Steering control device

Abstract

This steering control device is configured to perform torque feedback processes (M40, M62, M72, M74, M80), an operation process (M30), and characteristic changing processes (M64, M66, M76, M78). The torque feedback processes include a process for calculating an operation amount for controlling a steering torque to a target steering torque through feedback control. The operation process is for operating a drive circuit of a motor on the basis of the operation amount. The characteristic changing processes are for changing response characteristics of the feedback control in accordance with the operation state of an operation member.

Description

[Technical Field]

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

[0002] For example, Patent Document 1 listed below describes a control device that controls the steering torque, which is the torque applied to the steering wheel, to a target value by feedback control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-223832 Summary of the Invention [Problem to be solved by the invention]

[0004] When performing the above-mentioned torque feedback control, the challenge is to achieve both stability and responsiveness. [Means for solving the problem]

[0005] One aspect of the present disclosure provides a steering control device configured to operate a motor mechanically coupled to an operating member operated by a driver to steer a vehicle, the steering control device being configured to execute torque feedback processing, operation processing, and characteristic change processing, the torque feedback processing including processing for calculating an operation amount for controlling a steering torque to a target steering torque by feedback control, the steering torque being a torque input to the operating member, The operation process is a process for operating a drive circuit of the motor based on the amount of operation, and the characteristic change process is a process for changing the response characteristic of the feedback control in accordance with the operation state of the operating member. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a diagram showing a configuration of a steering system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing a process executed by a control device according to the first embodiment. [Figure 3] FIG. 2 is a block diagram showing details of some processes executed by a control device according to the first embodiment. [Figure 4] Fig. 4A is a time chart showing the response characteristics of the first embodiment, and Fig. 4B is a time chart showing the response characteristics of the first embodiment and a comparative example. [Figure 5] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a second embodiment. [Figure 6] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a third embodiment. [Figure 7] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a fourth embodiment. [Figure 8] FIG. 11 is a block diagram showing details of some processes executed by a control device according to a fifth embodiment. [Figure 9] FIG. 13 is a block diagram showing details of some processes executed by a control device according to a sixth embodiment. [Figure 10] FIG. 13 is a block diagram showing details of some of the processes executed by a control device according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] First Embodiment A first embodiment of the steering control device will be described below with reference to the drawings. "Prerequisite configuration" As shown in Fig. 1, a vehicle steering system 10 includes a reaction force actuator Ar and a turning actuator At. The steering system 10 of this embodiment has a structure in which the power transmission path between the steering wheel 12 and the steered wheels 44 is mechanically disconnected. In other words, the steering system 10 includes a steer-by-wire type steering device.

[0008] A steering shaft 14 is connected to the steering wheel 12. The reaction force actuator Ar is an actuator for applying a steering reaction force to the steering wheel 12. The steering reaction force is a force that acts in the opposite direction to the direction of operation of the steering wheel 12 by the driver. By applying the steering reaction force to the steering wheel 12, it is possible to give the driver an appropriate sense of responsiveness. The reaction force actuator Ar includes a reduction mechanism 16, a reaction force motor 20, and a reaction force inverter 22.

[0009] The reaction motor 20 is a three-phase brushless motor. The reaction motor 20 is a surface permanent magnet synchronous motor. The rotating shaft of the reaction motor 20 is connected to the steering shaft 14 via a reduction gear mechanism 16. The reaction inverter 22 is a power conversion circuit that converts the voltage of a battery 24, which is a DC voltage source, into AC voltage and applies it to the reaction motor 20.

[0010] Meanwhile, steering shaft 40 extends along the vehicle width direction, which is the left-right direction in Figure 1. Left and right steered wheels 44 are connected to both ends of steering shaft 40 via tie rods 42. The linear movement of steering shaft 40 changes the steering angle of steered wheels 44.

[0011] Steering actuator At includes speed reduction mechanism 56, steering motor 60, and steering inverter 62. Steering motor 60 is a three-phase brushless motor. The rotating shaft of steering motor 60 is connected to pinion shaft 52 via speed reduction mechanism 56. Pinion teeth of pinion shaft 52 mesh with rack teeth 54 of steering shaft 40. A rack-and-pinion mechanism is formed by pinion shaft 52 and steering shaft 40 provided with rack teeth 54. The torque of steering motor 60 is applied as a steering force to steering shaft 40 via pinion shaft 52. In response to the rotation of steering motor 60, steering shaft 40 moves along the vehicle width direction, which is the left-right direction in FIG. 1 .

