Steering control device and steering control method

Abstract

To provide a steering control device and a steering control method that prevent behavior of a vehicle from being unstable.SOLUTION: A steering control device controls a steer-by-wire vehicle steering device configured to be able to change a gear ratio VG. The gear ratio VG is adopted in advance to stabilize the behavior of a vehicle based on its state. A turning unit of the steering device includes a turning motor that generates turning force for turning steering wheels of the vehicle. The steering control device is configured to execute a turning control process executed by a turning control unit. The turning control process includes a process executed by a steering angle ratio variable control unit 71 that changes the gear ratio VG based on a vehicle state signal, and is a process for controlling the operation of the turning motor to apply the turning force to the steering wheels. The steering angle ratio variable control unit 71 includes a process for when an event condition is met, temporarily correcting the gear ratio VG regardless of adaptation so as to stabilize the behavior of the vehicle.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a steering control device and a steering control method.

Background Art

[0002] Conventionally, among steering devices mounted on vehicles, there is a steer-by-wire type steering device. For example, as described in Patent Document 1, a steering control device that controls such a steering device controls the steering angle of a tire using a target steering angle obtained by multiplying the steering angle of a steering wheel by a steering ratio gain. Here, the steering ratio gain is the ratio of the steering angle to the steering angle with respect to the steering angle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above steering ratio gain is pre-adjusted so that the behavior of the vehicle does not become unstable. However, when an event that makes the behavior of the vehicle unstable occurs, the steering ratio gain deviates from the pre-adjusted adaptation. This becomes a factor that makes the behavior of the vehicle unstable.

Means for Solving the Problems

[0005] The steering control device capable of solving the above problems controls the steering device of a vehicle. The steering device has a structure in which the power transmission path between a steering unit having a steering member and a steering unit configured to steer a steered wheel is separated, so that the positional relationship between the steering position of the steering member and the steering position of the steered wheel can be changed. The positional relationship is pre-adapted from the viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle. The steering unit includes a steering motor that generates a steering force for steering the steered wheel. The steering control device is configured to execute a steering control process. The steering control process includes a positional relationship change process of changing the positional relationship based on the state of the vehicle, and is a process for controlling the operation of the steering motor so as to apply the steering force to the steered wheel so that the steering position takes into account the positional relationship with respect to the steering position. The positional relationship change process includes a process of temporarily correcting the positional relationship regardless of the adaptation so that the behavior of the vehicle becomes stable when an event condition indicating that an event causing the behavior of the vehicle to become unstable has occurred is satisfied.

[0006] The above configuration is premised on the fact that the positional relationship between the steering position of the steering member and the steering position of the steered wheel is pre-adapted from the viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle. Under such a premise, when an event condition indicating that an event causing the behavior of the vehicle to become unstable has occurred is satisfied, the above positional relationship can be corrected regardless of the adaptation. By performing such correction of the positional relationship regardless of the adaptation, correction can be performed so that the behavior of the vehicle becomes stable. As a result, even if an event that makes the behavior of the vehicle unstable occurs, the behavior of the vehicle can be restored so as to become stable. Therefore, it becomes difficult for the behavior of the vehicle to become unstable.

[0007] In the above steering control device, it is preferable that the event condition includes that the vehicle is turning. According to the above configuration, assuming the event that the behavior of the vehicle becomes unstable is that the vehicle is in a turning operation, the behavior of the vehicle can be rectified so as to become stable. Therefore, when the vehicle is in a turning operation, it is difficult for the behavior of the vehicle to become unstable.

[0008] In the above steering control device, it is preferable that the event condition includes changing the yaw rate generated in the vehicle while the vehicle is in a turning operation. According to the above configuration, assuming the event that the behavior of the vehicle becomes unstable is that the yaw rate generated in the vehicle changes while the vehicle is in a turning operation, the behavior of the vehicle can be rectified so as to become stable. Therefore, when the yaw rate generated in the vehicle changes while the vehicle is in a turning operation, it is difficult for the behavior of the vehicle to become unstable.

[0009] In the above steering control device, it is preferable that the event condition includes changing the yaw rate generated in the vehicle unintentionally by the driver while the vehicle is in a turning operation.

[0010] According to the above configuration, assuming the event that the behavior of the vehicle becomes unstable is that the yaw rate generated in the vehicle changes unintentionally by the driver while the vehicle is in a turning operation, the behavior of the vehicle can be rectified so as to become stable. Therefore, when the yaw rate generated in the vehicle changes unintentionally by the driver while the vehicle is in a turning operation, it is difficult for the behavior of the vehicle to become unstable.

[0011] In the above-described steering control device, the position relationship change process includes a process of canceling a temporary correction of the position relationship when the event condition becomes non-established after the establishment of the event condition. The steering control process includes a target steering position calculation process of calculating a target steering position obtained by taking into account the position relationship based on the steering position, and a steering operation amount calculation process of calculating an operation amount for controlling the steering position to the target steering position by feedback processing. The target steering position calculation process includes an offset calculation process of calculating an offset component for reducing the absolute value of the difference in the target steering position before and after the temporary correction of the position relationship among the processes including the position relationship change process. The offset calculation process includes a release process of subtracting the offset component from the target steering position and adding a release component, which is at least a part of the offset component, to the target steering position. The release process is preferably a process that starts in accordance with the position relationship change process canceling the temporary correction of the position relationship.

[0012] According to the above configuration, the temporarily corrected position relationship has the influence of the correction eliminated by the release process after the cancellation of the temporary correction. Therefore, it is effective in suppressing a sudden change in the target steering position when the release component is reflected by the release process.

[0013] In the above-described steering control device, the release process preferably includes a process of making variable the addition amount of adding the release component to the target steering position. According to the above configuration, even if the release component is reflected, if the addition amount can be made variable, the change in the target steering position can be adjusted. This is effective in stabilizing the behavior of the vehicle while the release component is being reflected.

[0014] The steering control method capable of solving the above problems is a method for controlling a steering device of a vehicle configured to be able to change the positional relationship between a steering position of a steering member and a steering position of a steered wheel so as to have a position relationship preliminarily adapted from the viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle, by having a structure in which a power transmission path between a steering unit having a steering member of the vehicle and a steering unit including a steering motor that generates a steering force for steering the steered wheels of the vehicle is separated. The steering control method includes executing a steering control process, and the steering control process includes a process for changing the positional relationship based on the state of the vehicle. Among them, it is a process for controlling the operation of the steering motor so as to apply the steering force to the steered wheels so that the steering position becomes the steering position considering the positional relationship with respect to the steering position. The process for changing the positional relationship includes a process for temporarily correcting the positional relationship regardless of the adaptation so that the behavior of the vehicle becomes stable when an event condition indicating that an event in which the behavior of the vehicle becomes unstable has occurred is satisfied.

