Vehicle steering system control device

Abstract

To provide a controller for a vehicular steering system capable of suppressing idling of a handlebar while a vehicle is starting.SOLUTION: A vehicular steering system includes a handlebar lock mechanism for locking the rotation of a handlebar when the ignition of a vehicle is under an off state. A controller for the vehicular steering system includes a reaction device for giving s steering reaction to a handlebar of the vehicle and a steering device for steering a steering wheel of the vehicle. Thus, control of the reaction device is started before the handlebar lock mechanism is changed from a lock state to an unlock state after the ignition is changed from the off state to an on state.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] One type of vehicle steering system is the steer-by-wire (SBW) system, which mechanically separates a steering mechanism (Force Feedback Actuator: FFA) with a steering wheel operated by the driver from a road wheel actuator (RWA) that steers the steered wheels. 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 road wheel actuator generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates a 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. In other words, the steering wheel and the steered wheels are electrically controlled in a coordinated manner.

[0003] In a SBW system, the steering mechanism and the turning mechanism are mechanically separated, so if an external force is applied to the steering wheel while the electrical coordinated control between the steering wheel and the steered wheels is stopped, the steering wheel will rotate regardless of the turning of the steered wheels. Specifically, a situation in which an external force is applied to the steering wheel while the electrical coordinated control between the steering wheel and the steered wheels is stopped can be imagined, for example, when the driver grasps the steering wheel 1 while the vehicle is stopped to get in or out of the vehicle. For this reason, vehicles equipped with a SBW system generally have a configuration in which the steering wheel is locked when the ignition is turned off (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6888531 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described conventional technology, the normal start-up process is performed after the steering wheel is unlocked, and the vehicle transitions to normal driving. In this type of configuration, for example, if the driver turns on the ignition while applying weight to the steering wheel, an external force may be applied to the steering wheel during the period from when the steering wheel is unlocked until the normal start-up process is performed, causing the steering wheel to spin freely, resulting in a discrepancy between the steering angle and the turning angle, which may cause the driver to feel uncomfortable.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a control device for a vehicle steering system that can suppress free spin of the steering wheel when the vehicle is started. [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 comprises a reaction force device that applies a steering reaction force to the steering wheel of the vehicle, and a steering device that steers the steered wheels of the vehicle, and is a control device for a vehicle steering system that is equipped with a steering wheel lock mechanism that locks the rotation of the steering wheel when the ignition of the vehicle is in an off state, and after the ignition transitions from an off state to an on state, starts controlling the reaction force device before transitioning the steering wheel lock mechanism from a locked state to an unlocked state.

[0008] According to the above configuration, spinning of the steering wheel when starting the vehicle is suppressed, and deviation between the steering angle and the turning angle in control after the vehicle start-up process can be suppressed.

[0009] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the reaction force device is controlled in a first control mode after the ignition transitions from an off state to an on state, and is controlled in a second control mode different from the first control mode after the handle lock mechanism transitions from a locked state to an unlocked state.

[0010] According to the above configuration, it is possible to provide a first control mode that suppresses the steering wheel from spinning when the vehicle starts, and a second control mode that performs normal reaction force control.

[0011] A desirable aspect of the control device for a vehicle steering system includes 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 it is preferable that the steering torque target value generation unit generates a steering torque target value in the first control mode such that an actual steering angle that is an actual steering angle of the steering wheel is maintained at the steering angle in the locked state of the steering wheel lock mechanism, and generates a steering torque target value that increases at least as the actual steering angle increases in the second control mode.

[0012] According to the above configuration, while the reaction force device is controlled in the first control mode, spinning of the steering wheel at the time of starting the vehicle is suppressed, and the difference between the steering angle and the turning angle in the control after the vehicle start-up process can be suppressed. Furthermore, reaction force control according to the actual steering angle can be realized in the control after the vehicle start-up process.

