Control device of steering system for vehicle

Abstract

To provide a control device of a steering system for a vehicle, the control device allowing for obtaining steering sense reflecting the situation of a road surface or the state of the vehicles.SOLUTION: A steering torque target value generation unit comprises: a steering-reaction-force torque value generation part configured to generate a first torque value increasing or decreasing according to a steering angle; and a road-surface-reaction-force torque value generation part 280 configured to generate a second torque value Tref_d according to a road surface condition. The road-surface-reaction-force torque value generation part 280 is configured to generate: a self-aligning-torque induction torque value Trrf_est, which increases or decreases according to a self-aligning-torque estimated value estimated on the basis of at least a first steering motor current command value Iref_a, and torque reference value Trrf_base, which increases or decreases according to a steering angle; and the second torque value Tref_d on the basis of a torque deviation Trrf_div which is obtained by subtracting the torque reference value Trrf_base from the self-aligning-torque induction torque value Trrf_est. The steering torque target value generation unit at least adds the first torque value and the second torque value Tref_d to generate a steering torque target value.SELECTED DRAWING: Figure 20

Description

[Technical field]

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

[0002] One of the steering systems for vehicles 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 steering mechanism (RWA: Road Wheel Actuator) that steers the steered wheels are mechanically separated. In the SBW system, the steering mechanism and the steering mechanism are electrically connected via a control device (ECU: Electronic Control Unit), and 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.

[0003] In a SBW system in which the steering mechanism and the turning mechanism are mechanically separated, for example, when traveling on a frozen road or a low μ road where the frictional resistance of the road surface is significantly reduced due to hydroplaning in rainy weather, it is necessary to transmit the oversteer or understeer state to a reaction device as a steering reaction force. The following Patent Document 1 discloses a vehicle steering device that estimates a reaction force (self-aligning torque) acting from the road surface and adds it to a reaction force generated according to the steering angle, thereby reflecting the road surface conditions in the steering reaction force. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167661 Summary of the Invention [Problem to be solved by the invention]

[0005] The self-aligning torque varies depending on the road surface conditions as well as vehicle conditions such as vehicle speed and steering angle. In the above-mentioned conventional technology, a target steering torque is generated by adding a torque signal that increases or decreases according to a self-aligning torque estimated value to a torque signal that varies depending on the steering angle and vehicle speed. The self-aligning torque estimated value is estimated based on a motor angle and a motor current command value, but in a situation where tires are expected to slip, the steering angle and vehicle speed become relatively large, so that it may not be possible to obtain a steering feel that reflects the road surface conditions.

[0006] 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 apply a steering reaction force that appropriately reflects road surface conditions. [Means for solving the problem]

[0007] In order to achieve the above object, a control device for a vehicle steering system according to one aspect of the present invention is a control device for a vehicle steering system equipped with a reaction device that drives a reaction motor that applies a steering reaction force to a steering wheel in accordance with a steering angle, and a steering device that drives a steering motor that steers steered wheels in accordance with the steering angle, and is equipped with a steering torque target value generation unit that generates a steering torque target value that is a target value of steering torque of the steering wheel, a steering angle target value generation unit that generates a steering angle target value based on the steering angle, and a steering angle control unit that generates a first steering motor current command value to be supplied to the steering motor based on the steering angle target value, and the steering torque target value generation unit generates a first steering motor current command value that increases or decreases in accordance with at least the steering angle. The steering torque target value generating unit includes a steering reaction torque value generating unit that generates a torque value, and a road surface reaction torque value generating unit that generates a second torque value according to road surface conditions, wherein the road surface reaction torque value generating unit generates a self-aligning torque sensitive torque value that increases or decreases according to a self-aligning torque estimated value estimated based on at least the first steering motor current command value, and a torque reference value that increases or decreases according to at least the steering angle, and generates the second torque value based on a torque deviation obtained by subtracting the torque reference value from the self-aligning torque sensitive torque value, and the steering torque target value generating unit generates the steering torque target value by adding at least the first torque value and the second torque value.

[0008] According to the above configuration, a negative torque component indicating that the tire is slipping is estimated as the torque deviation between the self-aligning torque sensitive torque value and the torque reference value. A negative second torque value generated based on this torque deviation is added to at least the first torque value that increases or decreases according to the steering angle to generate a steering torque target value, thereby making it possible to apply a steering reaction force that appropriately reflects the road surface conditions.

[0009] In a preferred embodiment of the control device for a vehicle steering system, the road reaction torque value generating section increases the self-aligning torque sensitive torque value as the vehicle speed increases.

[0010] In a preferred embodiment of the control device for a vehicle steering system, the road reaction torque value generating section increases the torque reference value as the vehicle speed increases.

[0011] In a preferred embodiment of the control device for a vehicle steering system, the road reaction torque value generating section preferably includes a dead band processing section that sets a minute range of the torque deviation to zero.

[0012] According to the above configuration, minute error components contained in the torque deviation are removed.

[0013] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering torque target value generating unit further includes a torque adjustment gain generating unit that generates a torque gain of 1 or less to be multiplied by at least the first torque value when the torque deviation is a negative value.

[0014] According to the above configuration, when the torque deviation is a negative value, the steering torque target value is reduced, which makes it easier for the driver to feel that the tires are slipping.

[0015] In a preferred embodiment of the control device for a vehicle steering system, the torque adjustment gain generating section preferably reduces the torque gain as the torque deviation increases in a negative value.

[0016] According to the above-described configuration, the amount of decrease in the steering torque target value increases as the torque deviation increases in a negative value, making it possible to apply a steering reaction force that more appropriately reflects the road surface conditions.

[0017] As a desirable aspect of the control device for a vehicle steering system, the steering torque target value generating unit may further include a gain ratio generating unit that generates a first gain to be multiplied by the first torque value and a second gain to be multiplied by the second torque value, the first gain increasing or decreasing depending on at least one of a vehicle speed and a steering angle of the vehicle, and the sum of the first gain and the second gain may be 1.

[0018] As a desirable aspect of the control device for a vehicle steering system, the gain ratio generating section may decrease the first gain as the vehicle speed increases.

[0019] As a desirable aspect of the control device for a vehicle steering system, the gain ratio generating section may decrease the first gain as the steering angle increases.

[0020] As a desirable aspect of the control device for a vehicle steering system, the gain ratio generating section may be configured to decrease the first gain as the steering angle increases.

[0021] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering torque target value generation unit further includes a steering wheel return compensation unit that generates a torque compensation value that increases with an increase in steering angular velocity when the torque deviation is a negative value, and the steering torque target value generation unit further adds the torque compensation value to generate the steering torque target value.

[0022] According to the above configuration, a torque compensation value that suppresses an increase in the steering angular velocity when the tires are slipping is added, and the steering torque target value increases. As a result, the steering torque increases, and accordingly, changes in the steering angle are suppressed. This suppresses tire slippage, making it easier to recover grip.

[0023] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering angle control unit includes a friction compensation unit that calculates different steering motor current compensation values ​​for when the steered wheels are turned to the right and when they are turned to the left, based on the steering angle target value, and the steering angle control unit generates a second steering motor current command value for driving the steering motor, based on the first steering motor current command value and the steering motor current compensation value.

[0024] According to the above configuration, it is possible to effectively perform friction compensation control regardless of the steering speed of the driver, thereby reducing the discomfort felt by the driver when the steering direction of the driver's steering wheel is switched from further turning to returning, or from returning to further turning.

[0025] In a preferred embodiment of the control device for a vehicle steering system, the steering motor current compensation value has a hysteresis characteristic according to a change in the steering angle target value.

[0026] According to the above configuration, different turning motor current compensation values ​​are calculated when the steered wheels are turned to the right and when the steered wheels are turned to the left.

[0027] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering motor current compensation value monotonically increases in a region from a first steering angle target value when steering is started to a second steering angle target value obtained by adding a predetermined steering angle change amount threshold to the first steering angle target value, and becomes a constant value in a region larger than the second steering angle target value.

[0028] According to the above configuration, friction compensation control can be effectively performed from a state in which the steered wheels are stationary, regardless of the driver's steering speed. This makes it possible to reduce the sense of discomfort felt by the driver when the steering direction of the driver's steering is switched from further turning to returning, or from returning to further turning, even in a situation in which the driver's steering operation is extremely slow.

[0029] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the friction compensation section increases or decreases the turning motor current compensation value in response to the second turning motor current command value.

[0030] According to the above configuration, it is possible to realize friction compensation control according to the frictional force caused by the gear torque.

[0031] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the turning motor current compensation value monotonically increases as the second turning motor current command value increases.

[0032] According to the above configuration, it is possible to realize friction compensation control according to the friction force caused by the gear torque that monotonically increases as the second turning motor current command value increases.

[0033] A desirable aspect of the control device for a vehicle steering system includes a current compensation value calculation unit that calculates a first current compensation value, and a current sensitive gain generation unit that generates a gain that monotonically increases as the second steering motor current command value increases, and it is preferable that the friction compensation unit calculates the second current compensation value by multiplying the first current compensation value by the gain.

[0034] According to the above configuration, it is possible to realize friction compensation control according to the friction force caused by the gear torque that monotonically increases as the second turning motor current command value increases.

[0035] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the friction compensation section holds data correlating the second steering motor current command value with a gain that monotonically increases as the second steering motor current command value increases, and calculates the steering motor current compensation value based on the data.

[0036] According to the above configuration, it is possible to realize friction compensation control according to the friction force caused by the gear torque that monotonically increases as the second turning motor current command value increases. Effect of the Invention

[0037] According to the present invention, a steering reaction force corresponding to a road reaction torque estimate can be applied to the steering wheel at a ratio according to the state of the vehicle, thereby providing a control device for a vehicle steering system that enables a steering feel that reflects the road conditions and the state of the vehicle to be obtained. [Brief description of the drawings]

[0038] [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. [Diagram 2] FIG. 2 is a schematic diagram showing a hardware configuration of the ECU. [Diagram 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 angle control unit. [Diagram 5] FIG. 5 is a block diagram showing an example of the configuration of the friction compensation unit. [Figure 6] FIG. 6 is a diagram showing an example of characteristics of the first current compensation value in the current compensation value calculation section. [Figure 7A] FIG. 7A is a diagram showing a first example of a current sensitive gain map. [Figure 7B] FIG. 7B is a diagram showing a second example of a current sensitive gain map. [Figure 8] FIG. 8 is a diagram showing an example of output characteristics of the friction compensation unit. [Figure 9] FIG. 9 is a block diagram showing an example of the configuration of a friction compensation unit according to a modified example. [Figure 10A] FIG. 10A is a first conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. [Figure 10B] FIG. 10B is a first conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. [Figure 11A] FIG. 11A is a second conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. [Figure 11B] FIG. 11B is a second conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. [Figure 12] FIG. 12 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to the first embodiment. [Figure 13] FIG. 13 is a block diagram showing an example of the configuration of the steering reaction torque value generating unit. [Figure 14A] FIG. 14A is a diagram showing an example of the characteristics of the base map. [Figure 14B] FIG. 14B is a diagram showing an example of the characteristics of the torque value Tref_a. [Figure 15] FIG. 15 is a block diagram illustrating an example of the configuration of the damping torque value generating unit according to the first embodiment. As shown in FIG. [Figure 16A] FIG. 16A is a diagram showing an example of characteristics of a damping gain map. [Figure 16B] FIG. 16B is a conceptual diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. [Figure 17] FIG. 17 is a region diagram for explaining the steering direction in the present disclosure. [Figure 18] FIG. 18 is a block diagram illustrating an example of the configuration of the hysteresis compensating unit. [Figure 19] FIG. 19 is a diagram showing an example of the output characteristic of the hysteresis compensator. [Figure 20] FIG. 20 is a block diagram illustrating an example of the configuration of the road surface reaction torque value generating unit according to the first embodiment. [Figure 21] FIG. 21 is a block diagram showing an example of the configuration of the SAT responsive torque value generating unit. [Figure 22] FIG. 22 is an image diagram showing the state of torque generated between the road surface and the steering motor. [Diagram 23] FIG. 23 is a block diagram illustrating an example of the configuration of the SAT estimation unit. [Figure 24] FIG. 24 is a conceptual diagram for explaining a method for calculating the actual self-aligning torque acting on the steering mechanism. [Diagram 25] FIG. 25 is a conceptual diagram showing a configuration for executing a simulation for deriving the transfer function Gfil. [Figure 26A] FIG. 26A is a diagram showing an example of a characteristic of the SAT sensitive torque map. [Figure 26B] FIG. 26B is a diagram conceptually showing an example of the characteristics of the self-aligning torque sensitive torque value Trrf_est after sign conversion. [Figure 27] FIG. 27 is a block diagram showing an example of the configuration of the torque reference value generating unit. [Figure 28A] FIG. 28A is a diagram showing an example of characteristics of the torque reference map. [Figure 28B] FIG. 28B is a diagram showing an example of the characteristics of the torque reference value Trrf_base. [Figure 29] FIG. 29 is a diagram showing an example of output characteristics of the dead zone processing unit. [Diagram 30] FIG. 30 is a diagram showing an example of the characteristics of a vehicle speed sensitive gain map. [Diagram 31] FIG. 31 is a block diagram illustrating an example of the configuration of the torque adjustment gain generating unit according to the first embodiment. [Figure 32A] FIG. 32A is a diagram showing a first characteristic example of a torque sensing gain map. [Figure 32B] FIG. 32B is a diagram showing a second characteristic example of the torque sensing gain map. [Figure 32C] FIG. 32C is a diagram showing a third characteristic example of the torque sensing gain map. [Fig. 32D] FIG. 32D is a diagram showing a fourth characteristic example of the torque sensing gain map. [Diagram 33] FIG. 33 is a diagram illustrating an example of the behavior of the control device of the vehicle steering system according to the first embodiment. [Diagram 34] FIG. 34 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to a modified example of the first embodiment. [Diagram 35] FIG. 35 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to the second embodiment. [Figure 36A] FIG. 36A is a diagram conceptually showing a first example of a gain ratio setting example when the vehicle speed is used as a parameter. [Figure 36B] FIG. 36B is a diagram conceptually showing a second example of a gain ratio setting example when the vehicle speed is used as a parameter. [Figure 36C] FIG. 36C is a diagram conceptually showing a third example of gain ratio setting when the vehicle speed is used as a parameter. [Figure 37]FIG. 37 is a diagram conceptually showing an example of a gain ratio setting example when the actual steering angle is used as a parameter. [Figure 38] FIG. 38 is a diagram conceptually showing an example of a gain ratio setting example when the actual steering angle is used as a parameter. [Figure 39] FIG. 39 is a block diagram showing an example of the configuration of the gain ratio generating section when the vehicle speed and the actual steering angle are used as parameters. [Figure 40A] FIG. 40A is a diagram conceptually showing an example of a gain ratio setting example using vehicle speed as a parameter. [Figure 40B] FIG. 40B is a diagram conceptually showing an example of a gain ratio setting example using the actual steering angle as a parameter. [Diagram 41] FIG. 41 is a block diagram showing an example of the configuration of a gain ratio generating section when the vehicle speed and the actual steering angle are used as parameters. [Figure 42A] FIG. 42A is a diagram conceptually showing an example of a gain ratio setting example using vehicle speed as a parameter. [Figure 42B] FIG. 42B is a diagram conceptually showing an example of a gain ratio setting example using the actual steering angle as a parameter. [Diagram 43] FIG. 43 is a 3D map conceptually illustrating an example of a gain ratio generation technique. [Diagram 44] FIG. 44 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to the third embodiment. [Diagram 45] FIG. 45 is a block diagram illustrating an example of the configuration of a torque adjustment gain generating unit according to the third embodiment. [Diagram 46] FIG. 46 is a block diagram showing a configuration example of the steering return compensation unit. [Figure 47] FIG. 47 is a diagram showing an example of the characteristics of a steering angle velocity sensitive gain map. [Figure 48] FIG. 48 is a diagram conceptually illustrating an example of the behavior of the control device of the vehicle steering system according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Hereinafter, a mode for carrying out the invention (hereinafter, referred to as an embodiment) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiment. Furthermore, the components in the following embodiment include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiment can be appropriately combined.