[0012] The steering system 10 includes a control device 70 . The control object of control device 70 is the steering device. More specifically, the control object of control device 70 is steering wheel 12 of the steering device. Control device 70 operates reaction force actuator Ar to control the steering reaction force, which is the control variable of the control object. Fig. 1 shows an operation signal MSs to reaction force inverter 22. Furthermore, control device 70 operates steered wheels 44 of the steering device as the control object. Control device 70 operates steering actuator At to control the steering angle of steered wheels 44, which is the control variable of the control object. The steering angle is the turning angle of the tires. Fig. 1 shows an operation signal MSt to steering inverter 62.

[0013] In order to control the controlled variable, control device 70 refers to steering torque Th, which is input torque to steering shaft 14, detected by torque sensor 80. Torque sensor 80 includes a torsion bar connected to steering shaft 14 and a sensing element that detects the torsion angle of the torsion bar. Control device 70 also refers to rotation angle θa of the rotary shaft of reaction force motor 20, detected by rotation angle sensor 82. Control device 70 also refers to currents iu1, iv1, iw1 that flow through reaction force motor 20. Currents iu1, iv1, iw1 are quantified as voltage drops across shunt resistors provided in each leg of reaction force inverter 22. Control device 70 also refers to rotation angle θb of the rotary shaft of turning motor 60, detected by rotation angle sensor 84, in order to control the controlled variable. Control device 70 also refers to currents iu2, iv2, iw2 that flow through turning motor 60. The currents iu2, iv2, and iw2 are quantified as the amount of voltage drop across a shunt resistor provided in each leg of the steering inverter 62. The control device 70 also refers to the vehicle speed V detected by the vehicle speed sensor 86.

[0014] The control device 70 includes a PU 72, a storage device 74, and peripheral circuits 76. The PU 72 is a software processing device such as a CPU, a GPU, and a TPU. The storage device 74 includes a storage medium such as an electrically rewritable nonvolatile memory and a disk medium. A steering control program 74a is stored in the storage device 74. The peripheral circuits 76 include a circuit that generates a clock signal that regulates internal operations, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control amount by having the PU 72 execute the steering control program 74a stored in the storage device 74.

[0015] "control" FIG. 2 shows part of the processing executed by the control device 70. The steering angle calculation process M10 is a process that uses the rotation angle θa as an input and calculates the steering angle θh, which is the rotation angle of the steering wheel 12. The steering angle calculation process M10 includes a process that converts the rotation angle θa into an integrated angle that includes a range exceeding 360°, for example, by counting the number of rotations of the reaction force motor 20 from a steering neutral position, which is the position of the steering wheel 12 when the vehicle is traveling straight. The steering angle calculation process M10 includes a process that calculates the steering angle θh by multiplying the integrated angle obtained by conversion by a conversion coefficient based on the rotational speed ratio of the speed reduction mechanism 16. Note that the steering angle θh is positive when it is an angle to the right of the steering neutral position, and negative when it is an angle to the left of the steering neutral position, for example.

[0016] Pinion angle calculation process M12 is a process that uses rotation angle θb as an input and calculates pinion angle θp, which is the rotation angle of pinion shaft 52. Pinion angle calculation process M12 includes, for example, a process of counting the number of rotations of steering motor 60 from a rack neutral position, which is the position of steering shaft 40 when the vehicle is traveling straight, and converting the counted number of rotations into an integrated angle that includes a range exceeding 360°. Pinion angle calculation process M12 includes a process of multiplying the converted integrated angle by a conversion coefficient based on the rotational speed ratio of speed reduction mechanism 56 to calculate pinion angle θp, which is the actual rotation angle of pinion shaft 52. Note that pinion angle θp is positive when it is an angle to the right of the rack neutral position, and negative when it is an angle to the left of the rack neutral position, for example. Steering motor 60 and pinion shaft 52 are linked via speed reduction mechanism 56. Therefore, there is a one-to-one correspondence between the integrated value of rotation angle θb of steering motor 60 and pinion angle θp. Using this correspondence, pinion angle θp can be found from rotation angle θb of steering motor 60. Furthermore, pinion shaft 52 is meshed with steered shaft 40. Therefore, there is also a one-to-one correspondence between pinion angle θp and the amount of movement of steered shaft 40. And there is also a one-to-one correspondence between pinion angle θp and the steering angle of steered wheels 44.

[0017] The target pinion angle calculation process M14 is a process that calculates a target pinion angle θp* using the steering angle θh and the vehicle speed V as inputs. The target pinion angle θp* is a target value of the pinion angle θp according to the operation of the steering wheel 12 by the driver. The target pinion angle calculation process M14 includes a process that variably sets the steering angle ratio Dr according to the vehicle speed V. Therefore, the target pinion angle θp* output by the target pinion angle calculation process M14 will be a different value depending on the vehicle speed V even if the input steering angle θh is the same.

