Steering control device

Abstract

To provide a steering control device that is able to inform a driver of a vehicle of a road surface condition.SOLUTION: A steering control device includes a reaction force control unit and a turning control unit. The reaction force control unit calculates a first road surface reaction force torque by converting a first condition variable reflecting a road surface condition into a torque with respect to a steering wheel. The reaction force control unit calculates a second road surface reaction force torque by converting a second condition variable reflecting a road surface condition into a torque with respect to the steering wheel. The reaction force control unit calculates a reference road surface reaction force torque T1 by adjusting the first road surface reaction force torque and the second road surface reaction force torque. The reaction force control unit calculates a reaction torque command value T*, which is a target value of a steering reaction force, by using the reference road surface reaction force torque T1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

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

[0003] The control device in Patent Document 1 controls the drive of a steering motor in response to the operation of a steering wheel. For example, the control device calculates a target steering angle based on the steering angle of the steering wheel, and controls the steering current based on the calculated target steering angle. The target steering angle is a target value for the rotation angle of the steering motor. The steering current is a current flowing through the steering motor.

[0004] The control device controls the drive of the reaction force motor in response to the operation of the steering wheel. The control device calculates a target reaction force current based on a detection signal of the steering current, and controls the reaction force current based on the calculated target reaction force current. The target reaction force current is a current command value for the reaction force motor. The reaction force current is a current flowing through the reaction force motor.

[0005] When calculating the target reaction force current, the control device performs a process to remove unnecessary signals from the detection signal of the turning current. The control device has a band-pass filter. The band-pass filter extracts signals of a predetermined frequency or higher from the detection signal of the turning current. The predetermined frequency is the upper limit of the frequency band of low-frequency vibrations caused by ruts or the like formed on the road surface. In other words, the band-pass filter removes low-frequency signals caused by ruts or the like from the detection signal of the turning current.

[0006] The detection signal of the steering current, from which low-frequency signals caused by ruts and the like have been removed, mainly contains vibration components caused by unevenness in the road surface. Therefore, it is possible to transmit vibrations caused by unevenness in the road surface to the driver of the vehicle while suppressing transmission of low-frequency vibrations caused by ruts and the like to the driver of the vehicle. The driver of the vehicle can recognize the road surface condition by the response via the steering wheel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-142704 Summary of the Invention [Problem to be solved by the invention]

[0008] Steering control devices are required to more appropriately communicate road surface conditions to the driver of the vehicle. [Means for solving the problem]

[0009] A steering control device that can solve the above problems includes a reaction force control unit configured to control a reaction motor that generates a steering reaction force applied to a steering wheel whose power transmission is separated from the steered wheels of a vehicle, and a steering control unit configured to control a steering motor that generates a steering force applied to a steering shaft that steers the steered wheels. The reaction force control unit is configured to execute the following processes: calculating a first road reaction torque by converting a first state variable that reflects road surface conditions into a torque applied to the steering wheel, calculating a second road reaction torque by converting a second state variable that reflects road surface conditions into a torque applied to the steering wheel, calculating a reference road reaction torque by reconciling the first road reaction torque and the second road reaction torque, and calculating a reaction torque command value that is a target value for the steering reaction force using the reference road reaction torque.

[0010] According to this configuration, the reaction torque command value, which is the target value of the steering reaction force, is calculated using the reference road reaction torque obtained by adjusting the first road reaction torque and the second road reaction torque. Therefore, by applying a steering reaction force according to the reaction torque command value to the steering wheel, it is possible to give the driver of the vehicle a sense of appropriate response according to the road surface condition.

[0011] In the above steering control device, the first state variable may be the axial force of the steered shaft detected by an on-board axial force sensor, and the second state variable may be the torque of the steered motor calculated based on a value of a current of the steered motor detected by an on-board current sensor. The reaction force control unit is configured to set the first road surface reaction torque as the reference road surface reaction torque when the axial force sensor and the current sensor are both normal, and to set the second road surface reaction torque as the reference road surface reaction torque when an abnormality occurs in the axial force sensor.

[0012] According to this configuration, when both the axial force sensor and the current sensor are normal, the first road reaction torque based on the axial force of the steered shaft detected by the axial force sensor is set as the reference road reaction torque. Therefore, by applying a steering reaction force according to the reaction torque command value to the steering wheel, it is possible to provide the driver of the vehicle with a more realistic steering feel that corresponds to the actual road surface conditions. When an abnormality occurs in the axial force sensor, the second road reaction torque based on the value of the current of the steering motor is set as the reference road reaction torque. Therefore, it is possible to continue applying a steering reaction force to the steering wheel even if an abnormality occurs in the axial force sensor.

