Vehicle steering system control device

Abstract

To provide a control device for a vehicle steering system which has a zero steering reaction force or can suppress generation of a steering reaction force to instantaneously turn a handle more, when instantaneous returning occurs from turning the handle.SOLUTION: A control device for a vehicle steering system includes: a damping torque calculation part 240 for performing processing for each predetermined period, and calculating a first torque value which becomes larger with higher steering angle speed of a handle; and an output value selection part 251 for selecting any one of the first torque value and a second torque value which is generated in the previous processing and whose the first torque value is held, depending on whether at least the handle is returned.SELECTED DRAWING: Figure 8

Description

[Technical field]

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

[0002] One of the steering systems for vehicles is the Steer By Wire (SBW) system, in which a steering mechanism (FFA: Force Feedback Actuator) having a steering wheel operated by the driver and a steering mechanism (RWA: Road Wheel Actuator) that steers the steered wheels are mechanically separated. In the SBW system, the steering mechanism and the steering mechanism are electrically connected via a control device (ECU: Electronic Control Unit), and the operation of the steering wheel is transmitted to the steering mechanism by an electric signal to steer the steered wheels, and the steering mechanism generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates the steering reaction force by a reaction actuator equipped with a reaction motor, and the steering mechanism steers the steered wheels by a steering actuator equipped with a steering motor. The reaction actuator and the steering wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction actuator is transmitted to the driver via the column shaft and the steering wheel.

[0003] In SBW systems where the steering mechanism and the turning mechanism are mechanically separated, in order to avoid problems (e.g., cable breakage) caused by cables for electrical equipment such as an airbag or horn mounted on the steering wheel, a steering end point that is the limit of steering is provided in the steering mechanism, and an upper limit is set for the steering angle of the steering wheel. Patent Document 1 listed below discloses a technology that increases the steering reaction force when the steering angle is equal to or greater than a steering angle threshold, thereby restricting the steering wheel operation by the driver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-024624 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a configuration provided with a stopper (rotation limiting mechanism) that physically sets the steering end point that is the limit of possible steering, it is conceivable to suppress the occurrence of a collision at the steering end point when the driver turns the steering wheel further near the steering end point by applying a steering reaction force that increases with an increase in the steering angular speed. In such a configuration, if a steering reaction force exceeding the torque applied to the steering wheel by the driver when the driver steers the steering wheel is applied, there is a possibility that the steering wheel will momentarily transition from further turning to returning to its original position. If such a momentary return occurs from further turning to a position where the steering reaction force is zero, or a steering reaction force that momentarily tries to turn the wheel further is generated, there is a possibility that a collision will occur at the steering end point, which may cause discomfort or strangeness to the driver.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control device for a vehicle steering system that can suppress the steering reaction force from being zero or the generation of a steering reaction force that attempts to momentarily increase the steering force when the steering wheel is turned further and then instantly turned back. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a control device for a vehicle steering system according to one embodiment of the present invention is a control device for a vehicle steering system having a rotation limiting mechanism provided at the steering end of a steering wheel, a reaction force device that drives a reaction force motor that applies a steering reaction force to the steering wheel, and a steering device that drives a steering motor in accordance with the steering angle of the steering wheel, and is provided with a steering torque target value generation unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force, and the steering torque target value generation unit is provided with a torque calculation unit that performs processing at predetermined intervals and generates a first torque value that becomes larger as the steering angular speed of the steering wheel is faster, and an output value selection unit that selects either the first torque value or a second torque value that is retained as the first torque value generated in the previous processing, depending at least on whether the steering wheel has been turned back.

[0008] According to the above configuration, when the steering wheel is turned further and then instantly turned back, the second torque value generated by the torque calculation unit in the previous processing and held in the output value selection unit is output, thereby preventing the steering reaction force from becoming zero or preventing the steering reaction force from momentarily trying to turn the steering wheel further.

[0009] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the output value selection unit selects the second torque value when the multiplication value of the steering angle and the steering angular velocity changes from a positive value to a negative value and the amount of fluctuation of the steering angle is less than or equal to a predetermined fluctuation amount threshold.

[0010] According to the above configuration, it is possible to determine whether the steering wheel is being turned further or returned using the steering angle and the steering angle speed. Also, by selecting the second torque value when the steering wheel is turned further and then returned instantaneously and the amount of change in the steering angle is equal to or less than the threshold amount of change, it is possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn further.

[0011] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the output value selection unit selects the second torque value when the multiplied value of the steering angle and the steering angular velocity changes from a positive value to a negative value and the time during which the multiplied value is negative is equal to or less than a predetermined time threshold.

[0012] According to the above configuration, it is possible to determine whether the steering wheel is being turned further or returned using the steering angle and the steering angle speed. Also, when the steering wheel is turned further and then returned instantaneously, and the time during which the product of the steering angle and the steering angle speed is a negative value is equal to or less than the time threshold value, it is possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn further by selecting the second torque value.

