JP7801181B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

Steering devices using the so-called steer-by-wire system, which separates the power transmission between the steering wheel and the steered wheels, are known. For example, the steer-by-wire system disclosed in Patent Document 1 includes a reaction force actuator and a steering actuator. The reaction force actuator generates a steering reaction force that is applied to the steering shaft. The steering actuator generates a steering force that steers the steered wheels.

The reaction force actuator and the steering actuator each have two redundant control calculation units and two redundant motor drive units. The control calculation units perform calculations related to motor drive control. The motor drive units generate torque based on the drive signal generated by their corresponding control calculation units.

The two control calculation units of the first and second systems of the reaction force actuator can communicate with each other and can operate in coordination based on the information exchanged between them. The two control calculation units of the first and second systems of the steering actuator can communicate with each other and can operate in coordination based on the information exchanged between them.

The control calculation unit of the first system of the reaction force actuator and the control calculation unit of the first system of the steering actuator are capable of communicating with each other. The control calculation unit of the second system of the reaction force actuator and the control calculation unit of the second system of the steering actuator are capable of communicating with each other. The two control calculation units of the first system and the two control calculation units of the second system share information exchanged between them via inter-system communication to generate torque in the motor drive unit.

Conventionally, there are electric power steering devices that assist steering wheel operation. The control device of the electric power steering device causes the assist motor to generate an assist force depending on the steering state of the steering wheel. For example, the control device disclosed in Patent Document 2 executes power latch control, which continues control until a predetermined time has elapsed since the ignition key was turned off. When the steering wheel is operated while power latch control is being executed, steering assistance is provided by the motor.

Furthermore, the control device for the electric power steering device described in Patent Document 3 stops the motor drive current when the vehicle switch is turned off, and then executes power latch control to continue temperature estimation calculations for the elements on the circuit board. The control device maintains power until a predetermined time has elapsed since the motor drive current was stopped, or until the temperature of the elements on the circuit board drops below a predetermined value.

Japanese Patent Application Laid-Open No. 2021-075182 JP 2009-248850 A Japanese Patent Application Laid-Open No. 2020-108327

It is being considered to have a steer-by-wire system with multiple systems, such as that described in Patent Document 1, execute power latch control, as described in Patent Document 2 or Patent Document 3. In this case, when the vehicle power is turned off by operating the ignition key or the like, each control calculation unit individually executes power latch control. If the vehicle power is turned on while power latch control is being executed, each control calculation unit determines whether the vehicle power is on, and restarts after that determination is confirmed.

However, if the vehicle power supply is turned on while power latch control is being executed, there is a risk that the timing at which each control calculation unit recognizes that the vehicle power supply is on will not coincide due to differences in wiring resistance, etc. This raises concerns that there will also be a discrepancy in the timing at which each control calculation unit restarts. As a result, the control calculation unit that restarts first may receive pre-initialization information calculated by other control calculation units that are still executing power latch control, which could result in the output of unintended calculation results or unintended state transitions.

In particular, when the vehicle power is turned on during power latch control, unlike when the vehicle power is turned on for the first time, each control and calculation unit operates until just before it recognizes that the vehicle power has been turned on. This increases the likelihood that each control and calculation unit will output an unintended calculation result or undergo an unintended state transition. Furthermore, in a steer-by-wire steering device in which power transmission between the steering wheel and the steered wheels is separated, the output of an unintended calculation result or state transition described above could cause the reaction force actuator and steering actuator to be inappropriately controlled, potentially causing discomfort to the driver.

A vehicle control device that can solve the above problem has multiple control circuits that start up when the vehicle power is turned on and execute control of the control target, and that execute power latch control, which maintains power for a set period of time when the vehicle power is turned off. If the vehicle power is turned on while executing power latch control after the vehicle power is turned off, the multiple control circuits wait until all of the control circuits, including the control circuit itself, recognize that the vehicle power is on before starting up.

With this configuration, if the vehicle power is turned on while power latch control is being executed after the vehicle power has been turned off, each control circuit waits until all control circuits, including the control circuit itself, recognize that the vehicle power has been turned on before starting up. Therefore, if the vehicle power is turned on while power latch control is being executed after the vehicle power has been turned off, even if the timing at which each control device recognizes that the vehicle power has been turned on differs, the timing at which each control circuit starts up can be synchronized.

In the above-mentioned vehicle control device, the multiple control circuits may set flag values according to the recognition result of whether the vehicle power supply is on. In this case, the multiple control circuits may determine whether all of the control circuits, including themselves, recognize that the vehicle power supply is on based on the flag value.

According to this configuration, each control circuit can easily determine whether all control circuits, including itself, have recognized that the vehicle power supply is on, based on the value of each flag.
In the above vehicle control device, the controlled object may include a reaction motor having two systems of winding groups and generating a steering reaction force to be applied to a steering wheel whose power transmission between the reaction motor and the steered wheels is separated, and a turning motor that generates a steering force for turning the steered wheels. In this case, the plurality of control circuits may include a first reaction control circuit that controls power supply to a first system of winding groups of the reaction motor, a second reaction control circuit that controls power supply to a second system of winding groups of the reaction motor, a first turning control circuit that controls power supply to the first system of winding groups of the turning motor, and a second turning control circuit that controls power supply to the second system of winding groups of the turning motor.

With this configuration, if the vehicle power supply is turned on while power latch control is being executed after the vehicle power supply has been turned off, even if the first reaction force control circuit and second reaction force control circuit, which control the power supply to the reaction force motor, and the first turning control circuit and second turning control circuit, which control the power supply to the turning motor, recognize that the vehicle power supply has been turned on at different times, the timing at which each control circuit begins activation can be synchronized. This allows for appropriate control of the drive of the reaction force motor and the turning motor.

In the above-described vehicle control device, the first reaction force control circuit and the second reaction force control circuit may perform a first mutual confirmation to mutually confirm whether they have recognized that the vehicle power supply is on. The first turning control circuit and the second turning control circuit may perform a second mutual confirmation to mutually confirm whether they have recognized that the vehicle power supply is on. The first reaction force control circuit and the first turning control circuit may perform a third mutual confirmation to mutually confirm whether the first mutual confirmation and the second mutual confirmation are successful, and if the first mutual confirmation and the second mutual confirmation are successful, it may be determined that all of the control circuits have recognized that the vehicle power supply is on. The second reaction force control circuit and the second turning control circuit may perform a fourth mutual confirmation to mutually confirm whether the first mutual confirmation and the second mutual confirmation are successful, and if the first mutual confirmation and the second mutual confirmation are successful, it may be determined that all of the control circuits have recognized that the vehicle power supply is on.

This configuration simplifies the signal path compared to a configuration in which the first reaction force control circuit and the second reaction force control circuit, as well as the first turning control circuit and the second turning control circuit, mutually confirm the recognition results of the vehicle power being turned on with all control circuits except for themselves. For example, there is no need to provide a communication line between the first reaction force control circuit and the second turning control circuit, or a communication line between the second reaction force control circuit and the first turning control circuit.

In the above-mentioned vehicle control device, the controlled object may include a reaction motor, which is a source of steering reaction force applied to a steering wheel whose power transmission between it and the steered wheels is separated, and a steering motor, which is a source of steering force that steers the steered wheels. In this case, the multiple control circuits may include a reaction control circuit that controls the reaction motor, and a steering control circuit that controls the steering motor. The reaction control circuit and the steering control circuit may confirm with each other whether they have recognized that the vehicle power supply is on.

With this configuration, if the vehicle power supply is turned on while power latch control is being executed after the vehicle power supply has been turned off, the reaction force control circuit and the steering control circuit can synchronize their start-up timing even if they recognize the vehicle power supply being on at different times. This allows for appropriate control of the drive of the reaction force motor and the steering motor.

In the above-described vehicle control device, the controlled object may include an assist motor that generates an assist force to assist steering wheel operation. The assist motor may also have a first winding group and a second winding group. In this case, the multiple control circuits may include a first assist control circuit that controls the power supply to the first winding group, and a second assist control circuit that controls the power supply to the second winding group. The first assist control circuit and the second assist control circuit may confirm with each other whether they have recognized that the vehicle power supply is on.

With this configuration, if the vehicle power is turned on while power latch control is being executed after the vehicle power is turned off, the first assist control circuit and the second assist control circuit wait until both the first assist control circuit and the second assist control circuit recognize that the vehicle power is on before starting their activation. Therefore, if the vehicle power is turned on while power latch control is being executed after the vehicle power is turned off, even if the first assist control circuit and the second assist control circuit recognize that the vehicle power is on at different times, the timing at which the first assist control circuit and the second assist control circuit start their activation can be synchronized. This allows for appropriate control of the drive of the assist motor.

In the above-mentioned vehicle control device, the control circuit may be configured to be able to communicate with an in-vehicle system that executes processing to transition the vehicle to a drivable state. In this case, if the vehicle power is turned on while power latch control is being executed after the vehicle power has been turned off, the control circuit may be configured to wait until all the control circuits, including the control circuit itself, recognize that the vehicle power has been turned on before allowing communication with the in-vehicle system.

With this configuration, each control circuit cannot communicate with the in-vehicle system unless all of the multiple control circuits recognize that the vehicle power is on. This prevents a control circuit that recognizes that the vehicle power is on from starting communication with the in-vehicle system before all of the control circuits recognize that the vehicle power is on.

In the above-described vehicle control device, the control circuit may be configured to be able to communicate with an in-vehicle system that executes processing to transition the vehicle to a drivable state, and may be configured to permit communication with the in-vehicle system when the vehicle power is turned on. The control circuit may also have information indicating whether the in-vehicle system is permitted to execute the processing. In this case, when the vehicle power is turned off while control of the control target is being executed, the control circuit may initialize the information by changing the content of the information from one that permits the in-vehicle system to execute the processing to one that requests the in-vehicle system to prohibit execution of the processing, and may transmit the information to the in-vehicle system when the vehicle power is turned on while power latch control is being executed after the vehicle power was turned off.

If the vehicle power is turned on while power latch control is being executed after the vehicle power is turned off, there is a risk that the control circuit that first recognized the vehicle power being on will begin communicating with the in-vehicle system before all control circuits recognize that the vehicle power is on. In this case, there is a concern that the control circuit that first recognized the vehicle power being on will send information to the in-vehicle system indicating whether or not to permit the in-vehicle system to execute processing to transition the vehicle to a drivable state. However, the content of the information sent to the in-vehicle system is changed to request that the in-vehicle system prohibit the execution of processing to transition the vehicle to a drivable state. This prevents the in-vehicle system from beginning processing to transition the vehicle to a drivable state before all control circuits recognize that the vehicle power is on.

In the above-described vehicle control device, the control circuit may be configured to communicate with an in-vehicle system that executes a process to transition the vehicle to a drivable state, and may be configured to permit communication with the in-vehicle system when the vehicle power is turned on. The control circuit may also have information indicating whether to permit the in-vehicle system to execute the process. In this case, if the vehicle power is turned off while the control circuit is executing control of the control target, the control circuit may be configured to retain the content of the information as the content at the time of execution of control of the control target, which is the content permitting the in-vehicle system to execute the process, and to transmit the information to the in-vehicle system when the vehicle power is turned on while executing power latch control after the vehicle power is turned off. In this case, the control circuit may also be configured to execute processing to request the in-vehicle system to ignore the information if the vehicle power is turned on while executing power latch control after the vehicle power is turned off and not all of the control circuits, including the control circuit itself, recognize that the vehicle power is on.

If the vehicle power is turned on while power latch control is being executed after the vehicle power has been turned off, there is a risk that the control circuit that first recognized the vehicle power being on may begin communicating with the in-vehicle system before all other control circuits have recognized that the vehicle power is on. In this case, there is a concern that the control circuit that first recognized the vehicle power being on may send information to the in-vehicle system indicating whether or not to allow the in-vehicle system to execute processing to transition the vehicle to a state in which it can be driven.

When power latch control is being executed, the information indicating whether the in-vehicle system is permitted to execute processing to transition the vehicle to a drivable state is maintained at the time of execution of the control of the controlled object, i.e., the information permitting the in-vehicle system to execute processing to transition the vehicle to a drivable state. As a result, there is a risk that the in-vehicle system will begin executing processing to transition the vehicle to a drivable state before all control circuits recognize that the vehicle power is on.

In this regard, with the above configuration, if the vehicle power is turned on during power latch control after the vehicle power is turned off, the control circuit that first recognized the vehicle power is turned on executes processing to request the in-vehicle system to ignore the destination information sent to it if all control circuits, including the control circuit itself, have not yet recognized that the vehicle power is on. This prevents the in-vehicle system from starting processing to transition the vehicle to a drivable state before all control circuits recognize that the vehicle power is on.

The vehicle control device of the present invention can synchronize the startup timing of each control circuit even if the vehicle power supply is turned on while power latch control is being executed.

1 is a configuration diagram of a steer-by-wire steering device in which a first embodiment of a vehicle control device is mounted; FIG. 2 is a block diagram of a reaction force control device and a steering control device according to the first embodiment. 4 is a time chart showing state transitions of each control circuit in the first embodiment; FIG. 2 is a configuration diagram of a second embodiment of a vehicle control device. 10 is a time chart showing a first comparative example of state transitions of each control circuit; 10 is a time chart showing a second comparative example of state transitions of each control circuit; 13 is a time chart showing a first mode of state transition of each control circuit in the third embodiment; 13 is a time chart showing a second mode of state transition of each control circuit in the third embodiment; 13 is a time chart showing a first mode of state transition of each control circuit in the fourth embodiment; 13 is a time chart showing a second mode of state transition of each control circuit in the fourth embodiment; 13 is a time chart showing a first mode of state transition of each control circuit in the fifth embodiment; 13 is a time chart showing a second mode of state transition of each control circuit in the fifth embodiment;

First Embodiment
A first embodiment in which the vehicle control device is embodied in a steer-by-wire type steering device will be described below.

As shown in Figure 1, the vehicle steering device 10 has a steering shaft 12 connected to a steering wheel 11. The steering device 10 also has a steered shaft 13 extending in the vehicle width direction (left-right direction in Figure 1). Steered wheels 15 are connected to both ends of the steered shaft 13 via tie rods 14. The linear movement of the steered shaft 13 changes the steering angle θw of the steered wheels 15. The steering shaft 12 and the steered shaft 13 constitute the vehicle's steering mechanism. Note that Figure 1 only shows the steered wheels 15 on one side.