[0040] 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. The system includes a reaction device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering the steered wheels, and a control device 50 for controlling both devices.

[0041] 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 operation of the steering wheel 1 by the driver as an electrical signal, specifically, the steering angle θh output from the reaction force device 30 as an electrical signal.

[0042] The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotation speed of the reaction force motor 31. The reaction force device 30 transmits the vehicle's motion state transmitted from the steered wheels 5L, 5R to the driver as a steering reaction force. The reaction force motor 31 imparts the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

[0043] 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."

[0044] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point that 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.

[0045] The steering device 40 includes a steering motor 41, a speed reducing 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 response to the steering angle θh, and imparts the driving force to the pinion rack mechanism 44 via the speed reducing mechanism 42, and steers the steered wheels 5L, 5R 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. Instead of the steering angle θt of the steered wheels 5L, 5R, for example, a motor angle of the steering motor 41 or a position of a rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 is also referred to as the "actual steering angle θt_act".

[0046] In this disclosure, the actual steering angle θh_act and the actual turning angle θt_act are collectively referred to simply as the "steering angle" of the vehicle.

[0047] In order to coordinately 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 the turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

[0048] 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.

[0049] 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 a hardware configuration of an ECU. As shown in FIG. 2, the control device 50 of the vehicle steering system according to the embodiment includes a control computer (Electronic Control Unit, hereinafter also referred to as "ECU") 110.

[0050] ECU 110 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an EEPROM (Electrically Erasable Programmable ROM) 104, etc., which are connected to a bus 105. CPU 101 executes a control program stored in ROM 102. Reaction force device 30 and steering device 40 are cooperatively controlled by a control program executed mainly by ECU 110. Note that control device 50 may be configured as one ECU, or may include a reaction force control ECU that controls reaction force device 30 and a steering control ECU that controls steering device 40.

[0051] The ROM 102 is used as a memory for storing the control program and the control data used when the control program is executed, and the RAM 103 is used as a work memory for running the control program.

[0052] The EEPROM 104 is a non-volatile memory capable of retaining memory contents even after power is cut off, and stores control data and the like used by the CPU 101 to execute a control program. The various data stored in the EEPROM 104 is used in the control program expanded in the RAM 103 after power is applied to the ECU 110, and is overwritten in the EEPROM 104 at a predetermined timing. Note that, although an EEPROM is used as the non-volatile memory here, the present invention is not limited to this, and other non-volatile memories such as FLASH-ROM (registered trademark), SDRAM, etc. may also be used.

[0053] 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, the reaction force device 30 includes a reaction force motor 31 and the above-mentioned configuration, as well as a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. The steering device 40 includes a PWM control unit 47, an inverter 48, and a motor current detector 49, as well as a steering motor 41 and the above-mentioned configuration. The control device 50 realizes each control block of a reaction force control system 60 that controls the reaction force device 30, and a steering control system 70 that controls the steering device 40. The reaction force control system 60 and the steering control system 70 cooperate with each other to control the reaction force device 30 and the steering device 40. When the control device 50 includes a reaction force control ECU and a steering control ECU, the reaction force control system 60 may be realized by the reaction force control ECU, and the steering control system 70 may be realized by the steering control ECU. In this case, the reaction force control system 60 in the following description may be read as a reaction force control ECU, and the turning control system 70 may be read as a turning control ECU.

[0054] Each control block in reaction force control system 60 is realized by a reaction force control program executed in ECU 110. Also, each control block in steering control system 70 is realized by a steering control program executed in ECU 110. Note that some or all of the control blocks of control device 50 may be realized by hardware. Also, a mode in which control device 50 includes PWM control unit 37, inverter 38, motor current detector 39, PWM control unit 47, inverter 48, and motor current detector 49 may be used.

[0055] 3, control device 50 includes, as control blocks, steering torque target value generation section 200, steering torque control section 400, current control section 500, steering angle target value generation section 600, steering 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 constitute reaction force control system 60. Steering angle target value generation section 600, steering angle control section 700, and current control section 800 are control blocks that constitute steering control system 70.

[0056] The reaction force control system 60 performs control so that the actual steering torque Th_act detected by the torque sensor 34 follows a steering torque target value Th_ref, which is a target value of the steering torque of the reaction force device 30.

[0057] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0058] The steering torque control unit 400 generates a reaction force motor current command value Ih_ref for driving the reaction force motor 31. The steering torque control unit 400 generates a current command value such that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero, and limits the upper and lower limits of the current command value by an output limiting unit to calculate the reaction force motor current command value Ih_ref.

[0059] The current control unit 500 performs current control 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 reaction force 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.

[0060] 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.

[0061] The steering control system 70 performs control so that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

[0062] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0063] Steering angle control section 700 generates second steering motor current command value It_ref for driving steering motor 41. Specifically, steering angle control section 700 generates first steering motor current command value Iref_a, which is a control target value of a current supplied to steering motor 41, such that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero, and performs friction compensation control by a friction compensation section for the first steering motor current command value Iref_a to calculate second steering motor current command value It_ref. Below, an example in which a friction compensation section is provided in steering angle control section 700 will be described, but a configuration not including a friction compensation section may also be used. Note that in a configuration not including a friction compensation section, the first steering motor current command value Iref_a after PID control is generated as the second steering motor current command value It_ref.

[0064] Current control unit 800 performs current control of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that a deviation It_err between second steering motor current command value It_ref output from steering angle control unit 700 and an actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0065] In the steering device 40, the steering motor 41 is driven and controlled via a PWM control unit 47 and an inverter 48 based on the voltage control command value Vt_ref.

[0066] In this embodiment, the steering torque control unit 400, the current control unit 500, the steering angle target value generating unit 600, and the current control unit 800 need only be configured to realize each control in the reaction force control system 60 or the steering control system 70, and are not limited by the configuration of each of these control blocks.

[0067] Here, the steering angle control unit 700 will be described. Fig. 4 is a block diagram showing an example of the configuration of the steering angle control unit. As shown in Fig. 4, the steering angle control unit 700 includes a feedforward compensation unit 710, a PID control unit 730, a stabilization compensation unit 740, an output limiting unit 760, a friction compensation unit 770, and addition units 720, 750.

[0068] Feedforward compensation section 710 is composed of a filter (FF filter) for improving the tracking of actual steering angle θt_act with respect to steering angle target value θt_ref. Feedforward compensation section 710 performs filtering on steering angle target value θt_ref. Specifically, for example, an LPF having a first-order or second-order lag transfer function is used, and the LPF is designed so that the time delay caused by the filtering process by the LPF is equivalent to the tracking delay of actual steering angle θt_act with respect to steering angle target value θt_ref.

[0069] PID control section 730 performs PID control so that deviation θt_err between steering angle target value θt_ref, which is the calculation result of addition section 720, and actual steering angle θt_act approaches zero.

[0070] The stabilization compensation unit 740 is configured with a filter (stabilization filter) having a transfer characteristic required for stabilizing control. The stabilization compensation unit 740 performs a filter process on the output value of the PID control unit 730.

[0071] Output limiting section 760 performs output limiting processing on current command value Iref_c, which is the calculation result of addition section 750, and outputs second turning motor current command value It_ref. Upper and lower limit values ​​for current command value Iref_c are set in advance in output limiting section 760. Output limiting section 760 limits the upper and lower limit values ​​of current command value Iref_c, and outputs second turning motor current command value It_ref.

[0072] It should be noted that the above-mentioned feedforward compensation section 710 and stabilization compensation section 740 are not necessarily required components, and for example, either one or both of the feedforward compensation section 710 and the stabilization compensation section 740 may be omitted.

[0073] Friction compensation unit 770 calculates a second current compensation value Iref_b for compensating for a delay in the response of actual steering angle θt_act to steering angle target value θt_ref caused by friction in the steering mechanism, based on steering angle target value θt_ref. The specific configuration and operation of friction compensation unit 770 will be described in detail below.

[0074] Fig. 5 is a block diagram showing a configuration example of a friction compensation unit 770. As shown in Fig. 5, the friction compensation unit 770 includes a current compensation value calculation unit 771 and a current sensitive gain generation unit 773 as main components.

[0075] The turning angle target value θt_ref and the turning speed target value ωt_ref calculated by differentiating the turning angle target value θt_ref by differentiating section 772 are input to current compensation value calculation section 771. Current compensation value calculation section 771 calculates a first current compensation value Iref_b0 based on the turning angle target value θt_ref and the turning speed target value ωt_ref.

[0076] A method for calculating the first current compensation value Iref_b0 in the current compensation value calculation section 771 will be described below.

[0077] FIG. 6 is a diagram showing an example of the characteristics of the first current compensation value in the current compensation value calculation unit. In FIG. 6, the horizontal axis indicates the steering angle target value θt_ref, and the vertical axis indicates the first current compensation value Iref_b0. In addition, in FIG. 6, the solid line indicates the first current compensation value Iref_b0 when steering to the right, and the dashed line indicates the first current compensation value Iref_b0 when steering to the left. As shown in FIG. 6, the first current compensation value Iref_b0 calculated in the current compensation value calculation unit 771 has a hysteresis characteristic that becomes a different value when steering to the left and when steering to the left. L1 shown in FIG. 6 indicates the trajectory when steering to the right from the center position (origin (0,0)) of the steered wheels 5L, 5R, L2 indicates the trajectory when switching from right steering to left steering occurs at the coordinate A (x1, y1), and L3 indicates the trajectory when switching from right steering to left steering occurs at the coordinate B (x2, y2).

[0078] Current compensation value calculation unit 771 calculates the first current compensation value Iref_b0 using the following equations (1) and (2) based on the turning angle target value θt_ref and the turning speed target value ωt_ref. Specifically, when the sign ωt_ref(sgn) of the turning speed target value ωt_ref is a positive value ("+"), the first current compensation value Iref_b0 is calculated using the following equation (1), and when the sign ωt_ref(sgn) of the turning speed target value ωt_ref is a negative value ("-"), the first current compensation value Iref_b0 is calculated using the following equation (2). In the following equations (1) and (2), x is the turning speed target value ωt_ref, y is the R is the first current compensation value Iref_b0 when steering to the right, y L is the first current compensation value Iref_b0 when steering to the left. Furthermore, the coefficient a is a value greater than 1, and the coefficient c is a value greater than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic (the width of the first current compensation value Iref_b0), and the coefficient c is a coefficient representing the roundness of the hysteresis characteristic.

[0079] y R=Ahys{1-a -c(x-b)}···(1)

[0080] y L =-Ahys{1-a c(x-b’)}···(2)

[0081] That is, when steering to the right (ωt_ref(sgn)="+"), the current compensation value calculation unit 771 calculates the first current compensation value Iref_b0(y R ) is calculated, and when steering to the left (ωt_ref(sgn) = "-"), the first current compensation value Iref_b0(y L ) is calculated.

[0082] When a switch from right steering to left steering occurs (ωt_ref(sgn) = "+" → "-"), or when a switch from left steering to right steering occurs (ωt_ref(sgn) = "-" → "+"), current compensation value calculation unit 771 takes over the previous values ​​of steering angle target value θt_ref and first current compensation value Iref_b0, and substitutes coefficient b or b' shown in equation (3) or (4) below into equation (1) or (2) above that is applied after the steering switch. This maintains continuity before and after the steering switch. Specifically, when a switch from right steering to left steering occurs (ωt_ref(sgn)=“+”→“-”), current compensation value calculation unit 771 applies the steering angle target value θt_ref and the previous value of first current compensation value Iref_b0 (coordinate A(x1,y1) shown in FIG. 6) to the above equation (2), and substitutes coefficient b' shown in the following equation (4) to calculate first current compensation value Iref_b0. Also, when a switch from left steering to right steering occurs (ωt_ref(sgn)=“-”→“+”), current compensation value calculation unit 771 applies the steering angle target value θt_ref and the previous value of first current compensation value Iref_b0 (coordinate B(x2,y2) shown in FIG. 6) to the above equation (1), and substitutes coefficient b shown in the following equation (3) to calculate first current compensation value Iref_b0.

[0083] b=x1+(1 / c)log a {1-(y1 / Ahys)}···(3)

[0084] b'=x1-(1 / c)log a {1-(y1 / Ahys)}···(4)

[0085] The above formulas (3) and (4) are obtained by substituting x1 for x in the above formulas (1) and (2) and R and y L It can be derived by substituting y1 into

[0086] When, for example, Napier's constant e is used as the coefficient a, the above formulas (1), (2), (3), and (4) can be expressed as the following formulas (5), (6), (7), and (8), respectively.

