Vehicle steering system control device

Abstract

To provide a control device for a vehicular steering system capable of suppressing a turn-over of a steering wheel under a situation in which a turning is restricted.SOLUTION: In accordance with a deviation θt_err between a turning angle target value and an actual turning angle, a torque value Tref_c is generated which is a compensation value for a steering torque target value that is a target value of steering torque to obtain turning reaction force. The torque value Tref_c increases by a first inclination in a first region in which the deviation θt_err is equal to or greater than a first threshold θt_err_th.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a control device for a steering system for a vehicle. [Background technology]

[0002] One type of vehicle steering system is the steer-by-wire (SBW) system, in which a steering mechanism (FFA: Force Feedback Actuator) having a steering wheel operated by the driver and a road wheel actuator (RWA: Road Wheel Actuator) that steers the steered wheels are mechanically separated. In the SBW system, the steering mechanism and the road wheel actuator are electrically connected via an electronic control unit (ECU). The steering wheel operation is transmitted to the road wheel actuator via an electrical signal to steer the steered wheels, and the road wheel actuator generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates the steering reaction force using a reaction force actuator equipped with a reaction force motor, and the road wheel actuator steers the steered wheels using a steering actuator equipped with a steering motor. The reaction force actuator and the road wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction force actuator is transmitted to the driver via the column shaft and the road wheel (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-185819 Summary of the Invention [Problem to be solved by the invention]

[0004] In SBW systems, where the steering mechanism and the turning mechanism are mechanically separated, there is a possibility that the steering wheel will spin when the driver turns the steering wheel in a situation where the turning wheel cannot be turned, for example, when the steered wheel hits an obstacle such as a curb.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control device for a vehicle steering system that can suppress steering wheel spin when steering is restricted. [Means for solving the problem]

[0006] In order to achieve the above object, a control device for a vehicle steering system according to one aspect of the present invention comprises: A control device for a vehicle steering system including a reaction force device that applies a steering reaction force to a steering wheel in accordance with a steering angle of the steering wheel, and a steering device that steers steered wheels in accordance with the steering angle of the steering wheel, the control device comprising: a steering torque target value generation unit that generates a steering torque target value that is a target value of steering torque for obtaining the steering reaction force; and a steering angle target value generation unit that generates a steering angle target value that is a target value of the steering angle of the steered wheels based on the steering angle, the steering torque target value generation unit comprising a steering torque compensation value generation unit that generates a compensation value for the steering torque target value in accordance with a deviation between the turning angle target value and an actual turning angle that is the actual turning angle of the steered wheels, and the compensation value increases at a first slope in a first region where the deviation is equal to or greater than a predetermined first threshold.

[0007] According to the above configuration, when the steering becomes impossible while the driver is steering the steering wheel and the deviation between the steering angle target value and the steering angle becomes equal to or greater than the first threshold value, a steering reaction force can be applied that resists the steering force applied by the driver, thereby making it possible to suppress spinning of the steering wheel when the steering becomes impossible.

[0008] As a desirable aspect of the control device for a vehicle steering system, the first region is delimited by a second threshold value that is greater than the first threshold value, and the compensation value is such that the first slope increases as the deviation increases in a region where the deviation is less than the second threshold value, and the first slope is a constant value in a region where the deviation is equal to or greater than the second threshold value.

[0009] According to the above configuration, in the region equal to or greater than the first threshold and less than the second threshold, the first slope gradually increases as the deviation between the target steering angle value and the steering angle increases, thereby suppressing the discomfort caused by a sudden change in the compensation value when steering becomes impossible.

[0010] In a preferred embodiment of the control device for a vehicle steering system, the compensation value is preferably zero in a second region where the deviation is less than the first threshold value.

[0011] According to the above configuration, the compensation value is zero when the vehicle is not in a state where steering is impossible.

[0012] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the compensation value increases at a second slope smaller than the first slope as the deviation increases in a second region where the deviation is less than the first threshold value.

[0013] According to the above configuration, in the second region, the compensation value gradually increases as the deviation between the steering angle target value and the steering angle increases. As a result, for example, in a situation where the deviation between the steering angle target value and the steering angle gradually increases, the steering reaction force applied to the steering wheel can be gradually increased as the deviation between the steering angle target value and the steering angle increases.

[0014] In a preferred embodiment of the control device for a vehicle steering system, the steering torque compensation value generating section preferably includes a phase compensating section that performs phase lead compensation on the compensation value.

[0015] According to the above configuration, it is possible to suppress the steering wheel from bouncing back when steering becomes impossible.

[0016] In a preferred embodiment of the control device for a vehicle steering system, a limiting unit is provided that limits upper and lower limits of the steering torque target value as the compensation value increases.

