Steering system, steering control device, and steering control method

Abstract

In a steering system, a steering control device, and a steering control method according to the present invention, in one embodiment, when there is a predetermined amount of difference between a target steering amount in accordance with an operation amount of a steering input member and a steering amount of a wheel, and when the steering input member changes from a first state to a second state, a new target steering amount is acquired on the basis of: the target steering amount in the first state; a difference between the target steering amount in the second state and the target steering amount in the first state; and a coefficient based on information regarding whether or not the change from the first state to the second state is a change away from the steering amount, and a steering actuator is controlled in accordance with the new target steering amount. Thus, the operation amount of the steering input member and the steering amount of the wheel can be synchronized, while suppressing deterioration in operability by the driver and generation of steering noise.

Description

Steering system, steering control apparatus, and steering control method

[0001] The present invention relates to a steering system, a steering control apparatus, and a steering control method.

[0002] The vehicle steering apparatus disclosed in Patent Document 1 drives a steering actuator to bring the steered angle of wheels closer to a predetermined relationship with the steering angle of a steering member when the steered angle deviates from the predetermined relationship relative to the steering angle of the steering member, and sets an upper limit value for vehicle speed or acceleration.

[0003] Japanese National Publication of International Patent Application No. 2023-519465

[0004] In a steer-by-wire steering system, when a deviation occurs between an operation amount of a steering input member such as a steering wheel and a steered amount of wheels, it is required to synchronize the operation amount and the steered amount (in other words, reduce the deviation to within an allowable range). However, when an attempt is made to synchronize the operation amount and the steered amount by causing the steered amount of wheels to follow a target steered amount corresponding to the operation amount of the steering input member, causing the steered amount of wheels to instantaneously follow the operation amount of the steering wheel may generate a steering noise, or may change the steered amount in a direction opposite to an operation direction of the steering input member by a driver. A change in the steered amount in the direction opposite to the operation direction of the steering input member by the driver causes vehicle behavior that ignores the driver's steering intention, which has a problem of reducing drivability for the driver.

[0005] The present invention has been made in view of conventional circumstances, and an object of the present invention is to provide a steering system, a steering control apparatus, and a steering control method that can synchronize an operation amount of a steering input member and a steered amount of wheels while suppressing a decrease in drivability for a driver and generation of steering noise.

[0006] Therefore, according to the steering system, steering control device, and steering control method of the present invention, in one embodiment, there is a predetermined difference between the target steering amount corresponding to the amount of operation of the steering input member and the amount of steering of the wheel. When the steering input member changes from a first state to a second state, a new target steering amount is obtained based on the target steering amount in the first state, the difference between the target steering amount in the second state and the target steering amount in the first state, and a coefficient based on information as to whether the change from the first state to the second state is a change that moves away from the amount of steering, and the steering actuator is controlled according to the new target steering amount.

[0007] According to the present invention, it is possible to synchronize the amount of operation of the steering input member with the amount of steering of the wheels while suppressing a decrease in maneuverability and the generation of steering noise by the driver.

[0008] This is a schematic diagram of the steering system. This is a block diagram showing the control of limiting steering torque and increasing reaction torque. This is a time chart illustrating the change in actual steering amount under normal control. This is a block diagram showing synchronous control based on a new target steering amount. This is a time chart illustrating the change in actual steering amount and steering operation amount under synchronous control. This is a diagram illustrating the map characteristics of the coefficient G for steering inward. This is a diagram illustrating the map characteristics of the coefficient G for steering outward. This is a diagram illustrating the transition of the actual pinion angle and pinion angle command value. This is a flowchart showing the control processing procedure when steering becomes impossible due to a curb collision.

[0009] Hereinafter, embodiments of the steering system, steering control device, and steering control method according to the present invention will be described with reference to the drawings. Figure 1 is a configuration diagram showing one aspect of a steer-by-wire type steering system 1000 mounted on a four-wheeled vehicle 1. The steering system 1000 is a system that varies the amount of steering (in other words, the steering angle or tire angle) of the front wheels 2L and 2R of the vehicle 1 according to the amount of operation (in other words, the operation angle or operation position) of the steering wheel 500, which is a steering input member.

[0010] However, the steering input member is not limited to the steering wheel 500, but may be a lever or joystick, etc. Also, the wheels steered by the steering system 1000 are not limited to the front wheels 2L and 2R, but may be a system in which the rear wheels are steered.

[0011] The steering system 1000 comprises a steering device 2000 and a steering operation input device 3000, which are mechanically separated from each other and arranged in the vehicle 1. The steering device 2000 varies the amount of steering of the front wheels 2L and 2R by the steering torque applied to the front wheels 2L and 2R by a steering motor 100, which is a steering actuator. The steering operation input device 3000 applies a pseudo-reaction torque to the steering wheel 500 by the operation of a reaction motor 600, which is a reaction actuator.

[0012] The steering device 2000 includes a steering motor 100 that generates steering torque to be applied to the front wheels 2L and 2R, a steering control device 200 that drives and controls the steering motor 100, a steering mechanism 300, and a steering amount sensor 400 that detects the position of the steering mechanism 300 as information regarding the amount of steering of the front wheels 2L and 2R. In other words, the steering device 2000 has a steering motor 100 that detects the amount of steering of the front wheels 2L and 2R and applies steering torque to the front wheels 2L and 2R. The steering mechanism 300 is a mechanism that converts the rotational motion of the output shaft of the steering motor 100 into the linear motion of the steering rod 310, and in this embodiment, a rack and pinion is used.

[0013] The rotational driving force of the steering motor 100 is transmitted to the pinion shaft 330 via the reduction gear 320. The steering rod 310 is provided with a rack 311 that meshes with the pinion 331 mounted on the pinion shaft 330. When the pinion 331 rotates in response to the rotational driving force of the steering motor 100, the steering rod 310 moves horizontally in the left-right direction of the vehicle 1, thereby changing the amount of steering of the front wheels 2L and 2R.

[0014] Here, the steering amount sensor 400 consists of a pinion angle sensor that detects the angle of the pinion 331, or a stroke sensor that detects the amount of movement of the rack 311. In other words, the pinion angle detected by the pinion angle sensor and the amount of movement of the rack 311 detected by the stroke sensor are detected values ​​that correlate with the steering amount of the front wheels 2L and 2R.

[0015] The steering motor 100 is a brushless motor and has a steering motor rotation angle sensor 101 capable of detecting the rotation angle of the motor shaft. The steering motor rotation angle sensor 101 is, for example, composed of a Hall sensor. The steering control device 200 performs closed-loop control, switching the current to the coil of the steering motor 100 based on the rotation angle detected by the steering motor rotation angle sensor 101, and outputs a drive signal to the steering motor 100. The steering mechanism 300 can be a mechanism using, for example, a ball screw instead of a rack and pinion.

[0016] The steering input device 3000 includes a steering wheel 500 as a steering input member operated by the driver of the vehicle 1, a steering shaft 510 that rotates in conjunction with the rotation of the steering wheel 500, a reaction force motor 600 as a reaction force actuator that generates a reaction force torque to be applied to the steering wheel 500, a steering input control device 700 that drives and controls the reaction force motor 600, and an operating amount sensor 800 that detects the amount of operation of the steering wheel 500. In other words, the steering input device 3000 has a reaction force motor 600 that detects the amount of operation of the steering wheel 500 and applies a reaction force torque to the steering wheel 500.

[0017] The reaction motor 600 is a brushless motor and has a reaction motor rotation angle sensor 601 that can detect the rotation angle of the motor shaft. The steering input control device 700 performs closed-loop control to switch the current to the coil of the reaction motor 600 based on the rotation angle detected by the reaction motor rotation angle sensor 601, and outputs a drive signal to the reaction motor 600.

