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 an assist torque command value calculation unit 82, an axial-force torque calculation unit 83, a calculator 84, and a steering torque limit processing unit 81. An assist torque command value calculation unit 82 calculates an assist torque command value T1 based on a steering torque Th. The axial-force torque calculation unit 83 calculates an axial force of a turning shaft based on a target pinion angle θp*, a value of a current Ib of a turning motor, and a vehicle speed V, and calculates an axial-force torque T2 by converting the calculated axial force into a torque with respect to a steering wheel. The calculator 84 subtracts the axial-force torque T2 from an assist torque command value T1 to calculate a reaction-force torque command value T*. The steering torque limit processing unit 81 limits the steering torque Th or the assist torque command value T1 when an event in which output from the turning motor is limited occurs.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 becomes 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.

[0004] In the output limit process, the control device limits the output of the steering motor, for example, by decreasing the current limit value as the steering speed of the steering wheel increases. The current limit value is the upper limit value of the current supplied to the steering motor. In the reaction force increase process, the control device increases the steering reaction force, for example, by increasing the damping component of the steering reaction force as compared with the case where the output limit process is not executed. The damping component of the steering reaction force increases as the steering speed increases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In a reaction force increase process executed in synchronization with an output limit process like the control device of Patent Document 1, when increasing the steering reaction force by increasing the damping component of the steering reaction force, there are the following concerns. That is, when the steering speed is slow, the steering reaction force may not increase sufficiently, and the driver of the vehicle may not notice that the output of the steering motor is restricted. MEANS FOR SOLVING THE PROBLEMS

[0007] The steering control device capable of solving the above problems controls the power supply to a reaction force motor that generates a steering reaction force applied to a steering wheel whose power transmission to a steered wheel of a vehicle is separated, based on a reaction force torque command value calculated according to the steering state of the steering wheel, and controls the power supply to a steering motor that generates a steering force for steering the steered wheel, based on a steering torque command value calculated according to the steering state of the steering wheel. The steering control device includes an assist torque command value calculation unit, an axial force torque calculation unit, a calculator, and a limit processing unit. The assist torque command value calculation unit is configured to calculate 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. The axial force torque calculation unit is configured to calculate 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 calculate an axial force torque by converting the calculated axial force into a torque with respect to the steering wheel. The calculator is configured to calculate the reaction force torque command value by subtracting the axial force torque from the assist torque command value. The limit processing unit is configured to limit the first state variable or the assist torque command value when an event in which the output of the steering motor is restricted occurs.

[0008] According to this configuration, when an event occurs in which the output of the steering motor is restricted, the first state variable or the assist torque command value is restricted. Since the reaction torque command value increases by the amount by which the first state variable or the assist torque command value is restricted, the steering reaction force applied to the steering wheel also increases. Therefore, the driver of the vehicle can recognize that the output of the steering motor is restricted by feeling the steering reaction force transmitted through the steering wheel as a tactile sensation. Accordingly, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor is restricted.

[0009] In the above-described steering control device, the restriction processing unit may be configured to execute a restriction process for restricting the first state variable when the event occurs. Further, the restriction process may include a plurality of restriction processes having different restriction modes for the first state variable, and the restriction processing unit may be configured to switch the restriction process to be executed according to the content of the event.

[0010] According to this configuration, depending on the content of the event in which the output of the steering motor is restricted, any one of a plurality of restriction processes having different restriction modes for the first state variable is executed. Therefore, depending on the content of the event in which the output of the steering motor is restricted, the value of the first state variable can be appropriately restricted.

[0011] In the above-described steering control device, the limiting process may include a first limiting process, a second limiting process, and a third limiting process. The first limiting process is a process of limiting the change range of the first state variable based on a limit value defined for the first state variable, or a process of limiting the value of the first state variable based on a conversion map that defines the relationship between the first state variable and the first state variable after limitation. The second limiting process is a process of setting a first dead zone, which is a range of values of the first state variable including zero, for the first state variable, and when the value of the first state variable reaches a value within the first dead zone, limiting the value of the first state variable to zero. The third limiting process is a process of setting a second dead zone, which is a range of absolute values of the first state variable defined by a boundary value greater than zero, for the absolute value of the first state variable, and after the absolute value of the first state variable reaches a value within the second dead zone, gradually increasing the second dead zone by gradually decreasing the boundary value, whereby the absolute value of the steering torque T h is limited to the boundary value.

[0012] According to this configuration, any one of the first to third limiting processes is executed according to the content of the event in which the output of the steering motor is limited. Therefore, the value of the first state variable can be appropriately limited according to the content of the event in which the output of the steering motor is limited. Further, since the limiting modes of the first to third limiting processes with respect to the first state variable are different, different steering sensations corresponding to the content of the event in which the output of the steering motor is limited can be given to the driver of the vehicle as a feel through the steering wheel. Therefore, the driver of the vehicle can recognize the content of the event in which the output of the steering motor is limited by feeling the steering reaction force through the steering wheel as a feel.

