JP7538652B2 - Control device - Google Patents

Description

The present invention relates to a control device.

Technology related to slip suppression control for suppressing wheel slippage has been proposed in order to stabilize the vehicle body behavior. For example, Patent Document 1 discloses technology that suppresses slippage by reducing the vehicle torque relative to the required torque when the wheels slip.

JP 2007-049825 A

In vehicles equipped with a drive motor as a drive source, slip determination to determine whether or not a wheel is slipping may be performed based on the amount of change in the rotation speed of the drive motor over time. Here, when the vehicle goes over a step, a large change in the rotation speed of the drive motor over time occurs, which may result in an erroneous determination that slip is occurring. Therefore, in order to prevent erroneous determination in the slip determination, it is conceivable to make the determination conditions for the slip determination stricter so that it is less likely that slip is occurring. However, as a result, even when slip is actually occurring, it may be determined that slip is not occurring, and slip suppression control may not be executed.

In view of these problems, the present invention aims to provide a control device that can appropriately execute slip suppression control depending on whether or not wheel slippage occurs.

In order to solve the above problem, the control device of the present invention comprises a slip determination unit that determines whether or not slip has occurred in the vehicle's wheels based on the amount of change in the rotation speed of a drive motor over time; a step-crossing determination unit that determines whether or not the vehicle is crossing a step; and a control unit that performs slip suppression control in accordance with the determination result by the slip determination unit when it is determined that the vehicle is not crossing a step, and does not perform slip suppression control when it is determined that the vehicle is crossing a step , the drive motors include a front-wheel drive motor capable of outputting power to drive the front wheels, and a rear-wheel drive motor capable of outputting power to drive the rear wheels, and the step-crossing determination unit determines that the vehicle is crossing a step when, during travel of the vehicle, a time change in the rotation speed of more than a predetermined amount occurs in both the front-wheel drive motor and the rear-wheel drive motor, without going through a situation in which a time change in the rotation speed of more than a predetermined amount occurs in only one of the front-wheel drive motor and the rear-wheel drive motor .

The step-crossing determination unit may determine that the vehicle is crossing a step when a time change of the rotation speed of the drive motor occurs that is equal to or greater than a predetermined amount of change, and the time change of the rotation speed of the drive motor is in the direction of deceleration.

The slip determination unit may determine that wheel slip has occurred when a state in which the change in the rotation speed of the drive motor over time is equal to or greater than a time change threshold continues for a duration threshold or longer.

The step-crossing determination unit may determine that the vehicle has finished crossing the step if the change in the rotation speed of the drive motor over time falls below a time-change threshold value after determining that the vehicle is crossing the step.

According to the present invention, it is possible to appropriately execute slip suppression control depending on whether or not wheel slip occurs.

1 is a schematic diagram showing a schematic configuration of a vehicle on which a control device according to an embodiment of the present invention is mounted; FIG. 2 is a block diagram showing an example of a functional configuration of a control device according to an embodiment of the present invention. 4 is a flowchart showing an example of an overall process flow performed by a control device according to an embodiment of the present invention. 11 is a diagram showing an example of a transition of the motor rotation speed and the amount of change in the motor rotation speed over time when starting in a case where no wheel slip occurs; FIG. 11 is a diagram showing an example of a transition of the motor rotation speed and the amount of change in the motor rotation speed over time when starting in a case where wheel slip occurs; FIG. 11 is a schematic diagram showing an example of a relationship between a time change threshold and a duration threshold. FIG. 11A and 11B are diagrams illustrating an example of a transition of a motor rotation speed and a time change in the motor rotation speed when going over a step. 5 is a flowchart showing a first example of a flow of a process of determining whether or not a step has been overcome among the processes performed by the control device according to the embodiment of the present invention. 10 is a flowchart showing a second example of the flow of a process of determining whether or not a step has been overcome among the processes performed by the control device according to the embodiment of the present invention. This is a flowchart showing an example of the flow of the step-crossing determination process performed in the current processing cycle when the step-crossing determination in the previous processing cycle determines that the vehicle is crossing a step, among the processes performed by the control device according to an embodiment of the present invention.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific values shown in the embodiment are merely examples to facilitate understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid duplicated explanations, and elements not directly related to the present invention are not illustrated.

<Vehicle configuration>
The configuration of a vehicle 1 equipped with a control device 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

Figure 1 is a schematic diagram showing the general configuration of vehicle 1. In Figure 1, vehicle 1 is shown with the forward movement direction of vehicle 1 defined as the forward direction, the backward movement direction opposite to the forward movement direction defined as the rearward direction, and the left and right sides when facing forward defined as the left and right directions, respectively.