[0018] The steering control device 200 and the steering input control device 700 are electronic control devices equipped with a microcomputer. The microcomputers in the steering control device 200 and the steering input control device 700 are configured to include a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), etc., and execute the control contents of this embodiment. The steering control device 200 and the steering input control device 700 are connected to an in-vehicle network such as a Controller Area Network (CAN), and communication takes place between the steering control device 200 and the steering input control device 700, and between the steering control device 200 and / or the steering input control device 700 and other electronic control devices other than the steering system 1000.

[0019] The steering input control device 700 calculates a target steering amount based on the amount of steering wheel 500 maneuver detected by the maneuver amount sensor 800, and transmits the calculated target steering amount information to the steering control device 200. The steering control device 200 then compares the target steering amount information obtained from the steering input control device 700 with the actual steering amount information of the front wheels 2L and 2R detected by the steering amount sensor 400, and provides feedback control to the power supply to the steering motor 100 so that the actual steering amount follows the target steering amount. Alternatively, the steering input control device 700 can be configured to transmit the amount of steering wheel 500 maneuver information to the steering control device 200, and the steering control device 200 can determine the target steering amount based on the acquired information on the amount of steering wheel 500 maneuver.

[0020] Furthermore, the steering input control device 700 of the steering operation input device 3000 determines a target reaction force torque based on the amount of operation of the steering wheel 500 detected by the operation amount sensor 800, and controls the energization of the reaction force motor 600 according to the target reaction force torque. In other words, the control device 1100, which includes the steering control device 200 and the steering input control device 700, outputs drive signals to the steering motor 100 and the reaction force motor 600 according to the amount of operation of the steering wheel 500.

[0021] Furthermore, when the steering amount sensor 400 detects the pinion angle, which is the angle of the pinion 331, as a state variable correlated with the actual steering amount of the front wheels 2L and 2R, the steering input control device 700 determines the pinion angle command value PATG as the target steering amount based on the amount of operation of the steering wheel 500 and the steering gear ratio, and the steering control device 200 can control the steering motor 100 by comparing the actual pinion angle RPA with the pinion angle command value PATG. The following embodiment will describe steering control based on the pinion angle as one aspect.

[0022] Here, the steering control device 200 and the steering input control device 700 have a control function to deal with situations where steering becomes temporarily impossible, such as when the front wheels 2L and 2R hit an obstacle such as a curb, in addition to normal steering control and reaction force control. Specifically, the steering control device 200 has a control function to limit the increase in steering torque when steering becomes impossible, such as when the front wheels 2L and 2R hit an obstacle such as a curb. This control function that limits the increase in steering torque prevents damage to the steering system 1000 and the vehicle 1 from being caused by continuously applying excessive steering torque.

[0023] Furthermore, the steering input control device 700 has a control function that increases the reaction torque when the front wheels 2L and 2R hit an obstacle such as a curb and become unable to steer. This control function that increases the reaction torque allows the driver to recognize the state of being unable to steer (hitting a curb).

[0024] Figure 2 is a block diagram showing one mode of steering torque limit control and reaction torque increase control when the front wheels 2L and 2R hit an obstacle such as a curb and become unable to steer. The steering control device 200 has a deadlock determination unit 201, a timer unit 202, and a torque limit value increase / decrease unit 203.

[0025] The deadlock determination unit 201 is a functional unit that determines a deadlock state in which the steering amount does not change even when a steering torque exceeding a predetermined amount is applied to the front wheels 2L and 2R. When a deadlock state is in place, control is executed to limit the increase in steering torque. The deadlock determination unit 201 acquires information such as the actual pinion angular velocity ΔRPA, which indicates the rate of change of the actual steering amount; the steering torque command value set to bring the actual pinion angle RPA (actual steering amount) closer to the pinion angle command value PATG (target steering amount); and the vehicle speed. The actual pinion angular velocity ΔRPA is obtained by differentiating the detected value of the actual pinion angle RPA by the sensor with respect to time, and the vehicle speed is estimated, for example, from the detected wheel speed of each wheel.

[0026] The deadlock determination unit 201 then determines whether each of the following first to fourth deadlock intervention conditions is met or not, and the timer unit 202, based on the determination result from the deadlock determination unit 201, determines the following fifth deadlock intervention condition. When all of the first to fifth deadlock intervention conditions are met, the timer unit 202 outputs a signal indicating intervention in a deadlock state where the steering amount does not change even when a steering torque greater than a predetermined amount is applied to the front wheels 2L and 2R.

[0027] [Deadlock Intervention Conditions] ・First Deadlock Intervention Condition: The system is functioning normally. ・Second Deadlock Intervention Condition: The actual pinion angular velocity ΔRPA is less than the predetermined rate of change. ・Third Deadlock Intervention Condition: The steering torque command value (command value before limit) is equal to or greater than the predetermined torque. ・Fourth Deadlock Intervention Condition: The vehicle speed is less than the predetermined vehicle speed. ・Fifth Deadlock Intervention Condition: A predetermined time has elapsed with all of the first to fourth deadlock intervention conditions met.

[0028] The second deadlock intervention condition, "actual pinion angular velocity ΔRPA is less than a predetermined change speed," indicates that the direction of the front wheels 2L and 2R has not changed. The third deadlock intervention condition, "steering torque command value is greater than or equal to a predetermined torque," indicates that the steering torque command value has increased due to a difference between the pinion angle command value PATG and the actual pinion angle RPA. The fourth deadlock intervention condition, "vehicle speed is less than a predetermined vehicle speed," indicates that the front wheels 2L and 2R have hit an obstacle such as a curb and come to a stop. Adding these conditions prevents false detection of deadlock due to sudden changes in steering torque during driving.

[0029] Furthermore, when the deadlock determination unit 201 determines that at least one of the following first to fourth deadlock release conditions is met, the timer unit 202 outputs a signal indicating release from the deadlock state. [Deadlock Release Conditions] ・First deadlock release condition: The system is not functioning normally. ・Second deadlock release condition: The actual pinion angular velocity ΔRPA is greater than or equal to a predetermined rate of change. ・Third deadlock release condition: The steering torque command value (command value before limit) is less than a predetermined torque. ・Fourth deadlock release condition: The vehicle speed is greater than or equal to a predetermined vehicle speed.

[0030] The second deadlock release condition, "actual pinion angular velocity ΔRPA is greater than or equal to a predetermined rate of change," indicates that the front wheels 2L and 2R are now able to move. The third deadlock release condition, "steering torque command value is less than a predetermined torque," indicates that a large steering torque is no longer required because the front wheels 2L and 2R are now able to move. The fourth deadlock release condition, "vehicle speed is greater than or equal to a predetermined vehicle speed," indicates that the positional relationship between vehicle 1 (front wheels 2L and 2R) and the obstacle (curb) has changed, potentially allowing the front wheels 2L and 2R to move.

[0031] The torque limit adjustment unit 203 is a functional unit that changes the upper limit of the steering torque command value based on signals from the timer unit 202 indicating intervention and release from a deadlock state. In a deadlock state, the upper limit of the steering torque command value is lower than when there is no deadlock state. Specifically, the torque limit adjustment unit 203 gradually reduces the upper limit of the steering torque command value from the default value to the value applied in the deadlock intervention state after intervention in a deadlock state (in other words, it gradually strengthens the limit on increasing the steering torque command value).

[0032] Furthermore, the torque limit value increase / decrease unit 203 gradually increases the upper limit of the steering torque command value from the value in the deadlock state to the default value after the deadlock state is released (in other words, it gradually loosens the limit on increasing the steering torque command value), thereby canceling the steering torque limit (decrease in the upper limit) applied to the deadlock state. In other words, when the torque limit value increase / decrease unit 203 cancels the decrease in the upper limit of the steering torque command value, it gradually returns the upper limit of the steering torque command value to the value it was when not in a deadlock state, over time.