Effect of the Invention

[0015] According to the steering control device and the steering control method of the present invention, it is difficult for the behavior of the vehicle to become unstable.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0017] Hereinafter, a steering control device according to an embodiment will be described. As shown in FIG. 1, a vehicle steering system 2 includes a steering control device 1. The vehicle steering system 2 includes a steering unit 4 and a steering actuator unit 6. The steering unit 4 is steered by a driver via a steering wheel 3 of a vehicle which is a steering member. The steering actuator unit 6 operates to steer left and right steering wheels 5 of the vehicle in response to the steering input to the steering unit 4 by the driver. The vehicle steering system 2 of the present embodiment has, for example, a structure in which a power transmission path between the steering unit 4 and the steering actuator unit 6 is mechanically separated at all times. A power transmission path between a steering actuator 12 described later and a steering actuator 31 described later has a structure in which it is mechanically separated at all times. That is, the vehicle steering system 2 includes a steer-by-wire type steering device.

[0018] The steering unit 4 includes a steering shaft 11 and a steering actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering actuator 12 has a steering motor 13 and a steering side speed reduction mechanism 14. The steering motor 13 is a reaction force motor that applies a steering reaction force, which is a force resistant to steering, to the steering wheel 3 via the steering shaft 11. That is, the steering unit 4 is a reaction force unit. The steering motor 13 is connected to the steering shaft 11 via a steering side speed reduction mechanism 14 composed of, for example, a worm and a wheel. The steering motor 13 of the present embodiment employs, for example, a three-phase brushless motor.

[0019] The steering unit 6 has a pinion shaft 21, a rack shaft 22 as a steering shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected with a predetermined crossing angle. A rack and pinion mechanism 24 is configured by meshing a pinion tooth 21a formed on the pinion shaft 21 with a rack tooth 22a formed on the rack shaft 22. The pinion shaft 21 corresponds to a rotating shaft that can be converted into a steering angle θi which is the steering position of the steering wheel 5. The rack housing 23 houses the rack and pinion mechanism 24.

[0020] One end of the pinion shaft 21 on the side opposite to the side connected to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the rack shaft 22 via rack ends 25 each consisting of a ball joint. The tips of the tie rods 26 are respectively connected to knuckles (not shown) to which the left and right steering wheels 5 are assembled.

[0021] The steering unit 6 includes a steering actuator 31. The steering actuator 31 includes a steering motor 32, a transmission mechanism 33, and a conversion mechanism 34. The steering motor 32 applies a steering force for steering the steering wheel 5 to the rack shaft 22 via the transmission mechanism 33 and the conversion mechanism 34. The steering motor 32 transmits rotation to the conversion mechanism 34 via a transmission mechanism 33 consisting of, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering motor 32 into a reciprocating motion of the rack shaft 22 via a conversion mechanism 34 consisting of, for example, a ball screw mechanism. In the steering motor 32 of the present embodiment, for example, a three-phase brushless motor is adopted.

[0022] In the vehicle steering system 2, motor torque is applied as steering force from the steering actuator 31 to the rack shaft 22 in response to steering operation by the driver, thereby changing the steering angle θi of the steered wheels 5. At this time, a steering reaction force against the driver's steering is applied from the steering actuator 12 to the steering wheel 3. Thereby, in the vehicle steering system 2, the steering torque Th required for steering the steering wheel 3 is changed by the steering reaction force, which is the motor torque applied from the steering actuator 12.

[0023] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 inside the rack housing 23. By a support mechanism (not shown) provided in the vehicle steering system 2, the rack shaft 22 is supported so as to be movable along its axial direction and is pressed toward the pinion shaft 21. Thereby, the rack shaft 22 is supported inside the rack housing 23. However, another support mechanism for supporting the rack shaft 22 in the rack housing 23 without using the pinion shaft 21 may be provided.

[0024] <Electrical Configuration of Vehicle Steering System> As shown in FIG. 1, the steering motor 13 and the steering actuator motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of each motor 13, 32.

[0025] Detection results of various sensors are input to the steering control device 1. The various sensors include, for example, a torque sensor 41, a steering-side rotation angle sensor 42, a steered-side rotation angle sensor 43, and a vehicle speed sensor 44.

[0026] The torque sensor 41 is provided at a portion between the steering wheel 3 and the steering side reduction mechanism 14 on the steering shaft 11. The torque sensor 41 detects a steering torque Th which is a value indicating the torque applied to the steering shaft 11 by the driver's steering operation. The steering torque Th is detected in relation to the twist of a torsion bar 41a provided midway along the steering shaft 11 between the steering wheel 3 and the steering side reduction mechanism 14 on the steering shaft 11. The steering side rotation angle sensor 42 is provided on the steering motor 13. The steering side rotation angle sensor 42 detects a rotation angle θa which is the angle of the rotation shaft of the steering motor 13 within a range of 360 degrees. The steered side rotation angle sensor 43 is provided on the steering motor 32. The steered side rotation angle sensor 43 detects a rotation angle θb which is the angle of the rotation shaft of the steering motor 32 within a range of 360 degrees. The vehicle speed sensor 44 detects a vehicle speed V which is the traveling speed of the vehicle.

[0027] <Functions of the Steering Control Device> As shown in FIG. 2, the steering control device 1 includes a reaction force control unit 50 and a steering control unit 60. The reaction force control unit 50 executes control processing for controlling the steering wheel 3 which is a control target. The reaction force control unit 50 controls the drive of the steering actuator 12, more specifically the steering motor 13, in order to control the steering reaction force which is the control amount of the control target. The steering control unit 60 controls the drive of the steering actuator 31, more specifically the steering motor 32, in order to control the steering force which is the control amount of the control target. The reaction force control unit 50 and the steering control unit 60 mutually transmit and receive information via a local network such as serial communication. The reaction force control unit 50 constitutes a reaction force system RS in combination with the steering unit 4. The steering control unit 60 constitutes a steering system TS in combination with the steering unit 6.

[0028] The reaction force control unit 50 includes a central processing unit (hereinafter referred to as "CPU") and a memory. The reaction force control unit 50 executes various processes by the CPU executing a program stored in the memory at a predetermined operation cycle. The steering control unit 60 includes a central processing unit (hereinafter referred to as "CPU") and a memory. The steering control unit 60 executes various processes by the CPU executing a program stored in the memory at a predetermined operation cycle. The CPU and the memory constitute a microcomputer which is a processing circuit. The memory includes computer-readable media such as a RAM (Random Access Memory) and a ROM (Read Only Memory). However, the realization of various processes by software is just an example. The processing circuits of the reaction force control unit 50 and the steering control unit 60 may be configured to realize at least part of the processes by a hardware circuit such as a logic circuit.

[0029] FIG. 2 shows a part of the processes executed by the reaction force control unit 50 and the steering control unit 60. The processes shown in FIG. 2 describe a part of the processes realized by the CPU executing a program stored in the memory, classified by the types of the realized processes.