Vehicle 1 is an electric vehicle that has a drive motor as a drive source and runs using the torque output from the drive motor.

Note that the vehicle 1 described below is merely one example of a vehicle in which the control device according to the present invention is installed, and as described below, the configuration of a vehicle in which the control device according to the present invention is installed is not particularly limited to the configuration of vehicle 1.

As shown in FIG. 1, the vehicle 1 includes front wheels 11a, 11b, rear wheels 11c, 11d, a front differential 13f, a rear differential 13r, a front-wheel drive motor 15f, a rear-wheel drive motor 15r, inverters 17f, 17r, a battery 19, a front-wheel motor speed sensor 21f, a rear-wheel motor speed sensor 21r, and a control device 100.

Hereinafter, when there is no distinction between the front wheels 11a, 11b, rear wheels 11c, and rear wheels 11d, they will also be referred to simply as wheels 11. When there is no distinction between the front wheel drive motor 15f and the rear wheel drive motor 15r, they will also be referred to simply as drive motor 15. When there is no distinction between the inverter 17f and the inverter 17r, they will also be referred to simply as inverter 17. When there is no distinction between the front wheel motor speed sensor 21f and the rear wheel motor speed sensor 21r, they will also be referred to simply as motor speed sensor 21.

The front wheel drive motor 15f outputs torque to drive the front wheels 11a and 11b. Note that the front wheel 11a corresponds to the left front wheel, and the front wheel 11b corresponds to the right front wheel.

The front-wheel drive motor 15f is driven by power supplied from the battery 19. The front-wheel drive motor 15f is connected to the front differential device 13f. The front differential device 13f is connected to the front wheels 11a, 11b via drive shafts. The torque output from the front-wheel drive motor 15f is transmitted to the front differential device 13f, and then distributed and transmitted to the front wheels 11a, 11b by the front differential device 13f.

The front-wheel drive motor 15f is, for example, a multi-phase AC motor, and is connected to the battery 19 via an inverter 17f. The DC power supplied from the battery 19 is converted to AC power by the inverter 17f and supplied to the front-wheel drive motor 15f.

In addition to the function of outputting drive torque for the front wheels 11a, 11b, the front-wheel drive motor 15f may also function as a generator that generates electricity using the kinetic energy of the front wheels 11a, 11b. When the front-wheel drive motor 15f functions as a generator, electricity is generated by the front-wheel drive motor 15f and a braking force is applied to the vehicle 1 through regenerative braking. The AC power generated by the front-wheel drive motor 15f is converted to DC power by the inverter 17f and supplied to the battery 19. This charges the battery 19.

The rear wheel drive motor 15r outputs torque to drive the rear wheels 11c and 11d. Note that the rear wheel 11c corresponds to the left rear wheel, and the rear wheel 11d corresponds to the right rear wheel.

The rear-wheel drive motor 15r is driven by power supplied from a battery 19. The rear-wheel drive motor 15r is connected to the rear differential device 13r. The rear differential device 13r is connected to the rear wheels 11c, 11d via drive shafts. The torque output from the rear-wheel drive motor 15r is transmitted to the rear differential device 13r, and then distributed and transmitted to the rear wheels 11c, 11d by the rear differential device 13r.

The rear wheel drive motor 15r is, for example, a polyphase AC motor, and is connected to the battery 19 via an inverter 17r. The DC power supplied from the battery 19 is converted to AC power by the inverter 17r and supplied to the rear wheel drive motor 15r.

In addition to the function of outputting drive torque for the rear wheels 11c, 11d, the rear-wheel drive motor 15r may also function as a generator that generates electricity using the kinetic energy of the rear wheels 11c, 11d. When the rear-wheel drive motor 15r functions as a generator, electricity is generated by the rear-wheel drive motor 15r and a braking force is applied to the vehicle 1 by regenerative braking. The AC power generated by the rear-wheel drive motor 15r is converted to DC power by the inverter 17r and supplied to the battery 19. This charges the battery 19.

The front wheel motor rotation speed sensor 21f detects the rotation speed of the front wheel drive motor 15f and outputs the detection result. The rotation speed of the front wheel drive motor 15f detected by the front wheel motor rotation speed sensor 21f can correspond to information indicating the wheel speed of the front wheels 11a, 11b.

The rear wheel motor rotation speed sensor 21r detects the rotation speed of the rear wheel drive motor 15r and outputs the detection result. The rotation speed of the rear wheel drive motor 15r detected by the rear wheel motor rotation speed sensor 21r can correspond to information indicating the wheel speed of the rear wheels 11c, 11d.

