Steering control unit

Abstract

This invention discloses a steering control device. In the steering control device configured to control a steering system (2), a motor torque is used in the steering system (2) to change the steering torque required to turn the steering wheel (3). The processing circuit includes a first calculation state and a second calculation state. In the first calculation state, a calculated lag component for adding a first lag characteristic to the torque component is calculated. In the second calculation state, a calculated lag component for adding a second lag characteristic to the torque component is calculated. In the second calculation state after a change from the first calculation state, the processing circuit calculates a calculated lag component such that the value of the calculated lag component at the moment of change from the first calculation state can be maintained. It then calculates a value corresponding to the origin in the second lag characteristic and uses the calculated value as the origin to calculate the calculated lag component.

Description

Technical Field

[0001] This invention relates to a steering control device. Background Technology

[0002] A steer-by-wire system already exists as a type of steering system in which the power transmission path between the steering unit, which is steered by the driver, and the rotating unit, which rotates the wheels according to the driver's steering, is severed. In this type of steering system, road surface information, such as the road surface reaction force applied to the wheels, is not mechanically transmitted to the steering wheel. Therefore, the steering control device that controls this steering system performs control such that the road surface information is transmitted to the driver by controlling the steering-side actuators located in the steering unit to apply a steering reaction force to the steering wheel, taking into account the road surface information.

[0003] For example, the steering control device described in Japanese Unexamined Patent Application Publication No. 2020-142596 (JP 2020-142596 A) considers the axial force acting on the rotation shaft provided in the rotation unit to determine the reaction force. In the steering control device described in JP2020-142596 A, the angular axial force based on the target rotation angle for controlling the rotation angle of the rotating wheel, calculated according to the steering angle of the steering wheel, is exemplified as one type of axial force. Summary of the Invention

[0004] The relationship between the steering angle, which serves as the basis for the target rotation angle, and the axial force actually acting on the rotation axis varies with vehicle speed. When the vehicle is stationary, the axial force gradient, which is the rate of change of axial force with respect to the steering angle, decreases, and the hysteresis width of the change in axial force with respect to the steering angle increases. On the other hand, when the vehicle is traveling at medium or high speeds, the axial force gradient increases, and the hysteresis width decreases. The hysteresis components can be calculated by adding them together to provide the following hysteresis width, which reflects the actual hysteresis state of the change in axial force with respect to the steering angle, for calculating the angular axial force.

[0005] When the hysteresis width changes more than expected due to the addition of hysteresis components, there is a possibility that the movement of the steering wheel or the sensation obtained from the steering wheel may cause discomfort.

[0006] The problem is not limited to the angular axial force that is calculated as a component of the steering reaction force, but can also arise similarly when the hysteresis components are calculated by summing them to provide a hysteresis width that reflects the actual hysteresis state.

[0007] This invention relates to a steering control device configured to control a steering system in which a steering torque required to steer a steering wheel is changed using motor torque applied from an actuator driven by a motor. The steering control device includes processing circuitry configured to calculate a torque command value, which is a target value of motor torque generated when operation of the motor is controlled to produce motor torque. The processing circuitry is configured to calculate a torque component for calculating the torque command value based on a state variable that changes according to the operation of the steering system. The processing circuitry is configured to calculate a calculated hysteresis component for adding a hysteresis characteristic relative to the change of a specific state variable as the steering system changes to the torque component, the calculated hysteresis component being obtained using the value of the specific state variable set at a specific time as the origin. The processing circuitry includes a first calculation case and a second calculation case, in which a calculated hysteresis component for adding a first hysteresis characteristic to the torque component is calculated, and in the second calculation case, a calculated hysteresis component for adding a second hysteresis characteristic having a hysteresis width greater than that of the first hysteresis characteristic to the torque component is calculated. In the second calculation case following the change from the first calculation case, the processing circuit can calculate the value corresponding to the origin in the second hysteresis characteristic when calculating the calculation hysteresis component that allows the value of the calculation hysteresis component at the moment of change from the first calculation case to be maintained, and can use the calculated value as the origin to calculate the calculation hysteresis component.

[0008] Using this configuration, the computational hysteresis component can be calculated by adjusting the origin used to calculate it, depending on the situation. For example, consider the case of a change from a first calculation state to a second calculation state (i.e., the first calculation state has changed to the second calculation state): when calculating the computational hysteresis component, it is assumed that the hysteresis width changes more than expected before and after the change. At this point, the origin used to calculate the computational hysteresis component is adjusted, given that the first calculation state has changed to the second calculation state. Therefore, even when a specific state variable remains at its value at the moment of change from the first calculation state, sudden changes in the hysteresis width between the pre-change and post-change computational hysteresis components can be suppressed. Thus, by suppressing sudden changes in the hysteresis width in the computational hysteresis component, discomfort caused by steering wheel movement or sensations derived from the steering wheel can be suppressed. Therefore, improved steering feel can be achieved.

[0009] In the steering control device according to this aspect, the processing circuit can be configured to calculate the basic component of the angular axial force as a torque component, the angular axial force being determined based on the angle of rotation of the rotating wheels of the vehicle, and the angular axial force being the axial force in which road surface information is not reflected; and the processing circuit can be configured to calculate the calculation hysteresis component added to the basic component.

[0010] In the steering control device according to this aspect, the processing circuit can be configured to reflect the calculated lag component obtained by calculation in the first calculation case in the torque component in a first state in which the vehicle can be determined to be in a driving state excluding a stopped state; and the processing circuit can be configured to reflect the calculated lag component obtained by calculation in the second calculation case in the torque component in a second state in which the vehicle is determined to be in a driving state including a stopped state.

[0011] Using this configuration, when changing from the first state to the second state (i.e., the first state has changed to the second state), the value of the calculated hysteresis component at the moment of change from the first state is maintained. Therefore, even when changing from the first state to the second state (i.e., the first state has changed to the second state), improved steering feel can be achieved. From the perspective of transmitting the frictional force of the vehicle's rotating wheels to the driver, it is convenient to significantly change the hysteresis width in the second state between the first and second states. That is, when calculating the hysteresis component, it is assumed that the case of a significant change in hysteresis width corresponds to the case of the first state having changed to the second state. Therefore, from the perspective of transmitting the frictional force of the vehicle's rotating wheels to the driver, improved steering feel can be achieved while achieving a convenient mode.

[0012] In the steering control device according to this aspect, when the vehicle speed is determined to be a second vehicle speed corresponding to a second state after a change from a first vehicle speed which was determined to correspond to a first state, the processing circuit can calculate a calculation lag component such that the value of the calculation lag component at the moment of change from the first vehicle speed can be maintained.

[0013] Using this configuration, optimization can be achieved regarding the preservation of the calculated lag component values ​​by using vehicle speed.

[0014] In the steering control device according to this aspect, the processing circuit can be configured to calculate a vehicle speed coefficient according to the change in vehicle speed, such that when the first hysteresis characteristic or the second hysteresis characteristic is added to the torque component, the vehicle speed is reflected in the calculated hysteresis component; and when the calculated vehicle speed coefficient is a second vehicle speed coefficient calculated from a first vehicle speed determined to correspond to a first state and then changed to a second vehicle speed determined to correspond to a second state, the processing circuit can calculate a calculated hysteresis component such that the value of the calculated hysteresis component at the moment of change from the first vehicle speed coefficient can be maintained.

[0015] Using this configuration, optimization can be achieved regarding the preservation of the calculated lag component value by using a vehicle speed coefficient that varies with vehicle speed.

[0016] By utilizing the steering control device according to this aspect of the invention, the deterioration of steering feel can be suppressed. Attached Figure Description

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and in the drawings:

[0018] Figure 1 This is a diagram schematically illustrating the configuration of a steer-by-wire system according to the first embodiment;

[0019] Figure 2 This is a block diagram illustrating the functional configuration of the steering control device according to the first embodiment;

[0020] Figure 3 This is a block diagram showing the functional configuration of the steering force calculation unit according to the first embodiment;

[0021] Figure 4 This is a block diagram showing the functional configuration of the axial force calculation unit according to the first embodiment;

[0022] Figure 5 This is a block diagram illustrating the functional configuration of the axial force calculation unit according to the first embodiment;

[0023] Figure 6 This is a block diagram showing the functional configuration of the driving lag component calculation unit according to the first embodiment;

[0024] Figure 7A It is a graph showing the relationship between the steering angle and the hysteresis component when turning.

[0025] Figure 7B It is a graph showing the relationship between the steering angle and the hysteresis component when turning back;

[0026] Figure 8 It is a graph showing the relationship between vehicle speed and the speed gain of moving vehicles;

[0027] Figure 9 This is a block diagram showing the functional configuration of the angular axial force calculation unit according to the first embodiment;

[0028] Figure 10 It is a graph showing the relationship between the steering angle and the speed gain of the stopped vehicle during a stop;

[0029] Figure 11It is a graph showing the relationship between the steering angle and the stopping hysteresis component when the first vehicle speed has changed to the second vehicle speed;

[0030] Figure 12A It is a graph showing the relationship between steering angle and steering torque during driving;

[0031] Figure 12B It is a graph showing the relationship between steering angle and steering torque during a stop; and

[0032] Figure 13 This is a block diagram illustrating the functional configuration of the angular axis calculation unit according to the second embodiment. Detailed Implementation

[0033] First Implementation Method

[0034] The steering control device according to the first embodiment will now be described with reference to the accompanying drawings. Figure 1 As shown, the vehicle's steering system 2, controlled by the steering control device 1, is configured as a steer-by-wire system. The steering system 2 includes a steering unit 4 steered by the driver using a steering wheel 3 and a rotation unit 6 that rotates the turning wheels 5 according to the steering input from the driver to the steering unit 4.

[0035] The steering unit 4 includes a steering shaft 11 and a steering-side actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering-side actuator 12 includes a steering-side motor 13 serving as a drive source and a steering-side reduction mechanism 14. The steering-side motor 13 applies a steering reaction force as an anti-steering force to the steering wheel 3 via the steering shaft 11. The steering-side motor 13 is connected to the steering shaft 11, for example, via the steering-side reduction mechanism 14 configured as a worm and worm gear. For example, a three-phase brushless motor is used as the steering-side motor 13 according to this embodiment.

