JP7569082B2 - Vehicle steering system control device and steer-by-wire system equipped with the same - Google Patents

Description

The present invention relates to a control device for a vehicle steering system such as a steer-by-wire (SBW) system in which the steering mechanism and the turning mechanism are mechanically separated, and in particular to a control device for a vehicle steering system that controls a steering mechanism having a steering end point that is the limit of steerable operation, and an SBW system equipped with the same.

One type of vehicle steering system is the steer-by-wire (SBW) system, in which the steering mechanism having a steering wheel operated by the driver and the steering mechanism that steers the steered wheels are mechanically separated. In the SBW system, the operation of the steering wheel is transmitted to the steering mechanism by an electric signal to steer the steered wheels, and the steering mechanism generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates the steering reaction force by a reaction actuator equipped with a reaction motor, and the steering mechanism steers the steered wheels by a steering actuator equipped with a steering motor. The reaction actuator and the steering wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction actuator is transmitted to the driver via the column shaft and the steering wheel.

In the SBW system, a steering end point that is the limit of steering is provided in the steering mechanism, and an upper limit is set for the steering angle of the steering wheel. This is for the purpose of avoiding problems caused by cables when various electrical components are installed in the steering wheel and connected to a controller fixed to the vehicle with cables. For example, Japanese Patent Application Laid-Open No. 2016-30521 (Patent Document 1) proposes a vehicle steering device equipped with a rotation limiting mechanism that includes a guide ball that is movable by being sandwiched between both grooves, and a first plate having a first groove that has a semicircular cross section recessed in the axial direction of the steering shaft and is formed in a linear shape in the radial direction of the steering shaft, and a second plate having a semicircular cross section recessed in the axial direction of the steering shaft and is formed in a spiral shape in a plan view, which are overlapped. An inner diameter side regulating member and an outer diameter side regulating member are arranged on both sides of the guide ball along the first groove. The first plate rotates together with the steering shaft, and the second plate does not rotate, so when the steering components rotate and the first plate rotates together with the steering shaft, the guide ball moves along the second groove and also moves radially along the first groove of the steering shaft. When the guide ball comes into contact with the end of the inner diameter side regulating member or the end of the outer diameter side regulating member, the movement of the guide ball is restricted, and the rotation of the steering components is also restricted.

As described above, the steering mechanism in the SBW system generates a steering reaction force by supplying an electric current to a reaction force actuator. For example, in Japanese Patent Publication No. 5867612 (Patent Document 2), the steering reaction force is generated according to the steering state, such as the steering angle of the steered wheels.

JP 2016-30521 A Patent No. 5867612

However, in the case of an SBW system in which a steering end point is provided in the steering mechanism, when the steering wheel is steered up to the steering end point, the steering wheel operation is suppressed by the steering end point. In other words, the repulsive force from the steering end point acts as a reaction force against the steering wheel, so a steering reaction force from the reaction force actuator is not particularly necessary. In other words, if the reaction force actuator continues to generate a reaction force even after the steering end point is reached, an unnecessary load is placed on the reaction force actuator, power consumption increases, and there is a risk of malfunction such as heat generation.

The present invention was made in light of the above-mentioned circumstances, and the object of the present invention is to provide a control device for a vehicle steering system that can suppress increases in power consumption and heat generation in a reaction force actuator when the vehicle is steered to the end of the steering range, and an SBW system equipped with the same.

The present invention relates to a control device for a vehicle steering system that has a steering end point that is the limit of steering possible, and controls the drive of a reaction force actuator by adjusting the supplied current to control a steering mechanism. The above object of the present invention is achieved by providing an end contact determination unit that uses steering-related information detected in the steering mechanism to determine whether the steering state is an end contact ON state in which the steering is performed to the steering end point, or an end contact OFF state in which the steering is not performed to the steering end point, and the end contact determination unit determines the steering state using a first threshold value for determining whether the steering state has become the end contact ON state and a second threshold value for determining whether the steering state has become the end contact OFF state, which are set for the steering-related information, and the second threshold value is set to a range of values of the steering-related information in which it is not determined that the steering state has become the end contact ON state by the determination based on the first threshold value, and when the steering state is the end contact ON state, the control information that is the basis for adjusting the current is reduced in order to reduce the current.

The above object of the present invention is to increase the control information when the steering state is the end contact OFF state in order to restore the reduced current, or to have the end contact determination unit have a gain that decreases over time when the steering state is the end contact ON state and multiply the control information by the gain, or to have the end contact determination unit have a gain that decreases over time when the steering state is the end contact ON state and increases over time when the steering state is the end contact OFF state and multiply the control information by the gain, or to have the end contact determination unit use a steering angle as the steering-related information, and determine that the steering state has become the end contact ON state when the magnitude of the steering angle is equal to or greater than a first steering angle threshold, and determine that the steering state has become the end contact OFF state when the magnitude of the steering angle is smaller than a second steering angle threshold that is smaller than the first steering angle threshold. By this, or when the end contact determination unit further uses a steering angular velocity as the steering related information, and further satisfies a condition that the magnitude of the steering angular velocity is equal to or less than a first steering angular velocity threshold, it determines that the steering state has become the end contact ON state, and when the magnitude of the steering angular velocity is greater than a second steering angular velocity threshold that is greater than the first steering angular velocity threshold, it also satisfies a condition that the steering state has become the end contact OFF state, or when the end contact determination unit further uses a steering angular velocity as the steering related information, When a condition that the magnitude of the steering torque is equal to or greater than a first steering torque threshold is further satisfied, the steering state is determined to be in the end contact ON state, and when a condition that the magnitude of the steering torque is smaller than a second steering torque threshold which is smaller than the first steering torque threshold is satisfied, the steering state is determined to be in the end contact OFF state, or the end contact determination unit uses a steering torque as the steering-related information and determines that the magnitude of the steering torque is equal to or greater than a first steering torque threshold. When the condition that the magnitude of the steering torque is smaller than a second steering torque threshold value that is smaller than the first steering torque threshold value is satisfied, the steering state is determined to be in the end contact OFF state by determining that the steering state has become the end contact ON state, or when the end contact determination unit further uses a steering angular velocity as the steering-related information and further satisfies a condition that the magnitude of the steering angular velocity is equal to or smaller than a first steering angular velocity threshold value, the steering state is determined to be in the end contact ON state. When the condition that the magnitude of the steering angular velocity is greater than a second steering angular velocity threshold value that is greater than the first steering angular velocity threshold value is satisfied, the steering state is determined to be in the end contact OFF state, or when the end contact determination unit further uses the current as the steering-related information and further satisfies the condition that the magnitude of the current is equal to or greater than a first current threshold value, the steering state is determined to be in the end contact ON state, and when the condition that the magnitude of the current is smaller than a second current threshold value that is smaller than the first current threshold value is satisfied, the end contact determination unit further uses the current as the steering-related information and further satisfies the condition that the magnitude of the current is equal to or greater than a first current threshold value. a target steering torque generating unit that generates a target steering torque, a conversion unit that converts the target steering torque into a target torsion angle, and a current command that is a target value of the current so as to make the torsion angle of a torsion bar of the steering mechanism follow the target torsion angle. This is more effectively achieved by further comprising a torsion angle control unit that calculates a value and using the target steering torque as the control information, or by further comprising a target steering torque generation unit that generates a target steering torque, a conversion unit that converts the target steering torque into a target torsion angle, and a torsion angle control unit that calculates a current command value, which is a target value of the current, so that the torsion angle of the torsion bar of the steering mechanism follows the target torsion angle, and using the current command value as the control information.

Alternatively, the above object of the present invention is achieved by decreasing the current after the magnitude of the steering torque remains equal to or greater than a first steering torque threshold for a first predetermined time, and then increasing the current after the magnitude of the steering torque remains smaller than a second steering torque threshold, which is smaller than the first steering torque threshold, for a second predetermined time after the current has been decreased.

Alternatively, the above object of the present invention is achieved by decreasing the current after the steering angle continues to be equal to or greater than a first steering angle threshold for a first predetermined time, and then increasing the current after the steering angle continues to be smaller than a second steering angle threshold, which is smaller than the first steering angle threshold, for a second predetermined time after decreasing the current.

The above object of the present invention is more effectively achieved by the steering mechanism having an elastic body or a torsion bar between the handle and the reaction actuator.

Furthermore, the above object of the present invention is achieved by a steer-by-wire system including a control device for the above vehicle steering system and the steering mechanism controlled by the control device.

The control device for the vehicle steering system of the present invention determines the steering state, and when the steering state is a state where the steering has been completed to the steering end (end contact ON state), measures are taken to reduce the current supplied to the reaction actuator, thereby suppressing the increase in power consumption and heat generation in the reaction actuator.

