Steering control device

Abstract

To provide a steering control device that is able to properly inform a driver of a vehicle that output from a steering motor is limited.SOLUTION: A steering control device has a reaction force control unit and a turning control unit. The reaction force control unit controls a reaction force motor that generates a steering reaction force applied to a steering wheel. The turning control unit controls a turning motor that generates a turning force for turning a turning wheel. When an event in which output from the steering motor is limited occurs, the reaction force control unit executes reaction force change processing in which the steering reaction force is changed according to a content of the event.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, a so-called steer-by-wire type steering device that separates the power transmission between the steering wheel and the steered wheels is known. This steering device has a reaction force motor that is a source of the steering reaction force applied to the steering shaft, and a steering motor that is a source of the steering force for steering the steered wheels. When the vehicle is running, the control device of the steering device generates a steering reaction force through the reaction force motor and steers the steered wheels through the steering motor.

[0003] For example, when the output limit condition is satisfied, the control device of Patent Document 1 executes an output limit process for limiting the output of the steering motor and a reaction force increase process for increasing the steering reaction force. The output limit condition includes that the temperature of the steering motor exceeds a temperature threshold value, or the voltage supplied from the power supply device to the steering motor is less than a voltage threshold value. In synchronization with the limitation of the output of the steering motor, the steering reaction force increases. Therefore, the driver can recognize that there is a possibility that the steering followability of the steered wheels may decrease due to the feel transmitted through the steering wheel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the control device of Patent Document 1 limits the output of the steering motor, it simply increases the steering reaction force. It is required to appropriately notify the driver of the vehicle that the output of the steering motor is limited.

Means for Solving the Problems

[0006] The steering control device capable of solving the above problems is configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel in which power transmission to a steered wheel of a vehicle is separated, and a steering control unit configured to control a steering motor that generates a steering force for steering the steered wheel. When an event in which the output of the steering motor is restricted occurs, the reaction force control unit is configured to execute a reaction force change process for changing the steering reaction force according to the content of the event.

[0007] According to this configuration, when an event in which the output of the steering motor is restricted occurs, the steering reaction force is changed according to the content of the event. Therefore, as a feel through the steering wheel, different steering sensations corresponding to the content of the event in which the output of the steering motor is restricted can be given to the driver of the vehicle. Therefore, the driver of the vehicle can recognize that the output of the steering motor is restricted, and thus the content of the event in which the output of the steering motor is restricted, by feeling the steering reaction force through the steering wheel. Therefore, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor is restricted.

[0008] In the above steering control device, the reaction force control unit may be configured to execute a process of calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on a first state variable reflecting the steering state of the steering wheel, and calculating an axial force acting on a steering shaft that steers the steered wheel based on a second state variable reflecting the steering state of the steered wheel, and calculating an axial force torque by converting the calculated axial force into a torque with respect to the steering wheel, and a process of calculating a reaction force torque command value, which is a target value of the steering reaction force, by subtracting the axial force torque from the assist torque command value. In this case, the reaction force change process may include a process of changing the assist torque command value and a process of changing the axial force torque.

[0009] As described above, when an event occurs in which the output of the steering motor is restricted, by changing the assist torque command value and the axial force torque, the steering reaction force can be changed according to the content of the event in which the output of the steering motor is restricted.

[0010] In the above steering control device, the first state variable may be the steering torque applied to the steering wheel. In this case, the process of changing the assist torque command value may be a process of restricting the steering torque detected by the torque sensor according to the content of the event.

[0011] As described above, when an event occurs in which the output of the steering motor is restricted, by restricting the steering torque detected by the torque sensor according to the content of the event, the assist torque command value can be changed according to the content of the event.

[0012] In the above steering control device, the second state variable may include the current of the steering motor and the target rotation angle of the pinion shaft that rotates in conjunction with the steering shaft. The axial force may include a mixed axial force obtained by mixing a current axial force corresponding to the value of the current of the steering motor and an angular axial force corresponding to the target rotation angle of the pinion shaft. In this case, when the event occurs, the reaction force control unit may be configured to execute a process of switching the axial force from the mixed axial force to the angular axial force.

[0013] According to this configuration, when the output of the steering motor is restricted, the axial force used in the calculation of the axial force torque is switched from the mixed axial force to the angular axial force. Since the angular axial force is not affected by the current of the steering motor, it is possible to apply a more appropriate steering reaction force to the steering wheel.

[0014] In the above-described steering control device, when the event occurs, the reaction force control unit may be configured to execute a process of adjusting the assist torque command value so as to conform to a normal state in which the output of the steering motor is not restricted when switching the axial force from the combined axial force to the angular axial force.

[0015] The value of the angular axial force immediately after switching from the combined axial force to the angular axial force may vary with respect to the value of the combined axial force immediately before switching from the combined axial force to the angular axial force. In this regard, according to the above configuration, when the output of the steering motor is restricted, the assist torque command value is adjusted so as to conform to a normal state in which the output of the steering motor is not restricted. The steering reaction force is also adjusted in accordance with the adjustment of the assist torque command value. Therefore, it is possible to suppress fluctuations in the steering reaction force due to the axial force difference generated before and after the axial force used in the calculation of the axial force torque is switched from the combined axial force to the angular axial force.

[0016] In the above-described steering control device, the reaction force control unit may be configured to calculate a basic assist torque that is the basis for calculating the assist torque command value based on the first state variable, and calculate the assist torque command value by multiplying the calculated basic assist torque by a gain corresponding to the vehicle speed. In this case, the process of adjusting the assist torque command value may be a process of adjusting the value of the gain so that the assist torque command value conforms to a normal state in which the output of the steering motor is not restricted.

[0017] According to this configuration, when the output of the steering motor is restricted, the value of the gain is adjusted so that the assist torque command value conforms to a normal state in which the output of the steering motor is not restricted. As a result, the assist torque command value conforms to a normal state in which the output of the steering motor is not restricted. For this reason, it is possible to suppress fluctuations in the steering reaction force due to the axial force difference generated before and after the axial force used in the calculation of the axial force torque is switched from the combined axial force to the angular axial force.

[0018] In the above-described steering control device, the axial force may be an axial force obtained by adding a deviation compensation axial force corresponding to an angular deviation, which is a difference between the steering angle of the steering wheel converted from the steering angle of the steering wheel and the rotation angle of the pinion shaft, to the hybrid axial force. In this case, when the event occurs, the reaction force control unit may be configured to execute a process of increasing the value of the deviation compensation axial force as compared with a normal state in which the output of the steering motor is not restricted.

[0019] When the output of the steering motor is restricted, the steering followability of the steered wheels with respect to the steering of the steering wheel decreases. According to the above configuration, when an event in which the output of the steering motor is restricted occurs, the value of the deviation compensation axial force increases as compared with a normal state in which the output of the steering motor is not restricted. Therefore, it is possible to reflect a decrease in the steering followability of the steered wheels with respect to the steering of the steering wheel in the steering reaction force.

[0020] In the above-described steering control device, the event includes an abnormality of the vehicle or the steering motor, and the reaction force control unit may be configured to increase the steering reaction force as the degree of the abnormality increases.

[0021] According to this configuration, when an abnormality occurs in the vehicle or the steering motor, the steering reaction force increases as the degree of the abnormality increases. Therefore, the driver of the vehicle can recognize that an abnormality has occurred in the vehicle or the steering motor, and thus the degree of the abnormality, by feeling the steering reaction force transmitted through the steering wheel as a tactile sensation.

Effects of the Invention

[0022] According to the steering control device of the present invention, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor is restricted.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0024] Hereinafter, an embodiment of a steering control device will be described. <Overall Configuration> As shown in FIG. 1, the control target of the steering control device 1 is a steer-by-wire type steering device 2. The steering device 2 has a steering mechanism 3 and a steering mechanism 4. The steering mechanism 3 is a mechanism part that is steered by a driver via a steering wheel 5. The steering mechanism 4 is a mechanism part that steers the steered wheels 6 of the vehicle in response to the steering of the steering wheel 5. The steering control device 1 includes a reaction force control device 1A and a steering control device 1B. The control target of the reaction force control device 1A is the steering mechanism 3. The reaction force control device 1A executes reaction force control. The reaction force control device 1A corresponds to a reaction force control unit. The control target of the steering control device 1B is the steering mechanism 4. The steering control device 1B executes steering control. The steering control device 1B corresponds to a steering control unit.

[0025] The steering mechanism 3 includes a steering shaft 11, a reaction force motor 12, and a speed reducer 13. The steering wheel 5 is integrally rotatably connected to the steering shaft 11. The reaction force motor 12 is a source of the steering reaction force applied to the steering shaft 11. The steering reaction force is a force in the direction opposite to the steering direction of the steering wheel 5. The reaction force motor 12 is, for example, a three-phase brushless motor. The speed reducer 13 reduces the rotation of the reaction force motor 12 and transmits the reduced rotation to the steering shaft 11.

[0026] The steering gear mechanism 4 includes a pinion shaft 21, a steering shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. Also, the housing 23 reciprocally accommodates the steering shaft 22. The power transmission between the steering shaft 22 and the steering wheel 5 is separated. The pinion shaft 21 is provided so as to intersect the steering shaft 22. The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22. Tie rods 25 are connected to both ends of the steering shaft 22 via rack ends 24 composed of ball joints. The tip of the tie rod 25 is connected to a knuckle (not shown) to which the steering wheel 6 is assembled.