[0018] The pinion angle feedback process M16 is a process for calculating a steering torque command value Tt*, which is a command value for the torque of the steering motor 60, in order to control the pinion angle θp to the target pinion angle θp* by feedback control.

[0019] The steering operation process M18 is a process that receives as input the steering torque command value Tt*, currents iu2, iv2, iw2, and rotation angle θb, and outputs an operation signal MSt for the steering inverter 62. The steering operation process M18 includes a process that calculates current command values ​​for the dq axes based on the steering torque command value Tt*. The steering operation process M18 also includes a process that calculates currents for the dq axes based on the currents iu2, iv2, iw2 and the rotation angle θb. The steering operation process M18 then includes a process that calculates an operation signal MSt for operating the steering inverter 62 so that the currents for the dq axes become the command values.

[0020] The axial force calculation process M19 includes a process of calculating the axial force Taf using the turning torque command value Tt* as an input. Here, the axial force Taf is the force applied to the turning shaft 40 in the axial direction. The base target torque calculation process M20 is a process for calculating a base target torque Thb*, which is a base value of a target steering torque Th* that the driver should input to the steering shaft 14 via the steering wheel 12, based on the axial force Taf. Here, the axial force Taf is an axial force applied to the steered shaft 40. The axial force Taf is an amount that depends on the lateral force acting on the steered wheels 44, and therefore the lateral force can be determined from the axial force Taf. On the other hand, it is desirable to determine the torque that the driver should input to the steering shaft 14 via the steering wheel 12 depending on the lateral force. Therefore, the base target torque calculation process M20 is a process for calculating the base target torque Thb* depending on the lateral force determined from the axial force Taf.

[0021] In more detail, the base target torque calculation process M20 is a process for variably setting the absolute value of the base target torque Thb* in accordance with the vehicle speed V even when the absolute value of the axial force Taf is the same. This process may be a process for calculating the absolute value of the base target torque Thb* when the vehicle speed V is small so that it is equal to or less than the absolute value of the base target torque Thb* when the vehicle speed V is large. This can be realized, for example, by having the PU 72 perform map calculations of the base target torque Thb* in a state where map data is stored in advance in the storage device 74. This map data is data in which the axial force Taf or the lateral acceleration determined from the axial force Taf and the vehicle speed V are input variables, and the base target torque Thb* is an output variable.

[0022] Map data is a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. Furthermore, the map calculation may be a process in which, when the value of an input variable matches one of the input variable values ​​in the map data, the value of the corresponding output variable in the map data is used as the calculation result. Furthermore, when the value of an input variable does not match any of the input variable values ​​in the map data, the map calculation may be a process in which the value obtained by interpolating the values ​​of multiple output variables included in the map data is used as the calculation result. Alternatively, when the value of an input variable does not match any of the input variable values ​​in the map data, the map calculation may be a process in which the value of the output variable in the map data that corresponds to the closest value among the multiple output variable values ​​included in the map data is used as the calculation result.

[0023] The hysteresis processing M22 is a processing for calculating and outputting a hysteresis correction amount Thys for correcting the base target torque Thb* based on the steering angle θh. More specifically, the hysteresis processing M22 includes a processing for distinguishing between when the steering wheel 12 is being turned and when it is being turned back based on changes in the steering angle θh, etc., and calculating the hysteresis correction amount Thys. More specifically, the hysteresis processing M22 includes a processing for calculating the hysteresis correction amount Thys so that the absolute value of the target steering torque Th* is larger when the steering wheel 12 is being turned back than when it is being turned back. The hysteresis processing M22 includes a processing for variably setting the hysteresis correction amount Thys according to the vehicle speed V.

[0024] The addition process M24 is a process for calculating the target steering torque Th* by adding the hysteresis correction amount Thys to the base target torque Thb*. The target reaction force calculation process M26 is a process that uses the steering torque Th and the target steering torque Th* as inputs to calculate a target reaction force Ts* corresponding to the steering reaction force to be applied to the steering wheel 12. The target reaction force Ts* is actually a command value for the reaction force motor 20. The value obtained by multiplying the target reaction force Ts* by a coefficient corresponding to the reduction ratio of the reduction mechanism 16 becomes the steering reaction force.

[0025] The reaction force operation process M30 is a process that receives the target reaction force Ts*, currents iu1, iv1, iw1, and rotation angle θa as inputs and outputs an operation signal MSs for the reaction force inverter 22. The reaction force operation process M30 includes a process of calculating a dq-axis current command value based on the target reaction force Ts*. The reaction force operation process M30 also includes a process of calculating a dq-axis current based on the currents iu1, iv1, iw1 and the rotation angle θa. The reaction force operation process M30 then includes a process of calculating an operation signal MSs for operating the reaction force inverter 22 so that the dq-axis current becomes the command value.