[0013] In the above steering control device, the reaction force control unit may be configured to perform a process of calculating a final road reaction torque by extracting only frequency components important to steering feel from the reference road reaction torque by performing signal processing on the reference road reaction torque, and a process of calculating the reaction torque command value using the calculated final road reaction torque. In this case, the frequency components may be frequency components of vibrations generated between the road surface and the steered wheels that are necessary for the driver of the vehicle to recognize road surface conditions or the grip state of the steered wheels on the road surface.

[0014] According to this configuration, the reaction torque command value, which is the target value of the steering reaction force, is calculated using a final road reaction torque obtained by extracting only frequency components important to the steering feel from the reference road reaction torque. The extracted frequency components are frequency components of vibrations generated between the road surface and the steered wheels that are necessary for the vehicle driver to recognize the road surface condition or the grip state of the steered wheels on the road surface. Therefore, by applying a steering reaction force corresponding to the reaction torque command value to the steering wheel, the vehicle driver can recognize the road surface condition or the grip state of the steered wheels on the road surface by the response via the steering wheel.

[0015] In the steering control device, the vehicle driving modes may include a manual driving mode in which the steering wheel is steered and an automatic driving mode in which the steering wheel is not steered. In this case, the reaction force control unit may be configured not to execute the signal processing when the vehicle driving mode is the automatic driving mode.

[0016] According to this configuration, when the vehicle is in the autonomous driving mode, the steering wheel is not steered, so there is no need to inform the driver of the road surface conditions. Therefore, when the vehicle is in the autonomous driving mode, signal processing for the reference road surface reaction torque is not performed, thereby reducing the calculation load on the reaction force control unit.

[0017] In the above steering control device, the reaction force control unit may be configured to determine that the steered wheel has hit an obstacle or the steered shaft has hit an end when the value of the first road surface reaction torque or the second road surface reaction torque exceeds a torque threshold value for a specified determination time.

[0018] According to this configuration, it is possible to determine whether the steered wheels have hit an obstacle or the steered shaft has hit the end, based on the value of the first road surface reaction torque or the second road surface reaction torque.

[0019] In the above steering control device, the reaction force control unit may be configured to determine that at least one of the axial force sensor and the current sensor is abnormal when the value of the difference between the first road surface reaction torque and the second road surface reaction torque is outside a predetermined allowable range.

[0020] According to this configuration, it is possible to determine whether at least one of the axial force sensor and the current sensor is abnormal, based on the difference between the first road surface reaction torque and the second road surface reaction torque.

[0021] In the above steering control device, the axial force sensor may include a first axial force sensor provided at a first end of the steered shaft and configured to detect a first axial force of the steered shaft, and a second axial force sensor provided at a second end of the steered shaft and configured to detect a second axial force of the steered shaft.

[0022] According to this configuration, an axial force that more accurately reflects the actual road surface condition can be obtained based on the first axial force and the second axial force. [Effects of the Invention]

[0023] According to the steering control device of the present invention, road surface conditions can be more appropriately communicated to the driver of the vehicle. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a configuration diagram of a steering device in which an embodiment of a steering control device is installed. [Figure 2] 1 is a block diagram of a steering control device according to an embodiment. [Figure 3] FIG. 2 is a block diagram of a reaction torque command value calculation unit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of a steering control device will be described below. <Overall structure> As shown in FIG. 1, the control object of steering control device 1 is a steer-by-wire steering device 2. Steering device 2 has a steering mechanism 3 and a steering mechanism 4. Steering mechanism 3 is a mechanical part that is steered by a driver via steering wheel 5. Steering mechanism 4 is a mechanical part that steers steerable wheels 6 of a vehicle in response to steering of steering wheel 5. Steering control device 1 includes a reaction force control device 1A and a steering control device 1B. The control object of reaction force control device 1A is the steering mechanism 3. Reaction force control device 1A performs reaction force control. Reaction force control device 1A corresponds to a reaction force control section. The control object of steering control device 1B is the steering mechanism 4. Steering control device 1B performs steering control. Steering control device 1B corresponds to a steering control section.

[0026] The steering mechanism 3 has a steering shaft 11, a reaction motor 12, and a reducer 13. The steering wheel 5 is connected to the steering shaft 11 so as to be rotatable integrally therewith. The reaction motor 12 is a source of a steering reaction force applied to the steering shaft 11. The steering reaction force is a force in the opposite direction to the steering direction of the steering wheel 5. The reaction motor 12 is, for example, a three-phase brushless motor. The reducer 13 decelerates the rotation of the reaction motor 12 and transmits the decelerated rotation to the steering shaft 11.