[0027] The steering gear mechanism 4 includes a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is a source of the steering force applied to the steering shaft 22. The steering force is a force for steering the steering wheel 6. The steering motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt transmission mechanism. The transmission mechanism 32 transmits the rotation of the steering motor 31 to the conversion mechanism 33. The conversion mechanism 33 is, for example, a ball screw mechanism. The conversion mechanism 33 converts the rotation transmitted through the transmission mechanism 32 into the axial movement of the steering shaft 22.

[0028] When the steering shaft 22 moves axially, the steering angle θ of the steering wheel 6 wis changed. The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22. For this reason, the pinion shaft 21 rotates in conjunction with the movement of the steering shaft 22. The pinion shaft 21 is a shaft or a rotating body that rotates in conjunction with the steering operation of the steering wheel 6.

[0029] The reaction force control device 1A controls the operation of the reaction force motor 12. The reaction force control device 1A has a processing circuit including any one of the following three configurations A1, A2, and A3. A1. One or more processors that operate according to a computer program which is software. The processor includes a CPU (central processing unit) and a memory.

[0030] A2. One or more dedicated hardware circuits such as an application specific integrated circuit (ASIC) that executes at least a part of various processes. The ASIC includes a CPU and a memory.

[0031] A3. A hardware circuit combining configurations A1 and A2. The memory is a computer-readable medium that stores a program describing processing or instructions for the computer. In the present embodiment, the computer is a CPU. The memory includes a RAM (random access memory) and a ROM (read only memory). The CPU executes various controls by executing the program stored in the memory at a determined operation cycle.

[0032] The reaction force control device 1A takes in the detection results of in-vehicle sensors. The sensors include a vehicle speed sensor 41, a torque sensor 42, and a rotation angle sensor 43. The vehicle speed sensor 41 detects the vehicle speed V. The vehicle speed V is a state variable that reflects the driving state of the vehicle. The torque sensor 42 is provided on the steering shaft 11. The torque sensor 42 is located on the steering wheel 5 side with respect to the connection portion of the speed reducer 13 in the steering shaft 11. The torque sensor 42 detects the steering torque Th applied to the steering shaft 11. The steering torque Th is calculated based on the amount of twist of the torsion bar 42a provided on the steering shaft 11. The steering torque Th is an example of a first state variable that reflects the steering state of the steering wheel 5. The rotation angle sensor 43 is provided on the reaction force motor 12. The rotation angle sensor 43 detects the rotation angle θ a of the reaction force motor 12.

[0033] The steering torque Th and the rotation angle θ of the reaction force motor 12 a are, for example, positive values when the steering wheel 5 is steered to the right, and negative values when the steering wheel 5 is steered to the left.

[0034] The reaction force control device 1A controls the operation of the reaction force motor 12 using the detection results of the vehicle speed sensor 41, the torque sensor 42, and the rotation angle sensor 43. The reaction force control device 1A controls the power supply to the reaction force motor 12 so as to generate a steering reaction force corresponding to the steering torque Th in the reaction force motor 12.

[0035] The steering control device 1B controls the operation of the steering motor 31. The steering control device 1B has a processing circuit including any one of the previous three configurations A1, A2, and A3, similar to the reaction force control device 1A.

[0036] The steering control device 1B captures the detection results of in-vehicle sensors. The sensors include the rotation angle sensor 44. The rotation angle sensor 44 is provided on the steering motor 31. The rotation angle sensor 44 detects the rotation angle θ b of the steering motor 31. The rotation angle θ of the steering motor 31 bFor example, it is a positive value when the steering wheel 5 is steered to the right, and a negative value when the steering wheel 5 is steered to the left.

[0037] The steering control device 1B controls the operation of the steering motor 31 using the detection result of the rotation angle sensor 44. The steering control device 1B controls the power supply to the steering motor 31 so that the steered wheels 6 are steered according to the steering state of the steering wheel 5.

[0038] <Configuration of the reaction force control device 1A> Next, the configuration of the reaction force control device 1A will be described. As shown in FIG. 2, the reaction force control device 1A includes a steering angle calculation unit 51, a reaction force torque command value calculation unit 52, and a power supply control unit 53.

[0039] The steering angle calculation unit 51 calculates the steering angle θ of the steering wheel 5 based on the rotation angle θ of the reaction force motor 12 detected through the rotation angle sensor 43. a Based on s it calculates the steering angle θ of the steering wheel 5. The reaction force torque command value calculation unit 52 calculates a reaction force torque command value T based on the steering torque Th and the vehicle speed V. The reaction force torque command value T is the target value of the steering reaction force to be generated in the reaction force motor 12. The steering reaction force is a torque in the direction opposite to the steering direction of the steering wheel 5. The absolute value of the reaction force torque command value T becomes larger as the absolute value of the steering torque Th is larger and as the vehicle speed V is slower. * The reaction force torque command value T * is the target value of the steering reaction force to be generated in the reaction force motor 12. The steering reaction force is a torque in the direction opposite to the steering direction of the steering wheel 5. The absolute value of the reaction force torque command value T becomes larger as the absolute value of the steering torque Th is larger and as the vehicle speed V is slower. * becomes larger.

[0040] The power supply control unit 53 supplies power corresponding to the reaction force torque command value T to the reaction force motor 12. Specifically, the power supply control unit 53 calculates a current command value for the reaction force motor 12 based on the reaction force torque command value T. The power supply control unit 53 detects the value of the current I generated in the power supply path through a current sensor 54 provided in the power supply path to the reaction force motor 12. * The power supply control unit 53 supplies power corresponding to the reaction force torque command value T to the reaction force motor 12. Specifically, the power supply control unit 53 calculates a current command value for the reaction force motor 12 based on the reaction force torque command value T. * Based on the reaction force torque command value T a it calculates a current command value for the reaction force motor 12. The power supply control unit 53 detects the value of the current I generated in the power supply path through a current sensor 54 provided in the power supply path to the reaction force motor 12. aThe value is the value of the current supplied to the reaction force motor 12. The energization control unit 53 calculates the deviation between the current command value and the value of the current I a and controls the power supply to the reaction force motor 12 so as to eliminate the deviation. As a result, the reaction force motor 12 generates a torque corresponding to the reaction force torque command value T * .

[0041] <Configuration of the steering control device 1B> Next, the configuration of the steering control device 1B will be described. As shown in FIG. 2, the steering control device 1B includes a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit 63, an energization control unit 64, a current sensor 65, and a current limit processing unit 66.

[0042] The pinion angle calculation unit 61 calculates the pinion angle θ b based on the rotation angle θ p of the steering motor 31 detected through the rotation angle sensor 43. The pinion angle θ p is the rotation angle of the pinion shaft 21. The steering motor 31 and the pinion shaft 21 are interlocked via a transmission mechanism 32, a conversion mechanism 33, and a steering shaft 22. Therefore, there is a correlation between the rotation angle θ b of the steering motor 31 and the pinion angle θ p . Using this correlation, the pinion angle θ b can be obtained from the rotation angle θ p of the steering motor 31. The pinion shaft 21 is meshed with the steering shaft 22. Therefore, there is also a correlation between the pinion angle θ p and the movement amount of the steering shaft 22. That is, the pinion angle θ p is a value that reflects the steering angle θ w of the steering wheel 6.

[0043] The target pinion angle calculation unit 62 calculates the target pinion angle θ s based on the steering angle θ p * calculated by the steering angle calculation unit 51. The target pinion angle θ p *is the target angle of the pinion angle θ p The target pinion angle calculation unit 62 calculates the target pinion angle θ p * so as to achieve the steering angle ratio set according to product specifications and the like. The steering angle ratio is the ratio of the steering angle θ s to the swivel angle θ w of the swivel wheel.

[0044] The target pinion angle calculation unit 62 sets the steering angle ratio according to the driving state of the vehicle such as the vehicle speed V, for example, and calculates the target pinion angle θ p * according to the set steering angle ratio. As the vehicle speed V decreases, the target pinion angle calculation unit 62 calculates the target pinion angle θ s so that the swivel angle θ w with respect to the steering angle θ p * increases. As the vehicle speed V increases, the target pinion angle calculation unit 62 calculates the target pinion angle θ s so that the swivel angle θ w with respect to the steering angle θ p * decreases. The target pinion angle calculation unit 62 calculates a correction angle with respect to the steering angle θ s in order to achieve the steering angle ratio set according to the driving state of the vehicle, and adds the calculated correction angle to the steering angle θ s to calculate the target pinion angle θ p * corresponding to the steering angle ratio. The target pinion angle θ p * is the target rotation angle of the pinion shaft 21 and is an example of a second state variable reflecting the swivel state of the swivel wheel 6.

[0045] Depending on product specifications and the like, the target pinion angle calculation unit 62 may calculate the target pinion angle θ p * so that the steering angle ratio becomes "1:1" regardless of the driving state of the vehicle.

[0046] The pinion angle feedback control unit 63 is the target pinion angle θ calculated by the target pinion angle calculation unit 62p * and the pinion angle θ calculated by the pinion angle calculation unit 61 p is captured. The pinion angle feedback control unit 63 calculates the steering torque command value T p so that the pinion angle θ p * follows the target pinion angle θ p through the feedback control of the pinion angle θ p * . The steering torque command value T p * is a command value for the torque generated by the steering motor 31 and is a target value of the steering force.

[0047] The energization control unit 64 supplies power corresponding to the steering torque command value T p * to the steering motor 31. Specifically, the energization control unit 64 calculates a current command value for the steering motor 31 based on the steering torque command value T p * . The current sensor 65 is provided in the power supply path for the steering motor 31. The energization control unit 64 detects the value of the current I b generated in the power supply path for the steering motor 31 through the current sensor 65. The value of the current I b is the value of the current supplied to the steering motor 31 and is an example of a second state variable reflecting the steering state of the steering wheel 6. The energization control unit 64 obtains the deviation between the current command value and the value of the current I b and controls the power supply to the steering motor 31 so as to eliminate the deviation. As a result, the steering motor 31 generates a torque corresponding to the steering torque command value T p * .