[0013] In the above-described steering control device, the event may include a first event in which the temperature of the steering motor rises excessively, a second event in which the voltage input to the steering control device drops, a third event in which a high load is continuously applied to the steering motor, and a fourth event in which it becomes difficult to supply power to any one of the two winding groups when the steering motor has two winding groups. In this case, the restriction processing unit may be configured to execute the first restriction processing when the first event or the fourth event occurs, execute the second restriction processing when the second event occurs, and execute the third restriction processing when the third event occurs.

[0014] According to this configuration, when the first event or the fourth event occurs, the first restriction processing is executed. By executing the first restriction processing, as a feel through the steering wheel, it is possible to give the driver of the vehicle a steering feeling as if the steering wheel has become heavy. The driver of the vehicle can recognize that the first event or the fourth event has occurred by feeling the steering reaction force through the steering wheel as a feel.

[0015] When the second event occurs, the second restriction processing is executed. By executing the second restriction processing, as a feel through the steering wheel, it is possible to give the driver of the vehicle a steering feeling with a catching feeling. The driver of the vehicle can recognize that the second event has occurred by feeling the steering reaction force through the steering wheel as a feel.

[0016] When the third event occurs, the third restriction processing is executed. By executing the third restriction processing, as a feel through the steering wheel, it is possible to give the driver of the vehicle a steering feeling as if the steering wheel is gradually pushed back, or a steering feeling with a butting feeling. The driver of the vehicle can recognize that the third event has occurred by feeling the steering reaction force through the steering wheel as a feel.

[0017] In the above-described steering control device, the steering motor may be configured such that when the event occurs, the output is limited by limiting the current supplied to the steering motor at a predetermined limiting ratio. In this case, the limiting processing unit may be configured to limit the assist torque command value at the same ratio as the limiting ratio when the event occurs.

[0018] According to this configuration, when an event occurs in which the output of the steering motor is limited, the assist torque command value is limited at the same ratio as the limiting ratio of the current of the steering motor. For this reason, the steering reaction force increases according to the degree of output limitation of the steering motor. Therefore, the driver of the vehicle can recognize that the output of the steering motor is limited by feeling the steering reaction force via the steering wheel as a tactile sensation.

[0019] In the above-described steering control device, the limiting processing unit may be configured to limit the assist torque command value based on a conversion map that defines the relationship between the assist torque command value and the assist torque command value after limitation when the event occurs.

[0020] According to this configuration, by using the conversion map, the assist torque command value after limitation can be easily obtained from the assist torque command value. Obtaining the assist torque command value after limitation using the conversion map means limiting the assist torque command value used for the control of the reaction motor.

[0021] In the above-described steering control device, the limiting processing unit may be configured to limit the assist torque command value based on a conversion map that defines the relationship between the first state variable and the assist torque command value after limitation when the event occurs.

[0022] According to this configuration, by using the conversion map, the assist torque command value after limitation can be easily obtained from the first state variable. Obtaining the assist torque command value after limitation using the conversion map means limiting the assist torque command value used for the control of the reaction force motor.

[0023] In the above-described steering control device, the first state variable may be the steering torque applied to the steering wheel. The second state variable may be at least one of the current of the steering motor and the target rotation angle of the pinion shaft that rotates in conjunction with the steering shaft.

[0024] As described above, the steering torque is an example of the first state variable that reflects the steering state of the steering wheel. Also, the current of the steering motor or the target rotation angle of the pinion shaft that rotates in conjunction with the steering shaft is an example of the second state variable that reflects the steering state of the steered wheels.

Advantages of the Invention

[0025] 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 limited.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0027] <The First Embodiment> Hereinafter, a first embodiment of the 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 gear mechanism 4. The steering mechanism 3 is a mechanism portion that is steered by a driver via a steering wheel 5. The steering gear mechanism 4 is a mechanism portion 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 gear 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 gear control device 1B is the steering gear mechanism 4. The steering gear control device 1B executes steering gear control. The steering gear control device 1B corresponds to a steering gear control unit.

[0028] The steering mechanism 3 has a steering shaft 11, a reaction force motor 12, and a speed reducer 13. The steering wheel 5 is integrally and 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.

[0029] The steering gear mechanism 4 has a pinion shaft 21, a steering shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. Further, 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. At both ends of the steering shaft 22, tie rods 25 are connected via rack ends 24 formed 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.

[0030] 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 via the transmission mechanism 32 into the axial movement of the steering shaft 22.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] A3. A hardware circuit combining configurations A1 and A2. The memory is a computer-readable medium that stores a program describing a process or an instruction 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.

[0035] The reaction force control device 1A captures 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 torsion 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.

[0036] 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.

[0037] 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.

[0038] 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 three previous configurations A1, A2, and A3, similar to the reaction force control device 1A.

[0039] 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.

[0040] 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.

[0041] <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.