[0027] The steering mechanism 4 has a pinion shaft 21, a steered shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 also accommodates the steered shaft 22 so that it can reciprocate. Power transmission between the steered shaft 22 and the steering wheel 5 is separated. The pinion shaft 21 is arranged to intersect with the steered shaft 22. Pinion teeth 21a of the pinion shaft 21 mesh with rack teeth 22a of the steered shaft 22. Tie rods 25 are connected to both ends of the steered shaft 22 via rack ends 24 made up of ball joints. The ends of the tie rods 25 are connected to a knuckle (not shown) to which the steered wheels 6 are assembled.

[0028] The steering mechanism 4 comprises 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 steered wheels 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 axial movement of the steering shaft 22.

[0029] The steered shaft 22 moves in the axial direction, and the steered angle θ of the steered wheels 6 w The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steered shaft 22. Therefore, the pinion shaft 21 rotates in conjunction with the movement of the steered shaft 22. The pinion shaft 21 is a shaft or a rotating body that rotates in conjunction with the steering operation of the steered wheels 6.

[0030] 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 components 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 memory.

[0031] A2. One or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that perform at least some of the processing. The ASIC includes a CPU and memory.

[0032] A3. A hardware circuit that combines configurations A1 and A2. The memory is a computer-readable medium that stores a program that describes processes or instructions for the computer. In this embodiment, the computer is a CPU. The memory includes RAM (random access memory) and ROM (read only memory). The CPU executes the program stored in the memory at a predetermined calculation cycle to perform various controls.

[0033] The reaction force control device 1A receives detection results from sensors mounted on the vehicle, including a vehicle speed sensor 41, a torque sensor 42, a rotation angle sensor 43, and an axial force sensor 44. The vehicle speed sensor 41 detects the vehicle speed V. The vehicle speed V is one of the state variables that reflects the running state of the vehicle.

[0034] The torque sensor 42 is provided on the steering shaft 11. The torque sensor 42 is located on the steering wheel 5 side of the connecting portion of the steering shaft 11 to which the reducer 13 is connected. 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 a torsion bar 42a provided on the steering shaft 11. For example, the steering torque Th is a positive value when the steering wheel 5 is steered right from the neutral position, and a negative value when the steering wheel 5 is steered left from the neutral position. The neutral position is the position of the steering wheel 5 corresponding to the straight-ahead state of the vehicle. The steering torque Th is one of the state variables that reflect the steering state of the steering wheel 5.

[0035] The rotation angle sensor 43 is provided on the reaction motor 12. The rotation angle sensor 43 detects the rotation angle θ of the reaction motor 12. a The rotation angle θ of the reaction motor 12 is detected. a For example, when the steering wheel 5 is steered to the right from the neutral position, θ is a positive value, and when the steering wheel 5 is steered to the left from the neutral position, θ is a negative value.

[0036] Axial force sensor 44 is provided at a first end of steered shaft 22. The first end is, for example, the right end of steered shaft 22 in the direction of travel of the vehicle. Axial force sensor 44 detects axial force F1 acting on steered shaft 22. Axial force sensor 44 is, for example, a load cell. A load cell is a transducer that converts the load to be measured into an electrical signal proportional to the load. Axial force F1 corresponds to a first state variable that reflects the road surface condition.

[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, the rotation angle sensor 43, and the axial force sensor 44. The reaction force control device 1A controls the power supply to the reaction force motor 12 so that the reaction force motor 12 generates a steering reaction force corresponding to the steering torque Th. The steering torque Th is the torque applied to the steering wheel 5 when the steering wheel 5 is steered.

[0038] The steering control device 1B controls the operation of the steering motor 31. Like the reaction force control device 1A, the steering control device 1B has a processing circuit including any one of the three components A1, A2, A3 described above.

[0039] The steering control device 1B takes in the detection results of sensors mounted on the vehicle. The sensors include a rotation angle sensor 45. The rotation angle sensor 45 is provided in the steering motor 31. The rotation angle sensor 45 detects a rotation angle θ of the steering motor 31. b The rotation angle θ of the steering motor 31 is detected. b For example, when the steering wheel 5 is steered to the right from the neutral position, θ is a positive value, and when the steering wheel 5 is steered to the left from the neutral position, θ is a negative value.

