Steering control device

Abstract

To provide a steering control device that can suppress unintended behavior of a steering wheel or a turning wheel.SOLUTION: A steering control device includes two reaction force control circuits (41A, 42A). Each of the reaction force control circuits controls in a coordinated manner a reaction force motor that generates steering reaction force. When being started, each reaction force control circuit executes start sequence including processing required to automatically rotate the steering wheel through the reaction motor. When the execution of the start sequence is completed, the reaction force control circuit stores information indicating whether the start sequence is normally completed. When one of the two reaction force control circuits is reset, at the time of restart after the completion of reset, when the information indicating that the start sequence is normally completed remains, the reset reaction force control circuit does not continue the execution of the start sequence.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Conventionally, there have been steering devices of the so-called steer-by-wire type, in which power transmission between the steering wheel and the steered wheels is separated. For example, the steer-by-wire system disclosed in Patent Document 1 has a reaction force actuator and a steering actuator. The reaction force actuator generates a steering reaction force applied to the steering shaft. The steering actuator generates a steering force that steers the steered wheels.

[0003] The reaction force actuator and the steering actuator each have two redundantly provided control calculation units and two redundantly provided motor drive units. The control calculation units of each system cooperate with each other to generate torque in the motor drive unit of each system. The control calculation units perform calculations related to motor drive control. The motor drive units generate torque based on drive signals generated by their corresponding control calculation units.

[0004] In a steer-by-wire steering device, the steering wheel is not restricted by the steering mechanism. Therefore, when an external force is applied to the steering wheel while the vehicle is powered off, the steering wheel may rotate. In this case, the steered wheels do not move, and the positional relationship between the steering wheel and the steered wheels may differ from the intended positional relationship according to the specified steering angle ratio.

[0005] Therefore, for example, the control device in Patent Document 2 determines whether the positional relationship between the steering position of the steering wheel and the steered position of the steered wheels is the original positional relationship when the vehicle power is turned on. If the positional relationship between the steering position and the steered position is different from the original positional relationship, the control device changes at least one of the operating position and the steered position so that the positional relationship between the steering position and the steered position becomes the original positional relationship. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-70431 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-153109 Summary of the Invention [Problem to be solved by the invention]

[0007] It is conceivable to provide the steer-by-wire system of Patent Document 1 with a function for correcting the positional relationship between the steering position and the turning position of Patent Document 2. However, in this case, the following concern arises. That is, the control calculation unit may momentarily stop operating due to a power failure or a microcomputer reset, and then return to a normal operating state. Therefore, there is a risk that the correction process for the positional relationship between the steering position and the turning position will be executed every time the control calculation unit returns to a normal operating state. Therefore, there is a concern that the driver may feel uncomfortable due to unintended behavior of the steering wheel or steered wheels caused by the execution of the correction process. [Means for solving the problem]

[0008] A steering control device that can solve the above problem has two reaction force control circuits configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel whose power transmission is separated from the steered wheels of a vehicle. When the reaction force control circuit is started, it executes a preparatory process including a process required to automatically rotate the steering wheel via the reaction force motor, and when the execution of the preparatory process is completed, it stores information indicating whether the preparatory process was completed normally. When either of the two reaction force control circuits is reset, the reset reaction force control circuit is configured not to execute the preparatory process when restarted after the reset if the information indicating the preparatory process was completed normally remains.

[0009] With this configuration, when the reset reaction force control circuit is restarted after the reset is complete, if information indicating that the preparation process was completed successfully remains, the reaction force control circuit will not execute a new preparation process, thereby preventing unintended behavior of the steering wheel or steered wheels.

[0010] In the above steering control device, the reset reaction force control circuit may be configured to, when restarted after the reset is complete, transition its own control state to the control state of the unreset reaction force control circuit without executing the preparation process if the information indicating that the preparation process has been completed successfully remains.

[0011] According to this configuration, after the resetting of the reaction force control circuit is completed, the two reaction force control circuits can again cooperate to control the reaction force motor. In the above steering control device, the reset reaction force control circuit may be configured to stop its own operation without executing the preparation process when the information indicating that the preparation process has been completed successfully does not remain when the reaction force control circuit is restarted after the reset is complete.

[0012] With this configuration, the reset reaction force control circuit does not execute new preparation processing after the reset is complete, thereby preventing unintended behavior of the steering wheel or steered wheels due to the execution of preparation processing.

[0013] The above steering control device may further include two steering control circuits configured to control a steering motor that generates a steering force for turning the steered wheels. In this case, the reaction force control circuit that has not been reset may be configured to execute processing to stop operation of the reset reaction force control circuit and the steering control circuit in the same system as the reset reaction force control circuit when the information indicating that the preparation processing has been completed normally does not remain when the reset reaction force control circuit is restarted.

[0014] According to this configuration, after the operation of the reaction force control circuit and steering control circuit of the system in which the reset occurred has stopped, the reaction force control circuit and steering control circuit of the system in which the reset did not occur can continue to control the reaction force motor and steering motor.

[0015] In the above-mentioned steering control device, the preparation process may include a midpoint learning process that learns a steering neutral position of the steering wheel by automatically rotating the steering wheel through driving of the reaction motor, and a steering angle synchronization process that corrects the rotational position of the steering wheel so that the rotational position of the steering wheel becomes a rotational position corresponding to the steered position of the steered wheels.

[0016] When the preparatory processing includes the midpoint learning processing and the steering angle synchronization processing as in the case of this configuration, there is a risk that the steering wheel will automatically rotate when the reaction force control circuit is started. The above steering control device is suitable for the case where the preparatory processing includes the midpoint learning processing and the steering angle synchronization processing. [Effects of the Invention]

[0017] According to the steering control device of the present invention, unintended behavior of the steering wheel or steered wheels can be suppressed. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a configuration diagram of a steer-by-wire type steering device in which an embodiment of a steering control device is mounted. [Figure 2] FIG. 2 is a block diagram of a reaction force control device and a steering control device according to an embodiment. [Figure 3] 4 is a time chart showing a start-up sequence of a reaction force control device and a vehicle control device according to an embodiment; [Figure 4] 5A and 5B are configuration diagrams showing an example of a reset occurrence state in the reaction force control device and the turning control device of one embodiment. [Figure 5]10(a) and 10(b) are time charts showing an example of state transitions of a second reaction force control circuit according to an embodiment. [Figure 6] 10(a) and 10(b) are time charts showing another example of state transitions of the second reaction force control circuit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described below. As shown in FIG. 1, vehicle steering device 10 has steering shaft 12 connected to steering wheel 11. Steering device 10 also has steered shaft 13 extending in the vehicle width direction (left-right direction in FIG. 1). Steered wheels 15 are connected to both ends of steered shaft 13 via tie rods 14. The linear movement of steered shaft 13 changes the steering angle θw of steered wheels 15. Steering shaft 12 and steered shaft 13 constitute the steering mechanism of the vehicle. Note that FIG. 1 shows only steered wheels 15 on one side.