In addition, by differentiating the threshold value for determining whether the steering state has reached the end contact ON state from the threshold value for determining whether the steering state has reached the state where steering has not reached the steering end (end contact OFF state), it is possible to suppress the hunting phenomenon at the threshold boundary.

1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to the present invention; FIG. 4 is a structural diagram showing an example of the arrangement of various sensors on a column shaft. 1 is a block diagram showing a configuration example (first embodiment) of the present invention; 4 is a block diagram showing an example of the configuration of a target steering torque generating unit; FIG. 4A and 4B are diagrams illustrating an example of the configuration of a base map section and an example of characteristics of a base map. FIG. 4 is a diagram showing an example of a characteristic of a damper gain map. FIG. 2 is a block diagram showing a configuration example (first embodiment) of an end contact determination unit; 11A and 11B are diagrams illustrating changes in steering state when a first steering angle threshold and a second steering angle threshold are set. 11A and 11B are diagrams illustrating an image of changes over time in the steering angle and the motor current value when end contact determination is performed using the same threshold value and different threshold values. FIG. 4 is a block diagram showing a configuration example of a torsion angle control unit. 4 is a block diagram showing an example of the configuration of a target steering angle generating unit; FIG. 13 is a diagram showing an example of setting upper and lower limit values in a limiting section. FIG. 4 is a flowchart showing an operation example (first embodiment) of the present invention. 5 is a flowchart showing an example of the operation of a target steering torque generating unit. 5 is a flowchart showing an operation example (first embodiment) of an end contact determination unit. 5 is a flowchart showing an example of the operation of a target steering angle generating unit. 10 is a flowchart showing a modified example of the operation of the steering state determination unit. FIG. 13 is a block diagram showing a configuration example (second embodiment) of an end contact determination unit. FIG. 13 is a block diagram showing a configuration example (third embodiment) of an end contact determination unit. FIG. 13 is a block diagram showing a configuration example (fourth embodiment) of an end contact determination unit. 13 is a flowchart showing an operation example (fifth embodiment) of a steering state determination unit. FIG. 13 is a block diagram showing an example of the configuration of a reaction force control system (sixth embodiment). 13 is a flowchart showing a part of an operation example (sixth embodiment) of a reaction force control system.

The present invention uses steering-related information such as steering angle and steering torque detected in the steering mechanism to automatically determine when the steering state has reached the steering end, which is the limit of possible steering (end stop ON state), and in order to reduce the current supplied to the reaction actuator in the end stop ON state, it reduces intermediate data (control information) that is the basis for adjusting the current and is calculated before determining the current value. This reduces the current supplied, making it possible to suppress increases in power consumption and heat generation in the reaction actuator in the end stop ON state. Reducing power consumption leads to climate change countermeasures by reducing the environmental load, and to reducing the load on the global environment. The target steering torque, etc. can be used as control information.

In addition, in the present invention, the threshold value (first threshold value) for determining whether the steering state has become the end contact ON state and the threshold value (second threshold value) for determining whether the steering state has become the state where the steering has not been performed to the steering end (end contact OFF state) are different values. For example, when the steering angle is used as the steering-related information to perform the determination, the first threshold value is set to a value greater than the second threshold value. If the same value is used for the first threshold value and the second threshold value, when the steering-related information fluctuates at the threshold boundary, a hunting phenomenon occurs in which the steering state frequently switches between the end contact ON state and the end contact OFF state. The occurrence of the hunting phenomenon causes the current supplied to the reaction force actuator to become unstable, which may affect the steering reaction force and cause discomfort to the driver. By using different values for the first threshold value and the second threshold value, the hunting phenomenon at the threshold boundary can be suppressed.

Below, an embodiment of the present invention will be described with reference to the drawings.

First, we will explain an example of the configuration of a steer-by-wire (SBW) system equipped with a control device according to the present invention.

Figure 1 shows an example of the configuration of an SBW system. The SBW system comprises a reaction device 30 constituting a steering mechanism having a steering wheel operated by the driver, a steering device 40 constituting a steering mechanism that steers the steered wheels, and a control device 50 that controls both devices. The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft (steering shaft, handle shaft) 2, which is provided in general electric power steering devices, and transmits the operation of the steering wheel 1 by the driver as an electrical signal, specifically the steering angle θh output from the reaction device 30, as an electrical signal.

The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotational speed of the reaction force motor 31, and transmits the vehicle's motion state transmitted from the steered wheels 5L, 5R to the driver as a reaction force (torque) generated by the reaction force motor 31. The reaction force device 30 further includes a steering angle sensor 33 and an angle sensor 34 that are provided on the column shaft 2. The steering angle sensor 33 and the angle sensor 34 are specifically disposed on the column shaft 2 as shown in Fig. 2. That is, the steering angle sensor 33 is provided on the upper part of the column shaft 2, and detects the steering angle θh. A torsion bar 2A is inserted in the column shaft 2, and an upper angle sensor 34A is provided on the steering wheel 1 side of the column shaft 2 with the torsion bar 2A in between, and a lower angle sensor 34B is provided on the opposite side of the column shaft 2 to the steering wheel 1 with the torsion bar 2A in between, as angle sensors 34, the upper angle sensor 34A detecting a steering wheel angle θ ₁ , and the lower angle sensor 34B detecting a column angle θ _2. The steering wheel angle θ ₁ and the column angle θ ₂ are input to a torsion angle calculation unit 36, which calculates a torsion angle Δθ of the torsion bar by the following equation 1.

なお、磁歪式や光学式等の公知のセンサを用いて、捩れ角Δθを直接求めても良い。

The torsional angle Δθ may be directly obtained using a known sensor such as a magnetostrictive sensor or an optical sensor.

The column shaft 2 is equipped with a stopper 35 that physically sets the steering end point, which is the limit of possible steering. The steering angle θh when the steering is performed to the steering end point becomes the limit value of the magnitude (absolute value) of the steering angle θh (hereinafter referred to as the "end angle"). For example, a rotation limiting mechanism described in Patent Document 1 is used as the stopper 35. Note that the reaction force actuator is composed of a reaction force motor 31, a reduction mechanism 32, etc., but sometimes only the reaction force motor 31 is called the reaction force actuator.

The steering device 40 includes a steering motor 41, a speed reduction mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 44 that converts rotational motion into linear motion. The steering motor 41 is driven in accordance with changes in the steering angle θh, and the driving force is applied to the pinion rack mechanism 44 via the speed reduction mechanism 42, and the steered wheels 5L, 5R are steered via the tie rods 3a, 3b. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steered wheels 5L, 5R. The motor angle of the steering motor 41, the rack position, etc. may be used as the steering angle θt.

In order to cooperatively control the reaction force device 30 and the turning device 40, the control device 50 generates a voltage control command value Vref1 for driving and controlling the reaction force motor 31 and a voltage control command value Vref2 for driving and controlling the turning motor 41 based on information such as the steering angle θh and turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10. The control device 50 is supplied with power from the battery 12 and receives an ignition key signal via the ignition key 11. In addition, the control device 50 is connected to a CAN (Controller Area Network) 20 that transmits and receives various vehicle information, and the vehicle speed Vs can also be received from the CAN 20. In addition, the control device 50 can also be connected to a non-CAN 21 that transmits and receives communications other than the CAN 20, analog/digital signals, radio waves, etc.

The control device 50 has a CPU (including MCU, MPU, etc.), and the cooperative control of the reaction device 30 and the steering device 40 is mainly executed by a program inside the CPU. An example of the configuration for performing the control (first embodiment) is shown in FIG. 3. In FIG. 3, the reaction device 30 is equipped with a reaction motor 31, a steering angle sensor 33, an angle sensor 34, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39, the steering device 40 is equipped with a steering motor 41, an angle sensor 43, a PWM control unit 47, an inverter 48, and a motor current detector 49, and the other components are realized by the control device 50. Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may be equipped with a RAM (random access memory), a ROM (read only memory), etc. to store data, programs, etc. The control device 50 may also include some or all of the PWM control unit 37, the inverter 38, the motor current detector 39, the PWM control unit 47, the inverter 48, and the motor current detector 49.

The control device 50 has a configuration for controlling the reaction device 30 (hereinafter referred to as the "reaction control system") and a configuration for controlling the steering device 40 (hereinafter referred to as the "steering control system"). The reaction control system 60 and the steering control system 70 cooperate to control the reaction device 30 and the steering device 40.

