Vehicle steering system control device

Abstract

To provide a vehicle steering system control device that makes it possble to obtain a steering feel that reflects road surface conditions and the state of a vehicle. A steering torque target value generation unit (200) comprises a steering reaction force torque value generation unit (210) that generates a first torque value that increases or decreases in accordance with the steering angle, a road surface reaction force response torque compensation value generation unit (220) that generates a second torque value that increases or decreases in accordance with a road surface reaction force torque estimation value, a gain ratio generation unit (230) that generates a first gain (Ga) and a second gain (Gb) that change in terms of the the ratio therebetween in accordance with the vehicle speed, and a steering wheel return compensation unit (280) that generates a third torque value that decreases as the steering torque increases. A steering torque target value (Th_ref) is generated by adding a value obtained by multiplying the first torque value by the first gain (Ga), a value obtained by multiplying the second torque value by the second gain (Gb), and the third torque value.

Description

Vehicle steering system control device

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

[0002] One vehicle steering system is a steer-by-wire (SBW) system, in which a steering mechanism (FFA: Force Feedback Actuator) having a steering wheel operated by a driver and a road wheel actuator (RWA: Road Wheel Actuator) that steers the steered wheels are mechanically separated. In an SBW system, the steering mechanism and the road wheel actuator are electrically connected via an electronic control unit (ECU). The steering wheel operation is transmitted to the road wheel actuator via an electrical signal to steer the steered wheels, and the steering mechanism generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates the steering reaction force using a reaction actuator equipped with a reaction motor, and the road wheel actuator steers the steered wheels using 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 an SBW system in which the steering mechanism and the turning mechanism are mechanically separated, it is necessary to transmit to a reaction device the oversteer or understeer state that occurs when traveling on a low-μ road where the frictional resistance of the road surface is significantly reduced due to, for example, an icy road surface or hydroplaning in rainy weather. Patent Document 1 listed below discloses a vehicle steering device that estimates the reaction force (self-aligning torque) acting from the road surface and adds it to the reaction force generated in accordance with the steering angle, thereby reflecting the road surface conditions in the steering reaction force.

[0004] International Publication No. 2019 / 167661

[0005] The self-aligning torque varies depending on the road surface conditions as well as vehicle conditions such as vehicle speed and steering angle. With the above-mentioned conventional technology, depending on the vehicle condition, 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 provides a steering feel that reflects road conditions and the state of the vehicle.

[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 comprising a steering angle sensor that detects a steering angle of a steering wheel, a torque sensor that detects steering torque, a reaction force device that drives a reaction force motor that applies a steering reaction force to the steering wheel in accordance with the steering angle and the steering torque, and a steering device that drives a steering motor that steers steered wheels in accordance with the steering angle of the steering wheel, the control device for a vehicle steering system comprising a steering torque target value generation unit that generates a steering torque target value that is a target value of the steering torque, a steering angle target value generation unit that generates a steering angle target value that is a target value of the steering angle of the steered wheels, based on the steering angle, and a steering angle target value generation unit that generates a first steering motor current command value that is a target value of a current to be supplied to the steering motor, based on the steering angle target value. a control unit, wherein the steering torque target value generation unit comprises a steering reaction torque value generation unit that generates a first torque value that increases or decreases according to at least the steering angle; a road surface reaction force sensitive torque compensation value generation unit that generates a second torque value that increases or decreases according to at least a road surface reaction torque estimated value that is estimated based on at least the first steering motor current command value; a gain ratio generation unit that generates at least a first gain that increases or decreases according to a vehicle speed of the vehicle, and a second gain whose sum with the first gain is 1; and a steering wheel return compensation unit that generates at least a third torque value that decreases as the steering torque increases, and generates the steering torque target value by adding at least a value obtained by multiplying the first torque value by the first gain, a value obtained by multiplying the second torque value by the second gain, and the third torque value.

[0008] According to the above configuration, a steering reaction force corresponding to the road reaction torque estimate can be applied to the steering wheel at a ratio corresponding to at least the vehicle speed. This allows the driver to obtain a steering feel that reflects the road surface conditions and the vehicle state. Furthermore, a stable steering reaction force can be applied even when the vehicle is traveling at low speed on a low μ road.

[0009] In a preferred embodiment of the control device for a vehicle steering system, the gain ratio generating section preferably decreases the first gain as the vehicle speed increases.

[0010] According to the above configuration, a steering reaction force corresponding to the road reaction torque estimate can be applied to the steering wheel at a ratio according to the vehicle speed, thereby providing a steering feel that reflects the road surface conditions and the vehicle speed.

[0011] In a preferred aspect of the control device for a vehicle steering system, the steering wheel return compensation unit generates the third torque value by multiplying a torque value that decreases as the steering torque increases by a third gain that increases or decreases according to a steering angular velocity.

[0012] According to the above configuration, even when the vehicle is traveling at low speed on a low μ road, the third torque value can be generated in accordance with the steering angular velocity, thereby making it possible to apply a stable steering reaction force.

[0013] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering wheel return compensation unit increases the third gain as the steering angular velocity increases in a region where the steering angular velocity is equal to or less than a predetermined value, and decreases the third gain as the steering angular velocity increases when the steering angular velocity exceeds the predetermined value.

[0014] According to the above configuration, in a region where the steering angular velocity is equal to or less than a predetermined value, i.e., in a region where the steering wheel operation amount is small, the steering wheel can be returned to near the neutral position, thereby reducing the load on the driver.

[0015] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the steering wheel return compensation unit generates the third torque value by multiplying a torque value that decreases as the steering torque increases by a fourth gain corresponding to the ratio between the first gain and the second gain, and the steering torque target value generation unit further includes a damping torque value generation unit that generates a fourth torque value by multiplying a value obtained by multiplying a steering angular velocity by a damping gain that increases or decreases according to vehicle speed by a fifth gain corresponding to the ratio between the first gain and the second gain, and that the steering torque target value is generated by adding together the value obtained by multiplying the first torque value by the first gain, the value obtained by multiplying the second torque value by the second gain, the third torque value, and the fourth torque value.

[0016] According to the above configuration, by appropriately setting the ratio between the fourth gain and the fifth gain in accordance with the vehicle conditions, it is possible to obtain a steering feel that more appropriately reflects the road surface conditions and the vehicle state.

[0017] In a preferred embodiment of the control device for a vehicle steering system, the fourth gain may increase as the first gain increases, and the fifth gain may decrease as the first gain increases.

[0018] In a preferred embodiment of the control device for a vehicle steering system, the fourth gain may decrease as the first gain increases, and the fifth gain may increase as the first gain increases.

[0019] In a desirable aspect of the control device for a vehicle steering system, the steering angle control section includes a friction compensation section 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 target steering angle value, and the steering angle control section preferably 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.

[0020] According to the above configuration, friction compensation control can be performed effectively regardless of the steering speed of the driver, thereby reducing the sense of discomfort felt by the driver when the steering direction is changed from turning the steering wheel further to turning it back, or from turning it back to turning the steering wheel further.

[0021] In a preferred embodiment of the control device for a vehicle steering system, the steering motor current compensation value preferably has a hysteresis characteristic according to a change in the steering angle target value.

[0022] According to the above configuration, different turning motor current compensation values ​​are calculated when the steered wheels are turned right and when the steered wheels are turned left.

[0023] In a desirable aspect of the control device for a vehicle steering system, 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, and is a constant value in a region greater than the second steering angle target value.

[0024] With the above configuration, friction compensation control can be performed effectively from a state in which the steered wheels are stationary, regardless of the steering speed of the driver. 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 situations in which the driver's steering is extremely slow.

[0025] In a preferred aspect of the control device for a vehicle steering system, the friction compensation section preferably increases or decreases the steering motor current compensation value in accordance with the second steering motor current command value.

[0026] According to the above configuration, it is possible to realize friction compensation control according to the friction force caused by the gear torque.

[0027] In a preferred embodiment of the control device for a vehicle steering system, the turning motor current compensation value preferably increases monotonically as the second turning motor current command value increases.

[0028] 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.

[0029] A desirable aspect of the control device for a vehicle steering system is that it comprises 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.

[0030] 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.

[0031] In a preferred aspect of the control device for a vehicle steering system, the friction compensation section holds data relating the second turning motor current command value to 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.

[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] According to the present invention, a steering reaction force corresponding to an estimated road reaction torque value 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 allows the driver to obtain a steering feel that reflects the road conditions and the state of the vehicle.

[0034] FIG. 1 is a configuration diagram showing an example of an overview of an SBW system including a control device according to the present disclosure. FIG. 2 is a schematic diagram showing a hardware configuration of an ECU. FIG. 3 is a diagram showing an example of a control block configuration of a control device according to the present disclosure. FIG. 4 is a block diagram showing an example of a configuration of a steering angle control unit. FIG. 5 is a block diagram showing an example of a configuration of a friction compensation unit. FIG. 6 is a diagram showing an example of a characteristic of a first current compensation value in a current compensation value calculation unit. FIG. 7A is a diagram showing a first example of a current sensitive gain map. FIG. 7B is a diagram showing a second example of a current sensitive gain map. FIG. 8 is a diagram showing an example of an output characteristic of a friction compensation unit. FIG. 9 is a block diagram showing an example of a configuration of a friction compensation unit according to a modified example. FIG. 10A is a first conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. FIG. 10B is a first conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. FIG. 11A is a second conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. FIG. 11B is a second conceptual diagram illustrating a specific example of friction compensation control by the friction compensation unit. FIG. 12 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to the first embodiment. FIG. 13 is a block diagram showing an example of the configuration of a steering reaction force torque value generating unit. FIG. 14A is a diagram showing an example of the characteristics of a basic map. FIG. 14B is a diagram showing an example of the characteristics of the torque value Tref_a. FIG. 15 is a block diagram showing an example of the configuration of a damping torque value generating unit according to the first embodiment. FIG. 16A is a diagram showing an example of the characteristics of a damping gain map. FIG. 16B is a conceptual diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. FIG. 17 is a region diagram for explaining the steering direction in the present disclosure. FIG. 18 is a block diagram showing an example of the configuration of a hysteresis compensating unit. FIG. 19 is a diagram showing an example of the output characteristics of the hysteresis compensating unit. FIG. 20 is a block diagram showing an example of the configuration of a road surface reaction force sensitive torque compensation value generating unit. FIG. 21 is an image diagram showing the state of torque generated between the road surface and the steering motor. FIG. 22 is a block diagram showing an example of the configuration of a road surface reaction force torque estimating unit. Fig. 23 is a conceptual diagram for explaining a method for calculating the actual road surface reaction torque acting on the steering mechanism. Fig. 24 is a conceptual diagram showing a configuration for executing a simulation for deriving the transfer function Gfil.FIG. 25 is a diagram showing an example characteristic of a road reaction force sensitive torque map. FIG. 26 is a diagram conceptually showing an example characteristic of a second torque value after sign conversion. FIG. 27A is a diagram conceptually showing a first example of a gain ratio setting example when vehicle speed is used as a parameter. FIG. 27B is a diagram conceptually showing a second example of a gain ratio setting example when vehicle speed is used as a parameter. FIG. 27C is a diagram conceptually showing a third example of a gain ratio setting example when vehicle speed is used as a parameter. FIG. 28 is a diagram conceptually showing an example of a gain ratio setting example when actual steering angle is used as a parameter. FIG. 29 is a diagram conceptually showing an example of a gain ratio setting example when actual steering angle is used as a parameter. FIG. 30 is a block diagram showing an example configuration of a gain ratio generation unit when vehicle speed and actual steering angle are used as parameters. FIG. 31A is a diagram conceptually showing an example of a gain ratio setting example when vehicle speed is used as a parameter. FIG. 31B is a diagram conceptually showing an example of a gain ratio setting example when actual steering angle is used as a parameter. FIG. 32 is a block diagram showing an example of the configuration of a gain ratio generation unit when vehicle speed and actual steering angle are used as parameters. FIG. 33A is a diagram conceptually showing an example of a gain ratio setting example using vehicle speed as a parameter. FIG. 33B is a diagram conceptually showing an example of a gain ratio setting example using actual steering angle as a parameter. FIG. 34 is a 3D map conceptually showing an example of a gain ratio generation method. FIG. 35 is a block diagram showing an example of the configuration of a steering wheel return compensation unit according to the first embodiment. FIG. 36 is a diagram showing an example of the characteristics of an actual torque sensitive torque map. FIG. 37 is a diagram showing an example of the characteristics of a steering angular velocity sensitive gain map. FIG. 38 is a diagram conceptually explaining a specific example of the effect of the steering wheel return compensation unit according to the first embodiment. FIG. 39 is a block diagram showing an example of the configuration of a steering torque target value generation unit according to the second embodiment. FIG. 40 is a block diagram showing an example of the configuration of a steering wheel return compensation unit according to the second embodiment. FIG. 41 is a block diagram showing an example of the configuration of a damping torque value generation unit according to the second embodiment. FIG. 42A is a diagram showing a first example of characteristics of a gain ratio sensitive gain map of the steering wheel return compensation unit. 42B is a diagram showing a first example of a characteristic of a gain ratio sensitive gain map of a damping torque value generator. FIG. 43A is a diagram showing a second example of a characteristic of a gain ratio sensitive gain map of a steering return compensation unit.Fig. 43B is a diagram showing a second example of a characteristic of the gain ratio sensitive gain map of the damping torque value generation unit. Fig. 44A is a diagram showing a third example of a characteristic of the gain ratio sensitive gain map of the steering wheel return compensation unit damping torque value generation unit. Fig. 44B is a diagram showing a third example of a characteristic of the gain ratio sensitive gain map of the damping torque value generation unit. Fig. 45A is a diagram showing a fourth example of a characteristic of the gain ratio sensitive gain map of the steering wheel return compensation unit damping torque value generation unit. Fig. 45B is a diagram showing a fourth example of a characteristic of the gain ratio sensitive gain map of the damping torque value generation unit. Fig. 46 is a diagram conceptually explaining a specific example of the effect of the steering wheel return compensation unit according to the second embodiment.