The steering device 10 has a reaction motor 21 and a reduction mechanism 22. The reaction motor 21 is the source of a steering reaction force. The steering reaction force is a force that acts in the opposite direction to the direction of operation of the steering wheel 11 by the driver. The rotating shaft of the reaction motor 21 is connected to the steering shaft 12 via the reduction mechanism 22. The torque of the reaction motor 21 is applied to the steering shaft 12 as a steering reaction force. By applying the steering reaction force to the steering wheel 11, it is possible to give the driver an appropriate sense of response.

The reaction motor 21 is, for example, a three-phase brushless motor. The reaction motor 21 has a first winding group N11 and a second winding group N12. The first winding group N11 and the second winding group N12 are wound around a common stator (not shown). The electrical characteristics of the first winding group N11 and the second winding group N12 are equivalent.

The steering device 10 has a steering motor 31 and a reduction mechanism 32. The steering motor 31 is a source of steering force. The steering force refers to the power used to steer the steered wheels 15. The rotating shaft of the steering motor 31 is connected to a pinion shaft 33 via the reduction mechanism 32. The pinion teeth 33a of the pinion shaft 33 are engaged with the rack teeth 13a of the steering shaft 13. The torque of the steering motor 31 is applied to the steering shaft 13 via the pinion shaft 33 as a steering force. As the steering motor 31 rotates, the steering shaft 13 moves in the vehicle width direction.

The steering motor 31 is, for example, a three-phase brushless motor. The steering motor 31 has a first winding group N21 and a second winding group N22. The first winding group N21 and the second winding group N22 are wound around a common stator (not shown). The electrical characteristics of the first winding group N21 and the second winding group N22 are equivalent.

The steering device 10 has a reaction force control device 40. The reaction force control device 40 controls the drive of the reaction force motor 21, which is the object of control. The reaction force control device 40 executes reaction force control, causing the reaction force motor 21 to generate a steering reaction force corresponding to the steering torque Th. The reaction force control device 40 calculates a target steering reaction force based on the steering torque Th detected via a torque sensor 23. The torque sensor 23 is provided on the steering shaft 12. The reaction force control device 40 controls the power supply to the reaction force motor 21 so that the actual steering reaction force applied to the steering shaft 12 matches the target steering reaction force. The reaction force control device 40 independently controls the power supply to each of the two winding groups in the reaction force motor 21.

The reaction force control device 40 has a first circuit system 41 and a second circuit system 42. The first circuit system 41 controls the power supply to the first winding group N11 of the reaction force motor 21 in accordance with the steering torque Th detected by the torque sensor 23. The second circuit system 42 controls the power supply to the second winding group N12 of the reaction force motor 21 in accordance with the steering torque Th detected by the torque sensor 23.

The steering device 10 has a steering control device 50. The steering control device 50 controls the drive of the steering motor 31, which is the object of control. The steering control device 50 executes steering control by causing the steering motor 31 to generate a steering force for turning the steered wheels 15 according to the steering state. The steering control device 50 receives the steering angle θs detected via the steering angle sensor 24 and the stroke Xw of the steered shaft 13 detected via the stroke sensor 34. The stroke Xw is the amount of displacement of the steered shaft 13 relative to the neutral position, and is a state variable that reflects the steering angle θw. The steering angle sensor 24 is provided between the torque sensor 23 of the steering shaft 12 and the reduction mechanism 22. The stroke sensor 34 is provided near the steered shaft 13.

The steering control device 50 calculates the target steering angle of the steered wheels 15 based on the steering angle θs detected by the steering angle sensor 24. The target steering angle can be obtained, for example, by multiplying the detected steering angle θs by the steering angle ratio. The steering angle ratio is the ratio of the steering angle θw to the steering angle θs. The steering angle ratio is a value that is set in advance depending on product specifications, etc. The steering control device 50 calculates the steering angle θw based on the stroke Xw of the steered shaft 13 detected by the stroke sensor 34. The steering control device 50 controls the power supply to the steering motor 31 so that the steering angle θw calculated based on the stroke Xw matches the target steering angle. The steering control device 50 independently controls the power supply to each of the two winding groups in the steering motor 31.

The steering control device 50 has a first system circuit 51 and a second system circuit 52. The first system circuit 51 controls the power supply to the first system winding group N21 in the steering motor 31 based on the steering angle θs detected through the steering angle sensor 24 and the stroke Xw of the steering shaft 13 detected through the stroke sensor 34. The second system circuit 52 controls the power supply to the second system winding group N22 in the steering motor 31 based on the steering angle θs detected through the steering angle sensor 24 and the stroke Xw of the steering shaft 13 detected through the stroke sensor 34.

The reaction force control device 40 and the reaction force motor 21 may be integrally provided to form a so-called electromechanical integrated reaction force actuator. The steering control device 50 and the steering motor 31 may be integrally provided to form a so-called electromechanical integrated steering actuator.

<Power supply path>
Next, the power supply paths to the reaction force control device 40 and the steering control device 50 will be described.
The various on-board control devices including the reaction force control device 40 and the steering control device 50 are each supplied with power from a DC power supply 60 mounted on the vehicle. The DC power supply 60 is, for example, a battery. The various sensors including the torque sensor 23, the steering angle sensor 24, and the stroke sensor 34 are also each supplied with power from the DC power supply 60.

The first and second circuit systems 41 and 42 of the reaction force control device 40 and the first and second circuit systems 51 and 52 of the turning control device 50 are each connected to a DC power supply 60 via the vehicle's start switch SW. The start switch SW is, for example, an ignition switch or a power switch. The start switch SW is operated to start or stop a vehicle's driving source, such as an engine. When the start switch SW is turned on, power from the DC power supply 60 is supplied via the start switch SW to the first and second circuit systems 41 and 42 of the reaction force control device 40 and the first and second circuit systems 51 and 52 of the turning control device 50. Turning the start switch SW on turns on the vehicle power supply. Turning the start switch SW off turns off the vehicle power supply.

The first and second system circuits 41 and 42 of the reaction force control device 40, and the first and second system circuits 51 and 52 of the turning control device 50, are connected to a DC power supply 60 via power supply relays 61, 62, 63, and 64. When the power supply relays 61, 62, 63, and 64 are turned on, power from the DC power supply 60 is supplied to the first and second system circuits 41 and 42 of the reaction force control device 40, and the first and second system circuits 51 and 52 of the turning control device 50 via the power supply relays 61, 62, 63, and 64.

The first system circuit 41 of the reaction force control device 40 controls the on/off of the power supply relay 61. When the start switch SW is switched from on to off, the first system circuit 41 executes power latch control, which keeps the power supply relay 61 in the on state for a specified period of time. Therefore, the first system circuit 41 can continue to operate even after the start switch SW is turned off. The first system circuit 41 can cut off the power supply to itself by switching the power supply relay 61 from on to off after the specified period has elapsed.

The first system circuit 41 detects whether the start switch SW is on or off by, for example, monitoring the voltage across the start switch SW. The first system circuit 41 detects that the start switch SW has been turned on when the voltage across the start switch SW falls below a predetermined voltage threshold. The first system circuit 41 detects that the start switch SW has been turned off when the voltage across the start switch SW is equal to or greater than the predetermined voltage threshold.

The second system circuit 42 of the reaction force control device 40 controls the on/off of the power supply relay 62. Similar to the first system circuit 41, the second system circuit 42 performs power latch control. When the start switch SW is switched from on to off, the second system circuit 42 keeps the power supply relay 62 in the on state for a specified period of time.

The first system circuit 51 of the steering control device 50 controls the on/off of the power supply relay 63. Similar to the first system circuit 41 of the reaction force control device 40, the first system circuit 51 performs power latch control. When the start switch SW is switched from on to off, the first system circuit 51 keeps the power supply relay 63 in the on state for a specified period of time.

The second system circuit 52 of the steering control device 50 controls the on/off of the power supply relay 64. Similar to the first system circuit 41 of the reaction force control device 40, the second system circuit 52 performs power latch control. When the start switch SW is switched from on to off, the second system circuit 52 keeps the power supply relay 64 in the on state for a specified period of time.

Incidentally, among the components of the steering device 10, those that are required to continue operating even after the start switch SW is turned off, such as the torque sensor 23, steering angle sensor 24, and stroke sensor 34, are connected to the DC power supply 60 via at least one of the power supply relays 61, 62, 63, and 64. Therefore, even if the start switch SW is turned off, as long as at least one of the power supply relays 61, 62, 63, and 64 is turned on, power continues to be supplied to the components such as the torque sensor 23, steering angle sensor 24, and stroke sensor 34.

<Reaction force control device>
Next, the configuration of the reaction force control device will be described in detail.
2, the reaction force control device 40 has a first circuit system 41 and a second circuit system 42. The first circuit system 41 has a first reaction force control circuit 41A and a motor drive circuit 41B. The second circuit system 42 has a second reaction force control circuit 42A and a motor drive circuit 42B.

The first reaction force control circuit 41A is composed of processing circuits including: 1) one or more processors that operate according to a computer program (software); 2) one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that perform at least some of the various processes; and 3) a combination thereof. The processor includes a central processing unit (CPU). The processor also includes memory, such as random-access memory (RAM) and read-only memory (ROM). The memory stores program code or instructions that cause the CPU to perform processes. Memory, i.e., non-transitory computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

The first reaction force control circuit 41A calculates the target steering reaction force to be generated by the reaction force motor 21 based on the steering torque Th detected via the torque sensor 23, and calculates a first current command value for the first system winding group N11 according to the calculated target steering reaction force value. However, the first current command value is set to a value that is half (50%) of the amount of current (100%) required for the reaction force motor 21 to generate the target steering reaction force. The first reaction force control circuit 41A generates a drive signal (PWM signal) for the motor drive circuit 41B by performing current feedback control that causes the value of the actual current supplied to the first system winding group N11 to follow the first current command value.

The motor drive circuit 41B is a PWM inverter consisting of three legs connected in parallel, each corresponding to one of the three phases (U, V, W), with two series-connected switching elements such as field-effect transistors (FETs) serving as the basic unit. The motor drive circuit 41B converts DC power supplied from the DC power supply 60 into three-phase AC power by switching the switching elements of each phase based on the drive signal generated by the first reaction force control circuit 41A. The three-phase AC power generated by the motor drive circuit 41B is supplied to the first winding group N11 of the reaction force motor 21 via power supply paths for each phase, such as bus bars or cables. This causes the first winding group N11 to generate torque according to the first current command value.

The second reaction force control circuit 42A has basically the same configuration as the first reaction force control circuit 41A. The second reaction force control circuit 42A calculates a target steering reaction force to be generated by the reaction force motor 21 based on the steering torque Th detected via the torque sensor 23, and calculates a second current command value for the second system winding group N12 according to the calculated target steering reaction force value. However, the second current command value is set to half the amount of current required to generate the target steering reaction force in the reaction force motor 21. The second reaction force control circuit 42A generates a drive signal for the motor drive circuit 42B by performing current feedback control that causes the value of the actual current supplied to the second system winding group N12 to follow the second current command value.

The motor drive circuit 42B basically has the same configuration as the motor drive circuit 41B. Based on the drive signal generated by the second reaction force control circuit 42A, the motor drive circuit 42B converts the DC power supplied from the DC power supply 60 into three-phase AC power. The three-phase AC power generated by the motor drive circuit 42B is supplied to the second system winding group N12 of the reaction force motor 21 via power supply paths for each phase, such as bus bars or cables. This causes the second system winding group N12 to generate torque according to the second current command value. The reaction force motor 21 generates a torque that is the sum of the torque generated by the first system winding group N11 and the torque generated by the second system winding group N12.

Depending on the product specifications, there may be a master-slave relationship between the first circuit system 41 and the second circuit system 42 of the reaction force control device 40. In this case, for example, the first circuit system 41 may function as the master and the second circuit system 42 may function as the slave. Also, depending on the product specifications, the first circuit system 41 and the second circuit system 42 may have an equal relationship.

<Steering control device>
Next, the configuration of the steering control device 50 will be described in detail.
As shown in Fig. 2, the steering control device 50 has a first system circuit 51 and a second system circuit 52. The first system circuit 51 has a first steering control circuit 51A and a motor drive circuit 51B. The second system circuit 52 has a second steering control circuit 52A and a motor drive circuit 52B.

The first steering control circuit 51A has a configuration basically similar to that of the first reaction force control circuit 41A. The first steering control circuit 51A calculates the target steering angle of the steered wheels 15 based on the steering angle θs detected by the steering angle sensor 24. The steering control device 50 calculates the steering angle θw based on the stroke Xw of the steered shaft 13 detected by the stroke sensor 34. The first steering control circuit 51A calculates the target steering force to be generated in the steering motor 31 by performing angle feedback control to cause the steering angle θw calculated based on the stroke Xw to track the target steering angle, and calculates a third current command value for the first system winding group N21 of the steering motor 31 based on the value of this calculated target steering force. However, the third current command value is set to a value half (50%) of the amount of current required for the steering motor 31 to generate the target steering force. The first steering control circuit 51A generates a drive signal for the motor drive circuit 51B by performing current feedback control to cause the actual current value supplied to the first system winding group N21 to follow the third current command value.

Motor drive circuit 51B has basically the same configuration as motor drive circuit 41B. Based on the drive signal generated by first steering control circuit 51A, motor drive circuit 51B converts DC power supplied from DC power supply 60 into three-phase AC power. The three-phase AC power generated by motor drive circuit 42B is supplied to the first system winding group N21 of steering motor 31 via power supply paths for each phase, such as bus bars or cables. This causes the first system winding group N21 to generate torque according to the third current command value.

The second steering control circuit 52A has a configuration basically similar to that of the first reaction force control circuit 41A. The second steering control circuit 52A calculates the target steering angle of the steered wheels 15 based on the steering angle θs detected by the steering angle sensor 24. The steering control device 50 calculates the steering angle θw based on the stroke Xw of the steered shaft 13 detected by the stroke sensor 34. The second steering control circuit 52A calculates the target steering force to be generated in the steering motor 31 by performing angle feedback control to cause the steering angle θw calculated based on the stroke Xw to track the target steering angle, and calculates a fourth current command value for the second system winding group N22 of the steering motor 31 based on the value of this calculated target steering force. However, the fourth current command value is set to a value equal to half (50%) of the amount of current required for the steering motor 31 to generate the target steering force. The second steering control circuit 52A generates a drive signal for the motor drive circuit 52B by performing current feedback control to cause the actual current value supplied to the second system winding group N22 to follow the fourth current command value.