[0040] The steering control device 1B uses the detection result of the rotation angle sensor 45 to control the operation of the steering motor 31. The steering control device 1B controls the supply of power to the steering motor 31 so that the steered wheels 6 are turned in accordance with the steering state of the steering wheel 5.

[0041] <Configuration of 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 an energization control unit 53.

[0042] The steering angle calculation unit 51 calculates the rotation angle θ of the reaction force motor 12 detected through the rotation angle sensor 43. a The steering angle calculation unit 51 takes in the rotation angle θ of the reaction force motor 12. aBased on this, the steering angle θ of the steering wheel 5 s Calculate the following.

[0043] Reaction torque command value calculation unit 52 takes in steering torque Th detected by torque sensor 42 and vehicle speed V detected by vehicle speed sensor 41. Reaction torque command value calculation unit 52 also takes in current I of steering motor 31 detected by current sensor 65 provided in the power supply path to steering motor 31. b and the axial force F1 detected by the axial force sensor 44. The reaction torque command value calculation unit 52 calculates the current I b The reaction torque command value T is calculated based on the steering torque Th, the vehicle speed V, and the axial force F1. * Calculate the reaction torque command value T * is the target value of the steering reaction force to be generated by 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 reaction torque command value T * The absolute value of the current I of the steering motor 31 increases as the absolute value of the steering torque Th increases and as the vehicle speed V decreases. b The value of corresponds to the second state variable that reflects the road surface condition.

[0044] The reaction torque command value calculation unit 52 receives the vehicle state determination flag FG. The vehicle state determination flag FG is an electrical signal generated by a vehicle control device that controls the control devices of various in-vehicle systems. The vehicle control device is also a control device of an automatic driving system in which the system takes over the driving of the vehicle. The vehicle state determination flag FG is, for example, an electrical signal that indicates the driving mode of the vehicle. The driving modes include a manual driving mode and an automatic driving mode. It is possible to switch between the automatic driving mode and the manual driving mode by operating an automatic driving switch provided in the driver's seat or the like.

[0045] When the driving mode is the manual driving mode, the driver is the entity that executes the operation to steer the steered wheels 6. In other words, when the driving mode is the manual driving mode, the steering wheel 5 is steered by the driver of the vehicle. When the driving mode is the automatic driving mode, the entity that executes the operation to steer the steered wheels 6 is the vehicle control device, not the driver. In other words, when the driving mode is the automatic driving mode, the steering wheel 5 is not steered by the driver of the vehicle. The reaction torque command value calculation unit 52 calculates the reaction torque command value T * Change the calculation method.

[0046] The energization control unit 53 calculates the reaction torque command value T * The power supply control unit 53 receives the reaction torque command value T * Specifically, the power supply control unit 53 supplies the reaction force motor 12 with power according to the reaction force torque command value T * The current control unit 53 calculates a current command value for the reaction force motor 12 based on the current I generated in the power supply path through a current sensor 54 provided in the power supply path for the reaction force motor 12. a Detect the value of the current I a The value of is the value of the current supplied to the reaction motor 12. The current control unit 53 calculates the current command value and the current I a The deviation from the value of the reaction torque command value T is calculated, and the power supply to the reaction motor 12 is controlled so as to eliminate the deviation. * A torque corresponding to the

[0047] <Configuration of 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 has a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit 63, and an energization control unit 64.

[0048] The pinion angle calculation unit 61 calculates the rotation angle θ of the steering motor 31 detected through the rotation angle sensor 45. bThe rotation angle θ b Based on the pinion angle θ p Calculate the pinion angle θ p is the rotation angle of pinion shaft 21, and is one of the state variables that reflect the steering state of steered wheels 6. Steering motor 31 and pinion shaft 21 are linked via transmission mechanism 32, conversion mechanism 33, and steering shaft 22. Therefore, the rotation angle θ of steering motor 31 b and pinion angle θ p By utilizing this correlation, the rotation angle θ of the steering motor 31 is b From pinion angle θ p The pinion shaft 21 is meshed with the steering shaft 22. Therefore, the pinion angle θ p There is also a correlation between the pinion angle θ and the amount of movement of the steering shaft 22. p is the steering angle θ of the steered wheels 6 w This is a value that reflects the

[0049] The target pinion angle calculation unit 62 calculates the steering angle θ calculated by the steering angle calculation unit 51. s The steering angle θ s Based on the target pinion angle θ p * Calculate the target pinion angle θ p * is the pinion angle θ p The target pinion angle calculation unit 62 calculates the target pinion angle θ so as to realize a steering angle ratio set according to product specifications, etc. p * The steering angle ratio is calculated by the steering angle θ s steering angle θ w is the ratio of