[0020] The steering device 10 has a reaction motor 21 and a reduction mechanism 22. The reaction motor 21 is a source of a steering reaction force. The steering reaction force is a force that acts in the opposite direction to the direction of operation of the steering wheel 11 by the driver. The rotation shaft of the reaction motor 21 is connected to the steering shaft 12 via the reduction mechanism 22. The torque of the reaction motor 21 is applied to the steering shaft 12 as a steering reaction force. By applying the steering reaction force to the steering wheel 11, it is possible to give the driver an appropriate sense of response.

[0021] The reaction motor 21 is, for example, a three-phase brushless motor. The reaction motor 21 has a first winding group N11 and a second winding group N12. The first winding group N11 and the second winding group N12 are wound around a common stator (not shown). The first winding group N11 and the second winding group N12 have equivalent electrical characteristics.

[0022] Steering device 10 has a steering motor 31 and a reduction mechanism 32. Steering motor 31 is a source of steering force. The steering force refers to the power for steering steered wheels 15. The rotating shaft of steering motor 31 is connected to pinion shaft 33 via reduction mechanism 32. Pinion teeth 33a of pinion shaft 33 mesh with rack teeth 13a of steering shaft 13. The torque of steering motor 31 is applied to steering shaft 13 via pinion shaft 33 as a steering force. In response to the rotation of steering motor 31, steering shaft 13 moves in the vehicle width direction.

[0023] The steering motor 31 is, for example, a three-phase brushless motor. The steering motor 31 has a first winding group N21 and a second winding group N22. The first winding group N21 and the second winding group N22 are wound around a common stator (not shown). The first winding group N21 and the second winding group N22 have equivalent electrical characteristics.

[0024] The steering device 10 has a reaction force control device 40. The reaction force control device 40 controls the drive of the reaction force motor 21, which is the object to be controlled. The reaction force control device 40 executes reaction force control in which the reaction force motor 21 generates a steering reaction force corresponding to the steering torque Th. The reaction force control device 40 calculates a target steering reaction force based on the steering torque Th detected through a torque sensor 23. The torque sensor 23 is provided on the steering shaft 12. The reaction force control device 40 controls the power supply to the reaction force motor 21 so that the actual steering reaction force applied to the steering shaft 12 matches the target steering reaction force. The reaction force control device 40 controls the power supply to each of the two systems of winding groups in the reaction force motor 21 independently.

[0025] The reaction force control device 40 has a first circuit system 41 and a second circuit system 42. The first circuit system 41 controls the power supply to the winding group N11 of the first system in the reaction force motor 21 in accordance with the steering torque Th detected by the torque sensor 23. The second circuit system 42 controls the power supply to the winding group N12 of the second system in the reaction force motor 21 in accordance with the steering torque Th detected by the torque sensor 23.

[0026] The reaction force control device 40 and the on-board vehicle control device 60 are connected to each other via an on-board network 61. The on-board network 61 is, for example, a CAN (Controller Area Network). The reaction force control device 40 and the on-board vehicle control device 60 exchange information with each other via the on-board network 61. The vehicle control device 60 controls the running of the vehicle. Specifically, the vehicle control device 60 controls, for example, the vehicle's powertrain. The powertrain includes a driving source for running the vehicle and a power transmission mechanism. The driving source for running includes, for example, an engine or a motor. The power transmission mechanism is a mechanism for transmitting power generated by the driving source for running to the drive wheels. The reaction force control device 40 controls the driving of the reaction force motor 21 based on information exchanged with the vehicle control device 60.

[0027] Steering device 10 has steering control device 50. Steering control device 50 controls the drive of steering motor 31, which is the object to be controlled. Steering control device 50 executes steering control in which steering motor 31 generates a steering force for turning steered wheels 15 in accordance with the steering state. Steering control device 50 takes in steering angle θs detected via steering angle sensor 24 and stroke Xw of steered shaft 13 detected via stroke sensor 34. Steering angle θs is a state variable that indicates the amount of rotational operation of steering wheel 11. Stroke Xw is the amount of displacement of steered shaft 13 relative to the neutral position, and is a state variable that reflects steering angle θw. Steering angle sensor 24 is provided between torque sensor 23 of steering shaft 12 and reduction mechanism 22. Stroke sensor 34 is provided in the vicinity of steered shaft 13.

[0028] Steering control device 50 calculates a target steering angle of steered wheels 15 based on steering angle θs detected by steering angle sensor 24. The target steering angle can be obtained, for example, by multiplying the detected steering angle θs by a steering angle ratio. The steering angle ratio is the ratio of steering angle θw to steering angle θs. The steering angle ratio is a value that is set in advance according to product specifications, etc. Steering control device 50 calculates steering angle θw based on stroke Xw of steered shaft 13 detected by stroke sensor 34. Steering control device 50 controls the power supply to steering motor 31 so that steering angle θw calculated based on stroke Xw matches the target steering angle. Steering control device 50 controls the power supply to two systems of winding groups in steering motor 31 independently for each system.

[0029] The steering control device 50 has a first circuit system 51 and a second circuit system 52. The first circuit system 51 controls the power supply to the winding group N21 of the first system in the steering motor 31, based on the steering angle θs detected through the steering angle sensor 24 and the stroke Xw of the steering shaft 13 detected through the stroke sensor 34. The second circuit system 52 controls the power supply to the winding group N22 of the second system in the steering motor 31, based on the steering angle θs detected through the steering angle sensor 24 and the stroke Xw of the steering shaft 13 detected through the stroke sensor 34.