[0048] The current limit processing unit 66 determines whether a specific event has occurred. The specific event is an event that should limit the output of the steering motor 31, that is, the steering operation of the steering wheel 6, and is, for example, the following first to fourth events B1 to B4.

[0049] B1. The temperature of the steering motor 31 rises excessively. B2. The voltage input to the steering control device 1B decreases. B3. A high load is continuously applied to the steering motor 31.

[0050] B4. The drive mode of the steering motor 31 is a single-system drive mode. When the first determination condition is satisfied, the current limit processing unit 66 determines that the first event B1 has occurred. The first determination condition includes, for example, the temperature T of the steering motor 31 detected through a temperature sensor m exceeding a temperature threshold. However, the current limit processing unit 66 may calculate the temperature of the steering motor 31 based on the value of the current I of the steering motor 31 b or the integrated value of the value of the current I. b

[0051] When the second determination condition is satisfied, the current limit processing unit 66 determines that the second event B2 has occurred. The second determination condition includes, for example, the voltage V input to the steering control device 1B b falling below a voltage threshold. The voltage V b is the drawing-in voltage from the in-vehicle battery to the steering control device 1B. However, it may be conditioned that the value of the voltage of the battery detected through a voltage sensor falls below the voltage threshold. The battery is the main power source of the vehicle.

[0052] When the third determination condition is satisfied, the current limit processing unit 66 determines that the third event has occurred. The third determination condition includes, for example, the value of the current I supplied to the steering motor 31 b exceeding a current threshold and continuing for a predetermined time. The third event occurs, for example, when the steering wheel 6 hits an obstacle such as a curb during parking or when an end hit of the steering shaft 22 occurs. An end hit is when the rack end 24, which is the end of the steering shaft 22, hits the housing 23.

[0053] ​When the fourth determination condition is satisfied, the current limiting processing unit 66 determines that the fourth event B4 has occurred. The fourth determination condition includes, for example, when the reaction force motor 12 and the steering motor 31 each have two winding groups, the determination that an abnormality has been confirmed in one of the two power supply systems for the steering motor 31, or the determination that an abnormality has been confirmed in one of the two control systems for the steering motor 31, or the determination that the drive mode of the reaction force motor 12 has transitioned from the cooperative drive mode to the single-system drive mode.

[0054] When the reaction force motor 12 has two winding groups, the reaction force control device 1A has two power supply systems for the reaction force motor 12 and two control systems for the reaction force motor 12. The power supply system includes a motor drive circuit. The control system includes a CPU and various sensors. When an abnormality is detected in one of the two power supply systems or in one of the two control systems, the reaction force control device 1A transitions the drive mode of the steering motor 31 from the cooperative drive mode to the single-system drive mode.

[0055] When the steering motor 31 has two winding groups, the steering control device 1B has two power supply systems for the steering motor 31 and two control systems for the steering motor 31. The power supply system includes a motor drive circuit. The control system includes a CPU and various sensors. When an abnormality is detected in one of the two power supply systems or in one of the two control systems, the steering control device 1B transitions the drive mode of the steering motor 31 from the cooperative drive mode to the single-system drive mode.

[0056] The reaction force control device 1A and the steering control device 1B synchronize the drive mode of the reaction force motor 12 and the drive mode of the steering motor 31. That is, when the drive mode of the steering motor 31 transitions from the cooperative drive mode to the single-system drive mode, the reaction force control device 1A transitions the drive mode of the reaction force motor 12 from the cooperative drive mode to the single-system drive mode. When the drive mode of the reaction force motor 12 transitions from the cooperative drive mode to the single-system drive mode, the steering control device 1B transitions the drive mode of the steering motor 31 from the cooperative drive mode to the single-system drive mode.

[0057] The coordinated drive mode is a drive mode when both systems are normal, and it is a drive mode in which the winding groups of the two systems generate equal torque respectively. The single-system drive mode is a drive mode when an abnormality in either one of the two systems is confirmed and there is no possibility of normal recovery. In the single-system mode, torque is generated by the winding group of the system in which no abnormality has been detected.

[0058] When it is determined that a specific event (B1 to B4) has occurred, the current limiting processing unit 66 executes current limiting processing for the steering motor 31. The current limiting processing is an example of output limiting processing for limiting the output of the steering motor 31, and is processing for limiting the current supplied to the steering motor 31. Specifically, the current limiting processing unit 66 calculates a limit value I lim for limiting the amount of current supplied to the steering motor 31. The limit value I lim is the upper limit value of the amount of current supplied to the steering motor 31. The limit value I lim is, for example, a value of current set based on the viewpoint of protecting the steering motor 31 from overheating or the viewpoint of limiting the voltage drop of the battery by limiting the current of the steering motor 31 at a determined limiting ratio.

[0059] When the limit value I lim is calculated by the current limiting processing unit 66, the energization control unit 64 limits the amount of current supplied to the steering motor 31 according to the limit value I lim . The energization control unit 64 compares the absolute value of the current to be supplied to the steering motor 31 with the limit value I lim . When the absolute value of the current to be supplied to the steering motor 31 is greater than the limit value I lim , the energization control unit 64 limits the absolute value of the current supplied to the steering motor 31 to the limit value I lim . When the absolute value of the current to be supplied to the steering motor 31 is less than or equal to the limit value I lim , the energization control unit 64 supplies the original current calculated through the feedback control of the current I b to the steering motor 31 as it is.

[0060] The current limit processing unit 66 sets the value of the current limit flag F according to the determination result as to whether a specific event has occurred. When it is determined that none of the first to fourth events B1 to B4 has occurred, the current limit processing unit 66 sets the value of the current limit flag F lim to "0". When it is determined that the first event B1 has occurred, the current limit processing unit 66 sets the value of the current limit flag F lim to "1". When it is determined that the second event B2 has occurred, the current limit processing unit 66 sets the value of the current limit flag F lim to "2". When it is determined that the third event B3 has occurred, the current limit processing unit 66 sets the value of the current limit flag F lim to "3". When it is determined that the fourth event B4 has occurred, the current limit processing unit 66 sets the value of the current limit flag F lim to "4". The current limit flag F lim is an electrical signal indicating whether the current limit processing for the steering motor 31 is being executed, and is also an electrical signal including information indicating the content of a specific event. lim is an electrical signal indicating whether the current limit processing for the steering motor 31 is being executed, and is also an electrical signal including information indicating the content of a specific event.

[0061] During the execution of the current limit processing for the steering motor 31, when a defined end condition is satisfied, the current limit processing unit 66 ends the execution of the current limit processing for the steering motor 31. The end condition may be, for example, that the above first to fourth conditions are no longer satisfied, or may be a condition individually set for each of the first to fourth events B1 to B4. When the end condition of the current limit processing is satisfied, the current limit processing unit 66 stops the calculation of the limit value I lim and sets the value of the current limit flag F lim to "0".

[0062] <Configuration of the reaction torque command value calculation unit 52> Next, the configuration of the reaction torque command value calculation unit 52 will be described in detail. As shown in FIG. 3, the reaction torque command value calculation unit 52 includes a steering torque limit processing unit 81, an assist torque command value calculation unit 82, an axial force torque calculation unit 83, a calculator 84, and a command generation unit 85.

[0063] The steering torque limit processing unit 81 takes in the value of the steering torque T detected through the torque sensor 42. h Based on a command from the command generation unit 85, the steering torque limit processing unit 81 executes steering torque limit processing. The steering torque limit processing is a process of limiting the value of the steering torque T in order to limit the output of the steering motor 31. h Through the execution of the steering torque limit processing, the steering torque limit processing unit 81 generates a limited steering torque T by limiting the value of the steering torque T. h The limited steering torque T is the steering torque T after being limited. h_lim h_lim h

[0064] The assist torque command value calculation unit 82 takes in the steering torque T from the steering torque limit processing unit 81 or the limited steering torque T. h Also, the assist torque command value calculation unit 82 takes in the vehicle speed V detected through the vehicle speed sensor 41. h_lim Based on the steering torque T or the limited steering torque T and the vehicle speed V, the assist torque command value calculation unit 82 calculates an assist torque command value T1. h The assist torque command value T1 corresponds to the target value of the assist torque when the steering device 2 is an electric power steering device. h_lim The assist torque is a force for assisting the steering of the steering wheel 5. h The assist torque command value T1 is a torque in the same direction as the steering direction of the steering wheel 5. The absolute value of the assist torque command value T1 becomes larger as the absolute value of the steering torque T is larger and the vehicle speed V is slower.

[0065] The axial force torque calculation unit 83 calculates the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * ​​​The current I of the steering motor 31 detected through the current sensor 65 b and the vehicle speed V detected through the vehicle speed sensor 41 are captured. The axial force torque calculation unit 83 calculates the axial force acting on the steering shaft 22 based on the target pinion angle θ p * the value of the current I of the steering motor 31 b and the vehicle speed V. The axial force torque calculation unit 83 calculates the axial force torque T2 by converting the calculated axial force into the torque with respect to the steering shaft 11.

[0066] The calculator 84 captures the assist torque command value T1 calculated by the assist torque command value calculation unit 82 and the axial force torque T2 calculated by the axial force torque calculation unit 83. The calculator 84 calculates the reaction force torque command value T * by subtracting the axial force torque T2 from the assist torque command value T1.