[0026] FIG. 3 shows the details of the target reaction force calculation process M26. The deviation calculation process M40 is a process for calculating a torque deviation ΔTh, which is a value obtained by subtracting the target steering torque Th* from the steering torque Th.

[0027] The operation state identification process M50 is a process for identifying the operation state of the steering wheel 12. The operation state identification process M50 includes a linear operator M52 and a multiplication process M54. The linear operator M52 is a process for calculating and outputting a first-order time differential value of the steering angle θh. The multiplication process M54 is a process for multiplying the steering angle θh by the output value of the linear operator M52 and assigning the result to the state identification variable Sc. In a first operation state in which the steering wheel 12 is operated away from the neutral position, the sign of the steering angle θh and the sign of the first-order time differential value of the steering angle θh are the same. Therefore, the state identification variable Sc is positive in the first operation state. In contrast, in a second operation state in which the steering wheel 12 is operated toward the neutral position, the sign of the steering angle θh and the sign of the first-order time differential value of the steering angle θh are opposite. Therefore, the state identification variable Sc is negative in the second operation state.

[0028] The proportional element M60 is a process that receives the torque deviation ΔTh as input and outputs a value proportional to the torque deviation ΔTh. More specifically, the proportional gain multiplication process M62 is a process that multiplies the torque deviation ΔTh by the proportional gain Kp. The proportional variable gain calculation process M64 is a process that receives the value of the state identification variable Sc as input and calculates the proportional variable gain Gp. The proportional variable gain calculation process M64 sets the proportional variable gain Gp when the value of the state identification variable Sc is large to be equal to or greater than the proportional variable gain Gp when the value of the state identification variable Sc is small. This process may be, for example, a process in which the PU 72 calculates the proportional variable gain Gp using a map while map data is stored in the storage device 74. Here, the map data is data that uses the value of the state identification variable Sc as an input variable and the value of the proportional variable gain Gp as an output variable.

[0029] Specifically, the proportional variable gain Gp has different constant values ​​when the value of the state identification variable Sc is equal to or less than the first threshold value Sc1 and when the value is equal to or greater than the second threshold value Sc2. Furthermore, when the value of the state identification variable Sc is greater than the first threshold value Sc1 and less than the second threshold value Sc2, the proportional variable gain Gp has a value that monotonically increases according to the value of the state identification variable Sc.

[0030] Proportional variable gain multiplication processing M66 is processing that multiplies the output value of proportional gain multiplication processing M62 by proportional variable gain Gp. The output value of proportional variable gain multiplication processing M66 is the output value of proportional element M60. In other words, the gain of proportional element M60 is the value obtained by multiplying proportional gain Kp by proportional variable gain Gp.

[0031] The differential element M70 receives the torque deviation ΔTh as input and outputs a value proportional to the first-order time differential of the torque deviation ΔTh. Specifically, the linear operator M72 calculates the first-order time differential of the torque deviation ΔTh. The differential gain multiplication M74 multiplies the output value of the linear operator M72 by a differential gain Kd. The differential variable gain calculation M76 receives the value of the state identification variable Sc as input and calculates the differential variable gain Gd. The differential variable gain calculation M76 sets the differential variable gain Gd when the value of the state identification variable Sc is large to be equal to or greater than the differential variable gain Gd when the value of the state identification variable Sc is small. This process may be, for example, a process in which the PU 72 calculates the differential variable gain Gd using a map while map data is stored in the storage device 74. Here, the map data is data in which the value of the state identification variable Sc is an input variable and the value of the differential variable gain Gd is an output variable.

[0032] Specifically, the derivative variable gain Gd has different constant values ​​when the value of the state identification variable Sc is equal to or less than the third threshold Sc3 and when it is equal to or greater than the fourth threshold Sc4. Furthermore, when the value of the state identification variable Sc is greater than the third threshold Sc3 but less than the fourth threshold Sc4, the derivative variable gain Gd has a value that monotonically increases in accordance with the value of the state identification variable Sc. The first threshold Sc1 and the third threshold Sc3 may be the same. The second threshold Sc2 and the fourth threshold Sc4 may be the same.

[0033] The differential variable gain multiplication process M78 multiplies the output value of the differential gain multiplication process M74 by the differential variable gain Gd. The output value of the differential variable gain multiplication process M78 is the output value of the differential element M70. In other words, the product of the differential gain Kd and the differential variable gain Gd becomes the gain of the differential element M70.