The reaction force control system 60 includes a target steering torque generation unit 100, an end contact judgment unit 200, a conversion unit 300, a torsion angle control unit 400, a current control unit 500, a multiplication unit 510, and a subtraction unit 520, and performs control so that the torsion angle of the torsion bar 2A follows the target torsion angle. In addition, the target steering torque is used as control information. The target steering torque generation unit 100 generates a target steering torque TrefA based on the steering angle θh and the vehicle speed Vs, the end contact judgment unit 200 determines the end contact judgment gain Ge based on the judgment of the steering state, and the target steering torque Tref, which is the result of multiplying the target steering torque TrefA by the end contact judgment gain Ge, is converted to a target torsion angle Δθref by the conversion unit 300. The target torsion angle Δθref is input to the torsion angle control unit 400 together with the torsion angle Δθ, and the torsion angle control unit 400 calculates a current command value Imc such that the torsion angle Δθ becomes the target torsion angle Δθref. Then, a subtraction unit 520 calculates a deviation I1 (=Imc-Imr) between the current command value Imc and the current value (motor current value) Imr of the reaction force motor 41 detected by the motor current detector 39, and the current control unit 500 determines a voltage control command value Vref1 based on the deviation I1. In the reaction force device 30, the reaction force motor 31 is driven and controlled via the PWM control unit 37 and the inverter 38 based on the voltage control command value Vref1.

A configuration example of the target steering torque generation unit 100 is shown in FIG. 4. The target steering torque generation unit 100 includes a base map unit 110, a differentiation unit 120, a damper gain unit 130, a multiplication unit 140, and an addition unit 150. The steering angle θh is input to the base map unit 110 and the differentiation unit 120, and the vehicle speed Vs is input to the base map unit 110 and the damper gain unit 130.

The basic map unit 110 has a basic map, and outputs a torque signal Tref_a using the basic map with the vehicle speed Vs as a parameter. The torque signal Tref_a is used to generate a basic reaction force. The basic map is adjusted by tuning, and for example, as shown in FIG. 5(A), the torque signal Tref_a increases as the magnitude |θh| of the steering angle θh increases, and also increases as the vehicle speed Vs increases. In other words, the reaction force increases as the magnitude |θh| of the steering angle θh increases and as the vehicle speed Vs increases. In addition, in FIG. 5(A), the sign unit 111 outputs the sign (+1, -1) of the steering angle θh to the multiplication unit 112, and the magnitude of the torque signal Tref_a is obtained from the map from the magnitude |θh| of the steering angle θh, and this is multiplied by the sign of the steering angle θh to obtain the torque signal Tref_a. Alternatively, as shown in FIG. 5(B), a map may be constructed according to positive and negative steering angles θh. In this case, the manner of change may be different when the steering angle θh is positive and when it is negative. Also, although the basic map shown in FIG. 5 is vehicle speed sensitive, it does not have to be vehicle speed sensitive.

The differentiation unit 120 differentiates the steering angle θh to calculate the steering angular velocity ωh1, and the steering angular velocity ωh1 is input to the multiplication unit 140. In addition, in the calculation of the steering angular velocity ωh1, a low pass filter (LPF) process may be appropriately performed to reduce the influence of high-frequency noise, or a differentiation operation and LPF process may be performed using a high pass filter (HPF) and a gain. The steering angular velocity ωh1 may be calculated by performing a differentiation operation and LPF process on the handle angle _θ1 detected by the upper angle sensor or the column angle _θ2 detected by the lower angle sensor, instead of the steering angle θh. The motor angular velocity of the steering motor 41 may be used instead of the steering angular velocity ωh1. In this case, the differentiation unit 120 is not necessary.

The damper gain unit 130 outputs a damper gain _DG to be multiplied by the steering angular velocity ωh1. The steering angular velocity ωh1 multiplied by the damper gain _DG by the multiplication unit 140 is input to the addition unit 150 as a torque signal Tref_b. The damper gain _DG is calculated according to the vehicle speed Vs using a vehicle speed-sensitive damper gain map included in the damper gain unit 130. The damper gain map has a characteristic that the damper gain gradually increases as the vehicle speed Vs increases, as shown in FIG. 6, for example. By multiplying the steering angular velocity ωh1 by such a damper gain _DG to compensate for the target steering torque proportional to the steering angular velocity ωh1, a viscous feeling can be given, and when the steering wheel is changed from a turned state to a released state, the steering wheel can be made to have a convergence without oscillation, thereby improving the system stability. The damper gain map may be variable according to the steering angle θh.

The torque signals Tref_a and Tref_b are added in the adder 150, and the result of the addition is output as the target steering torque TrefA.

The end contact determination unit 200 uses the steering angle θh as steering-related information to determine the steering state St and determines the end contact determination gain Ge based on the steering state St. The motor current value Imr of the reaction force motor 41 is adjusted based on the target steering torque Tref obtained by multiplying the target steering torque TrefA by the end contact determination gain Ge. Therefore, by reducing the end contact determination gain Ge in the end contact ON state, the magnitude of the target steering torque Tref also decreases, and ultimately the motor current value Imr can be reduced.

An example of the configuration of the end contact determination unit 200 is shown in FIG. 7. The end contact determination unit 200 includes a steering state determination unit 210 and a gain calculation unit 220. The steering angle θh is input to the steering state determination unit 210.

The steering state determination unit 210 uses the steering angle θh to determine whether the steering state St has reached the end contact ON state (hereinafter referred to as "end contact ON determination") and whether the steering state St has reached the end contact OFF state (hereinafter referred to as "end contact OFF determination"), and outputs the steering state St.

In the end contact ON determination, if the magnitude |θh| of the steering angle θh is equal to or greater than a predetermined threshold (first steering angle threshold) θth1 set in advance, the steering state St is deemed to have entered the end contact ON state, and the "steering state St = end contact ON state" is determined. As the first steering angle threshold θth1, an angle slightly before the terminal angle, for example, an angle 2 degrees before the terminal angle, is used. By setting the first steering angle threshold θth1 before the terminal angle, it is possible to absorb the time lag that may occur between reaching the steering end and the motor current value Imr starting to decrease. The terminal angle may be used as the first steering angle threshold θth1.

In the end contact OFF judgment, if the magnitude |θh| of the steering angle θh is smaller than a predetermined threshold (second steering angle threshold) θth2 set in advance, the steering state St is deemed to have entered the end contact OFF state, and "steering state St = end contact OFF state" is determined. The second steering angle threshold θth2 is set to a range of the magnitude |θh| of the steering angle θh in which it is not determined that the steering state St has entered the end contact ON state in the end contact ON judgment, that is, a range smaller than the first steering angle threshold θth1. In other words, the second steering angle threshold θth2 is set to a value smaller than the first steering angle threshold θth1. For example, an angle 5 degrees before the terminal angle is used as the second steering angle threshold θth2.

When the steering wheel 1 is operated with the first steering angle threshold θth1 and the second steering angle threshold θth2 set in this way, the change in the steering state is as shown in Figure 8. The steering wheel 1 is operated from the neutral position, and the steering state is in the "end stop OFF state" (arrow A) until the magnitude |θh| of the steering angle θh becomes equal to or greater than the first steering angle threshold θth1. When the magnitude |θh| of the steering angle θh becomes equal to or greater than the first steering angle threshold θth1, the steering state becomes the "end stop ON state" (arrow B). Then, the steering wheel 1 is returned, and the steering state remains in the "end stop ON state" (arrow C) until the magnitude |θh| of the steering angle θh becomes smaller than the second steering angle threshold θth2. When the magnitude |θh| of the steering angle θh becomes smaller than the second steering angle threshold θth2, the steering state becomes the "end stop OFF state" (arrow D). Therefore, even if the magnitude |θh| of the steering angle θh becomes smaller than the first steering angle threshold θth1 immediately after the magnitude |θh| of the steering angle θh becomes equal to or larger than the first steering angle threshold θth1 and the steering state becomes the "end contact ON state", the steering state remains in the "end contact ON state". Also, even if the magnitude |θh| of the steering angle θh becomes smaller than the second steering angle threshold θth2 and the steering state becomes the "end contact OFF state", the steering state remains in the "end contact OFF state". In this way, by using the first steering angle threshold θth1 and the second steering angle threshold θth2, it is possible to suppress the hunting phenomenon in which the steering state frequently switches between the end contact ON state and the end contact OFF state even if the magnitude |θh| of the steering angle θh fluctuates at the threshold boundary.