[0013] As a desirable aspect of the control device for a vehicle steering system, the first torque value is preferably a value that increases with an increase in energy proportional to the square of the steering angular velocity.

[0014] According to the above configuration, the first torque value increases as the steering angular speed increases.

[0015] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the torque calculation unit generates a third torque value whose value increases as the steering angle increases, and multiplies the third torque value by the torque value selected by the output value selection unit.

[0016] According to the above configuration, it is possible to obtain a torque value that has both a characteristic of increasing with an increase in steering angular velocity and a characteristic of increasing with an increase in steering angle. Effect of the Invention

[0017] According to the present invention, a control device for a vehicle steering system can be provided that can suppress the steering reaction force from being zero or the generation of a steering reaction force that attempts to momentarily increase the steering force when the steering wheel is turned further and then turned back instantaneously. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a hardware configuration of the ECU. [Diagram 3] FIG. 3 is a diagram illustrating an example of a control block configuration of the control device according to the embodiment. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit. [Figure 5A] FIG. 5A is a diagram showing an example of the characteristics of the base map. [Figure 5B] FIG. 5B is a graph showing an example of the characteristics of the torque value Tref_basic. [Figure 6A] FIG. 6A is a diagram showing an example of a characteristic of a damper gain map. [Figure 6B] FIG. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. [Figure 7] FIG. 7 is a region diagram for explaining the steering direction in the present disclosure. [Figure 8] FIG. 8 is a block diagram showing an example of the configuration of the damping torque calculation unit. [Figure 9] FIG. 9 is a diagram showing an example of the characteristics of an angle sensitive gain map. [Figure 10] FIG. 10 is a diagram showing an example of the characteristics of the angular velocity sensitive gain map. [Figure 11] FIG. 11 is a diagram showing an example of the characteristics of the torque value calculated in the damping torque calculation section. [Figure 12] FIG. 12 is a block diagram illustrating an example of the configuration of the steering direction determination unit according to the first embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a control block configuration for explaining a processing mode of a calculation processing unit in the steering direction determination unit according to the first embodiment. [Figure 14] FIG. 14 is a block diagram showing a first modified example of the damping torque calculation unit. [Figure 15]FIG. 15 is a diagram showing an example of the characteristics of an energy sensitive gain map. [Figure 16] FIG. 16 is a block diagram showing a second modified example of the damping torque calculation unit. [Figure 17] FIG. 17 is a block diagram showing an example of the configuration of a steering direction determination unit according to the second embodiment. [Figure 18] FIG. 18 is a diagram showing an example of a control block configuration for explaining a processing mode of a calculation processing unit in a steering direction determination unit according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a mode for carrying out the invention (hereinafter, referred to as an embodiment) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiment. Furthermore, the components in the following embodiment include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiment can be appropriately combined.

[0020] (Embodiment 1) 1 is a configuration diagram showing an example of an overview of an SBW system including a control device according to embodiment 1. The system includes a reaction device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

[0021] 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.

[0022] The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotation speed of the reaction force motor 31. The reaction force device 30 transmits the vehicle's motion state transmitted from the steered wheels 5L, 5R to the driver as a steering reaction force. The reaction force motor 31 imparts the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

[0023] 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."

[0024] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point that is the limit of possible steering is provided on the column shaft 2. That is, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0025] The steering device 40 includes a steering motor 41, a speed reducing mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 44 that converts the rotational motion of the steering motor 41 into linear motion. The steering device 40 drives the steering motor 41 in response to the steering angle θh, and imparts the driving force to the pinion rack mechanism 44 via the speed reducing mechanism 42, and steers the steered wheels 5L, 5R via the tie rods 3a, 3b. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steered wheels 5L, 5R. Instead of the steering angle θt of the steered wheels 5L, 5R, for example, a motor angle of the steering motor 41 or a position of a rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 is also referred to as the "actual steering angle θt_act".

[0026] In order to coordinately control the reaction force device 30 and the turning device 40, the control device 50 generates a voltage control command value Vref1 for driving and controlling the reaction force motor 31 and a voltage control command value Vref2 for driving and controlling the turning motor 41 based on information such as the steering angle θh and the turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

[0027] The control device 50 is supplied with power from the battery 12 and receives an ignition key signal via the ignition key 11. A CAN (Controller Area Network) 20 that transmits and receives various vehicle information is also connected to the control device 50, and the vehicle speed Vs can also be received from the CAN 20. Furthermore, a non-CAN 21 that transmits and receives communications other than the CAN 20, analog / digital signals, radio waves, etc. can also be connected to the control device 50.

[0028] Specifically, the control device 50 is, for example, an ECU (Electronic Control Unit) mounted on a vehicle. The ECU is mainly composed of a CPU (including an MCU, an MPU, etc.). Fig. 2 is a schematic diagram showing a hardware configuration of the ECU. The cooperative control of the reaction device 30 and the steering device 40 is mainly executed by a program inside the CPU of the ECU.