[0017] According to the above configuration, it is possible to suppress occurrence of control abnormalities in the control of the control device. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a control device for a vehicle steering system that can suppress wheel spin when steering is restricted. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing the hardware configuration of the ECU. [Figure 3] FIG. 3 is a diagram illustrating an example of a control block configuration of the control device according to the present disclosure. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to the first embodiment. [Figure 5A] FIG. 5A is a diagram showing an example of the characteristics of the basic map. [Figure 5B] FIG. 5B is a diagram showing an example of the characteristics of the torque value Tref_basic. [Figure 6A] FIG. 6A is a diagram showing an example of the characteristics of a damper gain map. [Figure 6B] FIG. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. [Figure 7] FIG. 7 is a region diagram for explaining the steering direction in the present disclosure. [Figure 8] FIG. 8 is a conceptual diagram showing a specific example of a situation in which steering becomes impossible due to an obstacle. [Figure 9] FIG. 9 is a block diagram showing an example of the configuration of the steering torque compensation value calculation unit according to the first embodiment. [Figure 10] FIG. 10 is a diagram showing a first example of characteristics of the steering torque compensation value map. [Figure 11] FIG. 11 is a diagram showing an example of the characteristics of the torque value Tref_c after sign conversion when the first example of the characteristics of the steering torque compensation value map shown in FIG. 10 is applied. [Figure 12] FIG. 12 is a diagram showing a second characteristic example of the steering torque compensation value map. [Figure 13] FIG. 13 is a diagram showing an example of the characteristics of the torque value Tref_c after sign conversion when the second example of the characteristics of the steering torque compensation value map shown in FIG. 12 is applied. [Figure 14] FIG. 14 is a diagram showing a third characteristic example of the steering torque compensation value map. [Figure 15] FIG. 15 is a diagram showing an example of the characteristics of the torque value Tref_c after sign conversion when the third example of the characteristics of the steering torque compensation value map shown in FIG. 14 is applied. [Figure 16] FIG. 16 is a block diagram showing a modified example of the steering torque compensation value calculation unit according to the first embodiment. [Figure 17] FIG. 17 is a diagram illustrating a conceptual operation example of the steering torque target value generating unit according to the first embodiment. [Figure 18] FIG. 18 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to the second embodiment. [Figure 19] FIG. 19 is a diagram showing a conceptual operation example of the steering torque target value generating unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0021] (Embodiment 1) 1 is a block diagram showing an example of an outline of an SBW system equipped with a control device according to the present disclosure, which includes a reaction force device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

[0022] The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft (steering shaft, handle shaft) 2, which is found in general electric power steering devices, and instead transmits the driver's operation of the steering wheel 1 as an electrical signal, specifically the steering angle θh output from the reaction force device 30, as an electrical signal.

[0023] 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. The reaction force device 30 transmits the vehicle's motion state, which is transmitted from the steered wheels 5L, 5R, to the driver as a steering reaction force. The reaction force motor 31 applies the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

[0024] The reaction force device 30 further includes a steering angle sensor 33 and a torque sensor 34. The steering angle sensor 33 detects the steering angle θh of the steering wheel 1. The torque sensor 34 detects the steering torque Th of the steering wheel 1. Hereinafter, the steering angle θh detected by the steering angle sensor 33 will also be referred to as the "actual steering angle θh_act," and the steering torque Th detected by the torque sensor 34 will also be referred to as the "actual steering torque Th_act."

[0025] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point, which is the limit of possible steering, is provided on the column shaft 2. That is, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0026] 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 the rotational motion of the steering motor 41 into linear motion. The steering device 40 drives the steering motor 41 in accordance with the steering angle θh, and the resulting drive force is applied to the pinion rack mechanism 44 via the speed reduction mechanism 42, and the drive force is passed through the tie rods 3a and 3b to steer the steerable wheels 5L and 5R. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steerable wheels 5L and 5R. Instead of the steering angle θt of the steerable wheels 5L and 5R, for example, the motor angle of the steering motor 41 or the position of the rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 will also be referred to as the "actual steering angle θt_act."

[0027] In order to cooperatively control the reaction force device 30 and the steering 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 steering motor 41 based on information such as the steering angle θh and the turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

[0028] The control device 50 is supplied with power from the battery 12 and receives an ignition key signal via the ignition key 11. A CAN (Controller Area Network) 20 that transmits and receives various vehicle information is also connected to the control device 50, and the vehicle speed Vs can also be received from the CAN 20. Furthermore, a non-CAN 21 that transmits and receives communications other than the CAN 20, analog / digital signals, radio waves, etc. can also be connected to the control device 50.

[0029] Specifically, the control device 50 is, for example, an ECU (Electronic Control Unit) mounted on a vehicle. The ECU is mainly composed of a CPU (including an MCU, an MPU, etc.). Fig. 2 is a schematic diagram showing the hardware configuration of the ECU. Cooperative control of the reaction force device 30 and the steering device 40 is mainly executed by a program inside the CPU of the ECU.