The steering state determination unit 210 performs the end contact ON determination and the end contact OFF determination (hereinafter, these two determinations are collectively referred to as "end contact determination") in the following procedure. First, an end contact ON determination is performed, and if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, "steering state St = end contact ON state" is determined, and if not, an end contact OFF determination is performed. Then, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 in the end contact OFF determination, "steering state St = end contact OFF state" is determined, and if not, that is, if the magnitude |θh| of the steering angle θh is equal to or greater than the second steering angle threshold θth2 and smaller than the first steering angle threshold θth1, the steering state St is not changed.

The gain calculation unit 220 determines the end contact judgment gain Ge based on the steering state St. As described above, in the end contact ON state, the end contact judgment gain Ge is reduced in order to reduce the magnitude of the target steering torque Tref. In the end contact OFF state, the end contact judgment gain Ge is increased in order to return the reduced target steering torque to its original state.

When the steering state St is the "end contact ON state", in order to monotonically decrease the target steering torque by multiplying the end contact judgment gain Ge, the gain calculation unit 220 reduces the end contact judgment gain Ge over time. Specifically, in order to gradually decrease the end contact judgment gain Ge from 1 at a constant rate after the end contact ON state is reached, a constant value FR1 (e.g., 0.2) is subtracted from the immediately preceding end contact judgment gain Ge (hereinafter referred to as the "immediate end contact judgment gain Gep") to obtain a new end contact judgment gain Ge. That is, a new end contact judgment gain Ge is calculated as Ge = Gep - FR1. If the subtracted value is 0 or less, the end contact judgment gain Ge is set to 0. The immediately preceding end contact judgment gain Gep is updated to the newly calculated end contact judgment gain Ge.

When the steering state St is the "end contact OFF state", in order to monotonically increase the target steering torque by multiplying the end contact judgment gain Ge, the gain calculation unit 220 increases the end contact judgment gain Ge over time. Specifically, in order to gradually increase the end contact judgment gain Ge at a constant rate from the end contact OFF state until it becomes 1, a value obtained by adding a constant value FR2 (e.g., 0.2) to the previous end contact judgment gain Gep is set as a new end contact judgment gain Ge. That is, a new end contact judgment gain Ge is calculated as Ge = Gep + FR2. If the added value is 1 or more, the end contact judgment gain Ge is set to 1. The previous end contact judgment gain Gep is updated to the newly calculated end contact judgment gain Ge. Note that the constant values FR1 and FR2 may be the same value or different values.

The end contact judgment gain Ge output from the end contact judgment unit 200 is multiplied by the target steering torque TrefA in the multiplication unit 510, and the multiplication result is output as the target steering torque Tref.

By calculating the target steering torque Tref in this way, the motor current value Imr can be reduced in the end contact ON state, and the hunting phenomenon at the threshold boundary can be suppressed. For example, FIG. 9 is a diagram showing an image of the steering angle θh and the motor current value Imr over time when the steering wheel 1 starts to be turned from the neutral position at time t1, reaches the terminal angle at time t2, and then operates the steering wheel 1 around the threshold set before the terminal angle, and the effect is explained using this diagram. FIG. 9(A) is a diagram in the case where the first steering angle threshold θth1 and the second steering angle threshold θth2 are the same value (written as steering angle threshold), and FIG. 9(B) is a diagram in the case of this embodiment where the first steering angle threshold θth1 and the second steering angle threshold θth2 are different values. When the first steering angle threshold θth1 and the second steering angle threshold θth2 are the same value, as shown in FIG. 9A, when the steering angle θh fluctuates at the steering angle threshold boundary, the steering state alternates between the end contact ON state and the end contact OFF state accordingly, and the motor current value Imr repeatedly increases and decreases. In FIG. 9A, for the sake of convenience, the steering angle θh and the motor current value Imr are displayed overlapping each other. In contrast, when the first steering angle threshold θth1 and the second steering angle threshold θth2 are different values, as shown in FIG. 9B, even if the steering angle θh fluctuates at the first steering angle threshold θth1 boundary (see dashed line), as long as it does not become smaller than the second steering angle threshold θth2, the steering state remains in the end contact ON state, so the motor current value Imr gradually decreases and becomes 0 at time t3 (see solid line).

The minimum value of the end contact judgment gain Ge is set to 0, but any small value may be used as the minimum value. The end contact judgment gain Ge is decreased and increased linearly at a constant rate, but the shape of the change may be any shape as long as the end contact judgment gain Ge is decreased and increased monotonically, for example, it may be curved. The end contact judgment gain Ge may be increased or decreased based on a map or function. Furthermore, when it is determined that the end contact ON state has been reached, the end contact judgment gain Ge may be set to 0 or any small value, and when it is determined that the end contact OFF state has been reached, the end contact judgment gain Ge may be set to 1. In this case, instead of multiplying the target steering torque TrefA by the end contact judgment gain Ge, the target steering torque TrefA may be switched between 0 or any small value using a switch depending on the steering state St, and output as the target steering torque Tref.

The conversion unit 300 has the characteristic of the reciprocal "1/Kt" of the spring constant Kt of the torsion bar 2A, and converts the target steering torque Tref into the target torsion angle Δθref.

The torsion angle control unit 400 inputs the target torsion angle Δθref and the torsion angle Δθ, and calculates the current command value Imc so that the torsion angle Δθ becomes the target torsion angle Δθref. The desired steering reaction force is realized by controlling the torsion angle Δθ to follow a value corresponding to the steering angle θh.

Figure 10 is a block diagram showing an example of the configuration of the torsion angle control unit 400. The torsion angle control unit 400 includes gain units 420, 440, and 470, an integration unit 450, a differentiation unit 460, subtraction units 410 and 480, and an addition unit 430, and calculates the current command value Imc using the target torsion angle Δθref and the torsion angle Δθ by differentiation-first type PID (proportional-integral-differential) control (PI-D control). The target torsion angle Δθref is added and input to the subtraction unit 410, and the torsion angle Δθ is subtracted and input to the subtraction unit 410 and input to the differentiation unit 460.

The subtraction unit 410 calculates the angle deviation dΔθ between the target torsion angle Δθref and the torsion angle Δθ, and the angle deviation dΔθ is input to the gain units 420 and 440. The gain unit 420 multiplies the angle deviation dΔθ by the proportional gain Kp, and the multiplication result is input to the addition unit 430 as the current command value Imc1. The gain unit 440 multiplies the angle deviation dΔθ by the integral gain Ki, and the multiplication result is input to the integration unit 450 and integrated (1/s), and the integration result is input to the addition unit 430 as the current command value Imc2. The addition unit 430 adds the current command values Imc1 and Imc2, and the sum, which is the current command value Imc3, is added and input to the subtraction unit 480. The differentiation unit 460, which receives the torsion angle Δθ, differentiates (s) the torsion angle Δθ, and the differentiation result is input to the gain unit 470 and multiplied by the differentiation gain Kd. The multiplication result is input to the subtraction unit 480 as the current command value Imc4 for subtraction. In the subtraction unit 480, the current command value Imc4 is subtracted from the current command value Imc3, and the subtraction result is output as the current command value Imc.

The control by the torsion angle control unit 400 is not limited to PI-D control, and may be any control that controls the torsion angle Δθ to follow the target torsion angle Δθref, such as commonly used control such as PI (proportional integral) control, P (proportional) control, PID control, IP control (proportional-lead PI control), model matching control, model reference control, etc. Also, a limiter that limits the maximum value of the current command value Imc may be provided downstream of the torsion angle control unit 400.

The current command value Imc is added to the subtraction unit 520, which calculates the deviation I1 from the motor current value Imr that is fed back. The current control unit 500 inputs the deviation I1, performs current control using PI control or the like, and outputs the current-controlled voltage control command value Vref1.

The voltage control command value Vref1 is sent to the reaction force device 30 and input to the PWM control unit 37 to calculate the duty, and the reaction force motor 31 is PWM-driven via the inverter 38 by the PWM signal from the PWM control unit 37. The motor current value Imr of the reaction force motor 31 is detected by the motor current detector 39 and fed back to the subtraction unit 520 of the reaction force control system 60.

The steering control system 70 includes a target steering angle generating unit 600, a steering angle control unit 700, a current control unit 800, and a subtraction unit 810, and performs control so that the steering angle θt follows the target steering angle θtref. The target steering angle θtref is generated based on the steering angle θh in the target steering angle generating unit 600, and the target steering angle θtref is input to the steering angle control unit 700 together with the steering angle θt, and the steering angle control unit 700 calculates a current command value Imct such that the steering angle θt becomes the target steering angle θtref. Then, the subtraction unit 810 calculates the deviation I2 (=Imct-Imd) between the current command value Imct and the current value (motor current value) Imd of the steering motor 41 detected by the motor current detector 49, and the current control unit 800 determines the voltage control command value Vref2 based on the deviation I2. In the steering device 40, the steering motor 41 is driven and controlled via the PWM control unit 47 and the inverter 48 based on the voltage control command value Vref2.