[0035] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0036] 1 is a block diagram showing an example of an outline of an SBW system including a control device according to the present disclosure, which includes a reaction force device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

[0037] 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.

[0038] The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotational speed of the reaction force motor 31. The reaction force device 30 transmits the vehicle's motion state, which is transmitted from the steered wheels 5L, 5R, to the driver as a steering reaction force. The reaction force motor 31 applies the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

[0039] 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."

[0040] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point, which is the limit of possible steering, is provided on the column shaft 2. In other words, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0041] The steering device 40 includes a steering motor 41, a speed reduction mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 44 that converts the rotational motion of the steering motor 41 into linear motion. The steering device 40 drives the steering motor 41 in accordance with the steering angle θh, and the resulting drive force is applied to the pinion rack mechanism 44 via the speed reduction mechanism 42, and the drive force is passed through the tie rods 3a and 3b to steer the steerable wheels 5L and 5R. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steerable wheels 5L and 5R. Instead of the steering angle θt of the steerable wheels 5L and 5R, for example, the motor angle of the steering motor 41 or the position of the rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 will also be referred to as the "actual steering angle θt_act."

[0042] In the present disclosure, the actual steering angle θh_act and the actual turning angle θt_act are also collectively referred to simply as the "steering angle" of the vehicle.

[0043] In order to cooperatively control the reaction force device 30 and the steering device 40, the control device 50 generates a voltage control command value Vh_ref for driving and controlling the reaction force motor 31 and a voltage control command value Vt_ref for driving and controlling the steering motor 41 based on information such as the steering angle θh and the steering angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

[0044] 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, the control device 50 can also be connected to a non-CAN 21 that transmits and receives communications other than the CAN 20, analog / digital signals, radio waves, etc.

[0045] Specifically, the control device 50 is, for example, an ECU (Electronic Control Unit) mounted on a vehicle. The ECU is mainly composed of a CPU (including an MCU, an MPU, etc.). FIG. 2 is a schematic diagram showing the hardware configuration of the ECU. 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.

[0046] 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 a single 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.

[0047] The ROM 102 is used as a memory for storing the control program and control data used when the control program is executed, and the RAM 103 is used as a work memory for running the control program.

[0048] EEPROM 104 is a non-volatile memory that can retain its contents even after power is cut off, and stores control data and the like used by CPU 101 to execute a control program. The various data stored in EEPROM 104 is used in the control program loaded in RAM 103 after power is turned on to ECU 110, and is overwritten in EEPROM 104 at a predetermined timing. Note that, although 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) and SDRAM may also be used.

[0049] FIG. 3 is a diagram showing an example of a control block configuration of a control device according to the present disclosure. In FIG. 3, reaction force device 30 includes, in addition to reaction force motor 31 and the above-described configuration, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. Furthermore, turning device 40 includes, in addition to steering motor 41 and the above-described configuration, a PWM control unit 47, an inverter 48, and a motor current detector 49. Control device 50 implements the control blocks of reaction force control system 60, which controls reaction force device 30, and steering control system 70, which controls steering device 40. Reaction force control system 60 and steering control system 70 cooperate to control reaction force device 30 and steering device 40. Note that when control device 50 is configured to include a reaction force control ECU and a steering control ECU, reaction force control system 60 may be implemented by the reaction force control ECU, and steering control system 70 may be implemented 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.

[0050] 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 turning control system 70 is realized by a turning control program executed in ECU 110. Note that some or all of the control blocks in 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.

[0051] As shown in Fig. 3, control device 50 includes, as control blocks, steering torque target value generation section 200, steering torque control section 400, current control section 500, turning angle target value generation section 600, turning angle control section 700, and current control section 800. Steering torque target value generation section 200, steering torque control section 400, and current control section 500 are control blocks that make up reaction force control system 60. Turning angle target value generation section 600, turning angle control section 700, and current control section 800 are control blocks that make up steering control system 70.

[0052] The reaction force control system 60 performs control such that the actual steering torque Th_act detected by the torque sensor 34 follows the steering torque target value Th_ref, which is the target value of the steering torque of the reaction force device 30 .

[0053] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0054] 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 that brings the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act closer to zero, and limits the output of the current command value by an output limiting unit to the upper and lower limit values, thereby calculating the reaction force motor current command value Ih_ref.

[0055] The current control unit 500 controls the current of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the 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.

[0056] 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.

[0057] The steering control system 70 performs control such that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

[0058] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0059] Steering angle control unit 700 generates second steering motor current command value It_ref for driving steering motor 41. Specifically, steering angle control unit 700 generates first steering motor current command value Iref_a, which is a control target value for 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 compensator on first steering motor current command value Iref_a to calculate second steering motor current command value It_ref. While an example in which a friction compensator is provided in steering angle control unit 700 will be described below, a configuration that does not include a friction compensator is also possible. Note that in a configuration that does not include a friction compensator, first steering motor current command value Iref_a after PID control is generated as second steering motor current command value It_ref.

[0060] Current control unit 800 controls the current of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that deviation It_err between second steering motor current command value It_ref output from steering angle control unit 700 and actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0061] In the steering device 40, the steering motor 41 is controlled and driven via a PWM control unit 47 and an inverter 48 based on the voltage control command value Vt_ref.

[0062] In this embodiment, the steering torque control unit 400, the current control unit 500, the steering angle target value generation unit 600, and the current control unit 800 may 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.

[0063] Here, the steering angle control unit 700 will be described. Fig. 4 is a block diagram showing an example 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 and 750.

[0064] Feedforward compensation section 710 is configured with a filter (FF filter) for improving the ability of actual turning angle θt_act to follow target turning angle value θt_ref. Feedforward compensation section 710 performs filtering on target turning angle value θt_ref. Specifically, for example, an LPF having a first-order or second-order delay 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 delay in the follow-up of actual turning angle θt_act to target turning angle value θt_ref.

[0065] PID control section 730 performs PID control so that deviation θt_err between target turning angle value θt_ref, which is the calculation result of addition section 720, and actual turning angle θt_act approaches zero.

[0066] The stabilization compensation unit 740 is configured with a filter (stabilization filter) having transfer characteristics required for stabilizing control. The stabilization compensation unit 740 performs filtering on the output value of the PID control unit 730.

[0067] Output limiting section 760 performs output limiting processing on current command value Iref_c, which is the calculation result of adder 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 for 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.

[0068] It should be noted that the above-described 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.

[0069] Friction compensation section 770 calculates second current compensation value Iref_b to compensate for the delay in response of actual turning angle θt_act to turning angle target value θt_ref, which occurs due to friction in the turning mechanism, based on turning angle target value θt_ref. The specific configuration and operation of friction compensation section 770 will be described in detail below.

[0070] 5 is a block diagram showing an example of the configuration of the friction compensation unit 770. As shown in FIG. 5, the friction compensation unit 770 includes, as its main components, a current compensation value calculation unit 771 and a current sensitive gain generation unit 773.

[0071] Current compensation value calculation section 771 receives as input the target turning angle value θt_ref and the target turning speed value ωt_ref calculated by differentiating the target turning angle value θt_ref by differentiating section 772. Current compensation value calculation section 771 calculates a first current compensation value Iref_b0 based on the target turning angle value θt_ref and the target turning speed value ωt_ref.

[0072] The method of calculating the first current compensation value Iref_b0 in the current compensation value calculation unit 771 will be described below.

[0073] 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 represents the steering angle target value θt_ref, and the vertical axis represents the first current compensation value Iref_b0. Also in FIG. 6, the solid line represents the first current compensation value Iref_b0 when steering to the right, and the dashed line represents 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 in which it takes different values ​​when steering to the left and when steering to the right. L1 shown in FIG. 6 represents the locus when the steered wheels 5L, 5R are steered to the right from the center position (origin (0,0)), and L2 represents the coordinate A (x １ , y １ ) indicates the locus when a change from right steering to left steering occurs, and L3 indicates the locus when the coordinate B (x ２ , y ２ ) shows the trajectory when a switch from right steering to left steering occurs.

[0074] Current compensation value calculator 771 calculates first current compensation value Iref_b0 using the following equations (1) and (2) based on the steering angle target value θt_ref and the steering speed target value ωt_ref. Specifically, when the sign ωt_ref(sgn) of the steering speed target value ωt_ref is a positive value ("+"), it calculates first current compensation value Iref_b0 using the following equation (1), and when the sign ωt_ref(sgn) of the steering speed target value ωt_ref is a negative value ("-"), it calculates first current compensation value Iref_b0 using the following equation (2). In the following equations (1) and (2), x represents the steering speed target value ωt_ref, y represents 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 left. 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.

[0075] y Ｒ = Ahys{1-a －ｃ（ｘ－ｂ）} ... (1)

[0076] y Ｌ =-Ahys{1-a ｃ（ｘ－ｂ’）} ... (2)

[0077] 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.