[0042] 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 larger the absolute value of the steering torque Th and the lower the vehicle speed V, the larger the absolute value of the reaction force torque command value T. * Based on the steering torque Th and the vehicle speed V, it calculates the reaction force torque command value T. 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 larger the absolute value of the steering torque Th and the lower the vehicle speed V, the larger the absolute value of the reaction force torque command value T * becomes.

[0043] 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 the current sensor 54 provided in the power supply path to the reaction force motor 12. The current I * Based on the reaction force torque command value T, it 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 the current sensor 54 provided in the power supply path to the reaction force motor 12. The current I * Based on it, 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 the current sensor 54 provided in the power supply path to the reaction force motor 12. The current I a in the power supply path. aThe value is the value of the current supplied to the reaction force motor 12. The energization control unit 53 obtains 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 * .

[0044] <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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 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.

[0050] 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 * .

[0051] 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.

[0052] 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.

[0053] B4. When the steering motor 31 has two sets of winding groups, it becomes difficult to supply power to either one of the two sets of winding groups. 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 exceeds the 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 or the integrated value of the value of the current I. b b

[0054] 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 being lower than the voltage threshold. The voltage V b is the drawn-in voltage from the in-vehicle battery to the steering control device 1B. The voltage V b is also the voltage input to the steering control device 1. However, it may be conditional that the value of the voltage of the battery detected through a voltage sensor is lower than the voltage threshold. The battery is the main power source of the vehicle.

[0055] 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 state where the value of the current I supplied to the steering motor 31 exceeds the current threshold and continues for a predetermined time. The third event occurs, for example, when the steering wheel 6 hits an obstacle such as a curb during installation or when an end contact of the steering shaft 22 occurs. The end contact is that the rack end 24, which is the end of the steering shaft 22, hits the housing 23. b

[0056] ​​​ When the fourth determination condition is satisfied, the current limit processing unit 66 determines that the fourth event B4 has occurred. When the steering motor 31 has two winding groups, the steering control device 1B has two power supply systems and two control systems. The fourth determination condition includes, for example, an abnormality determination signal S generated by the abnormality determination unit of the steering control device 1B d indicating an abnormality in one of the two power supply systems or an abnormality in one of the two control systems. The power supply system includes a motor drive circuit. The control system includes a CPU and various sensors.

[0057] When an abnormality is detected in one of the two power supply systems or in one of the two control systems of the steering control device 1B, the steering control device 1B changes the drive mode of the steering motor 31 from the cooperative drive mode to the single-system drive mode. The cooperative drive mode is a drive mode when both systems are normal, and is a drive mode in which the two winding groups generate equal torque. The single-system drive mode is a drive mode when either one of the two systems is determined to be abnormal, and is a drive state in which only the winding group of the normal system among the two systems generates torque.

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

[0059] The energization control unit 64 receives the limit value I from the current limit processing unit 66 limWhen is calculated, the current amount supplied to the steering motor 31 is limited according to the limit value I lim The energization control unit 64 compares the absolute value of the current about to be supplied to the steering motor 31 with the limit value I lim When the absolute value of the current about to be supplied to the steering motor 31 is greater than the limit value I lim the absolute value of the current supplied to the steering motor 31 is limited to the limit value I lim When the absolute value of the current about to be supplied to the steering motor 31 is less than or equal to the limit value I lim the original current calculated through the feedback control of the current I b is directly supplied to the steering motor 31

[0060] The current limit processing unit 66 sets the value of the current limit flag F lim 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 lim 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 lim 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 lim 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

[0061] During the execution of the current limiting process for the steering motor 31, when a defined end condition is satisfied, the current limiting process for the steering motor 31 is terminated. The end condition may be, for example, that the previous first to fourth conditions are no longer satisfied, or it may be a condition individually set for each of the first to fourth events B1 to B4. When the end condition of the current limiting process is satisfied, the current limiting 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, and a calculator 84.

[0063] The steering torque limit processing unit 81 captures the steering torque T h detected through the torque sensor 42 and the value of the current limit flag F lim set by the current limiting unit 66. The steering torque limit processing unit 81 executes a steering torque limit process according to the value of the current limit flag F lim . The steering torque limit process is a process of limiting the steering torque T h in order to limit the output of the steering motor 31.

[0064] When the value of the current limit flag F lim is "0", the steering torque limit processing unit 81 does not execute the steering torque limit process. That is, the steering torque T h detected through the torque sensor 42 is directly used for the control of the steering motor 31. When the current of the steering motor 31 is limited, that is, when the value of the current limit flag F lim is any one of "1" to "4", the steering torque limit processing unit 81 executes the steering torque limit process. The steering torque limit processing unit 81 limits the steering torque T through the execution of the steering torque limit process.h By restricting the value of, a restricted steering torque T h_lim is generated. The steering torque limit processing unit 81 switches the method of limiting the value of the steering torque T lim according to the value of the current limit flag F h .