[0087] y R =Ahys[1-exp{-c(xb)}] (5)

[0088] y L =-Ahys[{1-exp{c(x-b')}]···(6)

[0089] b=x1+(1 / c)log e {1-(y1 / Ahys)}···(7)

[0090] b'=x1-(1 / c)log e {1-(y1 / Ahys)}···(8)

[0091] Returning to Fig. 5, previous value holding section 774 holds a previous output value It_ref' of steering angle control section 700. Specifically, previous output value It_ref' is second steering motor current command value It_ref in the previous process. Previous value holding section 774 is constituted by, for example, a RAM of an ECU constituting control device 50.

[0092] In the present disclosure, absolute value calculation section 775 performs absolute value processing of the previous output value It_ref′ of steering angle control section 700 outputted from previous value holding section 774 .

[0093] The previous output value |It_ref'| of steering angle control unit 700 that has been subjected to absolute value processing in absolute value calculation unit 775 is input to current sensitive gain generation unit 773. Current sensitive gain generation unit 773 generates gain Gi according to the previous output value |It_ref'| of steering angle control unit 700.

[0094] Current sensitive gain generation section 773 has a current sensitive gain map in which gain Gi is set according to previous output value |It_ref'| of steering angle control section 700. The current sensitive gain map is stored, for example, in the ROM of the ECU constituting control device 50. Fig. 7A is a diagram showing a first example of the current sensitive gain map. Fig. 7B is a diagram showing a second example of the current sensitive gain map.

[0095] The first example of the current-sensitive gain map shown in Fig. 7A has a current-value-sensitive characteristic in which gain Gi increases or decreases according to the previous output value |It_ref'| of steering angle control unit 700. More specifically, as shown in Fig. 7A, gain Gi increases monotonically as the previous output value |It_ref'| of steering angle control unit 700 increases.

[0096] Fig. 8 is a diagram showing an example of the output characteristic of the friction compensation unit. In Fig. 8, the horizontal axis represents the target steering angle value θt_ref, and the vertical axis represents the second current compensation value Iref_b.

[0097] The frictional force generated in the steering mechanism includes friction due to gear torque interposed between steering motor 41 and reduction mechanism 42. The gear torque refers to torque caused by frictional force generated in the mechanical elements of the reduction gear. For example, in the case of a worm reduction gear, the frictional torque caused by frictional force generated in the meshing portion between the worm gear and the worm wheel can be defined as the gear torque. The frictional force due to this gear torque increases monotonically with the motor current.

[0098] In the present disclosure, friction compensation section 770 multiplies (multiplication section 776) the first current compensation value Iref_b0 output from current compensation value calculation section 771 by the gain Gi generated by current sensitive gain generation section 773 to calculate second current compensation value Iref_b. As a result, as shown in Fig. 8, a characteristic is obtained in which the output width of the hysteresis characteristic (width of the second current compensation value Iref_b) increases and decreases according to the second turning motor current command value It_ref, and friction compensation control according to the frictional force caused by the gear torque can be realized.

[0099] Specifically, when the second turning motor current command value It_ref is relatively large, the gear torque becomes relatively large and the frictional force caused by the gear torque acts strongly. Under such circumstances, by multiplying the first current compensation value Iref_b0 output from current compensation value calculation section 771 by a gain Gi_H that is relatively larger than gain Gi_M, it is possible to increase the output width of the hysteresis characteristic (width of second current compensation value Iref_b), as shown by the dashed line.

[0100] Furthermore, when the second turning motor current command value It_ref is relatively small, the gear torque becomes relatively small and the frictional force caused by the gear torque becomes small. Under such circumstances, by multiplying the first current compensation value Iref_b0 output from current compensation value calculation section 771 by a gain Gi_L that is relatively smaller than gain Gi_M, it is possible to narrow the output width of the hysteresis characteristic (width of second current compensation value Iref_b) as shown by the dashed dotted line.

[0101] The mode of the current sensitive gain map is not limited to the mode of the first example shown in Fig. 7A. For example, as in the second example shown in Fig. 7B, the second current compensation value Iref_b may be calculated by multiplying the first current compensation value Iref_b0 output from current compensation value calculation section 771 by a constant gain Gi=k (for example, k=1) regardless of the second turning motor current command value It_ref (previous output value |It_ref'| of turning angle control section 700).

[0102] The second current compensation value Iref_b output from friction compensation section 770 is added to the first turning motor current command value Iref_a output from stabilization compensation section 740 by addition section 750 shown in FIG. 4, and the second turning motor current command value It_ref, which is output-limited by output limiting section 760 with respect to the current command value Iref_c after addition, is output.

[0103] FIG. 9 is a block diagram showing an example of the configuration of a friction compensation section according to a modified example. In the example of the configuration of friction compensation section 770a shown in FIG. 5, the first current compensation value Iref_b0 output from current compensation value calculation section 771 is multiplied by gain Gi generated by current sensitive gain generation section 773. However, in the modified example shown in FIG. 9, current compensation value calculation section 771a may be configured to hold a table (data) in which second turning motor current command value It_ref (previous output value |It_ref'| of turning angle control section 700) is associated with coefficient Ahys in the above expressions (6) to (13), and to obtain a characteristic in which the output width (width of second current compensation value Iref_b) of the hysteresis characteristic increases and decreases according to second turning motor current command value It_ref, as shown in FIG. 8. The data can be stored, for example, in the ROM of the ECU constituting control device 50, in the same way as the current sensitive gain map. Thereby, friction compensation control according to the frictional force caused by the gear torque can be realized in the same way as the configuration shown in FIG. 5.

[0104] Note that the present invention is not limited to the aspect of obtaining the steering speed target value ωt_ref by differentiating the steering angle target value θt_ref, and may be an aspect of determining that the steering direction has been switched using the motor angular velocity of the steering motor 41. Also, a configuration may be provided in which a filter is provided in front of the current compensation value calculation section 771 and the current sensitive gain generation section 773, or a configuration may be provided in the rear of the current sensitive gain generation section 773. Furthermore, a configuration may be provided in which a limiter that performs output limiting processing on the second current compensation value Iref_b is provided in the rear of the friction compensation section 770, similar to the above-mentioned output limiting section 760.

[0105] Figures 10A and 10B are first conceptual diagrams for explaining a specific example of friction compensation control by the friction compensation unit. In Figures 10A and 10B, the horizontal axis indicates time, and the vertical axis indicates steering angle. The dashed lines in Figures 10A and 10B indicate steering angle target value θt_ref, and the solid lines indicate actual steering angle θt_act. Figure 10A illustrates a time response when friction compensation control is not performed by friction compensation unit 770. Figure 10B illustrates a time response when friction compensation control is performed by friction compensation unit 770.

[0106] The examples shown in Fig. 10A and Fig. 10B show time responses when the steered wheels 5L, 5R are steered left and right from the center position at a relatively fast predetermined frequency. When friction compensation control by the friction compensation unit 770 is not performed, as shown in Fig. 10A, distortion occurs in the actual steering angle θt_act when the steering direction is switched as enclosed by the dashed line. In this case, when the driver switches the steering direction from turning the steering wheel further to turning it back, or from turning it back to turning it further, a deviation occurs between the operation (steering) of the steering wheel 1 and the steering of the steered wheels 5L, 5R, which may give the driver a sense of discomfort. In contrast, when friction compensation control by the friction compensation unit 770 is performed, distortion of the actual steering angle θt_act is suppressed when the steering direction is switched as enclosed by the dashed line, as shown in Fig. 10B.

[0107] To explain in more detail, when the steering direction is changed, when the steering angle target value θt_ref is changed, the steering speed target value ωt_ref becomes approximately zero. However, since the first current compensation value Iref_b0 is determined according to the steering angle target value θt_ref, the friction compensation unit 770 can perform a predetermined friction compensation control even when the steering speed target value ωt_ref is approximately zero.

[0108] This makes it possible to reduce the sense of discomfort felt by the driver when the steering direction of the driver's steering wheel is switched from further turning to returning, or when the steering direction is switched from returning to further turning.

[0109] 11A and 11B are second conceptual diagrams for explaining a specific example of friction compensation control by the friction compensation unit. In FIG. 11A and FIG. 11B, the horizontal axis indicates time, and the vertical axis indicates the steering angle. The dashed lines in FIG. 11A and FIG. 11B indicate the steering angle target value θt_ref, and the solid lines indicate the actual steering angle θt_act. FIG. 11A illustrates a time response when friction compensation control is performed according to the steering speed target value ωt_ref, as a comparative example of friction compensation control according to the embodiment. FIG. 11B illustrates a time response when friction compensation control is performed by friction compensation unit 770.

[0110] The examples shown in Figures 11A and 11B show time responses when steering to the left or right more minutely than in Figures 10A and 10B. When friction compensation control according to steering speed target value ωt_ref according to the comparative example is performed, as shown in Figure 11A, when steering to the left or right is performed slightly, distortion occurs in actual steering angle θt_act when the steering direction is switched as surrounded by a dashed line. In contrast, when friction compensation control is performed by friction compensation unit 770, as shown in Figure 11B, distortion of actual steering angle θt_act is suppressed when the steering direction is switched as surrounded by a dashed line, even when steering to the left or right is performed slightly.

[0111] To explain in more detail, if the steering wheel is operated slowly, minutely and slowly, when the steering direction is switched, as in the example of Figures 10A and 10B, when the steering angle target value θt_ref switches, the steering speed target value ωt_ref becomes approximately zero. Here, unlike the example of Figures 10A and 10B, the steering angle target value θt_ref also takes a value close to zero, so that the first current compensation value Iref_b0 output from current compensation value calculation unit 771 also has a small value, but by multiplying the first current compensation value Iref_b0 by the gain Gi calculated by current sensitive gain generation unit 773, it is possible to prevent the second current compensation value Iref_b from becoming too small.

[0112] This reduces the sense of discomfort felt by the driver when the steering direction is changed from further turning to returning, or from returning to further turning, even in a situation where the driver's steering operation is slight.

[0113] As described above, steering angle control unit 700 is equipped with friction compensation unit 770 and is configured to calculate second current compensation value Iref_b based on steering angle target value θt_ref to compensate for the delay in tracking of actual steering angle θt_act to steering angle target value θt_ref caused by friction in the steering mechanism, thereby enabling effective and appropriate friction compensation control to be performed regardless of the driver's steering wheel operation speed.

[0114] Also, as described above, by setting the second current compensation value Iref_b to have characteristics that increase or decrease according to the second turning motor current command value It_ref, it is possible to realize friction compensation control according to the friction force caused by the gear torque.

[0115] (Embodiment 1) Hereinafter, the steering torque target value generating unit 200 according to the embodiment 1 will be described. Fig. 12 is a block diagram showing a configuration example of the steering torque target value generating unit according to the embodiment 1. As shown in Fig. 12, the steering torque target value generating unit 200 according to the embodiment 1 includes, as main components, a steering reaction torque value generating unit 210, a damping torque value generating unit 240, a hysteresis compensating unit 250, a road reaction torque value generating unit 280, and a torque adjustment gain generating unit 290.

[0116] First, the steering reaction torque value generating unit 210 will be described with reference to Figures 13, 14A and 14B. Figure 13 is a block diagram showing an example of the configuration of the steering reaction torque value generating unit.

[0117] In the present disclosure, the sign extraction unit 213 shown in Fig. 13 extracts the sign of the actual steering angle θh_act. Specifically, for example, the value of the actual steering angle θh_a is divided by the absolute value of the actual steering angle θh_a. As a result, the sign extraction unit 213 outputs "1" when the sign of the actual steering angle θh_act is "+", and outputs "-1" when the sign of the actual steering angle θh_act is "-". Specifically, the sign extraction unit 213 generates, for example, a sign function Sgn(θh) of the actual steering angle θh_act.

[0118] Fig. 14A is a diagram showing an example of the characteristics of the basic map. The steering angle |θh| and the vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation unit 212 are input to the steering reaction torque map unit 211. The steering reaction torque value generation unit 210 generates a torque value Tref_a0 using the vehicle speed Vs as a parameter, using the basic map shown in Fig. 14A. The torque value Tref_a0 is used to generate a basic steering reaction according to the steering angle |θh| and the vehicle speed Vs.

[0119] The torque value Tref_a0 has an angle-sensitive characteristic that increases and decreases according to the steering angle |θh|. More specifically, the torque value Tref_a0 increases as the steering angle |θh| increases, as shown in FIG. 14A. Also, the torque value Tref_a0 has a vehicle-speed-sensitive characteristic that increases and decreases according to the vehicle speed Vs. More specifically, the torque value Tref_a0 increases as the vehicle speed Vs increases, as shown in FIG. 14A. That is, the reaction force obtained by the torque value Tref_a0 derived by the basic map shown in FIG. 14A increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and increases as the vehicle speed (vehicle speed Vs) increases. Note that the basic map shown in FIG. 14A has a vehicle-speed-sensitive characteristic, but is not limited thereto.

[0120] Fig. 14B is a diagram showing an example of the characteristics of the torque value Tref_a. The torque value Tref_a0 output from the steering reaction force torque map unit 211 is multiplied by the sign function Sgn(θh) output from the sign extraction unit 213 in the multiplication unit 293 to obtain the torque value Tref_a (first torque value) shown in Fig. 14B. Note that a configuration without the sign extraction unit 213 may be used in which the torque value Tref_a (first torque value) is obtained using a basic map corresponding to the positive and negative steering angles θh as shown in Fig. 14B.

[0121] Next, the damping torque value generating unit 240 will be described with reference to Fig. 15, Fig. 16A and Fig. 16B. Fig. 15 is a block diagram showing an example of the configuration of the damping torque value generating unit according to the first embodiment.

[0122] The damping torque value generating unit 240 includes a damping gain map unit 241, a differentiation unit 242, and a multiplication unit 243. Fig. 16A is a diagram showing an example of a characteristic of the damping gain map. The vehicle speed Vs is input to the damping gain map unit 241. The damping gain map unit 241 generates the damping gain DG by using the damping gain map shown in Fig. 16A.

[0123] The damping gain DG has a vehicle speed-sensitive characteristic that increases and decreases according to the vehicle speed Vs, as shown in Fig. 16A. The damping torque value generating unit 240 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 in a differentiating unit 242 by the damper gain DG output from the damping gain map unit 241 in a multiplier 243, and outputs the result as a torque value Tref_b.