[0033] The upper limit of the steering torque command value output by the torque limit value increase / decrease unit 203 (steering torque limit value) is compared with the steering torque command value set to bring the actual pinion angle RPA closer to the pinion angle command value PATG, and the increase of the steering torque command value is limited so that the steering torque command value does not exceed the upper limit value. In the determination of the third deadlock intervention condition and the third deadlock release condition described above, the fulfillment or non-fulfillment of the intervention condition and release condition is determined based on the steering torque command value before being limited by the above upper limit value.

[0034] In this way, the steering control device 200 prevents excessive steering torque from being continuously applied in a deadlock state where steering is impossible even when a steering torque exceeding a predetermined amount is applied to the front wheels 2L and 2R, by lowering the upper limit of the steering torque command value compared to when there is no deadlock state (in other words, limiting the increase of the steering torque command value), thereby preventing damage to the steering system 1000 (steering device 2000) and the vehicle 1. Furthermore, the steering control device 200 gradually changes the upper limit of the steering torque command value (steering torque limit value) in response to the switching between intervention and release from a deadlock state, thereby preventing abrupt changes in the amount of steering due to a sudden change in the final steering torque command value after the limiting process.

[0035] On the other hand, the steering input control device 700 has the following functional units: a curb collision state determination unit 701, an intervention determination unit 702, a reference control amount setting unit 703, a control amount change calculation unit 704, a reaction force torque calculation unit 705, a rate limiter unit 706, an upper limit limiter setting unit 707, and a limiter unit 708. The curb collision state determination unit 701 acquires the following signals from the timer unit 202: an intervention and release determination signal for a deadlock state, the actual pinion angular velocity ΔRPA indicating the rate of change of the actual steering amount, the actual pinion angle RPA indicating the actual steering amount, and the pinion angle command value PATG corresponding to the target steering amount.

[0036] The curb collision state determination unit 701 then determines the intervention of a curb collision state, which is a state in which the front wheels 2L and 2R have hit an obstacle such as a curb and are unable to steer in the desired direction, when all of the following two curb collision intervention conditions are met. [Curb collision intervention conditions] ・First curb collision intervention condition: The system is normal. ・Second curb collision intervention condition: Deadlock state is ON.

[0037] Furthermore, the curb collision state determination unit 701 determines that the vehicle has departed from the curb collision state if at least one of the following three curb collision departure conditions is met. [Curb Collision Departure Conditions] ・First curb collision departure condition: The system is not functioning normally. ・Second curb collision departure condition: The actual pinion angular velocity ΔRPA is greater than or equal to a predetermined rate of change. ・Third curb collision departure condition: Both of the following two curb collision departure conditions 3-1 and 3-2 are met. ・3-1 curb collision departure condition: The difference between the pinion angle command value PATG and the actual pinion angle RPA (control error in steering amount) is less than a predetermined value. ・3-2 curb collision departure condition: The deadlock state is OFF.

[0038] The second curb collision release condition, "actual pinion angular velocity ΔRPA is greater than or equal to a predetermined rate of change," indicates that the direction of the front wheels 2L and 2R has become movable. The third curb collision release condition is designed to prevent a release judgment from being made if there is a difference between the pinion angle command value PATG and the actual pinion angle RPA, even if the deadlock state has been released, as there is a possibility that the curb collision has not been released.

[0039] The intervention determination unit 702 acquires a signal indicating the latest determination result from the curb collision state determination unit 701 and an inverted signal of the signal indicating the previous determination result from the curb collision state determination unit 701. The intervention determination unit 702 then performs a logical AND operation between the signal indicating the latest determination result from the curb collision state determination unit 701 and the inverted signal of the signal indicating the previous determination result from the curb collision state determination unit 701, and outputs a high signal (initial intervention determination signal) when intervention for a curb collision state is determined for the first time after the system starts up.

[0040] The reference control amount setting unit 703 acquires the output of the intervention determination unit 702 and the detection signal of the steering wheel 500's control amount. When the output of the intervention determination unit 702 goes high, that is, when intervention for a curb collision is determined for the first time after the system starts up, the reference control amount of the steering wheel 500 at that time is set as the reference control amount, and continues to output it as the reference control amount even after the output of the intervention determination unit 702 switches to low.

[0041] The operation amount change calculation unit 704 calculates a deviation between a reference operation amount, which is the operation amount of the steering wheel 500 when intervention in a curb collision state is determined for the first time after system startup, and the latest value of the operation amount of the steering wheel 500. That is, the deviation of the operation amount of the steering wheel 500 obtained by the operation amount change calculation unit 704 is a change amount of the operation amount from when intervention in a curb collision state is determined for the first time after system startup.

[0042] The reaction torque calculation unit 705 acquires a signal of the change amount of the operation amount of the steering wheel 500 from the operation amount change calculation unit 704, multiplies the change amount of the operation amount by a spring rate to obtain the reaction torque when a curb collision state is intervened. That is, when the driver further operates the steering wheel 500 in the impacting direction even after the front wheels 2L and 2R impact an obstacle such as a curb, the reaction torque calculation unit 705 increases the reaction torque compared to when there is no impacting state, thereby allowing the driver to recognize that the front wheels 2L and 2R are impacting an obstacle such as a curb.

[0043] The rate limiter unit 706 performs processing for limiting the change amount per calculation cycle of the reaction torque output by the reaction torque calculation unit 705 within a set value. The limiter unit 708 limits the reaction torque after rate limiter processing output from the rate limiter unit 706 to be equal to or less than an upper limiter, and outputs the result.

[0044] The upper limiter used in the limiter unit 708 is variably set in the upper limiter setting unit 707 in accordance with intervention and withdrawal from a curb collision state. The upper limiter setting unit 707 sets the upper limiter for the reaction torque to a default value when a curb collision state is intervened. On the other hand, when withdrawing from the curb collision state, the upper limiter setting unit 707 gradually decreases the value of the upper limiter for the reaction torque with the reaction torque at the time of withdrawal set as an initial value (in other words, gradually restores the reaction torque as time passes), thereby gradually decreasing the reaction torque when withdrawing from the curb collision state and canceling the increase control of the reaction torque in the curb collision state.

[0045] Here, the reaction torque in the curb collision state is calculated in detail in accordance with Mathematical Formula 1. In Mathematical Formula 1, Tc is the reaction torque when the curb collision state occurs, θ is the operation amount of the steering wheel 500, k is the spring rate, and θc is the operation amount of the steering wheel 500 at the first time when the curb collision state occurs. That is, when the reaction torque is being gradually decreased after exiting the curb collision state, if the curb collision state occurs again, maintaining the reaction torque at the previous value without changing the reaction torque by an amount corresponding to the change in the operation amount suppresses sudden changes in the reaction torque.

[0046] By the way, when exiting from a state where the front wheels 2L and 2R hit an obstacle such as a curb and cannot be steered, if there is a difference (steering amount control error, phase shift) between a target steering amount (pinion angle command value PATG) corresponding to the operation amount of the steering wheel 500 and an actual steering amount (actual pinion angle RPA), as a result of performing feedback control to bring the actual steering amount closer to the target steering amount, there is a possibility that the steering amounts of the front wheels 2L and 2R are changed in a direction opposite to the operation direction of the steering wheel 500, or a steering noise is generated.

[0047] FIG. 3 is a time chart illustrating changes in the operation amount of the steering wheel 500 (the target steering amount based on the operation amount) and the actual steering amount when feedback control for bringing the actual steering amount closer to the target steering amount corresponding to the operation amount of the steering wheel 500 is performed in a state where a predetermined amount of control error occurs in the steering amount. The predetermined amount of control error is a control error of a magnitude exceeding the response delay that occurs when causing the actual steering amount to follow a change in the target steering amount according to the operation of the steering wheel 500 in a state where the steering amounts of the front wheels 2L and 2R can be normally changed.