[0030] Fig. 3 is a diagram showing an example of a control block configuration of a control device according to the present disclosure. In Fig. 3, reaction force device 30 includes, in addition to reaction force motor 31 and the above-described configuration, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. Furthermore, turning device 40 includes, in addition to turning motor 41 and the above-described configuration, a PWM control unit 47, an inverter 48, and a motor current detector 49. Control device 50 implements the control blocks of reaction force control system 60, which controls reaction force device 30, and steering control system 70, which controls steering device 40. Reaction force control system 60 and steering control system 70 cooperate to control reaction force device 30 and steering device 40.

[0031] Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may include, for example, a RAM (random access memory) or a ROM (read only memory) for storing data, programs, etc., as shown in Fig. 2. The control device 50 may also include a PWM control unit 37, an inverter 38, a motor current detector 39, a PWM control unit 47, an inverter 48, and a motor current detector 49.

[0032] As shown in Fig. 3, control device 50 includes, as control blocks, steering torque target value generation section 200, steering torque control section 400, current control section 500, turning angle target value generation section 600, turning angle control section 700, and current control section 800. Steering torque target value generation section 200, steering torque control section 400, and current control section 500 are control blocks that make up reaction force control system 60. Turning angle target value generation section 600, turning angle control section 700, and current control section 800 are control blocks that make up steering control system 70.

[0033] The reaction force control system 60 performs control such that the actual steering torque Th_act detected by the torque sensor 34 follows the steering torque target value Th_ref, which is the target value of the steering torque of the reaction force device 30.

[0034] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0035] The steering torque control unit 400 generates a motor current command value Ih_ref, which is a control target value of the current to be supplied to the reaction force motor 31. The steering torque control unit 400 calculates the motor current command value Ih_ref so that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero.

[0036] The current control unit 500 controls the current of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the motor current command value Ih_ref output from the steering torque control unit 400 and the actual current value (motor current value) Ih_act of the reaction force motor 31 detected by the motor current detector 39 approaches zero.

[0037] In the reaction force device 30, the reaction force motor 31 is controlled and driven via a PWM control unit 37 and an inverter 38 based on the voltage control command value Vh_ref.

[0038] The steering control system 70 performs control such that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

[0039] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0040] Steering angle control unit 700 generates motor current command value It_ref, which is a control target value for the current supplied to steering motor 41. Steering angle control unit 700 calculates motor current command value It_ref such that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero.

[0041] Current control unit 800 controls the current of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that deviation It_err between motor current command value It_ref output from steering angle control unit 700 and actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0042] In the steering device 40, the steering motor 41 is controlled and driven via a PWM control unit 47 and an inverter 48 based on the voltage control command value Vt_ref.

[0043] In this embodiment, steering torque control section 400, current control section 500, turning angle target value generation section 600, turning angle control section 700 and current control section 800 may have any configuration that can realize each control in reaction force control system 60 or turning control system 70, and are not limited by the configuration of each control block. The configuration of steering torque target value generation section 200 according to this embodiment will now be described with reference to Figure 4.

[0044] Fig. 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to embodiment 1. As shown in Fig. 4, the steering torque target value generating unit 200 according to this embodiment includes, as main components, a basic map unit 210, a damper torque generating unit 220, and a steering torque compensation value generating unit 230.

[0045] In the present disclosure, the sign extraction unit 280 shown in FIG. 4 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. As a result, the sign extraction unit 280 outputs "1" when the sign of the steering angle θh is "+", and outputs "-1" when the sign of the steering angle θh is "-". Specifically, the sign extraction unit 280 generates, for example, a sign function Sgn(θh) of the steering angle θh.

[0046] Fig. 5A is a diagram showing an example of the characteristics of the basic map. The steering angle |θh| and vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation unit 260 are input to the basic map unit 210. The basic map unit 210 generates a torque value Tref_basic using the vehicle speed Vs as a parameter, using the basic map shown in Fig. 5A. The torque value Tref_basic is used to generate a basic steering reaction force according to the steering angle |θh| and the vehicle speed Vs.

[0047] The torque value Tref_basic has an angle-sensitive characteristic that increases or decreases according to the steering angle |θh|. More specifically, as shown in FIG. 5A, the torque value Tref_basic increases as the steering angle |θh| increases. Furthermore, the torque value Tref_basic has a vehicle-speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. More specifically, as shown in FIG. 5A, the torque value Tref_basic increases as the vehicle speed Vs increases. In other words, the reaction force obtained by the torque value Tref_basic derived from the basic map shown in FIG. 5A increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and also increases as the vehicle speed (vehicle speed Vs) increases. Note that although the basic map shown in FIG. 5A has a vehicle-speed-sensitive characteristic, the present invention is not limited to this.