[0124] By adding the torque value Tref_b output from the damping torque value generation unit 240 to the torque value Tref_a (first torque value) output from the steering reaction force torque value generation unit 210, it becomes possible to compensate for the steering reaction force proportional to the steering angular velocity ωh.

[0125] Fig. 16B is a conceptual diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. In Fig. 16B, 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). In Fig. 16B, the dashed line indicates the torque value Tref_a (first torque value).

[0126] Fig. 17 is a region diagram for explaining the steering direction in the present disclosure, in which the horizontal axis indicates the steering angle θh, and the vertical axis indicates the steering angular velocity ωh.

[0127] Area A ((θh,ωh)=(+,+)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the right (θh>0) and is turned further to the right (ωh>0). Area B ((θh,ωh)=(+,-)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the right (θh>0) and is turned back to the left (ωh<0). Area C ((θh,ωh)=(-,-)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the left (θh<0) and is turned further to the left (ωh<0). Area D ((θh,ωh)=(-,+)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the left (θh<0) and is turned back to the right (ωh>0). Also, in Figure 17, 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)).

[0128] The torque value Tref_b output from the damping torque value generating unit 240 is a positive value in regions A and D where the steering angle velocity ωh>0, and is a negative value in regions B and C where the steering angle velocity ωh<0. As a result, when the steering angle 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 added to Tref_a as shown by the solid line in Fig. 16B. When the steering angle 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_a is subtracted by |Tref_b| as shown by the dashed line in Fig. 16B.

[0129] 16B, the torque value Tref_a+Tref_b increases in increment of torque relative to a change in 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.

[0130] Next, the hysteresis compensation section 250 will be described with reference to Fig. 18 and Fig. 19. Fig. 18 is a block diagram showing an example of the configuration of the hysteresis compensation section.

[0131] The actual steering angle θh_act and the steering angular velocity ωh_act calculated by differentiating the actual steering angle θh_act by a differentiation section 252 are input to the hysteresis compensation value calculation section 251. The hysteresis compensation value calculation section 251 calculates a torque compensation value Tref_c based on the actual steering angle θh_act and the steering angular velocity ωh_act. Hereinafter, a method of calculating the torque compensation value Tref_c in the hysteresis compensation value calculation section 251 will be described.

[0132] FIG. 19 is a diagram showing an example of the output characteristic of the hysteresis compensation unit. In FIG. 19, the horizontal axis indicates the actual steering angle θh_act, and the vertical axis indicates the torque compensation value Tref_c. In FIG. 19, the solid line indicates the torque compensation value Tref_c when steering to the right, and the dashed line indicates the torque compensation value Tref_c when steering to the left. As shown in FIG. 19, the torque compensation value Tref_c calculated in the hysteresis compensation value calculation unit 251 has a hysteresis characteristic that is a different value when steering to the left and when steering to the left. L1 shown in FIG. 19 indicates the trajectory when steering to the right from the center position (origin (0,0)) of the steering wheel 1, L2 indicates the trajectory when switching from right steering to left steering occurs at the coordinate A (x1, y1), and L3 indicates the trajectory when switching from right steering to left steering occurs at the coordinate B (x2, y2).

[0133] The hysteresis compensation value calculation unit 251 calculates the torque compensation value Tref_c using the following equations (9) and (10) based on the actual steering angle θh_act and the steering angular velocity ωh_act. Specifically, when the sign ωh_act(sgn) of the steering angular velocity ωh_act is a positive value ("+"), the torque compensation value Tref_c is calculated using the following equation (9), and when the sign ωh_act(sgn) of the steering angular velocity ωh_act is a negative value ("-"), the torque compensation value Tref_c is calculated using the following equation (10). In the following equations (9) and (10), x represents the steering angular velocity ωh_act, y represents the R is the torque compensation value Tref_c when steering to the right, y L is the torque compensation value Tref_c during left steering. The coefficient a is a value greater than 1, and the coefficient c is a value greater than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic (the width of the torque compensation value Tref_c), and the coefficient c is a coefficient representing the roundness of the hysteresis characteristic.

[0134] y R =Ahys{1-a -c(x-b)}···(9)

[0135] y L =-Ahys{1-a c(x-b’)}···(10)

[0136] That is, when steering to the right (ωh_act(sgn)="+"), the hysteresis compensation value calculation unit 251 calculates the torque compensation value Tref_c(y R ) is calculated, and when steering to the left (ωh_act(sgn) = "-"), the torque compensation value Tref_c(y L ) is calculated.

[0137] When a switch from right steering to left steering occurs (ωh_act(sgn) = "+" → "-"), or when a switch from left steering to right steering occurs (ωh_act(sgn) = "-" → "+"), the hysteresis compensation value calculation unit 251 takes over the previous values ​​of the actual steering angle θh_act and the torque compensation value Tref_c, and substitutes the coefficient b or b' shown in the following equation (11) or (12) into the above equation (9) or (10) that is applied after the steering switch. This maintains continuity before and after the steering switch. Specifically, when a switch from right steering to left steering occurs (ωh_act(sgn)=“+”→“-”), the hysteresis compensation value calculation unit 251 applies the actual steering angle θh_act and the previous value of the torque compensation value Tref_c (coordinate A(x1,y1) shown in FIG. 19) to the above equation (10), and substitutes the coefficient b′ shown in the following equation (12) to calculate the torque compensation value Tref_c. Also, when a switch from left steering to right steering occurs (ωh_act(sgn)=“-”→“+”), the hysteresis compensation value calculation unit 251 applies the actual steering angle θh_act and the previous value of the torque compensation value Tref_c (coordinate B(x2,y2) shown in FIG. 19) to the above equation (9), and substitutes the coefficient b shown in the following equation (11) to calculate the torque compensation value Tref_c.

[0138] b=x1+(1 / c)log a {1-(y1 / Ahys)}···(11)

[0139] b'=x1-(1 / c)log a {1-(y1 / Ahys)}···(12)

[0140] The above formulas (11) and (12) are obtained by substituting x1 for x in the above formulas (9) and (10) and R and y L It can be derived by substituting y1 into

[0141] When, for example, Napier's constant e is used as the coefficient a, the above formulas (9), (10), (11), and (12) can be expressed as the following formulas (13), (14), (15), and (16), respectively.

[0142] y R =Ahys[1-exp{-c(xb)}]···(13)

[0143] y L =-Ahys[{1-exp{c(x-b')}]···(14)

[0144] b=x1+(1 / c)log e {1-(y1 / Ahys)}···(15)

[0145] b'=x1-(1 / c)log e {1-(y1 / Ahys)}···(16)

[0146] As described above, the SBW system does not have an intermediate shaft that is mechanically connected to the column shaft 2. In other words, the steering mechanism and the turning mechanism are mechanically separated. For this reason, it is necessary to transmit the oversteer or understeer state, which occurs when traveling on a frozen road surface or a low μ road where the frictional resistance of the road surface is significantly reduced due to hydroplaning in rainy weather, to the reaction device 30 as a steering reaction force.

[0147] In this disclosure, as shown in Fig. 12, a road surface reaction torque value generating section 280 is provided as a component of steering torque target value generating section 200, and a self-aligning torque corresponding to first steering motor current command value Iref_a generated by steering angle control section 700 is estimated, and a road surface reaction torque value (second torque value) corresponding to the estimated self-aligning torque is applied to steering torque target value Th_ref. This makes it possible to impart a steering reaction force corresponding to road surface conditions. Below, a detailed description will be given of the configuration and operation capable of imparting a steering reaction force corresponding to road surface conditions.

[0148] 20 is a block diagram showing an example of the configuration of a road surface reaction torque value generator according to embodiment 1. The road surface reaction torque value generator 280 according to embodiment 1 includes, as main components, a SAT responsive torque value generator 281 and a torque reference value generator 282.

[0149] 21 is a block diagram showing an example of the configuration of the road surface reaction force sensitive torque value generating section 281. The SAT sensitive torque value generating section 281 includes, as main components, a SAT estimating section 281a and a SAT sensitive torque map section 281b.

[0150] First, a method for estimating the self-aligning torque (SAT) estimated value Tsat_est in the SAT estimator 281a will be described with reference to FIGS.

[0151] FIG. 22 is an image diagram showing the state of torque generated between the road surface and the steering motor.

[0152] When the driver steers the steering wheel, a steering angle target value θt_ref is generated, and the steering motor 41 generates a steering motor torque Tm for steering the steered wheels 5L, 5R in accordance with the steering angle target value θt_ref. As a result, the steered wheels 5L, 5R are steered, and a self-aligning torque T SATAt that time, a torque acting as a resistance is generated by the inertia (pinion shaft converted inertia) J acting on the pinion shaft due to the (rotor of) the steering motor 41, the reduction mechanism, etc. Furthermore, a damper term (damper coefficient D M ) A physical torque (viscous torque) is generated, which can be expressed as follows. The balance of these forces gives the equation of motion shown in Eq. (17) below.

[0153] J×α M +D M ×ω M =Tm-T SAT (17)

[0154] In the above formula (17), ω M is the motor angular velocity converted to the pinion shaft (value relative to the pinion shaft), and α M is the motor angular acceleration converted to the pinion shaft. Then, the above equation (17) is used to calculate the self-aligning torque T SAT By solving this, we obtain the following equation (18).

[0155] T SAT = Tm-J×α M -D M ×ω M (18)

[0156] As can be seen from the above equation (18), the pinion shaft converted inertia J and the damping coefficient D M By calculating in advance as a constant, the motor angular velocity ω M , motor angular acceleration α M , and the self-aligning torque Tm is calculated from the steering motor torque Tm. SAT The pinion shaft converted inertia J may be simply converted to a value corresponding to the pinion shaft inertia using a relational expression between the motor inertia and the reduction ratio.

[0157] SAT estimation section 281a receives as input first turning motor current command value Iref_a and actual turning angle θt_act generated by turning angle control section 700. SAT estimation section 281a calculates self-aligning torque T SATis replaced with the self-aligning torque estimated value Tsat_est to calculate the self-aligning torque estimated value Tsat_est.

[0158] 23 is a block diagram showing an example of the configuration of the SAT estimation unit 281a. The SAT estimation unit 281a includes a conversion unit 311, an angular velocity calculation unit 312, an angular acceleration calculation unit 313, a block 315, a block 317, and a subtraction unit 318.

[0159] The first turning motor current command value Iref_a is input to conversion section 311. Conversion section 311 calculates pinion shaft converted turning motor torque Tm by multiplying a predetermined gear ratio and torque constant.

[0160] The actual steering angle θt_act is input to the angular velocity calculation section 312. The angular velocity calculation section 312 converts the actual steering angle θt_act into the angle of the steering motor 41, performs differential calculation processing on the angle of the steering motor 41, and further divides it by the gear ratio to obtain the pinion shaft converted motor angular velocity ω M Calculate.

[0161] The angular acceleration calculation unit 313 receives the motor angular velocity ω M The angular acceleration calculation unit 313 receives the motor angular velocity ω M Differentiate and calculate the motor angular acceleration α M Calculate.

[0162] The steering motor torque Tm and the motor angular velocity ω M , and motor angular acceleration α M Using the above, the self-aligning torque estimated value Tsat_est is calculated based on the above equation (18) by the configuration shown in FIG.

[0163] A block 315 receives the motor angular velocity ω M is input. Block 315 adds the damper coefficient D M Multiply and output.

[0164] The block 317 receives the motor angular acceleration α M is input. Block 317 multiplies the input data by the pinion shaft converted inertia J and outputs the result.

[0165] Subtraction section 318 subtracts the output of block 317 and the output of block 315 from the steering motor torque Tm outputted from conversion section 311 .

[0166] The above-mentioned configuration can realize the above formula (18). That is, the self-aligning torque estimated value Tsat_est is calculated by the configuration of the SAT estimating section 281a shown in FIG.

[0167] In the embodiment where the angle of the steering motor 41 is detected, the angular velocity calculation unit 312 performs a differential calculation process on the detected angle of the steering motor 41, and further divides it by the gear ratio to obtain the pinion shaft converted motor angular velocity ω M In addition, if the column angle can be directly detected, the column angle may be used as angle information instead of the actual turning angle θt_act or the angle of the turning motor 41. In this case, pinion shaft conversion is not necessary. Also, instead of the actual turning angle θt_act or the angle of the turning motor 41, a signal obtained by converting the turning angular velocity or the turning motor angular velocity into a pinion shaft is calculated as the motor angular velocity ω M and omitting the differentiation process for the angle of steering motor 41. Furthermore, the self-aligning torque estimated value Tsat_est may be calculated by a method other than the above, or an estimated value equivalent to the self-aligning torque estimated value Tsat_est may be used. Below, a method of calculating the self-aligning torque estimated value Tsat_est that is different from the above method will be described.

[0168] In a calculation method of self-aligning torque estimated value Tsat_est different from the above-mentioned method, first turning motor current command value Iref_a generated by turning angle control unit 700 is input to SAT estimator 281a. Also, a transfer function Gfil shown in the following equation (19) is set in SAT estimator 281a. Transfer function Gfil is stored, for example, in a ROM of an ECU constituting control device 50.

[0169] Gfil = N(s) / D(s) = (Ds+E) / (As 2 +Bs+C) · · · (19)

[0170] In the above equation (19), the linear function N(s) = Ds + E and the quadratic function D(s) = As 2 A, B, C, D, and E in +Bs+C are coefficients set by the simulation shown below.

[0171] In this disclosure, the transfer function Gfil is assumed to be a transfer function with a linear numerator and a quadratic denominator, but the order of the numerator and denominator can be changed as appropriate depending on the allowable error between the actual self-aligning torque Tsat_act and the self-aligning torque estimate Tsat_est, the load on the ECU, etc.

[0172] For example, if the order of the numerator and denominator is increased, the relationship between the first steering motor current command value Iref_a obtained through experiments described below and the actual self-aligning torque Tsat_act can be made to match well with the transfer characteristics of the transfer function Gfil, making it possible to estimate a self-aligning torque estimated value Tsat_est that is close to the actual measured value.

[0173] On the other hand, if the order of the numerator and denominator is reduced, the load on the ECU can be reduced.

[0174] Self-aligning torque T SAT It is assumed that the relational expression shown in the following equation (20) holds between the first turning motor current command value Iref_a and the self-aligning torque TSAT is defined as the self-aligning torque estimated value Tsat_est in this disclosure.