[0065] The assist torque command value calculation unit 82 takes in the steering torque T h from the steering torque limit processing unit 81 or the restricted steering torque T h_lim . Also, the assist torque command value calculation unit 82 takes in the vehicle speed V detected through the vehicle speed sensor 41. The assist torque command value calculation unit 82 calculates an assist torque command value T1 based on the steering torque T h or the restricted steering torque T h_lim and the vehicle speed V. 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. The assist torque is a force for assisting the steering of the steering wheel 5. 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 h is larger and the vehicle speed V is slower.

[0066] The axial force torque calculation unit 83 takes in the target pinion angle θ p * calculated by the target pinion angle calculation unit 62, the value of the current I b of the steering motor 31 detected through the current sensor 65, and the vehicle speed V detected through the vehicle speed sensor 41. 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 b of the steering motor 31, 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 a torque with respect to the steering shaft 11.

[0067] Note that the axial force torque calculation unit 83 uses the target pinion angle θ p* and the current I of the steering motor 31 b Based on only one of the values, the axial force acting on the steering shaft 22 may be calculated. Further, the axial force torque calculation unit 83 may use the target pinion angle θ p * Instead of, the pinion angle θ p or the steering angle θ s may be captured.

[0068] 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 subtracts the axial force torque T2 from the assist torque command value T1 to calculate the reaction force torque command value T * is calculated.

[0069] <Steering torque T h Value limiting method> Next, the value limiting method of the steering torque T h will be described. The steering torque limit processing unit 81 is capable of executing first to third limit processes on the steering torque T h The first to third limit processes are processes with different limiting modes for the steering torque T h The steering torque limit processing unit 81 executes one of the first to third limit processes according to the value of the current limit flag F lim The steering torque limit processing unit 81 executes the first limit process when the value of the current limit flag F lim is "1" or "4". The steering torque limit processing unit 81 executes the second limit process when the value of the current limit flag F lim is "2". The steering torque limit processing unit 81 executes the third limit process when the value of the current limit flag F lim is "3".

[0070] <First limit process> As shown in FIG. 4, the first limit process is a process of limiting the change range of the value of the steering torque T h The steering torque T hThe change range of the value is, for example, 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.

[0071] When the value of the steering torque T h is a positive value, the steering torque limit 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 limit 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 .

[0072] When the value of the steering torque T h is a negative value, the steering torque limit 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 limit processing unit 81 limits the value of the steering torque T h 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 .

[0073] Note that when the value of the steering torque T h is between the first upper limit value T h_UL1 and the first lower limit value Th_LL1 When it is within the range with, the steering torque T detected through the torque sensor 42 h is set as the value of the restricted steering torque T h_lim as it is.

[0074] The assist torque command value calculation unit 82 calculates the assist torque command value T1 using the restricted steering torque T h_lim obtained through the first restriction 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 restricted. As the absolute value of the assist torque command value T1 becomes smaller, the reaction force torque command value T * calculated by the calculator 84, and thus the steering reaction force, becomes larger.

[0075] When the first restriction 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, a steering feeling as if the steering wheel 5 has become heavier can be given to the driver of the vehicle. The weight of the steering wheel 5 is the same as the weight of the steering wheel 5 when no assist force is 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. 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 as a feel.

[0076] <Second Restriction Process> As shown in FIG. 5, the second restriction 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, it is a process of restricting the value of the steering torque T h to "0". The first dead zone is a steering torque T including "0" his within a certain range of values. The first dead zone is between the second upper limit value T h_UL2 and the 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.

[0077] 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 .

[0078] When the value of the input steering torque T h is a negative 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_LL2 falls below the second lower limit value T h_lim . After the value of the steering torque T h falls below the second lower limit value T h_LL2 , 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_limSet the value. However, due to the influence of the first dead zone, the restricted steering torque T h_lim does not follow the value of the original steering torque T h that varies sinusoidally. The value of the restricted steering torque T h_lim is smaller than the value of the original steering torque T h .

[0079] When the second restriction 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, it is possible to give the driver of the vehicle a steering feeling with a catching sensation. 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 as a feel.

[0080] <The third restriction process> As shown in FIG. 6, the third restriction process is to set 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, gradually decrease the limit value T h_LV to gradually increase the second dead zone, whereby the absolute value of the steering torque T h is restricted 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 contact occurs. The limit value T h_LV is stored in the memory.

[0081] For example, when end contact occurs and the state of the end contact 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 contact continues, the absolute value of the steering torque T h is maintained at the predetermined value.

[0082] 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 .

[0083] 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.

[0084] 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. 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 as a feel.

[0085] <Modification Example of the First Limiting Process> Incidentally, the steering torque limiting process unit 81 may execute the following process as the first limiting process. That is, the steering torque limiting process unit 81 may use the first conversion map M1 or the second conversion map M2 instead of the first upper limit value T h_UL1 and the first lower limit value T h_LL1 to calculate the limited steering torque T h_lim . The first conversion map M1 or the second conversion map M2 is stored in the memory.