[0030] Note that a so-called electromechanical integrated type reaction force actuator may be configured by integrally providing reaction force control device 40 and reaction force motor 21. Also, a so-called electromechanical integrated type steering actuator may be configured by integrally providing steering control device 50 and steering motor 31. Reaction force control device 40 and steering control device 50 configure a steering control device.

[0031] <Reaction force control device> Next, the configuration of the reaction force control device will be described in detail. 2, the reaction force control device 40 has a first circuit system 41 and a second circuit system 42. The first circuit system 41 has a first reaction force control circuit 41A and a motor drive circuit 41B. The second circuit system 42 has a second reaction force control circuit 42A and a motor drive circuit 42B.

[0032] The first reaction force control circuit 41A is configured by processing circuits including: (1) one or more processors operating according to a computer program (software); (2) one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that perform at least some of the various processes; and (3) a combination thereof. The processor includes a central processing unit (CPU). The processor also includes memory, such as random-access memory (RAM) and read-only memory (ROM). The memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., non-transitory computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0033] The first reaction force control circuit 41A calculates a target steering reaction force to be generated in the reaction force motor 21 based on the steering torque Th detected via the torque sensor 23, and calculates a first current command value for the winding group N11 of the first system according to the value of the calculated target steering reaction force. However, the first current command value is set to a value that is half (50%) of the amount of current (100%) required for the reaction force motor 21 to generate the target steering reaction force. The first reaction force control circuit 41A generates a drive signal (PWM signal) for the motor drive circuit 41B by executing current feedback control that causes the value of the actual current supplied to the winding group N11 of the first system to follow the first current command value.

[0034] The motor drive circuit 41B is a PWM inverter in which three legs, each corresponding to one of the three phases (U, V, and W), are connected in parallel, with each leg consisting of two switching elements such as field-effect transistors (FETs) connected in series. The motor drive circuit 41B converts DC power supplied from the battery into three-phase AC power by switching the switching elements of each phase based on a drive signal generated by the first reaction force control circuit 41A. The three-phase AC power generated by the motor drive circuit 41B is supplied to a first winding group N11 of the reaction force motor 21 via a power supply path for each phase, which is formed by a bus bar or a cable. This causes the first winding group N11 to generate torque according to a first current command value.

[0035] The second reaction force control circuit 42A has basically the same configuration as the first reaction force control circuit 41A. The second reaction force control circuit 42A calculates a target steering reaction force to be generated in the reaction force motor 21 based on the steering torque Th detected by the torque sensor 23, and calculates a second current command value for the winding group N12 of the second system according to the value of the calculated target steering reaction force. However, the second current command value is set to a value that is half (50%) of the amount of current required for the reaction force motor 21 to generate the target steering reaction force. The second reaction force control circuit 42A generates a drive signal for the motor drive circuit 42B by performing current feedback control that causes the value of the actual current supplied to the winding group N12 of the second system to follow the second current command value.

[0036] The motor drive circuit 42B has basically the same configuration as the motor drive circuit 41B. The motor drive circuit 42B converts DC power supplied from the battery into three-phase AC power based on a drive signal generated by the second reaction force control circuit 42A. The three-phase AC power generated by the motor drive circuit 42B is supplied to the second winding group N12 of the reaction force motor 21 via power supply paths for each phase, which are made up of bus bars or cables, etc. This causes the second winding group N12 to generate torque according to the second current command value. The reaction force motor 21 generates a torque that is the sum of the torque generated by the first winding group N11 and the torque generated by the second winding group N12.

[0037] Depending on the product specifications, there may be a master-slave relationship between the first circuit system 41 and the second circuit system 42 of the reaction force control device 40. In this case, for example, the first circuit system 41 may function as the master and the second circuit system 42 may function as the slave. Also, depending on the product specifications, the first circuit system 41 and the second circuit system 42 may have an equal relationship.

[0038] <Steering control device> Next, the configuration of the steering control device 50 will be described in detail. As shown in Fig. 2, the steering control device 50 has a first circuit system 51 and a second circuit system 52. The first circuit system 51 has a first steering control circuit 51A and a motor drive circuit 51B. The second circuit system 52 has a second steering control circuit 52A and a motor drive circuit 52B.

[0039] First steering control circuit 51A has basically the same configuration as first reaction force control circuit 41A. First steering control circuit 51A calculates a target steering angle of steered wheels 15 based on steering angle θs detected by steering angle sensor 24. Steering control device 50 calculates steering angle θw based on stroke Xw of steered shaft 13 detected by stroke sensor 34. First steering control circuit 51A calculates a target steering force to be generated in steering motor 31 by executing angle feedback control that causes steering angle θw calculated based on stroke Xw to follow the target steering angle, and calculates a third current command value for first system winding group N21 of steering motor 31 according to the value of this calculated target steering force. However, the third current command value is set to a value that is half (50%) of the amount of current required for steering motor 31 to generate the target steering force. The first steering control circuit 51A generates a drive signal for the motor drive circuit 51B by performing current feedback control that causes the value of the actual current supplied to the first system winding group N21 to follow the third current command value.

[0040] Motor drive circuit 51B basically has the same configuration as motor drive circuit 41B. Motor drive circuit 51B converts DC power supplied from a battery into three-phase AC power based on a drive signal generated by first steering control circuit 51A. The three-phase AC power generated by motor drive circuit 42B is supplied to winding group N21 of the first system of steering motor 31 via power supply paths for each phase formed by bus bars, cables, or the like. This causes winding group N21 of the first system to generate torque according to the third current command value.

[0041] Second steering control circuit 52A has basically the same configuration as first reaction force control circuit 41A. Second steering control circuit 52A calculates a target steering angle of steered wheels 15 based on steering angle θs detected by steering angle sensor 24. Steering control device 50 calculates steering angle θw based on stroke Xw of steered shaft 13 detected by stroke sensor 34. Second steering control circuit 52A calculates a target steering force to be generated in steering motor 31 by executing angle feedback control that causes steering angle θw calculated based on stroke Xw to follow the target steering angle, and calculates a fourth current command value for second system winding group N22 of steering motor 31 in accordance with the value of this calculated target steering force. However, fourth current command value is set to a value that is half (50%) of the amount of current required for steering motor 31 to generate the target steering force. The second steering control circuit 52A generates a drive signal for the motor drive circuit 52B by performing current feedback control that causes the value of the actual current supplied to the second system winding group N22 to follow the fourth current command value.