[0078] 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 equation (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 takes over the previous values ​​of steering angle target value θt_ref and first current compensation value Iref_b0 (coordinates A(x １ , y １ )) into the above equation (2), and substitute the coefficient b' shown in the following equation (4) to calculate the first current compensation value Iref_b0. Also, when a switch from left steering to right steering occurs (ωt_ref(sgn) = "-" → "+"), the current compensation value calculation unit 771 calculates the first current compensation value Iref_b0 by applying the steering angle target value θt_ref and the previous value of the first current compensation value Iref_b0 (coordinates B(x ２ , y ２ )) is applied to the above equation (1), and a coefficient b shown in the following equation (3) is substituted to calculate the first current compensation value Iref_b0.

[0079] b = x １ +(1 / c) log ａ {1-(y １ / Ahys)}...(3)

[0080] b' = x １ −(1 / c) log ａ {1-(y １ / Ahys)}...(4)

[0081] The above formulas (3) and (4) are obtained by adding x to x in the above formulas (1) and (2). １ Substituting, y Ｒ and y Ｌ Niy １ It can be derived by substituting

[0082] When Napier's constant e is used as the coefficient a, the above equations (1), (2), (3), and (4) can be expressed by the following equations (5), (6), (7), and (8), respectively.

[0083] y Ｒ =Ahys[1-exp{-c(x-b)}]...(5)

[0084] y Ｌ =-Ahys[{1-exp{c(x-b')}]...(6)

[0085] b = x １ +(1 / c) log ｅ {1-(y １ / Ahys)}...(7)

[0086] b' = x １ −(1 / c) log ｅ {1-(y １ / Ahys)}...(8)

[0087] Returning to Figure 5, previous value holding section 774 holds the 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 processing. Previous value holding section 774 is formed, for example, by a RAM of an ECU constituting control device 50.

[0088] In the present disclosure, absolute value calculation section 775 performs absolute value processing on the previous output value It_ref′ of turning angle control section 700 output from previous value holding section 774 .

[0089] Current sensitive gain generation section 773 receives as input the previous output value |It_ref'| of steering angle control section 700 that has been subjected to absolute value processing in absolute value calculation section 775. Current sensitive gain generation section 773 generates gain Gi according to the previous output value |It_ref'| of steering angle control section 700.

[0090] 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 that constitutes 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.

[0091] The first example of the current-sensitive gain map shown in Figure 7A has a current-value-sensitive characteristic in which gain Gi increases or decreases in accordance with the previous output value |It_ref'| of turning angle control unit 700. More specifically, as shown in Figure 7A, gain Gi monotonically increases as the previous output value |It_ref'| of turning angle control unit 700 increases.

[0092] 8 is a diagram showing an example of the output characteristics of the friction compensation unit, in which the horizontal axis represents the target steering angle value θt_ref and the vertical axis represents the second current compensation value Iref_b.

[0093] The frictional force generated in the steering mechanism includes friction due to gear torque between steering motor 41 and reduction mechanism 42. Gear torque refers to torque resulting from 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 at the meshing portion between the worm gear and the worm wheel can be defined as gear torque. The frictional force due to this gear torque increases monotonically with motor current.

[0094] In the present disclosure, friction compensation section 770 calculates second current compensation value Iref_b by multiplying (multiplication section 776) first current compensation value Iref_b0 output from current compensation value calculation section 771 by gain Gi generated by current sensitive gain generation section 773. As a result, as shown in Fig. 8, a characteristic is obtained in which the output width of the hysteresis characteristic (width of second current compensation value Iref_b) increases or decreases in accordance with second turning motor current command value It_ref, and friction compensation control in accordance with the friction force caused by gear torque can be achieved.

[0095] Specifically, when second turning motor current command value It_ref is relatively large, gear torque becomes relatively large and frictional force caused by the gear torque acts strongly. Under such circumstances, by multiplying first current compensation value Iref_b0 output from current compensation value calculation section 771 by 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.

[0096] Furthermore, when 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 smaller. Under such circumstances, by multiplying first current compensation value Iref_b0 output from current compensation value calculation section 771 by 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.

[0097] 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, second current compensation value Iref_b may be calculated by multiplying first current compensation value Iref_b0 output from current compensation value calculation unit 771 by a constant gain Gi=k (for example, k=1), without depending on second turning motor current command value It_ref (previous output value |It_ref'| of turning angle control unit 700).

[0098] Second current compensation value Iref_b output from friction compensation section 770 is added by addition section 750 shown in FIG. 4 to first turning motor current command value Iref_a output from stabilization compensation section 740, and second turning motor current command value It_ref, which is obtained by output limiting section 760 limiting the output of current command value Iref_c after the addition, is output.

[0099] FIG. 9 is a block diagram showing an example configuration of a friction compensation unit according to a modified example. In the example configuration of friction compensation unit 770a shown in FIG. 5, first current compensation value Iref_b0 output from current compensation value calculation unit 771 is multiplied by gain Gi generated by current sensitive gain generation unit 773. However, in the modified example shown in FIG. 9, current compensation value calculation unit 771a may be configured to hold a table (data) that associates second turning motor current command value It_ref (previous output value |It_ref'| of turning angle control unit 700) with coefficient Ahys in equations (6) to (13) above, and to obtain a characteristic in which the output width of the hysteresis characteristic (width of second current compensation value Iref_b) increases or decreases depending on second turning motor current command value It_ref, as shown in FIG. 8. This data, like the current sensitive gain map, can be stored, for example, in the ROM of the ECU constituting control device 50. As a result, similar to the configuration shown in FIG. 5, friction compensation control according to the friction force caused by the gear torque can be realized.

[0100] Note that the present invention is not limited to the embodiment in which steering speed target value ωt_ref is obtained by differentiating steering angle target value θt_ref, and may instead be an embodiment in which it is determined that the steering direction has been switched using the motor angular velocity of steering motor 41. Also, a configuration may be adopted in which a filter is provided in a stage preceding current compensation value calculation section 771 and current sensitive gain generation section 773, or a configuration in which a filter is provided in a stage subsequent to current sensitive gain generation section 773. Furthermore, a configuration may be adopted in which a limiter that performs output limiting processing on second current compensation value Iref_b is provided in a stage subsequent to friction compensation section 770, similar to output limiting section 760 described above.

[0101] Figures 10A and 10B are first conceptual diagrams illustrating a specific example of friction compensation control by the friction compensation unit. In Figures 10A and 10B, the horizontal axis represents time, and the vertical axis represents steering angle. The dashed lines in Figures 10A and 10B represent steering angle target value θt_ref, and the solid lines represent actual steering angle θt_act. Figure 10A illustrates a time response when friction compensation control by friction compensation unit 770 is not performed. Figure 10B illustrates a time response when friction compensation control by friction compensation unit 770 is performed.

[0102] The examples shown in Figures 10A and 10B show time responses when steered wheels 5L, 5R are steered left and right from their center positions at a relatively fast predetermined frequency. When friction compensation control by friction compensation unit 770 is not performed, as shown in Figure 10A, distortion occurs in actual steering angle θt_act when the steering direction is changed, as enclosed by the dashed line. In this case, when the driver switches the steering direction from turning the steering wheel further to steering back, or from steering back to turning further, a discrepancy occurs between the operation (steering) of steering wheel 1 and the steering of steered wheels 5L, 5R, which may cause the driver to feel uncomfortable. In contrast, when friction compensation control by friction compensation unit 770 is performed, distortion in actual steering angle θt_act is suppressed when the steering direction is changed, as enclosed by the dashed line, as shown in Figure 10B.

[0103] To explain in more detail, when the steering angle target value θt_ref switches when the steering direction is switched, the steering speed target value ωt_ref becomes approximately zero, but because the first current compensation value Iref_b0 is determined in accordance with the steering angle target value θt_ref, the friction compensation unit 770 can perform predetermined friction compensation control even when the steering speed target value ωt_ref is approximately zero.

[0104] This reduces the sense of discomfort felt by the driver when the steering direction is switched from further turning to returning, or from returning to further turning.

[0105] 11A and 11B are second conceptual diagrams illustrating a specific example of friction compensation control by the friction compensation unit. In FIGS. 11A and 11B, the horizontal axis represents time, and the vertical axis represents steering angle. The dashed lines in FIGS. 11A and 11B represent steering angle target value θt_ref, and the solid lines represent actual steering angle θt_act. FIG. 11A illustrates a time response when friction compensation control is performed in accordance with 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.

[0106] The examples shown in Figures 11A and 11B show time responses when the steering is performed more slightly to the left or right than in Figures 10A and 10B. When friction compensation control is performed in accordance with steering speed target value ωt_ref according to the comparative example, as shown in Figure 11A, when the steering is performed slightly to the left or right, distortion occurs in actual steering angle θt_act when the steering direction is switched as surrounded by the 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 when the steering direction is switched as surrounded by the dashed line is suppressed even when the steering is performed slightly to the left or right.

[0107] To explain in more detail, if the steering wheel is operated slowly and minutely and slowly, when the steering direction is switched, as in the example of Figures 10A and 10B, when steering angle target value θt_ref switches, steering speed target value ωt_ref becomes approximately zero. Here, unlike the example of Figures 10A and 10B, steering angle target value θt_ref also takes a value close to zero, and so first current compensation value Iref_b0 output from current compensation value calculation unit 771 also becomes a small value, but by multiplying first current compensation value Iref_b0 by gain Gi calculated by current sensitive gain generation unit 773, it is possible to prevent second current compensation value Iref_b from becoming too small.

[0108] This reduces the sense of discomfort felt by the driver when the steering direction of the driver's steering wheel is changed from turning more to turning back, or from turning back to turning more, even in a situation where the driver's steering operation is slight.

[0109] As described above, steering angle control section 700 is provided with friction compensation section 770 and is configured to calculate, based on steering angle target value θt_ref, second current compensation value Iref_b for compensating for the delay in response of actual steering angle θt_act to steering angle target value θt_ref caused by friction in the steering mechanism, thereby enabling friction compensation control to be performed effectively and appropriately regardless of the steering wheel operation speed by the driver.

[0110] Furthermore, as described above, by setting the second current compensation value Iref_b to have a characteristic that increases or decreases in accordance with the second turning motor current command value It_ref, it is possible to realize friction compensation control in accordance with the friction force caused by the gear torque.

[0111] (Embodiment 1) Hereinafter, a steering torque target value generating unit 200 according to embodiment 1 will be described. Fig. 12 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to embodiment 1. As shown in Fig. 12, the steering torque target value generating unit 200 according to embodiment 1 includes, as main components, a steering reaction torque value generating unit 210, a road surface reaction force sensitive torque compensation value generating unit 220, a gain ratio generating unit 230, a damping torque value generating unit 240, a hysteresis compensating unit 250, and a steering wheel return compensating unit 280.

[0112] First, the steering reaction torque value generator 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 generator.

[0113] 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.

[0114] 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 force torque map unit 211. The steering reaction force torque value generation unit 210 generates a torque value Tref_a0 using the basic map shown in Fig. 14A with the vehicle speed Vs as a parameter. The torque value Tref_a0 is used to generate a basic steering reaction force according to the steering angle |θh| and the vehicle speed Vs.

[0115] The torque value Tref_a0 has an angle-sensitive characteristic that increases or decreases according to the steering angle |θh|. More specifically, as shown in FIG. 14A , the torque value Tref_a0 increases as the steering angle |θh| increases. Furthermore, the torque value Tref_a0 has a vehicle-speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. More specifically, as shown in FIG. 14A , the torque value Tref_a0 increases as the vehicle speed Vs increases. That is, the reaction force obtained by the torque value Tref_a0 derived from 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 also increases as the vehicle speed (vehicle speed Vs) increases. Note that although the basic map shown in FIG. 14A has a vehicle-speed-sensitive characteristic, the present invention is not limited to this.