[0050] The target pinion angle calculation unit 62 sets a steering angle ratio according to the vehicle running state, such as the vehicle speed V, and calculates the target pinion angle θ according to the set steering angle ratio. p * The target pinion angle calculation unit 62 may calculate the steering angle θ as the vehicle speed V decreases. s steering angle θw The target pinion angle θ p * As the vehicle speed V increases, the target pinion angle calculation unit 62 calculates the steering angle θ s steering angle θ w The target pinion angle θ p * The target pinion angle calculation unit 62 calculates the steering angle θ s The correction angle for the steering angle θ is calculated. s By adding to the target pinion angle θ according to the steering angle ratio p * Calculate the following.

[0051] Depending on the product specifications, the target pinion angle calculation unit 62 may calculate the target pinion angle θ so that the steering angle ratio becomes "1:1" regardless of the running state of the vehicle. p * The following may be calculated.

[0052] The pinion angle feedback control unit 63 receives the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * and the pinion angle θ calculated by the pinion angle calculation unit 61. p The pinion angle feedback control unit 63 receives the pinion angle θ p is the target pinion angle θ p * The pinion angle θ p Through the feedback control of the steering torque command value T p * Calculate 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.

[0053] The power supply control unit 64 controls the steering torque command value T p * Specifically, the power supply control unit 64 supplies the steering motor 31 with electric power according to the steering torque command value Tp * The current control unit 64 calculates a current command value for the steering motor 31 based on the current I generated in the power supply path through a current sensor 65 provided in the power supply path for the steering motor 31. b Detect the value of the current I b The value of is a value of the current supplied to the steering motor 31, and is one of the state variables that reflect the steering state of the steered wheels 6. The current control unit 64 calculates the current command value and the current I b The deviation from the value of the steering torque command value T is calculated and the power supply to the steering motor 31 is controlled so as to eliminate the deviation. p * A torque corresponding to the

[0054] <Configuration of 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 has a road surface reaction torque calculation unit 52A, a signal processing unit 52B, and a reaction torque arbitration unit 52C.

[0055] Road surface reaction force torque calculation unit 52A calculates the axial force F1 detected by axial force sensor 44 and the current I of steering motor 31 detected by current sensor 65. b The value of the axial force F1 changes due to disturbances acting on the steered wheels 6 according to road surface conditions such as road friction resistance. b The value of the target pinion angle θ p * and the actual pinion angle θ p That is, the value of the axial force F1 and the current I of the steering motor 31 change depending on the difference between the b The value of is a road surface reaction force, which is a reaction force from the road surface acting on the steered wheels 6, that is, one of the state variables that reflects the road surface condition.

[0056] Road surface reaction torque calculation unit 52A calculates a first road surface reaction torque by converting axial force F1 detected by axial force sensor 44 into torque with respect to steering shaft 11. Road surface reaction torque calculation unit 52A calculates a first road surface reaction torque by converting axial force F1 detected by axial force sensor 44 into torque with respect to steering shaft 11. b The torque generated by steering motor 31 is calculated based on the value of (a), and the calculated torque of steering motor 31 is converted into a torque for steering shaft 11 to calculate the second road surface reaction torque.

[0057] The road reaction torque calculation unit 52A arbitrates between the first road reaction torque and the second road reaction torque. That is, the road reaction torque calculation unit 52A uses either the first road reaction torque or the second road reaction torque as the reference road reaction torque T1. For example, if the axial force sensor 44 and the current sensor 65 are both normal, the road reaction torque calculation unit 52A uses the first road reaction torque as the reference road reaction torque T1. If an abnormality occurs in the axial force sensor 44, the road reaction torque calculation unit 52A uses the second road reaction torque as the reference road reaction torque T1. An abnormality in the axial force sensor 44 includes a disruption of the electrical signal from the axial force sensor 44. The reference road reaction torque T1 contains various vibration frequency components depending on the road surface condition.

[0058] Signal processing unit 52B receives reference road reaction torque T1 calculated by road reaction torque calculation unit 52A and calculates final road reaction torque T2 based on the received reference road reaction torque T1. Reference road reaction torque T1 is the basis for calculating final road reaction torque T2. Final road reaction torque T2 is the final road reaction torque used to control steering motor 31.