[0030] The reaction force control unit 50 has a current sensor 54. The current sensor 54 detects an actual current value Ia obtained from the current value of each phase of the steering motor 13 flowing through the connection line between the reaction force control unit 50 and the motor coil of each phase of the steering motor 13. The current sensor 54 acquires, as a current, the voltage drop of a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering motor 13. In FIG. 2, for convenience of explanation, the connection line of each phase and the current sensor of each phase are shown collectively as one.

[0031] The steering control unit 60 has a current sensor 65. The current sensor 65 detects an actual current value Ib obtained from the current value of each phase of the steering motor 32 flowing through the connection line between the steering control unit 60 and the motor coil of each phase of the steering motor 32. The current sensor 65 acquires, as a current, the voltage drop of a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering motor 32. In FIG. 2, for convenience of explanation, the connection line of each phase and the current sensor of each phase are collectively shown as one each.

[0032] <Regarding the reaction force control unit> As shown in FIG. 2, the reaction force control unit 50 controls the power supply to the steering motor 13 by inputting the steering torque Th, the vehicle speed V, and the rotation angle θa.

[0033] The reaction force control unit 50 includes a steering angle calculation unit 51, a steering reaction force command value calculation unit 52, and a power supply control unit 53. The steering angle calculation unit 51 calculates the steering angle θs by inputting the rotation angle θa. The steering angle calculation unit 51 converts the rotation angle θa into an integrated angle including a range exceeding 360° by, for example, counting the number of rotations of the steering motor 13 from the steering neutral position, which is the rotation position of the steering wheel 3 when the vehicle is going straight. The steering angle calculation unit 51 calculates the steering angle θs by multiplying the obtained integrated angle by a conversion coefficient based on the rotation speed ratio of the steering side reduction mechanism 14. That is, the steering angle θs is the steering position, which is the rotation position of the steering wheel 3. The thus obtained steering angle θs is output to the steering control unit 60.

[0034] The steering reaction force command value calculation unit 52 calculates a steering reaction force command value Ts* by inputting the steering torque Th and the vehicle speed V. The steering reaction force command value Ts* is a reaction force control amount that is the target of the steering reaction force of the steering wheel 3 to be generated through the steering motor 13. The thus obtained steering reaction force command value Ts* is used for the control in the power supply control unit 53.

[0035] The energization control unit 53 controls the energization to the steering motor 13 by executing current feedback processing for the actual current value Ia by inputting the steering reaction force command value Ts*, the rotation angle θa, and the actual current value Ia. As a result, the steering motor 13 generates torque corresponding to the steering reaction force command value Ts*. That is, it is possible to give the driver an appropriate feeling of feedback according to the road surface reaction force.

[0036] <Regarding the steering control unit> As shown in FIG. 2, the steering control unit 60 controls the power supply to the steering motor 32 by inputting the vehicle speed V, the steering angle θs, the rotation angle θb, and the vehicle state signal Sm. In the present embodiment, the process executed by the steering control unit 60 is an example of a steering control process.

[0037] The steering control unit 60 includes a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit (referred to as "pinion angle F / B control unit" in the figure) 63, and an energization control unit 64.

[0038] The pinion angle calculation unit 61 calculates the pinion angle θp by inputting the rotation angle θb. The pinion angle calculation unit 61 converts the rotation angle θb into an integrated angle including a range exceeding 360° by, for example, counting the number of rotations of the steering motor 32 from the rack neutral position, which is the position of the rack shaft 22 when the vehicle is going straight. The pinion angle calculation unit 61 multiplies the obtained integrated angle by a conversion coefficient based on the rotation speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack and pinion mechanism 24 to calculate the pinion angle θp, which is the actual rotation angle of the pinion shaft 21. The pinion angle θp thus obtained is used in the calculation by the pinion angle feedback control unit 63.

[0039] Note that the pinion angle θp is positive when it is at an angle, for example, on the right side rather than at the rack neutral position, and negative when it is at an angle on the left side. The steering motor 32 and the pinion shaft 21 are interlocked via a transmission mechanism 33, a conversion mechanism 34, and a rack shaft 22. Therefore, there is a correlation between the rotation angle θb of the steering motor 32 and the pinion angle θp. Using this correlation, the pinion angle θp can be obtained from the rotation angle θb of the steering motor 32. The pinion shaft 21 meshes with the rack shaft 22. Therefore, there is also a correlation between the pinion angle θp and the movement amount of the rack shaft 22. Accordingly, the pinion angle θp is a conversion angle that can be converted into the steering angle θi of the steering wheel 5, that is, the steering position.

[0040] The target pinion angle calculation unit 62 calculates a target pinion angle θp* by inputting a steering angle θs, a vehicle speed V, and a vehicle state signal Sm. The target pinion angle θp* is a steering control amount that is the target angle of the pinion angle θp obtained as a result of steering the steering wheel 5. The target pinion angle θp* thus obtained is used in the calculation by the pinion angle feedback control unit 63.

[0041] The vehicle state signal Sm is information indicating the state of the vehicle, and is information indicating that an event has occurred in which the behavior of the vehicle has become unstable. The vehicle state signal Sm includes, for example, information obtained from a yaw rate sensor, a camera, or a vehicle system other than the vehicle steering system 2 mounted on the vehicle. In the present embodiment, the event in which the behavior of the vehicle becomes unstable is an event that causes a change in the yaw rate generated in the vehicle, particularly when the vehicle is turning. When the yaw rate generated in the vehicle changes while the vehicle is turning, understeer or oversteer may occur in the vehicle, and the behavior of the vehicle may become unintended by the driver. Such a situation in which the behavior of the vehicle may become unintended by the driver may also occur in a situation where the vehicle performs so-called active steering control in which the vehicle intervenes in the steering of the steered wheels 5 for emergency avoidance or the like. The active steering control is control executed based on an instruction from a vehicle system other than the vehicle steering system 2 mounted on the vehicle. That is, the steering control unit 60 can determine whether or not it is a situation in which active steering control is executed by obtaining information from a vehicle system other than the vehicle steering system 2 mounted on the vehicle.

[0042] The target pinion angle calculation unit 62 calculates the target pinion angle θp* which is the target steering position by adding the adjustment amount θvg to the steering angle θs. The adjustment amount θvg is an operation amount for changing the steering angle ratio of the target pinion angle θp* with respect to the steering angle θs. The adjustment amount θvg is obtained by reflecting the gear ratio VG. For example, the gear ratio VG is a steering angle variable value obtained by subtracting "1" from a value indicating the relationship when the steering angle θs is the denominator and the target pinion angle θp* is the numerator. The value indicating the relationship when the steering angle θs is the denominator and the target pinion angle θp* is the numerator is an index indicating the ratio of the change amount of the target pinion angle θp* with respect to the change amount of the steering angle θs. Such an index is referred to as, for example, a transmission ratio, a steering angle ratio, etc., and defines the relationship between the steering angle θs and the pinion angle θp, that is, the relationship between the steering angle θs and the steering angle θi. That is, the gear ratio VG is a value indicating the difference with respect to the case where the steering angle θs and the target pinion angle θp* correspond 1:1. In the present embodiment, the process executed by the target pinion angle calculation unit 62 is an example of the target steering position calculation process.