[0067] The command generation unit 85 captures the value of the current limit flag F lim set by the current limit processing unit 66. The command generation unit 85 generates commands for the steering torque limit processing unit 81, the assist torque command value calculation unit 82, and the axial force torque calculation unit 83 according to the value of the current limit flag F lim . The commands include the first to fourth commands S1 to S4. The first command S1 is a command for the steering torque limit processing unit 81. The second command S2 is a command for the assist torque command value calculation unit 82. The third command S3 and the fourth command S4 are commands for the axial force torque calculation unit 83.

[0068] <Configuration of the steering torque limit processing unit 81> Next, the configuration of the steering torque limit processing unit 81 will be described in detail. The steering torque limit processing unit 81 is capable of executing the first to third limit processes for the steering torque T h . The first to third limit processes are for the steering torque T hThese are processes with different limiting modes for []. The steering torque limiting processing unit 81 executes any one of the first to third limiting processes based on the first command S1 generated by the command generation unit 85.

[0069] <First Limiting Process> As shown in FIG. 4, the first limiting process is a process of limiting the change range of the value of the steering torque T h . The change range of the value of the steering torque T h is, for example, the range between the first upper limit value T h_UL1 and the first lower limit value T h_LL1 . The first upper limit value T h_UL1 is a positive value, and the first lower limit value T h_LL1 is a negative value. The first upper limit value T h_UL1 and the first lower limit value T h_LL1 are limit values for the value of the steering torque T h and are stored in the memory. In FIG. 4, as an example, the value of the steering torque T h changes in a sine wave shape.

[0070] When the value of the steering torque T h is a positive value, the steering torque limiting processing unit 81 compares the value of the steering torque T h with the first upper limit value T h_UL1 . When the value of the steering torque T h exceeds the first upper limit value T h_UL1 , the steering torque limiting processing unit 81 limits the value of the steering torque T h to the first upper limit value T h_UL1 . After being limited to the first upper limit value T h_UL1 , the steering torque T h becomes the limited steering torque T h_lim .

[0071] When the value of the steering torque T h is a negative value, the steering torque limiting processing unit 81 compares the value of the steering torque T h with the first lower limit value T h_LL1 . When the value of the steering torque T h is less than the first lower limit value T h_LL1 , the steering torque Th Limit the value to the first lower limit value T h_LL1 After being limited to the first lower limit value T h_LL1 The steering torque T h becomes the limited steering torque T h_lim .

[0072] Note that the steering torque limiting processing unit 81, when the value of the steering torque T h is within the range between the first upper limit value T h_UL1 and the first lower limit value T h_LL1 , sets the value of the steering torque T h detected through the torque sensor 42 as the value of the limited steering torque T h_lim as it is.

[0073] The assist torque command value calculation unit 82 calculates the assist torque command value T1 using the limited steering torque T h_lim obtained through the first limiting process. However, the absolute value of the assist torque command value T1 is smaller than the assist torque command value T1 calculated using the steering torque T h by the amount by which the value of the steering torque T h is limited. As the absolute value of the assist torque command value T1 becomes smaller, the reaction torque command value T * calculated by the calculator 84, and thus the steering reaction force, becomes larger.

[0074] When the first limiting process is executed, when the steering wheel 5 is steered beyond the small steering angle region, the steering reaction force becomes larger than the original steering reaction force corresponding to the steering torque T h . Therefore, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feeling as if the steering wheel 5 has become heavier. The weight of the steering wheel 5 is the same as the weight of the steering wheel 5 when the assist force is not applied to the steering wheel 5 in the case where the steering device 2 is an electric power steering device that applies an assist force to the steering wheel 5.

[0075] <Second Limiting Process> As shown in FIG. 5, the second limiting process sets a first dead zone for the steering torque T h and, when the value of the steering torque T h reaches a value within the first dead zone, limits the value of the steering torque T h to "0". The first dead zone is a certain range of values of the steering torque T h including "0". The first dead zone is the range between a second upper limit value T h_UL2 and a second lower limit value T h_LL2 . The second upper limit value T h_UL2 is a positive value, and the second lower limit value T h_LL2 is a negative value. The second upper limit value T h_UL2 and the second lower limit value T h_LL2 are limit values for the value of the steering torque T h and are stored in the memory. In FIG. 5, as an example, the value of the steering torque T h changes in a sine wave shape.

[0076] When the value of the input steering torque T h is a positive value, the steering torque limiting processing unit 81 sets the value of the output limited steering torque T h to "0" until the value of the steering torque T h_UL2 exceeds the second upper limit value T h_lim . After the value of the steering torque T h exceeds the second upper limit value T h_UL2 , the steering torque limiting processing unit 81 sets the value of the limited steering torque T h according to the value of the steering torque T h_lim . However, due to the influence of the first dead zone, the value of the limited steering torque T h_lim does not follow the value of the original steering torque T h that changes in a sine wave shape. The value of the limited steering torque T h_lim is smaller than the value of the original steering torque T h .

[0077] When the value of the input steering torque T h is a negative value, the steering torque limiting processing unit 81, when the value of the steering torque T h is less than the second lower limit value T h_LL2Until it falls below, the output restricted steering torque T h_lim sets the value to "0". The steering torque limiting processing unit 81 sets the value of the restricted steering torque T h after the value of the steering torque T h_LL2 falls below the second lower limit value T h according to the value of the steering torque T h_lim . However, due to the influence of the first dead zone, the value of the restricted steering torque T h_lim does not follow the value of the original steering torque T h that changes in a sine wave shape. The value of the restricted steering torque T h_lim is smaller than the value of the original steering torque T h .

[0078] When the second limiting process is executed, the steering reaction force rapidly increases or decreases as the steering wheel 5 is steered. Therefore, as a feel through the steering wheel 5, a steering feel with a catching feeling can be given to the driver of the vehicle.

[0079] <The Third Limiting Process> As shown in FIG. 6, the third limiting process sets a second dead zone defined by a limit value T h for the absolute value of the steering torque T h_LV , and after the absolute value of the steering torque T h reaches a value within the second dead zone, the limit value T h_LV is gradually decreased to gradually increase the second dead zone, thereby limiting the absolute value of the steering torque T h to the limit value T h_LV . The limit value T h_LV is a value greater than "0" and is the boundary value of the second dead zone. That is, the second dead zone is the range of the absolute value of the steering torque T h_LV equal to or greater than the limit value T h . The limit value T h_LV is set to the same value as the absolute value of the steering torque T h when, for example, an end hit occurs. The limit value T h_LV is stored in the memory.

[0080] For example, when an end hit occurs and the state of the end hit continues, the absolute value of the steering torque Th changes as follows. That is, as the steering wheel 5 is steered, the absolute value of the steering torque T h gradually increases and eventually reaches a predetermined value (time T1). The predetermined value is equal to the limit value T h_LV . When the end hit continues, the absolute value of the steering torque T h is maintained at the predetermined value.

[0081] The steering torque limit processing unit 81 sets the absolute value of the steering torque T h to the absolute value of the limited steering torque T h_LV until the absolute value of the steering torque T h reaches the limit value T h_lim . After the absolute value of the steering torque T h reaches the limit value T h_LV , the dead zone range is gradually expanded. That is, as shown by the arrow AD in FIG. 6, the steering torque limit processing unit 81 gradually decreases the limit value T h_LV .

[0082] The steering torque limit processing unit 81 compares the absolute value of the steering torque T h with the limit value T h_LV . When the absolute value of the steering torque T h exceeds the limit value T h_LV , the absolute value of the steering torque T h is limited to the limit value T h_LV . After being limited to the limit value T h_LV , the absolute value of the steering torque T h becomes the absolute value of the limited steering torque T h_lim . Since the limit value T h_LV gradually decreases, the absolute value of the steering torque T h , and thus the absolute value of the limited steering torque T h_lim gradually decreases.

[0083] When the third limiting process is executed, the steering reaction force gradually increases as the steering wheel 5 is steered. Therefore, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feeling such that the steering wheel 5 is gradually pushed back, or a steering feeling with a sense of abutment.

[0084] <Configuration of Assist Torque Command Value Calculation Unit 82> Next, the configuration of the assist torque command value calculation unit 82 will be described in detail. As shown in FIG. 3, the assist torque command value calculation unit 82 includes a basic assist torque calculation unit 82A, a gain calculation unit 82B, and a multiplier 82C. The basic assist torque calculation unit 82A calculates a basic assist torque T11 based on the steering torque T h or the limited steering torque T h_lim and the vehicle speed V. The basic assist torque T11 is the basis for calculating the assist torque command value T1, and is a torque in the same direction as the steering direction of the steering wheel 5. The absolute value of the basic assist torque T11 becomes larger as the absolute value of the steering torque T h is larger and the vehicle speed V is slower. The gain calculation unit 82B calculates a gain G p according to the vehicle speed V. The gain calculation unit 82B calculates the gain G p using a first map M1 described later. The multiplier 82C multiplies the basic assist torque T11 by the gain G p to calculate the assist torque command value T1.

[0085] As shown in FIG. 7, the first map M1 is a two-dimensional map that defines the relationship between the vehicle speed V and the gain G p . The first map M1 has a first characteristic indicated by a first characteristic line L1 and a second characteristic indicated by a second characteristic line L2. The first characteristic is a characteristic used when the current limiting process by the current limiting processing unit 66 is not executed. The second characteristic is a characteristic used when the current limiting process by the current limiting processing unit 66 is executed.