[0029] Fig. 3 is a diagram showing an example of a control block configuration of a control device according to an embodiment. In Fig. 3, reaction device 30 includes reaction motor 31 and the above-mentioned configuration, as well as a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. Furthermore, steering device 40 includes a PWM control unit 47, an inverter 48, and a motor current detector 49, as well as a steering motor 41 and the above-mentioned configuration. Control device 50 realizes each control block of reaction force control system 60 that controls reaction device 30, and steering control system 70 that controls steering device 40. Reaction force control system 60 and steering control system 70 cooperate to control reaction device 30 and steering device 40.

[0030] Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may include, for example, a RAM (random access memory) or a ROM (read only memory) as shown in Fig. 2 in order to store data, programs, etc. Also, the control device 50 may include a PWM control unit 37, an inverter 38, a motor current detector 39, a PWM control unit 47, an inverter 48, and a motor current detector 49.

[0031] 3, control device 50 includes, as control blocks, steering torque target value generation section 200, steering torque control section 400, current control section 500, steering angle target value generation section 600, steering angle control section 700, and current control section 800. Steering torque target value generation section 200, steering torque control section 400, and current control section 500 are control blocks that constitute reaction force control system 60. Steering angle target value generation section 600, steering angle control section 700, and current control section 800 are control blocks that constitute steering control system 70.

[0032] The reaction force control system 60 performs control so that the actual steering torque Th_act detected by the torque sensor 34 follows a steering torque target value Th_ref, which is a target value of the steering torque of the reaction force device 30.

[0033] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0034] The steering torque control unit 400 generates a motor current command value Ih_ref which is a control target value of a current to be supplied to the reaction force motor 31. The steering torque control unit 400 calculates a motor current command value Imc such that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero.

[0035] The current control unit 500 performs current control of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the 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.

[0036] 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.

[0037] The steering control system 70 performs control so that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

[0038] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0039] Steering angle control unit 700 generates a motor current command value It_ref which is a control target value of the current supplied to steering motor 41. Steering angle control unit 700 calculates the motor current command value It_ref such that the deviation θt_err between the steering angle target value θt_ref and the actual steering angle θt_act approaches zero.

[0040] Current control unit 800 performs current control of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that a deviation It_err between a motor current command value It_ref output from steering angle control unit 700 and an actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0041] In the steering device 40, the steering motor 41 is driven and controlled via a PWM control unit 47 and an inverter 48 based on the voltage control command value Vt_ref.

[0042] In this embodiment, steering torque control section 400, current control section 500, steering angle target value generation section 600, steering angle control section 700 and current control section 800 may have any configuration capable of realizing each control in reaction force control system 60 or steering control system 70, and are not limited by the configuration of each control block. Below, the configuration of steering torque target value generation section 200 according to this embodiment will be described with reference to Fig. 4.

[0043] 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit according to the embodiment. As shown in FIG. 4, the steering torque target value generating unit 200 according to the present embodiment includes a basic map unit 210, a damper torque generating unit 220, and a damping torque generating unit 230 as main components.

[0044] In the present disclosure, the sign extraction unit 280 shown in Fig. 4 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. As a result, the sign extraction unit 280 outputs "1" when the sign of the steering angle θh is "+", and outputs "-1" when the sign of the steering angle θh is "-". Specifically, the sign extraction unit 280 generates, for example, a sign function Sgn(θh) of the steering angle θh.

[0045] Fig. 5A 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 260 are input to the basic map unit 210. The basic map unit 210 generates a torque value Tref_a using the vehicle speed Vs as a parameter, using the basic map shown in Fig. 5A. The torque value Tref_a is used to generate a basic steering reaction force according to the steering angle |θh| and the vehicle speed Vs.

[0046] The torque value Tref_basic has an angle-sensitive characteristic that increases and decreases according to the steering angle |θh|. More specifically, the torque value Tref_basic increases as the steering angle |θh| increases, as shown in FIG. 5A. Also, the torque value Tref_basic has a vehicle-speed-sensitive characteristic that increases and decreases according to the vehicle speed Vs. More specifically, the torque value Tref_basic increases as the vehicle speed Vs increases, as shown in FIG. 5A. That is, the reaction force obtained by the torque value Tref_basic derived by the basic map shown in FIG. 5A increases as the operation amount (steering angle θh) of the steering wheel 1 by the driver increases, and increases as the vehicle speed (vehicle speed Vs) increases. Note that the basic map shown in FIG. 5A has a vehicle-speed-sensitive characteristic, but is not limited thereto.

[0047] Fig. 5B is a diagram showing an example of the characteristics of the torque value Tref_a. The torque value Tref_a shown in Fig. 5B is obtained by multiplying the torque value Tref_basic output from the basic map unit 210 by the sign function Sgn(θh) output from the sign extraction unit 280 in the multiplier 293. Note that a configuration may be adopted in which the sign extraction unit 280 is not included, and the torque value Tref_a is obtained using a basic map corresponding to the positive and negative steering angles θh as shown in Fig. 5B.