The control device 100 includes a CPU (Central Processing Unit), which is an arithmetic processing device; a ROM (Read Only Memory), which is a storage element that stores programs and calculation parameters used by the CPU; and a RAM (Random Access Memory), which is a storage element that temporarily stores parameters that change as appropriate during CPU execution.

The control device 100 communicates with each device mounted on the vehicle 1. For example, the control device 100 communicates with the inverter 17f, the inverter 17r, the front wheel motor rotation speed sensor 21f, and the rear wheel motor rotation speed sensor 21r. The communication between the control device 100 and each device is realized, for example, using CAN (Controller Area Network) communication.

The functions of the control device 100 according to this embodiment may be divided among multiple control devices, or multiple functions may be realized by one control device. When the functions of the control device 100 are divided among multiple control devices, the multiple control devices may be connected to each other via a communication bus such as a CAN.

Figure 2 is a block diagram showing an example of the functional configuration of the control device 100.

For example, as shown in FIG. 2, the control device 100 has an acquisition unit 110, a determination unit 120, and a control unit 130.

The acquisition unit 110 acquires various information used in the processes performed by the determination unit 120 and the control unit 130, and outputs the information to the determination unit 120 and the control unit 130. For example, the acquisition unit 110 acquires information from the front wheel motor rotation speed sensor 21f and the rear wheel motor rotation speed sensor 21r.

The determination unit 120 performs various determinations. The determination results by the determination unit 120 are used in the processing performed by the control unit 130. The determination unit 120 includes, for example, a slip determination unit 121 and a step-crossing determination unit 122.

The slip determination unit 121 performs slip determination to determine whether or not slip has occurred in the wheel 11. Slip refers to a phenomenon in which the slip ratio of the wheel 11 becomes excessively large, causing the wheel 11 to spin freely. The slip ratio is a value obtained by dividing the difference between the wheel speed and the vehicle speed by the vehicle speed. Slip can occur, for example, when the vehicle 1 enters a low μ road, such as a frozen road.

The step-crossing determination unit 122 performs step-crossing determination to determine whether the vehicle 1 is crossing a step. Examples of steps include a strip-shaped protruding portion such as a speed bump provided on the road surface, or a joint between road surfaces with a difference in height, such as a joint between a roadway and a sidewalk.

The control unit 130 controls the operation of each device in the vehicle 1, thereby controlling the running of the vehicle 1. In particular, the control unit 130 controls the operation of the front wheel drive motor 15f and the rear wheel drive motor 15r.

Specifically, the control unit 130 controls the supply of power between the battery 19 and the front-wheel drive motor 15f by controlling the operation of the switching elements of the inverter 17f. This controls the torque of the front wheels 11a, 11b output by the front-wheel drive motor 15f. The control unit 130 also controls the supply of power between the battery 19 and the rear-wheel drive motor 15r by controlling the operation of the switching elements of the inverter 17r. This controls the torque of the rear wheels 11c, 11d output by the rear-wheel drive motor 15r. As described above, the control unit 130 can individually control the torque of the front wheels 11a, 11b and the torque of the rear wheels 11c, 11d.

The control unit 130 can switch the drive mode of the vehicle 1 between a front-wheel drive mode and a four-wheel drive mode. The front-wheel drive mode is a drive mode in which the front wheels 11a, 11b are driven while the rear wheels 11c, 11d are not driven. The four-wheel drive mode is a drive mode in which the front wheels 11a, 11b and the rear wheels 11c, 11d are driven. The control unit 130 may switch the drive mode, for example, in response to an input operation by the driver. The control unit 130 may also switch the drive mode, for example, in response to the running state of the vehicle 1. Note that the control unit 130 may be capable of executing a rear-wheel drive mode in which the front wheels 11a, 11b are not driven while the rear wheels 11c, 11d are driven instead of the front-wheel drive mode or in addition to the front-wheel drive mode.

Here, the control unit 130 can execute slip prevention control to prevent slippage of the wheels 11. For example, as the slip prevention control, the control unit 130 can execute torque down control to reduce the torque of the vehicle 1 relative to the required torque.

In this embodiment, the control unit 130 performs slip suppression control in accordance with the judgment result by the slip judgment unit 121 when it is judged that the vehicle 1 is not going over a step, and does not perform slip suppression control when it is judged that the vehicle 1 is going over a step. This makes it possible to appropriately execute slip suppression control in accordance with the occurrence or non-occurrence of slip of the wheel 11. Details of the processing related to the slip suppression control by the control device 100 will be described later.

<Control device operation>
Next, the operation of the control device 100 according to the embodiment of the present invention will be described with reference to FIGS.