Motor drive circuit 52B has basically the same configuration as motor drive circuit 41B. Based on the drive signal generated by second steering control circuit 52A, motor drive circuit 51B converts DC power supplied from DC power supply 60 into three-phase AC power. The three-phase AC power generated by motor drive circuit 52B is supplied to second system winding group N22 of steering motor 31 via power supply paths for each phase, such as bus bars or cables. As a result, second system winding group N22 generates torque according to the fourth current command value. The steering motor 31 generates torque that is the sum of the torque generated by first system winding group N21 and the torque generated by second system winding group N22.

Depending on the product specifications, there may be a master-slave relationship between the first system circuit 51 and the second system circuit 52 of the steering control device 50. In this case, for example, the first system circuit 51 may function as the master and the second system circuit 52 may function as the slave. Also, depending on the product specifications, the first system circuit 51 and the second system circuit 52 may have an equal relationship.

<Communication path>
Next, the communication paths within the reaction force control device 40 and the steering control device 50, and the communication paths between the reaction force control device 40 and the steering control device 50 will be described.

As shown in FIG. 2, the first reaction force control circuit 41A and the second reaction force control circuit 42A exchange information with each other via communication line L1. The information includes abnormality information for the first reaction force control circuit 41A, the second reaction force control circuit 42A, or the motor drive circuits 41B and 42B. The information also includes the values of various flags. The first reaction force control circuit 41A and the second reaction force control circuit 42A cooperate to control the drive of the reaction force motor 21 based on the information exchanged between them.

The first steering control circuit 51A and the second steering control circuit 52A exchange information with each other via communication line L2. This information includes abnormality information for the first steering control circuit 51A, the second steering control circuit 52A, or the motor drive circuits 51B and 52B. The information also includes the values of various flags. The first steering control circuit 51A and the second steering control circuit 52A cooperate to control the drive of the steering motor 31 based on the information exchanged between them.

The first reaction force control circuit 41A and the first turning control circuit 51A exchange information with each other via communication line L3. This information includes abnormality information for the first reaction force control circuit 41A, the first turning control circuit 51A, and the motor drive circuits 41B, 51B. The information also includes the values of various flags. The first reaction force control circuit 41A and the first turning control circuit 51A operate in coordination based on the information exchanged between them.

The second reaction force control circuit 42A and the second turning control circuit 52A exchange information with each other via communication line L4. This information includes abnormality information for the second reaction force control circuit 42A, the second turning control circuit 52A, or the motor drive circuits 42B, 52B. The information also includes the values of various flags. The second reaction force control circuit 42A and the second turning control circuit 52A operate in coordination based on the information exchanged between them.

If an abnormality occurs in the first system circuits 41, 51, which are components of the first system, the reaction force motor 21 and the steering motor 31 are driven by the second system circuits 42, 52, which are components of the second system. If an abnormality occurs in the second system circuits 42, 52, which are components of the second system, the reaction force motor 21 and the steering motor 31 are driven by the first system circuits 41, 51, which are components of the first system.

For example, if an abnormality occurs in the first reaction force control circuit 41A, the first reaction force control circuit 41A stops operating, while the second reaction force control circuit 42A continues to control the power supply to the second system winding group N12 of the reaction force motor 21. In this case, the second reaction force control circuit 42A may supply half (50%) of the current required to generate the target steering reaction force in the reaction force motor 21 to the second system winding group N12. Alternatively, the second reaction force control circuit 42A may supply more than half of the current required to generate the target steering reaction force in the reaction force motor 21 to the second system winding group N12. This is determined according to product specifications, etc. Only the torque generated by the second system winding group N12 of the reaction force motor 21 is applied to the steering shaft 12 as steering reaction force.

Furthermore, when an abnormality occurs in the first reaction force control circuit 41A, the first steering control circuit 51A stops operating, while the second steering control circuit 52A continues to control the power supply to the second system winding group N22 of the steering motor 31. In this case, the second steering control circuit 52A may supply half (50%) of the current required to generate the target steering force in the steering motor 31 to the second system winding group N22. The second steering control circuit 52A may also supply more than half of the current required to generate the target steering force in the steering motor 31 to the second system winding group N22. This is determined according to product specifications, etc. Only the torque generated by the second system winding group N22 of the steering motor 31 is applied as steering force to the steering shaft 13.

Similarly, if an abnormality occurs in the second reaction force control circuit 42A, the second reaction force control circuit 42A stops operating, while the first reaction force control circuit 41A continues to control the power supply to the first system winding group N11 of the reaction force motor 21. Furthermore, if an abnormality occurs in the second reaction force control circuit 42A, the second turning control circuit 52A stops operating, while the first turning control circuit 51A continues to control the power supply to the first system winding group N21 of the turning motor 31.

Even if an abnormality occurs in the first steering control circuit 51A or the second steering control circuit 52A, the power supply control to the reaction force motor 21 and the steering motor 31 continues by the normal system, just as when an abnormality occurs in the first reaction force control circuit 41A or the second reaction force control circuit 42A. Even if an abnormality occurs in the motor drive circuits 41B, 51B of the first system or the motor drive circuits 42B, 52B of the second system, the power supply control to the reaction force motor 21 and the steering motor 31 continues by the normal system.

<State transition of control circuit>
Next, the state transitions of the control circuits (41A, 42A, 51A, 52A) will be described.
3, first reaction force control circuit 41A executes power latch control when start switch SW is turned off (time T1) while normal control is being executed. Similar to first reaction force control circuit 41A, second reaction force control circuit 42A, first turning control circuit 51A and second turning control circuit 52A also execute power latch control when start switch SW is turned off.

Normal control refers to control for generating a steering reaction force and a turning force according to the steering state of the steering wheel 11. In normal control, torque is generated in both the first winding group N11 and the second winding group N12 of the reaction force motor 21, and torque is generated in both the first winding group N21 and the second winding group N22 of the turning motor 31. When the start switch SW is turned off, the vehicle is stopped.

After the start switch SW is turned off, each control circuit (41A, 42A, 51A, 52A) executes power latch control and continues temperature estimation calculations for elements on the circuit board, for example. The elements are, for example, the switching elements of each motor drive circuit (41B, 42B, 51B, 52B). Each control circuit maintains power until a predetermined time has elapsed since the start switch SW was turned off, or until the temperature of the elements on the circuit board falls below a predetermined temperature. The predetermined temperature is a sufficiently low temperature.

When the temperature of elements on the board falls below a predetermined temperature, each control circuit stores the current temperature of the elements on the board in non-volatile memory and terminates power latch control. By executing this power latch control, each control circuit can accurately determine the initial temperature of elements on the board at the start of the next normal control run, and thereby appropriately execute overheat protection control. Overheat protection control is a control that prevents overheating of elements on the board by limiting reaction force control or steering control according to the amount of temperature rise based on the initial temperature of elements on the board.

Here, it is assumed that the start switch SW will be turned on again during the execution period of power latch control after it has been turned off. In this case, the following concerns arise. Namely, if the start switch SW is turned on during the execution period of power latch control, there is a risk that the timing at which the first reaction force control circuit 41A, the second reaction force control circuit 42A, the first turning control circuit 51A, and the second turning control circuit 52A recognize that the start switch SW has been turned on will not coincide due to differences in wiring resistance, etc.

An example of the timing at which each control circuit (41A, 42A, 51A, 52A) recognizes that the start switch SW is turned on is as follows.
That is, when the start switch SW is turned on during the execution period of power latch control (time T2), the first reaction force control circuit 41A recognizes that the start switch SW is on at time T3. The second reaction force control circuit 42A recognizes that the start switch SW is on at time T4. The first turning control circuit 51A recognizes that the start switch SW is on at time T5. The second turning control circuit 52A recognizes that the start switch SW is on at time T6. The temporal relationship between each time is as shown in the following relational expression (1).

T1<T2<T3<T5<T6<T4...(1)
However, for example, "T1<T2" indicates that time T2 is later than time T1.

As such, there is a concern that the timing at which each control circuit (41A, 42A, 51A, 52A) recognizes that the start switch SW is on will differ, resulting in different start-up times for each control circuit. Therefore, in this embodiment, each control circuit performs first mutual confirmation MC1, second mutual confirmation MC2, third mutual confirmation MC3, and fourth mutual confirmation to synchronize their start-up times.

<First Mutual Confirmation MC1>
The first reaction force control circuit 41A and the second reaction force control circuit 42A perform a first mutual confirmation MC1 in which they confirm with each other whether they have recognized that the vehicle power supply is on. Specifically, this is as follows.

The first reaction force control circuit 41A sets the value of flag F11 depending on the result of determining whether the start switch SW is on. When the first reaction force control circuit 41A determines that the start switch SW is off, it sets the value of flag F11 to "0." When the first reaction force control circuit 41A determines that the start switch SW is on during the execution period of power latch control (time T3), it sets the value of flag F11 to "1." The first reaction force control circuit 41A transmits the value of flag F11 to the second reaction force control circuit 42A.

The second reaction force control circuit 42A sets the value of flag F21 depending on the result of determining whether the start switch SW is on. When the second reaction force control circuit 42A determines that the start switch SW is off, it sets the value of flag F21 to "0." When the second reaction force control circuit 42A determines that the start switch SW is on during the execution period of power latch control (time T4), it sets the value of flag F21 to "1." The second reaction force control circuit 42A transmits the value of flag F21 to the first reaction force control circuit 41A.

The first reaction force control circuit 41A sets the value of flag F12 according to the values of flags F11 and F21. The value of flag F12 indicates whether both the first reaction force control circuit 41A and the second reaction force control circuit 42A recognize that the start switch SW is on, i.e., whether the first mutual confirmation MC1 was successful. The first reaction force control circuit 41A sets the value of flag F12 to "0" when the value of at least one of flags F11 and F21 is "0." This indicates that at least one of the first reaction force control circuit 41A and the second reaction force control circuit 42A does not recognize that the start switch SW is on. The first reaction force control circuit 41A sets the value of flag F12 to "1" when the value of flags F11 and F21 are both "1." This indicates that both the first reaction force control circuit 41A and the second reaction force control circuit 42A recognize that the start switch SW is on. The first reaction force control circuit 41A transmits the value of flag F12 to the first steering control circuit 51A.

The second reaction force control circuit 42A sets the value of flag F22 according to the values of flag F11 and flag F21. Like flag F12, the value of flag F22 indicates whether both the first reaction force control circuit 41A and the second reaction force control circuit 42A recognize that the start switch SW is on, i.e., whether the first mutual confirmation MC1 was successful. The second reaction force control circuit 42A sets the value of flag F22 to "0" when the value of at least one of flag F11 and flag F21 is "0." The second reaction force control circuit 42A sets the value of flag F22 to "1" when the values of flag F11 and flag F21 are both "1." The second reaction force control circuit 42A transmits the value of flag F22 to the second steering control circuit 52A.

<Second Mutual Confirmation MC2>
The first turning control circuit 51A and the second turning control circuit 52A perform a second mutual confirmation MC2 in which they confirm with each other whether they have recognized that the vehicle power supply is on. Specifically, this is as follows.

The first steering control circuit 51A sets the value of flag F31 depending on the result of determining whether the start switch SW is on. When the first steering control circuit 51A determines that the start switch SW is off, it sets the value of flag F31 to "0." When the first steering control circuit 51A determines that the start switch SW is on during the execution period of power latch control (time T5), it sets the value of flag F31 to "1." The first steering control circuit 51A transmits the value of flag F31 to the second steering control circuit 52A.

The second steering control circuit 52A sets the value of flag F41 depending on the result of determining whether the start switch SW is on. When the second steering control circuit 52A determines that the start switch SW is off, it sets the value of flag F41 to "0." When the second steering control circuit 52A determines that the start switch SW is on during the execution period of power latch control (time T6), it sets the value of flag F41 to "1." The second steering control circuit 52A transmits the value of flag F41 to the first steering control circuit 51A.

The first steering control circuit 51A sets the value of flag F32 according to the values of flags F31 and F41. The value of flag F32 indicates whether both the first steering control circuit 51A and the second steering control circuit 52A recognize that the start switch SW is on, i.e., whether the second mutual confirmation MC2 was successful. The first steering control circuit 51A sets the value of flag F32 to "0" when the value of at least one of flags F31 and F41 is "0." This indicates that at least one of the first steering control circuit 51A and the second steering control circuit 52A does not recognize that the start switch SW is on. The first steering control circuit 51A sets the value of flag F32 to "1" when the value of flags F31 and F41 are both "1." This indicates that both the first steering control circuit 51A and the second steering control circuit 52A recognize that the start switch SW is on. The first steering control circuit 51A transmits the value of flag F32 to the first reaction force control circuit 41A.

The second steering control circuit 52A sets the value of flag F42 according to the values of flags F31 and F41. Like flag F32, the value of flag F42 indicates whether both the first steering control circuit 51A and the second steering control circuit 52A recognize that the start switch SW is on, i.e., whether the second mutual confirmation MC2 was successful. The second steering control circuit 52A sets the value of flag F42 to "0" when the value of at least one of flags F31 and F41 is "0." The second steering control circuit 52A sets the value of flag F42 to "1" when the values of flags F31 and F41 are both "1." The second steering control circuit 52A transmits the value of flag F42 to the second reaction force control circuit 42A.

<Third Mutual Confirmation MC3>
The first reaction force control circuit 41A and the first turning control circuit 51A perform a third mutual confirmation MC3 in which they mutually confirm the success or failure of the first mutual confirmation MC1 and the second mutual confirmation MC2. When the first mutual confirmation MC1 and the second mutual confirmation MC2 are successful, the first reaction force control circuit 41A and the first turning control circuit 51A determine that all the control circuits (41A, 42A, 51A, 52A) have recognized that the vehicle power supply is on. Specifically, this is as follows.