[0042] Motor drive circuit 52B basically has the same configuration as motor drive circuit 41B. Motor drive circuit 51B converts DC power supplied from the battery into three-phase AC power based on a drive signal generated by second steering control circuit 52A. The three-phase AC power generated by motor drive circuit 52B is supplied to winding group N22 of the second system of steering motor 31 via power supply paths for each phase formed by bus bars, cables, or the like. This causes winding group N22 of the second system to generate torque according to the fourth current command value. Steering motor 31 generates torque which is the sum of the torque generated by winding group N21 of the first system and the torque generated by winding group N22 of the second system.

[0043] Depending on the product specifications, there may be a master-slave relationship between the first circuit system 51 and the second circuit system 52 of the steering control device 50. In this case, for example, the first circuit system 51 may function as the master and the second circuit system 52 may function as the slave. Also, depending on the product specifications, the first circuit system 51 and the second circuit system 52 may have an equal relationship.

[0044] <Communication path> Next, the internal communication paths of the reaction force control device 40 and the steering control device 50, and the communication path between the reaction force control device 40 and the steering control device 50 will be described.

[0045] As shown in FIG. 2, the first reaction force control circuit 41A and the second reaction force control circuit 42A exchange information with each other via a communication line L1. The information includes abnormality information about the first reaction force control circuit 41A, the second reaction force control circuit 42A, or the motor drive circuits 41B and 42B. The information also includes flag values ​​indicating various states. The first reaction force control circuit 41A and the second reaction force control circuit 42A cooperate to control the drive of the reaction force motor 21 based on the information exchanged between them.

[0046] The first steering control circuit 51A and the second steering control circuit 52A exchange information with each other via communication line L2. The information includes abnormality information of the first steering control circuit 51A, the second steering control circuit 52A, or the motor drive circuits 51B, 52B. The information also includes flag values ​​that indicate various states. The first steering control circuit 51A and the second steering control circuit 52A cooperate to control the drive of the steering motor 31 based on the information exchanged between them.

[0047] The first reaction force control circuit 41A and the first turning control circuit 51A exchange information with each other via communication line L3. The information includes abnormality information for the first reaction force control circuit 41A, the first turning control circuit 51A, and the motor drive circuits 41B, 51B. The information also includes flag values ​​indicating various states. The first reaction force control circuit 41A and the first turning control circuit 51A operate in cooperation with each other based on the information exchanged between them.

[0048] The second reaction force control circuit 42A and the second turning control circuit 52A exchange information with each other via communication line L4. The information includes abnormality information of the second reaction force control circuit 42A, the second turning control circuit 52A, or the motor drive circuits 42B, 52B. The information also includes flag values ​​indicating various states. The second reaction force control circuit 42A and the second turning control circuit 52A operate in cooperation with each other based on the information exchanged between them.

[0049] <Motor drive mode> Next, a description will be given of the drive modes of reaction force motor 21 and steering motor 31. The drive modes include a cooperative drive mode, an independent drive mode, and a single-system drive mode.

[0050] The cooperative drive mode is a normal drive mode in which first system circuits 41, 51 and second system circuits 42, 52 are operating normally. First system circuit 41 and second system circuit 42 share information such as command values ​​and limit values ​​with each other, and generate equal torque in both the first system winding group N11 and the second system winding group N12 of reaction force motor 21. First system circuit 51 and second system circuit 52 share information such as command values ​​and limit values ​​with each other, and generate equal torque in both the first system winding group N21 and the second system winding group N22 of steering motor 31.

[0051] In the case where there is a master-slave relationship between first system circuit 41 and second system circuit 42 of reaction force control device 40, when the cooperative drive mode is selected as the drive mode, the slave uses the command value calculated by the master to control the drive of reaction force motor 21. Also, in the case where there is a master-slave relationship between first system circuit 51 and second system circuit 52 of turning control device 50, when the cooperative drive mode is selected as the drive mode, the slave uses the command value calculated by the master to control the drive of turning motor 31.

[0052] The independent drive mode is a drive mode used when one of the four control circuits (41A, 42A, 51A, 52A) momentarily stops operating but the abnormality has not been determined and there is a possibility that normal operation will be restored. In the independent drive mode, for example, when there is a possibility that one control circuit whose operation has stopped will return to normal operation, the remaining three control circuits generate torque in their corresponding winding groups based on their own calculation results without using information from inter-system communication.

[0053] In the case where there is a master-slave relationship between the first system circuit 41 and the second system circuit 42 of the reaction force control device 40, when the independent drive mode is selected as the drive mode, the master-slave relationship between the first system circuit 41 and the second system circuit 42 is temporarily canceled. Also, in the case where there is a master-slave relationship between the first system circuit 51 and the second system circuit 52 of the turning control device 50, when the independent drive mode is selected as the drive mode, the master-slave relationship between the first system circuit 51 and the second system circuit 52 is temporarily canceled.

[0054] The single-system drive mode is a drive mode used when an abnormality is confirmed in one of the four control circuits (41A, 42A, 51A, 52A) and there is no possibility of returning to normal operation. For example, when an abnormality is confirmed in first system circuits 41, 51, torque is generated in reaction force motor 21 and steering motor 31 only by second system circuits 42, 52. When an abnormality is confirmed in second system circuits 42, 52, torque is generated in reaction force motor 21 and steering motor 31 only by first system circuits 41, 51.

[0055] In the case where there is a master-slave relationship between the first system circuit 41 and the second system circuit 42 of the reaction force control device 40, when the single-system drive mode is selected as the drive mode, the master-slave relationship between the first system circuit 41 and the second system circuit 42 is temporarily canceled. Also, in the case where there is a master-slave relationship between the first system circuit 51 and the second system circuit 52 of the turning control device 50, when the single-system drive mode is selected as the drive mode, the master-slave relationship between the first system circuit 51 and the second system circuit 52 is temporarily canceled.

[0056] Each control circuit (41A, 42A, 51A, 52A) controls driving of each motor (21, 31) in the cooperative drive mode during normal operation when no abnormality occurs. When the cooperative drive mode is selected as the drive mode and an abnormality determination condition is satisfied, each control circuit switches the drive mode from the cooperative drive mode to the independent drive mode. Furthermore, when the independent drive mode is selected as the drive mode and a return determination condition is satisfied before an abnormality is confirmed, each control circuit returns the drive mode from the independent drive mode to the cooperative drive mode. Furthermore, when the independent drive mode is selected as the drive mode and an abnormality determination condition is satisfied, each control circuit switches the drive mode from the independent drive mode to the single-system drive mode.