[0013] In a preferred embodiment of the control device for a vehicle steering system, the steering torque target value generating section generates a steering torque target value that increases as the vehicle speed of the vehicle increases in the second control mode.

[0014] According to the above configuration, reaction force control according to the vehicle speed can be realized in the control after the vehicle startup process.

[0015] In a preferred embodiment of the control device for a vehicle steering system, it is preferable to detect that the ignition has transitioned from an off state to an on state and control the reaction force device in the first control mode.

[0016] In a preferred embodiment of the control device for a vehicle steering system, it is preferable that an unlock command is sent to the steering wheel lock mechanism after the reaction force device is shifted to the first control mode.

[0017] In a preferred embodiment of the control device for a vehicle steering system, the control device receives an unlock signal indicating that the handle lock mechanism has transitioned from a locked state to an unlocked state, and transitions the reaction force device from the first control mode to the second control mode.

[0018] In a preferred embodiment of the control device for a vehicle steering system, it is preferable that the control of the steering device is started after the reaction force device is shifted from the first control mode to the second control mode.

[0019] According to the above configuration, it is possible to realize cooperative control of the reaction force device and the steering device after the vehicle startup process. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a control device for a vehicle steering system that can suppress free spin of the steering wheel when starting the vehicle. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing the hardware configuration of a control computer that constitutes the control device of the vehicle steering system according to the embodiment. [Figure 3]FIG. 3 is a diagram showing an example of a basic control block configuration for realizing cooperative control of the reaction force device and the steering device in the control device according to the present disclosure. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit in the second control mode. [Figure 5A] FIG. 5A is a diagram showing an example of the characteristics of the basic map. [Figure 5B] FIG. 5B is a diagram showing an example of the characteristics of the torque value Tref_basic. [Figure 6A] FIG. 6A is a diagram showing an example of the characteristics of a damper gain map. [Figure 6B] FIG. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. [Figure 7] FIG. 7 is a region diagram for explaining the steering direction. [Figure 8] FIG. 8 is a block diagram showing an example of the configuration of the steering torque target value generating unit in the first control mode. [Figure 9] FIG. 9 is a flowchart showing an example of a vehicle start-up process in the control device of the vehicle steering system according to the embodiment. [Figure 10] FIG. 10 is a timing chart showing an example of control timing in the vehicle start-up process of the control device of the vehicle steering system according to the embodiment. [Figure 11] FIG. 11 is a conceptual diagram showing an example of the operation of the steering torque target value generating unit in the first control mode. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] 1 is a block diagram showing an example of an outline of an SBW system equipped with a control device according to the present disclosure, which includes a reaction force device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

[0024] The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft (steering shaft, handle shaft) 2, which is found in general electric power steering devices, and instead transmits the driver's operation of the steering wheel 1 as an electrical signal, specifically the steering angle θh output from the reaction force device 30, as an electrical signal.

[0025] 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.

[0026] 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 in real time by the steering angle sensor 33 will also be referred to as the "actual steering angle θh_act," and the steering torque Th detected in real time by the torque sensor 34 will also be referred to as the "actual steering torque Th_act."

[0027] A stopper (rotation limiting mechanism) 35 that physically sets a steering end point, which is the limit of possible steering, is provided on the column shaft 2. That is, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0028] Steering device 40 includes steering motor 41, speed reduction mechanism 42 that reduces the rotational speed of steering motor 41, and pinion rack mechanism 44 that converts the rotational motion of steering motor 41 into linear motion. Steering device 40 drives steering motor 41 in accordance with steering angle θh, and the resulting drive force is applied to pinion rack mechanism 44 via speed reduction mechanism 42, and the drive force is passed through tie rods 3a and 3b to steer steerable wheels 5L and 5R. Steering angle sensor 43 is disposed near pinion rack mechanism 44 and detects steering angle θt of steerable wheels 5L and 5R. Alternatively, for example, the motor angle of steering motor 41 or the position of a rack may be detected and the detected value may be used instead of the steering angle θt of steerable wheels 5L and 5R. Hereinafter, steering angle θt detected by steering angle sensor 43 will also be referred to as "actual steering angle θt_act."