[0086] As shown in FIG. 7, the first conversion map M1 is a two-dimensional map that defines the relationship between the absolute value of the steering torque T h and the absolute value of the limited steering torque T h_lim . The first conversion map M1 has the following characteristics. That is, when the absolute value of the steering torque T h gradually increases, after the absolute value of the steering torque T h reaches the first steering torque threshold value T h_1 , the absolute value of the limited steering torque T h_lim is maintained at the set value T h regardless of the absolute value of the steering torque T h_lim1 . However, the set value T h_lim1 is a constant value smaller than the absolute value of the steering torque T h . The first steering torque threshold value T h_1 is, for example, a value in the vicinity of "0".

[0087] When the first limiting process using the first conversion map M1 is executed, when the steering wheel 5 is steered beyond the small steering angle region, the steering reaction force becomes greater than the original steering reaction force corresponding to the steering torque T h Accordingly, 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 heavy. Further, assuming that the steering device 2 is an electric power steering device, it is possible to reproduce a steering feeling similar to when no assist force is applied to the steering wheel 5.

[0088] As shown in FIG. 8, the second conversion map M2 is a two-dimensional map that defines the relationship between the absolute value of the steering torque T h and the absolute value of the limiting steering torque T h_lim The second conversion map M2 has the following characteristics. That is, when the absolute value of the steering torque T h gradually increases, until the absolute value of the steering torque T h reaches the second steering torque threshold value T h_2 , the absolute value of the limiting steering torque T h_lim is maintained at "0". After the absolute value of the steering torque T h reaches the second steering torque threshold value T h_2 , the absolute value of the limiting steering torque T h_lim gradually increases. However, the absolute value of the limiting steering torque T h_lim is smaller than the absolute value of the steering torque T h . The second steering torque threshold value T h_2 is, for example, a value near "0".

[0089] When the first limiting process using the second conversion map M2 is executed and the steering wheel 5 is steered within the small steering angle region, a steering reaction force similar to when the absolute value of the steering torque T h is "0" is applied to the steering wheel 5. Accordingly, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feeling with a sense of hitting.

[0090] When the steering wheel 5 is steered beyond the small steering angle range, the steering reaction force decreases as the absolute value of the steering torque T h increases. 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 gradually becomes lighter.

[0091] <Effects of the First Embodiment> The first embodiment has the following effects. (1-1) The steering control device 1 includes a steering torque limit processing unit 81. When an event occurs in which the output of the steering motor 31 is restricted, the steering torque limit processing unit 81 restricts the value of the steering torque T h . As the value of the steering torque T h is restricted, the reaction torque command value T * increases, so 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 through the steering wheel 5. Accordingly, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor 31 is restricted.

[0092] (1-2) When an event occurs in which the output of the steering motor 31 is restricted, the value of the steering torque T h is restricted. Thereby, when it is assumed that the steering device 2 is an electric power steering device, it is possible to reproduce a steering feeling similar to the case where no assist force is applied to the steering wheel 5. Also, even if the steering speed of the steering wheel 5 is slow, as the value of the steering torque T h is restricted, the reaction torque command value T * , and thus the steering reaction force increases. Therefore, it is possible to surely notify the driver of the vehicle that the output of the steering motor 31 is restricted.

[0093] (1-3) When an event occurs in which the output of the steering motor 31 is restricted, the steering torque limit processing unit 81 restricts the value of the steering torque T hExecute a limiting process for limiting. The limiting process includes a plurality of limiting processes with different limiting modes for the steering torque T h The steering torque limiting processing unit 81 switches the limiting process to be executed according to the content of the event in which the output of the steering motor 31 is limited. According to this configuration, according to the content of the event in which the output of the steering motor 31 is limited, any one of a plurality of limiting processes with different limiting modes for the steering torque T h is executed. Therefore, according to the content of the event in which the output of the steering motor 31 is limited, the value of the steering torque T h can be appropriately limited.

[0094] (1-4) The limiting process for the steering torque T h includes, for example, a first limiting process, a second limiting process, and a third limiting process. According to this configuration, according to the content of the event in which the output of the steering motor 31 is limited, any one of the first to third limiting processes is executed. Therefore, according to the content of the event in which the output of the steering motor 31 is limited, the value of the steering torque T h can be appropriately limited. Also, since the limiting modes for the values of the steering torque T h of the first to third limiting processes are different, different steering feelings corresponding to the content of the event can be given to the driver of the vehicle as a feeling through the steering wheel 5. The driver of the vehicle can recognize the content of the event in which the output of the steering motor 31 is limited by feeling the steering reaction force through the steering wheel 5 as a feeling.

[0095] (1-5) When the first event B1 or the fourth event B4 occurs, the steering torque limiting processing unit 81 executes the first limiting process. By executing the first limiting process, a steering feeling as if the steering wheel 5 has become heavy can be given to the driver of the vehicle as a feeling through the steering wheel 5. 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 as a feeling.