[0175] T SAT =Gfil×Iref_a=Tsat_est···(20)

[0176] In other words, transfer function Gfil calculates self-aligning torque estimated value Tsat_est from first turning motor current command value Iref_a by simulating the relationship between first turning motor current command value Iref_a and actual self-aligning torque Tsat_act obtained by experiment.

[0177] On the other hand, the actual self-aligning torque Tsat_act acting on the turning mechanism can be calculated from the axial force applied to the tie rod. Fig. 24 is a conceptual diagram for explaining a method of calculating the actual self-aligning torque acting on the turning mechanism.

[0178] The actual self-aligning torque Tsat_act can be calculated by the following formula (21) using the axial forces FL and FR applied to the tie rods 3a and 3b and the length L of the arms 6a and 6b that is determined for each vehicle model.

[0179] Tsat_act=FL×L-FR×L···(21)

[0180] In the present disclosure, the actual self-aligning torque Tsat_act is calculated using the above formula (21) that uses the axial forces FL and FR that have been measured in advance through an experiment using an actual vehicle. The axial forces FL and FR can be measured, for example, by attaching force sensors to the tie rods 3a and 3b.

[0181] FIG. 25 is a conceptual diagram showing a configuration for executing a simulation for deriving the transfer function Gfil.

[0182] The first steering motor current command value Iref_a and the axial forces FL and FR are input to the processing device shown in Fig. 25. The processing device derives a transfer function Gfil such that the self-aligning torque estimated value Tsat_est shown in the above equation (20) approximates the actual self-aligning torque Tsat_act calculated by the above equation (21). An example of the processing device shown in Fig. 25 is one that includes a frequency characteristic analysis device (servo analyzer).

[0183] Specifically, the processing device performs curve fitting using a sweep method to derive the coefficients A, B, C, D, and E of the transfer function Gfil shown in the above formula (19). As an example of the curve fitting method, for example, the least squares approximation method can be used. Note that the curve fitting method is not limited to the least squares approximation method.

[0184] SAT estimation section 281a performs filtering on first steering motor current command value Iref_a generated by steering angle control section 700 using transfer function Gfil derived as described above, and calculates self-aligning torque estimated value Tsat_est shown in the above equation (20). This allows obtaining self-aligning torque estimated value Tsat_est corresponding to the behavior of actual self-aligning torque Tsat_act when the vehicle is actually traveling.

[0185] The transfer function used in calculating the self-aligning torque estimated value Tsat_est in the SAT estimation unit 281a is not limited to the above embodiment (19). Specifically, for example, the present disclosure is not limited by the orders of the functions N(s) and D(s).

[0186] Returning to Fig. 21, the sign extraction unit 281d extracts the sign of the self-aligning torque estimation value Tsat_est obtained by the above-mentioned calculation method. Specifically, for example, the value of the self-aligning torque estimation value Tsat_est is divided by the absolute value of the self-aligning torque estimation value Tsat_est. As a result, the sign extraction unit 281d outputs "1" when the sign of the self-aligning torque estimation value Tsat_est is "+", and outputs "-1" when the sign of the self-aligning torque estimation value Tsat_est is "-". Specifically, the sign extraction unit 281d generates, for example, a sign function Sgn(Tsat_est) of the self-aligning torque estimation value Tsat_est.

[0187] Fig. 26A is a diagram showing an example of the characteristics of the SAT sensitive torque map. The self-aligning torque estimated value |Tsat_est| and the vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation unit 281c are input to the SAT sensitive torque map unit 281b. The SAT sensitive torque map unit 281b generates the self-aligning torque sensitive torque value Trrf_est0 using the vehicle speed Vs as a parameter by using the SAT sensitive torque map shown in Fig. 26A. The SAT sensitive torque map is stored, for example, in the ROM of the ECU constituting the control device 50.

[0188] As shown in FIG. 26A, the self-aligning torque sensitive torque value Trrf_est0 has a torque sensitive characteristic that increases and decreases according to the self-aligning torque estimated value |Tsat_est|.

[0189] More specifically, the self-aligning torque sensitive torque value Trrf_est0 increases as the self-aligning torque estimated value |Tsat_est| increases, and the rate of increase decreases as the self-aligning torque estimated value |Tsat_est| increases.

[0190] Furthermore, the self-aligning torque sensitive torque value Trrf_est0 has a vehicle speed sensitive characteristic that increases and decreases according to the vehicle speed Vs. More specifically, the self-aligning torque sensitive torque value Trrf_est0 increases as the vehicle speed Vs increases, as shown in FIG 26A.

[0191] In other words, the reaction force obtained by the self-aligning torque sensitive torque value Trrf_est0 derived from the SAT sensitive torque map shown in Fig. 26A becomes larger as the self-aligning torque estimated value |Tsat_est| becomes larger and as the vehicle speed (vehicle speed Vs) becomes faster. Note that, although the SAT sensitive torque map shown in Fig. 26A has a vehicle speed sensitive characteristic, the present invention is not limited to this.

[0192] The SAT sensitive torque value generation unit 281 multiplies the self-aligning torque sensitive torque value Trrf_est0, which is the output value of the SAT sensitive torque map unit 281b, by the sign function Sgn(Tsat_est) of the self-aligning torque estimated value Tsat_est in a multiplication unit 281e to output the self-aligning torque sensitive torque value Trrf_est that has been sign-converted.

[0193] Fig. 26B is a diagram conceptually showing an example of the characteristics of the self-aligning torque sensitive torque value Trrf_est after sign conversion. As shown in Fig. 26B, the self-aligning torque sensitive torque value Trrf_est output from the SAT sensitive torque value generating unit 281 increases or decreases according to the self-aligning torque estimated value Tsat_est.

[0194] The method of deriving the self-aligning torque sensitive torque value Trrf_est according to the self-aligning torque estimated value Tsat_est is not limited to the map shown in FIG. 26A or FIG. 26B described above, and may be, for example, a method in which the self-aligning torque sensitive torque value Trrf_est is calculated using a predetermined transfer function showing the relationship between the self-aligning torque estimated value Tsat_est and the self-aligning torque sensitive torque value Trrf_est.

[0195] In the present disclosure, the SAT sensitive torque value generating unit 281 calculates a self-aligning torque estimated value Tsat_est corresponding to the first steering motor current command value Iref_a before adding the second current compensation value Iref_b output from the friction compensation unit 770, thereby obtaining a self-aligning torque estimated value Tsat_est corresponding to the behavior of the actual self-aligning torque Tsat_act when the vehicle is actually traveling, and obtaining a self-aligning torque sensitive torque value Trrf_est corresponding to the self-aligning torque estimated value Tsat_est.

[0196] Incidentally, in a mode in which steering angle control section 700 does not include friction compensation section 770, a mode in which a self-aligning torque corresponding to second steering motor current command value It_ref instead of first steering motor current command value Iref_a may be used.

[0197] Fig. 27 is a block diagram showing an example of the configuration of the torque reference value generating unit. The sign extracting unit 282c extracts the sign of the actual steering angle θh_act. Specifically, for example, the value of the actual steering angle θh_a is divided by the absolute value of the actual steering angle θh_a. As a result, the sign extracting unit 282c outputs "1" when the sign of the actual steering angle θh_act is "+", and outputs "-1" when the sign of the actual steering angle θh_act is "-". Specifically, the sign extracting unit 213 generates, for example, a sign function Sgn(θh) of the actual steering angle θh_act.

[0198] Fig. 28A is a diagram showing an example of the characteristics of the torque reference map. The steering angle |θh| and the vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation section 282b are input to the torque reference map section 282a. The torque reference value generation section 282 generates a torque reference value Trrf_base0 using the torque reference map shown in Fig. 28A with the vehicle speed Vs as a parameter. The torque reference map is stored, for example, in the ROM of the ECU constituting the control device 50.

[0199] The torque reference value Trrf_base0 has an angle-sensitive characteristic that increases and decreases according to the steering angle |θh|, as shown in Fig. 28A. More specifically, the torque reference value Trrf_base0 increases as the steering angle |θh| increases, and the rate of increase decreases as the steering angle |θh| increases.

[0200] Furthermore, the torque reference value Trrf_base0 has a vehicle speed-sensitive characteristic that increases and decreases according to the vehicle speed Vs. More specifically, the torque reference value Trrf_base0 increases as the vehicle speed Vs increases, as shown in Fig. 28A.

[0201] That is, the reaction force obtained by the torque reference value Trrf_base0 derived from the torque reference map shown in Fig. 28A increases as the steering angle |θh| increases and as the vehicle speed (vehicle speed Vs) increases. Note that the torque reference map shown in Fig. 28A has a vehicle speed-sensitive characteristic, but is not limited to this. The torque reference map shown in Fig. 28A may have the same characteristic as the SAT-sensitive torque map shown in Fig. 26A.

[0202] The torque reference value generating section 282 multiplies the torque reference value Trrf_base0, which is the output value of the torque reference map section 282a, by the sign function Sgn(θh) of the actual steering angle θh_act in a multiplication section 282d to output the torque reference value Trrf_base that has been sign-converted.

[0203] Fig. 28B is a diagram showing an example of the characteristics of the torque reference value Trrf_base. As shown in Fig. 28B, the torque reference value Trrf_base output from the torque reference value generating section 282 increases or decreases according to the actual steering angle θh_act.

[0204] Returning to Fig. 20, the subtraction unit 283 subtracts the torque reference value Trrf_base generated by the torque reference value generation unit 282 from the self-aligning torque sensitive torque value Trrf_est output from the SAT sensitive torque value generation unit 281. This extracts a torque component Trrf_dev0 according to the road surface condition. For example, when the vehicle is traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like and the tires are slipping, this torque component Trrf_dev0 is estimated as a negative torque component. Hereinafter, the torque component obtained by subtracting the torque reference value Trrf_base generated by the torque reference value generation unit 282 from the self-aligning torque sensitive torque value Trrf_est output from the SAT sensitive torque value generation unit 281 is also referred to as a "torque deviation".

[0205] The torque deviation Trrf_dev0 is input to the dead zone processor 284. Fig. 29 is a diagram showing an example of the output characteristics of the dead zone processor.

[0206] The dead band processing unit 284 generates the torque deviation Trrf_div by setting the minute range of the torque deviation Trrf_dev0 to 0. This obtains the torque deviation Trrf_div from which the minute error components contained in the torque deviation Trrf_dev0 extracted as the difference between the self-aligning torque sensitive torque value Trrf_est and the torque reference value Trrf_base have been removed.

[0207] The multiplication unit 286 generates a torque value Tref_d0 by multiplying the torque deviation Trrf_div by a gain Trrf_div_Gain according to the vehicle speed Vs. In the present disclosure, the road surface reaction force torque value generation unit 280 includes a vehicle speed sensitive gain map unit 285 as a component that generates the gain Trrf_div_Gain according to the vehicle speed Vs to be multiplied by the torque deviation Trrf_div. FIG. 30 is a diagram showing an example of the characteristics of the vehicle speed sensitive gain map. The vehicle speed sensitive gain map is stored, for example, in the ROM of the ECU constituting the control device 50.

[0208] Specifically, in the example shown in FIG. 30, the torque deviation Trrf_div is set to 0.7 when the vehicle speed Vs is in the range of 50 km / h or less, and the torque deviation Trrf_div gradually increases when the vehicle speed Vs is in the range of 50 km / h to 70 km / h.

[0209] The output limiting unit 287 performs an output limiting process on the torque value Tref_d0. An upper limit value and a lower limit value for the torque value Tref_d0 are set in advance in the output limiting unit 287. The output limiting unit 287 outputs a torque value Tref_d (second torque value) obtained by limiting the torque value Tref_d0 between the upper and lower limit values.

[0210] The steering torque target value generating unit 200 generates the steering torque target value Th_ref by adding (adding unit 271) the torque value Tref_d (second torque value) generated by the road surface reaction force torque value generating unit 280 to the torque value Tref_a (first torque value) generated by the steering reaction force torque value generating unit 210. This makes it possible to apply a steering reaction force that appropriately reflects the road surface conditions.

[0211] 31 is a block diagram showing an example of the configuration of a torque adjustment gain generating unit according to embodiment 1. The torque deviation Trrf_div extracted by road surface reaction torque value generating unit 280 is input to torque adjustment gain generating unit 290. As described above, for example, when the vehicle is traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like and the tires are slipping, the torque deviation Trrf_div is estimated as a negative torque component.

[0212] The sign reversal unit 291 performs sign reversal processing on the torque deviation Trrf_div, and the binarization processing unit 292 performs threshold determination processing on the torque component -Trrf_div after the sign reversal processing, with 0 as the threshold. Specifically, the binarization processing unit 292 outputs "0" when the torque component after the sign reversal processing (-Trrf_div) is equal to or less than 0, and outputs "1" when the torque component after the sign reversal processing (-Trrf_div) exceeds 0. The multiplication unit 293 multiplies the torque component (-Trrf_div) by the output of the binarization processing unit 292. This generates a torque component Trrf_div_inv that is "0" when the tires are not slipping and is a positive value when the tires are slipping.

[0213] The torque sensitive gain map unit 294 has a torque sensitive gain map for setting the torque gain Tref_Gain according to the torque component Trrf_div_inv. The torque sensitive gain map is stored, for example, in the ROM of the ECU constituting the control device 50. FIG. 32A is a diagram showing a first characteristic example of the torque sensitive gain map. FIG. 32B is a diagram showing a second characteristic example of the torque sensitive gain map. FIG. 32C is a diagram showing a third characteristic example of the torque sensitive gain map. FIG. 32D is a diagram showing a fourth characteristic example of the torque sensitive gain map.

[0214] As shown in Figures 32A, 32B, 32C, and 32D, the torque gain Tref_Gain is a value equal to or less than 1, and has a torque-sensitive characteristic that decreases with an increase in the torque component Trrf_div_inv. In other words, the torque gain Tref_Gain has a torque-sensitive characteristic that decreases with an increase in the negative torque deviation Trrf_div. The torque-sensitive gain map unit 294 generates the torque gain Tref_Gain using the torque-sensitive gain maps shown in Figures 32A, 32B, 32C, and 32D, for example. For example, as shown in Figure 32D, the characteristic may be changed between the high speed range and the low speed range of the vehicle speed Vs.

[0215] The steering torque target value generating unit 200 multiplies the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 by the torque gain Tref_Gain generated by the torque adjustment gain generating unit 290 (multiplication unit 260). As a result, for example, when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like, the steering torque target value Th_ref decreases.