[0029] 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.

[0030] The control device 50 is supplied with power from the battery 12 and receives an ignition signal from the ignition switch 11. The ignition signal is a signal that indicates that the ignition switch 11 is in an on state or an off state.

[0031] In the present disclosure, the column shaft 2 is provided with a handlebar lock mechanism 6 that mechanically locks the handlebar 1. Hereinafter, the state in which the handlebar 1 is locked by the handlebar lock mechanism 6 will also be referred to as the "locked state," and the state in which the handlebar 1 is released from the locked state will also be referred to as the "unlocked state." Note that the handlebar lock mechanism 6 may be configured to be capable of mechanically locking the handlebar 1, and the present disclosure is not limited by the configuration of the handlebar lock mechanism 6.

[0032] The handlebar lock mechanism 6 is electronically controlled by a lock command or an unlock command sent from the control device 50. Specifically, the handlebar lock mechanism 6 transitions from an unlocked state to a locked state based on a lock command from the control device 50, and transitions from the locked state to the unlocked state based on an unlock command from the control device 50. In addition, in the present disclosure, the handlebar lock mechanism 6 transmits an unlock signal to the control device 50 indicating that it has successfully transitioned from the locked state to the unlocked state.

[0033] A CAN (Controller Area Network) 20 that transmits and receives various types of vehicle information is also connected to the control device 50. 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.

[0034] 2 is a schematic diagram showing the hardware configuration of a control computer constituting the control device of the vehicle steering system according to the embodiment. 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.

[0035] The 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. The CPU 101 executes a control program stored in the ROM 102. The reaction force device 30 and the steering device 40 are cooperatively controlled mainly by the control program executed by the ECU 110.

[0036] 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.

[0037] The EEPROM 104 is a nonvolatile memory that can retain its contents even after power is cut off, and stores control data and the like used by the CPU 101 to execute a control program. The various data stored in the EEPROM 104 is used in the control program loaded in the RAM 103 after power is turned on to the ECU 110, and is overwritten in the EEPROM 104 at a predetermined timing. Note that, although an EEPROM is used as the nonvolatile memory here, the present invention is not limited to this, and other nonvolatile memories such as a FLASH-ROM (registered trademark) or an SDRAM may also be used.

[0038] ECU 110 receives an ignition signal from ignition switch 11, detects that ignition switch 11 has transitioned from an off state to an on state while the cooperative control of reaction force device 30 and steering device 40 is stopped, and starts various control programs for realizing the cooperative control of reaction force device 30 and steering device 40. That is, in the present disclosure, ECU 110 is always supplied with power from battery 12 and operates regardless of the state of ignition switch 11. Note that control device 50 may be configured as a single ECU, or may be configured to include a reaction force control ECU that controls reaction force device 30 and a steering control ECU that controls steering device 40.

[0039] FIG. 3 is a diagram showing an example of a basic control block configuration for realizing cooperative control of the reaction force device and the steering device in the control device according to the present disclosure.

[0040] 3, reaction force device 30 includes, in addition to reaction force motor 31 and the above-mentioned configuration, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. Furthermore, turning device 40 includes, in addition to turning motor 41 and the above-mentioned 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 that controls reaction force 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 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, an embodiment may be adopted in which reaction force control system 60 is implemented by the reaction force control ECU, and steering control system 70 is implemented by the steering control ECU. In this case, reaction force control system 60 in the following description may be read as a reaction force control ECU, and turning control system 70 may be read as a turning control ECU.

[0041] 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 of control device 50 may be realized by hardware. Also, a mode in which control device 50 includes PWM control section 37, inverter 38, motor current detector 39, PWM control section 47, inverter 48, and motor current detector 49 may be used.