[0096] (1-6) 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 feeling as a response 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 as a response.

[0097] (1-7) 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 feeling, as a response 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 as a response.

[0098] <Second Embodiment> Next, a second embodiment of the steering control device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 and 2 above. The configuration of the reaction torque command value calculation unit 52 in this embodiment is different from that of the first embodiment. Therefore, the same members and configurations as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0099] As shown in FIG. 9, the reaction torque command value calculation unit 52 has a command value limit processing unit 85 instead of the above-described steering torque limit processing unit 81. The command value limit processing unit 85 takes in the assist torque command value T1 calculated by the assist torque command value calculation unit 82 and the value of the current limit flag F lim set by the current limit processing unit 66. However, the current limit flag F limIt includes information indicating the limiting ratio LP of the current supplied to the steering motor 31. The limiting ratio LP is the amount of current actually supplied to the steering motor 31 out of the original current supplied from the energization control unit 64 to the steering motor 31. The limiting ratio LP is, for example, a value within the range of "0.1" or more and "1.0" or less, and is set in increments of "0.1". "0.1" corresponds to "10%".

[0100] The command value limiting processing unit 85 performs command value limiting processing according to the limiting ratio LP included in the current limiting flag F. lim The command value limiting processing is a process of limiting the assist torque command value T1 in order to limit the output of the steering motor 31. The command value limiting processing unit 85 does not perform the command value limiting processing when the value of the current limiting flag F lim is "0". That is, the assist torque command value T1 calculated by the assist torque command value calculation unit 82 is directly used for controlling the steering motor 31. The command value limiting processing unit 85 performs the command value limiting processing when the value of the current limiting flag F lim is any one of "1" to "4". The command value limiting processing unit 85 generates a limited assist torque command value T1 _lim by limiting the assist torque command value T1 through the execution of the command value limiting processing.

[0101] The command value limiting processing unit 85 limits the assist torque command value T1, for example, by the same ratio as the limiting ratio LP. For example, when the limiting ratio LP is "0.9", the limited assist torque command value T1 _lim becomes 90% of the original assist torque command value T1 calculated by the assist torque command value calculation unit 82. As the absolute value of the limited assist torque command value T1 _lim becomes smaller than the absolute value of the original assist torque command value T1, the reaction torque command value T * calculated by the arithmetic unit 84, and thus the steering reaction force increases.

[0102] When the command value limit process is executed, the steering reaction force becomes greater than the normal steering reaction force when the command value limit process is not executed. Therefore, as a feel through the steering wheel 5, it is possible to give the driver of the vehicle a steering feel in which the steering wheel 5 is heavier than normal. The driver of the vehicle can recognize that any one of the first to fourth events B1 to B4 has occurred by feeling the steering reaction force through the steering wheel 5 as a feel.

[0103] <Effect of the Second Embodiment> The second embodiment has the following effects. (2-1) The steering control device 1 has a command value limit processing unit 85. When an event occurs in which the output of the steering motor 31 is restricted, the command value limit processing unit 85 restricts the assist torque command value T1. Since the reaction torque command value T increases by the amount by which the assist torque command value T1 is restricted, 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 through the steering wheel 5 as a feel. Accordingly, it is possible to appropriately notify the driver of the vehicle that the output of the steering motor 31 is restricted. * When an event occurs in which the output of the steering motor 31 is restricted, the output of the steering motor 31 is restricted by restricting the current I supplied to the steering motor 31 at a predetermined restriction ratio LP. When an event occurs in which the output of the steering motor 31 is restricted, the command value limit processing unit 85 restricts the assist torque command value T1 at the same ratio as the restriction ratio LP. Therefore, the steering reaction force increases according to the degree of output restriction of the steering motor 31. Accordingly, the driver of the vehicle can recognize that the output of the steering motor 31 is restricted by feeling the steering reaction force through the steering wheel 5 as a feel.

[0104] (2-2) When an event occurs in which the output of the steering motor 31 is restricted, the current I supplied to the steering motor 31 is restricted at a predetermined restriction ratio LP, thereby restricting the output. b When an event occurs in which the output of the steering motor 31 is restricted, the command value limit processing unit 85 restricts the assist torque command value T1 at the same ratio as the restriction ratio LP. Therefore, the steering reaction force increases according to the degree of output restriction of the steering motor 31. Accordingly, the driver of the vehicle can recognize that the output of the steering motor 31 is restricted by feeling the steering reaction force through the steering wheel 5 as a feel.

[0105] When an event occurs in which the output of the steering motor 31 is restricted, the assist torque command value T1 is restricted. Therefore, even if the steering speed of the steering wheel 5 is slow, the reaction torque command value T increases by the amount by which the assist torque command value T1 is restricted. * As a result, the steering reaction increases. Therefore, the driver of the vehicle can be reliably informed that the output of the steering motor 31 is restricted.