[0216] Fig. 33 is a diagram showing an example of the behavior of the control device of the vehicle steering system according to embodiment 1. Fig. 33 shows the behavior of the steering angle (dotted line) and the steering torque (solid line) when the driver turns the steering wheel further. The dashed line shown in Fig. 33 shows the behavior of the steering torque in a configuration that does not have the torque adjustment gain generating unit 290.

[0217] Fig. 33 illustrates an example of behavior in a situation where the vehicle is traveling at a constant vehicle speed on a low μ road where the frictional resistance of the road surface has significantly decreased due to rainfall, etc., and the driver turns the steering wheel further at a constant steering angular speed from time t0, causing the tires to slip. Note that the example shown in Fig. 33 does not take into account the torque value Tref_b by the damping torque value generation unit 240 and the torque compensation value Tref_c by the hysteresis compensation unit 250.

[0218] When the tires are not slipping, further steering of the steering wheel does not cause any fluctuation in the steering torque. When the frictional resistance of the road surface is significantly reduced due to rainfall or the like, causing tire slippage, a negative torque value Tref_d (second torque value) generated by the road surface reaction torque value generating unit 280 is added to the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210, and the steering torque is reduced.

[0219] As described above, the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 has a vehicle speed-sensitive characteristic that increases as the vehicle speed increases. Therefore, the influence of the torque value Tref_d (second torque value) relatively decreases as the vehicle speed increases, making it difficult for the driver to feel that the tires are slipping.

[0220] The steering torque target value generating unit 200 according to the first embodiment includes the torque adjustment gain generating unit 290, and thus can reduce the steering torque target value Th_ref when the tires are slipping while the vehicle is traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall, etc. This makes it easier for the driver to feel that the tires are slipping.

[0221] (Modification) FIG. 34 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to a modified example of the first embodiment.

[0222] In the above-mentioned embodiment 1, the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 is multiplied by the torque gain Tref_Gain generated by the torque adjustment gain generating unit 290 (multiplication unit 260). However, as in the configuration of the steering torque target value generating unit 200a shown in FIG. 34, the sum of the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 and the torque value Tref_d (second torque value) generated by the road surface reaction torque value generating unit 280 is multiplied by the torque gain Tref_Gain generated by the torque adjustment gain generating unit 290 (multiplication unit 260b).

[0223] (Embodiment 2) 35 is a block diagram showing a configuration example of a steering torque target value generating unit according to embodiment 2. In embodiment 2, components and operations different from those in embodiment 1 will be described in detail, and descriptions of components and operations similar to those in embodiment 1 may be omitted.

[0224] The self-aligning torque estimated value Tsat_est estimated by the SAT estimation unit 281a varies depending on the road surface condition as well as the vehicle condition such as the vehicle speed and steering angle. Therefore, depending on the vehicle condition, the road surface condition may not be fully reflected, and a steering feel appropriate for the road surface condition and the vehicle condition may not be obtained.

[0225] In the steering torque target value generating section 200b according to the second embodiment, a steering feel reflecting the road surface condition and the vehicle state is obtained by multiplying the torque value Tref_a (first torque value) generated by the steering reaction torque value generating section 210 and the torque value Tref_d (second torque value) generated by the road surface reaction torque value generating section 280 by an appropriate gain using the vehicle speed Vs, the actual steering angle θh_act, the actual turning angle θt_act, etc. as parameters (variables). Specifically, the steering torque target value generating section 200b according to the second embodiment includes a gain ratio generating section 230 that generates a ratio (hereinafter also simply referred to as "gain ratio") between a first gain Ga by which the torque value Tref_a (first torque value) is multiplied and a second gain Gb by which the torque value Tref_d (second torque value) is multiplied.

[0226] The configuration and operation of the second embodiment capable of providing a steering feeling according to the road surface condition and the vehicle state will be described below. Fig. 36A is a diagram conceptually showing a first example of a gain ratio setting example when the vehicle speed is a parameter. Fig. 36B is a diagram conceptually showing a second example of a gain ratio setting example when the vehicle speed is a parameter. Fig. 36C is a diagram conceptually showing a third example of a gain ratio setting example when the vehicle speed is a parameter.

[0227] 36A, 36B, and 36C, a vehicle speed Vs is input to the gain ratio generation unit 230. The gain ratio generation unit 230 generates a first gain Ga that increases or decreases according to the vehicle speed Vs, and a second gain Gb whose sum with the first gain Ga is 1. The first gain Ga is multiplied by a torque value Tref_a (first torque value) by a multiplication unit 261. The second gain Gb is multiplied by a torque value Tref_d (second torque value) by a multiplication unit 262.

[0228] The gain ratio generating unit 230 monotonically decreases the first gain Ga by which the torque value Tref_a (first torque value) is multiplied within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. Accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied monotonically within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. The first vehicle speed Vs_A is set to, for example, 5 [km / h]. The second vehicle speed Vs_B is set to, for example, 30 [km / h]. The present disclosure is not limited to the values ​​of the first vehicle speed Vs_A and the second vehicle speed Vs_B.

[0229] 36A shows an example in which the maximum value Ga_max of the first gain Ga in the range equal to or less than the first vehicle speed Vs_A is greater than the maximum value Gb_max of the second gain Gb in the range equal to or greater than the second vehicle speed Vs_B. In this case, the minimum value Gb_min of the second gain Gb in the range equal to or less than the first vehicle speed Vs_A is greater than the minimum value Ga_min of the first gain Ga in the range equal to or greater than the second vehicle speed Vs_B.

[0230] 36B shows an example in which the maximum value Ga_max of the first gain Ga in the range equal to or less than the first vehicle speed Vs_A is smaller than the maximum value Gb_max of the second gain Gb in the range equal to or more than the second vehicle speed Vs_B. In this case, the minimum value Gb_min of the second gain Gb in the range equal to or less than the first vehicle speed Vs_A is smaller than the minimum value Ga_min of the first gain Ga in the range equal to or more than the second vehicle speed Vs_B.

[0231] 36C shows an example in which the maximum value Ga_max of the first gain Ga in the range equal to or less than the first vehicle speed Vs_A is equal to the maximum value Gb_max of the second gain Gb in the range equal to or more than the second vehicle speed Vs_B. In this case, the minimum value Gb_min of the second gain Gb in the range equal to or less than the first vehicle speed Vs_A is equal to the minimum value Ga_min of the first gain Ga in the range equal to or more than the second vehicle speed Vs_B.

[0232] The maximum value Ga_max of the first gain Ga, the minimum value Ga_min of the first gain Ga, the maximum value Gb_max of the second gain Gb, and the minimum value Gb_min of the second gain Gb, and their magnitude relationships may be set appropriately depending on the driving performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0233] In the examples shown in Fig. 36A, Fig. 36B, and Fig. 36C, a steering reaction force according to the self-aligning torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio according to the vehicle speed Vs. Specifically, in a region where the vehicle speed Vs is relatively small, the steering torque target value generating unit 200b generates the steering torque target value Th_ref by multiplying the torque value Tref_a (first torque value) output from the steering reaction torque value generating unit 210 by a relatively large first gain Ga, and in a region where the vehicle speed Vs is relatively large, the steering torque target value Th_ref is generated by multiplying the torque value Tref_d (second torque value) output from the road reaction torque value generating unit 280 by a relatively large second gain Gb. In a low-speed region where the vehicle speed Vs is relatively small, the component of the reaction torque caused by the elastic deformation of the tire is the main component of the road reaction torque, and the proportion of the reaction torque component caused by the road surface condition in the road reaction torque is small. That is, when the output of the road surface reaction torque value generating unit 280 is relatively large in the low speed region, a heavy steering torque is applied even though the road surface condition is difficult to obtain, and the steering feel of the driver deteriorates. Therefore, in the low speed region where the vehicle speed Vs is relatively low, a steering feel that reflects the road surface condition and the vehicle speed Vs can be obtained by using a relatively large first gain Ga and a relatively small second gain Gb.

[0234] The gain ratio setting example when the vehicle speed Vs is used as a parameter is merely an example, and is not limited to the above-mentioned aspects shown in Figs. 36A, 36B, and 36C. For example, in a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually decrease as the vehicle speed Vs increases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually increase as the vehicle speed Vs increases. Also, for example, in a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually increase as the vehicle speed Vs decreases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually decrease as the vehicle speed Vs decreases.

[0235] FIG. 37 is a diagram conceptually showing an example of a gain ratio setting example when the actual steering angle is used as a parameter.

[0236] 37, the actual steering angle θh_act is input to the gain ratio generation unit 230. The gain ratio generation unit 230 generates a first gain Ga that increases or decreases according to the actual steering angle θh_act, and a second gain Gb whose sum with the first gain Ga is 1. The first gain Ga is multiplied by a torque value Tref_a (first torque value) by a multiplication unit 261. The second gain Gb is multiplied by a torque value Tref_d (second torque value) by a multiplication unit 262.

[0237] The gain ratio generating unit 230 monotonically decreases the first gain Ga by which the torque value Tref_a (first torque value) is multiplied within a range of the first steering angle θh_A or more and the second steering angle θh_B or less. Accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied monotonically increases within a range of the first steering angle θh_A or more and the second steering angle θh_B or less. The first steering angle θh_A is set to, for example, 3 [deg]. The second steering angle θh_B is set to, for example, 20 [deg]. The present disclosure is not limited to the values ​​of the first steering angle θh_A and the second steering angle θh_B.

[0238] 37 shows an example in which the maximum value Ga_max of the first gain Ga in the range equal to or less than the first steering angle θh_A is greater than the maximum value Gb_max of the second gain Gb in the range equal to or more than the second steering angle θh_B. In this case, the minimum value Gb_min of the second gain Gb in the range equal to or less than the first steering angle θh_A is greater than the minimum value Ga_min of the first gain Ga in the range equal to or more than the second steering angle θh_B.

[0239] In addition, the maximum value Ga_max of the first gain Ga in the range equal to or less than the first steering angle θh_A may be smaller than the maximum value Gb_max of the second gain Gb in the range equal to or greater than the second steering angle θh_B, and the minimum value Gb_min of the second gain Gb in the range equal to or less than the first steering angle θh_A may be smaller than the minimum value Ga_min of the first gain Ga in the range equal to or greater than the second steering angle θh_B.

[0240] In addition, the maximum value Ga_max of the first gain Ga in the range equal to or less than the first steering angle θh_A may be equal to the maximum value Gb_max of the second gain Gb in the range equal to or more than the second steering angle θh_B, and the minimum value Gb_min of the second gain Gb in the range equal to or less than the first steering angle θh_A may be equal to the minimum value Ga_min of the first gain Ga in the range equal to or more than the second steering angle θh_B.

[0241] The maximum value Ga_max of the first gain Ga, the minimum value Ga_min of the first gain Ga, the maximum value Gb_max of the second gain Gb, and the minimum value Gb_min of the second gain Gb, and their magnitude relationships may be set appropriately depending on the driving performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0242] In the example shown in Fig. 37, a steering reaction force corresponding to the self-aligning torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio corresponding to the actual steering angle θh_act. Specifically, in a region where the actual steering angle θh_act is relatively small, the steering torque target value generating unit 200b generates the steering torque target value Th_ref by multiplying the torque value Tref_a (first torque value) output from the steering reaction force torque value generating unit 210 by a relatively large first gain Ga, and in a region where the actual steering angle θh_act is relatively large, the steering torque target value Th_ref by multiplying the torque value Tref_d (second torque value) output from the road surface reaction force torque value generating unit 280 by a relatively large second gain Gb. This makes it possible to obtain a steering feel that reflects the road surface condition and the actual steering angle θh_act.

[0243] The gain ratio setting example when the actual steering angle θh_act is used as a parameter is merely an example, and is not limited to the aspect shown in Fig. 37. For example, in a range of the first steering angle θh_A or more and the second steering angle θh_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually decrease as the actual steering angle θh_act increases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually increase as the actual steering angle θh_act increases. Also, for example, in a range of the first steering angle θh_A or more and the second steering angle θh_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually increase as the actual steering angle θh_act decreases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually decrease as the actual steering angle θh_act decreases.

[0244] FIG. 38 is a diagram conceptually showing an example of a gain ratio setting example when the actual steering angle is used as a parameter.

[0245] 38, actual steering angle θt_act is input to gain ratio generation section 230. Gain ratio generation section 230 generates a first gain Ga that increases or decreases according to the actual steering angle θt_act, and a second gain Gb whose sum with the first gain Ga is 1. Multiplication section 261 multiplies a torque value Tref_a (first torque value) by the first gain Ga. Multiplication section 262 multiplies a torque value Tref_d (second torque value) by the second gain Gb.

[0246] Gain ratio generating section 230 monotonically decreases the first gain Ga by which the torque value Tref_a (first torque value) is multiplied within a range of the first turning angle θt_A or more and the second turning angle θt_B or less. Accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied monotonically increases within a range of the first turning angle θt_A or more and the second turning angle θt_B or less. The first turning angle θt_A is set to, for example, 3 [deg]. The second turning angle θt_B is set to, for example, 20 [deg]. The present disclosure is not limited to the values ​​of the first turning angle θt_A and the second turning angle θt_B.

[0247] 38 shows an example in which the maximum value Ga_max of the first gain Ga in the range equal to or less than the first turning angle θt_A is greater than the maximum value Gb_max of the second gain Gb in the range equal to or more than the second turning angle θt_B. In this case, the minimum value Gb_min of the second gain Gb in the range equal to or less than the first turning angle θt_A is greater than the minimum value Ga_min of the first gain Ga in the range equal to or more than the second turning angle θt_B.

[0248] In addition, the maximum value Ga_max of the first gain Ga in the range equal to or less than the first steering angle θt_A may be smaller than the maximum value Gb_max of the second gain Gb in the range equal to or more than the second steering angle θt_B, and the minimum value Gb_min of the second gain Gb in the range equal to or less than the first steering angle θt_A may be smaller than the minimum value Ga_min of the first gain Ga in the range equal to or more than the second steering angle θt_B.

[0249] In addition, the maximum value Ga_max of the first gain Ga in the range equal to or less than the first steering angle θt_A may be equal to the maximum value Gb_max of the second gain Gb in the range equal to or more than the second steering angle θt_B, and the minimum value Gb_min of the second gain Gb in the range equal to or less than the first steering angle θt_A may be equal to the minimum value Ga_min of the first gain Ga in the range equal to or more than the second steering angle θt_B.