[0042] 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.

[0043] 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.

[0044] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0045] The steering torque control unit 400 generates a motor current command value Ih_ref, which is a control target value of the current to be supplied to the reaction force motor 31. The steering torque control unit 400 calculates the motor current command value Ih_ref so that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero.

[0046] The current control unit 500 controls the current of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the motor current command value Ih_ref output from the steering torque control unit 400 and the actual current value (motor current value) Ih_act of the reaction force motor 31 detected by the motor current detector 39 approaches zero.

[0047] 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.

[0048] The steering control system 70 performs control such that the actual steering angle θt_act detected by the steering angle sensor 43 follows the target steering angle value θt_ref.

[0049] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0050] Steering angle control unit 700 generates motor current command value It_ref, which is a control target value for the current supplied to steering motor 41. Steering angle control unit 700 calculates motor current command value It_ref such that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero.

[0051] Current control unit 800 controls the current of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that deviation It_err between motor current command value It_ref output from steering angle control unit 700 and actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0052] 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.

[0053] In this embodiment, steering torque control unit 400, current control unit 500, steering angle target value generation unit 600, steering angle control unit 700, and current control unit 800 may be configured to realize each control in reaction force control system 60 or steering control system 70, and are not limited by the configuration of each of these control blocks.

[0054] In the embodiment, the control device 50 starts controlling the reaction force device 30 after the ignition switch 11 transitions from an off state to an on state and before the steering lock mechanism 6 transitions from a locked state to an unlocked state. Specifically, the reaction force device 30 is controlled in a first control mode after the ignition switch 11 transitions from an off state to an on state, and is controlled in a second control mode different from the first control mode after the steering lock mechanism 6 transitions from a locked state to an unlocked state. Here, the second control mode is a normal reaction force control mode for achieving cooperative control of the reaction force device 30 and the steering device 40. Hereinafter, the configuration of the steering torque target value generation unit 200 when the reaction force device 30 is controlled in the second control mode in this embodiment will be described with reference to FIG. 4.

[0055] Fig. 4 is a block diagram showing an example of the configuration of the steering torque target value generator in the second control mode. As shown in Fig. 4, in the second control mode, the steering torque target value generator 200 includes, as main components, a basic map unit 210, a damper torque generator 220, and a steering torque compensation value generator 230.

[0056] 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.

[0057] Fig. 5A is a diagram showing an example of the characteristics of the basic map. The steering angle |θh| and vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation unit 260 are input to the basic map unit 210. The basic map unit 210 generates a torque value Tref_basic using the vehicle speed Vs as a parameter, using the basic map shown in Fig. 5A. The torque value Tref_basic is used to generate a basic steering reaction force according to the steering angle |θh| and the vehicle speed Vs.

[0058] The torque value Tref_basic has an angle-sensitive characteristic that increases or decreases according to the steering angle |θh|. More specifically, as shown in FIG. 5A, the torque value Tref_basic increases as the steering angle |θh| increases. Furthermore, the torque value Tref_basic has a vehicle-speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. More specifically, as shown in FIG. 5A, the torque value Tref_basic increases as the vehicle speed Vs increases. In other words, the reaction force obtained by the torque value Tref_basic derived from the basic map shown in FIG. 5A increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and also increases as the vehicle speed (vehicle speed Vs) increases. Note that although the basic map shown in FIG. 5A has a vehicle-speed-sensitive characteristic, the present invention is not limited to this.

[0059] 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 multiplication unit 293. Note that a configuration without the sign extraction unit 280 may also be adopted in which 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.

[0060] The damper torque generation unit 220 includes a damper gain map unit 221 and a multiplication unit 222. Fig. 6A is a diagram showing an example of the characteristics of the damper gain map. The vehicle speed Vs is input to the damper gain map unit 221. The damper gain map unit 221 generates the damper gain DG using the damper gain map shown in Fig. 6A.