Figure 3 is a flowchart showing an example of the overall processing flow performed by the control device 100. Specifically, the control flow shown in Figure 3 is repeatedly started at set time intervals when slip suppression control is not being executed.

When the control flow shown in FIG. 3 is started, first, in step S101, the slip determination unit 121 executes a slip determination.

In slip determination, the slip determination unit 121 determines whether or not slip has occurred in the wheel 11 based on the amount of change over time in the rotation speed of the drive motor 15. In this specification, the rotation speed of the drive motor 15 is also referred to as the motor rotation speed. The amount of change over time in the motor rotation speed means the amount of change per unit time in the motor rotation speed.

When the wheel 11 slips, the wheel speed of the wheel 11 increases rapidly, causing a large change over time in the rotation speed of the drive motor 15 connected to the wheel 11. Therefore, the slip determination unit 121 determines that the wheel 11 has slipped, for example, when a state in which the time change in the rotation speed of the drive motor 15 is equal to or greater than the time change threshold continues for equal to or greater than the duration threshold.

Specifically, the slip determination unit 121 performs slip determination for the front wheels 11a, 11b and for the rear wheels 11c, 11d separately. In other words, the slip determination unit 121 determines that slip has occurred in the front wheels 11a, 11b when the state in which the time change in the rotation speed of the front-wheel drive motor 15f is equal to or greater than the time change threshold continues for a duration threshold or longer. The slip determination unit 121 also determines that slip has occurred in the rear wheels 11c, 11d when the state in which the time change in the rotation speed of the rear-wheel drive motor 15r is equal to or greater than the time change threshold continues for a duration threshold or longer.

Figure 4 is a diagram showing an example of the transition of the motor rotation speed and the amount of change in the motor rotation speed over time when starting when no slippage of the wheels 11 occurs. When the drive motor 15 starts to drive, as shown in Figure 4, the amount of change in the motor rotation speed over time rises sharply for a short period of time due to twisting or backlash of the drive motor 15. In other words, a large change in the motor rotation speed over time occurs for a short period of time. In the example of Figure 4, a state in which the amount of change in the motor rotation speed over time is equal to or greater than the time change threshold continues between time t1 and time t2. However, since the duration of this state is shorter than the duration threshold, the slip determination unit 121 determines that no slippage of the wheels 11 is occurring.

Figure 5 is a diagram showing an example of the transition of the motor rotation speed and the amount of change in the motor rotation speed over time when starting when slippage of the wheel 11 occurs. As described above, when the wheel 11 slips, the wheel speed of the wheel 11 increases rapidly. Therefore, as shown in Figure 5, the amount of change in the motor rotation speed over time also increases rapidly. In other words, a large change in the motor rotation speed over time occurs. In the example of Figure 5, from time t3 onwards, a state in which the amount of change in the motor rotation speed over time is equal to or greater than the time change threshold continues. Because the duration of this state is equal to or greater than the duration threshold, the slip determination unit 121 determines that slippage of the wheel 11 is occurring.

Figure 6 is a schematic diagram showing an example of the relationship between the time change threshold and the duration threshold. As shown in Figure 6, the larger the time change threshold, the shorter the duration threshold. The time change threshold and duration threshold used in the slip determination by the slip determination unit 121 are preset to, for example, predetermined values that satisfy the relationship shown in Figure 6. As a result, when there is no slip of the wheel 11 as in the example of Figure 4, it is suppressed from being erroneously determined that slip has occurred, while when there is slip of the wheel 11 as in the example of Figure 5, it is appropriately determined that slip has occurred.

The slip determination unit 121 may change the time change threshold and duration threshold used in the slip determination in accordance with the vehicle speed, etc. In this case, the slip determination unit 121 changes the time change threshold and duration threshold so that the relationship shown in FIG. 6 is satisfied. In this case, the slip determination unit 121 performs the slip determination using the duration threshold at the point in time when the time change in the motor rotation speed exceeds the time change threshold.

Figure 7 is a diagram showing an example of the transition of the motor rotation speed and the amount of change in the motor rotation speed over time when going over a step. In the example of Figure 7, at time t4, the vehicle 1 begins to go over the step, and a large change in the motor rotation speed over time occurs. Therefore, the slip determination unit 121 may erroneously determine that slippage of the wheel 11 has occurred in the slip determination. In order to prevent erroneous determination in the slip determination, it is possible to make the determination condition for the slip determination stricter so that it is less likely to be determined that slippage has occurred. For example, it is possible to make the duration threshold larger compared to the case where the time change threshold and the duration threshold satisfy the relationship shown in Figure 6. However, as a result, even if slippage has actually occurred, it may be determined that slippage has not occurred, and slip suppression control may not be executed.