[0116] Fig. 14B is a diagram showing an example of the characteristics of the torque value Tref_a. The torque value Tref_a (first torque value) shown in Fig. 14B is obtained by multiplying the torque value Tref_a0 output from the steering reaction force torque map unit 211 by the sign function Sgn(θh) output from the sign extraction unit 213 in the multiplication unit 293. Note that a configuration may be adopted in which the sign extraction unit 213 is not provided, and 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.

[0117] 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.

[0118] The damping torque value generation 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 the characteristics 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 using the damping gain map shown in Fig. 16A.

[0119] 16A, the damping gain DG has a vehicle speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. In the damping torque value generation unit 240, a multiplication unit 243 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 differentiation unit 242 by the damper gain DG output from the damping gain map unit 241, and outputs the result as a torque value Tref_b.

[0120] 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 in proportion to the steering angular velocity ωh.

[0121] Fig. 16B is a conceptual diagram showing an example of the characteristic 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).

[0122] 17 is a region diagram for explaining the steering direction in the present disclosure, in which the horizontal axis represents the steering angle θh and the vertical axis represents the steering angular velocity ωh.

[0123] Region A ((θh, ωh) = (+, +)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned further to the right (ωh > 0). Region B ((θh, ωh) = (+, -)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned back to the left (ωh < 0). Region C ((θh, ωh) = (-, -)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned further to the left (ωh < 0). Region D ((θh, ωh) = (-, +)) shown in FIG. 17 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned back to the right (ωh > 0). Also, in Figure 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)).

[0124] The torque value Tref_b output from the damping torque value generation unit 240 is positive in regions A and D where the steering angular velocity ωh>0 and negative in regions B and C where the steering angular velocity ωh<0. As a result, when the steering angular velocity ωh>0, i.e., in region A where the steering wheel 1 is turned to the right (θh>0) and further turned rightward, or in region D where the steering wheel 1 is turned to the left (θh<0) and turned back rightward, the torque value Tref_b is a value obtained by adding |Tref_b| to Tref_a, as shown by the solid line in FIG. 16B. When the steering angular velocity ωh<0, i.e., in region B where the steering wheel 1 is turned to the right (θh>0) and turned back leftward, or in region C where the steering wheel 1 is turned to the left (θh<0) and turned further leftward, the torque value Tref_b is a value obtained by subtracting |Tref_b| from Tref_a, as shown by the dashed line in FIG. 16B.

[0125] 16B, the torque value Tref_a+Tref_b increases with increasing steering angle θ, and the torque increases less with increasing steering angle θ as the steering angle θh 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.

[0126] Next, the hysteresis compensator 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 compensator.

[0127] The hysteresis compensation value calculation unit 251 receives 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 unit 252. The hysteresis compensation value calculation unit 251 calculates a torque compensation value Tref_c based on the actual steering angle θh_act and the steering angular velocity ωh_act. A method for calculating the torque compensation value Tref_c in the hysteresis compensation value calculation unit 251 will be described below.

[0128] FIG. 19 is a diagram showing an example of the output characteristic of the hysteresis compensation unit. In FIG. 19, the horizontal axis represents the actual steering angle θh_act, and the vertical axis represents the torque compensation value Tref_c. Also in FIG. 19, the solid line represents the torque compensation value Tref_c when steering to the right, and the dashed line represents 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 in which the value is different when steering to the left and when steering to the right. L1 shown in FIG. 19 indicates the locus when steering to the right from the center position (origin (0,0)) of the steering wheel 1, and L2 indicates the coordinate A (x １ , y １ ) indicates the trajectory when a switch from right steering to left steering occurs, and L3 indicates the trajectory when the coordinate B (x ２ , y ２ ) shows the trajectory when a switch from right steering to left steering occurs.

[0129] 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 when steering to the left. 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 that indicates the roundness of the hysteresis characteristic.

[0130] y Ｒ = Ahys{1-a －ｃ（ｘ－ｂ） ... (9)

[0131] y Ｌ =-Ahys{1-a ｃ（ｘ－ｂ’）} ... (10)

[0132] 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.

[0133] 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 takes over the previous values ​​of the actual steering angle θh_act and the torque compensation value Tref_c (coordinates A(x １ , y １ )) into the above equation (10), and substitute the coefficient b' shown in the following equation (12) to calculate the torque compensation value Tref_c. In addition, when a switch from left steering to right steering occurs (ωh_act(sgn) = "-" → "+"), the hysteresis compensation value calculation unit 251 calculates the actual steering angle θh_act and the previous value of the torque compensation value Tref_c (coordinates B(x ２ , y ２ )) is applied to the above equation (9), and a coefficient b shown in the following equation (11) is substituted to calculate the torque compensation value Tref_c.

[0134] b = x １ +(1 / c) log ａ {1-(y １ / Ahys)}...(11)

[0135] b' = x １ −(1 / c) log ａ {1-(y １ / Ahys)}...(12)

[0136] The above formulas (11) and (12) are expressed by the formulas (9) and (10) with x added to x. １ Substituting, y Ｒ and y Ｌ Niy １ It can be derived by substituting

[0137] When Napier's constant e is used as the coefficient a, the above equations (9), (10), (11), and (12) can be expressed as the following equations (13), (14), (15), and (16), respectively.

[0138] y Ｒ =Ahys[1-exp{-c(x-b)}]...(13)

[0139] y Ｌ =-Ahys[{1-exp{c(x-b')}]...(14)

[0140] b = x １ +(1 / c) log ｅ {1-(y １ / Ahys)}...(15)

[0141] b' = x １ −(1 / c) log ｅ {1-(y １ / Ahys)}...(16)

[0142] As described above, the SBW system does not have an intermediate shaft mechanically coupled 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 to the reaction device 30 the steering reaction force when the vehicle is oversteered or understeered, for example, when traveling on a low-μ road where the road surface friction resistance is significantly reduced due to an icy road surface or hydroplaning during rainy weather.

[0143] In the present disclosure, as shown in Fig. 12, road reaction force sensitive torque compensation value generation section 220 is provided as a component of steering torque target value generation section 200, and a road reaction force torque corresponding to first steering motor current command value Iref_a generated by steering angle control section 700 is estimated, and a torque value (second torque value) corresponding to the estimated road reaction force torque is applied to steering torque target value Th_ref. This makes it possible to apply a steering reaction force corresponding to the estimated value of road reaction force torque to steering wheel 1. Below, a detailed description will be given of the configuration and operation that can apply a steering reaction force corresponding to the estimated value of road reaction force torque to steering wheel 1.

[0144] 20 is a block diagram showing an example of the configuration of the road reaction force sensitive torque compensation value generator 220. The road reaction force sensitive torque compensation value generator 220 includes a road reaction force torque estimator 221 and a road reaction force sensitive torque map unit 222 as main components.

[0145] First, the method of estimating the road surface reaction torque estimated value Tsat_est in the road surface reaction torque estimating section 221 will be described with reference to FIGS. 21 and 22. FIG.

[0146] FIG. 21 is an image diagram showing the state of torque generated between the road surface and the steering motor.

[0147] When the driver steers the steering wheel, a target steering angle value θt_ref is generated, and in accordance with the target steering angle value θt_ref, the steering motor 41 generates a steering motor torque Tm that steers the steerable wheels 5L, 5R. As a result, the steerable wheels 5L, 5R are steered, and the road surface reaction torque T ＳＡＴ At this time, torque is generated as resistance due to inertia (pinion shaft converted inertia) J acting on the pinion shaft by the steering motor 41 (its rotor), the reduction mechanism, etc. Furthermore, the damper term (damper coefficient D Ｍ ) A physical torque (viscous torque) is generated. From the balance of these forces, the equation of motion shown in the following equation (17) is obtained.

[0148] J×α Ｍ +D Ｍ ×ω Ｍ = Tm-T ＳＡＴ ...(17)

[0149] In the above formula (17), ω Ｍ is the motor angular velocity converted to the pinion axis (value relative to the pinion axis), and α Ｍ is the motor angular acceleration converted to the pinion shaft. Then, the above equation (17) is used to calculate the road reaction torque T ＳＡＴ When solving for, the following equation (18) is obtained.

[0150] T ＳＡＴ = Tm-J×α Ｍ -D Ｍ ×ω Ｍ ...(18)

[0151] As can be seen from the above equation (18), the pinion shaft converted inertia J and the damper coefficient D Ｍ is calculated as a constant in advance, the motor angular velocity ω Ｍ , motor angular acceleration α Ｍ , and the road surface reaction torque T ＳＡＴ The pinion shaft converted inertia J may be simply converted to a value corresponding to the pinion shaft using a relational expression between the motor inertia and the reduction ratio.

[0152] Road surface reaction torque estimating section 221 receives as input first steering motor current command value Iref_a and actual steering angle θt_act generated by steering angle control section 700. Road surface reaction torque estimating section 221 estimates road surface reaction torque T ＳＡＴ is replaced with the road surface reaction torque estimated value Tsat_est to calculate the road surface reaction torque estimated value Tsat_est.

[0153] 22 is a block diagram showing an example of the configuration of the road surface reaction torque estimating unit 221. The road surface reaction torque estimating unit 221 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.

[0154] 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 it by a predetermined gear ratio and torque constant.

[0155] Actual steering angle θt_act is input to angular velocity calculation section 312. Angular velocity calculation section 312 converts actual steering angle θt_act into the angle of steering motor 41, performs differential calculation processing on this angle of steering motor 41, and further divides by the gear ratio to obtain pinion shaft converted motor angular velocity ω Ｍ Calculate.

[0156] The angular acceleration calculation unit 313 calculates the motor angular velocity ω Ｍ The angular acceleration calculation unit 313 calculates the motor angular velocity ω Ｍ is differentiated, and the motor angular acceleration converted to the pinion shaft is Ｍ Calculate.

[0157] The steering motor torque Tm and the motor angular velocity ω Ｍ , and motor angular acceleration α Ｍ Using the above, the road surface reaction torque estimated value Tsat_est is calculated based on the above equation (18) by the configuration shown in FIG.

[0158] The block 315 receives the motor angular velocity ω output from the angular velocity calculation unit 312. Ｍ The block 315 inputs the damper coefficient D Ｍ Multiply and output.

[0159] The block 317 receives the motor angular acceleration α output from the angular acceleration calculation unit 313. Ｍ is input. Block 317 multiplies the input data by the pinion shaft converted inertia J and outputs the result.

[0160] Subtraction section 318 subtracts the outputs of blocks 317 and 315 from the turning motor torque Tm output from conversion section 311 .

[0161] The above-mentioned configuration can realize the above-mentioned equation (18). That is, the road surface reaction force torque estimated value Tsat_est is calculated by the configuration of the road surface reaction force torque estimating unit 221 shown in FIG.

[0162] In the case 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 Furthermore, if the column angle can be detected directly, 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. Furthermore, a signal obtained by converting the turning angular velocity or the turning motor angular velocity into a pinion shaft, rather than the actual turning angle θt_act or the angle of the turning motor 41, is used as the motor angular velocity ω Ｍand omit the differentiation process for the angle of steering motor 41. Furthermore, road surface reaction force torque estimated value Tsat_est may be calculated by a method other than the above, or an estimated value equivalent to road surface reaction force torque estimated value Tsat_est may be used. Below, a method for calculating road surface reaction force torque estimated value Tsat_est that is different from the above method will be described.