[0250] The maximum value Ga_max of the first gain Ga, the minimum value Ga_min of the first gain Ga, the maximum value Gb_max of the second gain Gb, and the minimum value Gb_min of the second gain Gb, and their magnitude relationships may be set appropriately depending on the driving performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0251] In the example shown in Fig. 38, a steering reaction force corresponding to the self-aligning torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio corresponding to the actual turning angle θt_act. Specifically, in a region where the actual turning angle θt_act is relatively small, the steering torque target value generating section 200b generates the steering torque target value Th_ref by multiplying the torque value Tref_a (first torque value) output from the steering reaction force torque value generating section 210 by a relatively large first gain Ga, and in a region where the actual turning angle θt_act is relatively large, the steering torque target value Th_ref by multiplying the torque value Tref_d (second torque value) output from the road surface reaction force torque value generating section 280 by a relatively large second gain Gb. This makes it possible to obtain a steering feel that reflects the road surface conditions and the actual turning angle θt_act.

[0252] The gain ratio setting example when the actual turning angle θt_act is used as a parameter is just an example, and is not limited to the aspect shown in Fig. 38 described above. For example, in the range of the first turning angle θt_A or more and the second turning angle θt_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually decrease as the actual turning angle θt_act increases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually increase as the actual turning angle θt_act increases. Also, for example, in the range of the first turning angle θt_A or more and the second turning angle θt_B or less, the first gain Ga multiplied by the torque value Tref_a (first torque value) may gradually increase as the actual turning angle θt_act decreases, and accordingly, the second gain Gb multiplied by the torque value Tref_d (second torque value) may gradually decrease as the actual turning angle θt_act decreases.

[0253] Fig. 39 is a block diagram showing a configuration example of a gain ratio generating unit when vehicle speed and actual steering angle are used as parameters. Fig. 40A is a diagram conceptually showing an example of a gain ratio setting example with vehicle speed as a parameter. Fig. 40B is a diagram conceptually showing an example of a gain ratio setting example with actual steering angle as a parameter.

[0254] 39, the vehicle speed Vs and the actual steering angle θh_act are input to the gain ratio generating unit 230. In the example shown in FIG. 39, the gain ratio generating unit 230 includes a first gain ratio generating unit 230a, a second gain ratio generating unit 230b, and a gain ratio calculating unit 231.

[0255] The first gain ratio generating section 230a generates a first gain Ga1 that increases or decreases according to the vehicle speed Vs, and a second gain Gb1 whose sum with the first gain Ga1 is one.

[0256] The first gain ratio generating unit 230a monotonically decreases the first gain Ga1 within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. Accordingly, the second gain Gb1 monotonically increases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. The first vehicle speed Vs_A is set to, for example, 5 [km / h]. The second vehicle speed Vs_B is set to, for example, 30 [km / h]. The present disclosure is not limited to the values ​​of the first vehicle speed Vs_A and the second vehicle speed Vs_B.

[0257] 40A shows an example in which the maximum value Ga1_max of the first gain Ga1 in the range equal to or less than the first vehicle speed Vs_A is greater than the maximum value Gb1_max of the second gain Gb1 in the range equal to or greater than the second vehicle speed Vs_B. In this case, the minimum value Gb1_min of the second gain Gb1 in the range equal to or less than the first vehicle speed Vs_A is greater than the minimum value Ga1_min of the first gain Ga1 in the range equal to or greater than the second vehicle speed Vs_B.

[0258] In addition, the maximum value Ga1_max of the first gain Ga1 in the range below the first vehicle speed Vs_A may be smaller than the maximum value Gb1_max of the second gain Gb1 in the range above the second vehicle speed Vs_B, and the minimum value Gb1_min of the second gain Gb1 in the range below the first vehicle speed Vs_A may be smaller than the minimum value Ga1_min of the first gain Ga1 in the range above the second vehicle speed Vs_B.

[0259] In addition, the maximum value Ga1_max of the first gain Ga1 in the range below the first vehicle speed Vs_A may be equal to the maximum value Gb1_max of the second gain Gb1 in the range above the second vehicle speed Vs_B, and the minimum value Gb1_min of the second gain Gb1 in the range below the first vehicle speed Vs_A may be equal to the minimum value Ga1_min of the first gain Ga1 in the range above the second vehicle speed Vs_B.

[0260] The maximum value Ga_max of the first gain Ga, the minimum value Ga_min of the first gain Ga, the maximum value Gb_max of the second gain Gb, and the minimum value Gb_min of the second gain Gb, and their magnitude relationships may be set appropriately depending on the driving performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0261] The second gain ratio generating section 230b generates a first gain Ga2 that increases or decreases according to the actual steering angle θh_act, and a second gain Gb2 whose sum with the first gain Ga2 is one.

[0262] The second gain ratio generating unit 230b monotonically decreases the first gain Ga2 within a range of the first steering angle θh_A or more and the second steering angle θh_B or less. Accordingly, the second gain Gb2 monotonically increases within a range of the first steering angle θh_A or more and the second steering angle θh_B or less. The first steering angle θh_A is set to, for example, 3 [deg]. The second steering angle θh_B is set to, for example, 20 [deg]. The present disclosure is not limited to the values ​​of the first steering angle θh_A and the second steering angle θh_B.

[0263] 40B shows an example in which the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first steering angle θh_A is greater than the maximum value Gb2_max of the second gain Gb2 in the range equal to or more than the second steering angle θh_B. In this case, the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first steering angle θh_A is greater than the minimum value Ga2_min of the first gain Ga2 in the range equal to or more than the second steering angle θh_B.

[0264] In addition, the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first steering angle θh_A may be smaller than the maximum value Gb2_max of the second gain Gb2 in the range equal to or greater than the second steering angle θh_B, and the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first steering angle θh_A may be smaller than the minimum value Ga2_min of the first gain Ga2 in the range equal to or greater than the second steering angle θh_B.

[0265] In addition, the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first steering angle θh_A may be equal to the maximum value Gb2_max of the second gain Gb2 in the range equal to or more than the second steering angle θh_B, and the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first steering angle θh_A may be equal to the minimum value Ga2_min of the first gain Ga2 in the range equal to or more than the second steering angle θh_B.

[0266] The first gain Ga1 and second gain Gb1 output from the first gain ratio generation section 230a, and the first gain Ga2 and second gain Gb2 output from the second gain ratio generation section 230b are input to the gain ratio calculation section 231. The gain ratio calculation section 231 calculates the first gain Ga using the following equation (22), and calculates the second gain Gb using the following equation (23).

[0267] Ga=(Ga1×Ga2) / {(Ga1×Ga2)+(Gb1×Gb2)} ···(twenty two)

[0268] Gb=(Gb1×Gb2) / {(Ga1×Ga2)+(Gb1×Gb2)} ···(twenty three)

[0269] The torque value Tref_a (first torque value) is multiplied by the first gain Ga by the multiplication unit 261. The torque value Tref_d (second torque value) is multiplied by the second gain Gb by the multiplication unit 262.

[0270] In the configuration example shown in Fig. 39, a steering reaction force corresponding to the self-aligning torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio corresponding to both the vehicle speed Vs and the actual steering angle θh_act. Specifically, in an area where the vehicle speed Vs or the actual steering angle θh_act is relatively small, the steering torque target value generating unit 200b generates the steering torque target value Th_ref by multiplying the torque value Tref_a (first torque value) output from the steering reaction torque value generating unit 210 by a relatively large first gain Ga, and in an area where the vehicle speed Vs or the actual steering angle θh_act is relatively large, the steering torque target value Th_ref is multiplied by the torque value Tref_d (second torque value) output from the road surface reaction torque value generating unit 280 by a relatively large second gain Gb. This makes it possible to obtain a steering feel that reflects the road surface condition, the vehicle speed Vs, and the actual steering angle θh_act.

[0271] The gain ratio setting example using the vehicle speed Vs as a parameter is merely an example, and is not limited to the aspect shown in Fig. 40A described above. For example, the first gain Ga1 may be gradually decreased as the vehicle speed Vs increases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, and the second gain Gb1 may be gradually increased accordingly as the vehicle speed Vs increases. Also, for example, the first gain Ga1 may be gradually increased as the vehicle speed Vs decreases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, and the second gain Gb1 may be gradually decreased accordingly as the vehicle speed Vs decreases.

[0272] Also, the gain ratio setting example using the actual steering angle θh_act as a parameter is just an example, and is not limited to the aspect shown in Fig. 40B described above. For example, within a range of the first steering angle θh_A or more and the second steering angle θh_B or less, the first gain Ga2 may be gradually decreased as the actual steering angle θh_act increases, and the second gain Gb2 may be gradually increased accordingly as the actual steering angle θh_act increases. Also, for example, within a range of the first steering angle θh_A or more and the second steering angle θh_B or less, the first gain Ga2 may be gradually increased as the actual steering angle θh_act decreases, and the second gain Gb2 may be gradually decreased accordingly as the actual steering angle θh_act decreases.

[0273] Fig. 41 is a block diagram showing an example of the configuration of a gain ratio generating unit when vehicle speed and actual steering angle are used as parameters. Fig. 42A and Fig. 42B are diagrams conceptually showing an example of a gain ratio setting example with vehicle speed as a parameter. Fig. 42B is a diagram conceptually showing an example of a gain ratio setting example with actual steering angle as a parameter.

[0274] In the configuration example shown in Fig. 41, vehicle speed Vs and actual steering angle θt_act are input to gain ratio generation section 230. Further, as shown in Fig. 41, gain ratio generation section 230 includes a first gain ratio generation section 230a, a second gain ratio generation section 230c, and a gain ratio calculation section 231.

[0275] The first gain ratio generating section 230a generates a first gain Ga1 that increases or decreases according to the vehicle speed Vs, and a second gain Gb1 whose sum with the first gain Ga1 is one.

[0276] The first gain ratio generating unit 230a monotonically decreases the first gain Ga1 within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. Accordingly, the second gain Gb1 monotonically increases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less. The first vehicle speed Vs_A is set to, for example, 5 [km / h]. The second vehicle speed Vs_B is set to, for example, 30 [km / h]. The present disclosure is not limited to the values ​​of the first vehicle speed Vs_A and the second vehicle speed Vs_B.

[0277] 42A shows an example in which the maximum value Ga1_max of the first gain Ga1 in the range equal to or less than the first vehicle speed Vs_A is greater than the maximum value Gb1_max of the second gain Gb1 in the range equal to or greater than the second vehicle speed Vs_B. In this case, the minimum value Gb1_min of the second gain Gb1 in the range equal to or less than the first vehicle speed Vs_A is greater than the minimum value Ga1_min of the first gain Ga1 in the range equal to or greater than the second vehicle speed Vs_B.

[0278] In addition, the maximum value Ga1_max of the first gain Ga1 in the range below the first vehicle speed Vs_A may be smaller than the maximum value Gb1_max of the second gain Gb1 in the range above the second vehicle speed Vs_B, and the minimum value Gb1_min of the second gain Gb1 in the range below the first vehicle speed Vs_A may be smaller than the minimum value Ga1_min of the first gain Ga1 in the range above the second vehicle speed Vs_B.

[0279] In addition, the maximum value Ga1_max of the first gain Ga1 in the range below the first vehicle speed Vs_A may be equal to the maximum value Gb1_max of the second gain Gb1 in the range above the second vehicle speed Vs_B, and the minimum value Gb1_min of the second gain Gb1 in the range below the first vehicle speed Vs_A may be equal to the minimum value Ga1_min of the first gain Ga1 in the range above the second vehicle speed Vs_B.

[0280] The maximum value Ga_max of the first gain Ga, the minimum value Ga_min of the first gain Ga, the maximum value Gb_max of the second gain Gb, and the minimum value Gb_min of the second gain Gb, and their magnitude relationships may be set appropriately depending on the driving performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0281] The second gain ratio generating section 230c generates a first gain Ga2 that increases or decreases according to the actual steering angle θt_act, and a second gain Gb2 whose sum with the first gain Ga2 is one.

[0282] The second gain ratio generating unit 230c monotonically decreases the first gain Ga2 within a range of the first turning angle θt_A or more and the second turning angle θt_B or less. Accordingly, the second gain Gb2 monotonically increases within a range of the first turning angle θt_A or more and the second turning angle θt_B or less. The first turning angle θt_A is set to, for example, 3 [deg]. The second turning angle θt_B is set to, for example, 20 [deg]. The present disclosure is not limited to the values ​​of the first turning angle θt_A and the second turning angle θt_B.

[0283] 42B shows an example in which the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first turning angle θt_A is greater than the maximum value Gb2_max of the second gain Gb2 in the range equal to or more than the second turning angle θt_B. In this case, the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first turning angle θt_A is greater than the minimum value Ga2_min of the first gain Ga2 in the range equal to or more than the second turning angle θt_B.

[0284] In addition, the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first steering angle θt_A may be smaller than the maximum value Gb2_max of the second gain Gb2 in the range equal to or greater than the second steering angle θt_B, and the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first steering angle θt_A may be smaller than the minimum value Ga2_min of the first gain Ga2 in the range equal to or greater than the second steering angle θt_B.

[0285] In addition, the maximum value Ga2_max of the first gain Ga2 in the range equal to or less than the first steering angle θt_A may be equal to the maximum value Gb2_max of the second gain Gb2 in the range equal to or more than the second steering angle θt_B, and the minimum value Gb2_min of the second gain Gb2 in the range equal to or less than the first steering angle θt_A may be equal to the minimum value Ga2_min of the first gain Ga2 in the range equal to or more than the second steering angle θt_B.

[0286] The gain ratio calculation unit 231 calculates the first gain Ga and the second gain Gb using the equations (14) and (15) described in the fourth embodiment.

[0287] The torque value Tref_a (first torque value) is multiplied by the first gain Ga by the multiplication unit 261. The torque value Tref_d (second torque value) is multiplied by the second gain Gb by the multiplication unit 262.

[0288] In the configuration example shown in Fig. 41, a steering reaction force corresponding to the self-aligning torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio corresponding to both the vehicle speed Vs and the actual turning angle θt_act. Specifically, in an area where the vehicle speed Vs or the actual turning angle θt_act is relatively small, the steering torque target value generating unit 200b generates the steering torque target value Th_ref by multiplying the torque value Tref_a (first torque value) output from the steering reaction torque value generating unit 210 by a relatively large first gain Ga, and in an area where the vehicle speed Vs or the actual turning angle θt_act is relatively large, the steering torque target value Th_ref is generated by multiplying the torque value Tref_d (second torque value) output from the road surface reaction torque value generating unit 280 by a relatively large second gain Gb. This makes it possible to obtain a steering feel that reflects the road surface conditions, the vehicle speed Vs, and the actual turning angle θt_act.