[0061] As shown in Fig. 6A, the damper gain DG has a vehicle speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. The damper torque generation unit 220 multiplies the angular velocity of the steering wheel 1 calculated by differentiating the steering angle θh (hereinafter also referred to as "the steering angular velocity ωh") (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.

[0062] The torque value Tref_b output from the damper torque generating section 220 is added to the torque value Tref_a (addition section 291), thereby making it possible to compensate for the steering reaction force in proportion to the turning angular velocity ωh.

[0063] Fig. 6B is a diagram showing an example of the characteristics of torque value Tref_a+Tref_b. Torque value Tref_a+Tref_b is obtained by adding torque value Tref_a to torque value Tref_b output from damper torque generation section 220. In Fig. 6B, the solid line indicates torque value Tref_a+Tref_b when steering angular velocity ωh is a positive value (ωh>0), and the dashed line indicates torque value Tref_a+Tref_b when steering angular velocity ωh is a negative value (ωh<0). Also in Fig. 6B, the dashed line indicates torque value Tref_a.

[0064] 6B, the torque value Tref_a+Tref_b increases with increasing steering angle θ as the steering angle θh increases and approaches the steering end point limited by the stopper (rotation limiting mechanism) 35. In other words, the torque value Tref_a+Tref_b has a characteristic that the rate of change gradually decreases as the steering angle θh increases.

[0065] 7 is a region diagram for explaining the steering direction in the present disclosure, in which the horizontal axis represents the steering angle θh and the vertical axis represents the steering angular velocity ωh.

[0066] Area A ((θh, ωh) = (+, +)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned further to the right (ωh > 0). Area B ((θh, ωh) = (+, -)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned back to the left (ωh < 0). Area C ((θh, ωh) = (-, -)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned further to the left (ωh < 0). Area D ((θh, ωh) = (-, +)) shown in FIG. 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned back to the right (ωh > 0). Also, in Figure 7, on the steering angle θh axis (ωh=0), it is shown that the steering wheel 1 is neither being turned further nor turned back ((θh, ωh)=(θh, 0)), and on the steering angular velocity ωh axis (θh=0), it is shown that the steering wheel 1 is in the center position ((θh, ωh)=(0, ωh)).

[0067] Torque value Tref_b output from damper torque generation unit 220 is a positive value in regions A and D where the steering angular velocity ωh>0, and a negative value in regions B and C where the steering angular velocity ωh<0. As a result, when the steering angular velocity ωh>0, that is, in region A where the steering wheel 1 is turned to the right (θh>0) and further turned rightward, or in region D where the steering wheel 1 is turned to the left (θh<0) and turned back to the right, torque value Tref_b is a value obtained by adding |Tref_b| to Tref_a, as shown by the solid line in FIG. 6B. Also, when the steering angular velocity ωh<0, that is, in region B where the steering wheel 1 is turned to the right (θh>0) and turned back to the left, or in region C where the steering wheel 1 is turned to the left (θh<0) and turned further leftward, torque value Tref_b is a value obtained by subtracting |Tref_b| from Tref_a, as shown by the dashed line in FIG. 6B.

[0068] The torque value Tref_b output from the damper torque generation unit 220 is added to the torque value Tref_a in the adder 291 shown in Fig. 4. As a result, the steering torque target value generation unit 200 outputs the steering torque target value Th_ref.

[0069] Next, the configuration of the steering torque target value generating section 200 when the reaction force device 30 is controlled in the first control mode will be described with reference to FIG.

[0070] 8 is a block diagram showing an example of the configuration of the steering torque target value generator in the first control mode. In the first control mode, the steering torque target value generator 200a receives the steering angle θh_lock and the actual steering angle θh_act when the steering wheel lock mechanism 6 is in the locked state. The steering angle θh_lock is acquired when the steering wheel lock mechanism 6 is in the locked state and is stored in, for example, the EEPROM 104 of the ECU 110.

