Steering Controller

Abstract

A steering controller (2) includes a torque command value calculator (62) configured to calculate a torque command value that serves as a target value of motor torque. The torque command value calculator (62) has a hysteresis component calculator (92) configured to calculate a hysteresis component that is added so that a command value component has a hysteresis characteristic and changes accordingly with a change in a state quantity that changes according to an operation of a steering device (1). The hysteresis component calculator (92) is configured to calculate the hysteresis component by adding a hysteresis differential component and a hysteresis basic component.

Description

Technical Field

[0001] The present invention relates to a steering controller. Background Art

[0002] Description of Related Art

[0003] A vehicle steering device includes an electric power steering (EPS) device that uses a motor to apply an assisting force for assisting a driver in performing steering. The vehicle steering device also includes a steering unit that is steered by the driver and a turning device that turns a turning wheel in accordance with the steering performed by the driver. In a steer-by-wire (SBW) steering device, a steering-side motor provided in the steering unit applies a steering reaction force that resists the driver's steering, and the steering-side motor provided in the steering unit applies a turning force to turn the steering wheel.

[0004] A steering controller that controls a steering device such as a control target improves the steering feel by calculating a command value of motor torque applied to the steering device by an electric motor based on various components. For example, the steering controller disclosed in Japanese Patent Application Laid-Open No. 2016-144974 calculates a torque command value based on a value obtained by subtracting a hysteresis component corresponding to a turning or returning steering state from a basic component of an assisting force based on steering torque. The steering controller changes the hysteresis component based on the spring characteristics of the vehicle on which the steering device is mounted to adjust and optimize the steering feel. Summary of the Invention

[0005] Incidentally, in recent years, there has been an increasing demand for improving the steering feel of a steering device. In fact, even with the above configuration, it cannot be said that the steering feel meets the required level. Therefore, it is desired to create new technology that can achieve a better steering feel.

[0006] The present invention provides a steering controller capable of improving the steering feel.

[0007] A steering controller according to an aspect of the present invention is configured to control a steering device configured to vary a steering torque for steering a steering wheel by using a motor torque applied by an actuator using a motor as a drive source. The steering controller includes a torque command value calculator configured to calculate a torque command value serving as a target value of the motor torque. The steering controller controls the operation of the motor to generate a motor torque corresponding to the torque command value. The torque command value calculator has a command value component calculator configured to calculate a command value component added for calculating the torque command value, and a hysteresis component calculator configured to calculate a hysteresis component added so that the command value component has a hysteresis characteristic and changes correspondingly with a change in a state quantity, the change in the state quantity changing according to the operation of the steering device. The hysteresis component calculator has a hysteresis basic component calculator configured to calculate a hysteresis basic component as a basic component of the hysteresis component based on the state quantity, the hysteresis basic component changing such that as the state quantity becomes larger, the absolute value of the hysteresis basic component becomes larger and the absolute value of a hysteresis gradient, which is a change amount with respect to the change in the state quantity, becomes smaller; and a hysteresis differential component calculator configured to calculate a hysteresis differential component, which is a component obtained by differentiating the hysteresis basic component. The hysteresis component calculator is configured to calculate the hysteresis component by adding the hysteresis differential component to the hysteresis basic component.

[0008] Here, by adding the hysteresis basic component, it is possible to give the driver a response to steering. In order to give the driver a significant response as a response to steering, it can be considered to increase the hysteresis gradient, which is the gradient at the rising edge of the hysteresis basic component, and thus enhance the responsiveness. In this case, when the hysteresis gradient is forcibly increased and thus the responsiveness is overly enhanced, due to reasons such as insufficient response performance, the characteristic of the vibration response in the hysteresis basic component becomes significant, which is disadvantageous in terms of stability. In other words, there are limitations to increasing the hysteresis gradient of the hysteresis basic component and enhancing the responsiveness for the purpose of giving the driver a significant response.

[0009] To address these limitations, in the above configuration, the hysteresis differential component functions to suppress the characteristic of the vibration response generated in the hysteresis basic component. This means that when the hysteresis gradient of the hysteresis basic component increases, the characteristic of the vibration response can be suppressed. Therefore, compared with the case where the hysteresis differential component is not added, the limitation of the responsiveness enhanced by increasing the hysteresis gradient of the hysteresis basic component can be expanded. Therefore, compared with the case where the hysteresis differential component is not added, a hysteresis basic component with a larger hysteresis gradient and enhanced responsiveness can be designed. Therefore, a significant response can be given to the driver, and an improvement in the steering feel can be achieved.

[0010] In the above aspect, the hysteresis basic component calculator may be configured to change the hysteresis basic component based on a change amount of an angle of a rotation axis that rotates in relation to the steering of the steering wheel.

[0011] According to the above configuration, for example, when changing the hysteresis basic component such that the hysteresis gradient becomes smaller and the responsiveness becomes lower, as the change amount of the angle of the rotation axis that rotates in relation to the steering of the steering wheel is larger, the driver can smoothly perform a steering operation with a steering response suppressed in the case of rapid steering. Therefore, a significant response can be given to the driver, or the driver can perform a smooth steering operation, and thus an appropriate steering feeling corresponding to the steering state of the steering wheel can be set. Therefore, the above configuration is effective for achieving an improvement in the steering feeling.

[0012] In the above aspect, the hysteresis basic component calculator may be configured to change the hysteresis basic component based on the vehicle speed. According to this configuration, for example, when changing the hysteresis basic component such that the hysteresis gradient becomes larger and the responsiveness is enhanced, as the vehicle speed becomes smaller, sufficient response can be given to the driver when the vehicle stops. Therefore, a significant response can be given to the driver, or sufficient response can be given to the driver, and thus an appropriate steering feeling corresponding to the driving state of the vehicle can be set. Therefore, the above configuration is effective for achieving an improvement in the steering feeling.

[0013] Here, when the hysteresis basic component is changed based on the vehicle speed, the hysteresis differential component (a component obtained by differentiating the hysteresis basic component) also changes based on the vehicle speed in the natural course of events. However, the hysteresis differential component that changes based on the vehicle speed in the natural course of events is not necessarily suitable for the purpose of improving the steering feeling.

[0014] Therefore, in the above configuration, the hysteresis differential component calculator may be configured to change the hysteresis differential component based on the vehicle speed. According to this configuration, in the case where the hysteresis basic component changes based on the vehicle speed, the hysteresis differential component added to the hysteresis basic component can be calculated as an appropriate component for improving the steering feeling. Therefore, the above configuration can contribute to the improvement of the steering feeling.

[0015] The steering controller according to the above aspect can achieve an improvement in the steering feeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and in which:

[0017] Figure 1 is a schematic block diagram of a steering device;

[0018] Figure 2 is a block diagram showing the functions of a steering controller;

[0019] Figure 3 is a block diagram showing the functions of a target reaction force torque calculator according to a first embodiment.

[0020] Figure 4 is a block diagram showing the functions of a hysteresis component calculator according to a first embodiment;

[0021] Figure 5A is a graph showing the relationship between the rotation angle and the basic hysteresis component during turning.

[0022] Figure 5B is a graph showing the relationship between the rotation angle and the basic hysteresis component during reverse steering.

[0023] <00> Figure 6 is a graph showing the relationship between the rotation angle and the basic hysteresis component in the case of sinusoidal steering;

[0024] Figure 7 is a graph showing the relationship between the rotation angle and the target steering torque;

[0025] Figure 8 is a diagram showing Figure 5A an enlarged view of the relationship in which the first quadrant of

[0026] Figure 9 is a diagram showing Figure 7 an enlarged view of the relationship in which the first quadrant of

[0027] Figure 10 is a block diagram showing the functions of a target reaction force torque calculator according to a second embodiment; and

[0028] Figure 11 is a block diagram showing the functions of an angular axial force calculator according to a third embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] First Embodiment

[0030] Hereinafter, a first embodiment in which a steering controller is applied to a steer-by-wire system will be described with reference to the drawings.