Therefore, in order to solve the above problem and appropriately execute slip suppression control depending on whether or not slippage of the wheel 11 occurs, following step S101 in FIG. 3, in step S102, the step-crossing determination unit 122 executes a step-crossing determination.

Figure 8 is a flowchart showing a first example of the flow of the step-crossing determination process among the processes performed by the control device 100. The flowchart in Figure 8 is an example of the process in step S102 in Figure 3. Specifically, the flowchart in Figure 8 is an example of the step-crossing determination process performed in the current processing cycle when it was determined in the step-crossing determination in the previous processing cycle of the flowchart in Figure 3 that the vehicle 1 is not crossing a step.

When the control flow shown in FIG. 8 is started, first, in step S201, the step-crossing determination unit 122 determines whether or not a time change of the motor rotation speed that is equal to or greater than a predetermined amount of change has occurred. Note that in this specification, a time change of the motor rotation speed that is equal to or greater than a predetermined amount of change means a time change of the motor rotation speed in which the time change of the motor rotation speed is equal to or greater than the predetermined amount of change.

As described above, when the vehicle 1 goes over a step, a large change in the motor rotation speed occurs over time. The predetermined change amount in step S201 is set to a value that indicates the possibility that the vehicle 1 is going over a step. In other words, if a change in the motor rotation speed over time that is greater than or equal to the predetermined change amount occurs, it can be determined that the vehicle 1 is likely going over a step. On the other hand, if a change in the motor rotation speed over time that is greater than or equal to the predetermined change amount does not occur, it can be determined that there is no possibility that the vehicle 1 is going over a step (step S204).

If it is determined in step S201 that a change in motor rotation speed over time of a predetermined amount or more has occurred (step S201/YES), the step-crossing determination unit 122 proceeds to step S202. On the other hand, if it is determined in step S201 that a change in motor rotation speed over time of a predetermined amount or more has not occurred (step S201/NO), the step-crossing determination unit 122 proceeds to step S204, determines that the vehicle 1 is not crossing a step, and ends the control flow shown in FIG. 8.

If step S201 returns YES, then in step S202, the step-crossing determination unit 122 determines whether the direction of change over time in the motor rotation speed is a deceleration direction. The determination process in step S202 is a process for determining whether the large change over time in the motor rotation speed is due to crossing a step or due to the occurrence of slippage of the wheel 11.

As in the example of Figure 7, when a large change in motor rotation speed over time is due to going over a step, the direction of the change in motor rotation speed over time is the deceleration direction. In other words, the amount of change in motor rotation speed over time becomes a negative value, and the motor rotation speed decreases. Therefore, when the direction of the change in motor rotation speed over time is the deceleration direction, it can be determined that the vehicle 1 is going over a step.

On the other hand, as in the example of Figure 5, if a large change in the motor rotation speed over time is due to slippage of the wheels 11, the direction of the change in the motor rotation speed over time will be the acceleration direction. In other words, the amount of change in the motor rotation speed over time will be a positive value, and the motor rotation speed will increase. Therefore, if the direction of the change in the motor rotation speed over time is not the deceleration direction, it can be determined that the vehicle 1 is not climbing over a step, and that slippage of the wheels 11 is occurring.

If it is determined in step S202 that the direction of change in the motor rotation speed over time is the deceleration direction (step S202/YES), the step-crossing determination unit 122 proceeds to step S203, determines that the vehicle 1 is crossing a step, and ends the control flow shown in FIG. 8. On the other hand, if it is determined in step S202 that the direction of change in the motor rotation speed over time is not the deceleration direction (step S202/NO), the step-crossing determination unit 122 proceeds to step S204, determines that the vehicle 1 is not crossing a step, and ends the control flow shown in FIG. 8.

Figure 9 is a flowchart showing a second example of the flow of the step-crossing determination process among the processes performed by the control device 100. The flowchart in Figure 9 is an example of the process in step S102 in Figure 3. Specifically, the flowchart in Figure 9 is an example of the step-crossing determination process performed in the current processing cycle when it was determined in the step-crossing determination in the previous processing cycle of the flowchart in Figure 3 that the vehicle 1 is not crossing a step.

When the control flow shown in FIG. 9 is started, first, in step S301, the step-crossing determination unit 122 determines whether or not a time change of the motor rotation speed that is equal to or greater than a predetermined change amount has occurred. Note that the predetermined change amount in step S301 is the same as the predetermined change amount in step S201 in FIG. 8.