An example of the configuration of the target steering angle generation unit 600 is shown in FIG. 11. The target steering angle generation unit 600 includes a limiting unit 610, a rate limiting unit 620, and a correction unit 630.

The limiting unit 610 limits the upper and lower limits of the steering angle θh and outputs the steering angle θh1. By limiting the upper and lower limits of the steering angle θh, the output of an abnormal value is suppressed when the steering angle θh becomes an abnormal value due to data corruption in RAM caused by a hardware error or a communication error. As shown in FIG. 12, an upper limit and a lower limit for the steering angle are set in advance, and when the input steering angle θh is equal to or greater than the upper limit, the upper limit is output as the steering angle θh1. When the input steering angle θh is equal to or greater than the lower limit, the lower limit is output as the steering angle θh. In other cases, the limiting unit 610 can be omitted. In cases where the steering angle does not become an abnormal value or when the output of an abnormal value is suppressed by other means, the limiting unit 610 can be omitted.

In order to prevent a sudden change in the steering angle when a very sudden steering operation is performed or when the steering angle becomes an abnormal value as described above, the rate limiting unit 620 sets a limit value for the amount of change in the steering angle θh1, applies a limit, and outputs the steering angle θh2. For example, the difference from the steering angle θh1 one sample before is set as the amount of change, and if the absolute value of the amount of change is greater than a predetermined value (limit value), the steering angle θh1 is added or subtracted so that the absolute value of the amount of change becomes the limit value, and is output as the steering angle θh2, and if it is equal to or less than the limit value, the steering angle θh1 is output as the steering angle θh2 as it is. By applying a limit to the amount of change in the steering angle θh1, a sudden change in the target steering angle is prevented and unstable behavior of the vehicle is suppressed. Note that instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to apply a limit, and a limit may be applied to the rate of change or the difference rate instead of the amount of change. Furthermore, the rate limiting unit 620 can be omitted if the steering angle does not change suddenly or if other means are used to avoid sudden changes.

The correction unit 630 corrects the steering angle θh2 and outputs the target steering angle θtref. For example, the target steering angle θtref is calculated from the steering angle θh2 using a map that defines the characteristics of the target steering angle θtref with respect to the magnitude |θh2| of the steering angle θh2, such as the basic map unit 110 in the target steering torque generation unit 100. Alternatively, the target steering angle θtref may be calculated simply by multiplying the steering angle θh2 by a predetermined gain.

The steering angle control unit 700 has the same configuration and operation as the torsion angle control unit 400, and uses the target steering angle θtref and steering angle θt through PI-D control to calculate a current command value Imct such that the steering angle θt follows the target steering angle θtref.

The subtraction unit 810, the current control unit 800, the PWM control unit 47, the inverter 48, and the motor current detector 49 have the same configuration and perform the same operation as the subtraction unit 520, the current control unit 500, the PWM control unit 37, the inverter 38, and the motor current detector 39, respectively.

In this configuration, an example of the operation of this embodiment will be described with reference to the flowcharts in Figures 13 to 16.

When operation starts, the steering angle θh, vehicle speed Vs, torsional angle Δθ, and turning angle θt are detected or calculated (step S10), and the steering angle θh is input to the target steering torque generation unit 100, the end contact determination unit 200, and the target turning angle generation unit 600, the vehicle speed Vs to the target steering torque generation unit 100, the torsional angle Δθ to the torsional angle control unit 400, and the turning angle θt to the turning angle control unit 700.

The target steering torque generating unit 100 receives the steering angle θh and the vehicle speed Vs and generates the target steering torque TrefA (step S20). An example of the operation of the target steering torque generating unit 100 will be described with reference to the flowchart in FIG. 14.

The steering angle θh input to the target steering torque generation unit 100 is input to the basic map unit 110 and the differentiation unit 120, and the vehicle speed Vs is input to the basic map unit 110 and the damper gain unit 130 (step S21).

The basic map unit 110 uses the basic map shown in FIG. 5(A) or (B) to generate a torque signal Tref_a corresponding to the steering angle θh and the vehicle speed Vs, and outputs it to the adder unit 150 (step S22).

The differentiating unit 120 differentiates the steering angle θh to output the steering angular velocity ωh1 (step S23), the damper gain unit 130 uses the damper gain map shown in Fig. 6 to output the damper gain _DG according to the vehicle speed Vs (step S24), and the multiplying unit 140 multiplies the steering angular velocity ωh1 by the damper gain _DG to calculate a torque signal Tref_b and outputs it to the adding unit 150 (step S25). Then, the adding unit 150 adds the torque signals Tref_a and Tref_b to calculate the target steering torque TrefA (step S26).

The end contact determination unit 200, which has received the steering angle θh, calculates the end contact determination gain Ge (step S30). An example of the operation of the end contact determination unit 200 will be described with reference to the flowchart in FIG. 15. Note that the initial value of the steering state St output by the steering state determination unit 210 is the "end contact OFF state", and the immediately preceding end contact determination gain Gep used by the gain calculation unit 220 is preset to 1 as an initial value.

The steering angle θh input to the end contact determination unit 200 is input to the steering state determination unit 210 (step S31).

If the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1 (step S32), the steering state determination unit 210 determines that the steering state St has become the end contact ON state, and sets the steering state St to the "end contact ON state" (step S33). If the magnitude |θh| of the steering angle θh is smaller than the first steering angle threshold θth1 (step S32), it checks whether the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 (step S34). Then, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2, it determines that the steering state St has become the end contact OFF state, and sets the steering state St to the "end contact OFF state" (step S35), and if not, the steering state St is left unchanged. The steering state determination unit 210 outputs the steering state St to the gain calculation unit 220 (step S36).

When the steering state St is "end contact ON state" (step S37), the gain calculation unit 220 sets the end contact judgment gain Ge to a value obtained by subtracting a constant value FR1 from the previous end contact judgment gain Gep (step S38), and if the end contact judgment gain Ge is 0 or less (step S39), sets the end contact judgment gain Ge to 0 (step S40). When the steering state St is "end contact OFF state" (step S37), the end contact judgment gain Ge is set to a value obtained by adding a constant value FR2 to the previous end contact judgment gain Gep (step S41), and if the end contact judgment gain Ge is 1 or more (step S42), sets the end contact judgment gain Ge to 1 (step S43). Then, the previous end contact judgment gain Gep is updated to the newly calculated end contact judgment gain Ge (step S44), and the end contact judgment gain Ge is output to the multiplication unit 510 (step S45).

The multiplication unit 510 multiplies the target steering torque TrefA by the end contact judgment gain Ge (step S50), and the multiplication result is output to the conversion unit 300 as the target steering torque Tref.

The conversion unit 300 converts the target steering torque Tref into a target torsion angle Δθref (step S60), and the target torsion angle Δθref is input to the torsion angle control unit 400.

The torsion angle control unit 400 inputs the torsion angle Δθ together with the target torsion angle Δθref, performs PI-D control using the configuration shown in FIG. 10, and calculates the current command value Imc (step S70).

The current command value Imc is added to the subtraction unit 520, which calculates the deviation I1 from the motor current value Imr detected by the motor current detector 39 (step S80). The deviation I1 is input to the current control unit 500, which calculates the voltage control command value Vref1 by current control (step S90). After that, the reaction force motor 31 is driven and controlled via the PWM control unit 37 and the inverter 38 based on the voltage control command value Vref1 (step S100).

On the other hand, the target steering angle generating unit 600, which has received the steering angle θh, generates the target steering angle θtref (step S110). An example of the operation of the target steering angle generating unit 600 will be described with reference to the flowchart in FIG. 16.

The steering angle θh input to the target steering angle generation unit 600 is input to the limiting unit 610. The limiting unit 610 limits the upper and lower limits of the steering angle θh using preset upper and lower limits (step S111), and outputs the steering angle θh1 to the rate limiting unit 620. The rate limiting unit 620 limits the amount of change in the steering angle θh1 using preset limits (step S112), and outputs the steering angle θh2 to the correction unit 630. The correction unit 630 corrects the steering angle θh2 to obtain the target steering angle θtref (step S113). The target steering angle θtref is input to the steering angle control unit 700.

The steering angle control unit 700 inputs the steering angle θt along with the target steering angle θtref, and calculates the current command value Imct using PI-D control (step S120).