[0048] At time t0 in Figure 3, the front wheels 2L and 2R have released the state in which they were unable to steer due to hitting an obstacle such as a curb. At this time, although the front wheels 2L and 2R are steered to the left of the neutral position (straight-ahead position), the steering wheel 500 is in the neutral position, and the target steering amount is set to the neutral position. From this state, the driver operates the steering wheel 500 to the left from the neutral position, but the feedback control that brings the actual steering amount closer to the target steering amount controls the front wheels 2L and 2R to the right in order to bring the steering amount closer to the neutral position. In other words, even though the driver is operating the steering wheel 500 to the left, the steering amount of the front wheels 2L and 2R changes to the right, which can result in vehicle behavior that disregards the driver's intention to steer.

[0049] Therefore, if there is a predetermined difference between the target steering amount corresponding to the amount of steering wheel 500 operation and the actual steering amount of the front wheels 2L and 2R, the steering control device 200 performs synchronous control to gradually converge the difference between the target steering amount corresponding to the amount of steering wheel 500 operation and the actual steering amount in accordance with the driver's operation of the steering wheel 500. Specifically, in synchronous control, the steering control device 200 determines a target change in the steering amount of the front wheels 2L and 2R according to the change in the amount of steering wheel 500 operation, and changes the steering amount of the front wheels 2L and 2R by the target change in a direction that matches the direction of operation of the steering wheel 500.

[0050] Furthermore, the steering control device 200 sets the gain of the target change in the steering amount of the front wheels 2L and 2R in relation to the change in the amount of steering wheel 500 operation to be smaller when the operation of the steering wheel 500 is an operation that approaches the steering amount of the front wheels 2L and 2R than when the operation is an operation that moves away from the steering amount of the front wheels 2L and 2R. In this application, the operation of the steering wheel 500 that approaches the steering amount of the front wheels 2L and 2R is called a counter-turn operation, and the operation of the steering wheel 500 that moves away from the steering amount of the front wheels 2L and 2R is called a turn-in operation. With this synchronous control, it is possible to suppress the generation of steering noise and the occurrence of vehicle behavior that disregards the driver's intention to steer due to synchronization.

[0051] Figure 4 is a block diagram showing in detail the synchronous control performed by the steering control device 200, which gradually reduces the difference between the target steering amount and the actual steering amount. The steering control device 200 has a deadlock determination unit 201, a control state determination unit 220, and a target value generation unit 230 as functional units for performing synchronous control. As described above, the deadlock determination unit 201 determines whether or not a deadlock state is in which the steering amount does not change even when steering torque is applied to the front wheels 2L and 2R, based on the command values ​​of the actual pinion angular velocity ΔRPA, which indicates the rate of change of the actual steering amount, the vehicle speed, and the steering torque.

[0052] The control state determination unit 220 obtains a determination signal from the deadlock determination unit 201 indicating whether or not a deadlock state exists, and also obtains signals for the actual pinion angular velocity ΔRPA (which indicates the rate of change of the actual steering amount), vehicle speed, pinion angle command value PATG (target steering amount), and actual pinion angle RPA (actual steering amount). The control state determination unit 220 then determines whether or not the vehicle is driving when it is released from a deadlock state, whether or not the amount of steering wheel 500 is being operated, and if the steering wheel 500 is being operated, whether or not the operation is a counter-turn operation, which is an operation that approaches the steering amount of the front wheels 2L and 2R (actual pinion angle RPA), or a turn-in operation, which is an operation that moves away from the steering amount of the front wheels 2L and 2R (actual pinion angle RPA).

[0053] In this application, the neutral position (straight-ahead position) is represented as 0 degrees, a positive value indicates a steering amount to the left of the neutral position, and a negative value indicates a steering amount to the right of the neutral position. Therefore, when the pinion angle command value PATG and the actual pinion angle RPA are positive values ​​greater than 0 degrees, it indicates a command to steer the front wheels 2L and 2R to the left of the neutral position, or a state in which the front wheels 2L and 2R are actually steered to the left of the neutral position. When the pinion angle command value PATG and the actual pinion angle RPA are negative values ​​less than 0 degrees, it indicates a command to steer the front wheels 2L and 2R to the right, or a state in which the front wheels 2L and 2R are actually steered to the right.

[0054] Furthermore, the pinion angular velocity command value ΔPATG is the rate of change per unit time of the pinion angle command value PATG (target steering amount) corresponding to the amount of steering wheel 500 is operated. Therefore, when the pinion angular velocity command value ΔPATG is positive, it indicates that the steering wheel 500 is being operated to the left, and when the pinion angular velocity command value ΔPATG is negative, it indicates that the steering wheel 500 is being operated to the right.

[0055] The control state determination unit 220 then determines whether the driver's operation of the steering wheel 500 is a counter-turn operation or a turn-in operation based on the following determination conditions: [Determination conditions for a turn-in operation] Pinion angular velocity command value ΔPATG ≤ 0, and pinion angle command value PATG < actual pinion angle RPA, or pinion angular velocity command value ΔPATG ≥ 0, and pinion angle command value PATG > actual pinion angle RPA.

[0056] [Conditions for determining the cutback operation] Pinion angular velocity command value ΔPATG ≤ 0, and pinion angle command value PATG ≥ actual pinion angle RPA, or pinion angular velocity command value ΔPATG ≥ 0, and pinion angle command value PATG ≤ actual pinion angle RPA.

[0057] Figure 5 is a time chart illustrating the correlation between the amount of steering wheel 500 manipulated (target steering amount based on the amount of manipulation) and the actual steering amount in synchronous control, and also showing the distinction between steering in and steering out. Here, between time t3 and time t4 and between time t5 and time t6, the steering wheel 500 is being manipulated to the left, in other words, the amount of steering wheel 500 manipulated is changing to the left.

[0058] Furthermore, between time t3 and time t4, and between time t5 and time t6, both the pinion angle command value PATG and the actual pinion angle RPA based on the amount of steering wheel 500 manipulated are greater than or equal to zero, and the actual pinion angle RPA is greater than the pinion angle command value PATG based on the amount of steering wheel 500 manipulated. In other words, between time t3 and time t4, and between time t5 and time t6, the conditions of pinion angular velocity command value ΔPATG ≥ 0 and pinion angle command value PATG ≤ actual pinion angle RPA are met, which corresponds to the steering wheel 500 being reversed.

[0059] Furthermore, between time t4 and time t5, and between time t6 and time t7, the steering wheel 500 is in a state of being operated to the right, in other words, the amount of operation of the steering wheel 500 is changing to the right. Moreover, between time t4 and time t5, and between time t6 and time t7, both the pinion angle command value PATG and the actual pinion angle RPA based on the amount of operation of the steering wheel 500 are greater than or equal to zero, and the actual pinion angle RPA is greater than the pinion angle command value PATG based on the amount of operation of the steering wheel 500.

[0060] In other words, between time t4 and time t5, and between time t6 and time t7, the conditions of pinion angular velocity command value ΔPATG ≤ 0 and pinion angle command value PATG < actual pinion angle RPA are met, which corresponds to the steering wheel 500 being turned in. Also, between time t2 and time t3, immediately after the deadlock is released, the steering wheel 500 is not operated and the amount of operation is constant, so the pinion angular velocity command value ΔPATG is zero, and the conditions of pinion angle command value PATG < actual pinion angle RPA are met, which corresponds to the steering wheel 500 being turned in. Note that time t1 in Figure 5 is a deadlock state where the front wheels 2L and 2R are stuck against an obstacle such as a curb and cannot move.