[0034] The addition process M80 is a process of adding the output value of the proportional element M60 and the output value of the derivative element M70 and outputting the resulting sum as the PD manipulated variable Tpd. The second operation amount calculation process M90 is a process for calculating an operation amount other than the PD operation amount Tpd for controlling the steering torque Th to the target steering torque Th*. The second operation amount calculation process M90 may include, for example, at least one of the processes (A) to (H) described below.

[0035] Process (A) is a process for calculating an operation amount corresponding to an integrated value of the value obtained by subtracting the steering torque Th from the estimated axial force. The estimated axial force is a value equivalent to the torque of the reaction force motor 20. The estimated axial force is a value calculated by the PU 72 by inputting the currents iu1, iv1, and iw1.

[0036] The process (B) is a process in which the integrated value of the difference between the steering torque Th and the target steering torque Th* multiplied by the integral gain is used as the operation amount. The process (C) is a process for calculating the amount of operation for controlling the steering torque estimated by the disturbance observer to the target steering torque Th*. The process (C) receives the steering angle θh, the torque of the reaction motor 20 calculated from the currents iu1, iv1, and iw1, and the like as inputs.

[0037] The process (D) is a process for calculating an open-loop operation amount using the steering torque Th as an input. The process (E) is a process for calculating an open-loop operation amount using the target steering torque Th* as an input.

[0038] The process (F) is a process for calculating an operation amount for applying a force to the steering shaft 14 to resist further increase in the magnitude of the pinion angle θp when the magnitude of the pinion angle θp becomes equal to or greater than a predetermined value.

[0039] The process (G) is a process for calculating an operation amount for applying a force to the steering shaft 14 to resist further increase in the magnitude of the steering angle θh when the magnitude of the steering angle θh becomes equal to or greater than a predetermined value.

[0040] The process (H) is a process for calculating an operation amount for controlling the steering angle θh to a converted steering angle obtained by converting the pinion angle θp into the steering angle θh through feedback control. The converted steering angle is calculated by the PU 72 based on the steering angle ratio and the pinion angle θp that are determined in the target pinion angle calculation process M14 according to the vehicle speed V.

[0041] The addition process M92 is a process for calculating the target reaction force Ts* by adding the PD operation amount Tpd and the second operation amount Ts2 output by the second operation amount calculation process M90. <Actions and Effects of This Embodiment> 4A and 4B illustrate control of steering torque Th in this embodiment and a comparative example. In FIGS. 4A and 4B, the solid line indicates the transition of steering torque Th. In FIG. 4, the dashed-dotted line indicates the transition of target steering torque Th*. FIG. 4A shows the transition of steering torque Th and target steering torque Th* according to this embodiment. FIG. 4B shows the transition of steering torque Th and target steering torque Th* in a comparative example. The comparative example is an example in which, in the processing of FIG. 3, the output value of proportional gain multiplication processing M62 is used as the output value of proportional element M60, and the output value of differential gain multiplication processing M74 is used as the output value of differential element M70. In addition, in FIGS. 4A and 4B, when the steering wheel 12 is operated away from the neutral position, it is referred to as "turning," and when the steering wheel 12 is operated toward the neutral position, it is referred to as "returning."

[0042] 4B, in the comparative example, the steering torque Th oscillates when the vehicle is turned back. That is, in the comparative example, the control of the steering torque Th is more unstable when the vehicle is turned back than when the vehicle is turned forward. Here, if the proportional gain Kp and the derivative gain Kd are reduced in order to suppress the instability when the vehicle is turned back, the responsiveness decreases.

[0043] Therefore, the PU 72 distinguishes between turning and turning back depending on the value of the state identification variable Sc. The PU 72 then reduces the proportional variable gain Gp and the derivative variable gain Gd when turning back compared to when turning. This makes it possible to prevent the control of the steering torque Th from becoming unstable when turning back. Furthermore, it is possible to maintain high responsiveness when turning.

[0044] Therefore, according to this embodiment, a good compromise can be achieved between stability and responsiveness of the feedback control of the steering torque Th. According to the present embodiment described above, the following actions and effects can be further obtained.

[0045] (1-1) The state identification variable Sc is configured by the product of the steering angle θh and the steering angular velocity. As a result, the state identification variable Sc is positive when turning the steering wheel, and negative when turning the steering wheel. Therefore, the state identification variable Sc can be a variable whose sign changes depending on whether the steering wheel is turning or turning.

[0046] (1-2) The state identification variable Sc is a variable that can take on values ​​of different magnitudes even if the value has the same sign. This allows the gain of the proportional element M60 and the gain of the derivative element M70 to be monotonically increased according to the value of the state identification variable Sc, even if the sign of the state identification variable Sc is the same. This makes it possible to suppress sudden changes in the gain.