[0043] The pinion angle feedback control unit 63 calculates the steering force command value Tp* by inputting the target pinion angle θp* and the pinion angle θp. The steering force command value Tp* is an operation amount that is the target of the steering force of the steering wheel 5 to be generated through the steering motor 32. The pinion angle feedback control unit 63 calculates the steering force command value Tp* by executing the feedback process of the pinion angle θp so that the pinion angle θp follows the target pinion angle θp*. The steering force command value Tp* thus obtained is used for the control in the energization control unit 64. In the present embodiment, the process executed by the pinion angle feedback control unit 63 is an example of the steering operation amount calculation process.

[0044] The energization control unit 64 controls the energization to the steering motor 32 by executing the current feedback process for the actual current value Ib by inputting the steering force command value Tp*, the rotation angle θb, and the actual current value Ib. As a result, the steering motor 32 generates a torque corresponding to the steering force command value Tp*. That is, it is possible to rotate the steering wheel 5 by an angle corresponding to the steering force.

[0045] <Regarding the target pinion angle calculation unit in the steering control unit> As shown in FIG. 3, the target pinion angle calculation unit 62 includes a steering angle ratio variable control unit 71, an offset component calculation processing unit 72, and an offset reflection processing unit 73.

[0046] <Regarding the steering angle ratio variable control unit> The steering angle ratio variable control unit 71 receives the steering angle θs, the vehicle speed V, and the vehicle state signal Sm. The steering angle ratio variable control unit 71 calculates the target pinion angle θp1* based on the steering angle θs, the vehicle speed V, and the vehicle state signal Sm. In the present embodiment, the process executed by the steering angle ratio variable control unit 71 is an example of the position relationship change process.

[0047] More specifically, the steering angle ratio variable control unit 71 includes a process of calculating the gear ratio VG with the steering angle θs and the vehicle speed V as inputs based on the steering angle θs and the vehicle speed V. Further, the steering angle ratio variable control unit 71 includes a process of calculating the adjustment amount θvg by multiplying the steering angle θs by the gear ratio VG. Then, the steering angle ratio variable control unit 71 calculates the target pinion angle θp1* by adding the adjustment amount θvg to the steering angle θs. The target pinion angle θp1* thus obtained is used in the calculations by the offset component calculation processing unit 72 and the offset reflection processing unit 73.

[0048] The steering angle ratio variable control unit 71 maps and calculates the gear ratio VG by the CPU using, for example, a gear ratio map which is map data stored in advance in the memory of the steering control unit 60. In the gear ratio map, the gear ratio VG is pre-adjusted from the viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle according to the steering angle θs and the vehicle speed V. That is, if the gear ratio VG deviates from the pre-adjustment, it becomes a factor for the behavior of the vehicle to become unstable. For example, the gear ratio VG is set such that the value becomes smaller as the steering angle θs increases and the value becomes smaller as the vehicle speed V increases. Note that the gear ratio VG is a positive value including "0". The gear ratio map is data having the steering angle θs and the vehicle speed V as input variables and the gear ratio VG as an output variable.

[0049] Note that the map data is paired data of discrete values of input variables and values of output variables corresponding to the respective values of the input variables. Also, the map operation may be a process in which, when the value of the input variable matches any of the values of the input variables of the map data, the value of the output variable of the corresponding map data is used as the operation result. Further, the map operation may be a process in which, when the value of the input variable does not match any of the values of the input variables of the map data, the value obtained by interpolation of the values of a plurality of output variables included in the map data is used as the operation result. Alternatively, the map operation may be a process in which, when the value of the input variable does not match any of the values of the input variables of the map data, the value of the output variable of the map data corresponding to the closest value among the values of a plurality of output variables included in the map data is used as the operation result.

[0050] Also, the steering angle ratio variable control unit 71 includes a condition determination process for determining whether or not an event condition is satisfied. The condition determination process is a process of determining, based on the vehicle state signal Sm, whether or not the vehicle state signal Sm indicates that an event in which the behavior of the vehicle becomes unstable has occurred. When the vehicle state signal Sm indicates that an event in which the behavior of the vehicle becomes unstable has occurred, the steering angle ratio variable control unit 71 determines that the event condition is satisfied. On the other hand, when the vehicle state signal Sm indicates that an event in which the behavior of the vehicle becomes unstable has not occurred, the steering angle ratio variable control unit 71 determines that the event condition is not satisfied.

[0051] Then, when the event condition is satisfied, the steering angle ratio variable control unit 71 includes a process of correcting the gear ratio VG. Correcting the gear ratio VG means calculating the gear ratio VG regardless of the conformity of the steering angle θs and the vehicle speed V at that time.

[0052] The gear ratio VG becomes a state where the reaction of the steering wheel 5 to the steering operation is sensitive, i.e., a so-called quick state, as the change in the target pinion angle θp* with respect to the change in the steering angle θs becomes larger. On the other hand, the gear ratio VG becomes a state where the reaction of the steering wheel 5 to the steering operation is dull, i.e., a so-called slow state, as the change in the target pinion angle θp* with respect to the change in the steering angle θs becomes smaller. That is, in the quick state, the range in which the steering wheel 5 can be steered with respect to the left and right steering operations is larger than in the slow state. And, for example, when the vehicle is turning and the steering operation is performed, an event occurs in which the yaw rate generated in the vehicle changes. In this case, if it is in the quick state, when the steering operation is performed, excessive understeer or oversteer is likely to occur in the vehicle. This indicates that the gear ratio VG becomes a factor deviating from the pre-conformed state. On the other hand, if it is in the slow state, even when the steering operation is performed, excessive understeer or oversteer is less likely to occur in the vehicle. This indicates that the gear ratio VG can maintain the pre-conformed state.

[0053] Therefore, when the event condition is satisfied, the steering angle ratio variable control unit 71 calculates the gear ratio VG obtained by correcting the gear ratio adapted to the steering angle θs and the vehicle speed V at that time so as to be in the slow state. The steering angle ratio variable control unit 71 calculates the temporarily corrected gear ratio VG while the event condition is satisfied. Then, when the event condition is no longer satisfied, the steering angle ratio variable control unit 71 cancels the correction of the gear ratio VG.

[0054] Note that when the event condition is not satisfied, the steering angle ratio variable control unit 71 does not correct the gear ratio VG. Not correcting the gear ratio VG means calculating the gear ratio VG adapted to the steering angle θs and the vehicle speed V at that time. This is because when the event condition is not satisfied, the possibility that the gear ratio VG deviates from the pre-conformed state is low.