[0106] <Other Embodiments> In addition, each embodiment may be implemented with the following modifications. · In the first embodiment, the steering torque limit processing unit 81 does not have to switch the method of limiting the value of the steering torque T according to the value of the current limit flag F lim among the first to third limit processes. In this case, for example, the steering torque limit processing unit 81 gradually decreases the absolute value of the steering torque T h regardless of whether the value of the current limit flag F lim is any of "1" to "4". The absolute value of the gradually decreasing steering torque T h is set as the absolute value of the limited steering torque T h h_lim . As the absolute value of the limited steering torque T h_lim gradually decreases, the reaction torque command value T * , and thus the steering reaction gradually increases. 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 gradually becomes heavier. The driver of the vehicle can recognize that any one of the first to fourth events B1 to B4 has occurred by feeling the steering reaction through the steering wheel 5 as a feel.

[0107] · In the second embodiment, when the current of the steering motor 31 is restricted, that is, when the current limit flag F lim ​When the value of [[ID=]] is any one of "1" to "4", a process for increasing the absolute value of the axial force torque T2 calculated by the axial force torque calculation unit 83 may be executed. The command value limit processing unit 85 increases the absolute value of the axial force torque T2, for example, by multiplying the absolute value of the axial force torque T2 by a gain. The gain is a value exceeding "1". In this way, when the current of the steering motor 31 is limited, a larger steering reaction force is applied to the steering wheel 5. For this reason, the driver of the vehicle can recognize that any one of the first to fourth events B1 to B4 has occurred by feeling the steering reaction force via the steering wheel 5 as a tactile sensation.

[0108] ·In the second embodiment, instead of the limit ratio LP, the command value limit processing unit 85 may use the third conversion map M3 to calculate the limit assist torque command value T1 _lim The third conversion map M3 is stored in the memory. The current limit flag F lim may not include information indicating the limit ratio LP of the current supplied to the steering motor 31.

[0109] As shown in FIG. 10, the third conversion map M3 is a two-dimensional map that defines the relationship between the absolute value of the assist torque command value T1 and the absolute value of the limit assist torque command value T1 _lim The third conversion map M3 has the following characteristics. That is, when the absolute value of the assist torque command value T1 gradually increases, after the absolute value of the assist torque command value T1 reaches the command value threshold T1 th , the absolute value of the limit assist torque command value T1 _lim is maintained at the set value T1 _lim1 regardless of the absolute value of the assist torque command value T1. However, the set value T1 _lim1 is a constant value smaller than the absolute value of the assist torque command value T1. The command value threshold T1 th is, for example, a value near "0".

[0110] When the command value limiting process using the third conversion map M3 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 Accordingly, 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 driver of the vehicle can recognize that any one of the first to fourth events B1 to B4 has occurred by feeling the steering reaction force through the steering wheel 5 as a feel

[0111] Also, by using the third conversion map M3, the limited assist torque command value T1 can be easily obtained from the assist torque command value T1 _lim Obtaining the limited assist torque command value T1 using the third conversion map M3 _lim is to limit the assist torque command value T1 used for the control of the reaction force motor 12

[0112] ·In the second embodiment, as the reaction torque command value calculation unit 52, a configuration in which the command value limiting process unit 85 is omitted may be adopted. In this case, the assist torque command value calculation unit 82 has the function of the command value limiting process unit 85. The assist torque command value calculation unit 82 takes in the value of the steering torque T h detected through the torque sensor 42 and the value of the current limit flag F lim set by the current limit processing unit 66. However, the current limit flag F lim does not necessarily include information indicating the current limit ratio LP of the current supplied to the steering motor 31

[0113] When the value of the current limit flag F lim is "0", the assist torque command value calculation unit 82 does not execute the command value limiting process. That is, the assist torque command value T1 calculated by the assist torque command value calculation unit 82 is directly used for the control of the steering motor 31. The command value limiting process unit 85 is the current limit flag F limWhen the value of _lim is any one of "1" to "4", the command value limit process is executed. The command value limit processing unit 85 generates a limited assist torque command value T1 by limiting the assist torque command value T1 through the execution of the command value limit process. The assist torque command value calculation unit 82 calculates the limited assist torque command value T1 using, for example, the fourth conversion map M4. The fourth conversion map M4 is stored in the memory. _lim

[0114] As shown in FIG. 11, the fourth conversion map M4 is a two-dimensional map that defines the relationship between the absolute value of the steering torque T h and the absolute value of the limited assist torque command value T1 _lim . The fourth conversion map M4 has the following characteristics. That is, when the absolute value of the steering torque T h gradually increases, after the absolute value of the steering torque T h reaches the third steering torque threshold value T h_3 , the absolute value of the limited assist torque command value T1 _lim gradually decreases as the absolute value of the steering torque T h increases. However, as the absolute value of the steering torque T h increases, the slope, which is the rate of change of the absolute value of the limited assist torque command value T1 h with respect to the absolute value of the steering torque T _lim , gradually becomes smaller.