[0031] As Figure 1As shown, the steering device 1 of this embodiment is a steer-by-wire device. The steering device 1 includes a steering controller 2 that controls the operation of the steering device 1. The steering device 1 includes a steering mechanism 4 that is steered by a driver via a steering wheel 3, and a rotation mechanism 6 that rotates a rotating wheel 5 according to the steering of the steering mechanism 4 by the driver. The steering device 1 of this embodiment has a structure that always mechanically separates the power transmission path between the steering mechanism 4 and the rotation mechanism 6.

[0032] The steering mechanism 4 includes a steering shaft 11 coupled to the steering wheel 3, and a steering-side actuator 12 that applies a steering reaction force that resists steering to the steering wheel 3 via the steering shaft 11.

[0033] The steering-side actuator 12 includes a steering-side electric motor 13 that serves as a drive source and a speed reducer 14 formed by a worm and a worm wheel. The steering-side motor 13 is coupled to the steering shaft 11 via the speed reducer 14.

[0034] The rotation mechanism 6 includes a pinion shaft 21, a rack shaft 22, a rack housing 23, and a rack and pinion mechanism 24. The rack shaft 22 serves as a rotating shaft coupled to the pinion shaft 21. The rack housing 23 accommodates the rack shaft 22 so as to be reciprocally movable in the axial direction. The rack and pinion mechanism 24 is formed by the pinion shaft 21 and the rack shaft 22. The rack shaft 22 and the pinion shaft 21 are arranged in the rack housing 23 at a prescribed crossing angle. The rack and pinion mechanism 24 is configured by the meshing of pinion teeth 21a formed on the pinion shaft 21 and rack teeth 22a formed on the rack shaft 22. Both ends of the rack shaft 22 are coupled to a tie rod 26 via a rack end 25 formed by a ball-and-socket joint. An end of the tie rod 26 is coupled to a steering knuckle (not shown) attached to the rotating wheel 5.

[0035] The pinion shaft 21 is provided to support the rack shaft 22 within the rack housing 23. Specifically, the rack shaft 22 is pressed against the pinion shaft 21, while the pinion shaft 21 is axially movably supported by a support mechanism (not shown) provided in the rotation mechanism 6. Thus, the rack shaft 22 is supported within the rack housing 23. The rotation of the rack shaft 22 is also restricted. Instead of the pinion shaft 21, another support mechanism that supports the rack shaft 22 may be provided in the rack housing 23. In this case, a rotation mechanism 6 without the pinion shaft 21 configured may be employed.

[0036] The rotation mechanism 6 includes a rotation-side actuator 31. The rotation-side actuator 31 applies power to the rack shaft 22 to axially move the rack shaft 22, thereby rotating the rotation wheel 5. The rotation-side actuator 31 includes a steering-side motor 32 serving as a drive source, a belt mechanism 33, and a ball screw mechanism 34. The rotation-side actuator 31 transmits the rotation of the rotation-side motor 32 to the ball screw mechanism 34 through the belt mechanism 33. In the ball screw mechanism 34, the rotation-side actuator 31 converts the rotation of the rotation-side motor 32 into a reciprocating axial motion of the rack shaft 22 to apply power to the rack shaft 22.

[0037] In the steering device 1 constructed in this way, according to the steering performed by the driver, motor torque is applied to the rack shaft 22 as power from the rotation-side actuator 31. Therefore, the steering angle of the rotation wheel 5 is changed. At this time, the rotation-side actuator 12 applies a steering reaction force against the steering performed by the driver to the steering wheel 3. In short, in the steering device 1, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, and the steering reaction force is the motor torque applied from the rotation-side actuator 12.

[0038] As Figure 1 shown, the steering-side motor 13 and the rotation-side motor 32 are connected to the steering controller 2 that controls the driving of the motors 13 and 32. The steering controller 2 controls the driving of the motors 13 and 32 by controlling the supply amount of current as a control variable of the motors 13 and 32 based on the detection results of various sensors. Examples of various sensors include a vehicle speed sensor 41, a torque sensor 42, a steering-side rotation angle sensor 43, and a rotation-side rotation angle sensor 44.

[0039] The vehicle speed sensor 41 detects a vehicle speed value V, which is a value indicating the vehicle speed as the traveling speed of the vehicle. The torque sensor 42 detects a steering torque Th, which is a value indicating the torque applied to the steering shaft 11 due to the steering performed by the driver. The steering-side rotation angle sensor 43 detects a steering-side rotation angle θs within a range of 360°, and the steering-side rotation angle θs is the angle of the rotation axis of the steering-side motor 13. The rotation-side rotation angle sensor 44 detects a rotation-side rotation angle θt as the angle of the rotation axis of the rotation-side motor 32 within a range of 360°. For example, the steering torque Th, the steering-side rotation angle θs, and the rotation-side rotation angle θt are detected as positive values when the vehicle steers to the right, and are detected as negative values when the vehicle steers to the left.

[0040] Now, a description of the functions of the steering controller 2 will be given. The steering controller 2 includes a central processing unit (CPU) and a memory (not shown). The CPU executes the program stored in the memory at each prescribed operation cycle. Therefore, various processes are executed.

[0041] Figure 2 Some of the processes executed by the steering controller 2 are shown. Figure 2 The processes shown are some of the processes implemented by the CPU executing a program stored in the memory. The processes are shown for each type implemented.

[0042] The steering controller 2 includes: a steering-side control unit 51 that outputs a steering-side motor control signal Ms; and a steering-side drive circuit 52 that supplies drive power to the steering-side motor 13 based on the steering-side motor control signal Ms. The steering-side control unit 51 is connected to a steering-side current sensor 45 that detects current values Ius, Ivs, Iws corresponding to each phase flowing through a connection line 53 between the steering-side drive circuit 52 and the motor coils of the steering-side motor 13 corresponding to each phase. The steering-side current sensor 45 obtains the voltage drop in a shunt resistor as current, and the shunt resistor is connected to the source side of each switching element provided in an inverter (not shown) corresponding to the steering-side motor 13. In Figure 2 For ease of description, the connection line 53 corresponding to each phase and the steering-side current sensor 45 corresponding to each phase are both shown as a single component.

[0043] The steering controller 2 includes: a rotation-side control unit 54 that outputs a rotation-side motor control signal Mt; and a rotation-side drive circuit 55 that supplies drive power to the rotation-side motor 32 based on the rotation-side motor control signal Mt. The rotation-side control unit 54 is connected to a rotation-side current sensor 46 that detects current values Iut, Ivt, Iwt corresponding to each phase flowing through a connection line 56 between the rotation-side drive circuit 55 and the motor coils of the rotation-side motor 32 corresponding to each phase. The rotation-side current sensor 46 obtains the voltage drop in a shunt resistor as current, and the shunt resistor is connected to the source side of each switching element provided in an inverter (not shown) corresponding to the rotation-side motor 32. In Figure 2 For ease of description, the connection line 56 corresponding to each phase and the rotation-side current sensor 46 corresponding to each phase are both shown as a single component. As the steering-side drive circuit 52 and the rotation-side drive circuit 55 of the present embodiment, a known PWM inverter including a plurality of switching elements such as FETs is employed. The steering-side motor control signal Ms and the rotation-side motor control signal Mt are gate on / off signals that define the on / off states of the switching elements, respectively.

[0044] The turning side control unit 51 outputs a turning side motor control signal Ms to the turning side drive circuit 52 to control the drive of the turning side motor 13 by supplying drive power from the vehicle-mounted power source B to the turning side motor 13. The rotating side control unit 54 outputs a rotating side motor control signal Mt to the rotating side drive circuit 55 to control the drive of the rotating side motor 32 by supplying drive power from the vehicle-mounted power source B to the rotating side motor 32.

[0045] A description of the function of the turning side control unit 51 is now given. The turning side control unit 51 receives inputs of the steering torque Th, the vehicle speed value V, the turning side rotation angle θs, the current values Ius, Ivs, Iws of each phase, the actual current value Iqt described below, and the rotation angle θp described below. The turning side control unit 51 generates and outputs a turning side motor control signal Ms based on each of these input state quantities of the input state quantities. The actual current value Iqt is calculated based on the current values Iut, Ivt, Iwt of each phase. The rotation angle θp is calculated based on the rotating side rotation angle θt.