[0055] Further, the steering angle ratio variable control unit 71 includes a process of calculating a steering end position θend based on the vehicle speed V. The steering end position θend is the control limit value on the left and right sides with respect to the steering neutral position when changing the steering angle θs. For example, the steering end position θend is a positive or negative value according to the positive or negative of the steering angle θs. These left and right limit values are angles for defining the angle range in which the steering angle θs can change, and will determine the rotation range of the steering wheel 3. The steering end position θend changes according to the vehicle speed V such that, for example, when the vehicle speed V is low, the angle range in which it can change, that is, the rotation range of the steering wheel 3, is larger than when the vehicle speed is high. The thus obtained steering end position θend is used in the calculation by the reaction force control unit 50.

[0056] And when the event condition is satisfied, the steering angle ratio variable control unit 71 calculates a steering end position θend obtained by correcting the steering end position conforming to the vehicle speed V at that time so that the absolute value becomes smaller. The steering angle ratio variable control unit 71 calculates a temporarily corrected steering end position θend while the event condition is satisfied. Thereafter, when the event condition ceases to be satisfied, the steering angle ratio variable control unit 71 cancels the correction of the steering end position θend. That is, in the present embodiment, the steering angle ratio variable control unit 71 is configured to associate the correction of the gear ratio VG with the correction of the steering end position θend through the state of satisfaction of the event condition.

[0057] Note that, based on the steering end position θend, when the steering angle θs reaches the steering end position θend, the reaction force control unit 50 calculates a regulation reaction force Fr to regulate further steering operation to the side exceeding the steering end position θend. The regulation reaction force Fr is a force that resists the steering operation and is a component for rapidly increasing the steering reaction force. The thus calculated regulation reaction force Fr is reflected in the steering reaction force, that is, the steering reaction force command value Ts*.

[0058] <Regarding the offset component calculation processing unit> As shown in FIG. 3, the offset component calculation processing unit 72 receives the vehicle state signal Sm and the target pinion angle θp1*. The offset component calculation processing unit 72 calculates an offset basic component θftb based on the vehicle state signal Sm and the target pinion angle θp1*. The offset basic component θftb thus obtained is used in the calculation in the offset reflection processing unit 73. In the present embodiment, the processing executed by the offset component calculation processing unit 72 is an example of offset calculation processing.

[0059] More specifically, the offset component calculation processing unit 72 includes a switching determination process for determining whether the event condition has changed from non - establishment to establishment or from establishment to non - establishment. The switching determination process is a process for determining, based on the vehicle state signal Sm, that the event condition has changed from non - establishment to establishment and that the event condition has changed from establishment to non - establishment. The fact that the event condition has changed from non - establishment to establishment coincides with the timing when the steering angle ratio variable control unit 71 starts to temporarily correct the gear ratio VG. The fact that the event condition has changed from establishment to non - establishment coincides with the timing when the steering angle ratio variable control unit 71 cancels the temporary correction of the gear ratio VG.

[0060] Then, when the offset component calculation processing unit 72 determines that the event condition has changed from non - establishment to establishment, it includes a process of calculating and storing a target pinion angle θft0 before correction. The target pinion angle θft0 before correction is the target pinion angle θp1* obtained based on the steering angle θs and the vehicle speed V that match the gear ratio VG at the time when it is determined that the event condition has changed from non - establishment to establishment. Also, when the offset component calculation processing unit 72 determines that the event condition has changed from establishment to non - establishment, it includes a process of calculating an offset basic component θftb, which is the deviation between the target pinion angle θp1* at that time and the stored target pinion angle θft0 before correction. Here, the target pinion angle θp1* at that time is the target pinion angle θp1* obtained based on the corrected gear ratio VG. That is, after calculating and storing the target pinion angle θft0 before correction, the offset component calculation processing unit 72 includes a process of temporarily storing the target pinion angle θft0 before correction until it is determined that the event condition has changed from establishment to non - establishment.

[0061] <Regarding the offset reflection processing unit> The vehicle speed V, the target pinion angle θp1*, the offset basic component θftb, and the pinion angle θp are input to the offset reflection processing unit 73. The offset reflection processing unit 73 calculates the final target pinion angle θp* based on the vehicle speed V, the target pinion angle θp1*, the offset basic component θftb, and the pinion angle θp. In the present embodiment, the processing executed by the offset reflection processing unit 73 is an example of offset calculation processing. Further, in the present embodiment, the processing executed by the offset reflection processing unit 73 is an example of release processing.

[0062] More specifically, as shown in FIG. 4, the offset reflection processing unit 73 includes a release gain calculation unit 81, a release amount calculation unit 82, and a sign processing unit 83. Further, the offset reflection processing unit 73 includes a release gain reflection processing unit 84, a sign reflection processing unit 85, a release component calculation processing unit 86, a release component reflection processing unit 87, and a differentiator 88.

[0063] The vehicle speed V is input to the release gain calculation unit 81. The release gain calculation unit 81 calculates the release gain G based on the vehicle speed V. The release gain calculation unit 81 map-calculates the release gain G by the CPU using, for example, a release gain map which is map data stored in advance in the memory of the steering control unit 60. In the release gain map, the value of the release gain G is, for example, "0" when the vehicle speed V is "0". Further, the value of the release gain G non-linearly increases smoothly in response to an increase in the vehicle speed V when it is larger than, for example, "0". The release gain map is data having the vehicle speed V as an input variable and the release gain G as an output variable. The release gain G thus obtained is used in the calculation by the release gain reflection processing unit 84.

[0064] The release amount calculation unit 82 receives the pinion angular velocity ωp. The release amount calculation unit 82 calculates a release basic amount θd1 based on the pinion angular velocity ωp. The pinion angular velocity ωp is a differential value obtained by differentiating the pinion angle θp with a differentiator 88. The release amount calculation unit 82 maps and calculates the release basic amount θd1 by the CPU using, for example, a release amount map which is map data prestored in the memory of the steering control unit 60. In the release amount map, the value of the release basic amount θd1 is, for example, "0" when the absolute value of the pinion angular velocity ωp is "0". Also, when the value of the release basic amount θd1 is greater than, for example, "0", it smoothly and non-linearly increases in response to an increase in the absolute value of the pinion angular velocity ωp. The release amount map is data having the pinion angular velocity ωp as an input variable and the release basic amount θd1 as an output variable. The release basic amount θd1 thus obtained is used in the calculation by the release gain reflection processing unit 84.

[0065] The release gain reflection processing unit 84 receives the release gain G and the release basic amount θd1. The release gain reflection processing unit 84 calculates a release amount θd2 by multiplying the release basic amount θd1 by the release gain G. For example, the release gain reflection processing unit 84 is a multiplier. The release amount θd2 thus obtained is used in the calculation by the sign reflection processing unit 85.