The current command value Imct is added to the subtraction unit 810, which calculates the deviation I2 from the motor current value Imd detected by the motor current detector 49 (step S130). The deviation I2 is input to the current control unit 800, which calculates the voltage control command value Vref2 by current control (step S140). After that, the steering motor 41 is driven and controlled via the PWM control unit 47 and the inverter 48 based on the voltage control command value Vref2 (step S150).

The order of data input and calculations in Figures 13 to 16 can be changed as appropriate.

In the above-described operation example, the steering state determination unit 210 may select the determination to be made (end contact ON determination, end contact OFF determination) depending on the steering state St at the time of making the end contact determination. That is, the end contact ON determination is made only when the steering state St is in the end contact OFF state, and the end contact OFF determination is made only when the steering state St is in the end contact ON state. In this case, the operation of the steering state determination unit differs from the operations of steps S32 to S35 in the flowchart shown in Figure 15. That is, as shown in Figure 17, the steering state determination unit checks the steering state St after inputting the steering angle θh (step S31A). If the steering state St is the "end contact OFF state", an end contact ON determination is performed, and if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1 (step S32), the steering state St is set to the "end contact ON state" (step S33); otherwise, the steering state St is left as is. If the steering state St is the "end contact ON state", an end contact OFF determination is performed, and if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 (step S34), the steering state St is set to the "end contact OFF state" (step S35); otherwise, the steering state St is left as is. Then, the process continues to step S36.

In addition, in the gain calculation unit 220, the operations of steps S38 to S40 may be omitted if the end contact judgment gain Ge is set to 0. Similarly, the operations of steps S41 to S43 may be omitted if the end contact judgment gain Ge is set to 1.

In the above embodiment, the target steering torque generating unit 100 includes a damper gain unit 130, but in cases where the effect of the damper gain is realized by other means or where reducing the amount of calculation is important, the damper gain unit 130 may be omitted. In this case, the differentiation unit 120, the multiplication unit 140, and the addition unit 150 can also be omitted. The target steering torque generating unit 100 is not limited to the above-mentioned configuration as long as it is configured based on the steering angle.

In the above embodiment, in the end stop ON state, the magnitude of the target steering torque is reduced by multiplying the target steering torque by the end stop judgment gain, but the magnitude of the target steering torque may be reduced by other methods, such as subtracting an amount that increases over time. Similarly, in the end stop OFF state, the magnitude of the target steering torque is increased by multiplying the target steering torque by the end stop judgment gain, but the magnitude of the target steering torque may be increased by other methods, such as adding an amount that increases over time.

Other embodiments of the present invention will be described. Note that in the following embodiments, the same components as those in the other embodiments described above will be given the same reference numerals, and some or all of the description will be omitted.

In the first embodiment, the steering state determination unit 210 in the end contact determination unit 200 performs end contact determination using the steering angle as steering-related information, but by adding the steering angular velocity as steering-related information, the end contact determination can be performed using the steering angle and the steering angular velocity. Since the steering angular velocity at the steering end is approximately 0, and the steering angular velocity near the steering end is also very small, adding the steering angular velocity to the end contact determination can perform an end contact determination that is more in line with reality.

A configuration example (second embodiment) of the end contact determination unit corresponding to the above is shown in FIG. 18. In the end contact determination unit 200A in the second embodiment, compared to the end contact determination unit 200 in the first embodiment shown in FIG. 7, the steering state determination unit 210 is replaced by a steering state determination unit 210A, and in addition to the steering angle θh, the steering angular velocity ωh2 is input to the steering state determination unit 210A.

The steering angle velocity ωh2 is calculated by differentiating the steering angle θh in a differentiation unit 900 that is newly added to the reaction force control system. Instead of the steering angle velocity ωh2, the steering angle velocity ωh1 calculated by the differentiation unit 120 in the target steering torque generation unit 100 may be used. In this case, the differentiation unit 900 is not necessary.

The steering state determination unit 210A performs end contact determination using the steering angle θh and the steering angular velocity ωh2.

In the end contact ON determination, if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1 and the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than a predetermined threshold (first steering angular velocity threshold) ωth1 that has been set in advance, the steering state St is deemed to have entered the end contact ON state, and the "steering state St = end contact ON state" is determined. For example, 2 deg/sec is used as the first steering angular velocity threshold ωth1.

In the end contact OFF judgment, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2, or the magnitude |ωh2| of the steering angular velocity ωh2 is larger than a predetermined threshold (second steering angular velocity threshold) ωth2, the steering state St is deemed to have entered the end contact OFF state, and "steering state St = end contact OFF state" is determined. The second steering angular velocity threshold ωth2 is set to a range of the magnitude |ωh2| of the steering angular velocity ωh2 in which it is not determined that the steering state St has entered the end contact ON state in the end contact ON judgment, that is, a range larger than the first steering angular velocity threshold ωth1. In other words, the second steering angular velocity threshold ωth2 is set to a value larger than the first steering angular velocity threshold ωth1. For example, 5 deg/sec is used as the second steering angular velocity threshold ωth2.

The steering state determination unit 210A performs end contact determination in the same procedure as the steering state determination unit 210. That is, first, an end contact ON determination is performed, and if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1 and the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than the first steering angular velocity threshold ωth1, "steering state St = end contact ON state" is determined, otherwise an end contact OFF determination is performed. Then, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 or the magnitude |ωh2| of the steering angular velocity ωh2 is larger than the second steering angular velocity threshold ωth2 in the end contact OFF determination, "steering state St = end contact OFF state" is determined, otherwise the steering state St is not changed.

Compared to the operation of the first embodiment, the operation of the second embodiment is the same as the operation of the first embodiment except that the operation of the differential unit 900 to calculate the steering angular velocity ωh2 is added and the operation of the steering state determination unit is changed as described above.

In addition to the steering angle and steering angular velocity, the steering torque can be used as steering-related information to perform end-contact judgment. If the driver tries to turn the steering wheel further while the end-contact is ON, the steering torque increases, so by adding the steering torque to the end-contact judgment, the end-contact judgment can be performed more accurately.

A configuration example (third embodiment) of the end contact determination unit corresponding to the above is shown in FIG. 19. In the end contact determination unit 200B in the third embodiment, compared to the end contact determination unit 200A in the second embodiment shown in FIG. 18, the steering state determination unit 210A is replaced by the steering state determination unit 210B, and in addition to the steering angle θh and the steering angular velocity ωh2, the steering torque Th is input to the steering state determination unit 210B.

The steering torque Th may be detected by a torque sensor provided on the column shaft 2, or may be calculated by multiplying the torsion angle Δθ by the spring constant Kt of the torsion bar 2A.

The steering state determination unit 210B performs end contact determination using the steering angle θh, the steering angular velocity ωh2, and the steering torque Th.

In the end contact ON determination, if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than the first steering angular velocity threshold ωth1, and the magnitude |Th| of the steering torque Th is equal to or greater than a predetermined threshold (first steering torque threshold) Tth1 that has been set in advance, then the steering state St is deemed to have entered the end contact ON state, and the "steering state St = end contact ON state" is determined. For example, a value that is 30% of the maximum value of the steering torque Th is used as the first steering torque threshold Tth1.

In the end contact OFF judgment, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2, or the magnitude |ωh2| of the steering angular velocity ωh2 is larger than the second steering angular velocity threshold ωth2, or the magnitude |Th| of the steering torque Th is smaller than a predetermined threshold (second steering torque threshold) Tth2, the steering state St is deemed to have entered the end contact OFF state, and "steering state St = end contact OFF state" is determined. The second steering torque threshold Tth2 is set to a range of the magnitude |Th| of the steering torque Th in which it is not determined that the steering state St has entered the end contact ON state in the end contact ON judgment, that is, a range smaller than the first steering torque threshold Tth1. In other words, the second steering torque threshold Tth2 is set to a value smaller than the first steering torque threshold Tth1. For example, a value of 15% of the maximum value of the steering torque Th is used as the second steering torque threshold Tth2.

The steering state determination unit 210B performs end contact determination in the same procedure as the steering state determination unit 210A. That is, first, an end contact ON determination is performed, and if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, and the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than the first steering angular velocity threshold ωth1, and the magnitude |Th| of the steering torque Th is equal to or greater than the first steering torque threshold Tth1, it is determined that the "steering state St = end contact ON state", and if not, an end contact OFF determination is performed. Then, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 in the end contact OFF determination, or the magnitude |ωh2| of the steering angular velocity ωh2 is greater than the second steering angular velocity threshold ωth2, or the magnitude |Th| of the steering torque Th is smaller than the second steering torque threshold Tth2, then "steering state St = end contact OFF state" is determined; otherwise, the steering state St is not changed.