[0048] The damper torque generation unit 220 includes a damper gain map unit 221 and a multiplication unit 222. Fig. 6A is a diagram showing an example of a characteristic of the damper gain map. The vehicle speed Vs is input to the damper gain map unit 221. The damper gain map unit 221 generates the damper gain DG by using the damper gain map shown in Fig. 6A.

[0049] The damper gain DG has a vehicle speed response characteristic that increases or decreases according to the vehicle speed Vs, as shown in Fig. 6A. The damper torque generation unit 220 multiplies the angular velocity of the steering wheel 1 (hereinafter also referred to as "steering angular velocity ωh") calculated by differentiating the steering angle θh (differentiation unit 270) by the damper gain DG output from the damper gain map unit 221 (multiplication unit 222), and outputs the result as a torque value Tref_b.

[0050] The torque value Tref_b output from the damper torque generating unit 220 is added to the torque value Tref_a (adder 291). This makes it possible to compensate for the steering reaction force in proportion to the steering angular velocity ωh.

[0051] Fig. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. The torque value Tref_a+Tref_b is obtained by adding the torque value Tref_a to the torque value Tref_a output from the damper torque generating unit 220. In Fig. 6B, the solid line indicates the torque value Tref_a+Tref_b when the steering angular velocity ωh is a positive value (ωh>0), and the dashed line indicates the torque value Tref_a+Tref_b when the steering angular velocity ωh is a negative value (ωh<0). Also, in Fig. 6B, the dashed line indicates the torque value Tref_a.

[0052] Fig. 7 is a region diagram for explaining the steering direction in the present disclosure, in which the horizontal axis indicates the steering angle θh, and the vertical axis indicates the steering angular velocity ωh.

[0053] Area A ((θh,ωh)=(+,+)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh>0) and is turned further to the right (ωh>0). Area B ((θh,ωh)=(+,-)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh>0) and is turned back to the left (ωh<0). Area C ((θh,ωh)=(-,-)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh<0) and is turned further to the left (ωh<0). Area D ((θh,ωh)=(-,+)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh<0) and is turned back to the right (ωh>0). Also, in Figure 7, on the steering angle θh axis (ωh = 0), it is shown that the steering wheel 1 is neither being turned further nor turned back ((θh, ωh) = (θh, 0)), and on the steering angular velocity ωh axis (θh = 0), it is shown that the steering wheel 1 is in the center position ((θh, ωh) = (0, ωh)).

[0054] The torque value Tref_b output from the damper torque generating unit 220 is a positive value in regions A and D where the steering angle velocity ωh>0, and is a negative value in regions B and C where the steering angle velocity ωh<0. As a result, when the steering angle velocity ωh>0, that is, in region A where the steering wheel 1 is turned to the right (θh>0) and further turned to the right, or in region D where the steering wheel 1 is turned to the left (θh<0) and turned back to the right, the torque value Tref_b is added to Tref_a as shown by the solid line in Fig. 6B. When the steering angle velocity ωh<0, that is, in region B where the steering wheel 1 is turned to the right (θh>0) and turned back to the left, or in region C where the steering wheel 1 is turned to the left (θh<0) and turned further to the left, the torque value Tref_a is subtracted by |Tref_b| as shown by the dashed line in Fig. 6B.

[0055] As shown in FIG. 6B, the torque value Tref_a+Tref_b increases with the magnitude of the steering angle θh, and the closer the steering angle θh approaches the steering terminal limit where the steering angle θh is limited by the stopper (rotation limiting mechanism) 35, the smaller the increment of torque increase with respect to the change in steering angle θ becomes. In other words, the torque value Tref_a+Tref_b has a characteristic that the rate of change gradually decreases with an increase in the steering angle θh. For this reason, the driver is likely to turn the steering wheel 1 further near the steering terminal limit, and a sudden further turning may cause a collision (hereinafter also referred to as a "high-speed collision") at the steering terminal limit, which may cause discomfort or strangeness to the driver.

[0056] In the present disclosure, as shown in Fig. 4, a damping torque generating unit 230 is provided that generates a damping torque that increases the rise of the steering reaction force as the steering angular velocity ωh increases, and the torque value Tref_d generated by the damping torque generating unit 230 is added to the torque value Tref_a+Tref_b, and then multiplied by the sign function Sgn(θh) output from the sign extracting unit 280. This suppresses abrupt further turning steering near the steering end. Hereinafter, a specific configuration and operation of the damping torque generating unit 230 according to the embodiment will be described.

[0057] Fig. 8 is a block diagram showing a configuration example of the damping torque calculation unit 240. In the configuration example shown in Fig. 8, the damping torque calculation unit 240 includes an angle sensitive gain map unit 241, an angular velocity sensitive gain map unit 242, a steering direction determination unit 250, and an output value selection unit 251 as main components.