[0048] Fig. 5B is a diagram showing an example of the characteristics of the torque value Tref_a. The torque value Tref_a shown in Fig. 5B is obtained by multiplying the torque value Tref_basic output from the basic map unit 210 by the sign function Sgn(θh) output from the sign extraction unit 280 in a multiplier 293. Note that a configuration may be adopted that does not include the sign extraction unit 280, and instead obtains the torque value Tref_a using a basic map corresponding to the positive or negative steering angle θh, as shown in Fig. 5B.

[0049] The damper torque generation unit 220 includes a damper gain map unit 221 and a multiplication unit 222. Fig. 6A is a diagram showing an example of the characteristics of the damper gain map. The vehicle speed Vs is input to the damper gain map unit 221. The damper gain map unit 221 generates the damper gain DG using the damper gain map shown in Fig. 6A.

[0050] 6A, the damper gain DG has a vehicle speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. The damper torque generation unit 220 multiplies the angular velocity of the steering wheel 1 (hereinafter also referred to as "steering angular velocity ωh") calculated by differentiating the steering angle θh (differentiation unit 270) by the damper gain DG output from the damper gain map unit 221 (multiplication unit 222), and outputs the result as a torque value Tref_b.

[0051] The torque value Tref_b output from the damper torque generating unit 220 is added to the torque value Tref_a (addition unit 291), thereby making it possible to compensate for the steering reaction force in proportion to the steering angular velocity ωh.

[0052] Fig. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. The torque value Tref_a+Tref_b is obtained by adding the torque value Tref_a to the torque value Tref_b output from the damper torque generation unit 220. In Fig. 6B, the solid line indicates the torque value Tref_a+Tref_b when the steering angular velocity ωh is a positive value (ωh>0), and the dashed line indicates the torque value Tref_a+Tref_b when the steering angular velocity ωh is a negative value (ωh<0). Also in Fig. 6B, the dashed line indicates the torque value Tref_a.

[0053] 7 is a region diagram for explaining the steering direction in the present disclosure, in which the horizontal axis represents the steering angle θh and the vertical axis represents the steering angular velocity ωh.

[0054] Area A ((θh, ωh) = (+, +)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned further to the right (ωh > 0). Area B ((θh, ωh) = (+, -)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned back to the left (ωh < 0). Area C ((θh, ωh) = (-, -)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned further to the left (ωh < 0). Area D ((θh, ωh) = (-, +)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned back to the right (ωh > 0). Also, in Figure 7, on the steering angle θh axis (ωh=0), it is shown that the steering wheel 1 is neither being turned further nor turned back ((θh, ωh)=(θh,0)), and on the steering angular velocity ωh axis (θh=0), it is shown that the steering wheel 1 is in the center position ((θh, ωh)=(0, ωh)).

[0055] The torque value Tref_b output from the damper torque generation unit 220 is a positive value in regions A and D where the steering angular velocity ωh>0, and a negative value in regions B and C where the steering angular velocity ωh<0. As a result, when the steering angular velocity ωh>0, that is, in region A where the steering wheel 1 is turned to the right (θh>0) and further turned to the right, or in region D where the steering wheel 1 is turned to the left (θh<0) and turned back to the right, the torque value Tref_b is a value obtained by adding |Tref_b| to Tref_a, as shown by the solid line in Fig. 6B. On the other hand, when the steering angular velocity ωh<0, that is, in region B where the steering wheel 1 is turned to the right (θh>0) and turned back to the left, or in region C where the steering wheel 1 is turned to the left (θh<0) and further turned to the left, the torque value Tref_b is a value obtained by subtracting |Tref_b| from Tref_a, as shown by the dashed line in Fig. 6B.

[0056] 6B, the torque value Tref_a+Tref_b increases with increasing steering angle θ as the steering angle θh increases and approaches the steering end point limited by the stopper (rotation limiting mechanism) 35. In other words, the torque value Tref_a+Tref_b has a characteristic that the rate of change gradually decreases as the steering angle θh increases.

[0057] Fig. 8 is a conceptual diagram showing a specific example of a situation where steering is disabled due to an obstacle. Fig. 8 shows an example where the steered wheel 5R hits an obstacle OB such as a curb while the driver is steering the steering wheel 1 to the right, and the vehicle cannot be steered beyond the actual steering angle θt_act_ob.

[0058] In a SBW system where the steering mechanism and the turning mechanism are mechanically separated, the fact that the vehicle is unable to turn is not transmitted to the steering wheel 1 due to its structure, as shown in Figure 8. For this reason, the driver may not realize that the vehicle is unable to turn due to an obstacle OB, and may continue to apply right steering force FR to the steering wheel 1, causing the steering wheel 1 to spin.