[0066] The sign processing unit 83 receives the offset basic component θftb. The sign processing unit 83 calculates a sign Sin based on the offset basic component θftb. The sign processing unit 83 includes a process of calculating "+1" when the offset basic component θftb is a positive value. Also, the sign processing unit 83 includes a process of calculating "-1" when the offset basic component θftb is a negative value. The positive or negative of the value of the offset basic component θftb conforms to the positive or negative of the target pinion angle θp*, that is, the pinion angle θp. The sign Sin thus obtained is used in the calculation by the sign reflection processing unit 85.

[0067] The symbol reflection processing unit 85 receives the release amount θd2 and the symbol Sin. The symbol reflection processing unit 85 calculates the release component θd by multiplying the release amount θd2 by the symbol Sin. For example, the symbol reflection processing unit 85 is a multiplier. The release component θd thus obtained is used in the calculation by the release component calculation processing unit 86.

[0068] The release component calculation processing unit 86 receives the offset base component θftb and the release component θd. The release component calculation processing unit 86 calculates the offset component θft by subtracting the release component θd from the offset base component θftb. For example, the release component calculation processing unit 86 is a subtractor. The offset component θft thus obtained is used in the calculation by the release component reflection processing unit 87. As a result, the release component θd is added to the target pinion angle θp1* as the eye addition amount.

[0069] The release component reflection processing unit 87 receives the target pinion angle θp1* and the offset component θft. The release component reflection processing unit 87 calculates the final target pinion angle θp* by subtracting the offset component θft from the target pinion angle θp1*. For example, the release component reflection processing unit 87 is a subtractor. The final target pinion angle θp* thus obtained is reflected in the steering force command value Tp* through the pinion angle feedback control unit 63.

[0070] Note that the offset reflection processing unit 73 includes a process of setting the release base amount θd1 to "0" when the offset base component θftb is "0". Further, the offset reflection processing unit 73 includes a process of calculating the release amount θd2, which is the absolute value of the offset base component θftb, when the absolute value of the offset base component θftb is less than or equal to the release amount θd2.

[0071] In the present embodiment, the offset component θft is an example of an operation amount for reducing the absolute value of the difference in the target pinion angle θp* before and after the temporary correction of the gear ratio VG based on the establishment of the event condition.

[0072] <Operation of this Embodiment> The gear ratio VG is pre - adapted so that the behavior of the vehicle does not become unstable. However, when an event that makes the vehicle behavior unstable occurs, the gear ratio VG deviates from the pre - applied adaptation. This becomes a factor that makes the vehicle behavior unstable.

[0073] That is, it is assumed that the gear ratio VG has been pre - adapted so that the behavior of the vehicle does not become unstable. Under such a premise, when the event condition is satisfied, the gear ratio VG can be corrected regardless of the adaptation.

[0074] Therefore, when the event condition is satisfied, the steering angle ratio variable control unit 71 performs a process including correcting the gear ratio VG. The correction of the gear ratio VG aims to correct the gear ratio VG so that it becomes a slow state with respect to the steering angle θs and the vehicle speed V at that time.

[0075] For example, FIG. 5 shows the frequency response characteristics of the yaw rate generated in the vehicle at a predetermined steering angle θs and vehicle speed V. Here, the horizontal axis represents the frequency F, and the vertical axis represents the yaw rate gain Kγ which is the amplitude ratio of the yaw rate with respect to the frequency F.

[0076] On the other hand, when the gear ratio VG becomes a slow state through the steering angle ratio variable control unit 71, as indicated by the arrow in FIG. 5, the absolute value of the yaw rate gain Kγ shifts to the decreasing side. Thereby, in the frequency response characteristics of the yaw rate generated in the vehicle, by correcting the gear ratio VG so that it becomes a slow state, the absolute value of the peak value that appears transiently is reduced. That is, by executing the correction of the gear ratio VG regardless of the adaptation, it is possible to perform a correction that stabilizes the vehicle behavior.

[0077] <Effect of the Embodiment> (1-1) By performing the correction of the gear ratio VG regardless of compliance, it is possible to perform a correction that stabilizes the behavior of the vehicle. Therefore, even if an event that destabilizes the behavior of the vehicle occurs, the behavior of the vehicle can be restored to be stable. Accordingly, it becomes difficult for the behavior of the vehicle to become unstable.

[0078] (1-2) The event conditions are set to include the vehicle being in a turning operation. Thereby, for the case where it is assumed that the vehicle is in a turning operation as an event that makes the behavior of the vehicle unstable, the behavior of the vehicle can be restored to be stable. Accordingly, when the vehicle is in a turning operation, it becomes difficult for the behavior of the vehicle to become unstable.

[0079] (1-3) The event conditions are set to include changing the yaw rate generated in the vehicle while the vehicle is in a turning operation. Thereby, for the case where it is assumed that the yaw rate generated in the vehicle is changed while the vehicle is in a turning operation as an event that makes the behavior of the vehicle unstable, the behavior of the vehicle can be restored to be stable. Accordingly, when the yaw rate generated in the vehicle is changed while the vehicle is in a turning operation, it becomes difficult for the behavior of the vehicle to become unstable.

[0080] (1-4) The event conditions are set to include changing the yaw rate generated in the vehicle unintentionally by the driver while the vehicle is in a turning operation. Thereby, for the case where it is assumed that the yaw rate generated in the vehicle is changed unintentionally by the driver while the vehicle is in a turning operation as an event that makes the behavior of the vehicle unstable, the behavior of the vehicle can be restored to be stable. Accordingly, when the yaw rate generated in the vehicle is changed unintentionally by the driver while the vehicle is in a turning operation, it becomes difficult for the behavior of the vehicle to become unstable.

[0081] (1-5) When the event condition becomes non - established after it has been established, the steering angle ratio variable control unit 71 performs a process of canceling the temporary correction of the gear ratio VG. Also, the steering control unit 60 includes a target pinion angle calculation unit 62 and a pinion angle feedback control unit 63. And the target pinion angle calculation unit 62 includes an offset component calculation processing unit 72 and an offset reflection processing unit 73 among the components including the steering angle ratio variable control unit 71. As a result, the temporarily corrected gear ratio VG has the influence of the correction canceled by the offset reflection processing unit 73 after the cancellation of the temporary correction. Therefore, it is effective in suppressing the sudden change of the target pinion angle θp* when the release component θd is reflected by the offset reflection processing unit 73.

[0082] (1-6) The offset reflection processing unit 73 performs a process of making variable the release amount θd2 for adding the release component θd to the target pinion angle θp*. Thereby, even when reflecting the release component θd, if the release amount θd2 can be made variable, the change of the target pinion angle θp* can be adjusted. This is effective in stabilizing the behavior of the vehicle while the release component θd is being reflected.