[0289] The gain ratio setting example using the vehicle speed Vs as a parameter is merely an example, and is not limited to the aspect shown in Fig. 42A described above. For example, the first gain Ga1 may be gradually decreased as the vehicle speed Vs increases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, and the second gain Gb1 may be gradually increased accordingly as the vehicle speed Vs increases. Also, for example, the first gain Ga1 may be gradually increased as the vehicle speed Vs decreases within a range of the first vehicle speed Vs_A or more and the second vehicle speed Vs_B or less, and the second gain Gb1 may be gradually decreased accordingly as the vehicle speed Vs decreases.

[0290] Also, the gain ratio setting example using the actual turning angle θt_act as a parameter is just an example, and is not limited to the aspect shown in Fig. 42B described above. For example, in the range of the first turning angle θt_A or more and the second turning angle θt_B or less, the first gain Ga2 may gradually decrease as the actual turning angle θt_act increases, and the second gain Gb2 may gradually increase accordingly as the actual turning angle θt_act increases. Also, for example, in the range of the first turning angle θt_A or more and the second turning angle θt_B or less, the first gain Ga2 may gradually increase as the actual turning angle θt_act decreases, and the second gain Gb2 may gradually decrease accordingly as the actual turning angle θt_act decreases.

[0291] In the present disclosure, the ratio of the first gain Ga and the second gain Gb is not limited to a mode in which it changes linearly with respect to the change of each parameter. Specifically, for example, a gain ratio corresponding to each parameter value may be mapped, and a gain ratio according to the parameter value may be applied. Figure 43 is a 3D map conceptually showing an example of a gain ratio generation method.

[0292] The gain ratio generating unit 230 may generate the second gain Gb using a gain ratio map having the vehicle speed Vs and the actual steering angle θh_act as parameters as shown in FIG. 43, and calculate the first gain Ga using the following equation (24).

[0293] Ga = 1-Gb (24)

[0294] Alternatively, the gain ratio generating unit 230 may generate the first gain Ga using a gain ratio map having the vehicle speed Vs and the actual steering angle θh_act as parameters, and calculate the second gain Gb using the following equation (25).

[0295] Gb = 1 − Ga (25)

[0296] Furthermore, the first gain Ga and the second gain Gb may be generated using a gain ratio map having the vehicle speed Vs and the actual steering angle θt_act as parameters, without being limited to the gain ratio map having the vehicle speed Vs and the actual steering angle θh_act as parameters.

[0297] By providing the road surface reaction torque value generating unit 280 in the configuration according to the second embodiment including the gain ratio generating unit 230 described above, it is possible to apply a steering reaction force that appropriately reflects the road surface conditions. Furthermore, by providing the torque adjustment gain generating unit 290, for example, when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like, the driver can easily feel that the tires are slipping.

[0298] (Embodiment 3) 44 is a block diagram showing a configuration example of a steering torque target value generating unit according to embodiment 3. In embodiment 3, components and operations different from those in embodiment 1 will be described in detail, and descriptions of components and operations similar to those in embodiment 1 may be omitted.

[0299] By multiplying at least the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 by the torque gain Tref_Gain generated by the torque adjustment gain generating unit 290, the steering torque target value Th_ref is reduced when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface has significantly decreased due to rainfall, etc. This makes it easier for the driver to feel that the tires are slipping, but on the other hand, it makes the steering wheel more likely to spin, which may promote tire slippage.

[0300] A steering torque target value generating unit 200c according to the third embodiment includes a steering wheel return compensation unit 300 in addition to the configuration according to the first embodiment. Fig. 45 is a block diagram showing a configuration example of a torque adjustment gain generating unit according to the third embodiment. Fig. 46 is a block diagram showing a configuration example of the steering wheel return compensation unit.

[0301] The steering wheel return compensation unit 300 receives the torque component Trrf_div_inv and the actual steering angle θh_act generated by the torque adjusting gain generating unit 290a according to the third embodiment.

[0302] As described in the first embodiment, the torque component Trrf_div_inv is a torque component obtained by inverting the sign of the negative torque deviation Trrf_div, and is a positive value when the tires are slipping. The binarization processor 301 executes a threshold determination process on the torque component Trrf_div_inv, with 0 as the threshold. Specifically, the binarization processor 301 outputs "0" when the torque component Trrf_div_inv is equal to or less than 0, and outputs "1" when the torque component Trrf_div_inv exceeds 0. This generates a binary value Trrf_dev_bin that is "0" when the tires are not slipping and "1" when the tires are slipping.

[0303] A steering angle velocity |ωh_act| obtained by differentiating the actual steering angle θh_act by a differentiating section 302 and performing absolute value processing by an absolute value calculation section 303 is input to a steering angle velocity sensitive gain map section 304. The steering angle velocity sensitive gain map section 304 has a steering angle velocity sensitive gain map in which a gain Gc corresponding to the steering angle velocity |ωh_act| is set. The steering angle velocity sensitive gain map is stored, for example, in the ROM of the ECU constituting the control device 50. Fig. 47 is a diagram showing an example of the characteristics of the steering angle velocity sensitive gain map.

[0304] The steering angle velocity sensitive gain map unit 304 generates a gain Gc according to the steering angle velocity |ωh_act|, using the steering angle velocity sensitive gain map shown in FIG.

[0305] The gain Gc has a steering angular velocity-sensitive characteristic that increases according to the steering angular velocity |ωh_act|. More specifically, the gain Gc increases as the steering angular velocity |ωh_act| increases in the region equal to or greater than ω0, as shown in FIG.

[0306] The steering angular velocity ωh_act after the differentiation process is multiplied by the gain Gc generated by the steering angular velocity sensitive gain map unit 304 (multiplication unit 305), and then multiplied by the binary value Trrf_dev_bin (multiplication unit 306). This provides a torque value Tref_e0 that increases with an increase in the steering angular velocity ωh_act when the tires are slipping.

[0307] The output limiting unit 307 performs output limiting processing on the torque value Tref_e0. An upper limit value and a lower limit value for the torque value Tref_e0 are set in advance in the output limiting unit 307. The output limiting unit 307 outputs a torque compensation value Tref_e obtained by limiting the upper and lower limit values ​​of the torque value Tref_e0.

[0308] The steering torque target value generating unit 200c adds the torque compensation value Tref_e generated by the steering wheel return compensation unit 300 to the sum of the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 and the torque value Tref_d (second torque value) generated by the road surface reaction torque value generating unit 280 (adding unit 274). As a result, for example, when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like, the torque compensation value Tref_e that suppresses an increase in the steering speed (steering angular speed) is added, and the steering torque target value Th_ref increases.

[0309] Fig. 48 is a diagram conceptually showing an example of the behavior in the control device of the vehicle steering system according to the embodiment 3. Fig. 48 shows the behavior of the steering angle (dashed line) and the steering torque (solid line) when the driver performs additional steering of the steering wheel. Note that in the example shown in Fig. 48, the torque value Tref_b by the damping torque value generating unit 240 and the torque compensation value Tref_c by the hysteresis compensating unit 250 are not taken into consideration.

[0310] As described above, by multiplying at least the torque value Tref_a (first torque value) generated by the steering reaction torque value generating unit 210 by the torque gain Tref_Gain generated by the torque adjustment gain generating unit 290, the steering torque target value Th_ref is reduced when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface has significantly decreased due to rainfall, for example. This makes it easier for the driver to feel that the tires are slipping, but on the other hand, it makes the steering wheel more likely to spin, which may promote tire slippage.

[0311] The steering torque target value generating unit 200c according to the third embodiment includes the steering wheel return compensation unit 300, and therefore, when the tires are slipping while traveling on a low μ road where the frictional resistance of the road surface is significantly reduced due to rainfall or the like, a torque compensation value Tref_e that suppresses an increase in the steering speed (steering angular speed) is added, and the steering torque target value Th_ref increases. As a result, as shown by the solid line in Fig. 48, the steering torque increases more than in the first embodiment, and accordingly, as shown by the dashed line, the change in the steering angle is suppressed compared to the behavior in the first embodiment. This suppresses tire slippage, making it easier to recover the grip force.

[0312] The figures used in the above-described embodiments are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited to these. Also, the above-described embodiment is an example of a preferred embodiment of the present disclosure, but is not limited thereto, and various modifications can be made without departing from the scope of the present disclosure. [Explanation of symbols]

[0313] 1 Handle 2 Column Axis 3a, 3b tie rod 5L,5R steered wheels 6a,6b Arm 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, 200a, 200b, 200c Steering torque target value generating unit 210 Steering reaction torque value generating unit 211 Steering reaction torque map section 230 Gain ratio generation unit 230a first gain ratio generating unit 230b, 230c second gain ratio generating unit 231 Gain ratio calculation section 240 Damping torque value generator 241 Damping Gain Map Section 250 Hysteresis compensation section 251 Hysteresis compensation value calculation unit 280 Road reaction torque value generator 281 SAT Sensitive Torque Value Generator 281a SAT Estimation Division 281b SAT torque map section 282 Torque reference value generator 282a Torque reference map section 284 Deadband Processing Unit 290, 290a Torque adjustment gain generation unit 300 Handle return compensation part 400 Steering torque control unit 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 710 Feedforward compensation section 720 Addition section 730 PID control unit 740 Stabilization compensation section 750 Addition section 760 Output Limiter 770,770a Friction compensation section 771,771a Current compensation value calculation section 772 Differential part 773 Current Sensitive Gain Generator 774 Previous value storage unit 775 Absolute Value Calculation Unit 776 Multiplication section 800 Current control section

Claims

1. A control device for a vehicle steering system including a reaction device that drives a reaction motor that applies a steering reaction force to a steering wheel in accordance with a steering angle, and a steering device that drives a steering motor that steers steered wheels in accordance with the steering angle, a steering torque target value generating unit that generates a steering torque target value that is a target value of the steering torque of the steering wheel; a steering angle target value generating unit that generates a steering angle target value based on a steering angle; a steering angle control unit that generates a first steering motor current command value to be supplied to the steering motor based on the steering angle target value; Equipped with The steering torque target value generating unit a steering reaction torque value generating unit that generates a first torque value that increases or decreases according to at least a steering angle; a road reaction torque value generating unit that generates a second torque value according to a road surface condition; Equipped with The road surface reaction torque value generating unit is generating a self-aligning torque sensitive torque value which increases or decreases in accordance with a self-aligning torque estimated value estimated based on at least the first steering motor current command value, and a torque reference value which increases or decreases in accordance with at least the steering angle, and generating the second torque value based on a torque deviation obtained by subtracting the torque reference value from the self-aligning torque sensitive torque value; The steering torque target value generating unit generating the steering torque target value by adding at least the first torque value and the second torque value; A control device for a vehicle steering system.

2. the road surface reaction torque value generating unit increases the self-aligning torque sensitive torque value as the vehicle speed increases. The control device for a vehicle steering system according to claim 1.

3. The road surface reaction torque value generating unit increases the torque reference value as the vehicle speed increases. The control device for a vehicle steering system according to claim 2.

4. The road surface reaction torque value generating unit includes a dead band processing unit that sets a small range of the torque deviation to 0. The control device for a vehicle steering system according to claim 3.

5. The steering torque target value generating unit a torque adjustment gain generating unit that generates a torque gain of 1 or less to be multiplied by at least the first torque value when the torque deviation is a negative value; 5. The control device for a vehicle steering system according to claim 4.

6. the torque adjustment gain generating unit reduces the torque gain as the torque deviation of a negative value increases. The control device for a vehicle steering system according to claim 5.

7. The steering torque target value generating unit a gain ratio generating unit configured to generate a first gain by which the first torque value is multiplied and a second gain by which the second torque value is multiplied, The first gain is increased or decreased according to at least one of a vehicle speed and a steering angle of a vehicle, The sum of the second gain and the first gain is 1. The control device for a vehicle steering system according to claim 6.

8. The gain ratio generating unit decreases the first gain as the vehicle speed increases. The control device for a vehicle steering system according to claim 7.

9. The gain ratio generating unit decreases the first gain as the steering angle increases. The control device for a vehicle steering system according to claim 7.

10. The gain ratio generating unit decreases the first gain as the steering angle increases. The control device for a vehicle steering system according to claim 7.

11. The steering torque target value generating unit a steering return compensation unit that generates a torque compensation value that increases with an increase in steering angular velocity when the torque deviation is a negative value; The steering torque target value generating unit and further adding the torque compensation value to generate the steering torque target value. The control device for a vehicle steering system according to claim 6.

12. The steering angle control unit is a friction compensation unit that calculates a steering motor current compensation value that differs depending on whether the steered wheels are steered to the right or to the left, based on the steering angle target value; The steering angle control unit is generating a second turning motor current command value for driving the turning motor based on the first turning motor current command value and the turning motor current compensation value; A control device for a vehicle steering system according to any one of claims 1 to 11.

13. the steering motor current compensation value has a hysteresis characteristic according to a change in the steering angle target value. The control device for a vehicle steering system according to claim 12.

14. the steering motor current compensation value monotonically increases in a region from a first steering angle target value at the start of steering to a second steering angle target value obtained by adding a predetermined steering angle change amount threshold to the first steering angle target value or less, and becomes a constant value in a region larger than the second steering angle target value. The control device for a vehicle steering system according to claim 12.

15. The friction compensation unit increases or decreases the steering motor current compensation value in response to the second steering motor current command value. The control device for a vehicle steering system according to claim 12.

16. the steering motor current compensation value monotonically increases with an increase in the second steering motor current command value. The control device for a vehicle steering system according to claim 15.

17. a current compensation value calculation unit that calculates a first current compensation value; a current sensitive gain generating unit that generates a gain that monotonically increases as the second steering motor current command value increases; Equipped with the friction compensation unit multiplies the first current compensation value by the gain to calculate a second current compensation value; The control device for a vehicle steering system according to claim 16.

18. the friction compensation unit holds data in which the second turning motor current command value is associated with a gain that monotonically increases as the second turning motor current command value increases, and calculates the turning motor current compensation value based on the data. The control device for a vehicle steering system according to claim 16.

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