[0061] The target value generation unit 230 shown in Figure 4 acquires the control state determination result from the control state determination unit 220, and further acquires the pinion angle command value PATG, the actual pinion angle RPA, and the vehicle speed signals. When the vehicle is released from a deadlock state, if there is a predetermined difference between the pinion angle command value PATG (target steering amount) based on the amount of steering wheel 500 operation and the actual pinion angle RPA (actual steering amount), the target value generation unit 230 calculates and outputs a new pinion angle command value NPATG (new target steering amount), which is the pinion angle command value PATG used in synchronous control, instead of the pinion angle command value PATG (target steering amount) determined from the amount of steering wheel 500 operation and the steering gear ratio.

[0062] Here, the target value generation unit 230 determines the new pinion angle command value NPATG according to equation 2. In equation 2, NPATG(n-1) is the previous value of the new pinion angle command value NPATG, PATG(n) is the current value of the pinion angle command value PATG, PATG(n-1) is the previous value of the pinion angle command value PATG, and G is the coefficient (gain).

[0063] The steering control device 200 controls the steering motor 100 in synchronous control so that the actual pinion angle RPA (actual steering amount) approaches the new pinion angle command value NPATG (new target steering amount). The value calculated at the previous calculation timing in the calculation processing at regular intervals is called the previous value, and the value calculated at the current calculation timing is called the current value (or current value). In other words, the previous value PATG(n-1) of the pinion angle command value PATG corresponds to the target steering amount in the first state before the steering wheel 500 is operated, and the current value PATG(n) of the pinion angle command value PATG corresponds to the target steering amount in the second state after the steering wheel 500 has been operated.

[0064] Furthermore, the target value generation unit 230 sets the initial value of the previous value NPAT(n-1) of the new pinion angle command value to the actual pinion angle RPA (actual steering amount) at the time of transition from normal control to synchronous control (in other words, when the deadlock state is released). In other words, when the steering wheel 500 changes from the first state to the second state for the first time after the synchronous control transition, the target value generation unit 230 sets the actual pinion angle RPA (actual steering amount) in the first state to the initial value of the previous value NPAT(n-1) used in Equation 2. Therefore, when the amount of operation of the steering wheel 500 changes for the first time after the deadlock state is released, the target value generation unit 230 sets the actual steering amount at the start of the change to the initial value of the previous value NPAT(n-1) used in Equation 2. In this embodiment, the predetermined timing is when the change of the steering wheel 500 from the first state to the second state occurs for the first time after the synchronous control transition and for the first time after the deadlock state is released.

[0065] In other words, the target value generation unit 230 uses the actual pinion angle RPA at the time of transition to synchronous control as the initial value of the new pinion angle command value NPATG, and updates the new pinion angle command value NPATG in accordance with the subsequent change in the amount of steering wheel 500 operation. Through this initial setting, the pinion angle can be gradually converged from the actual pinion angle RPA at the time of transition to synchronous control to a pinion angle synchronized with the amount of steering wheel 500 operation.

[0066] The following describes in detail each functional unit that performs the generation process of the new pinion angle command value NPATG by the target value generation unit 230. The command value change amount calculation unit 231 calculates the command value change amount (command value change amount = current value of pinion angle command value PATG PATG(n) - previous value of pinion angle command value PATG PATG(n-1)) by subtracting the previous value PATG(n-1) from the current value PATG(n) of the pinion angle command value PATG, which is based on the amount of operation of the steering wheel 500 and the steering gear ratio.

[0067] The above command value change corresponds to the difference between the target steering amount in the second state and the target steering amount in the first state when the steering wheel 500 changes from the first state to the second state. In other words, the above command value change corresponds to the target change in steering amount corresponding to the change in the amount of steering wheel 500 is operated.

[0068] The coefficient setting unit 232 is a functional unit that sets a coefficient G (gain) to be multiplied by the command value change amount calculated by the command value change amount calculation unit 231. The coefficient G is set to different values ​​depending on whether the driver is turning the steering wheel 500 in or out. Here, when the operation of the steering wheel 500 is an out-of-bounds operation, the coefficient setting unit 232 sets the coefficient G to a smaller value than when it is an in-bound operation.

[0069] Furthermore, the coefficient setting unit 232 can variably set the coefficient G for the reverse operation and the coefficient G for the turn-in operation according to the vehicle speed and / or the operating speed of the steering wheel 500, while satisfying the relationship "coefficient G for reverse operation < coefficient G for turn-in operation". Figure 6 illustrates the characteristics of a map that stores the coefficient G for the turn-in operation according to the vehicle speed, and Figure 7 illustrates the characteristics of a map that stores the coefficient G for the reverse operation according to the vehicle speed. As shown in Figures 6 and 7, the coefficient G for the turn-in operation and the coefficient G for the reverse operation are set to larger values ​​as the vehicle speed increases, and are set so that "coefficient G for reverse operation < coefficient G for turn-in operation" is satisfied under all vehicle speed conditions.

[0070] The coefficient setting unit 232 refers to these maps to find the coefficient G for the steering wheel turning operation and the coefficient G for the steering wheel returning operation that correspond to the vehicle speed at that time. The coefficient setting unit 232 then acquires the judgment signal for steering wheel returning operation and steering wheel turning operation from the control state determination unit 220, and if the steering wheel 500 is turned in, it selects and outputs the coefficient G for the steering wheel turning operation, and if the steering wheel 500 is turned in, it selects and outputs the coefficient G for the steering wheel returning operation.

[0071] Furthermore, when the coefficient setting unit 232 sets the coefficient G for the unscrew operation and the coefficient G for the cut-in operation variably according to the absolute value of the operating speed of the steering wheel 500, it sets the coefficient G for the cut-in operation and the coefficient G for the unscrew operation to be larger the faster the operating speed of the steering wheel 500 is, and sets them so that the condition "coefficient G for unscrew operation < coefficient G for cut-in operation" is satisfied at any operating speed.

[0072] Furthermore, the coefficient setting unit 232 can set the coefficient G during the steering wheel turning operation and the coefficient G during the steering wheel unturning operation to be larger as the vehicle speed increases, and also larger as the operating speed of the steering wheel 500 increases. For example, the coefficient setting unit 232 can output the larger of the coefficient G set based on the vehicle speed and the coefficient G set based on the operating speed of the steering wheel 500 as the final coefficient G.

[0073] The multiplication unit 233 multiplies the command value change amount (command value change amount = current value of pinion angle command value PATG(n) - previous value of pinion angle command value PATG(n-1)) obtained by the command value change amount calculation unit 231 by the coefficient G set by the coefficient setting unit 232 and outputs the result. The new pinion angle command value calculation unit 234 adds the result of the multiplication by the multiplication unit 233, "(current value of pinion angle command value PATG(n) - previous value of pinion angle command value PATG(n-1)) × coefficient G", to the previous value of the new pinion angle command value NPATG(n-1) set by the new command previous value setting unit 235, and outputs the new pinion angle command value NPATG(n). In other words, the new pinion angle command value calculation unit 234 calculates the new pinion angle command value NPATG(n) according to the formula 2 described above, as follows: "New pinion angle command value NPATG(n) = Previous new pinion angle command value NPATG(n-1) + (Current pinion angle command value PATG(n) - Previous pinion angle command value PATG(n-1)) × coefficient G".

[0074] Here, when the deadlock state is released, the new command previous value setting unit 235 sets the previous value of the new pinion angle command value NPATG(n-1) to the actual pinion angle RPA at the time of release, and thereafter outputs the previously determined new pinion angle command value NPATG(n) as the previous value NPATG(n-1) in the new pinion angle command value calculation unit 234. Therefore, the new pinion angle command value NPATG(n) is updated in the direction of change of the pinion angle command value PATG according to the change in the pinion angle command value PATG (in other words, the change in the amount of operation of the steering wheel 500), with the actual pinion angle RPA at the time of release from the deadlock state as the initial value, and the update gain of the new pinion angle command value NPATG(n) in response to the change in the pinion angle command value PATG is switched according to whether the operation of the steering wheel 500 is a return operation or a turn-in operation.