[0036] The rotating unit 6 includes a pinion shaft 21, a rack shaft 22 serving as a rotational shaft connected to the pinion shaft 21, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected to each other at a predetermined cross angle. The rack and pinion mechanism 24 is configured to mesh with the pinion teeth 21a formed in the pinion shaft 21 and the rack teeth 22a formed in the rack shaft 22. The rack and pinion mechanism 24 is housed in the rack housing 23. The end opposite to the end of the pinion shaft 21 connected to the rack shaft 22 protrudes from the rack housing 23. The two ends of the rack shaft 22 protrude axially from the corresponding ends of the rack housing 23. A tie rod 26 is connected to the two ends of the rack shaft 22 via rack ends 25, each of which is formed by a ball joint. The distal end of the tie rod 26 is connected to a steering knuckle (not shown) assembled from the right rotating wheel 5 and the left rotating wheel 5.

[0037] The rotating unit 6 includes a rotating-side actuator 31 that applies a rotational force to the rack shaft 22 to rotate the rotating wheel 5. The rotating-side actuator 31 includes a rotating-side motor 32 serving as a drive source, a transmission mechanism 33, and a conversion mechanism 34. The rotating-side motor 32 applies the rotational force to the rack shaft 22 via the transmission mechanism 33 and the conversion mechanism 34 to rotate the rotating wheel 5. The rotating-side motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is configured, for example, as a belt drive mechanism. The transmission mechanism 33 converts the rotational motion of the rotating-side motor 32 into the reciprocating motion of the rack shaft 22 via the conversion mechanism 34, which is configured, for example, as a ball screw mechanism.

[0038] In the steering system 2 with the aforementioned configuration, the rotation angle of the rotating wheel 5 is changed by applying a motor torque, which is a rotational force, from the rotation-side actuator 31 to the rack shaft 22 according to the driver's steering operation. At this time, a steering reaction force against the driver's steering is applied from the steering-side actuator 12 to the steering wheel 3. That is, in the steering system 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is the motor torque applied from the steering-side actuator 12.

[0039] The reason for providing the pinion shaft 21 is that the rack shaft 22 is supported together with the pinion shaft 21 in the rack housing 23. That is, the rack shaft 22 is supported by a support mechanism (not shown) provided in the steering system 2, allowing it to move in its axial direction and being pressed against the pinion shaft 21. Therefore, the rack shaft 22 is supported in the rack housing 23. Alternatively, another support mechanism could be provided to support the rack shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0040] The electrical configuration of steering system 2 will be described below. For example... Figure 1 As shown, the steering-side motor 13 and the rotation-side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of the steering-side motor 13 and the rotation-side motor 32.

[0041] Torque sensor 41, steering side rotation angle sensor 42, rotation side rotation angle sensor 43, and vehicle speed sensor 44 are connected to steering control unit 1. Torque sensor 41 detects steering torque Th, which is a value indicating the torque applied to steering shaft 11 according to the driver's steering operation. Torque sensor 41 is disposed in a portion of steering shaft 11 closer to steering wheel 3 than steering side reduction mechanism 14. Torque sensor 41 detects steering torque Th based on the amount of torsion of torsion bar 41a disposed in a portion of steering shaft 11. For example, when performing a right turn, steering torque Th is detected as a positive value, while when performing a left turn, steering torque Th is calculated as a negative value.

[0042] The steering-side rotation angle sensor 42 detects the rotation angle θa, which is the angle of the rotation axis of the steering-side motor 13, as an angle within a 360-degree range. The steering-side rotation angle sensor 42 is disposed in the steering-side motor 13. The rotation angle θa of the steering-side motor 13 is used to calculate the steering angle θs. The steering-side motor 13 and the steering shaft 11 operate in conjunction with each other via the steering-side reduction mechanism 14. Therefore, there is a correlation between the rotation angle θa of the steering-side motor 13 and the rotation angle of the steering shaft 11, and thus, there is a correlation between the rotation angle θa of the steering-side motor 13 and the steering angle θs, which is the rotation angle of the steering wheel 3. Therefore, the steering angle θs can be calculated based on the rotation angle θa of the steering-side motor 13. For example, when performing a right turn, the rotation angle θa is detected as a positive value, while when performing a left turn, the rotation angle θa is detected as a negative value.

[0043] The rotation angle sensor 43 on the rotation side detects the rotation angle θb, which is the angle of the rotation axis of the rotation side motor 32, as an angle within a 360-degree range. The rotation angle sensor 43 is installed in the rotation side motor 32. The rotation angle θb of the rotation side motor 32 is used to calculate the pinion angle θP. The rotation side motor 32 and the pinion shaft 21 operate in conjunction with each other via the transmission mechanism 33, the conversion mechanism 34, and the rack and pinion mechanism 24. Therefore, there is a correlation between the rotation angle θb of the rotation side motor 32 and the pinion angle θp, which is the rotation angle of the pinion shaft 21. Therefore, the pinion angle θp can be calculated based on the rotation angle θb of the rotation side motor 32. The pinion shaft 21 meshes with the rack shaft 22. Therefore, there is also a correlation between the pinion angle θp and the amount of movement of the rack shaft 22. That is, the pinion angle θp is the value in which the rotation angle of the rotating wheel 5 is reflected. For example, when performing a right turn, the rotation angle θb is detected as a positive value, while when performing a left turn, the rotation angle θb is detected as a negative value.

[0044] Vehicle speed sensor 44 detects vehicle speed V, which is set to indicate the vehicle's travel speed. The function of steering control unit 1 will now be described. Steering control unit 1 includes a central processing unit (CPU) (not shown) and a memory. Steering control unit 1 performs various controls by causing the CPU to execute programs stored in memory at predetermined calculation cycle intervals.

[0045] like Figure 2As shown, the steering control device 1 includes a steering side control unit 50 that controls the power supply to the steering side motor 13. The steering side control unit 50 includes a steering side current sensor 54. The steering side current sensor 54 detects the actual steering side current value Ia obtained from the value of the phase current of the steering side motor 13, which flows in the connection line between the steering side control unit 50 and the phase motor coil of the steering side motor 13. The steering side current sensor 54 obtains the voltage drop as current from the shunt resistor connected to the source side of each switching element in an inverter (not shown) corresponding to the steering side motor 13. Figure 2 For ease of description, one of the connected wirings and one of the phase current sensors are shown together.

[0046] The steering control device 1 includes a rotation-side control unit 60 that controls the power supply to the rotation-side motor 32. The rotation-side control unit 60 includes a rotation-side current sensor 65. The rotation-side current sensor 65 detects the actual rotation-side current value Ib obtained from the value of the phase current of the rotation-side motor 32, which flows in the connection line between the rotation-side control unit 60 and the phase motor coil of the rotation-side motor 32. The rotation-side current sensor 65 obtains the voltage drop as current from the shunt resistor connected to the source side of each switching element in an inverter (not shown) corresponding to the rotation-side motor 32. Figure 2 For ease of description, one of the connected wirings and one of the phase current sensors are shown together.

[0047] The steering side control unit 50 will now be described. Steering torque Th, vehicle speed V, rotation angle θa, actual rotation side current value Ib, pinion angle θp, and target pinion angle θp* (described later) are input to the steering side control unit 50. The steering side control unit 50 controls the power supply to the steering side motor 13 based on the steering torque Th, vehicle speed V, rotation angle θa, actual rotation side current value Ib, pinion angle θp, and target pinion angle θp*.

[0048] The steering-side control unit 50 includes a steering angle calculation unit 51, a target reaction torque calculation unit 52, and a power supply control unit 53. The rotation angle θa is input to the steering angle calculation unit 51. The steering angle calculation unit 51 converts the rotation angle θa into a total angle within a range exceeding 360 degrees, for example, by counting the number of rotations of the steering-side motor 13 starting from the steering neutral point (which is the position of the steering wheel 3 when the vehicle is moving forward in a straight line). The steering angle calculation unit 51 calculates the steering angle θs by multiplying the total angle obtained through conversion by a conversion factor based on the rotational speed ratio of the steering-side reduction gear 14. The obtained steering angle θs is output to the target reaction torque calculation unit 52. The steering angle θs is output to the rotation-side control unit 60, i.e., the steering angle transmission ratio change control unit 62, which will be described later.

[0049] The steering torque Th, vehicle speed V, actual steering side current value Ib, steering angle θs, pinion angle θp, and target pinion angle θp* (described later) are input to the target reaction torque calculation unit 52. The target reaction torque calculation unit 52 calculates the target reaction torque Ts* based on the steering torque Th, vehicle speed V, actual steering side current value Ib, steering angle θs, pinion angle θp, and target pinion angle θp*. The target reaction torque Ts* is a reaction control value that serves as a target value for the steering reaction force of the steering wheel 3 generated by the steering side motor 13. In this embodiment, the target reaction torque Ts* is an example of a torque command value, and the target reaction torque calculation unit 52 is an example of a torque command value calculation unit.

[0050] Specifically, the target reaction torque calculation unit 52 includes a steering force calculation unit 55 and an axial force calculation unit 56. The steering torque Th, steering angle θs, and vehicle speed V are input to the steering force calculation unit 55. The steering force calculation unit 55 calculates the steering force Tb* based on the steering torque Th, steering angle θs, and vehicle speed V. The steering force Tb* acts in the same direction as the driver's steering direction.

[0051] Specifically, such as Figure 3As shown, the steering force calculation unit 55 includes a basic control value calculation unit 71 and a compensation value calculation unit 72. The steering torque Th and vehicle speed V are input to the basic control value calculation unit 71. The basic control value calculation unit 71 calculates a basic control value I1* based on the steering torque Th and vehicle speed V. The basic control value I1* is a control value calculated in association with the steering of the steering wheel 3. The basic control value I1* is a fundamental component of the steering force Tb* and is configured to make the steering of the steering wheel 3 exhibit the desired characteristics. For example, the basic control value calculation unit 71 considers the auxiliary gradient (which is the ratio of the change in the basic control value I1* to the change in the steering torque Th) to calculate the basic control value I1*, such that its absolute value increases with the increase of the absolute value of the steering torque Th and with the decrease of the vehicle speed V. The acquired basic control value I1* is output to the adder 73.