[0115] The absolute value of the limited assist torque command value T1 _lim is the same as the absolute value of the assist torque command value T1 until the absolute value of the steering torque T h reaches the third steering torque threshold value T h_3 . The absolute value of the limited assist torque command value T1 _lim becomes smaller than the absolute value of the assist torque command value T1 after the absolute value of the steering torque T h reaches the third steering torque threshold value T h_3 . The third steering torque threshold value T h_3 is, for example, a value near "0".

[0116] ​ When the command value limiting process using the fourth conversion map M4 is executed and 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 . However, the steering reaction force gradually increases as the absolute value of the steering torque T h increases. 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 gradually becomes heavier. The driver of the vehicle can recognize that any one of the first to fourth events B1 to B4 has occurred by feeling the steering reaction force through the steering wheel 5

[0117] Also, by using the fourth conversion map M4, the limit assist torque command value T1 h can be easily obtained from the absolute value of the steering torque T _lim . Obtaining the limit assist torque command value T1 _lim using the fourth conversion map M4 means limiting the assist torque command value T1 used for the control of the reaction motor 12

Explanation of Signs

[0118] 1... Steering control device 5... Steering wheel 6... Steering wheel 12... Reaction motor 21... Pinion shaft 31... Steering motor 81... Steering torque limiting processing unit (limiting processing unit) 82... Assist torque command value calculation unit 83... Axial force torque calculation unit 84... Calculator 85... Command value limiting processing unit (limiting processing unit) M1... First conversion map M2... Second conversion map M3... Third conversion map M4... Fourth conversion map

Claims

1. Power supply to a reaction force motor that generates a steering reaction force applied to a steering wheel with power transmission separated from a steered wheel of a vehicle is controlled based on a reaction force torque command value calculated according to the steering state of the steering wheel, and power supply to a steering motor that generates a steering force for steering the steered wheel is controlled based on a steering torque command value calculated according to the steering state of the steering wheel. A steering control device configured as follows: An assist torque command value calculation unit configured to calculate 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; An axial force torque calculation unit configured to calculate 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 calculate an axial force torque by converting the calculated axial force into a torque with respect to the steering wheel; An arithmetic unit configured to calculate the reaction force torque command value by subtracting the axial force torque from the assist torque command value; A restriction processing unit configured to restrict the first state variable or the assist torque command value when an event occurs in which the output of the steering motor is restricted. A steering control device having the same.

2. The restriction processing unit is configured to execute a restriction process for restricting the first state variable when the event occurs. The restriction process includes a plurality of restriction processes with different restriction modes for the first state variable. The restriction processing unit is configured to switch the restriction process to be executed according to the content of the event. The steering control device according to Claim 1.

3. The restriction process includes a first restriction process, a second restriction process, and a third restriction process. The first restriction process is a process of restricting the change range of the first state variable based on a restriction value defined for the first state variable, or a process of restricting the value of the first state variable based on a conversion map that defines the relationship between the first state variable and the first state variable after restriction. The second limiting process sets a first dead zone, which is a range of values of the first state variable including zero, for the first state variable, and when the value of the first state variable reaches a value within the first dead zone, the process limits the value of the first state variable to zero. The third limiting process sets a second dead zone, which is a range of the absolute value of the first state variable defined by a boundary value greater than zero, for the absolute value of the first state variable, and after the absolute value of the first state variable reaches a value within the second dead zone, the second dead zone is gradually increased by gradually decreasing the boundary value. Thereby, the steering torque T ｈ The steering control device according to claim 2, which is a process of limiting the absolute value of to the boundary value.

4. The event includes a first event in which the temperature of the steering motor rises excessively, a second event in which the voltage input to the steering control device drops, a third event in which a high load is continuously applied to the steering motor, and when the steering motor has two winding groups, a fourth event in which it becomes difficult to supply power to either one of the two winding groups. When the first event or the fourth event occurs, the limiting processing unit executes the first limiting process. When the second event occurs, the limiting processing unit executes the second limiting process. The steering control device according to claim 3, wherein when the third event occurs, the limiting processing unit is configured to execute the third limiting process.

5. When the event occurs, the steering motor is configured such that the output is limited by limiting the current supplied to the steering motor at a predetermined limiting ratio. When the event occurs, the limiting processing unit is configured to limit the assist torque command value at the same ratio as the limiting ratio. The steering control device according to claim 1.

6. When the event occurs, the limiting processing unit is configured to limit the assist torque command value based on a conversion map that defines the relationship between the assist torque command value and the assist torque command value after limiting. The steering control device according to claim 1.

7. When the event occurs, the limiting processing unit is configured to limit the assist torque command value based on a conversion map that defines the relationship between the first state variable and the assist torque command value after limiting. The steering control device according to claim 1.

8. The first state variable is the steering torque applied to the steering wheel. The second state variable is at least one of the current of the steering motor and the target rotation angle of the pinion shaft that rotates in conjunction with the steering shaft. The steering control device according to any one of claims 1 to 7.

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