[0075] As a result, if the driver does not operate the steering wheel 500 and the amount of operation of the steering wheel 500 is constant, the steering amount (tire angle) of the front wheels 2L and 2R will not change, even if there is a predetermined difference between the pinion angle command value PATG and the actual pinion angle RPA. Furthermore, regardless of whether the steering direction to bring the actual pinion angle RPA closer to the pinion angle command value PATG is to the left or to the right, if the driver operates the steering wheel 500 to the right, the steering amount of the front wheels 2L and 2R will change to the right, and if the driver operates the steering wheel 500 to the left, the steering amount of the front wheels 2L and 2R will change to the left. Therefore, due to synchronous control, the steering amount of the front wheels 2L and 2R will not change when the driver is not operating the steering wheel 500, nor will the steering amount of the front wheels 2L and 2R change in the opposite direction to the direction of the driver's operation of the steering wheel 500, thus preventing vehicle behavior that disregards the driver's steering intentions.

[0076] On the other hand, by switching the update gain of the new pinion angle command value NPATG(n) in response to a change in the pinion angle command value PATG (in other words, the gain of the target change in steering amount in response to a change in the amount of operation) depending on whether it is a counter-turn or a turn-in operation, the actual pinion angle RPA (actual steering amount) gradually approaches the pinion angle command value PATG (target steering amount) corresponding to the amount of operation of the steering wheel 500 while the driver is operating the steering wheel 500 left and right, and the difference between the pinion angle command value PATG and the actual pinion angle RPA is eliminated (see Figure 5). Furthermore, by increasing the update gain of the new pinion angle command value NPATG(n) in response to a change in the pinion angle command value PATG as the vehicle speed increases and / or as the operating speed of the steering wheel 500 increases, the difference between the pinion angle command value PATG and the actual pinion angle RPA can be converged as quickly as possible while suppressing any discomfort to the driver.

[0077] Figure 8 illustrates the changes in the actual pinion angle RPA and the pinion angle command value PATG when there is a predetermined difference between the pinion angle command value PATG and the actual pinion angle RPA after releasing from a deadlock state. The symbols (1)-(7) appended to each state in Figure 8 correspond to the timings (1)-(7) in Figure 5, illustrating the state changes when synchronous control is performed to determine the new pinion angle command value NPATG according to the formula 2 described above.

[0078] State (2), which is released from the deadlock state, is a state in which the pinion angle command value PATG, based on the amount of steering wheel 500 operation and the steering gear ratio, is 0 degrees (neutral position), and the actual pinion angle RPA is rotated 55 degrees to the left from the neutral position, and a predetermined amount of difference occurs between the pinion angle command value PATG and the actual pinion angle RPA. If feedback control is implemented from state (2) to bring the actual pinion angle RPA closer to the pinion angle command value PATG, that is, if the actual pinion angle RPA is changed from 55 degrees to 0 degrees, a steering noise (squeal) will be generated due to the sudden change in tire angle, and if the driver operates the steering wheel 500 to the left while steering, the actual pinion angle RPA will change in the opposite direction to the direction of the driver's operation of the steering wheel 500.

[0079] On the other hand, in synchronous control based on the new pinion angle command value NPATG(n) obtained by the aforementioned formula 2, when the driver operates the steering wheel 500 to the left, during the change from state (3) to state (4) and from state (5) to state (6), even when it is necessary to change the steering amount of the front wheels 2L and 2R to the right for synchronization, when the driver operates the steering wheel 500 to the left (when the driver performs a counter-turn operation), the steering amount of the front wheels 2L and 2R is changed to the left in response to this operation. Conversely, when the driver operates the steering wheel 500 to the right (when the driver performs a turn-in operation) during the change from state (4) to state (5) and from state (6) to state (7), the synchronous control based on the new pinion angle command value NPATG(n) changes the steering amount of the front wheels 2L and 2R to the right in the same direction as the synchronization.

[0080] Here, the gain of the steering amount change during the steering input operation is made greater than the gain of the steering amount change during the counter-steering operation. As a result, while the driver repeatedly performs left and right steering operations, the difference between the actual pinion angle RPA and the pinion angle command value PATG gradually decreases, and eventually, the actual pinion angle RPA and the pinion angle command value PATG come to match. Therefore, steering noise associated with synchronous control can be suppressed, and since the steering amount of the front wheels 2L and 2R is changed in the direction of the driver's operation of the steering wheel 500, vehicle behavior that disregards the driver's steering intentions can be suppressed.

[0081] Figure 9 is a flowchart showing the control procedure performed by the control device 1100 when the front wheels 2L and 2R hit an obstacle such as a curb and steering becomes impossible, and more specifically, the control procedure including reaction force torque increase control, steering torque limit control, and synchronization control. In step 11, the control device 1100 performs steering control to match the actual pinion angle RPA (actual steering amount) to the pinion angle command value PATG (target steering amount) based on the amount of steering wheel 500 manipulated and the steering gear ratio, and controls the upper limits of the reaction force torque and steering torque to values ​​that are appropriate for a state that is not deadlocked.

[0082] Next, in step S12, the control device 1100 detects state quantities such as steering torque and actual pinion angular velocity to determine whether the front wheels 2L and 2R are in a state where they are unable to steer because they have hit an obstacle such as a curb, or a state where they can steer normally without hitting an obstacle such as a curb. Then, in step S13, the control device 1100 determines whether or not the front wheels 2L and 2R have hit an obstacle (i.e., whether or not there has been a collision).

[0083] Here, if the control device 1100 determines in step S13 that the front wheels 2L and 2R have not hit an obstacle and that steering of the front wheels 2L and 2R is normally possible, it returns to the normal control state in step S11. On the other hand, if the control device 1100 determines in step S13 that the front wheels 2L and 2R have hit an obstacle and cannot be steered, it proceeds to step S14 and executes steering control at the time of impact (curb detection control), which includes control to limit the steering torque to a smaller value than in the normally steerable state, and control to increase the reaction torque to a larger value than in the normally steerable state.

[0084] Next, in step S15, the control device 1100 detects state quantities such as the actual pinion angular velocity ΔRPA and the steering torque command value in order to determine whether the front wheels 2L and 2R have released the state in which they were hitting the obstacle and are now in a state where they can be steered normally. Then, in step S16, the control device 1100 determines whether the front wheels 2L and 2R have released the state in which they were hitting the obstacle.

[0085] If the front wheels 2L and 2R remain in contact with an obstacle, the control device 1100 continues the steering control during contact in step S14 (limiting the increase in steering torque and controlling the increase in reaction torque). On the other hand, if the front wheels 2L and 2R are released from contact with an obstacle and normal steering of the front wheels 2L and 2R becomes possible, the control device 1100 determines in step S17 that the contact state has been released (the curb has been driven over).

[0086] Then, in the next step S18, the control device 1100 determines the difference (error amount in steering control) between the pinion angle command value PATG (target steering amount) and the actual pinion angle RPA (actual steering amount) at the time of departure from the deadlock state. Next, in step S19, the control device 1100 compares the difference obtained in step S18 with a threshold value to determine whether a predetermined amount of difference has occurred between the pinion angle command value PATG and the actual pinion angle RPA, that is, whether a difference of a magnitude exceeding the allowable amount has occurred between the pinion angle command value PATG and the actual pinion angle RPA.