[0052] Steering torque Th, vehicle speed V, and steering angle θs are input to compensation value calculation unit 72. Compensation value calculation unit 72 calculates return compensation value I2*, driving lag compensation value I3*, damping compensation value I4*, and inertia compensation value I5* based on steering torque Th, vehicle speed V, and steering angle θs. In addition to specific compensation values ​​such as compensation values ​​I2* to I5*, various compensation values ​​include a phase delay compensation value for compensating the phase of steering torque Th, causing that phase to be delayed, and a phase advance compensation value for compensating the phase of basic control value I1*, causing that phase to be advanced. The phase delay compensation value and phase advance compensation value are not shown. The phase delay compensation value is used to adjust the auxiliary gradient. The phase advance compensation value is used to stabilize the system by suppressing resonance characteristics. These various compensation values ​​are compensation values ​​used to perform compensation so that the operation of the steering wheel 3 based on the basic control value I1* exhibits the desired characteristics.

[0053] The compensation value calculation unit 72 includes a return compensation value calculation unit 81, a driving lag compensation value calculation unit 82, a damping compensation value calculation unit 83, and an inertia compensation value calculation unit 84.

[0054] The steering torque Th, vehicle speed V, steering angle θs, and steering rate ωs obtained by differentiating the steering angle θs using the differentiator 85 are input to the return compensation value calculation unit 81. The return compensation value calculation unit 81 calculates the return compensation value I2* based on the steering torque Th, vehicle speed V, steering angle θs, and steering rate ωs. The return compensation value I2* is used to compensate for the return operation of the steering wheel 3, returning the steering wheel 3 to the steering neutral point. The self-aligning torque of the rotating wheel 5 is associated with the return operation of the steering wheel 3, and excess or insufficient self-aligning torque is compensated by the return compensation value I2*. The return compensation value I2* is used to generate torque in the direction in which the steering wheel 3 returns to the steering neutral point. The obtained return compensation value I2* is output to the adder 73.

[0055] Vehicle speed V and steering angle θs are input to the driving lag compensation value calculation unit 82. The driving lag compensation value calculation unit 82 calculates a driving lag compensation value I3* based on vehicle speed V and steering angle θs. The driving lag compensation value I3* is used to perform compensation, thereby optimizing the lag characteristics caused by the friction force during steering wheel 3 operation. The mechanical friction component of the vehicle equipped with steering system 2 is associated with the lag characteristics caused by the friction force during steering wheel 3 operation, and compensation is performed using the driving lag compensation value I3* to optimize the lag characteristics caused by the mechanical friction component. In this embodiment, the driving lag compensation value I3* is used to perform compensation, thereby optimizing the lag characteristics caused by the friction force during steering wheel 3 operation, particularly in the vehicle's driving state excluding a stationary state. The vehicle's driving state excluding a stationary state is, for example, a state where the vehicle is traveling at a medium or high speed equal to or greater than 10 km / h. The driving lag compensation value I3* has a lag characteristic relative to changes in steering angle θs. The obtained driving lag compensation value I3* is output to adder 73.

[0056] Vehicle speed V and steering speed ωs are input to damping compensation value calculation unit 83. Damping compensation value calculation unit 83 calculates a damping compensation value I4* based on vehicle speed V and steering speed ωs. The damping compensation value I4* is used to perform compensation, thereby reducing the minute vibrations generated in steering wheel 3. The viscosity component of steering system 2 (specifically, the viscosity component of the steering-side actuator 31) is associated with the reduction of minute vibrations generated in steering wheel 3, and compensation is performed using damping compensation value I4* to reduce the minute vibrations generated in steering wheel 3. The damping compensation value I4* is used to generate torque in the direction opposite to the direction in which the steering speed ωs is generated at this time. The acquired damping compensation value I4* is output to adder 73.

[0057] The vehicle speed V and the steering acceleration αs obtained from the differentiator 86 by differentiating the steering speed ωs are input to the inertia compensation value calculation unit 84. The inertia compensation value calculation unit 84 calculates the inertia compensation value I5* based on the vehicle speed V and the steering acceleration αs. The inertia compensation value I5* is used to perform compensation, thereby suppressing the caught feeling at the start of steering of the steering wheel 3 and the overshoot feeling at the end of steering. The inertial component of the steering system 2 is associated with suppressing the caught feeling at the start of steering of the steering wheel 3 and the overshoot feeling at the end of steering, and compensation is performed using the inertia compensation value I5* to suppress the caught feeling at the start of steering and the overshoot feeling at the end of steering. The inertia compensation value I5* is used to generate torque in the direction in which the steering acceleration αs is generated when the absolute value of the steering acceleration αs increases (e.g., at the start of steering of the steering wheel 3). The inertia compensation value I5* is used to generate torque in the direction opposite to the direction in which the steering acceleration αs decreases (e.g., at the end of steering of the steering wheel 3). The acquired inertia compensation value I5* is output to adder 73.

[0058] Adder 73 calculates the steering force Tb* by adding the compensation values ​​I2* to I5* to the basic control value I1*. In addition to the compensation values ​​I2* to I5*, phase delay compensation values, phase advance compensation values, etc., are added to and reflected in the basic control value I1*. For example... Figure 2 As shown, the acquired steering force Tb* is output to subtractor 57. The steering force Tb* acts in the same direction as the driver's steering direction. The steering force Tb* is calculated as a value with the dimension of torque (N·m).

[0059] like Figure 2 As shown, the vehicle speed V, steering angle θs, actual current value Ib on the rotating side, pinion angle θp, and target pinion angle θp* (described later) are input to the axial force calculation unit 56. The axial force calculation unit 56 calculates the axial force F applied to the rack shaft 22 via the rotating wheel 5 based on the vehicle speed V, steering angle θs, actual current value Ib on the rotating side, pinion angle θp, and target pinion angle θp*. The axial force F is calculated as a value with the dimension of torque (N·m). The axial force F acts in the direction opposite to the driver's steering direction. The subtractor 57 calculates the target reaction torque Ts* by subtracting the axial force F from the steering force Tb*. The obtained target reaction torque Ts* is output to the power supply control unit 53.

[0060] The target reaction torque Ts*, the rotation angle θa, and the actual steering side current value Ia are input to the power supply control unit 53. The power supply control unit 53 calculates the current command value Ia* for the steering side motor 13 based on the target reaction torque Ts*. The power supply control unit 53 calculates the difference between the current command value Ia* and the current value in the dq coordinate system obtained by converting the actual steering side current value Ia based on the rotation angle θa, and controls the power supply to the steering side motor 13 to eliminate the difference. The steering side motor 13 generates torque corresponding to the target reaction torque Ts*. Therefore, an appropriate responsiveness can be provided to the driver.

[0061] The rotation side control unit 60 will now be described. Steering angle θs, vehicle speed V, and rotation angle θb are input to the rotation side control unit 60. The rotation side control unit 60 controls the power supply to the rotation side motor 32 based on the steering angle θs, vehicle speed V, and rotation angle θb.

[0062] The rotating side control unit 60 includes a pinion angle calculation unit 61, a steering angle transmission ratio change control unit 62, and a pinion angle feedback control unit. Figure 2 The “pinion angle F / B control unit” 63 and the power supply control unit 64 are included.

[0063] The rotation angle θb is input to the pinion angle calculation unit 61. The pinion angle calculation unit 61 converts the rotation angle θb into a total angle within a range exceeding 360 degrees by counting the number of rotations of the rotation-side motor 32 starting from the rack center point (which is the position of the rack shaft 22 when the vehicle is traveling forward in a straight line). The pinion angle calculation unit 61 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, by multiplying the total angle obtained through conversion by a conversion factor based on the rotational speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotational speed ratio of the pinion mechanism 24. For example, when the pinion angle θp is to the right of the rack center point, the pinion angle θp is calculated as a positive value, and when the pinion angle θp is to the left of the rack center point, the pinion angle θp is calculated as a negative value. The obtained pinion angle θp is output to the pinion angle feedback control unit 63. The pinion angle θp is output to the steering side control unit 50, namely the axial force calculation unit 56 of the target reaction torque calculation unit 52.

[0064] Vehicle speed V and steering angle θs are input to steering angle transmission ratio change control unit 62. Steering angle transmission ratio change control unit 62 calculates the target pinion angle θp* by adding an adjustment amount to the steering angle θs. Steering angle transmission ratio change control unit 62 changes the adjustment amount based on vehicle speed V to change the steering angle transmission ratio, which is the ratio of the target pinion angle θp* to the steering angle θs. For example, the adjustment amount is changed such that when vehicle speed V is low, the change in target pinion angle θp* relative to steering angle θs is greater than the change in target pinion angle θp* relative to steering angle θs when vehicle speed V is high. There is a correlation between steering angle θs and target pinion angle θp*. The pinion angle θp is controlled based on the target pinion angle θp*. Therefore, there is also a correlation between steering angle θs and pinion angle θp.

[0065] The target pinion angle θp* and the pinion angle θp are input to the pinion angle feedback control unit 63. The pinion angle feedback control unit 63 uses proportional, integral, and derivative terms to perform PID control as feedback control of the pinion angle θp, ensuring that the pinion angle θp matches the target pinion angle θp*. That is, the pinion angle feedback control unit 63 calculates the difference between the target pinion angle θp* and the pinion angle θp, and calculates the rotational force command value T*, which serves as the target control value for the rotational force, thus eliminating the difference.

[0066] The rotation force command value T*, the rotation angle θb, and the actual rotation side current value Ib are input to the power supply control unit 64. The power supply control unit 64 calculates the current command value Ib* for the rotation side motor 32 based on the rotation force command value T*. The power supply control unit 64 calculates the difference between the current command value Ib* and the current value in the dq coordinate system obtained by converting the actual rotation side current value Ib based on the rotation angle θb, and controls the power supply to the rotation side motor 32 to eliminate the difference. Therefore, the rotation side motor 32 rotates by the angle corresponding to the rotation force command value T*.

[0067] The function of the axial force calculation unit 56 will be described in detail below. Figure 4 As shown, the axial force calculation unit 56 includes an axial force distribution calculation unit 91, an end axial force calculation unit 92, a differential axial force calculation unit 93, and an axial force selection unit 94.