[0059] In the present disclosure, as shown in Figures 3 and 4, a steering torque compensation value generation unit 230 is provided that generates a steering torque according to the deviation θt_err between the target steering angle value θt_ref and the actual steering angle θt_act, and torque value Tref_c generated by steering torque compensation value generation unit 230 is added to torque value Tref_a+Tref_b, and if steering becomes impossible while the driver is steering the steering wheel 1, a steering reaction force that resists the steering force by the driver is applied. This makes it possible to suppress spin of the steering wheel 1 when steering becomes impossible. Below, a configuration and operation that can suppress spin of the steering wheel 1 when steering is restricted will be described in detail.

[0060] Fig. 9 is a block diagram showing an example of the configuration of the steering torque compensation value calculation unit according to embodiment 1. In the example configuration shown in Fig. 9, the steering torque compensation value calculation unit 240 includes a steering torque compensation value map unit 241 as a main component.

[0061] Sign extraction section 243 shown in FIG. 9 extracts the sign of the deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act (hereinafter also referred to as "steering angle deviation"). Specifically, for example, the value of steering angle deviation θt_err is divided by the absolute value of steering angle deviation θt_err. As a result, sign extraction section 243 outputs "1" when the sign of steering angle deviation θt_err is "+", and outputs "-1" when the sign of steering angle deviation θt_err is "-". Specifically, sign extraction section 243 generates, for example, a sign function Sgn(θt_err) of steering angle deviation θt_err.

[0062] Fig. 10 is a diagram showing an example of the characteristics of a steering torque compensation value map. Steering torque compensation value map section 241 receives as input steering angle deviation |θt_err| that has been subjected to absolute value processing in absolute value calculation section 242. Steering torque compensation value map section 241 generates torque value Tref_c0 based on the steering torque compensation value map shown in Fig. 10.

[0063] The steering torque compensation value map has a turning angle deviation sensitive characteristic in which the torque value Tref_c0 increases or decreases according to the turning angle deviation |θt_err|, as shown in FIG. 10, for example.

[0064] 10 is also referred to as the "first region," and the region less than the first turning angle deviation threshold |θt_err_th1| is also referred to as the "second region." Furthermore, the slope (ΔTref_c0 / Δ|θt_err|) of the fluctuation amount ΔTref_c0 in the torque value Tref_c0 with respect to the fluctuation amount Δ|θt_err| in the turning angle deviation |θt_err| in the first region is also referred to as the "first slope," and the slope (ΔTref_c0 / Δ|θt_err|) of the fluctuation amount ΔTref_c0 in the torque value Tref_c0 with respect to the fluctuation amount Δ|θt_err| in the turning angle deviation |θt_err| in the second region is also referred to as the "second slope."

[0065] Δ1_aa and Δ1_bb shown in Fig. 10 indicate the first slope when the turning angle deviation |θt_err| is a value aa or a value bb that is equal to or greater than the first turning angle deviation threshold |θt_err_th1|. As shown in Fig. 10, when the relationship between the turning angle deviation |θt_err| and the torque value Tref_c0 is nonlinear in the first region, the first slope changes. When the relationship between the turning angle deviation |θt_err| and the torque value Tref_c0 is linear in the first region, the first slope is a constant value.

[0066] In the example shown in FIG. 10, the first region is separated by a second turning angle deviation threshold |θt_err_th2| that is greater than the first turning angle deviation threshold |θt_err_th1|. The first gradient in the first region increases as the turning angle deviation |θt_err| increases in a region where the turning angle deviation |θt_err| is less than the second turning angle deviation threshold |θt_err_th2|, and becomes a constant value in a region where the turning angle deviation |θt_err| is equal to or greater than the second turning angle deviation threshold |θt_err_th2|. The maximum value of the first gradient is, for example, about 10 [Nm] / 5 [deg] = 2 [Nm / deg]. Furthermore, in the example shown in FIG. 10, the second gradient in the second region is zero.

[0067] Steering torque compensation value calculation section 240 multiplies torque value Tref_c0, which is the output value of steering torque compensation value map section 241, by sign function Sgn(θt_err) of steering angle deviation θt_err in multiplication section 244 to output torque value Tref_c after sign conversion. Fig. 11 is a diagram showing an example of the characteristics of torque value Tref_c after sign conversion when the steering torque compensation value map shown in Fig. 10 is applied.

[0068] 11, for example, when the driver is steering the steering wheel 1 to the right, if the steering angle deviation θt_err exceeds the first positive steering angle deviation threshold θt_err_th1, the positive torque value Tref_c rises sharply, thereby restricting steering to the right.

[0069] Furthermore, for example, when the driver is steering the steering wheel 1 to the left, if the steering angle deviation θt_err exceeds the first negative steering angle deviation threshold θt_err_th1, the torque value Tref_c increases sharply, thereby restricting steering to the left.