If it is determined in step S301 that a change in motor rotation speed over time of a predetermined amount or more has occurred (step S301/YES), the step-crossing determination unit 122 proceeds to step S302. On the other hand, if it is determined in step S301 that a change in motor rotation speed over time of a predetermined amount or more has not occurred (step S301/NO), the step-crossing determination unit 122 proceeds to step S304, determines that the vehicle 1 is not crossing a step, and ends the control flow shown in FIG. 9.

If step S301 returns YES, then in step S302, the step-crossing determination unit 122 determines whether or not a time change of a predetermined amount or more has occurred in the rotation speed of both the front-wheel drive motor 15f and the rear-wheel drive motor 15r. The determination process in step S302 is similar to step S202 in FIG. 8 and is a process for determining whether a large time change in the motor rotation speed is due to crossing a step or due to the occurrence of slippage of the wheels 11.

When a large change in motor rotation speed over time is due to going over a step, the change in motor rotation speed over time occurs due to an impact on the vehicle body. Therefore, a change in rotation speed over time of more than a predetermined amount occurs in both the front-wheel drive motor 15f and the rear-wheel drive motor 15r. Therefore, when a change in rotation speed over time of more than a predetermined amount occurs in both the front-wheel drive motor 15f and the rear-wheel drive motor 15r, it can be determined that the vehicle 1 is going over a step.

On the other hand, if a large change in motor rotation speed over time is due to slippage of the wheels 11, then basically only one of the front-wheel drive motor 15f and the rear-wheel drive motor 15r will experience a change in rotation speed over time that is greater than or equal to a predetermined amount. Therefore, if neither the front-wheel drive motor 15f nor the rear-wheel drive motor 15r experience a change in rotation speed over time that is greater than or equal to a predetermined amount, it can be determined that the vehicle 1 is not climbing over a step, and that the wheels 11 are slipping.

For example, when the vehicle 1 enters a low μ road in the front-wheel drive mode and the wheels 11 slip, only the front-wheel drive motor 15f connected to the front wheels 11a and 11b, which are the drive wheels, causes a time change of more than a predetermined amount of change in the rotation speed. Also, for example, when the vehicle 1 enters a low μ road in the rear-wheel drive mode and the wheels 11 slip, only the rear-wheel drive motor 15r connected to the rear wheels 11c and 11d, which are the drive wheels, causes a time change of more than a predetermined amount of change in the rotation speed. Also, for example, when the vehicle 1 enters a low μ road in the four-wheel drive mode and the wheels 11 slip, the front wheels 11a and 11b slip before the rear wheels 11c and 11d, so a situation arises in which only the front-wheel drive motor 15f causes a time change of more than a predetermined amount of change in the rotation speed.

When the vehicle 1 parked on a low μ road starts in four-wheel drive mode, the front wheels 11a, 11b and the rear wheels 11c, 11d slip simultaneously, causing a time change in the rotation speed of both the front wheel drive motor 15f and the rear wheel drive motor 15r to be greater than or equal to a predetermined change. Therefore, in this situation, from the viewpoint of accurately determining whether the vehicle is passing over a step, it is preferable to perform the processing of the first example shown in FIG. 8.

If it is determined in step S302 that a time change of the rotation speed of the front-wheel drive motor 15f and the rear-wheel drive motor 15r has occurred at a rate equal to or greater than the predetermined rate (step S302/YES), the step-crossing determination unit 122 proceeds to step S303, determines that the vehicle 1 is crossing a step, and ends the control flow shown in FIG. 9. On the other hand, if it is determined in step S302 that a time change of the rotation speed of the front-wheel drive motor 15f and the rear-wheel drive motor 15r has not occurred at a rate equal to or greater than the predetermined rate (step S302/NO), the step-crossing determination unit 122 proceeds to step S304, determines that the vehicle 1 is not crossing a step, and ends the control flow shown in FIG. 9.

Note that if the drive mode is four-wheel drive mode and step S302 in the previous processing cycle was judged as NO, when step S302 in the current processing cycle is judged as YES, both the front wheels 11a, 11b and the rear wheels 11c, 11d may be slipping, so the step-crossing judgment unit 122 may judge that the vehicle 1 is not crossing a step.

Figure 10 is a flowchart showing an example of the flow of the step-crossing determination process performed in the current processing cycle of the control device 100 when the step-crossing determination in the previous processing cycle of the flowchart in Figure 3 indicates that the vehicle 1 is crossing a step. The flowchart in Figure 10 is an example of the process in step S102 in Figure 3.

When the control flow shown in FIG. 10 is started, first, in step S401, the step-over-judgment unit 122 judges whether the time change in the motor rotation speed has fallen below the time change threshold. Specifically, the step-over-judgment unit 122 judges whether the time change in the motor rotation speed of both the front-wheel drive motor 15f and the rear-wheel drive motor 15r has fallen below the time change threshold.