[0068] The axial force calculation unit 91 calculates the distributed axial force FD based on the axial force acting on the rack shaft 22. The distributed axial force Fd corresponds to the calculated axial force, which is obtained by summing the angular axial force Fr and the current axial force Fi (described later) in their respective distribution ratios so that the axial force acting on the rack shaft 22 via the rotating wheel 5 is appropriately reflected. The obtained distributed axial force Fd is output to the adder 95. In this embodiment, the distributed axial force Fd is an example of a torque component.

[0069] The end axial force calculation unit 92 calculates the end axial force Fie to transmit to the driver the situation where the steering limit of the steering wheel 3, i.e., the steering limit of the turning wheel 5, has been reached. The end axial force Fie corresponds to the force that resists the steering of the steering wheel 3, such that when the absolute value of the steering angle θs approaches the steering angle limit, it restricts the steering wheel 3 from additional steering to the side exceeding the steering angle limit corresponding to the steering limit.

[0070] The target pinion angle θp* is input to the end axial force calculation unit 92. The end axial force calculation unit 92 calculates the end axial force Fie based on the target pinion angle θp*. Specifically, the end axial force calculation unit 92 includes an end axial force mapping that defines the relationship between the target pinion angle θp* and the end axial force Fie, and uses the mapping and the target pinion angle θp* as input to calculate the end axial force Fie. When the absolute value of the target pinion angle θp* is equal to or less than the threshold angle θie, the end axial force calculation unit 92 calculates the end axial force Fie as "0". When the absolute value of the target pinion angle θp* is greater than the threshold angle θie, the end axial force calculation unit 92 determines that the steering angle θs exceeds the steering angle limit, and calculates the end axial force Fie such that its absolute value is greater than "0". The end axial force Fie is set such that when the absolute value of the target pinion angle θp* increases to a large value exceeding the threshold angle θie, the absolute value of the end axial force Fie becomes so large that additional steering of the steering wheel 3 is impossible to perform by hand. The acquired end axial force Fie is output to the axial force selection unit 94.

[0071] The differential axial force calculation unit 93 calculates the differential axial force Fv to transmit this change to the driver when the relationship between the steering state of the steering wheel 3 and the rotation state of the rotating wheel 5 changes based on the steering angle transmission ratio. An example of a change in the relationship between the steering state of the steering wheel 3 and the rotation state of the rotating wheel 5 is when the rotating wheel 5 contacts an obstacle such as a curb. In this case, the rotating wheel 5 cannot turn towards the side where the obstacle is located, but there is a possibility that the steering wheel 3 will turn beyond the side corresponding to the stop position of the steering wheel 3. This is because the power transmission path between the steering unit 4 and the rotation unit 6 is interrupted. Another example of a change in the relationship between the steering state of the steering wheel 3 and the steering state of the rotating wheel 5 is when the operation of the rotating-side motor 32 is restricted to prevent overheating, and therefore the correlation between the steering angle θs and the rotation angle collapses. This is because the pinion angle θp is unlikely to coincide with the target pinion angle θp*. The differential axial force Fv corresponds to the force opposing the steering of the steering wheel 3, thus limiting the additional steering of the steering wheel 3 when the rotating wheel 5 contacts an obstacle such as a curb. The differential axial force Fv corresponds to the force that opposes the steering of the steering wheel 3, so that when the operation of the rotating side motor 32 is restricted to prevent overheating, the steering of the steering wheel 3 is restricted to ensure the consistency (follow-up) of the pinion angle θp with the target pinion angle θp*.

[0072] The steering angle θs, pinion angle θp, and actual current value Ib on the rotating side are input to the differential axial force calculation unit 93. The differential axial force calculation unit 93 calculates the converted angle by adding an adjustment amount to the pinion angle θp. The converted angle is obtained by converting the pinion angle θp according to the steering angle transmission ratio, where the pinion angle θp is represented as an index value of the rotation angle, thus being represented as an index value of the steering angle. The differential axial force calculation unit 93 changes the adjustment amount according to the vehicle speed V, changing the calculation rule defined by the steering angle transmission ratio change control unit 62 to a calculation rule where the relationship between input and output is reversed. The differential axial force calculation unit 93 calculates the differential axial force Fv based on the difference obtained by subtracting the converted angle from the steering angle θs. Specifically, the differential axial force calculation unit 93 includes a differential axial force mapping that defines the relationship between the absolute value of the difference and the differential axial force Fv, and uses the mapping and the difference as input to calculate the differential axial force Fv. The differential axial force calculation unit 93 sets the sign of the differential axial force Fv based on the actual current value Ib on the rotating side. That is, the differential axial force calculation unit 93 sets the differential axial force Fv to positive when the actual current value Ib on the rotating side is positive, including zero, and sets the differential axial force Fv to negative when the actual current value Ib on the rotating side is negative. The obtained differential axial force Fv is output to the axial force selection unit 94.

[0073] The end axial force Fie and the differential axial force Fv are input to the axial force selection unit 94. The axial force selection unit 94 selects the axial force with the larger absolute value from the end axial force Fie and the differential axial force Fv, and calculates the selected axial force as the selected axial force Fsl. The adder 95 calculates the axial force F by adding the selected axial force Fsl to the allocated axial force Fd. Figure 2 As shown, the acquired axial force F is output to subtractor 57. Subtractor 57 calculates the target reaction torque Ts* by subtracting the axial force F from the steering force Tb*. The acquired target reaction torque Ts* is output to the power supply control unit 53.

[0074] The function of the axial force calculation unit 91 will be described below. Figure 5 As shown, the axial force distribution calculation unit 91 includes an angular axial force calculation unit 101, a current axial force calculation unit 102, and an axial force distribution ratio calculation unit 103.

[0075] The target pinion angle θp*, steering angle θs, and vehicle speed V are input to the angular axial force calculation unit 101. The angular axial force calculation unit 101 calculates the angular axial force Fr based on the target pinion angle θp*, steering angle θs, and vehicle speed V. The angular axial force Fr is an ideal value of the axial force defined by a model arbitrarily set for the vehicle. The angular axial force Fr is calculated as an axial force in which road surface information is not reflected. Road surface information includes, for example, minor bumps or irregularities that do not affect the vehicle's lateral behavior, or stepped sections that do affect the vehicle's lateral behavior. For example, the angular axial force calculation unit 101 calculates the angular axial force Fr such that its absolute value increases with the absolute value of the target pinion angle θp*. The angular axial force calculation unit 101 calculates the angular axial force Fr such that its absolute value increases with the vehicle speed V. The angular axial force Fr is calculated as a value with the dimension of torque (N·m). The acquired angular axial force Fr is output to the multiplier 104. In this embodiment, the angular axial force Fr is an example of a torque component, and the angular axial force calculation unit 101 is an example of a torque component calculation unit.

[0076] The actual current value Ib on the rotating side is input to the current axial force calculation unit 102. The current axial force calculation unit 102 calculates the current axial force Fi based on the actual current value Ib on the rotating side. The current axial force Fi is an estimate of the axial force actually acting on the rack shaft 22 that rotates the rotating wheel 5 (i.e., the axial force actually transmitted to the rack shaft 22). The current axial force Fi is calculated as the axial force in which road surface information is reflected. For example, the current axial force calculation unit 102 calculates the current axial force Fi based on the assumption that the torque applied to the rack shaft 22 by the rotating side motor 32 is balanced with the torque corresponding to the force applied to the rack shaft 22 via the rotating wheel 5. That is, the current axial force calculation unit 102 calculates the current axial force Fi such that its absolute value increases with the increase of the absolute value of the actual current value Ib on the rotating side. The current axial force Fi is calculated as a value with the dimension of torque (N·m). The acquired current axial force Fi is output to the multiplier 105.

[0077] The vehicle speed V is input to the axial force distribution ratio calculation unit 103. The axial force distribution ratio calculation unit 103 calculates the axial force distribution gain Di based on the vehicle speed V. The axial force distribution gain Di is the distribution ratio of the current axial force Fi when the angular axial force Fr and the current axial force Fi are added in a distribution ratio to obtain the distributed axial force Fd. The axial force distribution ratio calculation unit 103 includes an axial force distribution gain map that defines the relationship between the vehicle speed V and the axial force distribution gain Di, and uses this map and the vehicle speed V as input to calculate the axial force distribution gain Di. Multiplier 105 multiplies the current axial force Fi by the obtained axial force distribution gain Di, and outputs the result as the final current axial force Fim to adder 108. Subtractor 106 calculates the axial force distribution gain Dr by subtracting the axial force distribution gain Di from the "1" stored in storage unit 107. The obtained axial force distribution gain Dr is output to multiplier 104. The axial force distribution gain Dr is the distribution ratio of the angular axial force Fr when the distributed axial force Fd is acquired. That is, the axial force distribution gain Dr is calculated such that its sum with the axial force distribution gain Di is "1 (100%)". The distribution ratio includes the concept of a zero value where only one of the angular axial force Fr and the current axial force Fi is allocated (provided) to the distributed axial force Fd. Storage unit 107 is a predetermined storage area of ​​a memory (not shown).

[0078] Multiplier 104 multiplies the angular axial force Fr obtained from angular axial force calculation unit 101 by the obtained axial force distribution gain Dr, and outputs the result as the final angular axial force Frm to adder 108. Adder 108 calculates the distributed axial force Fd by adding the angular axial force Frm to the current axial force Fim (i.e., by summing the angular axial force Frm and the current axial force Fim). The distributed axial force Fd acts in the direction opposite to the driver's steering direction. The distributed axial force Fd is calculated as a value with the dimension of torque (N·m). Figure 4 As shown, the acquired axial force Fd is output to adder 95.

[0079] The following will describe the driving lag compensation value calculation unit 82. For example... Figure 6 As shown, the driving lag compensation value calculation unit 82 includes a driving zero point calculation unit 111, a driving lag component calculation unit 112, and a driving vehicle speed gain calculation unit 113.

[0080] The steering angle θs is input to the driving zero-point calculation unit 111. The driving zero-point calculation unit 111 calculates the driving zero-point Pr based on the steering angle θs, which is used when the driving lag component calculation unit 112 calculates the driving lag component Fhy1, which will be described later. Specifically, when the start of a turn-around steering or a return steering is determined, the driving zero-point calculation unit 111 calculates the steering angle θs at the starting position as the driving zero-point Pr. The driving zero-point calculation unit 111 determines the start of a turn-around steering or a return steering based on the increase and / or decrease of the steering angle θs, i.e., the sign of the steering speed ωs obtained by differentiating the steering angle θs. That is, the driving zero-point calculation unit 111 updates the driving zero-point Pr each time the start of a turn-around steering or a return steering is determined.