[0047] (1-3) The gains are changed in response to turning and turning back using both the proportional element M60 and the differential element M70. This increases the degree of freedom in designing the feedback control of the steering torque Th, making it possible to set a more appropriate value that achieves both stability and responsiveness compared to when only one of the elements is variable.

[0048] (1-4) The PU 72 operated the reaction force inverter 22 while the steering wheel 12 and the steered wheels 44 were mechanically separated. In other words, the control of FIG. 3 was adopted in a steer-by-wire steering device. Even if a controller does not generate vibrations in a system in which the steering wheel 12 and the steered wheels 44 are mechanically connected, vibrations may occur in a steer-by-wire steering device. Therefore, the control of FIG. 3 is particularly useful.

[0049] It is presumed that vibrations are likely to occur in a steer-by-wire steering device because the load applied to the steering wheel 12 is small when the magnitude of the steering torque Th is large enough to overcome the friction component. In other words, when the steering wheel 12 and the steered wheels 44 are mechanically connected, the load torque from the steered wheels 44 is applied to the steering wheel 12. It is presumed that this load torque tends to suppress the occurrence of vibrations.

[0050] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0051] Fig. 5 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 5, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals. 5, in the present embodiment, in the operation state identification process M50, the multiplication process M54 multiplies the steering torque Th by the steering angular velocity, which is the output value of the linear operator M52. In the present embodiment, the output value of the multiplication process M54 is the state identification variable Sc.

[0052] <Actions and Effects of the Second Embodiment> The PU 72 substitutes the product of the steering angular velocity and the steering torque Th for the state identification variable Sc. Here, when turning the wheel, the sign of the steering angular velocity and the sign of the steering torque Th are the same. Therefore, when turning the wheel, the sign of the state identification variable Sc is positive. On the other hand, when turning the wheel back, the steering torque Th is usually applied so as to brake the steering wheel 12 from returning to the neutral position. Therefore, when turning the wheel back, the sign of the steering angular velocity and the sign of the steering torque Th are opposite. Therefore, when turning the wheel back, the sign of the state identification variable Sc is negative. Therefore, according to this embodiment, it is possible to distinguish between turning the wheel and turning the wheel back by the sign of the state identification variable Sc.

[0053] According to the present embodiment described above, it is possible to obtain the effects (1-2) and (1-3) of the first embodiment. <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0054] Fig. 6 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 6, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals. 6, in this embodiment, the operation state identification process M50 includes a conversion coefficient multiplication process M56, an addition process M57, and an absolute value calculation process M58. The conversion coefficient multiplication process M56 is a process for converting the q-axis current iq1 into the torque that the reaction force motor 20 applies to the steering shaft 14. The q-axis current iq1 is the q-axis component of the current that flows through the reaction force motor 20. The q-axis current iq1 is calculated by the PU 72 based on the currents iu1, iv1, and iw1.

[0055] The addition process M57 is a process for adding the output value of the conversion coefficient multiplication process M56 and the steering torque Th. The absolute value calculation process M58 is a process for calculating the absolute value of the output value of the addition process M57. The output value of the absolute value calculation process M58 is the value of the state identification variable Sc.

[0056] The proportional variable gain calculation process M64 of the proportional element M60 sets the proportional variable gain Gp when the value of the state identification variable Sc is large to be equal to or smaller than the value of the proportional variable gain Gp when the value of the state identification variable Sc is small. This process may be, for example, a process in which the proportional variable gain Gp is ​​calculated using a map by the PU 72 with map data stored in the storage device 74. Here, the map data is data in which the value of the state identification variable Sc is an input variable and the value of the proportional variable gain Gp is ​​an output variable.

[0057] Specifically, the proportional variable gain Gp has different constant values ​​when the value of the state identification variable Sc is equal to or less than the fifth threshold Sc5 and when the value of the state identification variable Sc is equal to or greater than the sixth threshold Sc6. Furthermore, when the proportional variable gain Gp is ​​greater than the fifth threshold Sc5 but less than the sixth threshold Sc6, it has a value that monotonically decreases according to the value of the state identification variable Sc.

[0058] The differential variable gain calculation process M76 is a process for setting the differential variable gain Gd when the value of the state identification variable Sc is large to be equal to or smaller than the differential variable gain Gd when the value of the state identification variable Sc is small. This process may be, for example, a process in which the differential variable gain Gd is calculated using a map by the PU 72 with map data stored in the storage device 74. Here, the map data is data in which the value of the state identification variable Sc is an input variable and the value of the differential variable gain Gd is an output variable.