Compared to the operation of the second embodiment, the operation of the third embodiment is the same as the operation of the second embodiment except that the operation of detecting or calculating the steering torque Th is added and the operation of the steering state determination unit is changed as described above.

In addition to the steering angle, steering angular velocity, and steering torque, the motor current value can be used as steering-related information to perform end-contact judgment. By using the motor current value Imr of the reaction force motor 41, which is ultimately to be reduced when the end-contact is ON, for end-contact judgment, a more appropriate end-contact judgment that is directly linked to the effect can be performed.

A configuration example (fourth embodiment) of the end contact determination unit corresponding to the above is shown in FIG. 20. In the end contact determination unit 200C in the fourth embodiment, compared to the end contact determination unit 200B in the third embodiment shown in FIG. 19, the steering state determination unit 210B is replaced by a steering state determination unit 210C, and in addition to the steering angle θh, steering angular velocity ωh2, and steering torque Th, the motor current value Imr is input to the steering state determination unit 210C.

The motor current value Imr detected by the motor current detector 39 is input to the subtraction unit 520 for subtraction, and is also input to the steering state determination unit 210C.

The steering state determination unit 210C performs end contact determination using the steering angle θh, the steering angular velocity ωh2, the steering torque Th, and the motor current value Imr.

In the end contact ON determination, if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than the first steering angular velocity threshold ωth1, the magnitude |Th| of the steering torque Th is equal to or greater than the first steering torque threshold Tth1, and the motor current value Imr is equal to or greater than a predetermined threshold (first current threshold) Ith1 that has been set in advance, then the steering state St is deemed to have entered the end contact ON state, and the "steering state St = end contact ON state" is determined. For example, a value that is 30% of the maximum value of the motor current value Imr is used as the first current threshold Ith1.

In the end contact OFF judgment, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2, or the magnitude |ωh2| of the steering angular velocity ωh2 is larger than the second steering angular velocity threshold ωth2, or the magnitude |Th| of the steering torque Th is smaller than the second steering torque threshold Tth2, or the motor current value Imr is smaller than a predetermined threshold (second current threshold) Ith2 set in advance, the steering state St is deemed to be in the end contact OFF state, and the "steering state St = end contact OFF state" is determined. The second current threshold Ith2 is set to a range of the motor current value Imr in which it is not determined that the steering state St has become the end contact ON state in the end contact ON judgment, that is, a range smaller than the first current threshold Ith1. In other words, the second current threshold Ith2 is set to a value smaller than the first current threshold Ith1. For example, the second current threshold Ith2 is set to 15% of the maximum motor current value Imr.

The steering state determination unit 210C performs end contact determination in the same procedure as the steering state determination unit 210B. That is, first, an end contact ON determination is performed, and if the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, the magnitude |ωh2| of the steering angular velocity ωh2 is equal to or less than the first steering angular velocity threshold ωth1, the magnitude |Th| of the steering torque Th is equal to or greater than the first steering torque threshold Tth1, and the motor current value Imr is equal to or greater than the first current threshold Ith1, then "steering state St = end contact ON state" is determined, and otherwise, an end contact OFF determination is performed. Then, if the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 in the end contact OFF determination, or the magnitude |ωh2| of the steering angular velocity ωh2 is greater than the second steering angular velocity threshold ωth2, or the magnitude |Th| of the steering torque Th is smaller than the second steering torque threshold Tth2, or the motor current value Imr is smaller than the second current threshold Ith2, then the "steering state St = end contact OFF state" is determined; otherwise, the steering state St is not changed.

Compared to the operation of the third embodiment, the operation of the steering state determination unit differs as described above, and the other operations are the same.

In addition, the current command value Imc may be used as steering-related information instead of the motor current value Imr.

In the above-described embodiments (first to fourth embodiments), the end contact judgment is performed using the combinations of "steering angle", "steering angle, steering angular velocity", "steering angle, steering angular velocity, steering torque", and "steering angle, steering angular velocity, steering torque, motor current value" as steering-related information, but the end contact judgment may be performed using other combinations. For example, the end contact judgment may be performed using the combinations of "steering torque", "steering angle, steering torque", "steering torque, steering angular velocity", or these plus "motor current value".

For the end contact judgment in the above-mentioned embodiment, elapsed time can also be added as a condition. For example, in the end contact ON judgment in the first embodiment, when the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1, it is judged that the steering state St has become the end contact ON state. However, when the state in which the magnitude |θh| of the steering angle θh is equal to or greater than the first steering angle threshold θth1 continues for a predetermined time (first predetermined time), it is judged that the end contact ON state has been reached for the first time. If the magnitude |θh| of the steering angle θh becomes smaller than the first steering angle threshold θth1 before the predetermined time has elapsed, it is not judged that the end contact ON state has been reached. In the end contact OFF judgment, elapsed time is similarly added as a condition, and it is judged that the end contact OFF state has been reached for the first time when the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 continues for a predetermined time (second predetermined time). Adding elapsed time to the conditions has the effect of suppressing hunting at the threshold boundary, and by combining it with the use of two different thresholds, which are also effective in suppressing hunting, a more flexible response to hunting can be taken. Adding elapsed time is also effective in suppressing one-off, sudden value fluctuations. A counter or the like can be used to determine whether a certain period of time has continued.

An example of operation (fifth embodiment) when adding elapsed time as a condition to the end contact judgment in the first embodiment will be described with reference to the flowchart in FIG. 21. The operation of the fifth embodiment differs from that of the first embodiment only in the operation of the steering state judgment unit, so FIG. 21 shows only the operation of the steering state judgment unit, and that operation will be described. Note that the steering state judgment unit has a counter used for end contact ON judgment (hereinafter referred to as the "ON counter") and a counter used for end contact OFF judgment (hereinafter referred to as the "OFF counter"), and each counter is preset with an initial value of 0.

Following step S31 in the flowchart shown in FIG. 15, if the magnitude |θh| of the input steering angle θh is equal to or greater than the first steering angle threshold θth1 (step S32), the steering state determination unit increments the ON counter by one (step S32A). Then, if the ON counter is equal to or greater than a preset predetermined value Ft1 (step S32B), it determines that the steering state St has become the end contact ON state, sets the steering state St to the "end contact ON state" (step S33), and resets the ON counter to 0 (step S33A). If the ON counter is smaller than the predetermined value Ft1 (step S32B), it determines that the end contact ON state has not yet been reached, and does not change the steering state St. If the magnitude |θh| of the steering angle θh is smaller than the first steering angle threshold θth1 (step S32), the ON counter is reset to 0 (step S33B), and it is checked whether the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2 (step S34). If the magnitude |θh| of the steering angle θh is smaller than the second steering angle threshold θth2, the OFF counter is incremented by one (step S34A). Then, if the OFF counter is equal to or greater than a predetermined value Ft2 (step S34B), it is determined that the steering state St has become the end contact OFF state, the steering state St is set to the "end contact OFF state" (step S35), and the OFF counter is reset to 0 (step S35A). If the OFF counter is smaller than the predetermined value Ft2 (step S34B), it is determined that the end contact OFF state has not yet been reached, and the steering state St is not changed. If the magnitude |θh| of the steering angle θh is equal to or greater than the second steering angle threshold θth2 in step S34, the OFF counter is reset to 0 (step S35B), and the steering state St is left unchanged. Then, the process proceeds to step S36.

The order of data input and calculations in Figure 21 can be changed as appropriate.

In the above-mentioned end contact judgment, the preset values Ft1 and Ft2 may be the same or different. Also, although the elapsed time is added as a condition for both the end contact ON judgment and the end contact OFF judgment, it may be added to only one of them.

The elapsed time can also be added as a condition for the end contact judgment in the second to fourth embodiments. In this case, the predetermined time set in advance for each condition of the steering angular velocity ωh2, steering torque Th, and motor current value Imr may be the same as the predetermined time set for the condition of the steering angle θh, or may be different for each condition.

In the above-described embodiments (first to fifth embodiments), the target steering torque is used as the control information, and the motor current value is reduced by reducing the magnitude of the target steering torque, but other data calculated before the motor current value is determined can also be used as the control information. For example, the current command value can be used as the control information.

Figure 22 is a block diagram showing an example of the configuration of a reaction force control system (sixth embodiment) when the current command value Imc is used as control information, as opposed to the first embodiment. In the reaction force control system 60D in the sixth embodiment, compared to the reaction force control system 60 in the first embodiment shown in Figure 3, the multiplication unit 510 is installed after the torsion angle control unit 400, not after the target steering torque generation unit 100, and the target steering torque TrefA output from the target steering torque generation unit 100 is input to the conversion unit 300, the end contact judgment gain Ge output from the end contact judgment unit 200 is multiplied by the current command value Imc output from the torsion angle control unit 400 in the multiplication unit 510, and the multiplication result is added and input to the subtraction unit 520 as the current command value ImcD.