[0071] In the first control mode, the steering torque target value generating section 200a calculates the steering torque target value Th_ref such that the deviation θh_err between the steering angle θh_lock and the actual steering angle θh_act approaches zero.

[0072] Below, with reference to Figures 9 and 10, we will explain the specific processing (hereinafter also referred to as "vehicle start-up processing") that takes place in the control device 50 of the vehicle steering system according to the embodiment from the time the driver turns on the ignition until the control device 50 of the vehicle steering system according to the embodiment starts cooperative control of the reaction force device 30 and the turning device 40.

[0073] Fig. 9 is a flowchart illustrating an example of a vehicle startup process in the control device of the vehicle steering system according to the embodiment. Fig. 10 is a timing chart illustrating an example of control timing in the vehicle startup process in the control device of the vehicle steering system according to the embodiment.

[0074] As a premise for the vehicle startup processing shown in Fig. 9, ignition switch 11 is controlled to the OFF state, steering wheel lock mechanism 6 is controlled to the locked state, and cooperative control of reaction force device 30 and steering device 40 is stopped. Specifically, for example, when the driver stops the vehicle, by turning off the ignition, control device 50 controls steering wheel lock mechanism 6 to the locked state, and cooperative control of reaction force device 30 and steering device 40 (reaction force control and steering control) is stopped. Note that the processing from step S102 onwards of the vehicle startup processing shown in Fig. 9 is executed, for example, by detecting that the driver has gotten into the vehicle and turned on the ignition (step S101; Yes).

[0075] While the coordinated control of the reaction force device 30 and the steering device 40 is stopped, the control device 50 monitors the ignition signal from the ignition switch 11 and determines whether the ignition switch 11 has transitioned from an off state to an on state (step S101).If the ignition switch 11 has not transitioned from an off state to an on state (step S101; No), the control device 50 repeatedly executes the processing of step S101.

[0076] At time t11 (see FIG. 10), when it is detected that the ignition switch 11 has transitioned from an off state to an on state (step S101; Yes), the control device 50 stores the actual steering angle acquired by the steering angle sensor 33 as the steering angle θh_lock in the locked state of the steering lock mechanism, for example, in the EEPROM 104 (step S102), and at time t12 (see FIG. 10), starts control (reaction force control) of the reaction force device 30 in the first control mode (step S103).

[0077] Subsequently, at time t13 (see FIG. 10), the control device 50 transmits an unlock command to the handle lock mechanism 6 (step S104).

[0078] The handle lock mechanism 6 transitions from a locked state to an unlocked state based on an unlock command sent from the control device 50, and transmits an unlock signal to the control device 50 indicating that the handle lock mechanism 6 has successfully transitioned from the locked state to the unlocked state.

[0079] 11 is a conceptual diagram showing an example of the operation of the steering torque target value generator in the first control mode. In Fig. 11, the horizontal axis represents the passage of time, and the vertical axis represents the steering torque target value Th_ref in the first control mode.

[0080] When control (reaction force control) of the reaction force device 30 in the first control mode is started in step S103, as described above, the steering torque target value generating unit 200a calculates the steering torque target value Th_ref such that the deviation θh_err between the steering angle θh_lock and the actual steering angle θh_act approaches zero. As a result, for example, as shown in Fig. 11, when control (reaction force control) of the reaction force device 30 in the first control mode is started at time t12 and an external force is applied to the steering wheel 1 at time t13' after time t13 when an unlock command is sent to the steering wheel lock mechanism 6, the steering torque target value Th_ref rises sharply and spin of the steering wheel 1 is suppressed.

[0081] The control device 50 determines whether or not an unlock signal has been received from the handle lock mechanism 6 (step S105), and if an unlock signal has not been received from the handle lock mechanism 6 (step S105; No), it repeatedly executes the processing of step S105.