The first reaction force control circuit 41A sets the value of flag F13 according to the values of flag F12 and flag F32. The value of flag F13 indicates whether the first reaction force control circuit 41A, the second reaction force control circuit 42A, the first turning control circuit 51A, and the second turning control circuit 52A all recognize that the start switch SW is on, i.e., whether the first mutual confirmation MC1 and the second mutual confirmation MC2 are successful or not. When the value of at least one of flag F12 and flag F32 is "0," the first reaction force control circuit 41A determines that at least one of first mutual confirmation MC1 and second mutual confirmation MC2 is not successful, and sets the value of flag F13 to "0." When the value of flag F12 and flag F32 are both "1," the first reaction force control circuit 41A determines that first mutual confirmation MC1 and second mutual confirmation MC2 are successful, and sets the value of flag F13 to "1." This triggers the activation of the first reaction force control circuit 41A (time T7).

The first steering control circuit 51A sets the value of flag F33 according to the values of flags F12 and F32. Like flag F13, the value of flag F33 indicates whether the first reaction force control circuit 41A, the second reaction force control circuit 42A, the first steering control circuit 51A, and the second steering control circuit 52A all recognize that the start switch SW is on, i.e., whether the first mutual confirmation MC1 and the second mutual confirmation MC2 have been met. When the value of at least one of flags F12 and F32 is "0," the first steering control circuit 51A determines that at least one of the first mutual confirmation MC1 and the second mutual confirmation MC2 has not been met, and sets the value of flag F33 to "0." When the value of flag F12 and the value of flag F32 are both "1," the first steering control circuit 51A determines that the first mutual confirmation MC1 and the second mutual confirmation MC2 are established, and sets the value of flag F33 to "1." This triggers the first steering control circuit 51A to start up (time T7).

<Fourth Mutual Confirmation MC4>
The second reaction force control circuit 42A and the second turning control circuit 52A perform a fourth mutual confirmation MC4 in which they mutually confirm the success or failure of the first mutual confirmation MC1 and the second mutual confirmation MC2. When the first mutual confirmation MC1 and the second mutual confirmation MC2 are successful, the second reaction force control circuit 42A and the second turning control circuit 52A determine that all the control circuits (41A, 42A, 51A, 52A) have recognized that the vehicle power supply is on. Specifically, this is as follows.

The second reaction force control circuit 42A sets the value of flag F23 according to the values of flags F22 and F42. Like flag F13, the value of flag F23 indicates whether the first reaction force control circuit 41A, the second reaction force control circuit 42A, the first turning control circuit 51A, and the second turning control circuit 52A all recognize that the start switch SW is on, i.e., whether the first mutual confirmation and the second mutual confirmation have been successful. When at least one of flags F22 and F42 has a value of "0," the second reaction force control circuit 42A determines that at least one of the first mutual confirmation and the second mutual confirmation has not been successful and sets the value of flag F23 to "0." When both flags F22 and F42 have a value of "1," the second reaction force control circuit 42A determines that the first mutual confirmation and the second mutual confirmation have been successful and sets the value of flag F23 to "1." This triggers the activation of the second reaction force control circuit 42A (time T7).

The second steering control circuit 52A sets the value of flag F43 according to the values of flag F22 and flag F42. Like flag F13, the value of flag F43 indicates whether the first reaction force control circuit 41A, the second reaction force control circuit 42A, the first steering control circuit 51A, and the second steering control circuit 52A all recognize that the start switch SW is on, i.e., whether the first mutual confirmation and the second mutual confirmation were successful. When the value of at least one of flag F22 and flag F42 is "0," the second steering control circuit 52A determines that at least one of the first mutual confirmation and the second mutual confirmation is not successful and sets the value of flag F43 to "0." When the value of flag F22 and flag F42 are both "1," the second steering control circuit 52A determines that the first mutual confirmation and the second mutual confirmation are successful and sets the value of flag F43 to "1." This triggers activation of the second steering control circuit 52A (time T7).

In this way, when the start switch SW is turned on during the power latch control period, each control circuit (41A, 42A, 51A, 52A) starts up at the same timing (time T7). Each control circuit executes an initial sequence upon startup and then transitions to a normal control execution state. The initial sequence refers to a series of processes required for the steering system to operate. The initial sequence processes include, for example, hardware checks, CPU initialization, and variable or flag initialization.

<Advantages of the First Embodiment>
Therefore, according to the first embodiment, the following effects can be obtained.
(1-1) When the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off, each control circuit (41A, 42A, 51A, 52A) waits until all control circuits, including itself, recognize that the vehicle power supply is on before starting activation. Therefore, when the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off, even if the timing at which each control device recognizes that the vehicle power supply is on differs, the timing at which each control circuit starts activation can be synchronized. Therefore, the drive of reaction force motor 21 and steering motor 31 can be appropriately controlled.

(1-2) Each control circuit (41A, 42A, 51A, 52A) sets the value of each flag (F11, F21, F31, F41) depending on whether it recognizes that the vehicle power supply is on. Each control circuit can easily determine whether all control circuits, including itself, recognize that the vehicle power supply is on based on the value of each flag.

(1-3) The first reaction force control circuit 41A and the second reaction force control circuit 42A perform a first mutual confirmation MC1 to mutually confirm whether they have recognized that the vehicle power supply is on by exchanging the values of flags F11 and F21. The first turning control circuit 51A and the second turning control circuit 52A perform a second mutual confirmation MC2 to mutually confirm whether they have recognized that the vehicle power supply is on by exchanging the values of flags F31 and F41. The first reaction force control circuit 41A and the first turning control circuit 51A perform a third mutual confirmation MC3 to mutually confirm the success or failure of the first mutual confirmation MC1 and the second mutual confirmation MC2 by exchanging the values of flags F12 and F32. When the first mutual confirmation MC1 and the second mutual confirmation MC2 are successful, the first reaction force control circuit 41A and the first turning control circuit 51A determine that all control circuits have recognized that the vehicle power supply is on. The second reaction force control circuit 42A and the second turning control circuit 52A mutually confirm the success or failure of the first mutual confirmation MC1 and the second mutual confirmation MC2 by exchanging the values of flags F22 and F42 (fourth mutual confirmation MC4). When the first mutual confirmation MC1 and the second mutual confirmation MC2 are successful, the second reaction force control circuit 42A and the second turning control circuit 52A determine that all control circuits have recognized that the vehicle power is on. This simplifies the signal path compared to when each control circuit (41A, 42A, 51A, 52A) mutually confirms the values of each flag (F11, F21, F31, F41). For example, there is no need to provide a communication line between the first reaction force control circuit 41A and the second turning control circuit 52A, or between the second reaction force control circuit 42A and the first turning control circuit 51A.

Second Embodiment
Next, a second embodiment in which the vehicle control device is embodied in an electric power steering device will be described. Note that the same reference numerals are used to designate the same components as those in the first embodiment, and detailed descriptions thereof will be omitted.

The electric power steering device mechanically connects the steering wheel 11 and steered wheels 15 shown in FIG. 1 above. That is, the steering shaft 12, pinion shaft 33, and steered shaft 13 function as a power transmission path between the steering wheel 11 and the steered wheels 15. When the steering wheel 11 is steered, the steered shaft 13 moves linearly, changing the steering angle θw of the steered wheels 15.

The electric power steering device has an assist motor and an assist control device. The assist motor is provided in the same position as the reaction motor 21 or steering motor 31 shown in Figure 1 above. The assist motor generates an assist force to assist the operation of the steering wheel 11. The assist force is torque in the same direction as the steering direction of the steering wheel 11. The assist control device controls the drive of the assist motor, which is the object of control.

As shown in FIG. 4, the assist motor 70 has a first winding group N31 and a second winding group N32.
The assist control device 80 has a first system circuit 81. The first system circuit 81 has a first assist control circuit 81A and a motor drive circuit 81B. The first assist control circuit 81A controls the power supply to the winding group N31 of the first system. The first assist control circuit 81A generates a drive signal for the motor drive circuit 81B based on the steering torque Th detected via the torque sensor 23.

The motor drive circuit 81B converts the DC power supplied from the DC power supply 60 into three-phase AC power based on the drive signal generated by the first assist control circuit 81A. The three-phase AC power generated by the motor drive circuit 81B is supplied to the first winding group N31 of the assist motor 70 via power supply paths for each phase, such as bus bars or cables.

The assist control device 80 has a second system circuit 82. The second system circuit 82 has a second assist control circuit 82A and a motor drive circuit 82B. The second assist control circuit 82A controls the power supply to the second system winding group N32. The second assist control circuit 82A generates a drive signal for the motor drive circuit 82B based on the steering torque Th detected via the torque sensor 23.

The motor drive circuit 82B converts the DC power supplied from the DC power supply 60 into three-phase AC power based on the drive signal generated by the second assist control circuit 82A. The three-phase AC power generated by the motor drive circuit 82B is supplied to the second winding group N32 of the assist motor 70 via power supply paths for each phase, such as bus bars or cables.

The first assist control circuit 81A and the second assist control circuit 82A exchange information with each other via a communication line. This information includes abnormality information for the first assist control circuit 81A, the second assist control circuit 82A, or the motor drive circuits 81B and 82B. The information also includes the values of various flags. The first assist control circuit 81A and the second assist control circuit 82A cooperate to control the drive of the assist motor 70 based on the information exchanged between them.

When the start switch SW is turned off while normal control is being executed, the first assist control circuit 81A executes power latch control, which self-maintains the power supply. The first assist control circuit 81A sets the value of flag F51 depending on the result of determining whether the start switch SW is on. When the first assist control circuit 81A determines that the start switch SW is off, it sets the value of flag F51 to "0." When the first assist control circuit 81A determines that the start switch SW is on while power latch control is being executed, it sets the value of flag F51 to "1." The first assist control circuit 81A transmits the value of flag F51 to the second assist control circuit 82A.

When the start switch SW is turned off while normal control is being executed, the second assist control circuit 82A executes power latch control, which self-maintains the power supply. The second assist control circuit 82A sets the value of flag F61 depending on the result of determining whether the start switch SW is on. When the second assist control circuit 82A determines that the start switch SW is off, it sets the value of flag F61 to "0." When the second assist control circuit 82A determines that the start switch SW is on while power latch control is being executed, it sets the value of flag F61 to "1." The second assist control circuit 82A transmits the value of flag F61 to the first assist control circuit 81A.

The first assist control circuit 81A and the second assist control circuit 82A determine whether both the first assist control circuit 81A and the second assist control circuit 82A recognize that the start switch SW is on, depending on the values of flags F51 and F61.

When the value of at least one of flag F51 and flag F61 is "0," the first assist control circuit 81A and the second assist control circuit 82A determine that at least one of the first assist control circuit 81A and the second assist control circuit 82A does not recognize that the start switch SW is on.

When the value of flag F51 and the value of flag F61 are both "1," the first assist control circuit 81A and the second assist control circuit 82A determine that they both recognize that the start switch SW is on. This triggers the first assist control circuit 81A and the second assist control circuit 82A to begin startup.

In this way, when the start switch SW is turned on during the power latch control period, the first assist control circuit 81A and the second assist control circuit 82A begin startup at the same time. The first assist control circuit 81A and the second assist control circuit 82A execute an initial sequence upon startup, and then transition to a state in which normal control is executed.

<Effects of the Second Embodiment>
Therefore, according to the second embodiment, the following effects can be obtained.
(2-1) If the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off, the first assist control circuit 81A and the second assist control circuit 82A wait until both the first assist control circuit 81A and the second assist control circuit 82A recognize that the vehicle power supply has been turned on before starting their activation. Therefore, if the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off, even if the first assist control circuit 81A and the second assist control circuit 82A recognize that the vehicle power supply has been turned on at different times, the timing at which the first assist control circuit 81A and the second assist control circuit 82A start their activation can be synchronized. This allows the drive of the assist motor 70 to be appropriately controlled.

(2-2) The first assist control circuit 81A and the second assist control circuit 82A set the values of flags F51 and F61 depending on the result of determining whether the vehicle power supply is on. By mutually checking the values of flags F51 and F61, the first assist control circuit 81A and the second assist control circuit 82A can easily determine whether both the first assist control circuit 81A and the second assist control circuit 82A have recognized that the vehicle power supply is on.

Third Embodiment
Next, a third embodiment will be described in which the vehicle control device is embodied in a steer-by-wire steering device. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 to 3. Therefore, the same members and configurations as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

As shown in FIG. 1, the reaction force control device 40 is interconnected with various on-board systems 72 via an on-board network 71. The on-board network 71 is, for example, a CAN (Controller Area Network). The reaction force control device 40 and the on-board systems 72 exchange information with each other via the on-board network 71. The turning control device 50 is also interconnected with various on-board systems 72 via the on-board network 71. The turning control device 50 and the on-board systems 72 exchange information with each other via the on-board network 71.

The in-vehicle system 72 includes, for example, a steering lock control device, a shift lock control device, a power train control device, and a meter control device.
The steering lock control device controls the operation of the steering lock mechanism. The steering lock mechanism is a mechanism for restricting the rotation of the steering wheel 11. When the start switch SW is turned on, the steering lock control device controls the operation of the steering lock mechanism so that the steering wheel 11 is unlocked. The process for unlocking the steering wheel 11 is a process for transitioning the vehicle to a state in which it can be driven. When the start switch SW is turned off, the steering lock control device controls the operation of the steering lock mechanism so that the steering wheel 11 is locked.

The shift lock control device controls the operation of the shift lock mechanism. The shift lock mechanism is a mechanism that restricts the operation of the shift lever with a locking member. The shift lock control device controls the operation of the shift lock mechanism so that the shift lever is unlocked when the start switch SW is turned on while the shift lever is in the parking position and the brake pedal is depressed. The process for unlocking the shift lever is a process for transitioning the vehicle to a state in which it can be driven. The shift lock control device controls the operation of the shift lock mechanism so that the shift lever is locked when the start switch SW is turned off while the shift lever is in the parking position.

The powertrain control device controls the vehicle's running. More specifically, the powertrain control device controls the vehicle's powertrain. The powertrain includes the vehicle's running drive source and power transmission mechanism. The running drive source includes, for example, an engine or a motor. The power transmission mechanism is a mechanism for transmitting power generated by the running drive source to the drive wheels. When the start switch SW is turned on, the powertrain control device begins executing a predetermined startup preparation. The startup preparation includes an initial check, which includes processes such as hardware checks, CPU initialization, and variable or flag initialization, as well as processes required to start the vehicle's powertrain. After the startup preparation is complete, the powertrain control device starts the powertrain. The process to start the powertrain is a process for transitioning the vehicle to a state where it can run.