[0057] The abnormality includes, for example, a communication abnormality between systems, a communication abnormality within the same system, a deviation in command values ​​between systems, and a temporary abnormality that can be recovered from, such as a decrease in the current limit value. <Startup sequence> Next, the startup sequence of the reaction force control device 40 and the vehicle control device 60 will be described. The startup sequence is a series of processes that are executed when the vehicle power supply is turned on. While the vehicle power supply is turned off, the reaction force control device 40 and the vehicle control device 60 remain in a stopped state. Turning the vehicle power supply on or off also corresponds to turning on or off a start switch provided in the driver's seat, for example. The start switch is operated to start or stop the drive source for running the vehicle, and is, for example, an ignition switch or a power switch.

[0058] First, the startup sequence of the vehicle control device 60 will be described. As shown in the time chart of FIG. 3, when the vehicle power supply is turned on (time T1), the vehicle control device 60 starts executing a predetermined startup preparation. The startup preparation includes an initial check of the vehicle control device 60 and processing required to start the vehicle's powertrain. After the startup preparation is complete, the vehicle control device 60 starts the powertrain (mainly the driving source for traveling). When the powertrain startup processing is completed, the vehicle control device 60 turns on the preparation completion signal S1 (time T2). The vehicle control device 60 turns on the preparation completion signal S1 regardless of the state of the reaction force control device 40.

[0059] The ready signal S1 is information indicating whether the vehicle is ready to run, including the completion of the powertrain start process, and whether the vehicle is ready to run. When the ready signal S1 is on, it indicates that the vehicle is ready to run. When the ready signal S1 is off, it indicates that the vehicle is not ready to run. The ready signal S1 is transmitted to the reaction force control device 40 as an electrical signal.

[0060] Next, a description will be given of the start-up sequence of the reaction force control device 40. The start-up sequence is executed by each of the first reaction force control circuit 41A and the second reaction force control circuit 42A. 3, when the vehicle power supply is turned on (time T1), the reaction force control device 40 starts up and sequentially executes an initial check, a midpoint learning process, and a steering angle synchronization process, and then transitions to an assist start waiting state. The initial check, the midpoint learning process, and the steering angle synchronization process are a series of preparatory processes required to start executing reaction force control that causes the reaction force motor 21 to generate a steering reaction force.

[0061] The initial check is an initial inspection that is executed when the vehicle power is turned on, and includes, for example, a hardware check, initialization of the CPU (Central Processing Unit), and initialization of variables or flags.

[0062] The midpoint learning process is a process for learning the neutral steering position of the steering wheel 11. The steering device 10 has a stopper mechanism that restricts the rotation of the steering wheel 11 to set a limit on the steering angle of the steering wheel 11. The stopper mechanism, for example, restricts the steering range of the steering wheel 11 to less than 360°. The reaction force control device 40 controls the reaction force motor 21 to move the steering wheel 11 to a first operating end and then to a second operating end. After this, the reaction force control device 40 calculates the midpoint of the steering angle based on the rotation angle of the reaction force motor 21 at the start and end of the steering wheel 11's reversal movement. The midpoint of the steering angle corresponds to the motor midpoint, which is the rotational position of the reaction force motor 21 when the steering wheel 11 is located in the neutral steering position. The reaction force control device 40 stores the midpoint of the steering angle or the motor midpoint in memory as the neutral steering position of the steering wheel 11.

[0063] The reaction force control device 40 learns the neutral steering position of the steering wheel 11 when the information about the neutral steering position stored in the memory is lost. This applies, for example, when the vehicle power is turned on for the first time after a new battery is installed in the vehicle. This is because when the battery is removed from the vehicle for battery replacement, the information about the neutral steering position stored in the memory of the reaction force control device 40 is lost due to the loss of power supply to the reaction force control device 40.

[0064] Depending on the product specifications, the reaction force control device 40 may be configured to execute the midpoint learning process each time the vehicle power is turned on, or may be configured to execute the midpoint learning process when the reliability of the information regarding the steering neutral position stored in the memory has decreased.

[0065] The steering angle synchronization process is a process for correcting the rotational position of the steering wheel 11. When the rotational position of the steering wheel 11 is different from the rotational position corresponding to the steered position of the steered wheels 15, the reaction force control device 40 drives the reaction force motor 21 so that the rotational position of the steering wheel 11 becomes the rotational position corresponding to the steered position of the steered wheels 15.

[0066] For example, when the vehicle power supply is turned off, the reaction force control device 40 stores the steering angle θs detected immediately before as a reference steering angle. The reference steering angle is a reference for determining whether or not the steering wheel 11 is rotating while the vehicle power supply is turned off. When the steering angle θs immediately after the vehicle power supply is turned on does not match the reference steering angle, the reaction force control device 40 calculates the difference between the steering angle θs immediately after the vehicle power supply is turned on and the reference steering angle, and controls the power supply to the reaction force motor 21 to eliminate the difference.

[0067] In addition, the reaction force control device 40 may calculate the difference between the value of the steering angle θs immediately after the vehicle power supply is turned on and the value obtained by multiplying the steering angle θw immediately after the vehicle power supply is turned on by the reciprocal of the steering angle ratio, and control the power supply to the reaction force motor 21 so as to eliminate this difference.

[0068] The assist start waiting state is a state in which, after the preparation process has been completed, the reaction force control device 40 waits for confirmation that the vehicle control device 60 has completed the powertrain start process. The reaction force control device 40 determines whether or not to transition from the assist start waiting state to the normal control state, depending on the start state of the vehicle's powertrain. When the preparation complete signal S1 has not been turned on by the vehicle control device 60, the reaction force control device 40 determines that the vehicle's powertrain start process has not been completed, and maintains the assist start waiting state. When the preparation complete signal S1 has been turned on by the vehicle control device 60, the reaction force control device 40 determines that the vehicle's powertrain start process has been completed (time T3), and transitions from the assist start waiting state to the normal control state. The normal control state is a state in which reaction force control is performed to cause the reaction force motor 21 to generate a steering reaction force. When in the normal control state, the reaction force control device 40 controls the drive of the reaction force motor 21 depending on the steering state of the steering wheel 11.