[0081] In this embodiment, a turning steering is a steering in which the steering direction remains the same. A returning steering is a steering in which the steering angle θs remains within a predetermined small range after the steering direction has changed. For example, the driving zero-point calculation unit 111 determines the start of turning steering when the steering angle θs begins to change from a state where the steering angle θs has not changed, that is, when the steering speed ωs changes from a zero value to a positive or negative value. The driving zero-point calculation unit 111 determines the start of returning steering when the steering angle θs begins to change between increasing and decreasing during turning steering, that is, when the sign of the steering speed ωs begins to change between a positive and a negative value. The driving zero-point calculation unit 111 determines the start of turning steering when the steering angle θs has changed by an angle corresponding to a predetermined range after the start of returning steering has been determined.

[0082] The obtained zero-point driving speed Pr is output to the driving lag component calculation unit 112. The steering angle θs and the zero-point driving speed Pr are input to the driving lag component calculation unit 112. The driving lag component calculation unit 112 calculates the driving lag component Fhy1 based on the steering angle θs and the zero-point driving speed Pr. The driving lag component Fhy1 is the component that is added to the basic control value I1* to make the steering force Tb* have lag characteristics.

[0083] like Figure 7A and Figure 7B As shown, the driving lag component calculation unit 112 includes lag maps MA1 and MA2, which define the relationship between the steering angle θs and the driving lag component Fhy1. The driving lag component calculation unit 112 calculates the driving lag component Fhy1 using one of the lag maps MA1 and MA2, based on whether the currently executed steering is a turn steering or a return steering, determined in the same manner as in the driving zero-point calculation unit 111. In the lag maps MA1 and MA2, "θs" represents the change in the steering angle θs, that is, the angular deviation θhs when the steering angle θs is at the beginning position of the turn steering or return steering; that is, setting the driving zero point Pr to the origin.

[0084] Specifically, the driving lag component calculation unit 112 uses the lag mapping MA1 to calculate the driving lag component Fhy1 when turning the steering wheel. In this case, the driving lag component Fhy1 is calculated such that its absolute value increases, and the absolute value of the lag gradient decreases as the absolute value of the angular deviation θhs increases. The absolute value of the lag gradient is the rate of change of the driving lag component Fhy1 relative to the angular deviation θhs. In this case, the absolute value of the driving lag component Fhy1 saturates within a range where the angular deviation θhs is equal to or greater than a predetermined value, and the absolute value is calculated such that the maximum value of this value is equal to or less than the maximum value Fmax.

[0085] When performing a right turn, if the driving zero point Pr at the start of the turn is used as the origin of the hysteresis mapping MA1, the driving hysteresis component calculation unit 112 uses the value appearing in the first quadrant. When performing a left turn, if the driving zero point Pr at the start of the turn is used as the origin of the hysteresis mapping MA1, the driving hysteresis component calculation unit 112 uses the value appearing in the third quadrant.

[0086] On the other hand, the driving lag component calculation unit 112 calculates the driving lag component Fhy1 using the lag mapping MA2 during the return turn. In this case, the driving lag component Fhy1 is calculated as proportional to the angular deviation θhs. The driving lag component Fhy1 in this case is only calculated when the angular deviation θhs is within a predetermined range from the driving zero point Pr.

[0087] When performing a rightward return turn, and using the driving zero point Pr at the start position of the return turn as the origin of the hysteresis map MA2, the driving hysteresis component calculation unit 112 uses the value appearing in the first quadrant only when the angular deviation θhs is within a predetermined range from the origin. When performing a leftward return turn, and using the driving zero point Pr at the start position of the return turn as the origin of the hysteresis map MA2, the driving hysteresis component calculation unit 112 uses the value appearing in the third quadrant only when the angular deviation θhs is within a predetermined range from the origin.

[0088] In this embodiment, hysteresis maps MA1 and MA2 are configured to change the driving hysteresis component Fhy1 according to the vehicle speed V. Hysteresis maps MA1 and MA2 change the driving hysteresis component Fhy1 according to the vehicle speed V to achieve a desired steering feel. In this embodiment, for example, the driving hysteresis component Fhy1 is changed such that the hysteresis gradient increases as the vehicle speed V decreases. Hysteresis maps MA1 and MA2 change the driving hysteresis component Fhy1 such that the maximum value Fmax increases as the vehicle speed V increases. For example, in the case where the vehicle speed V is a very low speed, such as less than 6 km / h, including a stationary driving state, the maximum value Fmax is set to a large value, up to 10 times the maximum value Fmax in the case where the vehicle speed is a medium or high speed, such as equal to or greater than 10 km / h, excluding a stationary driving state. The driving hysteresis component Fhy1 can vary according to the steering speed ωs, which is the derivative of the steering angle θs. In this case, for example, the driving hysteresis component Fhy1 can be changed so that the hysteresis gradient decreases as the steering speed ωs increases.

[0089] Therefore, when performing a sinusoidal steering maneuver in which the steering wheel 3 is periodically and repeatedly rotated and returned at a constant frequency, the driving lag component calculation unit 112 calculates the driving lag component Fhyl, thus providing a lag characteristic relative to the change in steering angle θs. The obtained driving lag component Fhy1 is output to the multiplier 114.

[0090] The vehicle speed V is input to the vehicle speed gain calculation unit 113. The vehicle speed gain calculation unit 113 calculates the vehicle speed gain Dv1 based on the vehicle speed V. For example... Figure 8As shown, the vehicle speed gain calculation unit 113 includes a vehicle speed gain mapping M11 that defines the relationship between vehicle speed V and vehicle speed gain Dv1, and uses this mapping and vehicle speed V as input to calculate vehicle speed gain Dv1. For example, when vehicle speed V is extremely low, i.e., when vehicle speed V is less than a first threshold V1, the vehicle speed gain calculation unit 113 calculates vehicle speed gain Dv1 as "zero (0%)". For example, when vehicle speed V is medium or high, i.e., when vehicle speed V is equal to or higher than a second threshold V2, the vehicle speed gain calculation unit 113 calculates vehicle speed gain Dv1 as "1 (100%)". For example, when vehicle speed V is low, between extremely low and medium or high speed, i.e., when vehicle speed V is equal to or higher than the first threshold V1 and equal to or less than the second threshold V2, the vehicle speed gain calculation unit 113 calculates vehicle speed gain Dv1 such that "zero" and "1" are linearly connected. In this embodiment, a vehicle speed V less than a first threshold V1 corresponds to a second vehicle speed determined to correspond to a second state, and a vehicle speed V equal to or higher than the first threshold, that is, equal to or higher than a second threshold V2, which corresponds to a first vehicle speed determined to correspond to a first state.

[0091] The vehicle speed gain Dvl is obtained by multiplying the driving lag component Fhyl, and the result is output as the driving lag compensation value I3* obtained from multiplier 114 to adder 73. The angular axial force calculation unit 101 will be described below.

[0092] like Figure 9 As shown, the axial force calculation unit 101 includes an axial force basic component calculation unit 121, an extremely low speed determination unit 122, a stop zero point calculation unit 123, a stop lag component calculation unit 124, a stop vehicle speed gain calculation unit 125, and a zero point inverse calculation unit 126.

[0093] The target pinion angle θp* is input to the axial force fundamental component calculation unit 121. The axial force fundamental component calculation unit 121 calculates the axial force fundamental component Frb based on the target pinion angle θp*. The axial force fundamental component Frb is the fundamental component of the angular axial force Fr. Specifically, the axial force fundamental component calculation unit 121 calculates the axial force fundamental component Frb such that its absolute value increases with the absolute value of the target pinion angle θp*. The axial force fundamental component Frb is calculated as a value with a torque (N·m) dimension. The obtained axial force fundamental component Frb is output to adder 127.

[0094] The vehicle speed V is input to the ultra-low speed determination unit 122. When it is detected that the vehicle speed V, which is above a first threshold V1, has become below the first threshold V1 (i.e., the vehicle speed V has become below the first threshold V1 via the first threshold V1), the ultra-low speed determination unit 122 generates a determination flag FLG indicating that the change has been detected. In this embodiment, the case where the vehicle speed V, which is above the first threshold V1, has become below the first threshold V1 corresponds to the case where the vehicle speed V is detected to change from a first vehicle speed to a second vehicle speed. The obtained determination flag FLG is output to the stop zero-point calculation unit 123.

[0095] The steering angle θs, the determination flag FLG, and the correction zero point Pc (described later) are input to the stop zero point calculation unit 123. The stop zero point calculation unit 123 calculates the stop zero point Ps used in the stop hysteresis component calculation unit 124 when calculating the stop hysteresis component Fhy2, based on the steering angle θs. When the start of a turn or the start of a return turn is determined, the stop zero point calculation unit 123 calculates the steering angle θs at the starting position as the stop zero point Ps in the same manner as the driving zero point calculation unit 111 calculates the driving zero point Pr.

[0096] When no determination flag FLG is input, the stop zero-point calculation unit 123 calculates the stop zero-point Ps obtained through calculation, which is taken as the final stop zero-point Ps. That is, when no determination flag FLG is input, the stop zero-point calculation unit 123 updates the stop zero-point Ps each time the starting point of the determined rotation direction or the starting point of the return direction is determined.

[0097] On the other hand, when the determination flag FLG is input, the stop zero-point calculation unit 123 calculates the stop zero-point Ps obtained by correcting the calculated stop zero-point Ps to a correction zero-point Pc as the final stop zero-point Ps. The correction zero-point Pc is obtained by the zero-point inverse calculation unit 126. That is, when the determination flag FLG is input, the stop zero-point calculation unit 123 does not determine the start of the rotation direction or the start of the return direction, and updates the stop zero-point Ps so that it becomes the correction zero-point Pc obtained by the zero-point inverse calculation unit 126. The calculation of the correction zero-point Pc will be described in detail later. The obtained final stop zero-point Ps is output to the stop hysteresis component calculation unit 124.