[0046] Specifically, the turning side control unit 51 includes: a steering angle calculator 61 that calculates a steering angle θh, which is the rotation angle of the steering wheel 3 (i.e., the steering shaft 11); a target reaction force torque calculator 62 that calculates a target reaction force torque Ts*, which is a target torque serving as a target value for the steering reaction force; and a turning side motor control signal arithmetic unit 63 that calculates the turning side motor control signal Ms.

[0047] The steering angle calculator 61 receives an input of the turning side rotation angle θs. The steering angle calculator 61 converts the turning side rotation angle θs into an integral angle including a 360° range, for example, by counting the number of rotations of the turning side motor 13 relative to the steering neutral position, which is the position of the steering wheel 3 when the vehicle is traveling straight. The steering angle calculator 61 multiplies the integral angle obtained by the conversion by a conversion coefficient based on the speed ratio of the reduction gear 14 to calculate the steering angle θh. The steering angle θh thus obtained is output to the target reaction force torque calculator 62.

[0048] The target reaction force torque calculator 62 receives inputs of the steering torque Th, the vehicle speed value V, the steering angle θh, and the actual current value Iqt. The target reaction force torque operation calculator 62 calculates a target reaction force torque Ts* based on the input state quantities. The obtained target reaction force torque Ts* is output to the steering side motor control signal calculator 63. In the process of calculating the target reaction force torque Ts*, the target reaction force torque calculator 62 also calculates a target steering angle θh*, which is a target value of the steering angle θh of the steering wheel 3. The obtained target steering angle θh* is output to the steering side control unit 54. In the present embodiment, the target reaction force torque calculator 62 is an example of a torque command value calculator, and the target reaction force torque Ts* is an example of a torque command value.

[0049] In addition to the input of the target reaction force torque Ts*, the steering side motor control signal calculator 63 also receives an input of the steering side rotation angle θs, and the current values Ius, Ivs, Iws of each phase. The steering side motor control signal calculator 63 calculates a d-axis target current value Ids* on the d-axis and a q-axis target current value Iqs* on the q-axis in the dq coordinate system based on the target reaction force torque Ts*. The target current values Ids*, Iqs* respectively indicate the target current value on the d-axis and the target current value on the q-axis in the dq coordinate system. Specifically, as the absolute value of the target reaction force torque Ts* becomes larger, the steering side motor control signal calculator 63 calculates a q-axis target current value Iqs* with a larger absolute value. In the present embodiment, the d-axis target current value Ids* on the d-axis is basically set to zero. Then, the steering side motor control signal calculator 63 performs current feedback control in the dq coordinate system to generate a steering side motor control signal Ms to be output to the steering side drive circuit 52. In the following description, the term "feedback" may be written as "FB".

[0050] Specifically, based on the steering-side rotation angle θs, the steering-side motor control signal calculator 63 maps the actual current value Iqs to the dq coordinates to calculate the d-axis actual current value Ids and the q-axis actual current value Iqs, which are the actual current values of the steering-side motor 13 in the dq coordinate system. The steering-side motor control signal calculator 63 calculates the target voltage value based on the deviation of the d-axis and q-axis currents, so as to allow the d-axis actual current value Ids to follow the d-axis target actual current value Ids* and allow the q-axis actual current value Iqs to follow the q-axis target actual current value Iqs*, and generates a steering-side motor control signal Ms for setting the duty ratio based on the calculated target voltage value. The obtained steering-side motor control signal Ms is output to the steering-side drive circuit 52. Therefore, the steering-side motor 13 receives the supply of driving power corresponding to the steering-side motor control signal Ms from the steering-side drive circuit 52. Then, the steering-side motor 13 applies a steering reaction force represented as the target reaction torque Ts* to the steering wheel 3.

[0051] Now, a description of the functions of the rotation-side control unit 54 is given. The rotation-side control unit 54 receives the inputs of the rotation-side rotation angle θt, the target steering angle θh*, and the current values Iut, Ivt, Iwt of each phase. Based on each of these input state quantities of the input state quantities, the rotation-side control unit 54 generates a rotation-side motor control signal Mt and outputs it. In the steering device 1 of the present embodiment, the steering angle ratio, which is the ratio between the steering angle θh and the rotation angle θp, is constantly set to 1:1, and the target rotation angle used as the target value of the rotation angle θp is equal to the target steering angle θh*.

[0052] Specifically, the rotation-side control unit 54 includes: a rotation angle calculator 71 that calculates the rotation angle θp, which is the rotation angle of the pinion shaft 21; a target rotation torque calculator 72 that calculates the target rotation torque Tt*, which is the target value of the rotational force for rotating the rotating wheel 5; and a rotation-side motor control signal calculator 73 that calculates the rotation-side motor control signal Mt.

[0053] The rotation angle calculator 71 receives the input of the rotation-side rotation angle θt of the rotation-side motor 32. The rotation angle calculator 71 converts the input rotation-side rotation angle θt into an integral angle including a range of more than 360° by, for example, counting the number of rotations of the rotation-side motor 32 relative to the rack neutral position, which is the position of the rack shaft 22 when the vehicle is traveling straight. The rotation angle calculator 71 multiplies the integral angle obtained by the conversion by a conversion coefficient based on the reduction ratio of the belt mechanism 33, the lead of the ball screw mechanism 34, and the rotation speed ratio of the rack and pinion mechanism 24 to calculate the rotation angle θp. The obtained rotation angle θp is output to the target rotation torque calculator 72.

[0054] The target rotational torque calculator 72 receives inputs of the target steering angle θh* and the rotational angle θp. The target rotational torque calculator 72 performs an angle FB calculation that allows the rotational angle θp to follow the target steering angle θh* to calculate the target rotational torque Tt*. Specifically, the target rotational torque calculator 72 includes a rotational angle FB control unit 74 that performs the angle FB calculation. The rotational angle FB control unit 74 receives an input of the angle deviation Δθp, which is obtained by subtracting the rotational angle θp from the target steering angle θh* by a subtractor 75, and the target steering angle θh* is the target rotational angle. The target rotational torque calculator 72 calculates the sum of the output values of the proportional element, the integral element, and the derivative element as the target rotational torque Tt*, where the angle deviation θp is used as the input. The thus obtained target rotational torque Tt* is output to the rotational side motor control signal calculator 73.

[0055] In addition to the input of the target rotational torque Tt*, the rotational side motor control signal calculator 73 receives inputs of the rotational side rotation angle θt and the current values Iut, Ivt, Iwt of each phase. The rotational side motor control signal calculator 73 calculates a d-axis target current value Idt* on the d-axis and a q-axis target current value Iqt* on the q-axis in the dq coordinate system based on the target rotational torque Tt*. Specifically, as the absolute value of the target rotational torque Tt* becomes larger, the rotational side motor control signal calculator 73 calculates a q-axis target current value Iqt* with a larger absolute value. In the present embodiment, the d-axis target current value Idt* on the d-axis is basically set to zero. Similar to the steering side motor control signal calculator 63, the rotational side motor control signal calculator 73 performs a current FB operation in the dq coordinate system to generate a rotational side motor control signal Mt to be output to the rotational side drive circuit 55. The actual current value Iqt obtained in the process of generating the rotational side motor control signal Mt by the calculation in the rotational side motor control signal calculator 73 is output to the target reaction force torque calculator 62 of the steering side control unit 51. The thus obtained rotational side motor control signal Mt is output to the rotational side drive circuit 55. Accordingly, the rotational side motor 32 receives the supply of drive power corresponding to the rotational side motor control signal Mt from the rotational side drive circuit 55. Then, the rotational side motor 32 applies a turning force represented as the target rotational torque Tt* to the turning wheel 5.

[0056] A description of the function of the target reaction force torque calculator 62 is now given. As Figure 3As shown, the target reaction force torque calculator 62 includes an input torque component calculator 81 that calculates a torque FB component Tfbt as an input torque component, which is a force for rotating the steering wheel 3 in the direction of the driver's steering. The target reaction force torque calculator 62 further includes a reaction force component calculator 82 that calculates a force that resists the rotation of the steering wheel 3 steered by the driver, that is, a distributed axial force Fir, which is an axial force acting on the rack shaft 22 from the rotating wheel 5. The target reaction force torque calculator 62 further includes a target steering angle calculator 83 that calculates a target steering angle θh* and a steering angle FB component calculator 84 that calculates a steering angle FB component Tfbh.