[0058] The damping torque calculation unit 240 performs the process described below for each predetermined period Δt. The predetermined period Δt is determined, for example, by a processing sampling interval in the CPU of the ECU constituting the control device 50. The predetermined period Δt is set to, for example, about 1 ms to 4 ms. Note that the predetermined period Δt may be, for example, one sampling period of the ECU, or may be multiple sampling periods. In other words, the damping torque calculation unit 240 may perform steering direction determination processing at one sampling interval of the ECU, or may perform processing at multiple sampling intervals.

[0059] The sign extraction unit 243 shown in Fig. 8 extracts the sign of the steering angular velocity ωh. Specifically, for example, the value of the steering angular velocity ωh is divided by the absolute value of the steering angular velocity ωh. As a result, the sign extraction unit 243 outputs "1" when the sign of the steering angular velocity ωh is "+", and outputs "-1" when the sign of the steering angular velocity ωh is "-". Specifically, the sign extraction unit 243 generates, for example, a sign function Sgn(ωh) of the steering angular velocity ωh.

[0060] Fig. 9 is a diagram showing an example of the characteristics of an angle sensitive gain map. The steering angle |θh| that has been subjected to absolute value processing in the absolute value calculation unit 248 is input to the angle sensitive gain map unit 241. The angle sensitive gain map unit 241 generates a torque value (third torque value) according to the angle sensitive gain map shown in Fig. 9.

[0061] The angle-sensitive gain map shown in Fig. 9 has an angle-sensitive characteristic in which the gain Ga increases or decreases according to the steering angle |θh|. More specifically, as shown in Fig. 9, the gain Ga increases as the steering angle |θh| increases in a region equal to or greater than a predetermined steering angle threshold |θth|. In other words, the angle-sensitive gain map shown in Fig. 9 has a characteristic in which the gain Ga monotonically increases as the steering angle |θh| becomes larger beyond the steering angle threshold |θth|, that is, as the steering angle |θh| approaches the terminal angle. The steering angle threshold |θth| may be set to an angle at a position a predetermined angle before the terminal angle |θend| (for example, |θth|=|θend|-10[deg]).

[0062] Fig. 10 is a diagram showing an example of the characteristics of an angular velocity sensitive gain map. The steering angular velocity |ωh| that has been subjected to absolute value processing in the absolute value calculation unit 249 is input to the angular velocity sensitive gain map unit 242. The angular velocity sensitive gain map unit 242 generates a torque value (first torque value) according to the angular velocity sensitive gain map shown in Fig. 10.

[0063] The angular velocity-sensitive gain map shown in Fig. 10 has an angular velocity-sensitive characteristic in which the gain Gv increases or decreases according to the steering angular velocity |ωh|. More specifically, the gain Gv increases as the steering angular velocity |ωh| increases, as shown in Fig. 10. In other words, the angular velocity-sensitive gain map shown in Fig. 10 has a characteristic in which the gain Gv monotonically increases as the steering angular velocity |ωh| increases.

[0064] FIG. 11 is a diagram showing an example of the characteristics of the torque value calculated in the damping torque calculation unit. The damping torque calculation unit 240 multiplies the torque value (third torque value) generated by the angle-sensitive gain map unit 241 by the torque value (first torque value) generated by the angular velocity-sensitive gain map unit 242, or by the torque value (second torque value) held by the output value selection unit 251 described later (multiplication unit 244). As a result, as shown in FIG. 11, in a region equal to or greater than a predetermined steering angle threshold |θth|, an angular velocity-sensitive characteristic is obtained in which the torque value increases as the steering angle |θh| increases and increases or decreases according to the steering angular velocity |ωh|. More specifically, the torque value calculated in the damping torque calculation unit 240 has a characteristic that the torque value increases as the steering angle |θh| exceeds the steering angle threshold θth and approaches the terminal angle, and the rate of increase (rate of change) increases as the steering angular velocity |ωh| becomes faster.

[0065] The damping torque calculation section 240 further multiplies the output value of the multiplication section 244 by the sign function Sgn(ωh) of the steering angular velocity ωh (multiplication section 245) and outputs a torque value Tref_d.

[0066] 11, the output value of the multiplier 244 becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster. As a result, the steering reaction force obtained by the torque value Tref_d becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster.

[0067] As described above, the torque value (first torque value) generated by the angular velocity sensitive gain map unit 242 increases as the steering angular velocity |ωh| increases, but if the steering reaction force applied by the reaction force device 30 exceeds the steering force applied by the driver to the steering wheel 1 when the driver turns the steering wheel 1, there may be an instantaneous transition from further turning to returning. Specifically, there may be a transition from area A to area B, or from area C to area D, as shown in FIG. 7. When such a momentary return occurs from further turning of the steering wheel 1, the steering reaction force becomes zero, or a steering reaction force that momentarily tries to turn the wheel further is generated, which may cause a high-speed collision at the steering end caused by the stopper (rotation limiting mechanism) 35, giving the driver discomfort or strange feeling.