If it is determined that the time change in the motor rotation speed falls below the time change threshold (step S401/YES), the step-crossing determination unit 122 proceeds to step S402, determines that the vehicle 1 has finished crossing the step, and ends the control flow shown in FIG. 10. On the other hand, if it is determined that the time change in the motor rotation speed is not below the time change threshold (step S401/NO), the step-crossing determination unit 122 proceeds to step S403, determines that the vehicle 1 is crossing the step, and ends the control flow shown in FIG. 10.

After vehicle 1 starts to go over the step, while going over the step, the amount of change in motor rotation speed over time converges to the value before going over the step. For example, in the example of FIG. 7, after time t4 when vehicle 1 starts to go over the step, the amount of change in motor rotation speed over time changes so as to converge to the value before time t4. Here, the amount of change in motor rotation speed over time before going over the step is basically smaller than the time change threshold. Therefore, if the amount of change in motor rotation speed over time falls below the time change threshold after vehicle 1 starts to go over the step, it can be determined that vehicle 1 has finished going over the step.

After step S102 in FIG. 3, in step S103, the determination unit 120 determines whether or not the step-crossing determination has determined that the vehicle 1 is crossing a step. If the step-crossing determination has determined that the vehicle 1 is crossing a step (step S103/YES), the control device 100 ends the control flow shown in FIG. 3. If the step-crossing determination has determined that the vehicle 1 is not crossing a step (step S103/NO), the control device 100 proceeds to step S104.

If the result of the determination in step S103 is NO, in step S104, the determination unit 120 determines whether or not the slip determination has determined that slip has occurred. If the slip determination has determined that slip has not occurred (step S104/NO), the control device 100 ends the control flow shown in FIG. 3. If the result of the slip determination has determined that slip has occurred (step S104/YES), the control device 100 proceeds to step S105, where the control unit 130 executes slip suppression control. Note that the control device 100 ends the slip suppression control when a predetermined end condition is satisfied, and ends the control flow shown in FIG. 3.

In step S105, the control unit 130 executes slip suppression control for the wheel 11 that is determined to be slipping. For example, if the slip determination determines that the front wheels 11a, 11b are slipping, the control unit 130 executes slip suppression control for the front wheels 11a, 11b. Also, for example, if the slip determination determines that the rear wheels 11c, 11d are slipping, the control unit 130 executes slip suppression control for the rear wheels 11c, 11d.

As described above, when it is determined that the vehicle 1 is not going over a step, the control unit 130 performs slip suppression control in accordance with the determination result by the slip determination unit 121, and when it is determined that the vehicle 1 is going over a step, the control unit 130 does not perform slip suppression control. This prevents the vehicle 1 from erroneously determining that slippage of the wheel 11 is occurring when the vehicle 1 is going over a step, without making the determination conditions for slip determination stricter. It also prevents the occurrence of a situation in which it is erroneously determined that slippage is not occurring when slippage is actually occurring, and slip suppression control is not executed.

In the above, an example has been described in which the slip determination process in step S101 is followed by the step-crossing determination process in step S102, but the control flow performed by the control device 100 is not limited to this example. For example, the step-crossing determination process in step S102 may be performed before the slip determination process in step S101 in the flowchart of FIG. 3. In this case, the determination unit 120 may not perform a slip determination when it is determined in the step-crossing determination that the vehicle 1 is crossing a step. Also, for example, the slip determination process in step S101 and the step-crossing determination process in step S102 in the flowchart of FIG. 3 may be performed in parallel.

<Effects of the control device>
Next, the effects of the control device 100 according to the embodiment of the present invention will be described.

In the control device 100 according to this embodiment, the control unit 130 performs slip suppression control in accordance with the judgment result by the slip judgment unit 121 when it is judged that the vehicle 1 is not going over a step, and does not perform slip suppression control when it is judged that the vehicle 1 is going over a step. This prevents the vehicle 1 from erroneously judging that the wheel 11 is slipping when the vehicle 1 is going over a step, and prevents the vehicle 1 from erroneously judging that the wheel 11 is not slipping when the wheel 11 is actually slipping. Therefore, the slip suppression control can be appropriately executed depending on whether the wheel 11 is slipping or not.