[0069] In the time chart of FIG. 3, the vehicle control device 60 turns on the preparation completion signal S1 while the midpoint learning process is being executed, for example. When the vehicle power supply is turned on and the execution of the startup sequence is completed, the first reaction force control circuit 41A stores in memory whether the startup sequence was completed normally. For example, the first reaction force control circuit 41A sets a flag value depending on whether the startup sequence was completed normally. When the startup sequence is completed normally, the first reaction force control circuit 41A sets the flag value to "1." When the startup sequence is not completed normally, the first reaction force control circuit 41A sets the flag value to "0." The flag is information indicating whether the startup sequence was completed normally. Similarly to the first reaction force control circuit 41A, when the execution of the startup sequence is completed, the second reaction force control circuit 42A stores in memory whether the startup sequence was completed normally. The first reaction force control circuit 41A and the second reaction force control circuit 42A can confirm each other's flag values ​​through communication.

[0070] It should be noted that the first turning control circuit 51A and the second turning control circuit 52A also each execute a predetermined start-up sequence when the vehicle power supply is turned on. <Supplementary explanation of the control circuit> Next, the configuration of each control circuit (41A, 42A, 51A, 52A) will be further explained.

[0071] The power supply voltage of each control circuit has a guaranteed operating range. The guaranteed operating range is the voltage range within which operation is guaranteed according to specifications. When the power supply voltage changes from a value outside the guaranteed operating range to a value within the guaranteed operating range, each control circuit begins operation and executes the startup sequence shown in the time chart of Figure 3.

[0072] Each control circuit has a reset function. When a predetermined reset cause occurs, each control circuit is reset. The reset is a process for initializing the internal state of each control circuit. The reset cause includes, for example, a drop in the power supply voltage of each control circuit. When the power supply voltage temporarily drops and the value of the power supply voltage falls outside the guaranteed operating range, each control circuit is reset. When the reset is complete, each control circuit restarts and again executes the startup sequence shown in the time chart of Figure 3.

[0073] However, the resetting of each control circuit raises the following concerns. As shown in Figure 4(a), in a normal control state in which each control circuit (41A, 42A, 51A, 52A) controls the reaction force motor 21 and the steering motor 31, it is possible that, for example, the second reaction force control circuit 42A of the second system circuit 42 is reset.

[0074] After the reset is complete, the second reaction force control circuit 42A restarts. When the second reaction force control circuit 42A restarts, it executes the startup sequence shown in the time chart of FIG. 3. The startup sequence includes a midpoint learning process and a steering angle synchronization process. While these processes are being executed, the steering wheel 11 may automatically rotate in order to learn the steering neutral position of the steering wheel 11 or to correct the rotational position of the steering wheel 11.

[0075] At this time, the first reaction force control circuit 41A of the first system circuit 41, which has not been reset, continues to control the reaction force motor 21 as usual. That is, the first reaction force control circuit 41A controls the drive of the reaction force motor 21 in accordance with the steering torque Th. In contrast, the restarted second reaction force control circuit 42A controls the drive of the reaction force motor 21 to learn the steering neutral position or to correct the rotational position of the steering wheel 11. For this reason, there is a risk that the control of the first reaction force control circuit 41A and the control of the second reaction force control circuit 42A will interfere with each other. Furthermore, there is a risk that the steering wheel 11 will automatically rotate unintentionally.

[0076] First steering control circuit 51A and second steering control circuit 52A that have not been reset continue to control steering motor 31 as usual. That is, second steering control circuit 52A controls steering angle θw of steered wheels 15 based on steering angle θs detected via steering angle sensor 24. For this reason, there is a risk that steered wheels 15 will be automatically steered as steering wheel 11 automatically rotates. This steering is unintended by the driver.

[0077] This event may also occur when only first reaction force control circuit 41A of first system circuit 41 is reset. Also, as shown in Figure 4(b), this event may also occur when both second reaction force control circuit 42A and second turning control circuit 52A of second system circuits 42, 52 are reset. Also, this event may also occur when both first reaction force control circuit 41A and first turning control circuit 51A of first system circuits 41, 51 are reset.

[0078] Therefore, each control circuit (41A, 42A, 51A, 52A) executes a process to deal with the reset. <Reaction force control circuit processing> Next, a description will be given of the process for dealing with a reset, which is executed by the first reaction force control circuit 41A and the second reaction force control circuit A. The process for dealing with a reset has two processing patterns.

[0079] <First processing pattern> First, the first processing pattern will be described. As shown in Figure 5(a), here we take the example of a case where only the second reaction force control circuit 42A is reset while each control circuit is executing normal control, while the other three control circuits (41A, 51A, 52A) continue to execute normal control.

[0080] As shown by arrow A1 in FIG. 5(a), the second reaction force control circuit 42A restarts after the reset is complete. The restarted second reaction force control circuit 42A starts performing an initial check. The first reaction force control circuit 41A, which has not been reset, checks the state of the second reaction force control circuit 42A when the second reaction force control circuit 42A restarts. The first reaction force control circuit 41A can recognize the state of the second reaction force control circuit 42A through communication.

[0081] When the value of the flag stored in the memory of the second reaction force control circuit 42A is "1," the first reaction force control circuit 41A determines that the second reaction force control circuit 42A does not need to continue executing the startup sequence. This is because a flag value of "1" indicates that the startup sequence has been completed successfully. Successful completion of the startup sequence includes successful completion of the midpoint learning process and the steering angle synchronization process. Therefore, a flag value of "1" indicates that the steering neutral position of the steering wheel 11 stored in the memory is valid and can be used to control the reaction force motor 21. The second reaction force control circuit 42A can recognize the determination result of the first reaction force control circuit 41A through communication.

[0082] The second reaction force control circuit 42A may be configured to check the value of the flag stored in its own memory when it is restarted by resetting. As shown by arrow A2 in Figure 5(a), when it is determined that there is no need to continue executing the startup sequence, the second reaction force control circuit 42A transitions to the same control state as the first reaction force control circuit 41A without performing the midpoint learning process and the steering angle synchronization process.