[0098] The steering angle θs, the stop zero point Ps, and the vehicle speed V are input to the stop hysteresis component calculation unit 124. The stop hysteresis component calculation unit 124 calculates the stop hysteresis component Fhy2, which is added to the axial force base component Frb, as a component that gives the angular axial force Fr a hysteresis characteristic, based on the steering angle θs, the stop zero point Ps, and the vehicle speed V.

[0099] like Figure 7A and Figure 7BAs shown, the stop lag component calculation unit 124 includes lag maps MB1 and MB2, which define the relationship between the steering angle θs and the stop lag component Fhy2. The lag maps MB1 and MB2 have essentially the same configuration as the lag maps MA1 and MA2 included in the driving lag component calculation unit 112.

[0100] The stop lag component calculation unit 124 calculates the stop lag component Fhy2 in the same manner as the driving lag component calculation unit 112 calculates the driving lag component Fhy1. That is, when performing a right turn, if the stop zero point Ps at the start position of the turn is used as the origin of the lag mapping MB1, the stop lag component calculation unit 124 uses the value appearing in the first quadrant. When performing a left turn, if the stop zero point Ps at the start position of the turn is used as the origin of the lag mapping MB1, the stop lag component calculation unit 124 uses the value appearing in the third quadrant. In the case of performing a right return turn, if the stop zero point Ps at the start position of the return turn is used as the origin of the lag mapping MB2, the stop lag component calculation unit 124 uses the value appearing in the first quadrant only when the angular deviation θhs is within a predetermined range from the origin. In the case of performing a leftward return turn, where the stop zero point Ps at the start position of the return turn is used as the origin of the hysteresis map MB2, the stop hysteresis component calculation unit 124 uses the value appearing in the third quadrant only when the angular deviation θhs is within a predetermined range from the origin.

[0101] Therefore, when performing a sinusoidal steering maneuver in which the steering wheel 3 is periodically and repeatedly rotated and returned at a constant frequency, the stop hysteresis component calculation unit 124 calculates the stop hysteresis component Fhy2, thus providing a hysteresis characteristic relative to the change in steering angle θs. The obtained stop hysteresis component Fhy2 is output to the multiplier 128 and the zero-point inverse calculation unit 126.

[0102] In this embodiment, the characteristic indicated by the stopping hysteresis component Fhy2 calculated when the vehicle speed V is at a medium or high speed is an example of a first hysteresis characteristic. That is, the case where the stopping hysteresis component Fhy2 is calculated when the vehicle speed V is at a medium or high speed is an example of a first calculation case. The characteristic indicated by the stopping hysteresis component Fhy2 calculated when the vehicle speed V is at a very low speed is an example of a second hysteresis characteristic. That is, the case where the stopping hysteresis component Fhy2 is calculated when the vehicle speed V is at a very low speed is an example of a second calculation case.

[0103] The vehicle speed V is input to the stopped vehicle speed gain calculation unit 125. The stopped vehicle speed gain calculation unit 125 calculates the stopped vehicle speed gain Dv2 based on the vehicle speed V. For example... Figure 10As shown, the stopped vehicle speed gain calculation unit 125 includes a vehicle speed gain mapping M12 that defines the relationship between vehicle speed V and stopped vehicle speed gain Dv2, and calculates the stopped vehicle speed gain Dv2 using this mapping and vehicle speed V as input. For example, when vehicle speed V is low, medium, or high speed, i.e., when vehicle speed V is equal to or higher than a first threshold V1, the stopped vehicle speed gain calculation unit 125 calculates the stopped vehicle speed gain Dv2 as "zero (0%)". For example, when vehicle speed V is zero, the stopped vehicle speed gain calculation unit 125 calculates the stopped vehicle speed gain Dv2 as "1 (100%)". For example, when vehicle speed V is extremely low speed, i.e., when vehicle speed V is less than the first threshold V1, the stopped vehicle speed gain calculation unit 125 calculates the stopped vehicle speed gain Dv2 such that the "zero point" and the value "1" are linearly connected.

[0104] When the vehicle speed V increases from zero to medium or high speed, i.e., to the second threshold V2, the stopping vehicle speed gain calculation unit 125 limits the rate of change of the stopping vehicle speed gain Dv2 in each calculation cycle to a predetermined limit value. When the rate of change of the stopping vehicle speed gain Dv2 in each calculation cycle is greater than the limit value, the stopping vehicle speed gain calculation unit 125 limits the rate of change of the stopping vehicle speed gain Dv2 in each calculation cycle to the limit value. Therefore, when the vehicle speed V increases from zero to medium or high speed, i.e., to the second threshold V2, the stopping vehicle speed gain calculation unit 125 changes the stopping vehicle speed gain Dv2 more slowly compared to the previous cycle (one cycle ago). That is, the stopping vehicle speed gain calculation unit 125 has the function of compensating for the stopping vehicle speed gain Dv2, so that sudden changes in the stopping vehicle speed gain Dv2 are suppressed when the vehicle speed V increases from zero to medium or high speed, i.e., to the second threshold V2. In this embodiment, as Figure 10 As shown by the alternating long and two short dashed lines, for example, the limit value changes such that it increases with the increase of vehicle speed V. From the viewpoint of realizing a change in the stiffness of the rotating wheel 5 when the vehicle speed V increases from zero to medium or high speed, that is, to the second threshold V2, the limit value is set through experiments, simulations, etc.

[0105] The stopping hysteresis component Fhy2 is multiplied by multiplier 128 to obtain the stopping vehicle speed gain Dv2, and the result is input as the angular axial force hysteresis component Fhyr to adder 127. Adder 127 calculates the angular axial force Fr by adding the angular axial force hysteresis component Fhyr to the axial force base component Frb, and outputs the obtained angular axial force Fr to multiplier 104.

[0106] In the present embodiment, the stop vehicle speed gain Dv2 is an example of a vehicle speed coefficient, and the stop vehicle speed gain calculation unit 125 is an example of a coefficient calculation unit. The stop vehicle speed gain Dv2 calculated when the vehicle speed V is less than the first threshold V1 corresponds to a second vehicle speed coefficient, and the stop vehicle speed gain Dv2 calculated when the vehicle speed V is equal to or higher than the first threshold V1 corresponds to a first vehicle speed coefficient.

[0107] In the present embodiment, the running hysteresis compensation value I3* is used to perform compensation so that the hysteresis characteristics caused by the frictional force when operating the steering wheel 3 are optimized particularly in the running state of the vehicle excluding the stop state. The running state of the vehicle excluding the stop state is a state in which the vehicle travels at a medium speed or a high speed, for example, at a vehicle speed equal to or higher than 10 km / h. The running hysteresis compensation value I3* has a hysteresis characteristic with respect to the change in the steering angle θs. The obtained running hysteresis compensation value I3* is output to the adder 73.

[0108] As Figure 9 shown, the stop hysteresis component Fhy2 and the steering angle θs are input to the zero-point inverse calculation unit 126. The zero-point inverse calculation unit 126 calculates the correction zero point Pc based on the stop hysteresis component Fhy2 and the steering angle θs. The zero-point inverse calculation unit 126 includes hysteresis maps MB1 (V < V1) and MB2 (V < V1) in a case where the vehicle speed V is particularly extremely low, where the hysteresis maps MB1 and MB2 are included in the stop hysteresis component calculation unit 124. When determining the start of turning the steering or the start of returning the steering, the zero-point inverse calculation unit 126 calculates the steering angle θs at the start position as the stop zero point Ps in the same manner as the stop zero point calculation unit 123 calculates the stop zero point Ps. In this case, the zero-point inverse calculation unit 126 calculates the change in the steering angle θs, that is, the angular deviation θhs with the stop zero point Ps as the origin, based on the steering angle θs.

[0109] The zero-point inverse calculation unit 126 calculates the angular deviation θhs corresponding to the origin in the hysteresis maps MB1 (V < V1) and MB2 (V < V1) when calculating the stop hysteresis component Fhy2 having the same value as the input stop hysteresis component Fhy2. In this case, when performing a right turning steering, the zero-point inverse calculation unit 126 uses the value appearing in the first quadrant of the hysteresis map MB1 (V < V1). When performing a left turning steering, the zero-point inverse calculation unit 126 uses the value appearing in the third quadrant of the hysteresis map MB1 (V < V1). When performing a right return steering, the zero-point inverse calculation unit 126 uses the value appearing in the first quadrant of the hysteresis map MB2 (V < V1). When performing a left return steering, the zero-point inverse calculation unit 126 uses the value appearing in the third quadrant of the hysteresis map MB2 (V < V1).

[0110] For example, as shown in Figure 11 , on the premise of performing a turning steering to the right, assume that in a coordinate system where the horizontal axis represents the angular deviation θhs and the vertical axis represents the stop hysteresis component Fhy2, the point indicating the input [stop hysteresis component Fhy2, angular deviation θhs] is located at coordinate P1. Here, the value indicated by the one long and two short alternating dash-dot lines in the first quadrant of the hysteresis map MB1 (V < V1) is completely shifted to the right, that is, to the side where the angular deviation hs increases in the positive direction, until the position where the hysteresis map MB1 (V < V1) overlaps with the coordinate P1 at this position. In the shifted hysteresis map MB1 (V < V1), as indicated by the solid line in Figure 11 , the value of the steering angle θs corresponding to the value of the angular deviation θhs on the horizontal axis is the correction zero point Pc. In this case, the correction zero point Pc is obtained as a value obtained by subtracting the value of the angular deviation θhs on the horizontal axis from the steering angle θs corresponding to the stop zero point Ps. Using the angular deviation θhs obtained by updating the origin to the correction zero point Pc, the same value as the value of the stop hysteresis component Fhy2 input to the zero inverse calculation unit 126 at this time is obtained as the stop hysteresis component Fhy2 calculated using the hysteresis map MB1 (V < V1). On the premise of performing a turning steering to the left, the same applies to the values appearing in the third quadrant of the hysteresis map MB1 (V < V1), and the values appearing in the third quadrant are shifted to the left, that is, to the side where the angular deviation θhs increases in the negative direction. When performing a return steering to the right, the same applies to the values appearing in the first quadrant of the hysteresis map MB (V < V1), and the values appearing in the first quadrant are shifted to the right, that is, to the side where the angular deviation θhs increases in the positive direction. When performing a return steering to the left, the same applies to the values appearing in the third quadrant of the hysteresis map MB2 (V < V1), and the values appearing in the third quadrant are shifted to the left, that is, to the side where the angular deviation θhs increases in the negative direction.The obtained correction zero point Pc is output to the stop zero point calculation unit 123. In the present embodiment, the very low speed determination unit 122, the stop zero point calculation unit 123, the stop hysteresis component calculation unit 124, the stop vehicle speed gain calculation unit 125, the zero inverse calculation unit 126, and the multiplier 128 are examples of the hysteresis component calculation unit.