[0086] In the first characteristic, as the vehicle speed V increases, the gain G p value linearly and gradually increases. Also in the second characteristic, similar to the first characteristic, as the vehicle speed V increases, the gain G p value linearly and gradually increases. However, the value of the gain G p for the vehicle speed V in the second characteristic is larger than the value of the gain G p for the vehicle speed V in the first characteristic. Also, the slope which is the rate of change of the gain G p for the vehicle speed V in the second characteristic is slightly larger than the slope which is the rate of change of the gain G p for the vehicle speed V in the first characteristic.

[0087] Note that the second characteristic indicated by the second characteristic line L2 is appropriately set according to product specifications and the like. The second characteristic may be set, for example, as follows. That is, the value of the gain G p for the vehicle speed V in the second characteristic is smaller than the value of the gain G p for the vehicle speed V in the first characteristic. Also, the slope which is the rate of change of the gain G p for the vehicle speed V in the second characteristic is slightly smaller than the slope which is the rate of change of the gain G p for the vehicle speed V in the first characteristic.

[0088] The gain calculation unit 82B switches the characteristic of the first map M1 between the first characteristic and the second characteristic based on the second command S2 generated by the command generation unit 85. <Configuration of Axial Force Torque Calculation Unit 83> Next, the configuration of the axial force torque calculation unit 83 will be described in detail.

[0089] As shown in FIG. 3, the axial force torque calculation unit 83 includes an axial force calculation unit 83A, a compensated axial force calculation unit 83B, an adder 83C, and a converter 83D. The axial force calculation unit 83A calculates the angular axial force. The angular axial force is, for example, an ideal axial force corresponding to the target pinion angle θ p * The axial force calculation unit 83A is based on the target pinion angle θ p *Based on this, the angular axial force is calculated. The absolute value of the angular axial force may increase as the absolute value of the target pinion angle θ p * increases and as the vehicle speed V decreases. The absolute value of the angular axial force increases linearly with the increase in the absolute value of the target pinion angle θ p * . The angular axial force has the same sign as the target pinion angle θ p * . The angular axial force is an axial force that does not reflect the road surface condition or the force acting on the steering shaft 22 via the steered wheel 6. Note that the axial force calculation unit 83A may take in the pinion angle θ p * instead of the target pinion angle θ p or the steering angle θ s .

[0090] The axial force calculation unit 83A calculates the current axial force. The current axial force is an axial force corresponding to the value of the current I b of the steering motor 31. The axial force calculation unit 83A calculates the current axial force based on the value of the current I b of the steering motor 31. The value of the current I b of the steering motor 31 changes according to the disturbance caused by the road surface condition such as the road surface friction resistance acting on the steered wheel 6, corresponding to the difference between the target pinion angle θ p * and the actual pinion angle θ p . That is, the value of the current I b of the steering motor 31 reflects the actual road surface condition acting on the steered wheel 6. Therefore, it is possible to calculate the axial force reflecting the influence of the road surface condition based on the value of the current I b of the steering motor 31. The axial force calculation unit 83A calculates the current axial force by multiplying the value of the current I b of the steering motor 31 by a gain that is a coefficient corresponding to the vehicle speed V, for example.

[0091] The axial force calculation unit 83A calculates the combined axial force T12. The combined axial force T12 is an axial force obtained by mixing the angular axial force and the current axial force at a predetermined ratio. The axial force calculation unit 83A individually sets the distribution ratios for the angular axial force and the current axial force according to various state variables reflecting vehicle behavior, road surface conditions, or steering conditions. The axial force calculation unit 83A calculates the combined axial force T12 by adding the values obtained by multiplying the angular axial force and the current axial force by the individually set distribution ratios, respectively.

[0092] However, based on the third command S3 generated by the command generation unit 85, the axial force calculation unit 83A switches the axial force used for calculating the axial force torque T2 from the combined axial force T12 to the angular axial force. For example, the axial force calculation unit 83A sets the distribution ratio of the current axial force to "0%" and the distribution ratio of the angular axial force to "100%". Thereby, only the angular axial force is used for calculating the axial force torque T2.

[0093] The compensation axial force calculation unit 83B calculates the deviation compensation axial force T13. The deviation compensation axial force T13 is an axial force corresponding to the value of the difference between the steering angle θ s of the steering wheel 5 and the steering angle θ w of the steered wheel 6. The compensation axial force calculation unit 83B calculates the steering angle θ p of the steered wheel 6 based on the pinion angle θ w calculated by the pinion angle calculation unit 61, and multiplies the calculated steering angle θ w by the reciprocal of the steering ratio to convert the steering angle θ w of the steered wheel 6 to the steering angle θ s of the steering wheel 5. The compensation axial force calculation unit 83B calculates the angle deviation Δθ s which is the difference between the converted steering angle θ s and the steering angle θ s calculated by the steering angle calculation unit 51, and calculates the deviation compensation axial force T13 according to the calculated angle deviation Δθ s . The compensation axial force calculation unit 83B calculates the deviation compensation axial force T13 using, for example, the second map M2 described later.

[0094] The adder 83C takes in the combined axial force T12 calculated by the axial force calculation unit 83A and the deviation compensation axial force T13 calculated by the compensation axial force calculation unit 83B. The adder 83C calculates the final axial force T14 by adding the combined axial force T12 and the deviation compensation axial force T13. The final axial force T14 is the final axial force used for the calculation of the axial force torque T2.

[0095] The converter 83D takes in the final axial force T14 calculated by the adder 83C. The converter 83D calculates the axial force torque T2 by converting the final axial force T14 into the torque with respect to the steering shaft 11.

[0096] As shown in FIG. 8, the second map M2 is a two-dimensional map defining the relationship between the angular deviation Δθ s and the deviation compensation axial force T13. The second map M2 has a third characteristic indicated by the third characteristic line L3 and a fourth characteristic indicated by the fourth characteristic line L4. The third characteristic is the characteristic used when the current limiting process by the current limiting processing unit 66 is not executed. The fourth characteristic is the characteristic used when the current limiting process by the current limiting processing unit 66 is executed.

[0097] In the third characteristic, until the value of the angular deviation Δθ s reaches the angular deviation threshold value Δθ s_th , the value of the deviation compensation axial force T13 is maintained at "0". That is, a dead zone is set for the angular deviation Δθ s . The dead zone is the range of the value of the angular deviation Δθ s_th that is "0" or more and less than or equal to the angular deviation threshold value Δθ s . After the value of the angular deviation Δθ s reaches the angular deviation threshold value Δθ s_th , as the value of the angular deviation Δθ s increases, the value of the deviation compensation axial force T13 gradually increases. However, as the value of the angular deviation Δθ s increases, the slope, which is the rate of change of the value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s , gradually becomes larger.

[0098] In the fourth characteristic, the value of the deviation compensation axial force T13 gradually increases as the value of the angular deviation Δθ s increases starting from "0". That is, there is no dead zone set for the angular deviation Δθ s in the fourth characteristic. The slope, which is the rate of change of the value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s , gradually becomes larger as the value of the angular deviation Δθ s increases. The value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s in the fourth characteristic is larger than the value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s in the third characteristic.

[0099] Based on the fourth command S4 generated by the command generation unit 85, the compensation axial force calculation unit 83B switches the characteristics of the second map M2 between the third characteristic and the fourth characteristic. <Operation of the present embodiment> Next, the operation of the present embodiment will be described.

[0100] <F lim =0> When the value of the current limit flag F lim is "0", that is, when the current of the steering motor 31 is not limited, the command generation unit 85 generates the following first to fourth commands S1 to S4.

[0101] · The first command S1 is a command instructing the steering torque limit processing unit 81 not to execute the steering torque limit processing. · The second command S2 is a command instructing the gain calculation unit 82B to use the first characteristic of the first map M1 shown in FIG. 7.

[0102] · The third command S3 is a command instructing the axial force calculation unit 83A to use the mixed axial force T12, which is a mixture of the current axial force and the angular axial force, for the calculation of the axial force torque T2. · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the third characteristic of the second map M2 shown in FIG. 8.

[0103] The steering torque limit processing unit 81 does not execute the steering torque limit processing. That is, the steering torque T detected through the torque sensor 42 h is directly used for the control of the reaction force motor 12. The gain calculation unit 82B calculates the gain G p based on the first characteristic of the first map M1. The axial force calculation unit 83A generates a mixed axial force T12 that mixes the current axial force and the mixed axial force. The compensation axial force calculation unit 83B calculates a deviation compensation axial force T13 based on the third characteristic of the second map M2. Thereby, normal reaction force control is performed when the current of the steering motor 31 is not limited.

[0104] <F lim =1> When the value of the current limit flag F lim is "1", that is, when the first event B1 in which the temperature of the steering motor 31 rises excessively occurs, the command generation unit 85 generates the following first to fourth commands S1 to S4.

[0105] · The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the first limit processing shown in FIG. 4. · The second command S2 is a command instructing the gain calculation unit 82B to use the second characteristic of the first map M1.

[0106] · The third command S3 is a command instructing the axial force calculation unit 83A to use only the angular axial force. · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the fourth characteristic of the second map M2 shown in FIG. 8.

[0107] The steering torque limit processing unit 81 executes the first limit processing. Through the execution of the first limit processing, the value of the steering torque T h is limited. When the first limit processing is executed, when the steering wheel 5 is steered beyond the small steering angle region, the steering reaction force is the steering torque T hIt becomes larger than the original steering reaction force according to the situation. Therefore, as a feel through the steering wheel 5, for example, when the steering device 2 is an electric power steering device, a steering feel similar to that when no assist force is applied to the steering wheel 5 can be given to the driver of the vehicle. The driver of the vehicle can recognize that the first event B1 has occurred by feeling the steering reaction force through the steering wheel 5 as a feel.