The meter control device controls the illumination of indicator lights on the meter panel. Indicator lights include warning lights that alert the driver of an abnormality or malfunction related to vehicle operation, and warning lights that warn or caution the driver when the vehicle is not operating correctly. Warning lights illuminate in different colors depending on the warning level. For example, red indicates the occurrence of an abnormality that requires immediate inspection. Yellow indicates the occurrence of an abnormality that requires immediate inspection. Green indicates that the vehicle is normal.

The first reaction force control circuit 41A is capable of communicating via the in-vehicle network 71 when the power supply voltage supplied via the start switch SW is within a specified operating voltage range. The operating voltage range is the power supply voltage required to operate each control circuit (41A, 42A, 51A, 52A), including the first reaction force control circuit 41A. The operating voltage range is set, for example, based on ensuring communication reliability. When the power supply voltage supplied via the start switch SW reaches a value within the operating voltage range, the first reaction force control circuit 41A transmits various information to the in-vehicle system 72 via the in-vehicle network 71. The second reaction force control circuit 42A, first turning control circuit 51A, and second turning control circuit 52A perform the same processing as the first reaction force control circuit 41A.

The information includes, for example, the following five flags (A1) to (A5).
(A1) Communication permission flag F71
(A2) First unlock permission flag F72
(A3) Second unlock permission flag F73
(A4) Start permission flag F74
(A5) Meter notification flag F75
The communication permission flag F71 is information indicating whether communication through the in-vehicle network 71 is permitted. The first reaction force control circuit 41A sets the value of the communication permission flag F71 based on whether the voltage of the power source supplied via the start switch SW is within the operating voltage range. When the voltage of the power source supplied via the start switch SW is within the operating voltage range, the first reaction force control circuit 41A sets the value of the communication permission flag F71 to "permitted." Setting the value of the communication permission flag F71 to "permitted" indicates that communication through the in-vehicle network 71 of each control circuit (41A, 42A, 51A, 52A) is permitted. When the voltage of the power source supplied via the start switch SW is outside the operating voltage range, the first reaction force control circuit 41A sets the value of the communication permission flag F71 to "prohibited." Setting the value of the communication permission flag F71 to "prohibited" indicates that execution of communication through the in-vehicle network 71 of each of the control circuits (41A, 42A, 51A, 52A) is not permitted.

The first unlock permission flag F72 is information indicating whether the steering lock control device is permitted to unlock the steering wheel 11. The first reaction force control circuit 41A sets the value of the first unlock permission flag F72 based on whether the start switch SW is turned on. Here, the first reaction force control circuit 41A determines that the start switch SW is turned on when the voltage of the power supply supplied via the start switch SW is within the operating voltage range. Furthermore, the first reaction force control circuit 41A determines that the start switch SW is turned off when the voltage of the power supply supplied via the start switch SW is outside the operating voltage range.

When the start switch SW is turned on, the first reaction force control circuit 41A sets the value of the first unlock permission flag F72 to "allowed." Setting the value of the first unlock permission flag F72 to "allowed" indicates to the steering lock control device that unlocking the steering wheel 11 is permitted. When the start switch SW is turned off, the first reaction force control circuit 41A sets the value of the first unlock permission flag F72 to "prohibited." Setting the value of the first unlock permission flag F72 to "prohibited" indicates to the steering lock control device that unlocking the steering wheel 11 is not permitted.

The second unlock permission flag F73 is information indicating to the shift lock control device whether or not to permit unlocking of the shift lever. The first reaction force control circuit 41A sets the value of the second unlock permission flag F73 based on whether charging of the DC power supply 60 is complete. For example, the first reaction force control circuit 41A determines that charging of the DC power supply 60 is complete when the charge amount of the DC power supply 60 exceeds 90% of the full charge amount. The first reaction force control circuit 41A determines that charging of the DC power supply 60 is not complete when the charge amount of the DC power supply 60 is 90% or less of the full charge amount.

When charging of the DC power supply 60 is complete, the first reaction force control circuit 41A sets the value of the second unlock permission flag F73 to "permitted." Setting the value of the second unlock permission flag F73 to "permitted" indicates to the shift lock control device that unlocking the shift lever is permitted. When charging of the DC power supply 60 is not complete, the first reaction force control circuit 41A sets the value of the second unlock permission flag F73 to "prohibited." Setting the value of the second unlock permission flag F73 to "prohibited" indicates to the shift lock control device that unlocking the shift lever is not permitted.

The start permission flag F74 is information indicating whether starting of the powertrain is permitted. The first reaction force control circuit 41A sets the value of the start permission flag F74 based on whether execution of the initial sequence has been completed. When execution of the initial sequence has been completed, the first reaction force control circuit 41A sets the value of the start permission flag F74 to "Permitted." Setting the value of the start permission flag F74 to "Permitted" indicates to the powertrain control device that starting of the powertrain is permitted. When execution of the initial sequence has not been completed, the first reaction force control circuit 41A sets the value of the start permission flag F74 to "Prohibited." Setting the value of the start permission flag F74 to "Prohibited" indicates to the powertrain control device that starting of the powertrain is not permitted.

The meter notification flag F75 is information that indicates the operating status of the four control circuits (41A, 42A, 51A, 52A) as a steer-by-wire system. Each control circuit sets the value of the meter notification flag F75 to "normal" when all of the control circuits are operating normally. Each control circuit sets the value of the meter notification flag F75 to "abnormal" when at least one of the control circuits is not operating normally or is not started. Each control circuit also sets the value of the meter notification flag F75 to "abnormal" when, for example, a break in the power supply path to a specific one of the control circuits is detected.

Note that the second reaction force control circuit 42A, first steering control circuit 51A, and second steering control circuit 52A set the values of each flag (F71 to F75) in the same way as the first reaction force control circuit 41A.

However, it is not necessary for all four control circuits (41A, 42A, 51A, 52A) to have the function of setting the values of each permission flag (F72, F73, F74). In other words, the function of setting each permission flag may be shared and performed by each control circuit. In this case, there may be a control circuit that does not have the function of setting each permission flag.

For example, only the second reaction force control circuit 42A may have the function of setting the values of the first unlock permission flag F72 and the second unlock permission flag F73. Alternatively, the second reaction force control circuit 42A and the first turning control circuit 51A may have the function of setting the value of the start permission flag F74. Alternatively, only the first turning control circuit 51A may have the function of setting the value of the meter notification flag F75. The function of setting the value of the communication permission flag F71 may be provided by all of the control circuits.

Therefore, even if the start switch SW is turned on, the vehicle will not transition to a state in which it can run until the reaction force control device 40 and the steering control device 50 have completed execution of the initial sequence and are in a state in which normal control can be executed. In other words, unlocking the steering wheel 11 and shift lever, and starting the powertrain are not permitted until a state in which normal control can be executed is reached. This prevents the vehicle from transitioning to a state in which it can run while normal control cannot be executed by the reaction force control device 40 and the steering control device 50. Furthermore, the vehicle can start running in a state that is safer for the driver, i.e., in a state in which it can be steered in the direction intended by the driver.

<First Comparative Example of State Transition of Control Circuit>
Next, a first comparative example of the state transition of each control circuit (41A, 42A, 51A, 52A) will be described.

As shown in the time chart of FIG. 5, when the start switch SW is turned off while normal control is being performed (time T11), each control circuit performs power latch control.
When the start switch SW is turned off, the level of the power supply voltage supplied to each control circuit (41A, 42A, 51A, 52A) via the power supply path including the start switch SW switches from "Hi" to "Lo.""Hi" indicates that the power supply voltage is above the lower limit of the operating voltage range and below the upper limit of the operating voltage range. "Lo" indicates that the power supply voltage is below the lower limit of the operating voltage range. When the power supply voltage level switches from "Hi" to "Lo," the value of the communication permission flag F71 switches from "permitted" to "prohibited."

During power latch control, the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75 are maintained at the same values as during normal control immediately before the start switch SW is turned off. That is, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are all maintained at "permitted." The value of the meter notification flag F75 is maintained at "normal." The values of each flag (F72, F73, F74, F75) are reset, for example, when the start of each control circuit (41A, 42A, 51A, 52A) is confirmed, i.e., when all of the control circuits recognize that the start switch SW is turned on.

When the start switch SW is turned off, the steering lock control device switches the state of the steering wheel 11 from an unlocked state to a locked state via the steering lock mechanism.

When the start switch SW is turned off, the shift lock control device switches the state of the shift lever from unlocked to locked via the shift lock mechanism.

When the start switch SW is turned off, the powertrain control device switches the powertrain state from "READY-ON" to "READY-OFF." "READY-ON" is a state in which the powertrain is ready to start and can be started. "READY-OFF" is a state in which the powertrain is stopped.

When the start switch SW is turned off, the meter control device switches the indicator light on the meter panel that shows the status of the steer-by-wire system from a lit state, indicating normal operation of the steer-by-wire system, to an unlit state, indicating that the steer-by-wire system is stopped.

Here, it is assumed that the start switch SW will be turned on again during the execution period of power latch control after it has been turned off (time T12). In this case, due to differences in wiring resistance, etc., the timing at which each control circuit (41A, 42A, 51A, 52A) recognizes that the start switch SW has been turned on may not coincide. Furthermore, due to a break in the power supply path to a specific control circuit among the control circuits (41A, 42A, 51A, 52A), a situation may arise in which a specific control circuit is unable to recognize that the start switch SW has been turned on. The power supply path is a power supply path that includes the start switch SW.

If such an event occurs, the following concerns arise:
As an example, assume that a disconnection occurs in the power supply path to a specific control circuit during the period from when the start switch SW is turned off until the start switch SW is turned on again during power latch control (time T11 to time T12). The power supply path is a power supply path that includes the start switch SW. In this case, the power supply voltage is not supplied to the specific control circuit via the start switch SW. Therefore, the specific control circuit cannot recognize that the start switch SW is turned on. Furthermore, the specific control circuit does not start up.

Therefore, a situation cannot occur in which all four control circuits (41A, 42A, 51A, 52A) recognize that the start switch SW is on. Furthermore, each control circuit continues to execute power latch control without starting up. After a predetermined period of time has elapsed since the start switch SW was turned off, each control circuit stops executing power latch control and transitions to a sleep state (time T13). Sleep means that each control circuit temporarily stops operation and waits in a power-saving state. When transitioning to the sleep state, each control circuit transmits information indicating the transition to the sleep state to the in-vehicle system 72 via the in-vehicle network 71.

However, when the start switch SW is turned on while power latch control is being executed, power supply voltage is supplied to three of the four control circuits (41A, 42A, 51A, 52A) other than the specific control circuit via a power supply path that includes the start switch SW. When the power supply voltage supplied in response to the start switch SW being turned on reaches a value within the operating voltage range, the three control circuits other than the specific control circuit set the value of the communication permission flag F71 to "permitted."

In addition, during power latch control, the three control circuits other than the specific control circuit maintain the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75 at the same values as during normal control immediately before the start switch SW was turned off. In other words, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are all set to "permitted." The value of the meter notification flag F75 is set to "normal."

For this reason, when the value of the communication permission flag F71 switches from "prohibited" to "permitted" during power latch control, the three control circuits other than the specific control circuit transmit the values of each flag (F72, F73, F74, F75) to the in-vehicle system 72 via the in-vehicle network 71. This enables the steering lock control device to execute processing to unlock the steering wheel 11. The shift lock control device to execute processing to unlock the shift lever. The powertrain control device to execute processing to start the powertrain.

As a result, even though the four control circuits (41A, 42A, 51A, 52A) are in a state where they cannot be activated as a steer-by-wire system, the vehicle transitions to a state where it can run. Specifically, this is as follows:

The steering lock control device switches the state of the steering wheel 11 from a locked state to an unlocked state via the steering lock mechanism based on the value of the first unlock permission flag F72, which is set to "permitted."

The shift lock control device switches the state of the shift lever from locked to unlocked via the shift lock mechanism based on the value of the second unlock permission flag F73, which is set to "permitted."

When the start switch is turned on, the powertrain control device begins executing the specified startup preparations. Startup preparations include processes such as initial checks required to start the powertrain. When startup preparations are complete, the powertrain state switches from "READY-OFF" to "READY-ON." In other words, the powertrain transitions to a state where it can be started. The powertrain control device starts the powertrain based on the value of the start permission flag F74, which is set to "permitted."

Based on the value of the meter notification flag F75 being set to "normal," the meter control device switches the indicator light on the meter panel that shows the status of the steer-by-wire system from an off state, indicating that the steer-by-wire system is stopped, to an on state, indicating that the steer-by-wire system is operating normally.

In this way, with the four control circuits not activated as a steer-by-wire system, the steering wheel 11 and shift lever are unlocked and the powertrain is allowed to start, transitioning the vehicle to a state where it can be driven.

The meter control device switches the illumination state of the indicator light when it receives information via the in-vehicle network 71 indicating that each control circuit will transition to a sleep state, or when communication with each control circuit is interrupted. For example, the meter control device switches the illumination state of the indicator light from a lit state indicating normal operation of the steer-by-wire system to, for example, a red lit state. The driver can visually recognize an abnormality in the steer-by-wire system after each control circuit has completed execution of power latch control.

Even if the four control circuits (41A, 42A, 51A, 52A) simply do not recognize the start switch SW being turned on at the same time, the same phenomenon occurs as when a break occurs in the power supply path to a specific control circuit, including the start switch SW. That is, the control circuit that first recognizes that the start switch SW is turned on transmits the values of each flag (F72, F73, F74, F75) to the in-vehicle system 72 via the in-vehicle network 71. As a result, there is a risk that the vehicle will transition to a state where it can run even though the four control circuits have not yet activated as a steer-by-wire system.

Even when the function of setting the values of each permission flag (F72, F73, F74) is shared among the various control circuits, the same phenomenon will occur as if a break occurred in the power supply path to a specific control circuit, including the start switch SW.

For example, if only the second reaction force control circuit 42A has the function of setting the values of the first unlock permission flag F72 and the second unlock permission flag F73, it is expected that the second reaction force control circuit 42A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A will transmit the values of the first unlock permission flag F72 and the second unlock permission flag F73 to the in-vehicle system 72 via the in-vehicle network 71. As a result, there is a risk that the steering wheel 11 and the shift lever will be unlocked even if the four control circuits are not activated as a steer-by-wire system. Incidentally, a similar event can occur when a disconnection occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A; this power supply path is the power supply path that includes the start switch SW.