[0070] 10 or 11, in a region where the steering angle deviation |θt_err| is equal to or greater than the first turning angle deviation threshold |θt_err_th1| and is less than the second turning angle deviation threshold |θt_err_th2|, the first slope gradually increases as the turning angle deviation |θt_err| increases. This makes it possible to suppress any discomfort caused by a sudden change in the torque value Tref_c.

[0071] Below, a modified example of the steering torque compensation value map will be explained.

[0072] Fig. 12 is a diagram showing a second example characteristic of the steering torque compensation value map. In the second example characteristic of the steering torque compensation value map shown in Fig. 12, the turning angle deviation threshold |θt_err_th| corresponds to the first turning angle deviation threshold |θt_err_th1| in the first example characteristic. That is, in the second example characteristic of the steering torque compensation value map shown in Fig. 12, the region equal to or greater than the turning angle deviation threshold |θt_err_th| corresponds to the "first region," and the region less than the turning angle deviation threshold |θt_err_th| corresponds to the "second region."

[0073] In the second characteristic example of the steering torque compensation value map shown in Fig. 12, the second slope in the second region is zero, as in the first characteristic example, and the first slope in the first region is a constant value. The first slope is, for example, about 10 [Nm] / 5 [deg]=2 [Nm / deg]. Fig. 13 is a diagram showing an example of the characteristic of the torque value Tref_c after sign conversion when the second characteristic example of the steering torque compensation value map shown in Fig. 12 is applied.

[0074] 13, for example, when the driver is steering the steering wheel 1 to the right, if the steering angle deviation θt_err exceeds the positive steering angle deviation threshold θt_err_th, the positive torque value Tref_c rises sharply, thereby restricting steering to the right.

[0075] Furthermore, for example, when the driver is steering the steering wheel 1 to the left, if the steering angle deviation θt_err exceeds the negative steering angle deviation threshold θt_err_th, the negative torque value Tref_c rises sharply, thereby restricting steering to the left.

[0076] Fig. 14 is a diagram showing a third example characteristic of the steering torque compensation value map. In the third example characteristic of the steering torque compensation value map shown in Fig. 14, the turning angle deviation threshold |θt_err_th| corresponds to the first turning angle deviation threshold |θt_err_th1| in the first example characteristic. That is, in the third example characteristic of the steering torque compensation value map shown in Fig. 14, the region equal to or greater than the turning angle deviation threshold |θt_err_th| corresponds to the "first region," and the region less than the turning angle deviation threshold |θt_err_th| corresponds to the "second region."

[0077] Δ2_cc shown in Fig. 14 indicates the second slope when the turning angle deviation |θt_err| is a value cc that is smaller than the first turning angle deviation threshold |θt_err_th1|. As shown in Fig. 14, when the relationship between the turning angle deviation |θt_err| and the torque value Tref_c0 is linear in the second region, the second slope is a constant value. Note that when the relationship between the turning angle deviation |θt_err| and the torque value Tref_c0 is nonlinear in the second region, the second slope Δ2_cc changes according to the turning angle deviation |θt_err|.

[0078] In the third characteristic example of the steering torque compensation value map shown in Fig. 14, the first gradient in the first region is a constant value of, for example, about 10 [Nm] / 5 [deg]=2 [Nm / deg], and the second gradient in the second region is a constant value smaller than the first gradient. Fig. 15 is a diagram showing an example of the characteristic of the torque value Tref_c after sign conversion when the third characteristic example of the steering torque compensation value map shown in Fig. 14 is applied.

[0079] In the example shown in Fig. 15, for example, when the driver steers the steering wheel 1 to the right, in the region where the steering angle deviation θt_err is less than the positive steering angle deviation threshold θt_err_th, the positive torque value Tref_c gradually increases as the positive steering angle deviation θt_err increases, and when the steering angle deviation θt_err exceeds the positive steering angle deviation threshold θt_err_th, the positive torque value Tref_c rises sharply. This restricts steering to the right.

[0080] Also, for example, when the driver is steering the steering wheel 1 to the left, in a region where the steering angle deviation θt_err is less than the negative steering angle deviation threshold θt_err_th, the negative torque value Tref_c gradually increases as the negative steering angle deviation θt_err increases, and when the steering angle deviation θt_err exceeds the negative steering angle deviation threshold θt_err_th, the negative torque value Tref_c rises sharply. This restricts steering to the left.

[0081] 14 or 15, torque value Tref_c gradually increases as steering angle deviation |θt_err| increases in the second region. Therefore, for example, in a situation where steering angle deviation |θt_err| gradually increases due to insufficient steering force of steering motor 41, the steering reaction force applied to steering wheel 1 can be gradually increased as steering angle deviation |θt_err| increases.

[0082] The steering torque compensation value calculation unit 240 may also be configured as shown in Fig. 16. Fig. 16 is a block diagram showing a modified example of the steering torque compensation value calculation unit according to the first embodiment.