[0083] (1-7) When the event condition is established, the steering angle ratio variable control unit 71 performs a process of correcting the steering end position θend. The correction of the steering end position θend aims to correct the steering end position θend so that the absolute value becomes smaller to a steering end position suitable for the vehicle speed V at that time.

[0084] For example, FIG. 6 shows the left - and right - hand steering end positions θend at a predetermined vehicle speed V. Here, the horizontal axis represents the steering angle θs, and the vertical axis represents the regulating reaction force Fr. Also, "0" in FIG. 6 indicates the steering neutral position.

[0085] On the other hand, when the absolute value of the steering end position θend becomes small through the steering angle ratio variable control unit 71, as indicated by the arrow in Fig. 6, the absolute value of the steering end position θend shifts toward the steering neutral position side. As a result, within the rotation range of the steering wheel 3, it is corrected so as to be reduced, whereby the behavior of the vehicle is restricted. That is, by performing the correction of the steering end position θend regardless of compliance, it becomes difficult for the behavior of the vehicle to become unstable.

[0086] <Other Embodiments> The above embodiments may be modified as follows. Also, the following other embodiments can be combined with each other within a technically non - conflicting range.

[0087] · The event in which the behavior of the vehicle becomes unstable only needs to consider that the vehicle is at least in a turning operation. That is, the event condition only needs to include that the vehicle is at least in a turning operation.

[0088] · The vehicle state signal Sm may be, for example, flag information. Such flag information may be information generated by a vehicle system other than the vehicle steering system 2 mounted on the vehicle. In addition, the steering angle ratio variable control unit 71 may combine the vehicle state signal Sm with other information to determine whether the event condition is satisfied. Other information includes, for example, information regarding changes in the steering angle θs, information regarding changes in the pinion angle θp, information regarding changes in the target pinion angle θp*, information regarding the drive mode, and information regarding functional limitations of the steering motor 32. The drive mode is, for example, a function of varying the motion performance of the vehicle by variably adapting the pre - defined specification of the gear ratio VG. The functional limitation of the steering motor 32 is, for example, a function of suppressing malfunction of the steering motor 32 through limitation of the motor torque that can be output. All of these other information can be obtained from the vehicle steering system 2. In this case, the steering angle ratio variable control unit 71 can also internally generate the vehicle state signal Sm.

[0089] ·Situations where the behavior of the vehicle can become unintended by the driver can similarly occur not only in the above active steering control but also in a situation where so-called rear steering control for steering the left and right rear wheels of the vehicle is executed. Note that the rear steering control is a control executed based on an instruction from a vehicle system different from the vehicle steering system 2 mounted on the vehicle. That is, the steering control unit 60 can determine whether it is a situation where rear steering control is executed by obtaining information from a vehicle system different from the vehicle steering system 2 mounted on the vehicle. Further, a situation where the behavior of the vehicle can become unintended by the driver can occur not only when the vehicle is not in a turning travel but also in a situation where the above active control or the above rear steering control is executed. In this case, the gear ratio variable control unit 71 can also correct the gear ratio VG even when the vehicle is not in a turning travel in a situation where the above active control or the above rear steering control is executed.

[0090] ·The process of correcting the gear ratio VG may be implemented from the viewpoint of stabilizing the behavior of the vehicle. For example, when the event condition is satisfied, the gear ratio variable control unit 71 may calculate the gear ratio VG obtained by correcting the gear ratio adapted to the steering angle θs and the vehicle speed V at that time so as to be in a quick state. Further, when the event condition is satisfied, the gear ratio variable control unit 71 may calculate the gear ratio VG obtained by correcting the gear ratio adapted to the steering angle θs and the vehicle speed V at that time so as to be either in a slow state or a quick state.

[0091] ·The process of correcting the gear ratio VG may be realized by map calculation. For example, the gear ratio variable control unit 71 may switch the gear ratio map according to whether the event condition is satisfied. Alternatively, the process of correcting the gear ratio VG may be realized by correcting the adjustment amount θvg.

[0092] · When the offset component calculation processing unit 72 determines that the event condition has switched from non - fulfillment to fulfillment, instead of storing the target pinion angle θft0 before correction, it may include a process of storing the pinion angle θp at that time as the pinion angle before correction. In this case, the offset base component θftb is the deviation between the target pinion angle θp1* when the event condition switches from fulfillment to non - fulfillment and the stored pinion angle before correction. Additionally, the offset base component θftb may be a component considering the pinion angle θp. For example, it may be the deviation between the pinion angle θp when the event condition switches from fulfillment to non - fulfillment and the target pinion angle θft0 before correction. Also, the offset base component θftb may be the deviation between the pinion angle θp when the event condition switches from fulfillment to non - fulfillment and the pinion angle before correction.

[0093] · When the offset component calculation processing unit 72 determines that the event condition has switched from fulfillment to non - fulfillment, it may include a process of calculating the target pinion angle after correction release. The target pinion angle after correction release is the target pinion angle θp1* first obtained based on the gear ratio VG adapted to the steering angle θs and vehicle speed V after determining that the event condition has switched from fulfillment to non - fulfillment. Then, the offset component calculation processing unit 72 may calculate the offset base component θftb, which is the deviation between the target pinion angle θp1* at the time of determining that the event condition has switched from fulfillment to non - fulfillment and the target pinion angle after correction release.

[0094] · Instead of calculating the offset base component θftb, the offset component calculation processing unit 72 may calculate the offset base component, which is the difference in the gear ratio VG before and after temporary correction. For example, the offset reflection processing unit 73 may subtract the difference in the gear ratio VG from the gear ratio VG adapted to the steering angle θs and vehicle speed V, and add at least a part of the difference in the gear ratio VG to the gear ratio VG adapted to the steering angle θs and vehicle speed V.

[0095] · After the event condition changes from being satisfied to not being satisfied, the offset reflection processing unit 73 may include a process of immediately releasing the offset base component θftb. · The offset reflection processing unit 73 may be a process of releasing the offset base component θftb by a predetermined amount over time. For example, the offset reflection processing unit 73 may set the lower limit value of the release base amount θd1 to be greater than "0". In this case, the release gain calculation unit 81 and the release amount calculation unit 82 can be eliminated in the offset reflection processing unit 73.

[0096] · In the above embodiment, the processes related to the offset component calculation processing unit 72 and the offset reflection processing unit 73 may be eliminated. In this case, the target pinion angle calculation unit 62 can also suppress a sudden change in the target pinion angle θp* by applying a so-called change amount guard that limits the change amount with respect to the gear ratio VG.

[0097] · The characteristics of the gear ratio VG, that is, the characteristics of the gear ratio map, can be appropriately changed, such as changing stepwise. · The characteristics of the release gain G, that is, the characteristics of the release gain map, can be appropriately changed, such as having a dead zone where the value of the release gain G does not change even when the vehicle speed V changes. This is the same for the release amount map.