[0087] Here, if the difference between the pinion angle command value PATG and the actual pinion angle RPA is within the acceptable range, the control device 1100 returns to step S11 and performs normal steering control to match the actual pinion angle RPA to the pinion angle command value PATG. On the other hand, if the difference between the pinion angle command value PATG and the actual pinion angle RPA is large and exceeds the acceptable range, the control device 1100 proceeds to step S20 and transitions to a synchronous mode in which the difference between the pinion angle command value PATG and the actual pinion angle RPA is converged by performing steering control based on the new pinion angle command value NPATG obtained according to the formula 2 described above.

[0088] When the control device 1100 transitions to synchronous mode, in step S21 it acquires information such as vehicle speed (wheel speed) in order to determine whether the vehicle 1 is moving or stationary. Then, in the next step S22, the control device 1100 determines whether the vehicle 1 is moving or not based on the vehicle speed (wheel speed) information.

[0089] If vehicle 1 is in motion, in step S23, the control device 1100 determines the amount of change per unit time of the steering wheel 500's operation (operation position, operation angle) in order to detect whether or not the driver is operating the steering wheel 500. Next, in step S24, the control device 1100 determines whether or not the driver is operating the steering wheel 500, that is, whether or not the amount of operation of the steering wheel 500 is changing, based on a comparison of the amount of change in the steering wheel 500's operation with a threshold.

[0090] If the driver is operating the steering wheel 500, the control device 1100 proceeds to step S28 and beyond, and performs synchronous control of the steering motor 100 based on the new pinion angle command value NPATG obtained according to the formula 2 described above. On the other hand, if the driver is not operating the steering wheel 500, the control device 1100 proceeds to step S27, and performs synchronous control other than synchronous control according to the new pinion angle command value NPATG based on formula 2.

[0091] Furthermore, if vehicle 1 is stationary and not in motion, the control device 1100 proceeds to step S25 to determine whether the difference between the pinion angle command value PATG and the actual pinion angle RPA is in phase or out of phase, by determining the sign of the pinion angle command value PATG and the actual pinion angle RPA, and the amount of the gap between them. In-phase displacement means that both the pinion angle command value PATG and the actual pinion angle RPA are located to the left or right of the neutral position, and that they are separated by a predetermined amount or more. Out of phase displacement means that the side where the pinion angle command value PATG is located and the side where the actual pinion angle RPA is located are on opposite sides of the neutral position, and that they are separated by a predetermined amount or more.

[0092] Then, in step S26, the control device 1100 determines whether the difference between the pinion angle command value PATG and the actual pinion angle RPA is in phase or not, and if it is out of phase, proceeds to step S27. In step S27, the control device 1100 performs synchronous control other than synchronous control according to the new pinion angle command value NPATG based on formula 2.

[0093] On the other hand, if vehicle 1 is stationary and the difference between the pinion angle command value PATG and the actual pinion angle RPA is in phase, the control device 1100 proceeds to step S28 and beyond and performs synchronous control of the steering motor 100 based on the new pinion angle command value NPATG. In the synchronous control based on the new pinion angle command value NPATG, the control device 1100 first detects in step S28 whether the steering wheel 500 has been turned in or turned out.

[0094] The control device 1100 (control state determination unit 220) determines whether the steering wheel 500 has been turned in or out of position based on the pinion angular velocity command value ΔPATG, the pinion angle command value PATG, and the actual pinion angle RPA, as described above. Then, in the next step S29, the control device 1100 determines whether the driver has turned the steering wheel 500 in or out.

[0095] Here, if the driver is turning the steering wheel 500 inwards, the control device 1100, in step S30, calculates a new pinion angle command value NPATG based on formula 2, which is set to a value that the coefficient G applies to the turning operation, and compares the new pinion angle command value NPATG with the actual pinion angle RPA to perform synchronous control to control the steering motor 100, that is, synchronous control in the turning operation state. Also, if the driver is turning the steering wheel 500 back out, the control device 1100, in step S31, calculates a new pinion angle command value NPATG based on formula 2, which is set to a value that the coefficient G applies to the back out operation, and compares the new pinion angle command value NPATG with the actual pinion angle RPA to perform synchronous control to control the steering motor 100, that is, synchronous control in the back out operation state.

[0096] In step S30 or step S31, the control device 1100 performs synchronous control to control the steering motor 100 according to the new pinion angle command value NPATG, and then proceeds to step S32 to detect a change in the difference between the pinion angle command value PATG and the actual pinion angle RPA. Next, in step S33, the control device 1100 determines whether there is still a predetermined amount of difference between the pinion angle command value PATG and the actual pinion angle RPA, or whether the difference has been eliminated and the pinion angle command value PATG and the actual pinion angle RPA are in a state of near-perfect agreement.

[0097] If there is still a predetermined difference between the pinion angle command value PATG and the actual pinion angle RPA, the control device 1100 returns to step S20 and continues the synchronous mode (in other words, synchronous control that controls the steering motor 100 based on the new pinion angle command value NPATG). On the other hand, if the difference between the pinion angle command value PATG and the actual pinion angle RPA is eliminated and the pinion angle command value PATG and the actual pinion angle RPA are in a state of approximately agreement, the control device 1100 returns to step S11 and transitions from the synchronous mode (synchronous control state) to the normal mode (normal control state).

[0098] Thus, when the front wheels 2L and 2R hit an obstacle such as a curb and become unable to steer, the control device 1100 limits the increase in steering torque, thereby preventing excessive steering torque from being continuously applied and damaging the steering system 1000 or the vehicle 1. It also increases the reaction torque to make the driver aware of the unsteerable state. Furthermore, when the front wheels 2L and 2R release the obstacle and become able to steer, if there is a predetermined difference between the pinion angle command value PATG and the actual pinion angle RPA, the control device 1100 will gradually synchronize the direction of the front wheels 2L and 2R with the position of the steering wheel 500 as the driver operates the steering wheel 500, without ignoring the driver's steering intention, thus improving the safety of the steering system 1000.

[0099] The technical ideas described in the above embodiments can be used in appropriate combinations, provided that no contradictions arise. Furthermore, although the content of the present invention has been specifically described with reference to preferred embodiments, it will be obvious to those skilled in the art that various modifications can be taken based on the basic technical ideas and teachings of the present invention.

[0100] For example, the control device 1100 (steering control device 200) makes the coefficient G used in formula 2 for determining the new pinion angle command value NPATG variable depending on whether it is an in-turn operation or a re-turn operation, and the larger the difference between the pinion angle command value PATG and the actual pinion angle RPA, the larger the difference between the coefficient G used in the in-turn operation and the coefficient G used in the re-turn operation. Here, the process of increasing the difference between the coefficient G used in the in-turn operation and the coefficient G used in the re-turn operation includes at least one of the following: a process of increasing the coefficient G in the in-turn operation as the difference between the pinion angle command value PATG and the actual pinion angle RPA is larger, and a process of decreasing the coefficient G in the re-turn operation as the difference between the pinion angle command value PATG and the actual pinion angle RPA is larger.

[0101] Furthermore, the control device 1100 (steering control device 200) controls the steering motor 100 based on the new pinion angle command value NPATG obtained by formula 2 when the difference between the pinion angle command value PATG and the actual pinion angle RPA is greater than a threshold, and controls the steering motor 100 based on the pinion angle command value PATG obtained based on the amount of steering wheel 500 operation and the steering gear ratio when the difference between the pinion angle command value PATG and the actual pinion angle RPA becomes smaller than a threshold.

[0102] Furthermore, when the vehicle 1 is stationary, the steering motor 100 is controlled based on the pinion angle command value PATG, which is determined based on the amount of steering wheel 500 operation and the steering gear ratio, thereby synchronizing the direction of the front wheels 2L and 2R with the position of the steering wheel 500. When the vehicle 1 starts moving and enters a driving state while the difference between the pinion angle command value PATG and the actual pinion angle RPA has not been resolved, the steering motor 100 is controlled based on the new pinion angle command value NPATG, which is determined by equation 2, thereby synchronizing the direction of the front wheels 2L and 2R with the position of the steering wheel 500.