[0082] At time t14 (see FIG. 10), when an unlock signal is received from the handle lock mechanism 6 (step S105; Yes), the control device 50 starts control of the reaction force device 30 in the second control mode at time t15 (see FIG. 10) (step S106). The time from t14 to t15 can be set to, for example, about 1 millisecond to 10 milliseconds.

[0083] Thereafter, at time t16 (see FIG. 10), the control device 50 starts the steering control of the steering device 40 (step S107), and starts the cooperative control of the reaction force device 30 and the steering device 40.

[0084] By the vehicle startup process according to the embodiment described above, after ignition switch 11 transitions from an off state to an on state, and before steering lock mechanism 6 transitions from a locked state to an unlocked state, control of reaction force device 30 in the first control mode (reaction force control) is started. This suppresses free spin of steering wheel 1 when starting the vehicle. Specifically, for example, it is possible to prevent unintentional free spin of steering wheel 1 when the driver turns on the ignition with a load applied to steering wheel 1. This makes it possible to suppress a discrepancy between the steering angle and the turning angle in the cooperative control of reaction force device 30 and steering device 40 after the vehicle startup process.

[0085] 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. [Explanation of symbols]

[0086] 1 handle 2 column axis 3a, 3b tie rod 5L,5R steered wheels 6 Handle lock mechanism 10 Vehicle speed sensor 11 Ignition switch 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 Steering angle sensor 44 Pinion rack mechanism 50 Control device 60 Reaction Force Control System 70 Steering control system 110 ECU(Electronic Control Unit) 101 CPU(Central Processing Unit) 102 ROM (Read Only Memory) 103 RAM (Random Access Memory) 104 EEPROM (Electrically Erasable Programmable ROM) 105 Bus 200, 200a Steering torque target value generation unit 210 Basic Map Section 220 Damper torque generating unit 221 Damper gain map section 222 Multiplication section 260 Absolute value calculation unit 270 Differential part 280 Code extraction part 291 Addition section 293 Multiplication section 400 Steering torque control unit 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 800 Current control section

Claims

1. A control device for a vehicle steering system including a reaction force device that applies a steering reaction force to a steering wheel of a vehicle, a steering device that steers steered wheels of the vehicle, and a steering wheel lock mechanism that locks rotation of the steering wheel when an ignition of the vehicle is in an off state, After the ignition is switched from an off state to an on state, control of the reaction force device is started before the handle lock mechanism is switched from a locked state to an unlocked state. A control device for a vehicle steering system.

2. The reaction force device is After the ignition is switched from an off state to an on state, it is controlled in a first control mode, After the handlebar lock mechanism transitions from a locked state to an unlocked state, the handlebar lock mechanism is controlled in a second control mode different from the first control mode.

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

3. 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 generation unit In the first control mode, a steering torque target value is generated such that an actual steering angle, which is an actual steering angle of the steering wheel, is maintained at the steering angle in a locked state of the steering wheel lock mechanism, In the second control mode, a steering torque target value is generated that increases at least as the actual steering angle increases.

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

4. The steering torque target value generation unit In the second control mode, a steering torque target value that increases as the vehicle speed increases is generated.

4. The control device for a vehicle steering system according to claim 3.

5. detecting that the ignition has transitioned from an off state to an on state, and controlling the reaction force device in the first control mode; The control device for a vehicle steering system according to any one of claims 2 to 4.

6. After the reaction force device is shifted to the first control mode, an unlock command is sent to the handle lock mechanism. The control device for a vehicle steering system according to claim 5.

7. receiving an unlock signal indicating that the handle lock mechanism has transitioned from a locked state to an unlocked state, and transitioning the reaction force device from the first control mode to the second control mode; 7. The control device for a vehicle steering system according to claim 6.

8. and starting control of the steering device after transitioning the reaction force device from the first control mode to the second control mode. The control device for a vehicle steering system according to claim 7.

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