[0083] The second reaction force control circuit 42A can recognize the control state of the first reaction force control circuit 41A through communication. Here, the control state of the first reaction force control circuit 41A is the normal control state. Therefore, the second reaction force control circuit 42A transitions its own control state to the normal control state. This allows the first reaction force control circuit 41A and the second reaction force control circuit 42A to once again cooperate to control the drive of the reaction force motor 21.

[0084] It is also possible that only the second reaction force control circuit 42A is reset when each control circuit is waiting for the assist to start. The other three control circuits (41A, 51A, 52A) are also waiting for the assist to start. In this case, the second reaction force control circuit 42A executes the same processing as when it is reset during normal control.

[0085] As shown by arrow A3 in Figure 5(b), the second reaction force control circuit 42A restarts after the reset is complete. The restarted second reaction force control circuit 42A starts performing an initial check. The first reaction force control circuit 41A, which has not been reset, checks the state of the second reaction force control circuit 42A when the second reaction force control circuit 42A restarts.

[0086] As shown by arrow A4 in Figure 5(b), when it is determined that there is no need to continue executing the startup sequence, the second reaction force control circuit 42A transitions to the same control state as the first reaction force control circuit 41A without performing the midpoint learning process and the steering angle synchronization process.

[0087] Here, the control state of the first reaction force control circuit 41A is a state of waiting for the assist to start. Therefore, the second reaction force control circuit 42A transitions its control state to the state of waiting for the assist to start. When the powertrain start process by the vehicle control device 60 is completed, the first reaction force control circuit 41A and the second reaction force control circuit 42A transition to the normal control state.

[0088] When only the first reaction force control circuit 41A is reset, the reset first reaction force control circuit 41A executes the same processing as when only the second reaction force control circuit 42A is reset.

[0089] <Second processing pattern> Next, the second processing pattern will be described. As shown in Figure 6(a), here too, we will take the example of a case where only the second reaction force control circuit 42A is reset while each control circuit is executing normal control, while the other three control circuits (41A, 51A, 52A) continue to execute normal control.

[0090] As shown by arrow A5 in Figure 5(a), the second reaction force control circuit 42A restarts after the reset is complete. The restarted second reaction force control circuit 42A starts performing an initial check. The first reaction force control circuit 41A, which has not been reset, checks the state of the second reaction force control circuit 42A when the second reaction force control circuit 42A restarts.

[0091] When the value of the flag stored in the memory of the second reaction force control circuit 42A is "0," the first reaction force control circuit 41A determines that the second reaction force control circuit 42A needs to continue executing the startup sequence. This is because a flag value of "0" indicates that the startup sequence has not been completed normally. The fact that the startup sequence has not been completed normally includes the fact that the midpoint learning process and the steering angle synchronization process have not been completed normally. Therefore, a flag value of "0" indicates that the steering neutral position of the steering wheel 11 stored in the memory is invalid and cannot be used to control the reaction force motor 21.

[0092] When the value of the flag stored in the memory of the second reaction force control circuit 42A is "0," the first reaction force control circuit 41A executes a predetermined process as a fail-safe. That is, the first reaction force control circuit 41A executes a process to stop the operation of the second system circuits 42, 52. This is to prevent interference between the control of the second reaction force control circuit 42A, which attempts to continue execution of the startup sequence, and the control of the first reaction force control circuit 41A, which attempts to continue normal control. This is also to prevent the steering wheel 11 from automatically rotating due to the second reaction force control circuit 42A continuing execution of the startup sequence.

[0093] When the value of the flag stored in the memory of the second reaction force control circuit 42A is "0," the first reaction force control circuit 41A turns on, for example, a stop request signal S2. Turning on the stop request signal S2 indicates a request to the second reaction force control circuit 42A to stop operation. The stop request signal S2 may be a flag.

[0094] As shown by arrow A6 in FIG. 6(a), when the stop request signal S2 is ON, the second reaction force control circuit 42A executes stop control to stop its own operation without continuing execution of the startup sequence. Stopping the operation of the second reaction force control circuit 42A also stops the power supply to the second winding group N12 of the reaction force motor 21. When a predetermined period has elapsed since the start of execution of the stop control, the second reaction force control circuit 42A turns off its own power supply relay to cut off the power supply to itself. This stops the operation of the second reaction force control circuit 42A. Therefore, mutual interference between the control of the first reaction force control circuit 41A and the control of the second reaction force control circuit 42A is avoided. Furthermore, because the second reaction force control circuit 42A does not continue execution of the startup sequence, the steering wheel 11 does not automatically rotate.

[0095] Through communication with second reaction force control circuit 42A, second turning control circuit 52A recognizes that stop request signal S2 has been turned on. When stop request signal S2 is on, second turning control circuit 52A executes stop control to stop its own operation. Stopping the operation of second turning control circuit 52A also stops the supply of power to second system winding group N22 of steering motor 31. When a predetermined period has elapsed since the start of execution of stop control, second turning control circuit 52A turns off its own power supply relay to cut off the supply of power to itself. This causes second turning control circuit 52A to stop operation.

[0096] After the operation of second reaction force control circuit 42A and second turning control circuit 52A stops, control of reaction force motor 21 and turning motor 31 continues only by first system circuits 41, 51. That is, the drive mode of reaction force motor 21 and turning motor 31 transitions to a single-system drive mode by the first system. The first system is a system in which a reset has not occurred.

[0097] It is also possible that only the second reaction force control circuit 42A is reset when each control circuit is waiting for the assist to start. The other three control circuits (41A, 51A, 52A) are also waiting for the assist to start. In this case, the second reaction force control circuit 42A executes the same processing as when it is reset during normal control.

[0098] As shown by arrow A7 in Figure 6(b), the second reaction force control circuit 42A restarts after the reset is complete. The restarted second reaction force control circuit 42A starts performing an initial check. The first reaction force control circuit 41A, which has not been reset, checks the state of the second reaction force control circuit 42A when the second reaction force control circuit 42A restarts.

[0099] When the value of the flag stored in the memory of the second reaction force control circuit 42A is "0", the first reaction force control circuit 41A determines that the second reaction force control circuit 42A is in a state where it is necessary to continue executing the startup sequence, and turns on the stop request signal S2.

[0100] As shown by arrow A8 in Figure 6(b), when the stop request signal S2 is on, the second reaction force control circuit 42A executes stop control to stop its own operation without continuing to execute the startup sequence.