[0108] The axial force torque calculation unit 83 calculates the axial force torque T2 using the angular axial force calculated by the axial force calculation unit 83A and the deviation compensation axial force T13 calculated by the compensation axial force calculation unit 83B. Due to the occurrence of the first event B1, the current I b supplied to the steering motor 31 is restricted, so it is difficult to use the mixed axial force T12 in which the current axial force and the angular axial force are mixed. Therefore, the axial force used for calculating the axial force torque T2 is switched from the mixed axial force T12 to only the angular axial force. Thereby, a more appropriate steering reaction force is applied to the steering wheel 5.

[0109] The compensation axial force calculation unit 83B calculates the deviation compensation axial force T13 based on the fourth characteristic of the second map M2. The value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s is larger than the value of the deviation compensation axial force T13 with respect to the angular deviation Δθ s of the third characteristic. When the value of the deviation compensation axial force T13 increases, the value of the axial force torque T2 also increases. Therefore, the decrease in the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5 can be reflected in the steering reaction force. The decrease in the steering followability is caused by the restriction of the current I b of the steering motor 31.

[0110] The gain calculation unit 82B calculates the gain G p based on the second characteristic of the first map M1. The gain G calculated based on the second characteristic of the first map M1 pUsing this, the assist torque command value T1 is calculated. As a result, fluctuations in the steering reaction force due to the axial force difference that occurs before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force are suppressed. The reason is as follows.

[0111] The value of the angular axial force immediately after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force may vary with respect to the value of the combined axial force T12 immediately before the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force. For this reason, the value of the axial force torque T2 varies, and the reaction force torque command value T * , and thus the steering reaction force also varies.

[0112] Therefore, when the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force, the gain calculation unit 82B calculates the gain G p based on the second characteristic of the first map M1. The second characteristic is set from the viewpoint of adapting the assist torque command value T1 to a normal state where the output of the steering motor 31 is not restricted. That is, the second characteristic is set from the viewpoint of suppressing fluctuations in the steering reaction force due to the axial force difference that occurs before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force.

[0113] For this reason, by using the gain G p of the second characteristic for calculating the assist torque command value T1, the assist torque command value T1 conforms to a normal state where the output of the steering motor 31 is not restricted. Therefore, fluctuations in the steering reaction force due to the axial force difference that occurs before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force are suppressed. That is, a more appropriate steering reaction force is applied to the steering wheel 5. Before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force is also before and after the current limit processing unit 66 starts executing the current limit processing.

[0114] Note that switching the characteristics of the first map M1 from the first characteristic to the second characteristic is to adjust the value of the gain G so that the assist torque command value T1 conforms to the normal state where the output of the steering motor 31 is not restricted. Also, switching the characteristics of the first map M1 from the first characteristic to the second characteristic and calculating the assist torque command value T1 using the gain G p of the second characteristic to be switched is to adjust the assist torque command value T1 so that it conforms to the normal state where the output of the steering motor 31 is not restricted. p When the value of the current limit flag F lim = 2, that is, when the second event B2 in which the voltage V input to the steering control device 1B decreases occurs, the command generation unit 85 generates the following first to fourth commands S1 to S4. p · The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the second limit processing shown in FIG. 5.

[0115] <F lim =2> Current limit flag F lim · The second command S2 is a command instructing the gain calculation unit 82B to use the second characteristic of the first map M1. b · The third command S3 is a command instructing the axial force calculation unit 83A to use only the angular axial force.

[0116] · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the fourth characteristic of the second map M2 shown in FIG. 8. · The second command S2 is a command instructing the gain calculation unit 82B to use the second characteristic of the first map M1.

[0117] · The third command S3 is a command instructing the axial force calculation unit 83A to use only the angular axial force. · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the fourth characteristic of the second map M2 shown in FIG. 8.

[0118] The steering torque limit processing unit 81 executes the second limit processing. Through the execution of the second limit processing, the steering torque T hThe value of is restricted. When the second limiting process is executed, the steering reaction force rapidly increases or decreases as the steering wheel 5 is steered. Therefore, as a feel transmitted through the steering wheel 5, a steering feel with a catching sensation can be given to the driver of the vehicle. The driver of the vehicle can recognize that the second event B2 has occurred by feeling the steering reaction force transmitted through the steering wheel 5 as a feel.

[0119] Due to the occurrence of the second event B2, the current I supplied to the steering motor 31 b is restricted, making it difficult to use the combined axial force T12 in which the current axial force and the angular axial force are mixed. Therefore, the axial force calculation unit 83A switches the axial force used for calculating the axial force torque T2 from the combined axial force T12 to only the angular axial force, as in the case where the value of the current limit flag F lim is "1". Thereby, a more appropriate steering reaction force is applied to the steering wheel 5.

[0120] Due to the current I of the steering motor 31 b being restricted, the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5 deteriorates. Therefore, the compensation axial force calculation unit 83B calculates the deviation compensation axial force T13 based on the fourth characteristic of the second map M2, as in the case where the value of the current limit flag F lim is "1". Thereby, the deterioration of the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5 can be reflected in the steering reaction force.

[0121] The gain calculation unit 82B calculates the gain G lim based on the second characteristic of the first map M1, as in the case where the value of the current limit flag F p is "1". The assist torque command value T1 is calculated using the gain G p calculated based on the second characteristic of the first map M1. Thereby, fluctuations in the steering reaction force due to the axial force difference that occurs before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force are suppressed.

[0122] <F lim = 3> Current limit flag F lim When the value of is "3", that is, when the third event B3 in which a high load is continuously applied to the steering motor 31 occurs, the command generation unit 85 generates the following first to fourth commands S1 to S4.

[0123] · The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the third limit processing shown in FIG. 6. · The second command S2 is a command instructing the gain calculation unit 82B to use the second characteristic of the first map M1.

[0124] · The third command S3 is a command instructing the axial force calculation unit 83A to use only the angular axial force. · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the fourth characteristic of the second map M2 shown in FIG. 8.

[0125] The steering torque limit processing unit 81 executes the third limit processing. When the third limit processing is executed, the steering reaction force gradually increases as the steering wheel 5 is steered. Therefore, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feel such that the steering wheel 5 is gradually pushed back, or a steering feel with a sense of abutment. The driver of the vehicle can recognize the occurrence of the third event B3 by feeling the steering reaction force through the steering wheel 5 as a feel.

[0126] Due to the occurrence of the third event B3, the current I supplied to the steering motor 31 b is limited, so it is difficult to use the mixed axial force T12 in which the current axial force and the angular axial force are mixed. Therefore, the axial force calculation unit 83A switches the axial force used for calculating the axial force torque T2 from the mixed axial force T12 to only the angular axial force as in the case where the value of the current limit flag F lim is "1". Thereby, a more appropriate steering reaction force is applied to the steering wheel 5.

[0127] The current I of the steering motor 31 b Due to the limitation of the current I, the steering followability of the steering wheel 6 with respect to the steering of the steering wheel 5 deteriorates. Therefore, the compensation axial force calculation unit 83B calculates the deviation compensation axial force T13 based on the fourth characteristic of the second map M2 in the same manner as when the value of the current limit flag F lim is "1". Thereby, the decrease in the steering followability of the steering wheel 6 with respect to the steering of the steering wheel 5 can be reflected in the steering reaction force.

[0128] The gain calculation unit 82B calculates the gain G lim based on the second characteristic of the first map M1 in the same manner as when the value of the current limit flag F p is "1". The assist torque command value T1 is calculated using the gain G p calculated based on the second characteristic of the first map M1. Thereby, the fluctuation of the steering reaction force due to the axial force difference generated before and after the axial force used for the calculation of the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force is suppressed.

[0129] <F lim =4> When the value of the current limit flag F lim is "4", that is, when the fourth event B4 in which power supply to either one of the two winding groups becomes difficult occurs, the command generation unit 85 generates the first to fourth commands S1 to S4 similar to the case when the value of the current limit flag F lim is "1".

[0130] · The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the first limit processing shown in FIG. 4. · The second command S2 is a command instructing the gain calculation unit 82B to use the second characteristic of the first map M1.

[0131] · The third command S3 is a command instructing the axial force calculation unit 83A to use only the angular axial force. · The fourth command S4 is a command instructing the compensation axial force calculation unit 83B to use the fourth characteristic of the second map M2 shown in FIG. 8.

[0132] The steering torque limit processing unit 81 executes the first limit processing. Through the execution of the first limit processing, the value of the steering torque T h is limited. When the first limit processing is executed, when the steering wheel 5 is steered beyond the small steering angle region, the steering reaction force becomes larger than the original steering reaction force corresponding to the steering torque T h . Therefore, as a feel transmitted through the steering wheel 5, for example, when the steering device 2 is an electric power steering device, a steering feel similar to when no assist force is applied to the steering wheel 5 can be given to the driver of the vehicle. The driver of the vehicle can recognize that the fourth event B4 has occurred by feeling the steering reaction force transmitted through the steering wheel 5 as a feel.

[0133] Due to the occurrence of the fourth event B4, the current I b supplied to the steering motor 31 is limited, so it is difficult to use the combined axial force T12 in which the current axial force and the angular axial force are mixed. Therefore, the axial force calculation unit 83A switches the axial force used for calculating the axial force torque T2 from the combined axial force T12 to only the angular axial force as in the case where the value of the current limit flag F lim is "1". Thereby, a more appropriate steering reaction force is applied to the steering wheel 5.

[0134] Due to the limitation of the current I b of the steering motor 31, the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5 decreases. Therefore, the compensation axial force calculation unit 83B calculates the deviation compensation axial force T13 based on the fourth characteristic of the second map M2 as in the case where the value of the current limit flag F lim is "1". Thereby, it is possible to reflect the decrease in the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5 in the steering reaction force.