[0068] In the present disclosure, when the steering wheel 1 is turned back from an instantaneous further turning as described above, the previous value (second torque value) of the torque value (first torque value) output from the angular velocity sensitive gain map unit 242 is output. This makes it possible to suppress the steering reaction force from becoming zero or the steering reaction force that tries to momentarily turn the steering wheel 1 back from an additional turning when the steering wheel 1 is turned back from an additional turning when the steering wheel 1 is turned back from an instantaneous turning. Below, a detailed description will be given of a configuration and operation that can suppress the steering reaction force from becoming zero or the steering reaction force that tries to momentarily turn the steering wheel 1 back from an additional turning when the steering wheel 1 is turned back from an additional turning when the steering wheel 1 is turned back from an instantaneous turning.

[0069] Fig. 12 is a block diagram showing an example of the configuration of a steering direction determination unit according to embodiment 1. Fig. 13 is a diagram showing an example of a control block configuration for explaining the processing mode of a calculation processing unit in the steering direction determination unit according to embodiment 1.

[0070] The steering angle θh and the steering angular velocity ωh are input to the steering direction determination unit 250. The multiplication unit 252 multiplies the steering angle θh by the steering angular velocity ωh.

[0071] The sign determination unit 253 determines the sign of the multiplication result of the steering angle θh and the steering angular velocity ωh, and generates a sign function Sgn.

[0072] When the sign function Sgn is a positive value (+), it indicates that the vehicle is in area A or area C shown in Fig. 7. In other words, when the sign function Sgn is a positive value (+), it indicates that the steering wheel 1 is turned to the right (θh>0) and has been turned further to the right (ωh>0), or that the steering wheel 1 is turned to the left (θh<0) and has been turned further to the left (ωh<0).

[0073] On the other hand, when the sign function Sgn is a negative value (-), it indicates that the vehicle is in area B or area D shown in Fig. 7. In other words, when the sign function Sgn is a negative value (-), it indicates that the steering wheel 1 is turned to the right (θh>0) and then turned back to the left (ωh<0), or that the steering wheel 1 is turned to the left (θh<0) and then turned back to the right (ωh>0).

[0074] The calculation processing unit 254 performs the steering direction determination process described below at each predetermined period Δt.

[0075] 8 holds the torque value (second torque value) generated by the angular velocity sensitive gain map unit 242 in the previous process (processing a predetermined period of time Δt ago). Specifically, the torque value (second torque value) held by the output value selection unit 251 is the output value of the output value selection unit 251 in the previous process (steering direction determination process a predetermined period of time Δt ago). The output value selection unit 251 is configured by, for example, a RAM of an ECU constituting the control device 50.

[0076] 13, the output value selection unit 251 is controlled to select and output the previous output value (second torque value) held by the output value selection unit 251 when the sign function Sgn transitions from a positive value (+) to a negative value (-), i.e., when the steering wheel 1 is turned back from a state in which it has been turned further, and when the amount of change in the steering angle θh from the previous value is equal to or less than a predetermined change amount threshold Δθth (e.g., 3 [deg]). The change amount threshold Δθth is stored, for example, in a ROM of an ECU constituting the control device 50.

[0077] By repeatedly executing the above-mentioned steering direction determination process at every predetermined period Δt, it is possible to suppress the occurrence of zero steering reaction force or a steering reaction force that tries to momentarily increase steering force when the steering wheel 1 is turned back instantaneously after being turned further. This makes it possible to suppress a high-speed collision at the steering end caused by the stopper (rotation limiting mechanism) 35, and to prevent the driver from feeling uncomfortable or unnatural.

[0078] The damping torque calculation unit may have the following configuration instead of the configuration shown in FIG.

[0079] Fig. 14 is a block diagram showing a first modified example of the damping torque calculation section 240a. In the first modified example shown in Fig. 14, the damping torque calculation section 240a includes an energy calculation section 246 and an energy sensitive gain map section 247 as main components.

[0080] The steering angular velocity ωh is input to the energy calculation unit 246. The energy calculation unit 246 calculates the energy Eg generated by the handle operation (steering) using the following equation.

[0081] Eg=J×ωh 2 / 2

[0082] In the above equation, J represents the moment of inertia. The moment of inertia J is stored in, for example, the ROM of the ECU constituting the control device 50.

[0083] 15 is a diagram showing an example of the characteristics of the energy-sensitive gain map. The energy Eg calculated by the energy calculation unit 246 is input to the energy-sensitive gain map unit 247. The energy-sensitive gain map unit 247 generates a torque value (first torque value) according to the energy-sensitive gain map shown in FIG.