[0059] The signal processing unit 52B has a filter such as a band-pass filter. The filter extracts frequency components important for the steering feel from the reference road reaction torque T1 and removes frequency components that may cause anxiety to the vehicle driver. The frequency components important for the steering feel are, for example, frequency components of vibrations generated between the road surface and the steered wheels 6 that are necessary for the vehicle driver to recognize the road surface condition or the grip state of the steered wheels on the road surface. The frequency components that may cause anxiety to the vehicle driver are, for example, frequency components of excessive vibrations generated between the road surface and the steered wheels 6 that are caused by ruts or the like. The final road reaction torque T2 is generated by the signal processing unit 52B applying filter processing to the reference road reaction torque T1.

[0060] The signal processing unit 52B receives the vehicle state determination flag FG and determines whether to apply filtering to the reference road surface reaction torque T1 according to the received vehicle state determination flag FG. When the vehicle state determination flag FG indicates that the manual driving mode has been selected as the vehicle driving mode, the signal processing unit 52B applies filtering to the reference road surface reaction torque T1. When the vehicle state determination flag FG indicates that the autonomous driving mode has been selected as the vehicle driving mode, the signal processing unit 52B does not apply filtering to the reference road surface reaction torque T1. This is because when the vehicle driving mode is the autonomous driving mode, the steering wheel 5 is not steered by the vehicle driver, and therefore there is no need to apply an appropriate steering reaction force to the steering wheel 5 according to the road surface condition.

[0061] The reaction torque arbitration unit 52C takes in the steering torque Th detected by the torque sensor 42, the vehicle speed V detected by the vehicle speed sensor 41, and the final road reaction torque T2 generated by the signal processing unit 52B. The reaction torque arbitration unit 52C calculates an assist torque command value based on the steering torque Th and the vehicle speed V. The assist torque command value 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 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 increases as the absolute value of the steering torque Th increases and the vehicle speed V decreases. The reaction torque arbitration unit 52C calculates the reaction torque command value T by subtracting the final road reaction torque T2 from the assist torque command value. * Calculate the following.

[0062] <Functions and Effects of the Embodiment> This embodiment provides the following functions and effects. (1) The reaction force control device 1A controls the first road surface reaction torque based on the axial force F1 and the current I of the steering motor 31. b The reaction force control device 1A calculates a reference road surface reaction torque T1 by adjusting the reference road surface reaction torque T1 and a second road surface reaction torque T2 based on the value of the reference road surface reaction torque T1. * Therefore, the reaction torque command value T * By applying a steering reaction force according to the road surface condition to the steering wheel 5, the driver of the vehicle can be given an appropriate sense of response according to the road surface condition. Also, the driver of the vehicle can recognize the road surface condition as a response via the steering wheel 5.

[0063] (2) When both the axial force sensor 44 and the current sensor 65 are normal, the reaction force control device 1A sets the first road surface reaction torque based on the axial force F1 as the reference road surface reaction torque T1. When an abnormality occurs in the axial force sensor 44, the reaction force control device 1A sets the first road surface reaction torque based on the axial force F1 as the reference road surface reaction torque T1. bThe second road reaction torque based on the value of is set as the reference road reaction torque T1.

[0064] According to this configuration, when both the axial force sensor 44 and the current sensor 65 are normal, the first road reaction torque based on the axial force F1 is set as the reference road reaction torque T1. The axial force F1 does not include the frictional component or viscous component of the transmission mechanism 32 and the conversion mechanism 33. Therefore, the reaction torque command value T based on the axial force F1 is * By applying a steering reaction force to steering wheel 5 according to the actual road surface condition, the driver of the vehicle can be given a more realistic steering feel according to the actual road surface condition. In addition, it is possible to prevent the frictional or viscous sensation of transmission mechanism 32 and conversion mechanism 33 from being conveyed to the driver of the vehicle. The frictional or viscous sensation of transmission mechanism 32 and conversion mechanism 33 is information that does not need to be conveyed to the driver of the vehicle. In contrast, when an abnormality occurs in axial force sensor 44, the current I of steering motor 31 b The second road surface reaction torque based on the value of is set as the reference road surface reaction torque T1. Therefore, even if an abnormality occurs in the axial force sensor 44, the steering reaction force can continue to be applied to the steering wheel 5.

[0065] (3) The reaction force control device 1A performs signal processing on the reference road reaction torque T1 to extract only frequency components important to the steering feel from the reference road reaction torque T1 and calculates the final road reaction torque T2. The reaction force control device 1A uses the final road reaction torque T2 to calculate the reaction torque command value T * The frequency components that are important for the steering feel are the frequency components of the vibrations that occur between the road surface and the steered wheels 6, which are necessary for the driver of the vehicle to recognize the road surface condition or the grip state of the steered wheels 6 on the road surface. For this reason, the reaction torque command value T * By applying a steering reaction force to the steering wheel according to the steering angle, the driver of the vehicle can recognize the road surface condition or the grip state of the steered wheels on the road surface by the response felt through the steering wheel.