[0059] Specifically, the derivative variable gain Gd has different constant values ​​when the value of the state identification variable Sc is equal to or less than the seventh threshold Sc7 and when the value is equal to or greater than the eighth threshold Sc8. Furthermore, when the value of the state identification variable Sc is greater than the seventh threshold Sc7 but less than the eighth threshold Sc8, the derivative variable gain Gd has a value that monotonically increases according to the value of the state identification variable Sc. Note that the fifth threshold Sc5 and the seventh threshold Sc7 may be the same. Furthermore, the sixth threshold Sc6 and the eighth threshold Sc8 may be the same.

[0060] <Actions and Effects of the Third Embodiment> The PU 72 sets the value of the state identification variable Sc to be the absolute value of the sum of the torque applied to the steering shaft 14 by the reaction force motor 20 and the steering torque Th. Therefore, when the torque applied to the steering shaft 14 by the reaction force motor 20 and the steering torque Th are approximately equal in magnitude, the value of the state identification variable Sc is close to zero. On the other hand, when the driver largely displaces the steering wheel 12, the steering torque Th becomes larger than the torque applied to the steering shaft 14 by a certain value or more. Therefore, the value of the state identification variable Sc becomes larger than zero by a certain value or more.

[0061] A state in which the steering torque Th is greater than the torque applied to the steering shaft 14 by the reaction force motor 20 by a certain value or more corresponds to a state in which the steering torque Th has overcome the friction applied to the steering shaft 14. In other words, this corresponds to a state in which the degree of influence of friction is small. In this state in which friction has been overcome, feedback control of the steering torque Th is likely to become unstable. Therefore, when the value of the state identification variable Sc increases, the PU 72 reduces the gain of the proportional element M60 and the gain of the derivative element M70. This ensures stability in this state in which friction has been overcome. Furthermore, in a state before friction has been overcome, the gain of the proportional element M60 and the gain of the derivative element M70 are increased. In other words, when the degree of influence of friction is large, the gain of the proportional element M60 and the gain of the derivative element M70 are increased. This improves responsiveness in this state in which the degree of influence of friction is large.

[0062] Therefore, in this embodiment, a good compromise can be achieved between stability and responsiveness of the feedback control of the steering torque Th. According to the present embodiment described above, in addition to the effect similar to the effect (1-3) above, the following actions and effects can be further obtained.

[0063] (3-1) The value of the state identification variable Sc is a variable that can take three or more values. This allows the gain of the proportional element M60 and the gain of the derivative element M70 to be monotonically decreased according to the value of the state identification variable Sc. This makes it possible to suppress sudden changes in the gain.

[0064] <Fourth embodiment> The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0065] Fig. 7 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 7, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals. As shown in Fig. 7, the proportional element M60 includes a proportional phase controller M100 and a proportional characteristic varying process M102. The proportional phase controller M100 performs low-pass filtering on the output value of the proportional gain multiplication process M62. More specifically, the proportional phase controller M100 is a first-order lag filter as described below.

[0066] 1 / (Tp s+1) Note that "Tp" is a time constant and "s" is a linear operator indicating first-order time differentiation. The output value of the proportional phase controller M100 is the output value of the proportional element M60.

[0067] The proportional characteristic varying process M102 is a process for varying the characteristic of the proportional phase controller M100 in accordance with the value of the state identification variable Sc. More specifically, the proportional characteristic varying process M102 varies the cutoff frequency fc of the proportional phase controller M100 in accordance with the value of the state identification variable Sc. This process may be, for example, a process in which the PU 72 calculates the time constant Tp using a map while map data is stored in the storage device 74. Here, the map data is data in which the value of the state identification variable Sc is an input variable and the value of the time constant Tp is an output variable.

[0068] Specifically, the cutoff frequency fc is a constant value that is different when the value of the state identification variable Sc is equal to or less than the first threshold value Sc1 and when the value of the state identification variable Sc is equal to or greater than the second threshold value Sc2. Furthermore, when the cutoff frequency fc is greater than the first threshold value Sc1 and less than the second threshold value Sc2, the cutoff frequency fc is a value that monotonically decreases according to the value of the state identification variable Sc.

[0069] The differential element M70 includes a differential phase controller M110 and a differential characteristic variable process M112. The differential phase controller M110 is a process that advances or delays the phase of a predetermined frequency component of the output value of the differential gain multiplication process M74. The differential phase controller M110 is a phase controller with zero order difference as shown below.

[0070] {ad Td s+1} / (Td s+1) Here, "Td" is a time constant. If "ad>1", the phase of a predetermined frequency component can be advanced.