[0057] Specifically, the input torque component calculator 81 includes: a target steering torque calculator 91 that calculates a target steering torque Thb* that serves as a target value of the steering torque Th to be input to the steering wheel 3; and a hysteresis component calculator 92 that calculates a hysteresis component Thy*, which is added so that the target steering torque Thb* has a hysteresis characteristic and changes accordingly. The input torque component calculator 81 further includes a torque FB component calculator 93 that calculates the torque FB component Tfbt by performing torque FB calculation.

[0058] The target steering torque calculator 91 receives an input of a drive torque Tc, which is obtained by adding the torque FB component Tfbt and the steering torque Th by an adder 94. The target steering torque calculator 91 calculates a target steering torque Thb*, and the absolute value of the target steering torque Thb* becomes larger as the absolute value of the drive torque Tc becomes larger. The drive torque Tc is a torque for rotating the rotating wheel 5 in a configuration where the steering mechanism 4 and the rotating mechanism 6 are mechanically coupled to each other. The drive torque Tc indicates a force that is substantially balanced with the axial force acting on the rack shaft 22. In short, the drive torque Tc corresponds to the estimated and calculated axial force acting on the rack shaft 22.

[0059] The hysteresis component calculator 92 receives inputs of a rotation angle θp and a vehicle speed value V. The hysteresis component calculator 92 calculates the hysteresis component Thy* based on the rotation angle θp and the vehicle speed value V. A specific method for calculating the hysteresis component Thy* will be described in detail later. The hysteresis component Thy* thus obtained is added to the target steering torque Thb*, and output to a subtractor 96 as the target steering torque Th* obtained by an adder 95. The target steering torque Th* thus obtained is further subtracted from the steering torque Th, and the result is output to the torque FB component calculator 93 as a torque deviation △Th obtained by the subtractor 96.

[0060] The torque FB component calculator 93 receives an input of the torque deviation ΔTh. Based on the torque deviation ΔTh, the torque FB component calculator 93 performs torque FB (i.e., torque feedback control) calculation to allow the steering torque Th to follow the target steering torque Th* to calculate the torque FB component Tfbt. The torque FB component calculator 93 calculates the sum of the output values of the proportional element, integral element, and derivative element as the torque FB component Tfbt, where the torque deviation ΔTh is used as the input. The thus obtained torque FB component Tfbt is output to the adder 94 and the target steering angle calculator 83. The torque FB component Tfbt is also output to the adder 85 described later.

[0061] The reaction force component calculator 82 includes: an angular axial force calculator 101 that calculates the axial force acting on the rotating wheel 5, i.e., the angular axial force Fib, which is the ideal value of the transmission force transmitted to the steering wheel 5; and a current axial force calculator 102 that calculates the axial force acting on the steering wheel 5, i.e., the current axial force Fer, which is the estimate of the transmission force transmitted to the rotating wheel 5. The reaction force component calculator 82 includes a distributed axial force calculator 103 that calculates the distributed axial force Fir, and the distributed axial force Fir corresponds to the estimated and calculated axial force acting on the rack shaft 22 obtained by adding the angular axial force Fib and the current axial force Fer at a specified distribution ratio. In the present embodiment, the angular axial force Fib is calculated as the ideal value of the axial force defined by the optional vehicle model. The angular axial force Fib is calculated as the axial force that does not reflect the road surface information, such as minute unevenness that does not affect the vehicle's behavior in the lateral direction and level differences that affect the vehicle's behavior in the lateral direction. The current axial force Fer is calculated as an estimate of the axial force actually acting when the vehicle is running or stopped, and is calculated as the axial force that reflects the road surface information. Each of the axial forces Fib and Fer is calculated in units of torque (N·m).

[0062] The angular axial force calculator 101 receives inputs of the rotation angle θp and the vehicle speed value V. The angular axial force calculator 101 calculates the angular axial force Fib that has a larger absolute value as the absolute value of the rotation angle θp becomes larger. The angular axial force calculator 101 also calculates the angular axial force Fib whose absolute value becomes larger as the vehicle speed value V becomes larger. The thus obtained angular axial force Fib is output to the distributed axial force calculator 103.

[0063] The current axial force calculator 102 receives an input of the actual current value Iqt. The current axial force calculator 102 calculates the current axial force Fer that has a larger absolute value as the absolute value of the actual current value Iqt becomes larger. The thus obtained current axial force Fer is output to the distributed axial force calculator 103.

[0064] The distributed axial force calculator 103 receives inputs of the angular axial force Fib, the current axial force Fer, and the vehicle speed value V. The distributed axial force calculator 103 adds the angular axial force Fib and the current axial force Fer together to calculate the distributed axial force Fir, and at the same time, based on the vehicle speed value V, adjusts the distribution ratio of the axial force Fib to be smaller and the distribution ratio of the current axial force Fer to be larger as the vehicle speed value V increases.

[0065] The target steering angle calculator 83 receives inputs of the vehicle speed value V, the steering torque Th, the torque FB component Tfbt, and the distributed axial force Fir. The target steering angle calculator 83 uses the steering model expression of Expression (1) shown below to calculate the target steering angle θh*. Expression (1) associates the input torque Tin* with the target steering angle θh*, and the input torque Tin* is obtained by adding the steering torque Th to the torque FB component Tfbt and subtracting the distributed axial force Fir from the torque FB component Tfbt.

[0066] Tin* = C·θh*' + J·θh*” (1)

[0067] This model expression defines and represents the relationship between the torque and the rotation angle of the rotation axis that rotates in relation to the rotation of the steering wheel 3 in a configuration where the steering wheel 3 and the rotating wheel 5 are mechanically coupled to each other, that is, in a configuration where the steering mechanism 4 and the rotating mechanism 6 are mechanically coupled. The model expression is represented using the viscous coefficient C that simulates the frictional force of the simulation steering device 1 and the inertia coefficient J that simulates the inertia of the simulation steering device 1. The viscosity coefficient C and the inertia coefficient J are variably set according to the vehicle speed value V. The obtained target steering angle θh* is output to the target steering torque calculator 72 and the steering angle FB component calculator 84.

[0068] The steering angle FB component calculator 84 receives an input of the angle deviation Δθp, which is obtained by subtracting the steering angle θh from the target steering angle θh* by the subtractor 86. The steering angle FB component calculator 84 calculates the steering angle FB component Tfbh by performing an angle FB calculation for allowing the steering angle θh to follow the target steering angle θh* based on the angle deviation Δθp. Specifically, the steering angle FB component calculator 84 calculates the sum of the output values of the proportional element, the integral element, and the derivative element as the steering angle FB component Tfbh, where the angle deviation Δθp is used as the input. The obtained steering angle FB component Tfbh is added to the torque FB component Tfbt and output as the target reaction torque Ts* obtained by the adder 85 to the steering side motor control signal calculator 63.

[0069] In the present embodiment, the target reaction force torque calculator 62 calculates a target steering torque Th* for torque FB calculation based on the driving torque Tc which is the calculated axial force. The target reaction force torque calculator 62 also calculates a target steering angle θh* for angle FB calculation based on the distributed axial force Fir which is the calculated axial force, and adds the target steering torque Th* and the target steering angle θh* to obtain a target reaction force torque Ts*. Therefore, the steering reaction force applied by the steering side motor 13 basically acts as a force that resists the driver's steering. However, the steering reaction force can also act as a force that assists the driver's steering according to the deviation between the calculated axial force and the actual axial force acting on the rack shaft 22.

[0070] Here, the function of the hysteresis component calculator 92 is described in more detail. As Figure 4 shown, the hysteresis component calculator 92 includes: a hysteresis basic component calculator 111 that calculates a hysteresis basic component Thyb* which is a basic component of the hysteresis component Thy*; and a hysteresis differential component calculator 112 that calculates a hysteresis differential component Thyd* which is a differential value of the hysteresis basic component Thyb*.

[0071] The hysteresis basic component calculator 111 receives inputs of a vehicle speed value V, a steering angle θp, and an angular velocity ωp. The angular velocity ωp is a differential value obtained by differentiating the steering angle θp by a differentiator 113. The angular velocity ωp is the amount of change in the steering angle θp of the pinion shaft 21 that rotates in relation to the steering of the steering wheel 3.