Furthermore, for example, if the second reaction force control circuit 42A and the first steering control circuit 51A have the function of setting the value of the start permission flag F74, it is possible that the second reaction force control circuit 42A or the first steering control circuit 51A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A or the first steering control circuit 51A will transmit the value of the start permission flag F74 to the on-board system 72 via the on-board network 71. As a result, there is a risk that the vehicle's powertrain will start even if the four control circuits are not activated as a steer-by-wire system. Incidentally, a similar event occurs when a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A or the first steering control circuit 51A. The power supply path is a power supply path that includes the start switch SW.

<Second Comparative Example of State Transition of Control Circuit>
Next, a second comparative example of the state transition of each control circuit (41A, 42A, 51A, 52A) will be described.

As shown in the time chart in Figure 6, during normal control immediately before the start switch SW is turned off, a situation may occur in which a specific control circuit is unable to recognize that the start switch SW is on due to a break in the power supply path to that control circuit. The power supply path is the power supply path that includes the start switch SW. Even in this case, when the start switch SW is turned on again during the execution of power latch control after the start switch SW is turned off, an event similar to that in the first comparative example shown in Figure 5 occurs.

As a result, there is a concern that the vehicle may transition to a state in which it is capable of running even when the four control circuits are not activated as a steer-by-wire system. Furthermore, if the function of setting the values of each permission flag (F72, F73, F74) is shared among the control circuits, the following concerns may arise, for example. That is, even when each control circuit is not activated as a steer-by-wire system, the steering wheel 11 and shift lever may be unlocked or the powertrain may be started.

However, when a break in the power supply path to a specific control circuit is detected during normal control immediately before the start switch SW is turned off, each control circuit sets the value of the meter notification flag F75 to "abnormal." Based on the value of the meter notification flag F75 being set to "abnormal," the meter control device switches the illumination state of the indicator light, for example, to a yellow illumination state.

While power latch control is being executed after the start switch SW is turned off, the value of the meter notification flag F75 remains set to "abnormal." Therefore, if the start switch SW is turned on again while power latch control is being executed, and the value of the communication permission flag F71 is set to "permitted," the meter control device will switch the indicator light's illumination state to yellow based on the value of the meter notification flag F75, which is set to "abnormal."

During the period when the start switch SW is turned off, the meter control device changes the indicator lamp from a lit state to an unlit state.
It is not desirable for the vehicle to transition to a state in which it can travel, or for processing to transition the vehicle to a state in which it can travel, to be executed even though the control circuits are not activated as a steer-by-wire system, as in the first comparative example shown in Figure 5 and the second comparative example shown in Figure 6. This is because the reaction force control and steering control according to the steering state of the steering wheel 11 are not executed, and therefore the traveling direction of the vehicle cannot be changed to the direction intended by the driver.

Therefore, in this embodiment, the reaction force control device 40 and the steering control device 50 have the following configurations.
<Conditions for communication permission>
Each control circuit (41A, 42A, 51A, 52A) sets the value of the communication permission flag F71 to "permitted" when all of the following five conditions B1 to B5 are met. Conditions B1 to B5 constitute communication permission conditions. The communication permission conditions are conditions for each control circuit to determine whether or not it is permissible to permit communication through the in-vehicle network 71.

B1. The value of the communication permission flag F71 is set to "prohibited."
B2. The value of the vehicle power on flag F76 is set to "on."
B3. The power supply voltage is above the lower limit of the operating voltage range.

B4. The power supply voltage is below the upper limit of the operating voltage range.
B5. The conditions B1 to B4 remain true for a set period of time or longer.
The vehicle power on flag F76 is information indicating whether all of the control circuits have recognized that the start switch SW is on. The control circuits mutually confirm whether they have recognized that the start switch SW is on, i.e., that the vehicle power supply is on, through the first mutual confirmation MC1, second mutual confirmation MC2, third mutual confirmation MC3, and fourth mutual confirmation MC4 shown in FIG. 3 . Each control circuit sets the value of the vehicle power on flag F76 to "off" when it determines that even one of the control circuits has not recognized that the start switch SW is on. Each control circuit sets the value of the vehicle power on flag F76 to "on" when it determines that all of the control circuits have recognized that the start switch SW is on.

Conditions B3 and B4 are conditions for determining whether the power supply voltage recognized by each control device is within the operating voltage range.
Condition B5 is set to prevent the value of communication permission flag F71 from being erroneously set to "permitted" when conditions B1 to B4 are instantaneously met, for example.

Therefore, when each control circuit determines that all four control circuits, including itself, recognize that the start switch SW is on, it is able to communicate via the in-vehicle network 71.

<First mode of state transition of control circuit>
Next, a first mode of state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.

As an example, consider the case where a break occurs in the power supply path to a specific control circuit during the period from when the start switch SW is turned off until the start switch SW is turned on again while power latch control is being executed. The power supply path is a power supply path that includes the start switch SW. Therefore, the power supply voltage is not supplied to the specific control circuit via the start switch SW. Therefore, the specific control circuit cannot recognize that the start switch SW is on. Furthermore, the specific control circuit does not start up.

As shown in the time chart in Figure 7, each control circuit executes power latch control when the start switch SW is turned off (time T11) while normal control is being executed. When the start switch SW is turned off, the power supply voltage level switches from "Hi" to "Lo." Therefore, when the start switch SW is turned off, each control circuit switches the value of the vehicle power on flag F76 from "On" to "Off." Additionally, each control circuit switches the value of the communication permission flag F71 from "Permitted" to "Prohibited."

During power latch control, the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75 are maintained at the same values as during normal control immediately before the start switch SW is turned off. That is, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are all maintained at "permitted." The value of the meter notification flag F75 is maintained at "normal."

When the start switch SW is turned on while power latch control is being executed (time T12), power supply voltage is supplied to three of the four control circuits (41A, 42A, 51A, 52A) other than a specific control circuit via a power supply path that includes the start switch SW. However, because the power supply via the start switch SW is cut off to the specific control circuit, it is unable to recognize that the start switch SW is on. For this reason, a situation cannot occur in which all four control circuits (41A, 42A, 51A, 52A) recognize that the start switch SW is on.

Therefore, while power latch control is being executed, each control circuit maintains the value of the vehicle power on flag F76 at "off" even if the power supply voltage level actually switches from "low" to "high" when the start switch SW is turned on. Furthermore, each control circuit maintains the value of the communication permission flag F71 at "prohibited" because conditions B2 and B5 of the communication start determination conditions are not met.

Since communication through the in-vehicle network 71 is not permitted, the three control circuits other than the specific control circuit will not transmit the values of each flag (F72, F73, F74, F75) to the in-vehicle system 72 via the in-vehicle network 71.

As a result, the steering lock control device will not begin executing the process to unlock the steering wheel 11. The steering lock control device will maintain the steering wheel 11 in a locked state. Furthermore, the shift lock control device will not begin executing the process to unlock the shift lever. The shift lock control device will maintain the shift lever in a locked state. Furthermore, the powertrain control device will not begin executing the process to start the powertrain. The powertrain control device will maintain the powertrain in a "READY-OFF" state, i.e., a state in which the powertrain operation is stopped.

As a result, even if the four control circuits (41A, 42A, 51A, 52A) are in a state where they cannot be activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

When the start switch SW is turned on, the meter control device switches the indicator light from off to, for example, red. This is because communication with each control circuit is not possible even though the start switch SW is turned on. The driver can immediately visually recognize an abnormality in the steer-by-wire system without waiting for each control circuit to complete power latch control.

The same applies if the four control circuits (41A, 42A, 51A, 52A) simply do not recognize the start switch SW as being on at the same time. That is, the control circuit that first recognizes the start switch SW as being on will not transmit the values of each flag (F72, F73, F74, F75) to the in-vehicle system 72 via the in-vehicle network 71. This is because communication via the in-vehicle network 71 is not permitted until all four control circuits recognize that the start switch SW is on. For this reason, even if the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

The same applies to the case where the function of setting the values of the permission flags (F72, F73, F74) is shared and executed by the respective control circuits.
For example, if only the second reaction force control circuit 42A has the function of setting the values of the first unlock permission flag F72 and the second unlock permission flag F73, it is assumed that the second reaction force control circuit 42A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A will not transmit the values of the first unlock permission flag F72 and the second unlock permission flag F73 to the in-vehicle system 72 via the in-vehicle network 71. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the steering wheel 11 and the shift lever will not be unlocked. The same applies when a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A. The power supply path is a power supply path that includes the start switch SW.

Furthermore, for example, if the second reaction force control circuit 42A and the first steering control circuit 51A have the function of setting the value of the start permission flag F74, it is assumed that the second reaction force control circuit 42A or the first steering control circuit 51A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A or the first steering control circuit 51A will not transmit the value of the start permission flag F74 to the on-board system 72 via the on-board network 71. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the vehicle's powertrain will not start. Incidentally, the same applies if a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A or the first steering control circuit 51A. The power supply path is a power supply path that includes the start switch SW.

<Second Aspect of State Transition of Control Circuit>
Next, a second aspect of the state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.

As shown in the time chart in Figure 8, during normal control immediately before the start switch SW is turned off, a situation may occur in which a specific control circuit is unable to recognize that the start switch SW is on due to a break in the power supply path to that control circuit. The power supply path is the power supply path that includes the start switch SW. Even in this case, when the start switch SW is turned on again during the execution of power latch control after the start switch SW is turned off, each control circuit performs processing similar to the first mode shown in Figure 7.

As a result, even if the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven. The same is true when the function of setting the values of each permission flag (F72, F73, F74) is shared among the control circuits. In other words, even if the control circuits are not activated as a steer-by-wire system, the steering wheel 11 and shift lever will not be unlocked and the powertrain will not be started.

<Effects of the Third Embodiment>
Therefore, according to the third embodiment, the following effects can be obtained.
(3-1) When the start switch SW is turned on, the four control circuits (41A, 42A, 51A, 52A) wait until all control circuits, including themselves, recognize that the start switch SW is turned on before starting up. Furthermore, when the start switch SW is turned on, communication through the in-vehicle network 71 is not permitted until all four control circuits recognize that the start switch SW is turned on. Therefore, if there is a control circuit that does not recognize that the start switch SW is turned on, the other control circuits that recognize that the start switch SW is turned on cannot transmit the values of the flags (F72, F73, F74, F75) to the in-vehicle system 72. This makes it possible to prevent the vehicle from transitioning to a state where it can run, or to prevent processing for transitioning the vehicle to a state where it can run, from being executed even though the control circuits have not yet started up as a steer-by-wire system.

(3-2) When the start switch SW is turned on but communication with each control circuit is not possible, the meter control device switches the indicator light from off to red. The red light indicates an abnormality in the steer-by-wire system. This allows the driver to immediately recognize an abnormality in the steer-by-wire system visually, without waiting for each control circuit to complete power latch control.

<Fourth embodiment>
Next, a fourth embodiment will be described in which the vehicle control device is embodied in a steer-by-wire steering device. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 to 3. Therefore, the same members and configurations as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

This embodiment differs from the third embodiment in the content of the processing executed by each control circuit (41A, 42A, 51A, 52A) when the start switch SW is turned off.
When the following three conditions C1 to C3 are all satisfied, each control circuit initializes the value of a flag to be transmitted to the in-vehicle system 72. The flags transmitted to the in-vehicle system 72 include a first unlock permission flag F72, a second unlock permission flag F73, a start permission flag F74, and a meter notification flag F75.

C1. The value of the control stop flag F77 is set to "stop."
C2. The value of the vehicle power off flag F78 is set to "off."
C3. The value of the communication permission flag F71 is set to "prohibited."

The control stop flag F77 is information indicating whether each control circuit has stopped the execution of reaction force control or steering control. When each control circuit has not stopped the execution of reaction force control or steering control, it sets the value of the control stop flag F77 to "not stopped." When each control circuit has stopped the execution of reaction force control or steering control, it sets the value of the control stop flag F77 to "stopped."

The vehicle power off flag F78 is information indicating whether all of the control circuits have recognized that the start switch SW is off. Each control circuit confirms with each other whether they have recognized that the start switch SW is off, i.e., that the vehicle power is off, through the first mutual confirmation MC1, second mutual confirmation MC2, third mutual confirmation MC3, and fourth mutual confirmation MC4 shown in Figure 3 above. Each control circuit sets the value of the vehicle power off flag F78 to "on" when it determines that even one of the control circuits has not recognized that the start switch SW is off. Each control circuit sets the value of the vehicle power off flag F78 to "off" when it determines that all of the control circuits have recognized that the start switch SW is off.

The communication permission flag F71 is information indicating whether communication through the in-vehicle network 71 is permitted. When all five conditions B1 to B5 are met, each control circuit sets the value of the communication permission flag F71 to "permitted." When the start switch SW is turned off, each control circuit sets the value of the communication permission flag F71 to "prohibited."

As part of the initialization process, each control circuit sets the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 to "prohibited." Also, as part of the initialization process, each control circuit switches the value of the meter notification flag F75 to a value that corresponds to the current state of the steer-by-wire system.

<First mode of state transition of control circuit>
Next, a first mode of state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.

As an example, consider the case where a break occurs in the power supply path to a specific control circuit during the period from when the start switch SW is turned off until the start switch SW is turned on again while power latch control is being executed. The power supply path is a power supply path that includes the start switch SW. Therefore, the power supply voltage is not supplied to the specific control circuit via the start switch SW. Therefore, the specific control circuit cannot recognize that the start switch SW is on. Furthermore, the specific control circuit does not start up.

As shown in the time chart of Figure 9, when the start switch SW is turned off while normal control is being performed, each control circuit executes power latch control (time T11). When the start switch SW is turned off, the power supply voltage level switches from "Hi" to "Lo." As a result, each control circuit stops the execution of reaction force control or steering control and changes the value of the control stop flag F77 from "non-stop" to "stop." Each control circuit also changes the value of the vehicle power off flag F78 from "on" to "off." Each control circuit also changes the value of the communication permission flag F71 from "permitted" to "prohibited."