In addition, in the control device 100 according to this embodiment, it is preferable that the step-crossing determination unit 122 determines that the vehicle 1 is crossing a step when a time change of the rotation speed of the drive motor 15 occurs that is equal to or greater than a predetermined change amount, and the direction of the time change of the rotation speed of the drive motor 15 is the deceleration direction. This makes it possible to appropriately determine whether a large time change in the motor rotation speed is due to crossing a step or due to the occurrence of slippage of the wheels 11, by focusing on the direction of the time change in the motor rotation speed. Therefore, the step-crossing determination can be performed with high accuracy.

In addition, in the control device 100 according to this embodiment, it is preferable that the step-crossing determination unit 122 determines that the vehicle 1 is crossing a step when a time change in rotation speed that is greater than or equal to a predetermined amount occurs in both the front-wheel drive motor 15f and the rear-wheel drive motor 15r. This makes it possible to appropriately determine whether a large time change in the motor rotation speed is due to crossing a step or due to the occurrence of slippage of the wheels 11, by focusing on which drive motor 15 has experienced a time change in rotation speed that is greater than or equal to a predetermined amount. Therefore, step-crossing determination can be performed with high accuracy.

In addition, in the control device 100 according to this embodiment, it is preferable that the slip determination unit 121 determines that slippage of the wheel 11 has occurred when the state in which the time change in the rotation speed of the drive motor 15 is equal to or greater than the time change threshold continues for equal to or greater than the duration threshold. This allows for accurate slip determination. For example, it is possible to appropriately determine that slippage has occurred when slippage of the wheel 11 has occurred as in the example of FIG. 5, while suppressing erroneous determination that slippage has occurred when slippage of the wheel 11 has occurred as in the example of FIG. 4.

In addition, in the control device 100 according to this embodiment, it is preferable that the step-crossing determination unit 122 determines that the vehicle 1 is crossing a step, and then determines that the vehicle 1 has finished crossing the step if the time change in the rotation speed of the drive motor 15 falls below the time change threshold. This makes it possible to accurately determine whether the vehicle 1 has finished crossing the step.

The above describes a preferred embodiment of the present invention with reference to the attached drawings, but it goes without saying that the present invention is not limited to the above-mentioned embodiment, and various modifications and alterations within the scope of the claims also fall within the technical scope of the present invention.

For example, the configuration of vehicle 1 has been described above with reference to FIG. 1, but the configuration of the vehicle according to the present invention is not limited to such an example. The vehicle according to the present invention may be, for example, a vehicle in which some components have been removed, added, or modified from vehicle 1 shown in FIG. 1. Furthermore, the vehicle according to the present invention may be, for example, a vehicle in which a drive motor 15 is provided for each wheel 11.

In addition, for example, the processes described in this specification using flowcharts do not necessarily have to be performed in the order shown in the flowcharts. In addition, additional processing steps may be employed, and some processing steps may be omitted.

The present invention can be used in control devices.

Reference Signs List 1 Vehicle 11 Wheel 13f Front differential device 13r Rear differential device 15 Drive motor 17 Inverter 19 Battery 21 Motor rotation speed sensor 100 Control device 110 Acquisition unit 120 Determination unit 121 Slip determination unit 122 Step passing determination unit 130 Control unit

Claims (4)

a slip determination unit that determines whether or not slippage has occurred in the vehicle wheels based on a time change in the rotation speed of the drive motor;
a step-crossing determination unit that determines whether the vehicle is crossing a step;
a control unit that performs slip suppression control in accordance with a determination result by the slip determination unit when it is determined that the vehicle is not climbing over a step, and does not perform the slip suppression control when it is determined that the vehicle is climbing over a step;
Equipped with
the drive motor includes a front-wheel drive motor capable of outputting power to drive front wheels, and a rear-wheel drive motor capable of outputting power to drive rear wheels,
the step-crossing determination unit determines that the vehicle is crossing a step when, during traveling of the vehicle, a time change in rotation speed of at least a predetermined amount of change occurs in both the front-wheel drive motor and the rear-wheel drive motor without a situation in which a time change in rotation speed of at least a predetermined amount of change occurs in only one of the front-wheel drive motor and the rear-wheel drive motor.
Control device. the step-crossing determination unit determines that the vehicle is crossing a step when a time change of the rotation speed of the drive motor occurs at a predetermined change amount or more and the time change of the rotation speed of the drive motor is in a deceleration direction.
The control device according to claim 1 . the slip determination unit determines that slip of the wheel has occurred when a state in which a time change amount of the rotation speed of the drive motor is equal to or greater than a time change amount threshold continues for a duration threshold or longer.
The control device according to claim 1 or 2 . the step-crossing determination unit determines that the vehicle has finished crossing the step when a time-varying amount of change in the rotation speed of the drive motor falls below the time-varying amount threshold after determining that the vehicle is crossing the step;
The control device according to claim 3 .

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