[0101] The second steering control circuit 52A recognizes that the stop request signal S2 has been turned on through communication with the second reaction force control circuit 42A. When the stop request signal S2 is on, the second steering control circuit 52A executes stop control to stop its own operation.

[0102] After the operation of second reaction force control circuit 42A and second turning control circuit 52A stops, control of reaction force motor 21 and turning motor 31 continues using only first system circuits 41, 51. In other words, the drive mode of reaction force motor 21 and turning motor 31 transitions to a single-system drive mode using the first system.

[0103] When only the first reaction force control circuit 41A is reset, the reset first reaction force control circuit 41A executes the same processing as when only the second reaction force control circuit 42A is reset.

[0104] <Effects of the embodiment> According to this embodiment, the following effects can be obtained. (1) When one of the two reaction force control circuits (41A, 42A) is reset, the reset reaction force control circuit will not continue executing the startup sequence when restarting after the reset is complete if information indicating that the startup sequence has been completed successfully remains. The startup sequence includes processing that requires automatic rotation of the steering wheel 11. Since the execution of this startup sequence is not continued, unintended behavior of the steering wheel 11 or the steered wheels 15 can be suppressed. Note that the fact that information indicating that the startup sequence has been completed successfully remains means that the flag value remains set to "1."

[0105] (2) When the reset reaction force control circuit is restarted after the reset is complete, if information indicating that the startup sequence has been completed successfully remains, the reset reaction force control circuit does not continue execution of the startup sequence and transitions its own control state to the control state of the reaction force control circuit that has not been reset. Therefore, after the reset of the reset reaction force control circuit is complete, the two reaction force control circuits can once again cooperate to control the reaction force motor 21.

[0106] (3) When the reset reaction force control circuit is restarted after the reset is complete, if there is no information remaining indicating that the startup sequence has been completed successfully, the reset reaction force control circuit stops its operation without executing the startup sequence. Therefore, after the reset of the reset reaction force control circuit is complete, the reset reaction force control circuit does not continue to execute the startup sequence. Therefore, unintended behavior of the steering wheel 11 or the steered wheels 15 caused by the execution of the startup sequence can be suppressed. Note that the absence of information remaining indicating that the startup sequence has been completed successfully means that the flag value remains set to "0."

[0107] (4) When restarting a reset reaction force control circuit, if no information remains indicating that the startup sequence has been completed normally, the reaction force control circuit that has not been reset executes processing to stop the operation of the reset reaction force control circuit and the steering control circuit (51A or 52A) of the same system as the reset reaction force control circuit, from a fail-safe perspective. This processing involves, for example, switching stop request signal S2 from off to on. Therefore, after the operation of the reaction force control circuit and steering control circuit of the system in which the reset occurred has stopped, the reaction force control circuit and steering control circuit of the system in which the reset occurred can continue to control reaction force motor 21 and steering motor 31.

[0108] (5) The startup sequence includes a midpoint learning process and a steering angle synchronization process. The midpoint learning process and the steering angle synchronization process are examples of processes that require automatic rotation of the steering wheel 11. If the startup sequence includes the midpoint learning process and the steering angle synchronization process, there is a risk that the steering wheel 11 will automatically rotate when the reaction force control circuit is started. This embodiment is suitable for cases where the startup sequence includes the midpoint learning process and the steering angle synchronization process.

[0109] <Other embodiments> This embodiment may be modified as follows. The contents of the startup sequence executed by the first reaction force control circuit 41A and the second reaction force control circuit 42A at startup may be changed as appropriate. The startup sequence may include processes other than the midpoint learning process and the steering angle synchronization process as processes required to automatically rotate the steering wheel 11.

[0110] When restarting a reset reaction force control circuit (41A or 42A), it is determined whether it is necessary to continue executing the startup sequence during the period from when the initial check begins to when the midpoint learning process begins. However, it may also be possible to determine whether it is necessary to execute the startup sequence before the initial check begins to when restarting a reset reaction force control circuit. In this way, it is possible to determine at an earlier timing whether to transition the control state of the reset reaction force control circuit to the control state of a reaction force control circuit that has not been reset, or to stop the operation of the reset reaction force control circuit. [Explanation of symbols]

[0111] 11...Steering wheel 15...Steering wheel 21...Reaction motor 31...Steering motor 40...Reaction force control device constituting the steering control device 41A...First reaction force control circuit 42A...Second reaction force control circuit 50... Steering control device constituting the steering control device 51A...First steering control circuit 52A...Second steering control circuit

Claims

1. two reaction force control circuits configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel whose power transmission is separated from that of steered wheels of a vehicle; the reaction force control circuit is configured to, upon startup, execute a preparatory process including a process required to automatically rotate the steering wheel via the reaction force motor, and upon completion of execution of the preparatory process, store information indicating whether the preparatory process has been completed successfully; A steering control device configured such that when either of the two reaction force control circuits is reset, the reset reaction force control circuit will not execute the preparation process when restarted after the reset is complete if the information indicating that the preparation process has been completed successfully remains.

2. 2. The steering control device according to claim 1, wherein the reset reaction force control circuit is configured to transition its own control state to the control state of the reaction force control circuit that has not been reset without executing the preparation process when the reset reaction force control circuit is restarted after the reset is complete and the information indicating that the preparation process has been completed normally remains.

3. 3. A steering control device according to claim 1 or claim 2, wherein the reset reaction force control circuit is configured to stop its own operation without executing the preparation process when the information indicating that the preparation process has been completed successfully does not remain when the reaction force control circuit is restarted after the reset is complete.

4. The vehicle further includes two steering control circuits configured to control a steering motor that generates a steering force for steering the steered wheels, 4. The steering control device according to claim 3, wherein the reaction force control circuit that has not been reset is configured to execute processing to stop operation of the reset reaction force control circuit and the steering control circuit of the same system as the reset reaction force control circuit when the information indicating that the preparation processing has been completed normally does not remain when the reset reaction force control circuit is restarted.

5. the preparation process includes a midpoint learning process for learning a steering neutral position of the steering wheel by automatically rotating the steering wheel through driving of the reaction motor; 3. The steering control device according to claim 1, further comprising a steering angle synchronization process for correcting the rotational position of the steering wheel so that the rotational position of the steering wheel corresponds to the steered position of the steered wheels.

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