When all three of the above conditions C1 to C3 are met, each control circuit initializes the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75. That is, each control circuit switches the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 from "permitted" to "prohibited." Each control circuit also switches the value of the meter notification flag F75 to a value corresponding to the current state of the steer-by-wire system. In this case, because a break has occurred in the power supply path to a specific control circuit, the value of the meter notification flag F75 is set to "abnormal." Incidentally, the value of the meter notification flag F75 may also be set to a more specific value, such as "yellow illumination request," instead of "abnormal."

During the execution period of power latch control after the start switch SW is turned off, when the start switch SW is turned on again (time T12), power supply voltage is not supplied to the specific control circuit via the power supply path that includes the start switch SW. As a result, the specific control circuit is unable to recognize that the start switch SW is on. Furthermore, the specific control circuit is not activated.

However, the three control circuits other than the specific control circuit are supplied with power supply voltage via a power supply path that includes the start switch SW. When the power supply voltage supplied in response to the start switch SW being turned on reaches a value within the operating voltage range, the three control circuits other than the specific control circuit set the value of the communication permission flag F71 to "permitted." This allows the three control circuits other than the specific control circuit to communicate via the in-vehicle network 71.

When the value of the communication permission flag F71 switches from "prohibited" to "permitted," the three control circuits other than the specific control circuit transmit the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75 to the in-vehicle system 72 via the in-vehicle network 71.

However, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are set to "prohibited" by initialization.
Therefore, the steering lock control device does not start executing a process to unlock the steering wheel 11. The steering lock control device maintains the state of the steering wheel 11 in a locked state. Furthermore, the shift lock control device does not start executing a process to unlock the shift lever. The shift lock control device maintains the state of the shift lever in a locked state. Furthermore, the powertrain control device does not start executing a process to start the powertrain. The powertrain control device maintains the state of the powertrain in a "READY-OFF" state, i.e., a state in which the operation of the powertrain is stopped.

As a result, even if the four control circuits (41A, 42A, 51A, 52A) are in a state where they cannot be activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

When the value of the meter notification flag F75 is set to "abnormal," the meter control device switches the indicator light from off to yellow. The driver can immediately visually recognize an abnormality in the steer-by-wire system without waiting for the completion of power latch control by each control circuit.

The same applies if the four control circuits (41A, 42A, 51A, 52A) simply do not recognize the start switch SW being turned on at the same time. That is, the control circuit that first recognizes the start switch SW being turned on may transmit the values of the first unlock permission flag F72, second unlock permission flag F73, start permission flag F74, and meter notification flag F75 to the in-vehicle system 72 via the in-vehicle network 71. However, the values of the first unlock permission flag F72, second unlock permission flag F73, and start permission flag F74 are set to "prohibited" by initialization. Therefore, even though the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

The same applies to the case where the function of setting the values of the permission flags (F72, F73, F74) is shared and executed by the respective control circuits.
For example, if only the second reaction force control circuit 42A has the function of setting the first unlock permission flag F72 and the second unlock permission flag F73, it is possible that the second reaction force control circuit 42A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A may transmit the values of the first unlock permission flag F72 and the second unlock permission flag F73 to the in-vehicle system 72 via the in-vehicle network 71. However, the values of the first unlock permission flag F72 and the second unlock permission flag F73 are set to "prohibited" by initialization. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the steering wheel 11 and the shift lever will not be unlocked. The same applies when a power supply path to a specific control circuit other than the second reaction force control circuit 42A is broken. The power supply path includes the start switch SW.

Furthermore, for example, if the second reaction force control circuit 42A and the first steering control circuit 51A have the function of setting the value of the start permission flag F74, it is possible that the second reaction force control circuit 42A or the first steering control circuit 51A will recognize that the start switch SW is on before the other three control circuits. In this case, the second reaction force control circuit 42A or the first steering control circuit 51A may transmit the value of the start permission flag F74 to the on-board system 72 via the on-board network 71. However, the value of the start permission flag F74 is set to "prohibited" by initialization. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the vehicle's powertrain will not start. The same applies if a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A or the first steering control circuit 51A. The power supply path includes the start switch SW.

<Second Aspect of State Transition of Control Circuit>
Next, a second aspect of the state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.

As shown in the time chart in Figure 10, during normal control immediately before the start switch SW is turned off, it is possible that the power supply to a specific control circuit may be cut off due to a break in the power supply path to that control circuit. The power supply path is the one that includes the start switch SW. If the start switch SW is turned off in this state, and all three conditions C1 to C3 are met, each control circuit initializes the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75.

That is, each control circuit switches the values of the first unlock permission flag F72, second unlock permission flag F73, and start permission flag F74 from "permitted" to "prohibited." Each control circuit also switches the value of the meter notification flag F75 to a value that corresponds to the current state of the steer-by-wire system. In this case, because a break has occurred in the power supply path to a specific control circuit, the value of the meter notification flag F75 is set to "abnormal."

If the start switch SW is turned on again during the execution period of power latch control after the start switch SW is turned off, each control circuit executes processing similar to the first mode shown in Figure 9. That is, when the value of the communication permission flag F71 switches from "prohibited" to "permitted," the three control circuits other than the specific control circuit transmit the values of the first unlock permission flag F72, second unlock permission flag F73, start permission flag F74, and meter notification flag F75 to the in-vehicle system 72 via the in-vehicle network 71.

However, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are set to "prohibited" by initialization.
Therefore, even if the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state in which it is capable of running. The same applies when the function of setting the values of the permission flags (F72, F73, F74) is shared among the control circuits. In other words, even if the control circuits are not activated as a steer-by-wire system, the steering wheel 11 and the shift lever will not be unlocked and the powertrain will not be started.

<Effects of the Fourth Embodiment>
Therefore, according to the fourth embodiment, the following effects can be obtained.
(4-1) When the start switch SW is turned off, each control circuit (41A, 42A, 51A, 52A) initializes the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74. That is, each control device sets the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 to "prohibited."

If the start switch SW is turned on again during the execution period of power latch control after the start switch SW is turned off, and there is a control circuit that does not recognize that the start switch SW is on, the control circuits will not activate as a steer-by-wire system. However, there is a risk that other control circuits that recognize that the start switch SW is on will send the values of each permission flag (F72, F73, F74) to the in-vehicle system 72.

At this time, because the values of each permission flag (F72, F73, F74) are set to "prohibited," the steering wheel 11 and shift lever will not be unlocked and the powertrain will not be started. This prevents the vehicle from transitioning to a state where it can be driven, or the execution of processing to transition the vehicle to a state where it can be driven, even though each control circuit has not been activated as a steer-by-wire system.

(4-2) When the start switch SW is turned off, each control circuit (41A, 42A, 51A, 52A) initializes the value of the meter notification flag F75. That is, each control circuit switches the value of the meter notification flag F75 to a value corresponding to the current state of the steer-by-wire system. For example, if a break in the power supply path to a specific control circuit is detected when the start switch SW is turned off, each control circuit sets the value of the meter notification flag F75 to "abnormal." If the start switch SW is turned on again during the execution of power latch control after the start switch SW is turned off, the control circuit that recognizes that the start switch SW is on transmits the value of the meter notification flag F75 to the in-vehicle system 72. Based on the fact that the value of the meter notification flag F75 is set to "abnormal," the meter control device switches the illumination state of the indicator lamp from an off state to an on state indicating an abnormality in the steer-by-wire system. The illumination state indicating an abnormality is, for example, a yellow illumination state. Therefore, the driver can immediately visually recognize any abnormalities in the steer-by-wire system without having to wait for each control circuit to complete power latch control.

Fifth Embodiment
Next, a fifth embodiment will be described in which the vehicle control device is embodied in a steer-by-wire steering device. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 to 3. Therefore, the same members and configurations as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

This embodiment differs from the third embodiment in the content of the processing executed by each control circuit (41A, 42A, 51A, 52A) when the start switch SW is turned on.
When the start switch SW is turned on, each control circuit sets the value of an activation status flag F79. The activation status flag F79 is information indicating whether all of the control circuits recognize that the start switch SW is on. The control circuits mutually confirm whether they recognize that the start switch SW is on, i.e., that the vehicle power supply is on, through the first mutual confirmation MC1, second mutual confirmation MC2, third mutual confirmation MC3, and fourth mutual confirmation MC4 shown in FIG. 3 . When a control circuit determines that even one of the control circuits has not recognized that the start switch SW is off, the control circuit sets the value of the activation status flag F79 to “not activated.” Setting the value of the activation status flag F79 to “not activated” indicates that the control circuit cannot be activated as a steer-by-wire system. When a control circuit determines that all of the control circuits recognize that the start switch SW is on, the control circuit sets the value of the activation status flag F79 to “activated.” The activation status flag F79 being set to "activated" indicates that each control circuit is in a state where it can be activated as a steer-by-wire system.

Next, a first mode of state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.
As an example, assume that a disconnection occurs in the power supply path to a specific control circuit during the period from when the start switch SW is turned off until the start switch SW is turned on again during power latch control. The power supply path includes the start switch SW. Therefore, the power supply voltage is not supplied to the specific control circuit via the start switch SW. Therefore, the specific control circuit cannot recognize that the start switch SW is turned on. Furthermore, the specific control circuit is not started.

As shown in the time chart in Figure 11, each control circuit executes power latch control when the start switch SW is turned off (time T11) while normal control is being executed. When the start switch SW is turned off, the power supply voltage level switches from "Hi" to "Lo." When the power supply voltage level switches from "Hi" to "Lo," each control circuit switches the value of the communication permission flag F71 from "Permitted" to "Prohibited."

During power latch control, the values of the first unlock permission flag F72, the second unlock permission flag F73, the start permission flag F74, and the meter notification flag F75 are maintained at the same values as during normal control immediately before the start switch SW is turned off. That is, the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74 are each maintained at "permitted." The value of the meter notification flag F75 is maintained at "normal." The value of the startup status flag F79 is maintained at "started."

During the execution period of power latch control after the start switch SW is turned off, when the start switch SW is turned on again (time T12), power supply voltage is not supplied to the specific control circuit via the power supply path that includes the start switch SW. As a result, the specific control circuit is unable to recognize that the start switch SW is on. As a result, the specific control circuit is not activated.

The power supply voltage is supplied to the three control circuits other than the specific control circuit via a power supply path that includes the start switch SW. In this case, the specific control circuit cannot recognize that the start switch SW is on, so a situation cannot occur in which all of the control circuits recognize that the start switch SW is on. Therefore, the three control circuits other than the specific control circuit set the value of the activation status flag F79 to "not activated."

The three control circuits other than the specific control circuit set the value of the communication permission flag F71 to "permitted" when the power supply voltage supplied when the start switch SW is turned on reaches a value within the operating voltage range. This allows the three control circuits other than the specific control circuit to communicate via the in-vehicle network 71.

When the value of the communication permission flag F71 switches from "prohibited" to "permitted," the three control circuits other than the specific control circuit transmit the values of the first unlock permission flag F72, second unlock permission flag F73, start permission flag F74, meter notification flag F75, and activation status flag F79 to the in-vehicle system 72 via the in-vehicle network 71. The process of transmitting the value of the activation status flag F79 set to "not activated" to the in-vehicle system 72 is a process for requesting the in-vehicle system 72 to ignore the values of the first unlock permission flag F72, second unlock permission flag F73, and start permission flag F74.

For this reason, when the value of the activation status flag F79 is set to "not activated," the in-vehicle system 72 ignores the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74. In other words, even if the value of the first unlock permission flag F72, the value of the second unlock permission flag F73, and the value of the start permission flag F74 are all set to "permitted," the in-vehicle system 72 will not operate.

In other words, the steering lock control device does not execute the process to unlock the steering wheel 11. As a result, the steering wheel 11 remains locked. Furthermore, the shift lock control device does not execute the process to unlock the shift lever. As a result, the shift lever remains locked. Furthermore, the powertrain control device does not execute the process to start the powertrain. As a result, the powertrain remains stopped.

As a result, even if the four control circuits (41A, 42A, 51A, 52A) are in a state where they cannot be activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

When the start switch SW is turned on and the activation status flag F79 is set to "not activated," the meter control device switches the indicator light's illumination state from an off state to, for example, a red illumination state. This is because the activation status flag F79 being set to "not activated" indicates that each control circuit cannot be activated as a steer-by-wire system. The driver can immediately recognize an abnormality in the steer-by-wire system visually, without waiting for each control circuit to complete power latch control.

The same applies if the four control circuits (41A, 42A, 51A, 52A) simply do not recognize the start switch SW as ON at the same time. That is, the control circuit that first recognizes the start switch SW as ON may transmit the values of each flag (F72, F73, F74, F75, F79) to the in-vehicle system 72 via the in-vehicle network 71. However, if there is a control circuit that does not recognize the start switch SW as ON, the value of the activation status flag F79 is set to "not activated." Therefore, even if each permission flag (F72, F73, F74) set to "enabled" is transmitted to the in-vehicle system 72, the in-vehicle system 72 will not operate. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven.

The same applies to the case where the function of setting the values of the permission flags (F72, F73, F74) is shared and executed by the respective control circuits.
For example, if only the second reaction force control circuit 42A has the function of setting the values of the first unlock permission flag F72 and the second unlock permission flag F73, it is possible that the second reaction force control circuit 42A will recognize that the start switch SW is turned on before the other three control circuits. In this case, there is a risk that the second reaction force control circuit 42A will transmit the values of the first unlock permission flag F72 and the second unlock permission flag F73 to the in-vehicle system 72 via the in-vehicle network 71.

However, if there is a control circuit that does not recognize that the start switch SW is on, the value of the activation status flag F79 is set to "not activated." Therefore, even if the value of the first unlock permission flag F72 set to "enabled" is sent to the in-vehicle system 72, the steering lock control device will not begin executing the process to unlock the steering wheel 11. Similarly, even if the value of the second unlock permission flag F73 set to "enabled" is sent to the in-vehicle system 72, the shift lock control device will not begin executing the process to unlock the shift lever. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the steering wheel 11 and the shift lever will not be unlocked. The same applies when a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A. The power supply path is a power supply path that includes the start switch SW.

Furthermore, for example, if the second reaction force control circuit 42A and the first steering control circuit 51A have the function of setting the value of the start permission flag F74, it is possible that the second reaction force control circuit 42A or the first steering control circuit 51A will recognize that the start switch SW is on before the other three control circuits. In this case, there is a risk that the second reaction force control circuit 42A or the first steering control circuit 51A will transmit the value of the start permission flag F74 to the on-board system 72 via the on-board network 71.