An example of the operation of the reaction force control system 60D of the sixth embodiment configured as described above will be described with reference to the flowchart in FIG. 23. FIG. 23 shows only the parts of the example of the operation of the first embodiment shown in FIG. 13 where the flow of the operation is different.

The target steering torque TrefA generated in step S20 in the flowchart shown in FIG. 13 is input to the conversion unit 300, and the end contact judgment gain Ge calculated in step S30 is input to the multiplication unit 510.

The conversion unit 300 converts the target steering torque TrefA into a target torsion angle Δθref (step S60), and the target torsion angle Δθref is input to the torsion angle control unit 400.

As in the first embodiment, the torsion angle control unit 400 inputs the torsion angle Δθ together with the target torsion angle Δθref, performs PI-D control, and calculates the current command value Imc (step S70).

The current command value Imc is input to the multiplication unit 510, where it is multiplied by the end contact judgment gain Ge (step S70A), and the multiplication result is output as the current command value ImcD.

The current command value ImcD is added to the subtraction unit 520, which calculates the deviation I1 from the motor current value Imr detected by the motor current detector 39 (step S80). Then, the process proceeds to step S90.

For the second to fifth embodiments, the current command value can be used as the control information instead of the target steering torque. Also, in addition to the target steering torque and the current command value, the target torsion angle, etc. can be used as the control information.

In the above-described embodiments (first to sixth embodiments), the reaction force control system controls the torsion angle to follow the target torsion angle, but the control in the reaction force control system is not limited to this, and it may also control the steering angle to follow the target steering angle, etc.

In the above embodiment, one control device has a reaction force control system and a steering control system, but a control device having only a reaction force control system and a control device having only a steering control system may be provided. In this case, the control devices transmit and receive data by communication. The SBW system shown in FIG. 1 does not have a mechanical connection between the reaction force device 30 and the steering device 40, but the present invention can also be applied to an SBW system equipped with a mechanical torque transmission mechanism that mechanically connects the column shaft 2 and the steering mechanism with a clutch or the like when an abnormality occurs in the system. In such an SBW system, when the system is normal, the clutch is turned off to release the mechanical torque transmission, and when the system is abnormal, the clutch is turned on to enable the mechanical torque transmission. Furthermore, although the reaction force device 30 has a torsion bar, it does not have to be limited to a torsion bar as long as an elastic body or mechanism having an arbitrary spring constant is used between the handle 1 and the reaction force motor 31.

In the above embodiment, the torsion angle control unit directly calculates the current command value, but before calculating the current command value, it is also possible to first calculate the motor torque (target torque) to be output, and then calculate the current command value. In this case, the commonly used relationship between motor current and motor torque is used to find the current command value from the motor torque.

The figures used above are conceptual diagrams for providing a qualitative explanation of the present invention, and are not intended to be limiting. The above-described embodiment is an example of a preferred embodiment of the present invention, but is not intended to be limiting, and various modifications may be made without departing from the spirit of the present invention.

1. Handle 2. Column shaft (steering shaft, handle shaft)
Reference Signs List 2A torsion bar 10 vehicle speed sensor 30 reaction force device 31 reaction force motor 32, 42 speed reduction mechanism 33 steering angle sensor 34, 43 angle sensor 35 stopper 36 torsion angle calculation section 37, 47 PWM control section 38, 48 inverter 39, 49 motor current detector 40 steering device 41 steering motor 50 control device 60, 60D reaction force control system 70 steering control system 100 target steering torque generation section 110 basic map section 130 damper gain section 200, 200A, 200B, 200C end contact determination section 210, 210A, 210B, 210C steering state determination section 220 gain calculation section 300 conversion section 400 torsion angle control section 500, 800 current control section 600 target steering angle generation section 610 Limiting section 620 Rate limiting section 630 Correcting section 700 Steering angle control section

Claims (13)

A control device for a vehicle steering system, which has a steering limit that is a steerable limit of a steering mechanism , and drives and controls a reaction force actuator by adjusting a supplied current, and controls the steering mechanism,
an end contact determination unit that uses steering-related information detected in the steering mechanism to determine whether the steering state is an end contact ON state in which the steering has been performed to the vicinity of the steering end point, or an end contact OFF state in which the steering has not been performed to the vicinity of the steering end point,
the end contact determination unit determines the steering state using a first threshold value for determining whether the steering state has become the end contact ON state and a second threshold value for determining whether the steering state has become the end contact OFF state, the first threshold value being set for the steering-related information;
The second threshold value is set to a range of values of the steering-related information in which it is not determined that the steering state has become the end contact ON state based on the determination based on the first threshold value,
2. A control device for a vehicle steering system, comprising: a control unit for controlling a steering force of a vehicle; a control unit for controlling a steering force of a vehicle; The control device for a vehicle steering system according to claim 1, wherein when the steering state is the end contact OFF state, the control information is increased to restore the reduced current. the end contact determination unit has a gain that decreases over time when the steering state is the end contact ON state,
2. The control device for a vehicle steering system according to claim 1, wherein the control information is reduced by multiplying the gain. the end contact determination unit has a gain that decreases over time when the steering state is the end contact ON state and increases over time when the steering state is the end contact OFF state,
3. The control device for a vehicle steering system according to claim 2, wherein the control information is increased or decreased by multiplying the gain. The end contact determination unit,
A steering angle is used as the steering-related information,
When the condition that the magnitude of the steering angle is equal to or greater than a first steering angle threshold is satisfied, it is determined that the steering state is in the end contact ON state,
When the magnitude of the steering angle satisfies a condition that the magnitude of the steering angle is smaller than a second steering angle threshold value that is smaller than the first steering angle threshold value, it is determined that the steering state has entered the end contact OFF state ,
When the magnitude of the steering angle satisfies a condition that the magnitude is smaller than the first steering angle threshold value and is equal to or larger than the second steering angle threshold value, the previous determination of the end contact determination unit is maintained.
5. A control device for a vehicle steering system according to claim 1. The control device for a vehicle steering system according to claim 5 , wherein the end contact determination unit makes a determination corresponding to each of the conditions when the each of the conditions is continuously satisfied for a predetermined time period set for the each of the conditions. a target steering torque generation unit that generates a target steering torque;
A conversion unit that converts the target steering torque into a target twist angle;
a torsion angle control unit that calculates a current command value that is a target value of the current so that the torsion angle of a torsion bar of the steering mechanism follows the target torsion angle,
7. The control device for a vehicle steering system according to claim 1, wherein the target steering torque is used as the control information. a target steering torque generation unit that generates a target steering torque;
A conversion unit that converts the target steering torque into a target twist angle;
a torsion angle control unit that calculates a current command value that is a target value of the current so that the torsion angle of a torsion bar of the steering mechanism follows the target torsion angle,
7. The control device for a vehicle steering system according to claim 1, wherein the current command value is used as the control information. 9. The control device for a vehicle steering system according to claim 1, wherein the steering mechanism has an elastic body or a torsion bar between a handle and the reaction force actuator. A control device for a vehicle steering system, which has a steering end point which is a steerable limit of a steering mechanism , and drives and controls a reaction force actuator by adjusting a current supplied thereto to control the steering mechanism, wherein after a state in which the magnitude of the steering torque is equal to or greater than a first steering torque threshold value continues for a first predetermined time, in order to reduce the current, control information which is a basis for adjusting the current is reduced;
A control device for a vehicle steering system, characterized in that after the current is reduced, the control information is increased to restore the reduced current after the magnitude of the steering torque continues to be smaller than a second steering torque threshold value that is smaller than the first steering torque threshold value for a second predetermined time. A control device for a vehicle steering system, which has a steering limit that is a steerable limit of a steering mechanism , and drives and controls a reaction force actuator by adjusting a supplied current, and controls the steering mechanism,
After the state in which the magnitude of the steering angle is equal to or greater than the first steering angle threshold continues for a first predetermined time,
reducing control information on which the current is adjusted to reduce the current;
A control device for a vehicle steering system, characterized in that after the current is reduced , the control information is increased to restore the reduced current after the steering angle continues to be smaller than a second steering angle threshold that is smaller than the first steering angle threshold for a second predetermined time. 12. The control device for a vehicle steering system according to claim 10 , wherein the steering mechanism has an elastic body or a torsion bar between a handle and the reaction force actuator. A control device for a vehicle steering system according to any one of claims 1 to 12 ,
and the steering mechanism controlled by the control device.

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