[0098] · In the release amount calculation unit 82, instead of using the pinion angular velocity ωp, a differential value obtained by differentiating the target pinion angle θp* may be used. · The gear ratio VG may be an index indicating the ratio of the change amount of the target pinion angle θp* to the change amount of the steering angle θs, that is, a value of "1" or more. In the case of other embodiments described herein, the adjustment amount θvg will indicate the target pinion angle θp1*.

[0099] · The steering end position θend may not be a target to be corrected based on the vehicle state signal Sm. · The steering end position θend may be a fixed value regardless of the vehicle speed V, or · The pinion angle feedback control unit 63 may execute PID control using a proportional term, an integral term, and a derivative term as feedback processing of the pinion angle θp.

[0100] · The rudder angle ratio variable control unit 71 may be the processing of the reaction force control unit 50. Also, each of the control units 50 and 60 may be a single control unit that aggregates these processes. · When calculating the steering reaction force command value Ts*, the steering reaction force command value calculation unit 52 may not use either the vehicle speed V or the steering torque Th, or may use a combination of other elements.

[0101] · The steering reaction force command value calculation unit 52 may calculate, as the steering reaction force command value Ts*, a value calculated by executing torque feedback processing that causes the steering torque Th to follow the target steering torque calculated based on the steering torque Th.

[0102] · The steering angle calculation unit 51 may calculate the steering angle θs by taking into account the twist of the steering shaft 11 corresponding to the steering torque Th. · The steering angle θs may be the detection value of a steering angle sensor that directly detects the rotation angle of the steering shaft 11. Note that the steering angle sensor may be provided, for example, between the steering wheel 3 and the torque sensor 41 on the steering shaft 11.

[0103] · It is not essential for the steering actuator 12 to include the steering side reduction mechanism 14. · The steering motor 13 is not limited to a three-phase brushless motor. For example, it may be a DC motor with brushes. The other embodiments described herein can be similarly applied to the steering motor 32.

[0104] · The pinion angle θp may be obtained by converting the detection value of the movement amount of the rack shaft 22. In this case, the control amount and the like related to the pinion angle θp will be converted by the detection value of the movement amount of the rack shaft 22.

[0105] ·The steering member that the driver operates to steer the vehicle is not limited to the steering wheel 3. For example, it may be a joystick. ·The steering unit 6 is not limited to a configuration in which the right steering wheel 5 and the left steering wheel 5 are interlocked. In other words, it may be possible to independently control the right steering wheel 5 and the left steering wheel 5.

[0106] ·The vehicle steering system 2 is configured to have a linkless structure in which the steering unit 4 and the steering unit 6 are mechanically separated at all times, but it is not limited to this. For example, it may be configured such that the steering unit 4 and the steering unit 6 can be mechanically separated by a clutch.

[0107] ·The steering motor 32 may be, for example, arranged coaxially with the rack shaft 22 or connected to the pinion shaft constituting the rack and pinion mechanism of the rack shaft 22 via a worm and wheel.

Explanation of symbols

[0108] 1... Steering control device 2... Vehicle steering system 3... Steering wheel (steering member) 4... Steering unit 5... Steering wheel 6... Steering unit 32... Steering motor 60... Steering control unit 62... Target pinion angle calculation unit 63... Pinion angle feedback control unit 71... Steering angle ratio variable control unit 72... Offset component calculation processing unit 73... Offset reflection processing unit 81... Release gain calculation unit 82... Release amount calculation unit 83... Sign processing unit 84... Release gain reflection processing unit 85... Sign reflection processing unit 86... Release component calculation processing unit 87... Release component reflection processing unit

Claims

1. A steering control device for controlling a steering device of a vehicle, wherein the steering device has a structure in which a power transmission path between a steering unit having a steering member and a steering unit configured to steer a steered wheel is separated, so that the positional relationship between the steering position of the steering member and the steering position of the steered wheel can be changed, the positional relationship is pre - adapted from the viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle, the steering unit includes a steering motor that generates a steering force for steering the steered wheel, the steering control device is configured to execute a steering control process, the steering control process includes a position - relationship change process of changing the positional relationship based on the state of the vehicle, and is a process for controlling the operation of the steering motor so as to apply the steering force to the steered wheel so that the steering position becomes the steering position taking into account the positional relationship with respect to the steering position, the position - relationship change process includes a process of temporarily correcting the positional relationship regardless of the adaptation so that the behavior of the vehicle becomes stable when an event condition indicating that an event causing the behavior of the vehicle to become unstable has occurred is satisfied. A steering control device.

2. The steering control device according to claim 1, wherein the event condition includes that the vehicle is in a turning operation.

3. The steering control device according to claim 1, wherein the event condition includes changing a yaw rate generated in the vehicle while the vehicle is in a turning operation.

4. The steering control device according to claim 1, wherein the event condition includes changing a yaw rate generated in the vehicle unintentionally by the driver while the vehicle is in a turning operation.

5. The position - relationship change process includes a process of canceling the temporary correction of the positional relationship when the event condition becomes non - satisfied after the event condition is satisfied, the steering control process includes a target steering position calculation process of calculating a target steering position obtained by taking into account the positional relationship based on the steering position, and a steering operation amount calculation process of calculating an operation amount for controlling the steering position to the target steering position by feedback processing, the target steering position calculation process includes an offset calculation process of calculating an offset component for reducing the absolute value of the difference in the target steering position before and after the temporary correction of the positional relationship in the position - relationship change process. The offset operation processing includes a release process of subtracting the offset component from the target steering position and adding a release component, which is at least a part of the offset component, to the target steering position. The steering control device according to any one of claims 1 to 4, wherein the release process is a process that is started in accordance with the position relationship change process releasing a temporary correction of the position relationship.

6. The steering control device according to claim 5, wherein the release process includes a process of variably setting an addition amount for adding the release component to the target steering position.

7. A steering control method for controlling a steering device of a vehicle configured to be able to change a position relationship between a steering position of a steering member and a steering position of a steered wheel so as to have a position relationship preliminarily adapted from a viewpoint of stabilizing the behavior of the vehicle based on the state of the vehicle, the structure having a power transmission path separated between a steering unit having the steering member of the vehicle and a steering unit including a steering motor that generates a steering force for steering the steered wheels of the vehicle, The steering control method includes executing a steering control process. The steering control process is a process for controlling the operation of the steering motor so as to apply the steering force to the steered wheels so that the steered wheels have a steering position taking into account the position relationship with respect to the steering position, including a process for changing the position relationship based on the state of the vehicle. The process for changing the position relationship includes a process of temporarily correcting the position relationship regardless of the adaptation so that the behavior of the vehicle becomes stable when an event condition indicating that an event in which the behavior of the vehicle becomes unstable has occurred is satisfied.

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