However, if there is a control circuit that does not recognize that the start switch SW is on, the value of the activation status flag F79 is set to "not activated." Therefore, even if the start permission flag F74 set to "enabled" is sent to the on-board system 72, the powertrain control device will not begin executing processing to operate the powertrain. Therefore, even if the four control circuits are not activated as a steer-by-wire system, the powertrain will not start. Incidentally, the same applies if a break occurs in the power supply path to a specific control circuit other than the second reaction force control circuit 42A or the first turning control circuit 51A. The power supply path is a power supply path that includes the start switch SW.

<Second Aspect of State Transition of Control Circuit>
Next, a second aspect of the state transition of each control circuit (41A, 42A, 51A, 52A) in this embodiment will be described.

As shown in the time chart in Figure 12, during normal control immediately before the start switch SW is turned off, a situation may occur in which a specific control circuit is unable to recognize that the start switch SW is on due to a break in the power supply path to that control circuit. The power supply path is the one that includes the start switch SW. Even in this case, when the start switch is turned off, each control circuit executes processing similar to the first mode shown in Figure 11 above. That is, when each control circuit determines that even one of the control circuits has not recognized that the start switch SW is off, it sets the value of the activation status flag F79 to "not activated."

As a result, even if the four control circuits are not activated as a steer-by-wire system, the vehicle will not transition to a state where it can be driven. The same is true when the function of setting the values of each permission flag (F72, F73, F74) is shared among the control circuits. In other words, even if the control circuits are not activated as a steer-by-wire system, the steering wheel 11 and shift lever will not be unlocked and the powertrain will not be started.

<Effects of the Fifth Embodiment>
Therefore, according to the fifth embodiment, the following effects can be obtained.
(5-1) When the start switch SW is turned on, each of the control circuits (41A, 42A, 51A, 52A) sets the value of the activation status flag F79 to "not activated" if there is at least one control circuit that does not recognize that the start switch SW is turned on. When the value of the activation status flag F79 is set to "not activated," the in-vehicle system 72 ignores the values of the first unlock permission flag F72, the second unlock permission flag F73, and the start permission flag F74. This makes it possible to prevent the vehicle from transitioning to a state where it can travel, or to prevent processing for transitioning the vehicle to a state where it can travel, from being executed even when each of the control circuits has not been activated as a steer-by-wire system.

(5-2) When the start switch SW is turned on and the activation status flag F79 is set to "not activated," the meter control device switches the indicator lamp from an off state to, for example, a red illuminated state. This is because the activation status flag F79 being set to "not activated" indicates that each control circuit cannot be activated as a steer-by-wire system. Therefore, the driver can immediately visually recognize an abnormality in the steer-by-wire system without waiting for each control circuit to complete power latch control.

<Other embodiments>
Each embodiment may be modified as follows.
In the first embodiment and the third to fifth embodiments, the initial sequence executed by each control circuit (41A, 42A, 51A, 52A) at startup may include a midpoint learning process and a steering angle synchronization process.

The midpoint learning process is a process for learning the neutral steering position of the steering wheel 11. The steering device 10 has a stopper mechanism that restricts the rotation of the steering wheel 11 to limit the steering angle of the steering wheel 11. The stopper mechanism, for example, restricts the steering range of the steering wheel 11 to less than 360°. The reaction force control device 40 controls the reaction force motor 21 to move the steering wheel 11 to a first operating limit and then reverse it to a second operating limit. The reaction force control device 40 then calculates the midpoint of the steering angle based on the rotation angle of the reaction force motor 21 at the start and end of the reverse movement of the steering wheel 11. The midpoint of the steering angle corresponds to the motor midpoint, which is the rotational position of the reaction force motor 21 when the steering wheel 11 is in the neutral steering position. The reaction force control device 40 stores the midpoint of the steering angle or the motor midpoint in memory as the neutral steering position of the steering wheel 11.

However, the reaction force control device 40 learns the neutral steering position of the steering wheel 11 when the information about the neutral steering position stored in memory is lost. This applies, for example, when the vehicle power is turned on for the first time after a new battery is installed in the vehicle. This is because when the battery is removed from the vehicle during battery replacement, the power supply to the reaction force control device 40 is no longer supplied, and the information about the neutral steering position stored in the reaction force control device 40's memory is lost.

Depending on the product specifications, the reaction force control device 40 may be configured to perform the midpoint learning process each time the vehicle power is turned on, or may be configured to perform the midpoint learning process when the reliability of the information related to the steering neutral position stored in memory has decreased.

The steering angle synchronization process is a process for correcting the rotational position of the steering wheel 11. When the rotational position of the steering wheel 11 is different from the rotational position corresponding to the steered position of the steered wheels 15, the reaction force control device 40 drives the reaction force motor 21 so that the rotational position of the steering wheel 11 becomes the rotational position corresponding to the steered position of the steered wheels 15.

For example, when the vehicle power supply is turned off, the reaction force control device 40 stores the steering angle θs detected immediately before as the reference steering angle. The reference steering angle is used as a reference for determining whether the steering wheel 11 is rotating while the vehicle power supply is turned off. When the steering angle θs immediately after the vehicle power supply is turned on does not match the reference steering angle, the reaction force control device 40 calculates the difference between the steering angle θs immediately after the vehicle power supply is turned on and the reference steering angle, and controls the power supply to the reaction force motor 21 to eliminate this difference.

The reaction force control device 40 may also calculate the difference between the value of the steering angle θs immediately after the vehicle power supply is turned on and the value obtained by multiplying the steering angle θw immediately after the vehicle power supply is turned on by the reciprocal of the steering angle ratio, and control the power supply to the reaction force motor 21 so as to eliminate this difference.

- In the first embodiment, the reaction force motor 21 and the steering motor 31 have two winding groups, but they may also have a single winding group. In this case, the reaction force control device 40 may have only one of the first system circuit 41 and the second system circuit 42. In this case, the steering control device 50 may have only one of the first system circuit 51 and the second system circuit 52. Here, we will take as an example a case where the reaction force control device 40 has only the first system circuit 41 and the steering control device 50 has only the first system circuit 51. The first reaction force control circuit 41A sets the value of flag F11 depending on the result of determining whether the start switch SW is on. The first steering control circuit 51A sets the value of flag F31 depending on the result of determining whether the start switch SW is on. When the value of flag F11 and the value of flag F31 are both "1," the first reaction force control circuit 41A and the first turning control circuit 51A determine that they both recognize that the start switch SW is on. This triggers the first reaction force control circuit 41A and the first turning control circuit 51A to start up. Therefore, if the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off, even if the first reaction force control circuit 41A and the first turning control circuit 51A recognize that the vehicle power supply is on at different times, the timing at which the first reaction force control circuit 41A and the first turning control circuit 51A start up can be synchronized. This also applies when the reaction force control device 40 has only the second system circuit 42 and when the turning control device 50 has only the second system circuit 52. This allows the drive of the reaction force motor and the turning motor to be appropriately controlled. The first reaction force control circuit 41A or the second reaction force control circuit 42A corresponds to a reaction force control circuit. The first turning control circuit 51A or the second turning control circuit 52A corresponds to a turning control circuit. This configuration may be applied to the third to fifth embodiments.

- In the first embodiment, the control circuits (41A, 42A, 51A, 52A) may mutually check the values of their flags (F11, F21, F31, F41) to determine whether all control circuits have recognized that the vehicle power supply is on. However, in this case, the first reaction force control circuit 41A and the second turning control circuit 52A are configured to be able to exchange information with each other via a communication line. The second reaction force control circuit 42A and the first turning control circuit 51A are also configured to be able to exchange information with each other via a communication line. This configuration may be applied to the third to fifth embodiments.

- In the first embodiment, one specific control circuit among the control circuits (41A, 42A, 51A, 52A) may check the flag values of the other control circuits to determine whether all control circuits have recognized that the vehicle power supply is on. The specific control circuit notifies the other control circuits of the determination result of whether all control circuits have recognized that the vehicle power supply is on. In this case, however, the first reaction force control circuit 41A and the second turning control circuit 52A, or the second reaction force control circuit 42A and the first turning control circuit 51A, are configured to be able to exchange information with each other via communication lines. This configuration may also be applied to the third to fifth embodiments.

- In the first embodiment, the vehicle control device is embodied in a steer-by-wire steering device, and in the second embodiment, the vehicle control device is embodied in an electric power steering device. However, it may also be embodied in, for example, a door mirror device that opens and closes in conjunction with door locks. The present invention can be embodied in any in-vehicle system that requires synchronized state transitions between multiple control circuits. However, the event that triggers a synchronized state transition is not limited to turning on the vehicle power supply. As with the first and second embodiments, the third to fifth embodiments can also be embodied in any in-vehicle system that requires synchronized state transitions between multiple control circuits.

REFERENCE SIGNS LIST 11...Steering wheel 15...Steered wheel 21...Reaction motor 31...Steered motor 41A...First reaction force control circuit 42A...Second reaction force control circuit 51A...First turning control circuit 52A...Second turning control circuit 70...Assist motor 72...In-vehicle system N11...First system winding group of reaction force motor N12...Second system winding group of reaction force motor N21...First system winding group of turning motor N22...Second system winding group of turning motor N31...First system winding group of assist motor N32...Second system winding group of assist motor

Claims (9)

The control circuit includes a plurality of control circuits that are activated when the vehicle power supply is turned on to control the control target, and that are activated when the vehicle power supply is turned off to perform power latch control to maintain power for a predetermined period of time,
When the vehicle power supply is turned on while power latch control is being executed after the vehicle power supply is turned off, the plurality of control circuits wait for all of the control circuits, including the control circuit itself, to recognize that the vehicle power supply is on before starting up. The plurality of control circuits set flag values according to the recognition result of whether the vehicle power supply is on or not,
The vehicle control device according to claim 1 , wherein each of the plurality of control circuits determines whether or not all of the control circuits, including itself, recognize that the vehicle power supply is on, based on the value of the flag. The control object is
a reaction motor having two winding groups and generating a steering reaction force to be applied to a steering wheel whose power transmission between the steering wheel and the steered wheels is separated;
a steering motor that generates a steering force for steering the steered wheels,
The plurality of control circuits include:
a first reaction force control circuit that controls power supply to a first system of windings of the reaction force motor;
a second reaction force control circuit that controls power supply to a second system of windings of the reaction force motor;
a first steering control circuit that controls power supply to a first system of windings of the steering motor;
3. The vehicle control device according to claim 1, further comprising: a second steering control circuit that controls power supply to a second system of windings of the steering motor. the first reaction force control circuit and the second reaction force control circuit perform a first mutual confirmation in which they confirm with each other whether they have recognized that a vehicle power source is on;
the first turning control circuit and the second turning control circuit perform a second mutual confirmation in which they confirm with each other whether they have recognized that the vehicle power supply is on;
the first reaction force control circuit and the first steering control circuit perform a third mutual confirmation in which they mutually confirm the success or failure of the first mutual confirmation and the second mutual confirmation, and when the first mutual confirmation and the second mutual confirmation are successful, it is determined that all of the control circuits have recognized that the vehicle power supply is on;
4. The vehicle control device according to claim 3, wherein the second reaction force control circuit and the second steering control circuit perform a fourth mutual confirmation in which they mutually confirm the success or failure of the first mutual confirmation and the second mutual confirmation, and when the first mutual confirmation and the second mutual confirmation are successful, it is determined that all of the control circuits have recognized that the vehicle power supply is on. the controlled object includes a reaction motor which is a source of generating a steering reaction force applied to a steering wheel whose power transmission is separated from that of the steered wheels, and a turning motor which is a source of generating a turning force for turning the steered wheels,
the plurality of control circuits include a reaction force control circuit that controls the reaction force motor, and a steering control circuit that controls the steering motor,
3. The vehicle control device according to claim 1, wherein the reaction force control circuit and the steering control circuit confirm with each other whether they have recognized that the vehicle power supply is on. the controlled object includes an assist motor that generates an assist force to assist the operation of a steering wheel,
the assist motor has a first winding group and a second winding group,
the plurality of control circuits include a first assist control circuit that controls power supply to the first system of winding groups, and a second assist control circuit that controls power supply to the second system of winding groups;
3. The vehicle control device according to claim 1, wherein the first assist control circuit and the second assist control circuit confirm with each other whether they have recognized that the vehicle power supply is turned on. the control circuit is configured to be able to communicate with an in-vehicle system that executes a process for transitioning the vehicle to a drivable state;
3. The vehicle control device according to claim 1, wherein the control circuit is configured such that, when the vehicle power is turned on while power latch control is being executed after the vehicle power is turned off, the control circuit waits until all of the control circuits, including the control circuit itself, recognize that the vehicle power is on before allowing communication with the in-vehicle system to be executed. the control circuit is configured to be able to communicate with an in-vehicle system that executes a process for transitioning the vehicle to a drivable state, and is configured to be allowed to communicate with the in-vehicle system when the vehicle power supply is turned on;
the control circuit has information indicating whether or not the in-vehicle system is permitted to execute the process;
When the vehicle power supply is turned off during execution of control of the control target, the control circuit initializes the information by changing the content of the information from a content that allows the in-vehicle system to execute the process to a content that requests the in-vehicle system to prohibit execution of the process;
3. The vehicle control device according to claim 1, wherein the information is transmitted to the in-vehicle system when the vehicle power supply is turned on during execution of power latch control after the vehicle power supply has been turned off. the control circuit is configured to be able to communicate with an in-vehicle system that executes a process for transitioning the vehicle to a drivable state, and is configured to be allowed to communicate with the in-vehicle system when the vehicle power supply is turned on;
the control circuit has information indicating whether or not the in-vehicle system is permitted to execute the process;
the control circuit is configured to, when the vehicle power supply is turned off during execution of the control of the control object, hold the content of the information as the content at the time of execution of the control of the control object, which is the content that permits the in-vehicle system to execute the process, and to transmit the information to the in-vehicle system when the vehicle power supply is turned on during execution of the power latch control after the vehicle power supply is turned off;
3. The vehicle control device according to claim 1, wherein the control circuit is configured to execute processing to request the in-vehicle system to ignore the information when the vehicle power is turned on during execution of power latch control after the vehicle power is turned off and all of the control circuits, including the control circuit itself, are not in a state where they recognize that the vehicle power is on.