[0083] The steering torque compensation value map unit 241a in the modified example of the steering torque compensation value calculation unit shown in Fig. 16 may have, for example, a steering torque compensation value map with the characteristics shown in Fig. 11 instead of the steering torque compensation value map with the characteristics shown in Fig. 10. Also, for example, a steering torque compensation value map with the characteristics shown in Fig. 13 instead of the steering torque compensation value map with the characteristics shown in Fig. 12. Also, for example, a steering torque compensation value map with the characteristics shown in Fig. 15 instead of the steering torque compensation value map with the characteristics shown in Fig. 14.

[0084] The torque value Tref_c output from the steering torque compensation value generation unit 230 is added to the torque value Tref_a and the torque value Tref_b in addition units 291 and 292 shown in Fig. 4. As a result, the steering torque target value generation unit 200 outputs the steering torque target value Th_ref.

[0085] Fig. 17 is a diagram showing a conceptual operation example of the steering torque target value generation unit according to embodiment 1. In Fig. 17, the horizontal axis represents actual steering angle θt_act, and the vertical axis represents steering torque target value Th_ref output from steering torque target value generation unit 200.

[0086] Fig. 17 shows an example in which, when the driver is steering the steering wheel 1 to the right, the steered wheel 5R hits an obstacle OB such as a curb at actual steering angle θt_act_ob, making the steering impossible, as shown in Fig. 8. At this time, when the steering angle deviation θt_err reaches the steering angle deviation threshold θt_err_th (first steering angle deviation threshold θt_err_th1 in the modes shown in Figs. 10 and 11) (Δθt_err = θt_err_th), in a region exceeding the actual steering angle θt_act_ob, steering torque target value Th_ref rises sharply by torque value Tref_c output from steering torque compensation value generation section 230. As a result, a steering reaction force is applied that resists the steering force generated by the driver operating the steering wheel 1, and spin of the steering wheel 1 is suppressed.

[0087] The characteristics of the steering torque compensation value map are not limited to the above-described aspects shown in Figures 10 to 15, as long as a steering reaction force that resists the steering force generated by the driver operating the steering wheel 1 is applied when the steering angle deviation |θt_err| exceeds the steering angle deviation threshold |θt_err_th| (first turning angle deviation threshold |θt_err_th1| in the aspects shown in Figures 10 and 11). Also, for example, instead of the map aspects shown in Figures 10 to 15, the characteristics may be defined by a predetermined transfer function.

[0088] (Embodiment 2) FIG. 18 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to the second embodiment.

[0089] In the configuration example shown in FIG. 18, the steering torque compensation value generation unit 230a of the steering torque target value generation unit 200a according to the second embodiment includes a phase compensation unit 250 in addition to the steering torque compensation value calculation unit 240 described in the first embodiment.

[0090] The phase compensation unit 250 performs phase lead compensation on the torque value Tref_c output from the steering torque compensation value calculation unit 240 to calculate the torque value Tref_d. The following calculation formula is used for the phase compensation filter C f It shows the characteristics of

[0091] C f =(T n S+1) / (T d S+1)

[0092] The cutoff frequency f of the numerator of the above formula n is f n =1 / (2π×T n ) and the cutoff frequency f d is f d =1 / (2π×T d )

[0093] The phase compensation unit 250 applies a phase compensation filter C expressed by the above equation to the torque value Tref_c output from the steering torque compensation value calculation unit 240. f The phase compensation filter C is used to perform phase lead compensation and calculate the torque value Tref_d. f When setting the phase lead compensation characteristic, n The value of f d It is better to set it smaller than this.

[0094] The torque value Tref_d output from the steering torque compensation value generation unit 230a is added to the torque values Tref_a and Tref_b in addition units 291 and 292 shown in Fig. 18. As a result, the steering torque target value generation unit 200a outputs the steering torque target value Th_ref.

[0095] Fig. 19 is a diagram showing a conceptual operation example of the steering torque target value generation unit according to embodiment 2. In Fig. 19, the horizontal axis represents time, and the vertical axis represents the actual steering angle θh_act. The dashed line in Fig. 19 represents an operation example based on the steering torque target value Th_ref to which the torque value Tref_c, which is the output value of the steering torque compensation value calculation unit 240, has been added, and the solid line represents an operation example based on the steering torque target value Th_ref to which the torque value Tref_d, which has been phase-lead compensated in the phase compensation unit 250, has been added.

[0096] FIG. 19 shows an example in which the driver steers the steering wheel 1 to the right, and at time t_ob_lock an obstacle OB such as a curb makes steering impossible at the actual steering angle θt_act_ob (hereinafter also referred to as "steering lock").

[0097] As shown by the dashed line in FIG. 19, in an example of operation using the steering torque target value Th_ref to which the torque value Tref_c without phase lead compensation is added, there is a possibility that an event will occur in which the steering wheel 1 bounces back after the steering lock occurs.