[0135] The gain calculation unit 82B is configured such that the current limit flag Flim Similar to the case where the value of lim is "1", the gain G is calculated based on the second characteristic of the first map M1. p The gain G calculated based on the second characteristic of the first map M1 p is used to calculate the assist torque command value T1. This suppresses fluctuations in the steering reaction force due to the axial force difference that occurs before and after the axial force used for calculating the axial force torque T2 is switched from the combined axial force T12 to only the angular axial force.

[0136] <Effects of the present embodiment> The present embodiment has the following effects. (1) The steering control device 1 includes a reaction force control device 1A that controls a reaction force motor 12 that generates a steering reaction force applied to the steering wheel 5, and a steering control device 1B that controls a steering motor 31 that generates a steering force for steering the steered wheels 6. When an event occurs in which the output of the steering motor 31 is restricted, the reaction force control device 1A executes a reaction force change process for changing the steering reaction force according to the content of the event.

[0137] Note that the reaction force change process includes first to third restriction processes and a process of switching the characteristic of the first map M1 from the first characteristic to the second characteristic. The reaction force change process also includes a process of switching the axial force used for calculating the axial force torque T2 from the combined axial force to the angular axial force and a process of switching the characteristic of the second map M2 from the third characteristic to the fourth characteristic.

[0138] According to this configuration, when an event occurs in which the output of the steering motor 31 is restricted, the steering reaction force is changed according to the content of the event. Therefore, as a feel transmitted through the steering wheel 5, different steering sensations corresponding to the content of the event in which the output of the steering motor 31 is restricted can be given to the driver of the vehicle. Accordingly, the driver of the vehicle can recognize that the output of the steering motor 31 is restricted, and thus the content of the event in which the output of the steering motor 31 is restricted, by feeling the steering reaction force transmitted through the steering wheel 5 as a feel. Therefore, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor 31 is restricted. The driver of the vehicle can continue to steer the steering wheel 5 in consideration of the content of the event in which the output of the steering motor 31 is restricted.

[0139] (2) The reaction force control device 1A executes a process of calculating the assist torque command value T1, a process of calculating the axial force torque T2, and a process of calculating the reaction force torque command value T by subtracting the axial force torque T2 from the assist torque command value T1. * In this case, the reaction force change process may include a process of changing the assist torque command value T1 and a process of changing the axial force torque T2.

[0140] Note that the process of changing the assist torque command value T1 includes the first to third restriction processes and a process of switching the characteristics of the first map M1 from the first characteristics to the second characteristics. The process of changing the axial force torque T2 includes a process of switching the axial force used for the calculation of the axial force torque T2 from the combined axial force to the angular axial force and a process of switching the characteristics of the second map M2 from the third characteristics to the fourth characteristics.

[0141] According to this configuration, when an event occurs in which the output of the steering motor 31 is restricted, the reaction force control device 1A can change the steering reaction force according to the content of the event by changing the assist torque command value T1 and the axial force torque T2.

[0142] (3) When an event occurs in which the output of the steering motor 31 is restricted, for example, the steering torque T detected by the torque sensor 42 h is restricted according to the content of the event, thereby changing the assist torque command value T1. According to this configuration, when an event occurs in which the output of the steering motor 31 is restricted, the steering torque T detected by the torque sensor 42 h is restricted according to the content of the event, so that the assist torque command value T1 can be changed according to the content of the event.

[0143] (4) The axial force used for calculating the axial force torque T2 is the current axial force corresponding to the value of the current I of the steering motor 31 b and the angular axial force corresponding to the target pinion angle θ which is the target rotation angle of the pinion shaft 21 p * and includes a mixed axial force T12 obtained by mixing them. When an event occurs in which the output of the steering motor 31 is restricted, the reaction force control device 1A switches the axial force used for calculating the axial force torque T2 from the mixed axial force T12 to the angular axial force.

[0144] According to this configuration, when an event occurs in which the output of the steering motor 31 is restricted, the axial force used for calculating the axial force torque T2 is switched from the mixed axial force T12 to the angular axial force. Since the angular axial force is not affected by the current of the steering motor 31, it is possible to apply a more appropriate steering reaction force to the steering wheel 5.

[0145] (5) When an event occurs in which the output of the steering motor 31 is restricted, the reaction force control device 1A adjusts the assist torque command value T1 so as to conform to the normal state in which the output of the steering motor 31 is not restricted when switching the axial force used for calculating the axial force torque T2 from the mixed axial force T12 to the angular axial force.

[0146] The value of the angular axial force immediately after switching from the mixed axial force T12 to the angular axial force may vary from the value of the mixed axial force T12 immediately before switching from the mixed axial force T12 to the angular axial force. In this regard, according to the present embodiment, when an event occurs in which the output of the steering motor 31 is limited, the assist torque command value T1 is adjusted so as to conform to a normal state in which the output of the steering motor 31 is not limited. The steering reaction force is also adjusted in accordance with the adjustment of the assist torque command value T1. Therefore, it is possible to suppress the fluctuation of the steering reaction force due to the axial force difference that occurs before and after the axial force used in the calculation of the axial torque T2 is switched from the mixed axial force T12 to the angular axial force.

[0147] (6) The reaction force control device 1A calculates the basic assist torque T11 and applies a gain G according to the vehicle speed V to the calculated basic assist torque T11. p When an event occurs in which the output of the steering motor 31 is limited, the reaction force control device 1A calculates the assist torque command value T1 by multiplying the gain G p According to this configuration, when an event occurs in which the output of steering motor 31 is limited, assist torque command value T1 is adjusted so as to conform to a normal state in which the output of steering motor 31 is not limited. This makes it possible to suppress fluctuations in steering reaction force due to an axial force difference occurring before and after the axial force used in the calculation of axial force torque T2 is switched from mixed axial force T12 to the angle axial force.

[0148] (7) The axial force used to calculate the axial torque T2 is the angle deviation Δθ sIt is the axial force obtained by adding the deviation compensation axial force T13 calculated based on to the combined axial force T12. When an event occurs where the output of the steering motor 31 is restricted, the reaction force control device 1A increases the value of the deviation compensation axial force T13 compared to the normal state where the output of the steering motor 31 is not restricted. According to this configuration, when an event occurs where the output of the steering motor 31 is restricted, the value of the deviation compensation axial force T13 increases compared to the normal state where the output of the steering motor 31 is not restricted. Therefore, it is possible to reflect in the steering reaction force the decrease in the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5. The angle deviation Δθ s is a state variable that reflects the steering followability of the steered wheels 6 with respect to the steering of the steering wheel 5.

[0149] (8) When the first event B1 or the fourth event B4 occurs, the reaction force control device 1A executes the first restriction process. By executing the first restriction process, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feel as if the steering wheel 5 has become heavy. The driver of the vehicle can recognize that the first event B1 or the fourth event B4 has occurred by feeling the steering reaction force through the steering wheel 5. The driver of the vehicle can appropriately respond to the occurrence of the first event B1 or the fourth event B4. The response is to continue steering the steering wheel 5 in consideration of the occurrence of the first event B1 or the fourth event B4. For example, the driver of the vehicle can reduce the burden on the steering motor 31 by reducing the steering of the steering wheel 5.

[0150] (9) When the second event occurs, the steering torque limit processing unit 81 executes the second limit processing. By executing the second limit processing, it is possible to give the driver of the vehicle a steering feeling with a catching sensation as a reaction through the steering wheel 5. The driver of the vehicle can recognize that the second event B2 has occurred by feeling the steering reaction force through the steering wheel 5. The driver of the vehicle can appropriately respond to the occurrence of the second event B2. The response is, for example, battery replacement or maintenance.

[0151] (10) When the third event occurs, the steering torque limit processing unit 81 executes the third limit processing. By executing the third limit processing, it is possible to give the driver of the vehicle a steering feeling such that the steering wheel 5 is gradually pushed back, or a steering feeling with a hitting sensation, as a reaction through the steering wheel 5. The driver of the vehicle can recognize that the third event B3 has occurred by feeling the steering reaction force through the steering wheel 5. The driver of the vehicle can appropriately respond to the occurrence of the second event B2. The response is to continue steering the steering wheel 5 in consideration of the occurrence of the second event B2. For example, the driver of the vehicle can reduce the load on the steering motor 31 by steering the steering wheel 5 so as to eliminate the contact between the steered wheels 6 and the obstacle.

[0152] <Other Embodiments> Note that this embodiment may be implemented with the following modifications. · The events in which the output of the steering motor 31 is restricted are not limited to the first to fourth events B1 to B4. The events in which the output of the steering motor 31 is restricted may further include the following fifth to seventh events B5 to B7.

[0153] B5. The backup power supply is activated. B6. The vehicle speed V detected through the vehicle speed sensor 41 is abnormal. The drive mode of the steering motor 31 is the independent drive mode.

[0154] The backup power supply is a power supply device that backs up power supply to each part of the vehicle when the battery, which is the main power supply, fails. When the vehicle power is switched from the main power supply to the backup power supply, the current limit processing unit 66 determines that the fifth event B5 has occurred. When the fifth event B5 occurs, the command generation unit 85 generates the first to fourth commands S1 to S4 similar to the case when the first event B1 occurs.

[0155] For example, when the vehicle speed V suddenly changes, or when the vehicle speed V is not detected even though the vehicle is running, the current limit processing unit 66 determines that the sixth event B6 in which the vehicle speed V is abnormal has occurred. When the sixth event B6 occurs, the command generation unit 85 generates the first to fourth commands S1 to S4 similar to the case when the first event B1 occurs.