[0111] ​​The operations in the first embodiment will be described below. In this embodiment, according to whether the vehicle speed V is an extremely low speed, the stop hysteresis component Fhy2 can be calculated by correcting the origins of the hysteresis maps MB1 and MB2. For example, when calculating the stop hysteresis component Fhy2, the case where the vehicle speed V is detected to change from a medium speed or a low speed via a low speed to an extremely low speed is a case where it is assumed that the hysteresis width changes greatly before and after changing to the extremely low speed. This is because the maximum value Fmax of the stop hysteresis component Fhy2 in the hysteresis map MB1 (V < V1) used after changing to the extremely low speed is set to be greater than the maximum value Fmax in the hysteresis map MB1 (V ≥ V1, V2) used before changing to the extremely low speed. The same applies to the hysteresis map MB2 (V ≥ V1, V2) and the hysteresis map MB2 (V < V1, V2).

[0112] In this embodiment, the stop zero calculation unit 123 can use the determination flag FLG to determine whether the vehicle speed V changes from a medium speed or a high speed via a low speed to an extremely low speed. When the determination flag FLG is input, the stop zero calculation unit 123 updates the obtained stop zero Ps to the corrected zero Pc obtained by the zero inverse calculation unit 126.

[0113] For example, assume Figure 11 The situation shown represents the instant when the vehicle speed V changes from a medium speed or a high speed via a low speed to an extremely low speed on the premise of performing a rightward turning steering. At this instant, when the angular deviation θhs has the first deviation value θhs1, the stop hysteresis component Fhy2 corresponding to the first component value Fhy21 at the coordinate P1 is calculated based on the hysteresis map MB1 (V ≥ V1, V2).

[0114] Subsequently, immediately after the vehicle speed V has changed to an extremely low speed, Figure 11 The hysteresis map MBl (V < Vl) indicated by the one long and two short alternate dash lines in is used to calculate the stop hysteresis component Fhy2. When neither the start of a turning steering nor the start of a return steering is performed immediately after the vehicle speed V changes to an extremely low speed, the stop zero Ps ([[]] Figure 11 "Ps1" in ) at the instant when the vehicle speed V has changed from a medium speed or a high speed via a low speed to an extremely low speed is maintained. In this case, when the angular deviation θhs is maintained at the first deviation value θhs1 immediately after the vehicle speed V has changed to an extremely low speed, the stop hysteresis component Fhy2 having the second component value Fhy22 corresponding to the coordinate P2 is calculated based on the hysteresis map MB1 (V < V1). An example of the case where the angular deviation θhs is maintained at the first deviation value θhs1 is the hands-free state where the driver does not hold the steering wheel 3. That is, immediately after the vehicle speed V changes to an extremely low speed, because the one indicated by Figure 11The hysteresis mapping MB1 (V < V1) indicated by the one long and two short alternating dash-dotted lines in [ ] causes the possibility that the hysteresis width of the stop hysteresis component Fhy2 will suddenly change.

[0115] On the other hand, in the present embodiment, as shown by the arrow in [ ], even when the start of turning the steering wheel or the start of returning the steering wheel is not performed immediately after the vehicle speed V has changed to an extremely low speed, the stop zero point Ps is updated to the correction zero point Pc under the condition that the vehicle speed V has changed to an extremely low speed. Therefore, as shown by the arrow in [ ], the stop zero point Ps is updated from "Ps1" to the correction zero point Pc ( Figure 11 "Ps2" in [ ]). In this case, even if the angular deviation θhs is maintained at the first deviation value θhs1, the stop hysteresis component Fhy2 having the first component value Fhy21 corresponding to the coordinate P1 is calculated based on the hysteresis mapping MB1 (V < V1) indicated by the solid line in [ ]. Figure 11 Figure 11 Figure 11

[0116]

[0117] Figure 12A Therefore, when the vehicle speed V has changed from medium speed or high speed via low speed to extremely low speed, a sudden change in the hysteresis width between the stop hysteresis component Fhy2 before the change and the stop hysteresis component Fhy2 after the change can be suppressed. Figure 12B

[0118]

[0119]

[0120]

[0121] It is assumed that the characteristics shown in [ ] represent the driving steering characteristics indicated by the relationship between the steering angle θs and the steering torque Th when performing the sinusoidal steering of the steering wheel 3 in a state where the vehicle speed V is low speed, medium speed, or high speed. On the other hand, it is assumed that the characteristics shown in [ ] represent the stop steering characteristics indicated by the relationship between the steering angle θs and the steering torque Th when performing the sinusoidal steering of the steering wheel 3 in a state where the vehicle speed V is extremely low speed.

[0122] [[ID=​​(1-2) According to this embodiment, when the vehicle speed V has changed from medium or high speed to very low speed via low speed, the value of the stopping lag component Fhy2 at the moment of its change can be maintained. Therefore, even when the vehicle speed V has changed from medium or high speed to very low speed via low speed, steering feel can be improved. From the viewpoint of transmitting the friction force of the rotating wheel 5 to the driver, the lag width can be easily and significantly changed between the low, medium, or high speed driving states and the very low speed driving state. That is, the case where the lag width changes significantly when calculating the stopping lag component Fhy2 corresponds to the case where the vehicle speed V has changed from medium or high speed to very low speed via low speed. Therefore, from the viewpoint of transmitting the friction force of the rotating wheel 5 to the driver, steering feel can be improved while achieving a convenient mode.

[0121] (1-3) According to this embodiment, by using the vehicle speed V, it is possible to optimize the value of the stopping hysteresis component Fhy2.

[0122] Second Implementation Method

[0123] The steering control device according to the second embodiment will now be described with reference to the accompanying drawings. The differences from the first embodiment will be described primarily herein. Elements identical to those in the first embodiment will be indicated by the same reference numerals and will not be described again.

[0124] The axial force calculation unit 101 will be described. For example... Figure 13 As shown, the angular axial force calculation unit 101 has a configuration in which the extremely low speed determination unit 122 is omitted from the configuration described above in the first embodiment. In the angular axial force calculation unit 101, the stop zero point calculation unit 123 and the zero point inverse calculation unit 126 according to the first embodiment are modified to omit the extremely low speed determination unit 122.

[0125] Specifically, the steering angle θs and the correction zero point Pc are input to the stop zero point calculation unit 123a corresponding to the stop zero point calculation unit 123 according to the first embodiment. The stop zero point calculation unit 123a calculates the stop zero point Ps in the same manner as the stop zero point calculation unit 123 according to the first embodiment. When the correction zero point Pc is not input, the stop zero point calculation unit 123a calculates the stop zero point Ps obtained by calculation as the final stop zero point Ps. On the other hand, when the correction zero point Pc is input, the stop zero point calculation unit 123a calculates the stop zero point Ps obtained by correcting the stop zero point Ps obtained by calculation to the correction zero point Pc as the final stop zero point PS.

[0126] The stop hysteresis component Fhy2, the steering angle θs, and the stopping vehicle speed gain Dv2 are input to the zero-point inverse calculation unit 126a corresponding to the zero-point inverse calculation unit 126 according to the first embodiment. When no change in the value of the stopping vehicle speed gain Dv2 from "zero" is detected, i.e., an increase, in other words, the value does not change, or when a decrease in the value of the stopping vehicle speed gain Dv2 from "1" to "zero" is detected, the zero-point inverse calculation unit 126a neither calculates nor outputs the correction zero point Pc. On the other hand, when a change in the value of the stopping vehicle speed gain Dv2 is detected, i.e., an increase from "zero", the zero-point inverse calculation unit 126a calculates the correction zero point Pc and outputs it to a stop zero-point calculation unit 123a similar to the zero-point inverse calculation unit 126 according to the first embodiment. That is, when the value of the stopped vehicle speed gain Dv2 is detected to increase from "zero", the zero-point inverse calculation unit 126a is uncertain about the start of the turning steering or the start of the return steering and calculates and outputs the correction zero point Pc so that the stop zero point Ps is updated by the stop zero point calculation unit 123a.

[0127] According to this embodiment, in addition to the operation and advantages of the first embodiment, the following advantages can also be achieved. (2-1) According to this embodiment, by using the parking vehicle speed gain Dv2, optimization can be achieved regarding the value of the parking lag component Fhy2.

[0128] The aforementioned implementation can be modified as follows. Unless there is a technical conflict, the following modification examples can be combined. In the first implementation, the function of the extremely low speed determination unit 122 can be implemented as the function of the stop zero-point calculation unit 123. That is, the vehicle speed V can be input to the stop zero-point calculation unit 123. Alternatively, the function of the extremely low speed determination unit 122 can be implemented as the function of the zero-point inverse calculation unit 126. In this case, the vehicle speed V can be input to the zero-point inverse calculation unit 126. Similar to the second implementation, the correction zero point Pc can be input to the stop zero-point calculation unit 123 only when necessary. In this case, the function of the extremely low speed determination unit 122 can be omitted.

[0129] In the second embodiment, the function of the zero-point inverse calculation unit 126a in detecting the increase of the value of the stopped vehicle speed gain Dv2 from "zero" can be implemented as the function of the stop zero-point calculation unit 123a. That is, the vehicle speed V can be input to the stop zero-point calculation unit 123a. In this case, the zero-point inverse calculation unit 126a can be basically configured to calculate and output the correction zero point Pc. When the value of the stopped vehicle speed gain Dv2 is detected to increase from "zero", the stop zero-point calculation unit 123a can reflect the correction based on the input correction zero point Pc. In addition, a calculation unit having the function of the zero-point inverse calculation unit 126a that detects the increase of the value of the stopped vehicle speed gain Dv2 from "zero" can be added to the angular axial force calculation unit 101.