[0084] The energy-sensitive gain map shown in FIG. 15 has an energy-sensitive characteristic in which the gain Ge (Gd2) increases or decreases according to the energy Eg generated by steering the steering wheel 1. More specifically, as shown in FIG. 15, the gain Ge (Gd2) increases as the energy Eg increases. As shown in the above calculation formula, the energy Eg is proportional to the square of the steering angular velocity ωh. In other words, the energy-sensitive gain map shown in FIG. 15 has a characteristic in which the rate at which the gain Ge (Gd2) increases (rate of change) increases as the steering angular velocity ωh increases, similar to the characteristic shown in FIG. 11.

[0085] The damping torque calculation unit 240a outputs a torque value Tref_d obtained by multiplying (multiplication unit 245) the torque value (first torque value) generated by the energy sensitive gain map unit 247 or the torque value (second torque value) held by the output value selection unit 251 by the sign function Sgn(ωh) of the steering angular velocity ωh.

[0086] The output value of the energy sensitive gain map unit 247 becomes larger as the operation speed (steering angular velocity ωh) of the steering wheel 1 by the driver becomes faster, due to the characteristics of the energy sensitive gain map shown in Fig. 15. As a result, the steering reaction force obtained by the torque value Tref_d becomes larger as the operation speed (steering angular velocity ωh) of the steering wheel 1 by the driver becomes faster.

[0087] As described above, since the first torque value (energy sensitive gain Ge) increases as the steering angular velocity ωh increases, if the steering reaction force applied by the reaction force device 30 exceeds the steering force applied by the driver to the steering wheel 1 when the driver turns the steering wheel 1, there may be an instantaneous transition from further turning to returning. If such a momentary return occurs from further turning of the steering wheel 1, and the steering reaction force becomes zero or a steering reaction force that momentarily tries to turn the wheel further occurs, a high-speed collision may occur at the steering end point due to the stopper (rotation limiting mechanism) 35, causing discomfort or an odd feeling to the driver.

[0088] In the configuration having the damping torque calculation unit 240a shown in FIG. 14, similarly to the configuration shown in FIG. 8, by configuring it to have the above-mentioned steering direction determination unit 250 and output value selection unit 251, it is possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn the steering wheel 1 back to its original position when the steering wheel 1 is turned further.

[0089] Fig. 16 is a block diagram showing a second modified example of the damping torque calculation unit. In the second modified example shown in Fig. 16, a damping torque calculation unit 240b includes an energy calculation unit 246 and an energy sensitive gain map unit 247 in the embodiment shown in Fig. 14, instead of the angular velocity sensitive gain map unit 242 in the embodiment shown in Fig. 8.

[0090] The damping torque calculation unit 240b multiplies the torque value (third torque value) generated by the angle sensitive gain map unit 241 by the torque value (first torque value) generated by the energy sensitive gain map unit 247 or the torque value (second torque value) held by the output value selection unit 251 (multiplication unit 244). As a result, similar to the characteristics shown in Fig. 11, an angular velocity sensitive characteristic is obtained which increases as the steering angle |θh| increases in a region equal to or greater than a predetermined steering angle threshold |θth| and which increases or decreases according to the steering angular velocity |ωh|.

[0091] The damping torque calculation section 240b further multiplies the output value of the multiplication section 244 by the sign function Sgn(ωh) of the steering angular velocity ωh (multiplication section 245) and outputs a torque value Tref_d.

[0092] 11, the output value of the multiplier 244 becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster. As a result, the steering reaction force obtained by the torque value Tref_d becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster.

[0093] As described above, since the first torque value (energy sensitive gain Ge) increases as the steering angular velocity ωh increases, if the steering reaction force applied by the reaction force device 30 exceeds the steering force applied by the driver to the steering wheel 1 when the driver turns the steering wheel 1, there may be an instantaneous transition from further turning to returning. If such a momentary return occurs from further turning of the steering wheel 1, and the steering reaction force becomes zero or a steering reaction force that momentarily tries to turn the wheel further occurs, a high-speed collision may occur at the steering end point due to the stopper (rotation limiting mechanism) 35, causing discomfort or an odd feeling to the driver.

[0094] In the configuration having the damping torque calculation unit 240b shown in FIG. 16, similarly to the configuration shown in FIG. 8, by configuring it to have the above-mentioned steering direction determination unit 250 and output value selection unit 251, it is possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn the steering wheel 1 back to its original position when the steering wheel 1 is turned further.

[0095] The torque value Tref_d output from the damping torque generation unit 230 is added to the torque value Tref_a and the torque value Tref_b in the addition units 291 and 292 shown in Fig. 4. As a result, the steering torque target value generation unit 200 outputs the steering torque target value Th_ref.