[0163] In a method of calculating road surface reaction force torque estimated value Tsat_est that is different from the above-described method, first steering motor current command value Iref_a generated by steering angle control unit 700 is input to road surface reaction force torque estimating section 221. Also, a transfer function Gfil shown in the following equation (19) is set in road surface reaction force torque estimating section 221. Transfer function Gfil is stored, for example, in the ROM of an ECU that constitutes control device 50.

[0164] Gfil=N(s) / D(s)=(Ds+E) / (As ２ +Bs+C)...(19)

[0165] 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.

[0166] In the present 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 road surface reaction torque Tsat_act and the road surface reaction torque estimate value Tsat_est, the load on the ECU, etc.

[0167] For example, if the orders of the numerator and denominator are increased, the relationship between the first steering motor current command value Iref_a obtained through experiments described below and the actual road surface reaction torque Tsat_act can be made to match well with the transfer characteristics of the transfer function Gfil, making it possible to estimate a road surface reaction torque estimated value Tsat_est that is close to the actually measured value.

[0168] On the other hand, if the order of the numerator and denominator is reduced, the load on the ECU can be reduced.

[0169] Road reaction torque TＳＡＴ It is assumed that the relational expression shown in the following equation (20) holds between the first steering motor current command value Iref_a and the road surface reaction torque T ＳＡＴ is defined as the road surface reaction torque estimated value Tsat_est in this disclosure.

[0170] T ＳＡＴ =Gfil×Iref_a=Tsat_est...(20)

[0171] In other words, the transfer function Gfil calculates the road surface reaction force torque estimated value Tsat_est from the first steering motor current command value Iref_a by simulating the relationship between the first steering motor current command value Iref_a and the actual road surface reaction force torque Tsat_act obtained through experiments.

[0172] On the other hand, the actual road surface reaction torque Tsat_act acting on the steering mechanism can be calculated from the axial force applied to the tie rod. Figure 23 is a conceptual diagram for explaining a method of calculating the actual road surface reaction torque acting on the steering mechanism.

[0173] The actual road surface reaction torque Tsat_act can be calculated by the following equation (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 determined for each vehicle type.

[0174] Tsat_act=FL×L-FR×L...(21)

[0175] In the present disclosure, the actual road surface reaction torque Tsat_act is calculated using the above-mentioned formula (21) that uses the axial forces FL and FR measured in advance through experiments using an actual vehicle. The axial forces FL and FR can be measured, for example, by attaching force sensors to the tie rods 3 a and 3 b.

[0176] FIG. 24 is a conceptual diagram showing a configuration for executing a simulation for deriving the transfer function Gfil.

[0177] The first steering motor current command value Iref_a and axial forces FL and FR are input to the processing device shown in Figure 24. The processing device derives a transfer function Gfil such that road surface reaction torque estimated value Tsat_est shown in equation (20) above approximates actual road surface reaction torque Tsat_act calculated by equation (21) above. An example of the processing device shown in Figure 24 is one that includes a frequency characteristics analysis device (servo analyzer).

[0178] 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 equation (19). An example of the curve fitting method is the least squares approximation method. Note that the curve fitting method is not limited to the least squares approximation method.

[0179] Road surface reaction force torque estimating section 221 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 road surface reaction force torque estimated value Tsat_est shown in equation (20) above. In this way, road surface reaction force torque estimated value Tsat_est corresponding to the behavior of actual road surface reaction force torque Tsat_act when the vehicle is actually traveling is obtained.

[0180] The transfer function used when the road surface reaction torque estimation unit 221 calculates the road surface reaction torque estimated value Tsat_est is not limited to the form shown in the above (19). Specifically, for example, the present disclosure is not limited by the orders of the function N(s) or the function D(s).

[0181] Returning to FIG. 20 , the sign extraction unit 224 extracts the sign of the road reaction force torque estimated value Tsat_est obtained by the calculation method described above. Specifically, for example, the value of the road reaction force torque estimated value Tsat_est is divided by the absolute value of the road reaction force torque estimated value Tsat_est. As a result, the sign extraction unit 224 outputs "1" when the sign of the road reaction force torque estimated value Tsat_est is "+", and outputs "-1" when the sign of the road reaction force torque estimated value Tsat_est is "-". Specifically, the sign extraction unit 224 generates, for example, a sign function Sgn(Tsat_est) of the road reaction force torque estimated value Tsat_est.

[0182] 25 is a diagram showing an example of the characteristics of a road reaction force sensitive torque map. The road reaction force torque estimated value |Tsat_est| and vehicle speed Vs that have been subjected to absolute value processing in absolute value calculation section 223 are input to road reaction force sensitive torque map section 222. Road reaction force sensitive torque map section 222 generates a torque value Tref_d0 using the road reaction force sensitive torque map shown in FIG. 25 with vehicle speed Vs as a parameter.

[0183] As shown in FIG. 25, the torque value Tref_d0 has a torque-sensitive characteristic that increases and decreases according to the road surface reaction torque estimated value |Tsat_est|.

[0184] More specifically, the torque value Tref_d0 increases as the road surface reaction torque estimated value |Tsat_est| increases, and the rate of increase decreases as the road surface reaction torque estimated value |Tsat_est| increases.

[0185] Furthermore, the torque value Tref_d0 has a vehicle speed-sensitive characteristic that increases and decreases according to the vehicle speed Vs. More specifically, the torque value Tref_d0 increases as the vehicle speed Vs increases, as shown in Fig. 25 .

[0186] That is, the reaction force obtained by the torque value Tref_d0 derived from the road reaction force sensitive torque map shown in Fig. 25 becomes larger as the road reaction force torque estimated value |Tsat_est| becomes larger and as the vehicle speed (vehicle speed Vs) becomes faster. Note that although the road reaction force sensitive torque map shown in Fig. 25 has a vehicle speed sensitive characteristic, the present invention is not limited to this.

[0187] The road reaction force sensitive torque compensation value generating unit 220 multiplies the torque value Tref_d0, which is the output value of the road reaction force sensitive torque map unit 222, by the sign function Sgn(Tsat_est) of the road reaction force torque estimated value Tsat_est in the multiplier unit 225 to output the sign-converted torque value Tref_d (second torque value).

[0188] 26 is a diagram conceptually showing an example of the characteristics of the second torque value after sign conversion. As shown in Fig. 26, the torque value Tref_d (second torque value) output from the road reaction force sensitive torque compensation value generator 220 increases or decreases according to the road reaction force torque estimated value Tsat_est, which is an estimate of the reaction force (self-aligning torque) acting from the road surface. By applying the torque value Tref_d (second torque value), which increases or decreases according to the road reaction force torque estimated value Tsat_est, to the steering torque target value Th_ref, it is possible to obtain a steering reaction force according to the road reaction force torque estimated value Tsat_est.

[0189] The characteristics of the road reaction force sensitive torque map are not limited to the aspects shown in Fig. 25 or 26. Furthermore, for example, instead of the aspects of the maps shown in Fig. 25 or 26, the characteristics may be defined by a predetermined transfer function.

[0190] In the present disclosure, road surface reaction force sensitive torque compensation value generation section 220 calculates a road surface reaction force torque estimated value Tsat_est corresponding to first steering motor current command value Iref_a before adding second current compensation value Iref_b output from friction compensation section 770, thereby obtaining a road surface reaction force torque estimated value Tsat_est corresponding to the behavior of actual road surface reaction force torque Tsat_act when the vehicle is actually traveling, and can apply a steering reaction force corresponding to road surface reaction force torque estimated value Tsat_est.

[0191] In a mode in which steering angle control section 700 does not include friction compensation section 770, a mode can be adopted in which a road surface reaction torque corresponding to second steering motor current command value It_ref is estimated instead of first steering motor current command value Iref_a.

[0192] Here, the road reaction torque estimated value Tsat_est changes depending on the road surface condition as well as the vehicle state such as the vehicle speed, steering angle, etc. Therefore, depending on the vehicle state, the road surface condition may not be fully reflected, and it may not be possible to obtain a steering feel that corresponds to the road surface condition and the vehicle state.

[0193] In the present disclosure, a steering feel that reflects the road surface conditions and the vehicle state is obtained by multiplying the torque value Tref_a (first torque value) generated by steering reaction force torque value generator 210 and the torque value Tref_d (second torque value) generated by road surface reaction force sensitive torque compensation value generator 220 by an appropriate gain using the vehicle speed Vs, actual steering angle θh_act, actual turning angle θt_act, etc. as parameters (variables). Specifically, gain ratio generator 230 of steering torque target value generator 200 according to the first embodiment controls the ratio (hereinafter also simply referred to as the "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.

[0194] The configuration and operation of the first embodiment, which can provide a steering feel according to road conditions and vehicle status, will be described below. Fig. 27A is a diagram conceptually showing a first example of a gain ratio setting example when vehicle speed is used as a parameter. Fig. 27B is a diagram conceptually showing a second example of a gain ratio setting example when vehicle speed is used as a parameter. Fig. 27C is a diagram conceptually showing a third example of a gain ratio setting example when vehicle speed is used as a parameter.

[0195] 27A , 27B, and 27C , vehicle speed Vs is input to gain ratio generation unit 230. Gain ratio generation unit 230 generates a first gain Ga that increases or decreases according to vehicle speed Vs, and a second gain Gb whose sum with first gain Ga is 1. Multiplication unit 261 multiplies torque value Tref_a (first torque value) by first gain Ga. Multiplication unit 262 multiplies torque value Tref_d (second torque value) by second gain Gb.

[0196] The gain ratio generation 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.

[0197] 27A 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.

[0198] 27B 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 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 smaller 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.

[0199] 27C 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 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 equal to the minimum value Ga_min of the first gain Ga in the range equal to or greater than the second vehicle speed Vs_B.

[0200] The values ​​and magnitude relationships of 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 may be set appropriately depending on the dynamic performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0201] 27A, 27B, and 27C, a steering reaction force corresponding to the road reaction force torque estimated value Tsat_est can be applied to the steering wheel 1 at a ratio corresponding to the vehicle speed Vs. Specifically, in a region where the vehicle speed Vs is relatively small, the steering torque target value generating unit 200 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 vehicle speed Vs is relatively large, the steering torque target value generating unit 200 generates the steering torque target value Th_ref by multiplying the torque value Tref_d (second torque value) output from the road reaction force sensitive torque compensation value generating unit 220 by a relatively large second gain Gb. In the low-speed region where the vehicle speed Vs is relatively low, the reaction torque component due to the elastic deformation of the tires is the main component of the road reaction torque, and the reaction torque component due to the road surface condition accounts for a small proportion of the road reaction torque. In other words, if the output of the road reaction force sensitive torque compensation value generator 220 is relatively large in the low-speed region, a heavy steering torque will be applied even though it is difficult to obtain the road surface condition, and the steering feel of the driver will deteriorate. 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.

[0202] Note that 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 aspects shown in Figures 27A, 27B, and 27C. For example, within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, the first gain Ga by which the torque value Tref_a (first torque value) is multiplied may gradually decrease as the vehicle speed Vs increases, and accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied may gradually increase as the vehicle speed Vs increases. Furthermore, within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, the first gain Ga by which the torque value Tref_a (first torque value) is multiplied may gradually increase as the vehicle speed Vs decreases, and accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied may gradually decrease as the vehicle speed Vs decreases.

[0203] FIG. 28 is a diagram conceptually showing an example of gain ratio setting when the actual steering angle is used as a parameter.