[0072] As Figure 5A and Figure 5B shown, the hysteresis basic component calculator 111 includes hysteresis diagrams M1, M2 that define the relationship between the steering angle θp and the hysteresis basic component Thyb*. The hysteresis basic component calculator 111 uses the steering angle θp as an input to perform the calculation of the hysteresis basic component Thyb*. The hysteresis basic component calculator 111 performs the graph calculation of the hysteresis basic component Thyb* using one of the hysteresis diagrams M1, M2 according to whether the steering is a turning steering or a returning steering determined based on the signs or changes of the steering angle θp and the angular velocity ωp. In the present embodiment, the turning steering is a steering continuously performed in the same direction, and the returning steering is a steering performed only when the steering angle θp after the change of the steering direction is within a smaller specified range. In the hysteresis diagrams M1, M2, the term "θp" represents the amount of change in the steering angle θp with the steering angle θp at the starting position of using the turning steering or the returning steering as the origin.

[0073] Specifically, the hysteresis basic component calculator 111 calculates the hysteresis basic component Thyb* using the hysteresis diagram M1 during a turning steering. In this case, the hysteresis basic component Thyb* is calculated such that when the absolute value of the turning angle θp becomes larger, the absolute value of the hysteresis basic component Thyb* becomes larger, and the absolute value of the hysteresis gradient becomes smaller. The hysteresis gradient is the change amount of the hysteresis basic component Thyb* with respect to the turning angle θp at the rising edge of the hysteresis basic component Thyb*. When the turning angle θp is within a specified range or a larger range, the absolute value of the hysteresis basic component Thyb* in this case saturates. The value at this time is calculated to be the maximum value Tmax or larger.

[0074] During the execution of a right turning steering, the hysteresis basic component calculator 111 uses the value shown in the first quadrant of the hysteresis diagram M1 with the turning angle θp at the starting position of the turning steering as the origin. During a left turning steering, the hysteresis basic component calculator 111 uses the value shown in the third quadrant of the hysteresis diagram M1 with the turning angle θp at the starting position of the turning steering as the origin.

[0075] Meanwhile, during a return steering, the hysteresis basic component calculator 111 calculates the hysteresis basic component Thyb* using the hysteresis diagram M2. In this case, the hysteresis basic component Thyb* is calculated in proportion to the turning angle θp. The hysteresis basic component Thyb* in this case is calculated only when the turning angle θp is within a specified range from the origin.

[0076] During the execution of a right return steering, the hysteresis basic component calculator 111 uses the value shown in the first quadrant of the hysteresis diagram M2 with the turning angle θp at the starting position of the return steering as the origin only when the turning angle θp is within a specified range from the origin. During the execution of a left return steering, the hysteresis basic component calculator 111 uses the value shown in the third quadrant of the hysteresis diagram M2 with the turning angle θp at the starting position of the return steering as the origin only when the turning angle θp is within a specified range from the origin.

[0077] In the present embodiment, the hysteresis diagrams M1 and M2 are configured to change the hysteresis basic component Thyb* according to the angular velocity ωp, and are also configured to change the hysteresis basic component Thyb* according to the vehicle speed value V. For the purpose of achieving a desired steering feel, the hysteresis diagrams M1 and M2 change the hysteresis basic component Thyb* according to the angular velocity ωp or the vehicle speed value V. In the present embodiment, for example, the hysteresis basic component Thyb* is changed such that when the angular velocity ωp is large, the hysteresis gradient becomes smaller and the responsiveness decreases. The hysteresis basic component Thyb* is also changed such that when the vehicle speed value V is small, the hysteresis gradient becomes larger and the responsiveness increases.

[0078] Therefore, as Figure 6As shown, in the case of performing, for example, sinusoidal steering in which the turning steering and the returning steering of the steering wheel 3 are periodically repeated at a constant frequency, the hysteresis basic component calculator 111 calculates a hysteresis basic component Thyb* having a hysteresis characteristic with respect to a change in the turning angle θp. The obtained hysteresis basic component Thyb* is output to the hysteresis differential component calculator 112 and the adder 114. In the present embodiment, specifically, the target steering torque calculator 91 of the input torque component calculator 81 is an example of a command value component calculator, the target steering torque Thb* is an example of a command value component, and the turning angle θp is an example of a state quantity that changes according to the operation of the steering device 1.

[0079] The hysteresis differential component calculator 112 receives the input of the hysteresis basic component Thyb* and the vehicle speed value V. The hysteresis differential component calculator 112 multiplies the value obtained by differentiating the hysteresis basic component Thyb* by the differentiator 115 by a gain Ky corresponding to the vehicle speed value V to calculate a hysteresis differential component Thyd*, which is a differential component of the hysteresis basic component Thyb* obtained by the multiplier 116. In the present embodiment, the hysteresis differential component Thyd* is calculated as a component that suppresses the vibration response characteristic generated in the hysteresis basic component Thyb*.

[0080] In the present embodiment, since the hysteresis basic component Thyb* is changed based on the vehicle speed value V, the hysteresis differential component Thyd* is changed based on the vehicle speed value V during a natural event. At the same time, for the purpose of improving the steering feel, the hysteresis differential component Thyd* is configured to be adjusted and changed to an appropriate component based on the gain Ky corresponding to the vehicle speed value V.

[0081] The obtained hysteresis differential component Thyd* is added to the hysteresis basic component Thyb* and output as a hysteresis basic component Thy* obtained by the adder 114 to the adder 95. In the present embodiment, by adding to the hysteresis basic component Thy*, the hysteresis differential component Thyd* is added as a component that suppresses the vibration response characteristic generated in the hysteresis basic component Thyb*. By adding to the target steering torque Th*, the hysteresis component Thy* is added as a component that makes the target steering torque Th* have a hysteresis characteristic and accordingly changes. In the present embodiment, considering that the hysteresis component Thy* functions to suppress the vibration response characteristic generated in the hysteresis basic component Thyb*, the same effect can be obtained even when the hysteresis differential component Thyd* is added by subtracting from the hysteresis basic component Thyb*.

[0082] Hereinafter, the effects of the present embodiment will be described. In the present embodiment, by adding a hysteresis basic component Thyb*, steering response can be provided to the driver.

[0083] As Figure 7 shown, for example, when performing sinusoidal steering, the steering characteristics indicated by the relationship between the rotation angle θp and the target steering torque Th* show characteristics having a hysteresis characteristic based on the hysteresis basic component Thyb* and changing accordingly. Then, the hysteresis gradient, which is the gradient at the rising edge of the hysteresis basic component Thyb*, affects the following situations: for example, when starting a rightward rotational steering from the origin where the rotation angle θp is zero, and when starting a leftward rotational steering after a rightward rotational steering followed by a leftward return steering, particularly.

[0084] In other words, in order to give the driver a significant response as a steering response, it can be thought of to increase the hysteresis gradient of the hysteresis basic component Thyb*, and thereby enhance the responsiveness. In this case, when the hysteresis gradient is forcibly increased and thus the responsiveness is excessively enhanced, due to reasons such as insufficient response performance, the vibration response characteristics in the hysteresis basic component Thyb* become significant, which is disadvantageous in terms of stability. In other words, increasing the hysteresis gradient of the hysteresis basic component Thyb* and enhancing the responsiveness for the purpose of giving the driver a significant response have limitations.

[0085] As a solution, in the present embodiment, the hysteresis differential component Thyd* serves to suppress the vibration response characteristics generated in the hysteresis basic component Thyb*. This means that when the hysteresis gradient of the hysteresis basic component Thyb* increases, the vibration response characteristics can be suppressed. Therefore, compared with the case where the hysteresis differential component Thyb* is not added, the limitations of the responsiveness can be expanded, and the responsiveness can be enhanced by increasing the hysteresis gradient of the hysteresis basic component Thyb*.

[0086] Specifically, Figure 8 shows Figure 5A an enlarged portion of the first quadrant in the hysteresis diagram M1 shown. The first quadrant corresponds to the time of starting a rightward rotational steering from the origin where the rotation angle θp is zero. The absolute value of the hysteresis gradient of the hysteresis basic component Thyb* can be designed as shown by the solid line, which increases from the imaginary line indicated by the arrow in the figure. The same applies to the absolute value of the hysteresis gradient of the hysteresis basic component Thyb* in the third quadrant, which corresponds to the time of starting a leftward rotational steering from the origin where the rotation angle θp is zero in the hysteresis diagram M1.