[0066] (4) The vehicle has a manual driving mode in which the steering wheel 5 is steered and an automatic driving mode in which the steering wheel 5 is not steered. When the vehicle's driving mode is the automatic driving mode, the reaction force control device 1A does not perform signal processing on the reference road reaction torque T1. When the vehicle's driving mode is the automatic driving mode, the steering wheel 5 is not steered, so there is no need to notify the vehicle driver of the road surface conditions. Therefore, when the vehicle's driving mode is the automatic driving mode, not performing signal processing on the reference road reaction torque T1 can reduce the calculation load on the reaction force control device 1A.

[0067] (5) Reaction force control device 1A can determine whether or not steered wheels 6 have hit an obstacle or end hit of steered shaft 22 has occurred based on the value of the first road reaction torque or the second road reaction torque. An obstacle hit occurs, for example, when steered wheels 6 hit an obstacle such as a curb while steering the vehicle stationary. End hit occurs when rack end 24, which is the end of steered shaft 22, hits housing 23. Reaction force control device 1A determines that steered wheels 6 have hit an obstacle or end hit of steered shaft 22 has occurred when, for example, the value of the first road reaction torque or the second road reaction torque exceeds a torque threshold value for a specified determination time. This is because, when steered wheels 6 have hit an obstacle or end hit of steered shaft 22, axial force F1 of steered shaft 22 and current I of steering motor 31 are measured. b is an excessively large value.

[0068] (6) The reaction force control device 1A can determine whether at least one of the axial force sensor 44 and the current sensor 65 is abnormal based on the difference between the first road reaction force torque and the second road reaction force torque. When the value of the difference between the first road reaction force torque and the second road reaction force torque is within a predetermined allowable range, the reaction force control device 1A determines that both the axial force sensor 44 and the current sensor 65 are normal. When the value of the difference between the first road reaction force torque and the second road reaction force torque is outside the predetermined allowable range, the reaction force control device 1A determines that at least one of the axial force sensor 44 and the current sensor 65 is abnormal. This is based on the fact that when both the axial force sensor 44 and the current sensor 65 are operating normally, the first road reaction force torque and the second road reaction force torque will basically be approximate values.

[0069] <Other embodiments> This embodiment may be modified as follows. As shown in FIG. 1, steered shaft 22 may have another axial force sensor 46 in addition to axial force sensor 44. Axial force sensor 44 detects axial force F2 acting on steered shaft 22. Axial force sensor 46 is provided at a second end of steered shaft 22. The second end is the end opposite to the first end of steered shaft 22, for example, the left end of steered shaft 22 in the direction of travel of the vehicle. One axial force sensor 44 corresponds to the first axial force sensor, and the other axial force sensor 46 corresponds to the second axial force sensor. The axial force F1 detected by one axial force sensor 44 corresponds to the first axial force, and the axial force F2 detected by the other axial force sensor 46 corresponds to the second axial force.

[0070] When the steering wheel 5 is held in the neutral position, no axial force acts on the steered shaft 22. When the steering wheel 5 is steered right from the neutral position, one axial force sensor 44 generates an electric signal corresponding to the axial force in the compression direction, and the other axial force sensor 46 generates an electric signal corresponding to the axial force in the tension direction. When the steering wheel 5 is steered left from the neutral position, one axial force sensor 44 generates an electric signal corresponding to the axial force in the tension direction, and the other axial force sensor 46 generates an electric signal corresponding to the axial force in the compression direction. In other words, when the steering wheel 5 is steered right or left from the neutral position, the axial force F1 detected by one axial force sensor 44 and the axial force F2 detected by the other axial force sensor 46 have opposite signs.

[0071] Therefore, road reaction force torque calculation unit 52A can obtain an axial force that more accurately reflects the actual road surface conditions, based on the two axial forces F1 and F2. By setting the first road reaction force torque based on an axial force that takes into account the two axial forces F1 and F2 as reference road reaction force torque T1, a more accurate steering reaction force that corresponds to the actual road surface conditions is applied to steering wheel 5. Furthermore, reaction force control device 1A can determine the steering direction of steered wheels 6, based on the signs of the two axial forces F1 and F2. Furthermore, reaction force control device 1A can determine on which side, left or right with respect to the vehicle's traveling direction, the steered wheels 6 have hit an obstacle or the end of steered shaft 22 has hit the obstacle, based on the signs of the two axial forces F1 and F2.