[0103] Furthermore, the steering system 1000 is not limited to a system that performs synchronous control of the steering motor 100 based on the new pinion angle command value NPATG obtained by formula 2 when the steering error increases due to the front wheels 2L and 2R hitting an obstacle such as a curb. For example, when the steering wheel 500 and / or the front wheels 2L and 2R are moved while the steering system 1000 is stopped, causing a large steering error, the system can be configured to perform synchronous control of the steering motor 100 based on the new pinion angle command value NPATG obtained by formula 2 when the steering system 1000 is started.

[0104] Furthermore, although the control device 1100 is composed of a steering control device 200 and a steering input control device 700, which are provided separately, a single electronic control device can be a steering system that combines the control function of a steering control device 200 and the control function of a steering input control device 700. In this case, the single electronic control device described above corresponds to the steering control device according to the present invention. Moreover, the system may be any of the following: a system in which the single electronic control device described above is arranged integrally with the steering device 2000, a system in which the single electronic control device described above is arranged integrally with the steering operation input device 3000, or a system in which the single electronic control device described above is arranged separately from the steering device 2000 and the steering operation input device 3000.

[0105] 1...Vehicle, 2L, 2R...Front wheel (wheel), 100...Steering motor (steering actuator), 200...Steering control device, 400...Steering amount sensor, 500...Steering wheel (steering input component), 600...Reaction motor (reaction actuator), 700...Steering input control device, 800...Operation amount sensor, 1000...Steering system, 1100...Control device, 2000...Steering device, 3000...Steering operation input device

Claims

1. A steering system comprising: a steering input device having a reaction actuator that detects the amount of operation of a steering input member of a vehicle and applies a reaction torque to the steering input member; a steering device that is mechanically separated from the steering input device and arranged in the vehicle, and has a steering actuator that detects the amount of steering of the vehicle's wheels and applies steering torque to the wheels; and a control device that outputs a drive signal corresponding to the amount of operation to the reaction actuator and the steering actuator, wherein the control device acquires the amount of operation from the steering input device and determines a target steering amount corresponding to the amount of operation, acquires the steering amount from the steering device, and when there is a predetermined difference between the target steering amount and the steering amount, and the steering input member changes from a first state to a second state, the control device determines the target steering amount in the first state, the difference between the target steering amount in the second state and the target steering amount in the first state, and a coefficient based on information as to whether the change from the first state to the second state is a change that moves away from the steering amount, A steering system that, based on the above, acquires a new target steering amount and outputs a drive signal corresponding to the new target steering amount to the steering actuator.

2. A steering system according to claim 1, wherein the control device sets the steering amount to the target steering amount in the first state when there is a predetermined difference between the target steering amount and the steering amount, and a change from the first state to the second state of the steering input member occurs at a predetermined time.

3. A steering system according to claim 1, wherein the control device sets the coefficient to a larger value as the vehicle speed increases or as the operating speed of the steering input member increases.

4. A steering system according to claim 1, wherein the control device reduces the coefficient when the change of the steering input member from the first state to the second state is a change that approaches the steering amount, compared to when the change is a change that moves away from the steering amount.

5. The steering system according to claim 1, wherein the control device is such that the first state is the state before the steering input member is operated, and the second state is the state after the steering input member in the first state has been operated.

6. A steering system according to claim 1, wherein the control device determines whether the steering device is in a deadlock state based on the rate of change of the steering amount, the torque command value of the steering actuator, and the vehicle speed of the vehicle, and when the steering device is released from the deadlock state, if there is a predetermined difference between the target steering amount and the steering amount, it outputs a drive signal corresponding to the new target steering amount to the steering actuator.

7. A steering system according to claim 6, wherein the steering device is determined to be in a deadlock state when the rate of change of the steering amount is less than a predetermined rate of change, the torque command value of the steering actuator is greater than or equal to a predetermined torque, and the vehicle speed is less than a predetermined speed; and the steering device is determined to have been released from a deadlock state when any of the following conditions are met: the rate of change of the steering amount is greater than or equal to the predetermined rate of change, the torque command value of the steering actuator is less than the predetermined torque, and the vehicle speed is greater than or equal to the predetermined speed.

8. A steering system according to claim 6, wherein the control device lowers the upper limit of the steering torque when the steering device is in a deadlock state compared to when the steering device is not in a deadlock state, and increases the reaction torque compared to when the steering device is not in a deadlock state.

9. A steering system according to claim 8, wherein the control device cancels the increase in reaction torque when the rate of change of the steering amount becomes greater than or equal to a predetermined rate of change, or when the steering device disengages from a deadlock state and the difference between the target steering amount and the steering amount is less than a predetermined value.

10. A steering system according to claim 8, wherein the control device gradually restores the upper limit of the steering torque and the reaction torque over time when canceling the reduction of the upper limit of the steering torque and the increase of the reaction torque.

11. A steering control device mounted on a vehicle comprising: a steering operation input device having a reaction actuator that detects the amount of operation of a steering input member of a vehicle and applies a reaction torque to the steering input member; and a steering device that is mechanically separated from the steering operation input device and arranged in the vehicle, and has a steering actuator that detects the amount of steering of the vehicle's wheels and applies steering torque to the wheels, and outputs a drive signal to the steering actuator according to the amount of operation, wherein the steering control device obtains the amount of operation from the steering operation input device and determines a target steering amount according to the amount of operation, obtains the steering amount from the steering device, and when there is a predetermined difference between the target steering amount and the steering amount, and the steering input member changes from a first state to a second state, obtains a new target steering amount based on the target steering amount in the first state, the difference between the target steering amount in the second state and the target steering amount in the first state, and a coefficient based on information as to whether the change from the first state to the second state is a change away from the steering amount, A steering control device that outputs a drive signal corresponding to the new target steering amount to the steering actuator.

12. A steering control method executed by a control device mounted on a vehicle, comprising: a steering operation input device having a reaction actuator that detects the amount of operation of a steering input member of a vehicle and applies a reaction torque to the steering input member; and a steering device that is mechanically separated from the steering operation input device and arranged on the vehicle, and has a steering actuator that detects the amount of steering of the vehicle's wheels and applies steering torque to the wheels, wherein the control device obtains the amount of operation from the steering operation input device and determines a target steering amount corresponding to the amount of operation; obtains the steering amount from the steering device, and when there is a predetermined difference between the target steering amount and the steering amount, and the steering input member changes from a first state to a second state, obtains a new target steering amount based on the target steering amount in the first state, the difference between the target steering amount in the second state and the target steering amount in the first state, and a coefficient based on information as to whether the change from the first state to the second state is a change away from the steering amount; A steering control method that outputs a drive signal corresponding to the new target steering amount to the steering actuator.

13. A steering control device mounted on a vehicle comprising: a steering operation input device having a reaction actuator that detects the amount of operation of a steering input member of a vehicle and applies a reaction torque to the steering input member; and a steering device that is mechanically separated from the steering operation input device and arranged in the vehicle, and has a steering actuator that detects the amount of steering of the vehicle's wheels and applies steering torque to the wheels, wherein the steering control device outputs a drive signal corresponding to the amount of operation to the steering actuator to control the amount of steering, wherein, when there is a predetermined difference between a target amount of steering corresponding to the amount of operation and the amount of steering, the steering control device determines a target change in the amount of steering according to the change in the amount of operation of the steering input member, changes the amount of steering by the target change in a direction that coincides with the direction of operation of the steering input member, and makes the gain of the target change in the amount of steering with respect to the change in the amount of operation smaller when the operation of the steering input member is an operation that approaches the amount of steering than when the operation is an operation that moves away from the amount of steering.

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