[0087] In this relationship, Figure 9 shows an enlarged portion of the first quadrant, which corresponds to starting from having Figure 7The origin with a rotation angle of zero for the steering characteristics shown rotates to the right corresponding to the steering. As shown by the solid line increasing from the imaginary line shown by the arrow in the figure, the absolute value of the gradient of the change of the target steering torque Th* with respect to the rotation angle θp at the start of the rightward rotation can be changed. As Figure 9 shown, after performing a return steering to the left, the absolute value of the gradient of the target steering torque Th* can increase with respect to the change in the rotation angle θp at the start of the leftward rotational steering, as shown by the arrow in the figure.

[0088] Hereinafter, the effects of the present embodiment will be described. (1) In the present embodiment, when calculating the hysteresis component Thy*, the hysteresis differential component Thyd* is added to the hysteresis basic component Thyb*. Therefore, in the present embodiment, compared with the case where the hysteresis differential component Thyd* is not added, the hysteresis basic component Thyb* with a larger hysteresis gradient and enhanced responsiveness can be designed. As a result, a significant response can be given to the driver, and an improvement in the steering feel can be achieved.

[0089] (2) In the present embodiment, when the hysteresis basic component Thyb* changes based on the angular velocity ωp, the hysteresis basic component Thyb* is changed such that when the angular velocity ωp is large, the hysteresis gradient becomes smaller and the responsiveness decreases. This enables the driver to perform a smooth steering operation with a steering response suppressed in the case of rapid steering. Therefore, a significant response can be given to the driver, or the driver can perform a smooth steering operation, and an appropriate steering feel corresponding to the steering state of the steering wheel 3 can be set. Therefore, the present embodiment is effective for achieving an improvement in the steering feel.

[0090] (3) In the present embodiment, when the hysteresis basic component Thyb* changes based on the vehicle speed value V, the hysteresis basic component Thyb* is changed such that when the vehicle speed value V is small, the hysteresis gradient becomes larger and the responsiveness is enhanced. This enables a sufficient response to be given to the driver when parking the vehicle. Therefore, a significant response or a sufficient response is given to the driver, and an appropriate steering feel corresponding to the driving state of the vehicle is set. Therefore, the present embodiment is effective for achieving an improvement in the steering feel.

[0091] (4) Here, when the hysteresis basic component Thyb* changes based on the vehicle speed value V, the hysteresis differential component, which is a component obtained by differentiating the hysteresis basic component Thyb*, also changes based on the vehicle speed value V during the natural event process. However, the hysteresis differential component that changes based on the vehicle speed value V during the natural event process is not necessarily suitable for the purpose of improving the steering feel.

[0092] Therefore, in the present embodiment, when the hysteresis basic component Thyb* changes based on the vehicle speed value V, the hysteresis differential component Thyd* changes based on the vehicle speed value V. As a result, the hysteresis differential component Thyd* is adjusted to an appropriate component to achieve an improvement in the steering feel. Therefore, the present embodiment contributes to the improvement of the steering feel.

[0093] Second Embodiment

[0094] A description of a second embodiment of the steering controller will now be given. Component members similar to those in the previously described embodiments are denoted by similar symbols to omit redundant descriptions.

[0095] As Figure 10 shown, the input torque component calculator 81 of the present embodiment includes an auxiliary basic component calculator 122 that calculates an auxiliary basic component Tb* that serves as a basic component of the motor torque to be output with respect to the steering torque Th input to the steering wheel 3. The input torque component calculator 81 further includes a first hysteresis component calculator 123 that calculates a first hysteresis component Tby* that is added so that the auxiliary basic component Tb* has a hysteresis characteristic and changes accordingly. The input torque component calculator 81 further includes a second hysteresis component calculator 121 that calculates a second hysteresis component. Similar to the first hysteresis component Tby*, the second hysteresis component Ty is added so that the auxiliary basic component Tb* has a hysteresis characteristic and changes accordingly. In the present embodiment, the auxiliary basic component calculator 122 of the input torque component calculator 81 is an example of a command value component calculator, the auxiliary steering torque Tb* is an example of a command value component, and the rotation angle θp and the steering torque Th are examples of state quantities that change according to the operation of the steering device 1.

[0096] The second hysteresis component calculator 121 receives inputs of the steering torque Th and the rotation angle θp. The second hysteresis component calculator 121 calculates an apparent steering torque Th' that is configured such that the absolute value of the steering torque Th becomes smaller than the actual value to provide a motor torque equal to or greater than a predetermined motor torque as the motor torque to be output with respect to the steering torque Th. The second hysteresis component calculator 121 basically calculates the actual value of the absolute value of the steering torque Th near the rack neutral position where the rotation angle θp is zero as the steering torque Th'. The second hysteresis component calculator 121 also calculates the steering torque Th' such that the absolute value of the steering torque Th becomes smaller than the actual value when the absolute value of the rotation angle θp is large. The thus obtained steering torque Th' is output to the auxiliary basic component calculator 122 and the target steering angle calculator 125.

[0097] The second hysteresis component calculator 121 is configured similarly to the hysteresis component calculator 92 of the first embodiment. In the second hysteresis component calculator 121, the steering torque Th is used in place of the rotation angle θp, the basic steering torque component Thb is used in place of the basic hysteresis component Thy b*, and the differential steering torque component Thd, which is a value obtained by differentiating the basic steering torque component Thb, is used in place of the differential hysteresis component Thy d*. In the second hysteresis component calculator 121, the hysteresis component Thy* is replaced with the steering torque Th' obtained by adding the basic steering torque component Thb and the differential steering torque component Thd. The second hysteresis component calculator 121 includes a graph that changes the vertical axes of the hysteresis graphs M1 and M2 shown in Figure 5A and Figure 5B to the difference "ΔTh" for setting the absolute value of the steering torque Th to be smaller than the actual value. This embodiment is similar to the first embodiment in that the differential steering torque component Thd is added by subtracting from the basic steering torque component Thb.

[0098] The auxiliary basic component calculator 122 receives inputs of the steering torque Th' and the vehicle speed value V. The auxiliary basic component calculator 122 calculates and generates an auxiliary basic component Tb* based on the steering torque Th' and the vehicle speed value V. When the absolute value of the steering torque Th' is large and the vehicle speed value V is small, the auxiliary basic component calculator 122 calculates an auxiliary basic component Tb* with a larger absolute value. Specifically, in this embodiment, the auxiliary basic component Tb* is calculated by torque feedforward control of the steering torque Th. The obtained auxiliary basic component Tb* is output to the adder 124.

[0099] The first hysteresis component calculator 123 receives inputs of the rotation angle θp and the vehicle speed value V. The first hysteresis component calculator 123 calculates a first hysteresis component Tby* based on the rotation angle θp and the vehicle speed value V. The obtained first hysteresis component Tby* is added to the auxiliary basic component Tb*, and is output as the auxiliary component Tb* obtained by the adder 124 to the target steering angle calculator 125.

[0100] The first hysteresis component calculator 123 is configured similarly to the hysteresis component calculator 92 of the first embodiment. The basic first hysteresis component Tbyb* is used in place of the basic hysteresis component Thy b*, and the first differential hysteresis component Tbyd*, which is a value obtained by differentiating the basic first hysteresis component Tbyb*, is used in place of the differential hysteresis component Thy d*. In the first hysteresis component calculator 123, the hysteresis component Thy* is replaced with the first hysteresis component Tby* obtained by adding the basic first hysteresis component Tbyb* and the first differential hysteresis component Tbyd*. The first hysteresis component calculator 123 includes a graph that changes the vertical axes ofFigure 5A and Figure 5B The vertical axes of the hysteresis diagrams M1 and M2 shown in Figure 5B are changed to a diagram of the first hysteresis basic component Tbyb*. This embodiment is similar to the first embodiment in that the first hysteresis differential component Tbyd* can be added by subtracting from the first hysteresis basic component Tbyb*.