[0204] 28 , 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. A multiplication unit 261 multiplies the torque value Tref_a (first torque value) by the first gain Ga. A multiplication unit 262 multiplies the torque value Tref_d (second torque value) by the second gain Gb.

[0205] The gain ratio generation 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 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 degrees. The second steering angle θh_B is set to, for example, 20 degrees. The present disclosure is not limited to the values ​​of the first steering angle θh_A and the second steering angle θh_B.

[0206] 28 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 greater 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 greater than the second steering angle θh_B.

[0207] In addition, the maximum value Ga_max of the first gain Ga in the range below the first steering angle θh_A may be smaller than the maximum value Gb_max of the second gain Gb in the range above the second steering angle θh_B, and the minimum value Gb_min of the second gain Gb in the range below the first steering angle θh_A may be smaller than the minimum value Ga_min of the first gain Ga in the range above the second steering angle θh_B.

[0208] In addition, the maximum value Ga_max of the first gain Ga in the range below the first steering angle θh_A may be equal to the maximum value Gb_max of the second gain Gb in the range above the second steering angle θh_B, and the minimum value Gb_min of the second gain Gb in the range below the first steering angle θh_A may be equal to the minimum value Ga_min of the first gain Ga in the range above the second steering angle θh_B.

[0209] The values ​​and magnitude relationships of 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 may be set appropriately depending on the dynamic performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0210] 28 , a steering reaction force corresponding to the road reaction 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 200 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 actual steering angle θh_act is relatively large, the steering torque target value generating unit 200 generates the steering torque target value Th_ref by multiplying the torque value Tref_d (second torque value) output from the road reaction force sensitive torque compensation value generating unit 220 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 steering angle θh_act.

[0211] Note that the example of setting the gain ratio when the actual steering angle θh_act is used as a parameter is just one example, and is not limited to the aspect shown in Fig. 28. 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 Ga by which the torque value Tref_a (first torque value) is multiplied may gradually decrease as the actual steering angle θh_act increases, and accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied may gradually increase as the actual steering angle θh_act increases. Further, for example, within the 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.

[0212] FIG. 29 is a diagram conceptually showing an example of gain ratio setting when the actual steering angle is used as a parameter.

[0213] 29 , 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 actual steering angle θt_act, and a second gain Gb whose sum with first gain Ga is 1. Multiplication section 261 multiplies torque value Tref_a (first torque value) by first gain Ga. Multiplication section 262 multiplies torque value Tref_d (second torque value) by second gain Gb.

[0214] Gain ratio generation unit 230 monotonically decreases the first gain Ga by which torque value Tref_a (first torque value) is multiplied within a range of not less than first turning angle θt_A and not more than second turning angle θt_B. Accordingly, second gain Gb by which torque value Tref_d (second torque value) is multiplied monotonically within a range of not less than first turning angle θt_A and not more than second turning angle θt_B. First turning angle θt_A is set to 3 degrees, for example. Second turning angle θt_B is set to 20 degrees, for example. The present disclosure is not limited to the values ​​of first turning angle θt_A and second turning angle θt_B.

[0215] 29 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 greater 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 greater than the second turning angle θt_B.

[0216] 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 greater 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 greater than the second steering angle θt_B.

[0217] 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 greater 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 greater than the second steering angle θt_B.

[0218] The values ​​and magnitude relationships of 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 may be set appropriately depending on the dynamic performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0219] 29 , a steering reaction force corresponding to road surface reaction force torque estimated value Tsat_est can be applied to steering wheel 1 at a ratio corresponding to actual turning angle θt_act. Specifically, in a region where actual turning angle θt_act is relatively small, steering torque target value generation section 200 generates steering torque target value Th_ref by multiplying torque value Tref_a (first torque value) output from steering reaction force torque value generation section 210 by a relatively large first gain Ga, and in a region where actual turning angle θt_act is relatively large, steering torque target value generation section 200 generates steering torque target value Th_ref by multiplying torque value Tref_d (second torque value) output from road surface reaction force sensitive torque compensation value generation section 220 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.

[0220] Note that the example of setting the gain ratio when the actual turning angle θt_act is used as a parameter is just one example, and is not limited to the aspect shown in Fig. 29. For example, within a range of not less than the first turning angle θt_A and not more than the second turning angle θt_B, an aspect may be adopted in which the first gain Ga by which the torque value Tref_a (first torque value) is multiplied gradually decreases as the actual turning angle θt_act increases, and accordingly the second gain Gb by which the torque value Tref_d (second torque value) is multiplied gradually increases as the actual turning angle θt_act increases. Further, for example, within the range of the first steering angle θt_A or more and the second steering angle θt_B or less, the first gain Ga by which the torque value Tref_a (first torque value) is multiplied may gradually increase as the actual steering angle θt_act decreases, and accordingly, the second gain Gb by which the torque value Tref_d (second torque value) is multiplied may gradually decrease as the actual steering angle θt_act decreases.

[0221] Fig. 30 is a block diagram showing an example of the configuration of a gain ratio generation unit when vehicle speed and actual steering angle are used as parameters. Fig. 31A is a diagram conceptually showing an example of a gain ratio setting example when vehicle speed is used as a parameter. Fig. 31B is a diagram conceptually showing an example of a gain ratio setting example when actual steering angle is used as a parameter.

[0222] 30 , the vehicle speed Vs and the actual steering angle θh_act are input to the gain ratio generation unit 230. In the example shown in FIG. 30 , the gain ratio generation unit 230 includes a first gain ratio generation unit 230 a, a second gain ratio generation unit 230 b, and a gain ratio calculation unit 231.

[0223] The first gain ratio generating unit 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.

[0224] 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 values ​​of the first vehicle speed Vs_A and the second vehicle speed Vs_B are not intended to limit the present disclosure.

[0225] 31A 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.

[0226] 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.

[0227] 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.

[0228] The values ​​and magnitude relationships of 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 may be set appropriately depending on the dynamic performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0229] 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.

[0230] The second gain ratio generator 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 degrees. The second steering angle θh_B is set to, for example, 20 degrees. The present disclosure is not limited to the values ​​of the first steering angle θh_A and the second steering angle θh_B.

[0231] 31B 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 greater 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 greater than the second steering angle θh_B.

[0232] In addition, the maximum value Ga2_max of the first gain Ga2 in the range below the first steering angle θh_A may be smaller than the maximum value Gb2_max of the second gain Gb2 in the range above the second steering angle θh_B, and the minimum value Gb2_min of the second gain Gb2 in the range below the first steering angle θh_A may be smaller than the minimum value Ga2_min of the first gain Ga2 in the range above the second steering angle θh_B.

[0233] 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 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 equal to the minimum value Ga2_min of the first gain Ga2 in the range equal to or greater than the second steering angle θh_B.

[0234] The gain ratio calculation unit 231 receives the first gain Ga1 and second gain Gb1 output from the first gain ratio generation unit 230 a, and the first gain Ga2 and second gain Gb2 output from the second gain ratio generation unit 230 b. The gain ratio calculation unit 231 calculates the first gain Ga using the following equation (22), and calculates the second gain Gb using the following equation (23).

[0235] Ga=(Ga1×Ga2) / {(Ga1×Ga2)+(Gb1×Gb2)} (22)

[0236] Gb=(Gb1×Gb2) / {(Ga1×Ga2)+(Gb1×Gb2)} (23)

[0237] 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.

[0238] 30 , a steering reaction force corresponding to road surface reaction force 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 a region where the vehicle speed Vs or the actual steering angle θh_act is relatively small, the steering torque target value generating unit 200 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 vehicle speed Vs or the actual steering angle θh_act is relatively large, the steering torque target value generating unit 200 generates the steering torque target value Th_ref by multiplying the torque value Tref_d (second torque value) output from the road surface reaction force sensitive torque compensation value generating unit 220 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 steering angle θh_act.

[0239] Note that 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. 31A described above. For example, the first gain Ga1 may gradually decrease as the vehicle speed Vs increases within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, and the second gain Gb1 may accordingly gradually increase as the vehicle speed Vs increases. Furthermore, for example, the first gain Ga1 may gradually increase as the vehicle speed Vs decreases within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, and the second gain Gb1 may accordingly gradually decrease as the vehicle speed Vs decreases.

[0240] Furthermore, the example of setting the gain ratios using the actual steering angle θh_act as a parameter is merely an example, and is not limited to the example shown in FIG. 31B. 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 gradually decrease as the actual steering angle θh_act increases, and the second gain Gb2 may accordingly increase as the actual steering angle θh_act increases. Furthermore, 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 gradually increase as the actual steering angle θh_act decreases, and the second gain Gb2 may accordingly decrease as the actual steering angle θh_act decreases.

[0241] Fig. 32 is a block diagram showing an example of the configuration of a gain ratio generation unit when vehicle speed and actual steering angle are used as parameters. Figs. 33A and 33B are diagrams conceptually showing an example of a gain ratio setting example using vehicle speed as a parameter. Fig. 33B is a diagram conceptually showing an example of a gain ratio setting example using actual steering angle as a parameter.

[0242] In the exemplary configuration shown in Fig. 32 , vehicle speed Vs and actual steering angle θt_act are input to gain ratio generation unit 230. Furthermore, as shown in Fig. 32 , gain ratio generation unit 230 includes a first gain ratio generation unit 230a, a second gain ratio generation unit 230c, and a gain ratio calculation unit 231.

[0243] The first gain ratio generating unit 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.

[0244] 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 values ​​of the first vehicle speed Vs_A and the second vehicle speed Vs_B are not intended to limit the present disclosure.

[0245] 33A 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.

[0246] 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.

[0247] 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.

[0248] The values ​​and magnitude relationships of 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 may be set appropriately depending on the dynamic performance and vehicle specifications of the vehicle in which the control device 50 of the present disclosure is installed.

[0249] The second gain ratio generating section 230c generates a first gain Ga2 that increases or decreases according to the actual turning angle θt_act, and a second gain Gb2 whose sum with the first gain Ga2 is one.

[0250] Second gain ratio generation unit 230c monotonically decreases first gain Ga2 within a range of not less than first turning angle θt_A and not more than second turning angle θt_B. Accordingly, second gain Gb2 monotonically increases within a range of not less than first turning angle θt_A and not more than second turning angle θt_B. First turning angle θt_A is set to 3 degrees, for example. Second turning angle θt_B is set to 20 degrees, for example. The present disclosure is not limited to the values ​​of first turning angle θt_A and second turning angle θt_B.

[0251] 33B 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 greater 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 greater than the second turning angle θt_B.

[0252] 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.

[0253] 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 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 equal to the minimum value Ga2_min of the first gain Ga2 in the range equal to or greater than the second steering angle θt_B.

[0254] 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.

[0255] 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.

[0256] 32 , a steering reaction force corresponding to road surface reaction force torque estimated value Tsat_est can be applied to steering wheel 1 at a ratio corresponding to both vehicle speed Vs and actual turning angle θt_act. Specifically, in a region where vehicle speed Vs or actual turning angle θt_act is relatively small, steering torque target value generation section 200 generates steering torque target value Th_ref by multiplying torque value Tref_a (first torque value) output from steering reaction force torque value generation section 210 by a relatively large first gain Ga, and in a region where vehicle speed Vs or actual turning angle θt_act is relatively large, steering torque target value generation section 200 generates steering torque target value Th_ref by multiplying torque value Tref_d (second torque value) output from road surface reaction force sensitive torque compensation value generation section 220 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 steering angle θt_act.