[0096] As described above, in the damping torque generating section 230 of the present disclosure, the steering direction determining section 250 and the output value selecting section 251 are controlled to hold the output value (second torque value) of the output value selecting section 251 in the previous process, and to select and output the previous output value (second torque value) held by the output value selecting section 251 when the steering wheel 1 is turned back from a state in which it has been turned further and when the amount of change in the steering angle θh from the previous value is equal to or less than a predetermined change amount threshold value Δθth. This makes it possible to suppress the occurrence of zero steering reaction force or a steering reaction force that tries to turn the steering wheel more instantaneously when the steering wheel 1 is turned back instantaneously from a state in which it has been turned further.

[0097] (Embodiment 2) Fig. 17 is a block diagram showing an example of the configuration of a steering direction determination unit according to embodiment 2. Fig. 18 is a diagram showing an example of a control block configuration for explaining the processing mode of a calculation processing unit in the steering direction determination unit according to embodiment 2.

[0098] In the steering direction determination unit 250a, the calculation processing unit 254a performs the steering direction determination process described below every predetermined period Δt.

[0099] 17, the output value selection unit 251 is controlled to select and output the previous output value (second torque value) held by the output value selection unit 251 when the sign function Sgn transitions from a positive value (+) to a negative value (-), i.e., when the steering wheel 1 is turned back from a state in which it has been turned further, and when the time tc during which the sign function Sgn is a negative value (-) is equal to or shorter than a predetermined time threshold Δtth (e.g., 0.5 [sec]). The time threshold Δtth is stored, for example, in the ROM of the ECU constituting the control device 50.

[0100] By repeatedly executing the above-mentioned steering direction determination process at every predetermined period Δt, it is possible to suppress the occurrence of zero steering reaction force or a steering reaction force that tries to momentarily increase steering force when the steering wheel 1 is turned back instantaneously after being turned further, as in the first embodiment. This makes it possible to suppress a high-speed collision at the steering end caused by the stopper (rotation limiting mechanism) 35, and to prevent the driver from feeling uncomfortable or unnatural.

[0101] The figures used in the above-described embodiments are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited to these. Also, the above-described embodiment is an example of a preferred embodiment of the present disclosure, but is not limited thereto, and various modifications can be made without departing from the scope of the present disclosure. [Explanation of symbols]

[0102] 1 Handle 2 Column Axis 3a, 3b tie rod 5L,5R steered wheels 10 Vehicle speed sensor 11 Ignition key 12 Battery 30 Reaction Device 31 Reaction motor 32 Reduction mechanism 33 Steering angle sensor 34 Torque sensor 35 Stopper (rotation limiting mechanism) 40 Steering gear 41 Steering motor 42 Reduction mechanism 43 Angle Sensor 44 Pinion rack mechanism 50 Control device 60 Reaction Force Control System 70 Steering control system 200 Steering torque target value generating unit 210 Basic Map Section 220 Damper torque generating unit 221 Damper gain map section 222 Multiplication section 230 Damping torque generating unit 240, 240a, 240b Damping torque calculation unit 241 Angle-sensitive gain map section 242 Angular velocity sensitive gain map section 243 Code extraction part 244,245 Multiplication section 246 Energy Calculation Unit 247 Energy Sensitive Gain Map Section 248 Absolute value calculation unit 250, 250a Steering direction determination unit 251 Output value selection section 252 Multiplication section 253 Sign determination section 254, 254a Processing unit 260 Absolute value calculation unit 270 Differential part 280 Code extraction part 291,292 Addition section 293 Multiplication section 400 Steering torque control unit 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 800 Current control section

Claims

1. A control device for a vehicle steering system, comprising: a rotation limiting mechanism provided at a steering end of a steering wheel; a reaction device that drives a reaction motor that applies a steering reaction force to the steering wheel; and a steering device that drives a steering motor in accordance with a steering angle of the steering wheel, a steering torque target value generating unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force, The steering torque target value generating unit a torque calculation unit that performs processing at predetermined intervals and generates a first torque value that increases as the steering angular velocity of the steering wheel increases; an output value selection unit that selects either the first torque value or a second torque value that is a held first torque value generated in a previous process, depending on at least whether the steering wheel has been turned back; Equipped with A control device for a vehicle steering system.

2. the output value selection unit selects the second torque value when a multiplication value of the steering angle and the steering angular velocity becomes a negative value from a positive value and an amount of fluctuation of the steering angle is equal to or less than a predetermined amount of fluctuation threshold. The control device for a vehicle steering system according to claim 1.

3. the output value selection unit selects the second torque value when a multiplication value of the steering angle and the steering angular velocity becomes a negative value from a positive value and a time during which the multiplication value is a negative value is equal to or shorter than a predetermined time threshold value. The control device for a vehicle steering system according to claim 1.

4. The first torque value is a value that increases with an increase in energy proportional to the square of the steering angular velocity. A control device for a vehicle steering system according to any one of claims 1 to 3.

5. The torque calculation unit is generating a third torque value whose value increases as the steering angle increases, and multiplying the third torque value by the torque value selected by the output value selection unit; A control device for a vehicle steering system according to any one of claims 1 to 4.

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