[0156] The independent drive mode is a drive mode in a case where an abnormality in either one of the two systems is detected, but the abnormality has not been confirmed and there is a possibility of normal recovery. In the independent drive mode, torque is generated by the winding group of the system in which no abnormality is detected. For example, when the abnormality determination signal S d generated by the abnormality determination unit of the steering control device 1B indicates that an abnormality in either one of the two systems has been confirmed, the current limit processing unit 66 determines that the seventh event B7 has occurred. When the seventh event B7 occurs, the command generation unit 85 generates the first to fourth commands S1 to S4 similar to the case when the second event B2 occurs.

[0157] · When the current limit processing unit 66 determines that the first event B1 in which the temperature T of the steering motor 31 rises excessively has occurred, the current limit processing unit 66 may set the value of the current limit flag F m according to the temperature T of the steering motor 31. When the temperature T of the steering motor 31 exceeds the first temperature threshold, the current limit flag F m lim m lim ​​​Set the value of m to "1A". When the temperature T of the steering motor 31 lim exceeds the second temperature threshold value, the current limit flag F m is set to "1B". The second temperature threshold value is larger than the first temperature threshold value. When the temperature T of the steering motor 31 lim exceeds the third temperature threshold value, the current limit flag F lim is set to "1C". The third temperature threshold value is larger than the second temperature threshold value. When the value of the current limit flag F

[0158] is "1A", "1B" or "1C", the command generation unit 85 generates the following first to fourth commands S1 to S4. h_UL1 The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the first limit processing shown in FIG. 4, and is a command specifying the first upper limit value T h_LL1 and the first lower limit value T h_UL1 . However, the absolute value of the first upper limit value T h_LL1 and the absolute value of the first lower limit value T lim become smaller in the order of the value of the current limit flag F h_UL1 being "1A", "1B", "1C". That is, the absolute value of the first upper limit value T h_LL1 and the absolute value of the first lower limit value T m decrease stepwise as the temperature T of the steering motor 31 m rises. The driver of the vehicle can recognize that the first event B1 in which the temperature T of the steering motor 31 rises excessively, and thus the degree of increase in the temperature of the steering motor 31, by feeling the steering reaction force via the steering wheel 5. The second to fourth commands S2 to S4 are the same as in the previous embodiment when the value of the current limit flag F lim is "1". The first event B1 is an example of an abnormality of the steering motor 31.

[0159] · When it is determined that the second event B2 in which the voltage V input to the steering control device 1B b decreases has occurred, the voltage Vb Set the value of the current limit flag F according to the value of lim . The current limit processing unit 66 may be configured to set the value of the current limit flag F when the value of the voltage V b is less than the first voltage threshold. When the value of the voltage V lim is less than the first voltage threshold, the current limit processing unit 66 sets the value of the current limit flag F to "2A". When the value of the voltage V b is less than the second voltage threshold, the current limit processing unit 66 sets the value of the current limit flag F to "2B". The second voltage threshold is smaller than the first voltage threshold. When the value of the voltage V lim is less than the third voltage threshold, the current limit processing unit 66 sets the value of the current limit flag F to "2C". The third voltage threshold is smaller than the second voltage threshold. When the value of the current limit flag F b is "2A", "2B" or "2C", the command generation unit 85 generates the following first to fourth commands S1 to S4. lim The first command S1 is a command instructing the steering torque limit processing unit 81 to execute the second limit processing shown in FIG. 4, and specifies the second upper limit value T lim and the second lower limit value T

[0160] of the first dead zone. However, the absolute value of the second upper limit value T h_UL2 and the absolute value of the second lower limit value T h_LL2 are greater in the order of the value of the current limit flag F being "2C", "2B", "1A". That is, the absolute value of the second upper limit value T h_UL2 and the absolute value of the second lower limit value T h_LL2 increase step by step as the voltage V lim input to the steering control device 1B decreases. In other words, the width of the first dead zone expands step by step as the voltage V h_UL2 input to the steering control device 1B decreases. The driver of the vehicle can feel, through the steering reaction force via the steering wheel 5, that the second event B2 in which the voltage V h_LL2 input to the steering control device 1B decreases has occurred, and thus the voltage V b input to the steering control device 1B b decreases. In other words, the width of the first dead zone expands step by step as the voltage V b input to the steering control device 1B decreases. The driver of the vehicle can feel, through the steering reaction force via the steering wheel 5, that the second event B2 in which the voltage V bThe degree of decrease can be recognized. The second to fourth commands S2 to S4 are the same as when the value of the current limit flag F lim is "1". The second event B2 is an example of a vehicle abnormality.

[0161] Note that the current limit processing unit 66 may set the value of the current limit flag F lim according to the voltage of the battery detected through the voltage sensor. · When the first to seventh events B1 to B7 occur simultaneously, the event with the higher priority may be prioritized. For example, the fifth event B5, the fourth event B4, the sixth event B6, the second event B2, the third event B3, the first event B1, and the seventh event B7 have higher priorities in this order. The priority is set based on, for example, the warning level of the event.

[0162] · When an event occurs in which the output of the steering motor 31 is restricted, the reaction torque command value calculation unit 52 may limit the basic assist torque T h instead of the steering torque T. The assist torque command value T1 decreases by the amount by which the basic assist torque T11 is restricted. The reaction torque command value T * increases by the amount by which the assist torque command value T1 decreases, so the steering reaction force applied to the steering wheel 5 increases. Therefore, the driver of the vehicle can recognize that the output of the steering motor 31 is restricted by feeling the steering reaction force via the steering wheel 5 as a tactile sensation. The reaction torque command value calculation unit 52 may vary the restriction mode of the basic assist torque T11 depending on the content of the event in which the output of the steering motor 31 is restricted, in the same manner as when restricting the steering torque T h .

[0163] · When an event occurs in which the output of the steering motor 31 is restricted, the reaction torque command value calculation unit 52 may limit the assist torque command value T1 h instead of the steering torque T. The reaction torque command value T *Since it increases, the steering reaction force applied to the steering wheel 5 also increases. Therefore, the driver of the vehicle can recognize that the output of the steering motor 31 is restricted by feeling the steering reaction force transmitted through the steering wheel 5 as a tactile sensation. The reaction torque command value calculation unit 52 h may vary the restriction mode of the assist torque command value T1 according to the content of the event in which the output of the steering motor 31 is restricted in the same manner as when restricting the steering torque T

Explanation of Signs

[0164] 1... Steering control device 1A... Reaction force control device (reaction force control unit) 1B... Steering control device (steering control unit) 5... Steering wheel 6... Steering wheel 12... Reaction force motor 21... Pinion shaft 31... Steering motor

Claims

1. A reaction force control unit configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel with power transmission to a steered wheel of a vehicle separated; A steering control unit configured to control a steering motor that generates a steering force for steering the steered wheel, and having: The reaction force control unit is a steering control device configured to execute a reaction force change process of changing the steering reaction force according to the content of the event when an event in which the output of the steering motor is restricted occurs.

2. The reaction force control unit performs a process of calculating an assist torque command value that is a torque in the same direction as the steering direction of the steering wheel based on a first state variable that reflects the steering state of the steering wheel; Based on a second state variable that reflects the steering state of the steered wheel, calculates an axial force acting on a steering shaft that steers the steered wheel, and converts the calculated axial force into a torque on the steering wheel to calculate an axial force torque Process; The reaction force control unit is configured to execute a process of calculating a reaction force torque command value that is a target value of the steering reaction force by subtracting the axial force torque from the assist torque command value, The reaction force change process includes a process of changing the assist torque command value and a process of changing the axial force torque. The steering control device according to claim 1.

3. The first state variable is a steering torque applied to the steering wheel, The process of changing the assist torque command value is a process of restricting the steering torque detected by a torque sensor according to the content of the event. The steering control device according to claim 2.

4. The second state variable includes the current of the steering motor and the target rotation angle of a pinion shaft that rotates in conjunction with the steering shaft, The axial force includes a mixed axial force obtained by mixing a current axial force corresponding to the value of the current of the steering motor and an angular axial force corresponding to the target rotation angle of the pinion shaft, When the event occurs, the reaction force control unit is configured to execute a process of switching the axial force from the mixed axial force to the angular axial force. The steering control device according to claim 2 or claim 3.

5. The reaction force control unit is configured to execute a process of adjusting the assist torque command value so as to conform to a normal state in which the output of the steering motor is not restricted when switching the axial force from the combined axial force to the angular axial force when the event occurs. The steering control device according to claim 4.

6. The reaction force control unit calculates a basic assist torque that is the basis for calculating the assist torque command value based on the first state variable, and multiplies the calculated basic assist torque by a gain corresponding to the vehicle speed to calculate the assist torque command value. The process of adjusting the assist torque command value is a process of adjusting the value of the gain so that the assist torque command value conforms to a normal state in which the output of the steering motor is not restricted. The steering control device according to claim 5.

7. The axial force is an axial force obtained by adding a deviation compensation axial force corresponding to an angle deviation, which is a difference between the combined axial force and the steering angle of the steering wheel converted from the rotation angle of the pinion shaft, to the combined axial force. The reaction force control unit is configured to execute a process of increasing the value of the deviation compensation axial force when the event occurs as compared with a normal state in which the output of the steering motor is not restricted. The steering control device according to claim 4.

8. The event includes an abnormality of the vehicle or the steering motor. The reaction force control unit is configured to increase the steering reaction force as the degree of the abnormality increases. The steering control device according to any one of claims 1 to 3.

Images