[0130] In the first embodiment, the angular axial force hysteresis component Fhyr can be input to the zero-point inverse calculation unit 126. In this case, the stopping vehicle speed gain Dv2 can be input to the zero-point inverse calculation unit 126, and the stopping vehicle speed gain Dv2 can be used to calculate the correction zero point Pc. Regarding the correction zero point Pc, the zero-point inverse calculation unit 126 can calculate the angular deviation θhs corresponding to the origin when calculating the angular axial force hysteresis component Fhyr, which has the same value as the input angular axial force hysteresis component Fhyr. In this case, regarding the correction zero point Pc, the zero-point inverse calculation unit 126 can calculate the angular deviation θhs corresponding to the origin when calculating the stopping hysteresis component Fhy2, which has the same value as the input angular axial force hysteresis component Fhyr. This also applies to the second embodiment.

[0131] In the foregoing embodiments, the component using the target pinion angle θp* can calculate various components based on state variables that are correlated with the target pinion angle θp*, rather than the target pinion angle θp* itself. Examples of state variables correlated with the target pinion angle θp* include the pinion angle θp, steering angle θs, rotation angle θa, and rotation angle θb, and these are examples of state variables that vary according to the operation of the steering system 2. The target pinion angle θp*, or an angle correlated with the target pinion angle θp*, is an angle that can be converted into the rotation angle of the rotating wheel 5. That is, for example, the axial force base component Frb or the end axial force Fie can be calculated based on the pinion angle θp. According to this modified example, the same advantages as in the foregoing embodiments can be achieved. This also applies to state variables correlated with the target pinion angle θp*, such as the steering angle θs or the pinion angle θp. That is, for example, the driving lag component Fhy1 or the stopping lag component Fhy2 can be calculated based on the pinion angle θp or the target pinion angle θp*, rather than the steering angle θs.

[0132] In the foregoing embodiments, as long as at least one state variable associated with the operation of the steering wheel 3 is used to calculate the steering force Tb*, the steering force calculation unit 55 may not use the vehicle speed V and may use a combination with another element. As the state variable associated with the operation of the steering wheel 3, the steering angle θs may be used, or other elements may be used instead of the steering torque Th described in the foregoing embodiments.

[0133] In the aforementioned embodiment, as long as at least the target pinion angle θp* is used to calculate the axial force basic component Frb, the axial force basic component calculation unit 121 can combine other elements such as vehicle speed V.

[0134] In the aforementioned embodiment, as long as at least the steering angle θs is used to calculate the driving lag component Fhy1, the driving lag component calculation unit 112 may not use the vehicle speed V. In this case, the driving vehicle speed gain Dv1 can be used to adjust the magnitude of the maximum value Fmax of the vehicle speed V based on lag maps MA1 and MA2, etc. This also applies to the case where the stopping lag component calculation unit 124 calculates the stopping lag component Fhy2. In this case, the stopping vehicle speed gain Dv2 can be used to adjust the magnitude of the maximum value Fmax of the vehicle speed V based on lag maps MB1 and MB2, etc.

[0135] In the aforementioned embodiment, the driving lag component calculation unit 112 can use another element in combination with the steering angle θs or the vehicle speed V to calculate the driving lag component Fhy1. This also applies to the case where the stopping lag component calculation unit 124 calculates the stopping lag component Fhy2.

[0136] In the aforementioned embodiment, the axial force distribution ratio calculation unit 103 can be combined with another element as long as the vehicle speed V is used to calculate the axial force distribution gain Di. In the aforementioned embodiment, the end axial force calculation unit 92 and the differential axial force calculation unit 93 can be removed from the axial force calculation unit 56. In this case, the axial force selection unit 94 and the adder 95 can be removed. The distributed axial force Fd calculated by the distributed axial force calculation unit 91 is output to the subtractor 57.

[0137] In the aforementioned embodiments, as long as the vehicle speed V is used to calculate the speed gain Dv1 of a moving vehicle, the moving vehicle speed gain calculation unit 113 can combine with another element. This also applies to the case where the stationary vehicle speed gain calculation unit 125 calculates the speed gain Dv2 of a stationary vehicle.

[0138] In the aforementioned embodiment, the stopping vehicle speed gain calculation unit 125 can gradually change the stopping vehicle speed gain Dv2 over time, and take into account the steering state of the steering unit 4, such as the steering angle θs, or the rotation state of the rotation unit 6, such as the pinion angle θp, during the gradual change.

[0139] In the aforementioned embodiments, another case can be considered as maintaining the value of the stopping hysteresis component Fhy2. An example of such a case is where the rotation of the rotating wheel 5 is locked while the vehicle is moving. In the case where the rotation of the rotating wheel 5 is locked while the vehicle is moving, there is a possibility that the vehicle speed V will reach an extremely low speed. This can be estimated, for example, based on the separation between the vehicle speed V and state variables such as the yaw rate generated in the vehicle. Another example of such a case is where the road on which the vehicle is traveling changes from a high-μ road to a low-μ road.

[0140] In the foregoing embodiments, the target to which the hysteresis components are added is not limited to the angular axial force Fr. As the target to which the hysteresis components are added, a component such as the axial force, obtained by considering at least one of the yaw rate and lateral acceleration, can be appropriately used, as long as it is a component with hysteresis characteristics and thus facilitates the operation of the steering system 2. In this case, even if the same problem as in the foregoing embodiments occurs, this problem can be solved by adopting a configuration based on the embodiment.

[0141] In the aforementioned embodiments, the value of the vehicle speed V, which is defined as extremely low speed, i.e., the first threshold V1, can be appropriately modified, as long as it includes a stationary state. For example, the first threshold V1 can be set to a small value, such as 3 km / h, or it can be set to a large value, such as 10 km / h, which is considered a low speed.

[0142] In the aforementioned embodiments, the steering control device 1 can reflect the command values ​​for the autonomous driving system used to implement various driving support functions or autonomous driving functions during the operation of the steering system 2. In this case, even if the same problem occurs as in the aforementioned embodiments, this problem can be solved by adopting a configuration based on the implementation method.

[0143] In the foregoing embodiments, the steering side control unit 50 can be configured to function as the steering side control unit 60. In the foregoing embodiments, the steering side motor 32 can be configured, for example, coaxially with the rack shaft 22, or connected via a worm gear to the pinion shaft, which together with the rack shaft 22 forms a rack and pinion mechanism.

[0144] In the foregoing embodiments, the steering control device 1 may be configured to include (1) one or more processors operating according to a computer program (software), (2) one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs) executing at least some of various processes, or (3) a combination of such processing circuits. The processor includes a CPU and memories such as RAM and ROM, and the memories store program code or commands configured to cause the CPU to perform processing. The memories, i.e., non-transitory computer-readable media, include all available media accessible by a general-purpose or special-purpose computer.

[0145] In the foregoing embodiments, the steering system 2 employs a disconnected structure in which the steering unit 4 and the rotation unit 6 are typically mechanically disconnected from each other. However, the invention is not limited to this, and the steering system can also employ a structure in which the steering unit 4 and the rotation unit 6 can be mechanically disconnected via a clutch. The steering system 2 can be an electric power steering system that applies an auxiliary force, which is a force used to assist the driver's steering operation. In this case, the steering wheel 3 is mechanically connected to the pinion shaft 21 via the steering shaft 11. The component corresponding to the angular axial force hysteresis component Fhyr in the foregoing embodiments can be reflected in the auxiliary force. In this case, even if the same problem as in the foregoing embodiments occurs, this problem can be solved by adopting a configuration based on the embodiment.

Claims

1. A steering control device configured to control a steering system (2) in which a steering torque required to steer a steering wheel (3) is changed using a motor torque applied from an actuator driven by a motor, the steering control device being characterized by comprising: A processing circuit configured to calculate a torque command value, the torque command value being a target value of the motor torque when the operation of the motor is controlled to generate the motor torque. The processing circuit is configured to calculate the torque component used to calculate the torque command value based on state variables that change according to the operation of the steering system (2). The processing circuit is configured to calculate a calculated hysteresis component, which is used to add the hysteresis characteristic relative to the change of a specific state variable as the steering system (2) changes to the torque component. The calculated hysteresis component is obtained using the value of the specific state variable set at a predetermined time as the origin. The processing circuit includes a first calculation state and a second calculation state. In the first calculation state, a calculated hysteresis component is calculated to add the first hysteresis characteristic to the torque component. In the second calculation state, a calculated hysteresis component is calculated to add the second hysteresis characteristic, which has a hysteresis width greater than that of the first hysteresis characteristic, to the torque component. In the second calculation scenario following a change from the first calculation scenario, when the processing circuit calculates a calculation lag component that preserves the value of the calculation lag component at the moment of change from the first calculation scenario, it calculates a value corresponding to the origin in the second lag characteristic and uses the calculated value as the origin to calculate the calculation lag component. The processing circuit is configured to: in a first state in which the vehicle can be determined to be in a driving state excluding a stopped state, reflect the computational lag component obtained through calculation in the first computational case in the torque component; and The processing circuit is configured to, in a second state in which the vehicle can be determined to be in a driving state including the stopped state, reflect the computational lag component obtained by calculation in the second computational case in the torque component.

2. The steering control device according to claim 1, characterized in that, The processing circuit is configured to calculate the fundamental component of the angular axial force as the torque component, the angular axial force being determined based on an angle that can be converted into the rotation angle of the vehicle's rotating wheels, and the angular axial force being an axial force in which road surface information is not reflected; and The processing circuit is configured to calculate the computational lag component that is added to the basic component.

3. The steering control device according to claim 1 or 2, characterized in that, When the vehicle speed is determined to be a second vehicle speed corresponding to the second state after a change from a first vehicle speed determined to correspond to the first state, the processing circuit calculates a computational lag component such that the value of the computational lag component at the moment of change from the first vehicle speed can be maintained.

4. The steering control device according to claim 1 or 2, characterized in that, The processing circuit is configured to calculate a vehicle speed coefficient based on changes in vehicle speed, such that when the first hysteresis characteristic or the second hysteresis characteristic is added to the torque component, the vehicle speed is reflected in the calculated hysteresis component. and In the case where the calculated vehicle speed coefficient is a second vehicle speed coefficient calculated from a first vehicle speed determined to correspond to the first state and then to a second vehicle speed determined to correspond to the second state, the processing circuit calculates a calculation lag component such that the value of the calculation lag component at the moment of change from the first vehicle speed coefficient is maintained.

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