[0101] The target steering angle calculator 125 of this embodiment receives inputs of the vehicle speed value V, the steering torque Th', the assist component Tb*', and the distributed axial force Fir:. The target steering angle calculator 125 uses the steering model expression of the same expression (1) as in the first embodiment to calculate the target steering angle θh*. Expression (1) associates the input torque Tin* with the target steering angle θh*, and the input torque Tin* is obtained by adding the steering torque Th' to the assist component Tb*' and subtracting the distributed axial force Fir from the assist component Tb*'. The obtained target steering angle θh* is output to the target rotational torque calculator 72 and the steering angle FB component calculator 84.

[0102] In addition to the functions and effects corresponding to those of the first embodiment, this embodiment exhibits the following effects. (5) When torque feedforward control of the steering torque Th is employed in calculating the assist basic component Tb* as in this embodiment, unlike the first embodiment in which torque feedback control is used to control the steering torque Th to reach the target value, the steering torque Th varies during natural events. In this case, even when the first hysteresis component Tby* is added to the assist basic component Tb* to provide hysteresis characteristics, the addition of the first hysteresis component Tby* is not reflected over the entire range of the rotation angle θp. For example, in some cases, when the rotation angle θp is far from the rack neutral position where the rotation angle θp is zero, the addition of the first hysteresis component Tby* is less reflected. Near the upper limit of the rotation angle θp, the addition of the first hysteresis component Tby* can hardly be reflected. In this case, near the upper limit of the rotation angle θp, the assist basic component Tb* has almost no hysteresis characteristics.

[0103] To address this situation, in the present embodiment, in order to endow the auxiliary basic component Tb* with a hysteresis characteristic throughout the entire range of the rotation angle θp, the absolute value of the steering torque Th near the upper limit of the rotation angle θp is replaced with an apparently smaller steering torque Th' than the actual value. As a result, near the upper limit of the rotation angle θp, a motor torque smaller than the motor torque required at this time is output. Therefore, in order to rotate the rotating wheel 5, the driver needs to input a steering torque Th having a larger absolute value compared to the actual steering torque Th. In this case, the absolute value of the steering torque Th provided by the driver becomes larger, and as a result, the absolute value of the auxiliary basic component Tb* becomes larger to increase the motor torque output. Therefore, the auxiliary basic component Tb* has a hysteresis characteristic even near the upper limit of the rotation angle θp, which may contribute to achieving a desired steering feel.

[0104] Third Embodiment

[0105] A description of a third embodiment of the steering controller is now given. Component members similar to those in the previously described embodiments are denoted by similar symbols to omit redundant descriptions.

[0106] As Figure 11 shown, the angle axial force calculator 101 of the present embodiment calculates the angle axial force Fib to have a hysteresis characteristic. Specifically, the angle axial force calculator 101 includes: an angle axial force basic component calculator 131 that calculates an angle axial force basic component Fibb as the basic component of the angle axial force Fib; and a hysteresis component calculator 132 that calculates a hysteresis component Fibby, which is added such that the angle axial force Fib has a hysteresis characteristic and changes accordingly. In the present embodiment, the angle axial force calculator 101 is an example of a command value component calculator, the angle axial force Fib is an example of a command value component, and the rotation angle θp is an example of a state quantity that changes according to the operation of the steering device 1.

[0107] The angle axial force basic component calculator 131 receives inputs of the rotation angle θp and the vehicle speed value V. The angle axial force basic component calculator 131 calculates the angle axial force Fib calculated by the angle axial force calculator 101 of the first embodiment as the angle axial force basic component Fibb. The thus obtained angle axial force basic component Fibb is output to the adder 133.

[0108] The lag component calculator 132 receives inputs of the rotational angle θp and the vehicle speed value V. The lag component calculator 132 calculates a lag component Fibby based on the rotational angle θp and the vehicle speed value V. The resulting lag component Fibby is added to the angular axial force basic component Fibb and output as the angular axial force Fib obtained by the adder 133 to the distributed axial force calculator 103.

[0109] The lag component calculator 132 is configured similarly to the lag component calculator 92 of the first embodiment. The lag basic component Fibbyb is used in place of the lag basic component Thyb*, and the lag differential component Fibbyd is used in place of the lag differential component Thyd*, where the lag differential component Fibbyd is a value obtained by differentiating the lag basic component Fibbyb. In the lag component calculator 132, the lag component Fibby obtained by adding the lag basic component Fibbyb and the lag differential component Fibbyd is used in place of the lag component Thy*. The lag component calculator 132 includes changing the Figure 5A and Figure 5B vertical axes of the lag diagrams M1 and M2 shown in to diagrams of the differential lag basic component Fibbyb. This embodiment is similar to the first embodiment in that the lag differential component Fibbyd can be added by subtracting from the lag basic component Fibbyb. This embodiment is not limited to being configured and applied by changing the configuration of the angular axial force calculator 101 of the first embodiment. This embodiment can also be configured and applied by changing the configuration of the angular axial force calculator 101 of the second embodiment.

[0110] This embodiment shows functions and effects corresponding to those of the first embodiment. Each embodiment can be changed as follows. Without departing from the scope of technical consistency, the other embodiments shown below can be combined with each other.

[0111] In the first embodiment, the lag differential component Thyd* may not be changed based on the vehicle speed value V. This also applies to the differential components corresponding to the lag differential component Thyd* in the second and third embodiments.

[0112] In the first embodiment, for example, the aspect of changing the lag basic component Thyb* based on the vehicle speed value V can be appropriately modified such that when the vehicle speed value V is small, the lag gradient becomes smaller and the responsiveness becomes lower. This also applies to the basic components corresponding to the lag basic component Thyb* in the second and third embodiments.

[0113] In the first embodiment, for example, the aspect of changing the hysteresis basic component Thyb* based on the angular velocity ωp can be appropriately modified such that when the angular velocity ωp is large, the hysteresis gradient becomes larger and the responsiveness becomes higher. This also applies to the basic components corresponding to the hysteresis basic component Thyb* in the second and third embodiments.

[0114] In the first embodiment, the hysteresis basic component Thyb* can be changed based on the angular acceleration αp instead of the angular velocity ωp. This also applies to the basic components corresponding to the hysteresis basic component Thyb* in the second and third embodiments.

[0115] In the first embodiment, when calculating the hysteresis differential component Thyd*, instead of the differential method, for example, the method of calculating the change amount of the hysteresis basic component Thyb* and using it as the differential component, or the method of performing filtering processing with a phase lead filter and using the result as the differential component can be used.

[0116] In the first embodiment, the rotation angle θp is used for the calculation of various components. However, various components can also be calculated based on any state quantity related to the rotation angle θp (i.e., the steering angle of the rotating wheel 5). Examples of the state quantity related to the steering angle of the rotating wheel 5 include: the target steering angle θh* (i.e., the target rotation angle), the steering angle θh, the steering side rotation angle θs, and the rotating side rotation angle θt. These state quantities are also examples of the state quantities that change according to the operation of the steering device 1. Specifically, the hysteresis basic component Thyb* and the angular axial force Fib can be calculated based on, for example, the target steering angle θh*. This variant can also provide the same effect as the first embodiment. This is also the case in the second and third embodiments.

[0117] In the first embodiment, the control configuration can be constructed such that the torque FB component Tfbt is equal to the target reaction torque Ts*. The control configuration can also be constructed such that the steering angle FB component without adding the torque FB component Tfbt is equal to the target reaction torque Ts*.

[0118] In the first embodiment, when calculating the target steering torque Thb* in the target steering torque calculator 91, at least the steering torque Th can be used, and the vehicle speed value can be omitted, or other elements can be used in combination. This is the same in the case of calculating the auxiliary basic component Tb* in the second embodiment. In this case, at least the steering torque Th' can be used, and the vehicle speed value V can be omitted, or other elements can be used in combination.

[0119] In the first embodiment, when the hysteresis basic component calculator 111 calculates the hysteresis basic component Thyb* in the hysteresis component calculator 92, the rotational angle θp can be used at least, and the vehicle speed value V and the angular velocity ωp can be omitted, or other elements can be used in combination. When the hysteresis differential component calculator 112 calculates the hysteresis differential component Thyd*, the hysteresis basic component Thyb* can be used at least, and the vehicle speed value V can be omitted, or other elements can be used in combination. This is the same in the case of calculating components corresponding to various components in the second and third embodiments.