[0072] As shown in FIG. 1, the steering mechanism 4 may have a rotation angle sensor 47. The rotation angle sensor 47 detects a pinion angle θ p In this case, the road surface reaction torque calculation unit 52A calculates the pinion angle θ detected through the rotation angle sensor 47. p The axial force F1 may be calculated based on the following. A torque corresponding to the amount of movement of the steered shaft 22 acts on the pinion shaft 21. The pinion angle θ p is a state variable that reflects the axial force acting on the steering shaft 22.

[0073] Steering motor 31 may have a torque sensor. In this case, road surface reaction force torque calculation unit 52A may calculate second road surface reaction force torque by converting the torque of steering motor 31 detected by the torque sensor into torque with respect to steering shaft 11.

[0074] The road reaction force torque calculation unit 52A may mix the first road reaction force torque and the second road reaction force torque depending on the running state of the vehicle. For example, the road reaction force torque calculation unit 52A sets the distribution ratio for the first road reaction force torque and the second road reaction force torque individually depending on the vehicle speed V. The road reaction force torque calculation unit 52A calculates the reference road reaction force torque T1 by adding the values ​​obtained by multiplying the first road reaction force torque and the second road reaction force torque by the distribution ratios that are individually set.

[0075] In this specification, "at least one of A and B" means "A only, B only, or both A and B." [Explanation of symbols]

[0076] 1...Steering control device 1A...Reaction force control device (reaction force control unit) 1B...Steering control device (steering control section) 5...Steering wheel 6...Steering wheel 12...Reaction motor 22...Steering shaft 31...Steering motor 44...Axial force sensor (first axial force sensor) 46...Axial force sensor (second axial force sensor) 65...Current sensor

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 whose power transmission is separated from that of steered wheels of the vehicle; a steering control unit configured to control a steering motor that generates a steering force applied to a steering shaft that steers the steered wheels, The reaction force control unit is a process of calculating a first road surface reaction torque by converting a first state variable reflecting a road surface condition into a torque applied to the steering wheel; a process of calculating a second road reaction torque by converting a second state variable reflecting a road surface condition into a torque applied to the steering wheel; a process of calculating a reference road surface reaction torque by adjusting the first road surface reaction torque and the second road surface reaction torque; and a process of calculating a reaction torque command value, which is a target value of the steering reaction force, using the reference road surface reaction torque.

2. the first state variable is an axial force of the steering shaft detected by an axial force sensor mounted on the vehicle, the second state variable is a torque of the steering motor calculated based on a value of a current of the steering motor detected by an on-vehicle current sensor, 2. The steering control device according to claim 1, wherein the reaction force control unit is configured to set the first road surface reaction torque as the reference road surface reaction torque when the axial force sensor and the current sensor are both normal, and to set the second road surface reaction torque as the reference road surface reaction torque when an abnormality occurs in the axial force sensor.

3. The reaction force control unit is a process of extracting only frequency components important to steering feel from the reference road reaction torque by performing signal processing on the reference road reaction torque, and calculating a final road reaction torque; and calculating the reaction torque command value using the calculated final road surface reaction torque, 3. A steering control device according to claim 1, wherein the frequency components are frequency components of vibrations generated between the road surface and the steered wheels that are required for the driver of the vehicle to recognize the road surface condition or the grip state of the steered wheels on the road surface.

4. The driving modes of the vehicle include a manual driving mode in which the steering wheel is steered and an automatic driving mode in which the steering wheel is not steered, The steering control device according to claim 3 , wherein the reaction force control unit is configured not to execute the signal processing when the driving mode of the vehicle is the automatic driving mode.

5. 3. The steering control device according to claim 1, wherein the reaction force control unit is configured to determine that the steered wheel has hit an obstacle or the steered shaft has hit an end when the value of the first road surface reaction torque or the second road surface reaction torque exceeds a torque threshold value for a predetermined determination time.

6. 3. The steering control device according to claim 2, wherein the reaction force control unit is configured to determine that at least one of the axial force sensor and the current sensor is abnormal when a value of a difference between the first road surface reaction torque and the second road surface reaction torque is outside a predetermined allowable range.

7. The axial force sensor is a first axial force sensor provided at a first end of the steered shaft and configured to detect a first axial force of the steered shaft; 3. The steering control device according to claim 2, further comprising: a second axial force sensor provided at a second end of the steered shaft and configured to detect a second axial force of the steered shaft.

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