[0257] Note that 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. 33A described above. For example, the first gain Ga1 may gradually decrease as the vehicle speed Vs increases within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, and the second gain Gb1 may accordingly gradually increase as the vehicle speed Vs increases. Furthermore, for example, the first gain Ga1 may gradually increase as the vehicle speed Vs decreases within a range from the first vehicle speed Vs_A to the second vehicle speed Vs_B, and the second gain Gb1 may accordingly gradually decrease as the vehicle speed Vs decreases.

[0258] Furthermore, the example of setting the gain ratio using the actual steering angle θt_act as a parameter is merely an example, and is not limited to the aspect shown in Figure 33B described above. For example, within a range of not less than the first steering angle θt_A and not more than the second steering angle θt_B, the first gain Ga2 may gradually decrease as the actual steering angle θt_act increases, and accordingly, the second gain Gb2 may gradually increase as the actual steering angle θt_act increases. Furthermore, within a range of not less than the first steering angle θt_A and not more than the second steering angle θt_B, the first gain Ga2 may gradually increase as the actual steering angle θt_act decreases, and accordingly, the second gain Gb2 may gradually decrease as the actual steering angle θt_act decreases.

[0259] In the present disclosure, the ratio of the first gain Ga to the second gain Gb is not limited to a ratio that changes linearly with changes in each parameter. Specifically, for example, a gain ratio corresponding to each parameter value may be mapped and the gain ratio according to the parameter value may be applied. Fig. 34 is a 3D map conceptually illustrating an example of a gain ratio generation method.

[0260] The gain ratio generation 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 Figure 34, and calculate the first gain Ga using the following equation (24).

[0261] Ga=1-Gb...(24)

[0262] Alternatively, the gain ratio generation unit 230 may generate the first gain Ga using a gain ratio map with the vehicle speed Vs and the actual steering angle θh_act as parameters, and calculate the second gain Gb using the following equation (25).

[0263] Gb=1-Ga...(25)

[0264] Furthermore, the first gain Ga and the second gain Gb may be generated using a gain ratio map that uses the vehicle speed Vs and the actual steering angle θh_act as parameters, without being limited to a gain ratio map that uses the vehicle speed Vs and the actual steering angle θt_act as parameters.

[0265] 35 is a block diagram showing an example of the configuration of a steering wheel return compensation unit according to embodiment 1. The steering wheel return compensation unit 280 according to embodiment 1 includes, as main components, an actual steering torque sensitive torque map unit 281 and a steering angular velocity sensitive gain map unit 282.

[0266] 36 is a diagram showing an example of the characteristics of an actual steering torque responsive torque map. The actual steering torque |Th_act| that has been subjected to absolute value processing in an absolute value calculation section 284 is input to the actual steering torque responsive torque map section 281. The actual steering torque responsive torque map section 281 generates a torque value Tref_e0 corresponding to the actual steering torque |Th_act| using the actual steering torque responsive torque map shown in FIG.

[0267] The torque value Tref_e0 has an actual steering torque sensitive characteristic that increases or decreases according to the actual steering torque |Th_act|. More specifically, the torque value Tref_e0 decreases as the actual steering torque |Th_act| increases, as shown in Fig. 36. In other words, the reaction force obtained by the torque value Tref_e0 derived from the actual steering torque sensitive torque map shown in Fig. 36 increases as the actual steering torque Th_act decreases.

[0268] Fig. 37 is a diagram showing an example of the characteristics of a steering angular velocity sensitive gain map. A steering angular velocity |ωh_act| obtained by differentiating the actual steering angle θh_act in a differentiating section 285 and performing absolute value processing in an absolute value calculation section 286 is input to the steering angular velocity sensitive gain map section 282. The steering angular velocity sensitive gain map section 282 generates a third gain Gc corresponding to the steering angular velocity |ωh_act| using the steering angular velocity sensitive gain map shown in Fig. 37.

[0269] The third gain Gc has a steering angular velocity sensitivity characteristic that increases or decreases according to the steering angular velocity |ωh_act|. More specifically, as shown in FIG. 37, the third gain Gc is ０ In the following region, the steering angle speed |ωh_act| increases rapidly, and the steering angle speed ω ０ When the steering angle speed |ωh_act| exceeds ωh_act, the steering angle speed |ωh_act| gradually decreases as the steering angle speed |ωh_act| increases.

[0270] The third gain Gc generated by the steering angular velocity sensitive gain map unit 282 is multiplied by the sign Sgn(ωh) of the steering angular velocity ωh_act by a multiplication unit 288, and then multiplied by the torque value Tref_e0 by a multiplication unit 289. As a result, a torque value Tref_e1 corresponding to an increase or decrease in the steering angular velocity ωh_act is obtained.

[0271] The output limiting unit 290 performs an output limiting process on the torque value Tref_e1. Upper and lower limit values ​​for the torque value Tref_e1 are set in advance in the output limiting unit 290. The output limiting unit 290 limits the upper and lower limit values ​​of the torque value Tref_e1 and outputs the limit value to the filter unit 291.

[0272] The filter unit 291 performs filtering on the torque value after the output limiting process. Specifically, the filter unit 291 is a low-pass filter, and filtering by the low-pass filter reduces high-frequency noise components contained in the torque value Tref_e1.

[0273] The torque value after filtering is subjected to sign inversion processing by sign inversion unit 292 and output as torque compensation value Tref_e (third torque value). As a result, torque compensation value Tref_e (third torque value) is output as a torque value that applies a steering force in the opposite direction to the steering direction.

[0274] The steering torque target value generation unit 200 adds (addition units 271, 272, 273, 274) the torque value Ga×Tref_a obtained by multiplying the torque value Tref_a (first torque value) output from the steering reaction torque value generation unit 210 by the first gain Ga to obtain a torque value Ga×Tref_a, (multiplication unit 261) the torque value Tref_d (second torque value) output from the road surface reaction force sensitive torque compensation value generation unit 220 by the second gain Gb to obtain a torque value Gb×Tref_d, (multiplication unit 262) the torque value Tref_b output from the damping torque value generation unit 240, the torque compensation value Tref_c output from the hysteresis compensation unit 250, and the torque compensation value Tref_e (third torque value) output from the steering wheel return compensation unit 280 to obtain a steering torque target value Th_ref.

[0275] Fig. 38 is a diagram conceptually illustrating a specific example of the effect of the steering wheel return compensation unit according to embodiment 1. In Fig. 38, the vertical axis represents the steering angle θh, and the horizontal axis represents time t.

[0276] 38 shows an example in which, at time t0, the driver releases the steering wheel, which has been held at a steering angle θh≈α1 (deg), while traveling at low speed on a low μ road. The solid line in FIG. 38 shows the trajectory of the steering angle θh in the configuration of embodiment 1 that has the steering wheel return compensation unit 280, and the dashed line shows the trajectory of the steering angle θh in the configuration that does not have the steering wheel return compensation unit 280.

[0277] When traveling on a low μ road, the torque value Tref_d (second torque value) generated by the road reaction force sensitive torque compensation value generating unit 220 becomes small. Therefore, in a configuration that does not have the steering return compensation unit 280, the steering reaction force applied while traveling on a low μ road becomes small, which may result in an unstable steering feel.

[0278] In particular, when the first gain Ga and the second gain Gb are generated using the vehicle speed Vs as a parameter (e.g., FIGS. 27A, 27B, and 27C), the second gain Gb by which the torque value Tref_d (second torque value) is multiplied becomes smaller during low-speed driving. Specifically, for example, when the driver releases the steering wheel from a turned state while driving at low speed on a low-μ road, it may take a long time for the steering wheel position to return to the center position (steering angle θh≒0 (deg)), or the steering wheel position may not return completely to the center position, resulting in a residual steering angle. The example shown by the dashed line in FIG. 38 illustrates an example in which the steering angle θh≒0 (deg) does not return completely after the driver releases his / her hands from the steering wheel at time t0, resulting in a residual steering angle of steering angle θh≒α2 (deg) after time t1, which is σ (sec) after time t0.

[0279] The steering torque target value generating unit 200 according to the first embodiment can apply a stable steering reaction force even when the vehicle is traveling at low speed on a low μ road by including the steering wheel return compensation unit 280. Specifically, the example shown by the solid line in Fig. 38 shows an example in which an appropriate steering reaction force is applied by the torque compensation value Tref_e (third torque value) generated by the steering wheel return compensation unit 280, and after the driver releases his / her hands from the steering wheel at time t0, the steering wheel position returns to the steering angle θh ≈ 0 (deg) after time t1.

[0280] 39 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to embodiment 2. In embodiment 2, components and operations different from those of embodiment 1 will be described in detail, and descriptions of components and operations similar to those of embodiment 1 may be omitted.

[0281] 39 is configured to apply a gain corresponding to the gain ratio between the first gain Ga and the second gain Gb generated by the gain ratio generation unit 230 to the torque compensation value Tref_e (third torque value) generated by the steering wheel return compensation unit 280a and the torque value Tref_b (fourth torque value) generated by the damping torque value generation unit 240a. The configurations and operations of the steering wheel return compensation unit 280a and the damping torque value generation unit 240a according to the second embodiment will be described below.

[0282] Fig. 40 is a block diagram showing an example of the configuration of a steering wheel return compensation unit according to embodiment 2. Fig. 41 is a block diagram showing an example of the configuration of a damping torque value generation unit according to embodiment 2. A steering wheel return compensation unit 280a according to embodiment 2 includes a gain ratio sensitive gain map unit 283 in addition to the configuration of embodiment 1 shown in Fig. 35. A damping torque value generation unit 240a according to embodiment 2 includes a gain ratio sensitive gain map unit 244 in addition to the configuration of embodiment 1 shown in Fig. 15.

[0283] 42A and 42B are diagrams showing first example characteristics of a gain ratio sensitive gain map of a steering wheel return compensation unit and a damping torque value generation unit, respectively;

[0284] The first gain Ga generated by the gain ratio generating unit 230 is input to the gain ratio sensitive gain map unit 283 of the steering wheel return compensation unit 280a. The gain ratio sensitive gain map unit 283 generates the fourth gain Gd according to the first gain Ga using, for example, the gain ratio sensitive gain map shown in Fig. 42A.

[0285] 42A, the fourth gain Gd has a first-gain sensitive characteristic that increases or decreases according to the first gain Ga. More specifically, the fourth gain Gd increases as the first gain Ga increases.

[0286] Similarly to the gain ratio sensitive gain map section 283 of the steering wheel return compensation section 280a, the first gain Ga generated by the gain ratio generation section 230 is also input to the gain ratio sensitive gain map section 244 of the damping torque value generation section 240a. The gain ratio sensitive gain map section 244 generates the fifth gain Ge corresponding to the first gain Ga using, for example, the gain ratio sensitive gain map shown in FIG. 42B .

[0287] 42B, the fifth gain Ge has a first-gain sensitive characteristic that increases or decreases according to the first gain Ga. More specifically, the fifth gain Ge decreases as the first gain Ga increases.

[0288] The characteristics of the gain ratio sensitive gain map of the steering wheel return compensation section 280a and the gain ratio sensitive gain map of the damping torque value generation section 240a are not limited to the first characteristic example shown in FIGS. 42A and 42B.

[0289] 43A and 43B are diagrams showing second example characteristics of the gain ratio sensitive gain map of the steering wheel return compensation unit and the damping torque value generation unit, respectively.

[0290] In the second characteristic example of the gain ratio sensitive gain map of the steering wheel return compensation unit shown in FIG. 43A, the fourth gain Gd increases as the first gain Ga increases.