[0120] In the first embodiment, when calculating the hysteresis component Thy* in the hysteresis component calculator 92, the hysteresis differential component Thyd* can be added to the hysteresis basic component Thyb* only during the end-side steering in the rotational steering, and the end-side steering is performed in a direction separated from the rack neutral position where the rotational angle θp is zero. In this case, the hysteresis basic component calculator 111 or the hysteresis differential component calculator 112 can determine whether the end-side steering is in operation based on the steering torque Th, etc., or an additional calculator can be provided to perform this determination. In this example, different from the Figure 9 case shown, after performing a left return steering, it is difficult to increase the absolute value of the gradient of the target steering torque Th* with respect to the change in the rotational angle θp at the start of the rotational steering to the left, as shown by the arrow in the figure. However, in terms of improving the steering feel, sufficient effects are provided. This is also the case for the calculator corresponding to the hysteresis component calculator 92 in the second and third embodiments.

[0121] In the first embodiment, when calculating the angular axial force Fib in the angular axial force calculator 101, the rotational angle θp can be used at least, and the vehicle speed value V can be omitted, or other elements can be used in combination. This also applies to the case where the current axial force calculator 102 calculates the current axial force Fer, and the case where the distributed axial force calculator 103 calculates the distributed axial force Fir. This also applies to the case of the third embodiment, where the angular axial force basic component calculator 131 in the angular axial force calculator 101 calculates the angular axial force basic component Fibb.

[0122] In the second embodiment, when at least providing the configuration of the first hysteresis component calculator 123, the configuration of the second hysteresis component calculator 121 can be eliminated. Even in this case, functions and effects corresponding to those of the first embodiment can be exhibited.

[0123] In each embodiment, the steering angle ratio between the steering angle θh and the rotation angle θp is set to be constant. However, the steering angle ratio may vary according to the vehicle speed value V, the rotation angle θp, etc. In this case, the target steering angle θh* and the target rotation angle take different values.

[0124] In each embodiment, instead of the expression (1), a model expression of the spring coefficient K determined by using the specifications of the wheel alignment or the suspension of the vehicle can be utilized to calculate the target steering angle θh*, and this model expression is modeled by adding a so-called spring term.

[0125] In each embodiment, it is possible to adopt a configuration such that the rotation-side motor 32 is arranged coaxially with the rack shaft 22, or such that the rotation-side motor 32 is coupled to the rack shaft 22 through a worm reducer and the rack and pinion mechanism can be used as the rotation-side actuator 31.

[0126] In each embodiment, the CPU constituting the steering controller 2 can be implemented as: one or more processors that execute a computer program, such as one or more dedicated hardware circuits of an application-specific integrated circuit that execute at least some of various processes, or a circuit including a combination of a processor and a dedicated hardware circuit. The memory can include any available medium that can be accessed by a general-purpose computer or a dedicated computer.

[0127] In each embodiment, the steering device 1 has a linkless structure in which the steering mechanism 4 and the rotation mechanism 6 are always mechanically separated. However, not limited thereto, the steering device 1 may have a structure in which the steering mechanism 4 and the rotation mechanism 6 can be mechanically separated by a clutch. The steering device 1 can be configured as an electric power steering device that applies an auxiliary force for assisting the steering of the steering wheel 3. In this case, the steering wheel 3 is mechanically connected to the pinion shaft 21 through the steering shaft 11.

[0128] Next, the technical concepts that can be recognized from each embodiment and modification will be further described below. The command value component calculator calculates the target steering torque as a command value component. This target steering torque is used as the target value of the steering torque to be input to the steering wheel. The torque command value calculator calculates the torque command value by performing feedback control for allowing the steering torque input to the steering wheel to follow the target steering torque. A hysteresis basic component is added so that the target steering torque has a hysteresis characteristic and changes accordingly with the change of the state quantity, and the state quantity is the angle of the rotating shaft that rotates in relation to the steering of the steering wheel.

[0129] With the above configuration, in the case of adopting torque feedback control for controlling the steering torque to be consistent with the target value, a significant response can be given to the driver, and an improvement in the steering feel can be achieved.

[0130] The command value component calculator calculates the target motor torque as a command value component, and this target motor torque is used as the target value of the motor torque to be generated by the motor with respect to the steering torque input to the steering wheel. The torque refers to the torque command value calculated by the command value calculator by performing the feedforward control of the steering torque. A hysteresis basic component is added so that the target motor torque has a hysteresis characteristic and changes accordingly with the change of the state quantity, and the state quantity is the angle of the rotating shaft that rotates in relation to the steering of the steering wheel.

[0131] With the above configuration, when the torque feedforward control of the steering torque is adopted in the calculation of the command value component, a significant response can be given to the driver, and the improvement of the steering feeling can be achieved.

[0132] The command value component calculator calculates the target motor torque as a command value component, and this target motor torque is used as the target value of the motor torque to be generated by the motor with respect to the steering torque input to the steering wheel. The torque refers to the torque command value calculated by the command value calculator by performing the feedforward control of the steering torque. The hysteresis basic component includes a first hysteresis basic component and a second hysteresis basic component. The first hysteresis basic component is added so that the target motor torque has a hysteresis characteristic and changes accordingly with the change of the state quantity, and the state quantity is the angle of the rotating shaft that rotates in relation to the steering of the steering wheel. The second hysteresis basic component is added so that the target motor torque has a hysteresis characteristic and changes accordingly with the change of the state quantity, and the state quantity is the steering torque.

[0133] With the above configuration, when the torque feedforward control of the steering torque is adopted in the calculation of the command value component, the situation where the command value component loses the hysteresis characteristic with the change of the state quantity can be reduced, and it helps to achieve the desired steering feeling.

[0134] The command value component calculator calculates the axial force acting on the rotating shaft included in the steering device for performing the rotation of the rotating wheel as a command value component. A hysteresis basic component is added so that the axial force has a hysteresis characteristic and changes accordingly with the change of the state quantity, and the state quantity is the angle of the rotating shaft that rotates in relation to the steering of the steering wheel.

[0135] With the above configuration, when calculating the axial force acting on the rotating shaft and adopting the calculated axial force as the command value component, a significant response can be given to the driver, and the improvement of the steering feeling can be achieved.

Claims

1. A steering controller (2) configured to control a steering device (1) which is configured to vary a steering torque for steering a steering wheel (3) by using a motor torque, the motor torque being applied by an actuator (12) using a motor (13) as a drive source, wherein the steering controller (2) is characterized by including a torque command value calculator (62) configured to calculate a torque command value serving as a target value of the motor torque, where: The steering controller (2) controls an operation of the motor (13) to generate the motor torque corresponding to the torque command value; The torque command value calculator (62) has: A command value component calculator (91) configured to calculate a command value component which is added for calculation of the torque command value, and A hysteresis component calculator (92) configured to calculate a hysteresis component which is added so that the command value component has a hysteresis characteristic and changes accordingly with a change in a state quantity, the change in the state quantity changing according to an operation of the steering device (1); The hysteresis component calculator (92) has: A hysteresis basic component calculator (111) configured to calculate a hysteresis basic component as a basic component of the hysteresis component based on the state quantity, the hysteresis basic component changing such that as the state quantity becomes larger, an absolute value of the hysteresis basic component becomes larger and an absolute value of a hysteresis gradient, which is a change amount for the state quantity, becomes smaller, and A hysteresis differential component calculator (112) configured to calculate a hysteresis differential component which is a component obtained by differentiating the hysteresis basic component; And The hysteresis component calculator (92) is configured to calculate the hysteresis component by adding the hysteresis differential component to the hysteresis basic component.

2. The steering controller (2) according to claim 1, characterized in that, The hysteresis basic component calculator (111) is configured to change the hysteresis basic component based on a change amount of an angle of a rotating shaft that rotates in relation to the steering of the steering wheel (3).

3. The steering controller (2) according to claim 1 or 2, characterized in that, The hysteresis basic component calculator (111) is configured to change the hysteresis basic component based on a vehicle speed.

4. The steering controller (2) according to claim 3, characterized in that, The hysteresis differential component calculator (112) is configured to change the hysteresis differential component based on the vehicle speed.

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