[0098] In the region where the steering angle deviation θt_err before the occurrence of the steering lock is less than the steering angle deviation threshold θt_err_th (first steering angle deviation threshold θt_err_th1 in the state shown in FIG. 11), the phase compensation filter C f When the steering lock occurs and the steering angle deviation θt_err becomes equal to or greater than the steering angle deviation threshold θt_err_th (first steering angle deviation threshold θt_err_th1 in the state shown in FIG. 11), the phase compensation filter C f The bounce phenomenon of the handle 1 is suppressed by the phase lead compensation by the above.

[0099] In addition, T in the above formula n , T d , i.e., the cutoff frequency f n , f d By adjusting the above, it is possible to realize a more appropriate setting for the rebound phenomenon of the steering wheel 1. Furthermore, the configuration of the phase compensation unit 250 is not limited to the above-mentioned embodiment, and may be, for example, a second-order or higher filter, or may be realized by, for example, PD (proportional differential control).

[0100] Furthermore, the control device 50 of the above-described embodiment may be provided with a limiting unit that limits the upper and lower limits of the steering torque target value Th_ref associated with fluctuations in the torque value Tref_c, which is the output value of the steering torque compensation value calculation unit 240. This makes it possible to suppress the occurrence of abnormalities in each unit (calculated values and detected values within the RAM) in the control of the ECU. The limiting unit may be provided, for example, between the steering torque target value generation unit 200 (200a) and the steering torque control unit 400, or may be included in either the steering torque target value generation unit 200 (200a) or the steering torque control unit 400.

[0101] Furthermore, the drawings used in the above-described embodiments are conceptual diagrams for qualitatively explaining the present disclosure, and are not intended to be limiting. Furthermore, while the above-described embodiment is an example of a preferred embodiment of the present disclosure, the present disclosure is not limited thereto, and various modifications can be made without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0102] 1 handle 2 column axis 3a, 3b tie rod 5L,5R steered wheels 10 Vehicle speed sensor 11 Ignition key 12 Battery 30 Reaction Device 31 Reaction motor 32 Reduction mechanism 33 Steering angle sensor 34 Torque sensor 35 Stopper (rotation limiting mechanism) 40 Steering gear 41 Steering motor 42 Reduction mechanism 43 Angle Sensor 44 Pinion rack mechanism 50 Control device 60 Reaction Force Control System 70 Steering control system 200 Steering torque target value generation unit 210 Basic Map Section 220 Damper torque generating unit 221 Damper gain map section 222 Multiplication section 230 Steering torque compensation value generation unit 240 Steering torque compensation value calculation unit 241, 241a Steering torque compensation value map section 242 Absolute value calculation unit 243 Code extraction part 244 Multiplication Unit 250 Phase compensation section 260 Absolute value calculation unit 270 Differential part 280 Code extraction part 291,292 Addition section 293 Multiplication section 400 Steering torque control unit 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 800 Current control section

Claims

1. A control device for a vehicle steering system including a reaction force device that applies a steering reaction force to a steering wheel in accordance with a steering angle of the steering wheel, and a steering device that steers steered wheels in accordance with the steering angle of the steering wheel, a steering torque target value generating unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force; a steering angle target value generation unit that generates a steering angle target value that is a target value of the steering angle of the steered wheels based on the steering angle; Equipped with The steering torque target value generation unit a steering torque compensation value generation unit that generates a compensation value for the steering torque target value in accordance with a deviation between the steering angle target value and an actual steering angle that is an actual steering angle of the steered wheels, The steering torque compensation value generation unit a steering torque compensation value calculation unit that outputs a first torque value that increases at a first gradient in a first region where the deviation is equal to or greater than a predetermined first threshold; a phase compensation unit that calculates a second torque value by performing phase lead compensation on the first torque value output by the steering torque compensation value calculation unit, The second torque value is set as a compensation value for the steering torque target value. A control device for a vehicle steering system.

2. The first region is delimited by a second threshold value that is greater than the first threshold value; The compensation value is such that the first slope increases as the deviation increases in a region where the deviation is less than the second threshold value, and the first slope is a constant value in a region where the deviation is equal to or greater than the second threshold value.

2. The control device for a vehicle steering system according to claim 1.

3. the compensation value is zero in a second region where the deviation is less than the first threshold.

3. The control device for a vehicle steering system according to claim 1 or 2.

4. the compensation value increases at a second gradient smaller than the first gradient as the deviation increases in a second region where the deviation is less than the first threshold value; 3. The control device for a vehicle steering system according to claim 1 or 2.

5. The phase lead compensation is set by a cutoff frequency that suppresses the bounce phenomenon of the steering wheel in the first region. The control device for a vehicle steering system according to any one of claims 1 to 4.

6. a limiting unit that limits upper and lower limits of the steering torque target value as the compensation value increases; The control device for a vehicle steering system according to any one of claims 1 to 5.

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