[0291] In the second characteristic example of the gain ratio sensitive gain map of the damping torque value generating unit shown in FIG. 43B, the fifth gain Ge decreases as the first gain Ga increases.

[0292] 44A and 44B are diagrams showing third example characteristics of the gain ratio sensitive gain map of the steering wheel return compensation unit and the damping torque value generation unit, respectively.

[0293] In the third characteristic example of the gain ratio sensitive gain map of the steering return compensation unit shown in FIG. 44A, the fourth gain Gd decreases as the first gain Ga increases.

[0294] In the third characteristic example of the gain ratio sensitive gain map of the damping torque value generating unit shown in FIG. 44B, the fifth gain Ge increases as the first gain Ga increases.

[0295] 45A and 45B are diagrams showing fourth example characteristics of the gain ratio sensitive gain map of the steering wheel return compensation unit and the damping torque value generation unit, respectively.

[0296] In the fourth characteristic example of the gain ratio sensitive gain map of the steering wheel return compensation unit shown in FIG. 45A, the fourth gain Gd decreases as the first gain Ga increases.

[0297] In the fourth characteristic example of the gain ratio sensitive gain map of the damping torque value generating unit shown in FIG. 45B, the fifth gain Ge increases as the first gain Ga increases.

[0298] The steering wheel return compensation unit 280a obtains a torque value Tref_e2 by multiplying the torque value Tref_e1, which corresponds to an increase or decrease in the steering angular velocity ωh_act, by a fifth gain Ge using a multiplication unit 293. Then, an output limiting unit 290 limits the upper and lower limits of the torque value Tref_e2, a filter unit 291 performs filtering on the torque value after the output limiting process, and a sign inversion unit 292 performs sign inversion on the torque value after the filtering process, and outputs the result as a torque compensation value Tref_e (third torque value).

[0299] The damping torque value generating section 240a multiplies the value obtained by multiplying the steering angular velocity ωh by the damper gain DG by a fifth gain Ge using a multiplier 245, and outputs the result as a torque value Tref_b (fourth torque value).

[0300] The steering torque target value generation unit 200a adds (addition units 271, 272, 273, 274) the torque value Ga×Tref_a obtained by multiplying (multiplication unit 261) the torque value Tref_a (first torque value) output from the steering reaction torque value generation unit 210 by the first gain Ga, (multiplication unit 262) Gb×Tref_d obtained by multiplying (multiplication unit 262) the torque value Tref_d (second torque value) output from the road surface reaction force sensitive torque compensation value generation unit 220 by the second gain Gb, the torque value Tref_b (fourth torque value) output from the damping torque value generation unit 240a, the torque compensation value Tref_c output from the hysteresis compensation unit 250, and the torque compensation value Tref_e (third torque value) output from the steering wheel return compensation unit 280a, and outputs the result as the steering torque target value Th_ref.

[0301] As described above, in the second embodiment, the gain ratio between the torque compensation value Tref_e (third torque value) generated by the steering wheel return compensation unit 280a and the torque value Tref_b (fourth torque value) generated by the damping torque value generation unit 240a is controlled in accordance with the gain ratio between the first gain Ga and the second gain Gb generated by the gain ratio generation unit 230. This makes it possible to optimize the steering feel by, for example, setting the ratio between the fourth gain Gd that determines the gain distribution of the torque compensation value Tref_e (third torque value) and the fifth gain Ge that determines the gain distribution of the torque value Tref_b (fourth torque value) in accordance with vehicle conditions such as vehicle weight and driving specifications, or a driving mode such as an urban driving mode or a highway driving mode.

[0302] Fig. 46 is a diagram conceptually illustrating a specific example of the effect of the steering wheel return compensation unit according to embodiment 2. In Fig. 46, the vertical axis represents the steering angle θh, and the horizontal axis represents time t.

[0303] 46 shows an example in which, at time t0, the driver releases the steering wheel, which has been held at a steering angle θh≈α1 (deg), while traveling at low speed on a low μ road. The solid line in FIG. 46 shows the trajectory of the steering angle θh in the configuration of embodiment 2 that has the steering wheel return compensation unit 280a, and the dashed line shows the trajectory of the steering angle θh in the configuration that does not have the steering wheel return compensation unit 280a.

[0304] In the configuration of the steering torque target value generating unit 200a according to the second embodiment, as in the first embodiment, by including the steering wheel return compensation unit 280a, it is possible to apply a stable steering reaction force even when the vehicle is traveling at low speed on a low μ road. Specifically, the example shown by the solid line in Fig. 46 shows an example in which an appropriate steering reaction force is applied by the torque compensation value Tref_e (third torque value) generated by the steering wheel return compensation unit 280a, and after the driver releases his / her hands from the steering wheel at time t0, the steering wheel position returns to the steering angle θh ≈ 0 (deg) after time t1.

[0305] In addition to the above, the configuration of the steering torque target value generating unit 200a according to the second embodiment is configured to apply a gain corresponding to the gain ratio between the first gain Ga and the second gain Gb generated by the gain ratio generating unit 230 to the torque value Tref_b (fourth torque value) generated by the damping torque value generating unit 240a and the torque compensation value Tref_e (third torque value) generated by the steering wheel return compensation unit 280a. In the configuration of the steering torque target value generating unit 200a according to the second embodiment, by appropriately setting the characteristics of the gain ratio sensitive gain map of the damping torque value generating unit 240a and the characteristics of the gain ratio sensitive gain map of the steering wheel return compensation unit 280a according to, for example, the vehicle conditions, it is possible to obtain a steering feel that more appropriately reflects the road surface conditions and the vehicle state.

[0306] It should be noted that the drawings used in the above-described embodiments are conceptual diagrams for qualitatively explaining the present disclosure, and are not intended to be limiting. Furthermore, while the above-described embodiment is an example of a preferred embodiment of the present disclosure, the present disclosure is not limited thereto, and various modifications can be made within the scope of the gist of the present disclosure.

[0307] DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Column shaft 3a, 3b Tie rods 5L, 5R Steered wheels 6a, 6b Arm 10 Vehicle speed sensor 11 Ignition key 12 Battery 30 Reaction device 31 Reaction motor 32 Speed ​​reduction mechanism 33 Steering angle sensor 34 Torque sensor 35 Stopper (rotation limiting mechanism) 40 Steering device 41 Steering motor 42 Speed ​​reduction mechanism 43 Angle sensor 44 Pinion rack mechanism 50 Control device 60 Reaction control system 70 Steering control system 200, 200a Steering torque target value generation unit 210 Steering reaction torque value generation unit 211 Steering reaction torque map unit 220 Road surface reaction force sensitive torque compensation value generation unit 221 Road surface reaction force torque estimation unit 222 Road surface reaction force sensitive torque map unit 230 Gain ratio generation section 230a First gain ratio generation section 230b, 230c Second gain ratio generation section 231 Gain ratio calculation section 240, 240a Damping torque value generation section 241 Damping gain map section 244 Gain ratio sensitive gain map section 250 Hysteresis compensation section 251 Hysteresis compensation value calculation section 280, 280a Steering wheel return compensation section 281 Actual steering torque sensitive torque map section 282 Steering angular velocity sensitive gain map section 283 Gain ratio sensitive gain map section 400 Steering torque control section 500 Current control section 600 Turning angle target value generation section 700 Turning angle control section 710 Feedforward compensation section 720 Addition section 730 PID control section 740 Stabilization compensation section 750 Addition section 760 Output limitation section 770, 770a Friction compensation unit 771, 771a Current compensation value calculation unit 772 Differentiation unit 773 Current sensitive gain generation unit 774 Previous value holding unit 775 Absolute value calculation unit 776 Multiplication unit 800 Current control unit

Claims

1. A control device for a vehicle steering system including a steering angle sensor that detects the steering angle of a steering wheel, a torque sensor that detects steering torque, a reaction force device that drives a reaction force motor that applies a steering reaction force to the steering wheel in accordance with the steering angle and the steering torque, and a steering device that drives a steering motor that steers the turnable wheels in accordance with the steering angle of the steering wheel, comprising: a steering torque target value generation unit that generates a steering torque target value that is a target value of the steering torque, a steering angle target value generation unit that generates a steering angle target value that is a target value of the turning angle of the turnable wheels, based on the steering angle, and a turning angle control unit that generates a first turning motor current command value that is a target value of the current to be supplied to the turning motor, based on the turning angle target value, wherein the steering torque target value generation unit comprises: a steering reaction force torque value generation unit that generates a first torque value that increases or decreases in accordance with at least the steering angle, a road surface reaction force sensitive torque compensation value generation unit that generates a second torque value that increases or decreases in accordance with a road surface reaction torque estimated value estimated based on at least the first steering motor current command value; a gain ratio generation unit that generates at least a first gain that increases or decreases in accordance with a vehicle speed of a vehicle, and a second gain whose sum with the first gain is 1; and a steering wheel return compensation unit that generates at least a third torque value that decreases as the steering torque increases, 2. The control device for a vehicle steering system according to claim 1, wherein the gain ratio generating unit decreases the first gain as the vehicle speed increases.

3. The control device for a vehicle steering system according to claim 2, wherein the steering wheel return compensation unit generates the third torque value by multiplying a torque value that decreases as the steering torque increases by a third gain that increases or decreases according to a steering angular speed.

4. The control device for a vehicle steering system according to claim 3, wherein the steering wheel return compensation unit increases the third gain as the steering angular velocity increases in a region where the steering angular velocity is equal to or less than a predetermined value, and decreases the third gain as the steering angular velocity increases when the steering angular velocity exceeds the predetermined value.

5. The control device for a vehicle steering system as described in claim 4, wherein the steering wheel return compensation unit generates the third torque value by multiplying a torque value that decreases as the steering torque increases by a fourth gain corresponding to a ratio between the first gain and the second gain, and the steering torque target value generation unit further includes a damping torque value generation unit that generates a fourth torque value by multiplying a value obtained by multiplying a steering angular velocity by a damping gain that increases or decreases according to vehicle speed by a fifth gain corresponding to the ratio between the first gain and the second gain, and generates the steering torque target value by adding together the value obtained by multiplying the first torque value by the first gain, the value obtained by multiplying the second torque value by the second gain, the third torque value, and the fourth torque value.

6. The control device for a vehicle steering system according to claim 5, wherein the fourth gain increases as the first gain increases, and the fifth gain decreases as the first gain increases.

7. The control device for a vehicle steering system according to claim 5, wherein the fourth gain decreases as the first gain increases, and the fifth gain increases as the first gain increases.

8. A control device for a vehicle steering system as described in any one of claims 1 to 7, wherein the steering angle control unit includes a friction compensation unit that calculates different steering motor current compensation values ​​depending on whether the steered wheels are steered to the right or 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.

9. The control device for a vehicle steering system according to claim 8, wherein the steering motor current compensation value has a hysteresis characteristic according to a change in the steering angle target value.

10. A control device for a vehicle steering system as described in claim 8, wherein 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.

11. The control device for a vehicle steering system according to claim 8, wherein the friction compensation section increases or decreases the steering motor current compensation value in response to the second steering motor current command value.

12. The control device for a vehicle steering system according to claim 11, wherein the turning motor current compensation value monotonically increases as the second turning motor current command value increases.

13. A control device for a vehicle steering system as described in claim 12, comprising: 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, wherein the friction compensation unit calculates a second current compensation value by multiplying the first current compensation value by the gain.

14. A control device for a vehicle steering system as described in claim 12, wherein the friction compensation unit holds data relating to the second turning motor current command value and 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.

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