[0071] The differential characteristic varying process M112 is a process for varying the characteristics of the differential phase controller M110 in accordance with the value of the state identification variable Sc. More specifically, the differential characteristic varying process M112 varies the predetermined frequency component in accordance with the value of the state identification variable Sc. This process may be, for example, a process in which the PU 72 performs map calculations on the time constant Td or the variable ad with map data stored in the storage device 74. Here, the map data is data in which the value of the state identification variable Sc is used as an input variable and the value of the time constant Td or the variable ad is used as an output variable.

[0072] <Actions and Effects of the Fourth Embodiment> When the value of the state identification variable Sc decreases, the PU 72 increases the cutoff frequency fc in the proportional element M60. This reduces responsiveness and ensures stability when turning. Also, when the value of the state identification variable Sc increases, the PU 72 decreases the cutoff frequency fc. This improves responsiveness when turning.

[0073] Therefore, in this embodiment, a good compromise between stability and responsiveness of the feedback control of the steering torque Th can be achieved. According to the present embodiment described above, in addition to the effect similar to the effect (1-1) above, the following actions and effects can be further obtained.

[0074] (4-1) The characteristics of the frequency controller are changed in response to turning and turning back, using both the proportional element M60 and the differential element M70. This increases the degree of freedom in the design of the feedback control of the steering torque Th, making it possible to set it more appropriately to achieve both stability and responsiveness, compared to when only one of the elements is variable.

[0075] Fifth Embodiment The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the fourth embodiment.

[0076] Fig. 8 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 8, the processes corresponding to those shown in Fig. 7 are denoted by the same reference numerals. As shown in FIG. 8, in this embodiment, the operation state identification process M50 in the process shown in FIG. 7 is replaced with the process shown in FIG.

[0077] Sixth Embodiment The sixth embodiment will be described below with reference to the drawings, focusing on the differences from the fourth embodiment.

[0078] Fig. 9 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 9, the processes corresponding to those shown in Fig. 7 are denoted by the same reference numerals. As shown in FIG. 9, in this embodiment, the operation state identification process M50 in the process shown in FIG. 7 is replaced with the process shown in FIG. 6. Furthermore, the proportional characteristic varying process M102 is a process for setting the value of the cutoff frequency fc when the value of the state identification variable Sc is large to be equal to or greater than the value of the cutoff frequency fc when the value of the state identification variable Sc is small. In other words, the cutoff frequency fc when the degree of influence of friction is large is set to be smaller than the cutoff frequency fc when the degree of influence of friction is small. Specifically, the cutoff frequency fc is set to different constant values ​​when the value of the state identification variable Sc is equal to or less than the fifth threshold Sc5 and when the value of the state identification variable Sc is equal to or greater than the sixth threshold Sc6. Furthermore, when the cutoff frequency fc is greater than the fifth threshold Sc5 and less than the sixth threshold Sc6, it is set to a value that monotonically increases according to the value of the state identification variable Sc.

[0079] Seventh Embodiment The seventh embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0080] Fig. 10 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 10, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals.

[0081] As shown in Fig. 10, in this embodiment, the input of the derivative element M70 is the steering torque Th. Therefore, the linear operator M72 is a process for calculating a first-order time derivative of the steering torque Th. Furthermore, the derivative gain multiplication process M74 is a process for multiplying the first-order time derivative of the steering torque Th by a derivative gain Kd. Furthermore, the PD operation amount Tpd is a value obtained by subtracting the output value of the derivative element M70 from the output value of the proportional element M60 in the subtraction process M80a.

[0082] In this way, the PD manipulated variable Tpd according to this embodiment is a manipulated variable of the advanced differential type PD control. <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0083] "About proportional elements" The proportional variable gain multiplication process M66 may be provided upstream of the proportional gain multiplication process M62. In other words, the torque deviation ΔTh may be multiplied by the proportional variable gain Gp.

[0084] For example, the proportional phase controller M100 may be provided upstream of the proportional gain multiplication process M62. The proportional element M60 may include the proportional phase controller M100 but may not include the proportional characteristic varying process M102.

[0085] "About differential elements" The differential variable gain multiplication process M78 may be provided upstream of the differential gain multiplication process M74. In other words, the output value of the linear operator M72 may be multiplied by the differential variable gain Gd. Also, for example, the differential variable gain multiplication process M78 may be provided upstream of the linear operator M72. In other words, the torque deviation ΔTh may be multiplied by the differential variable gain Gd.

[0086] For example, the differential phase controller M110 may be provided between the linear operator M72 and the differential gain multiplication process M74. Also, for example, the differential phase controller M110 may be provided upstream of the linear operator M72.

[0087] The differential element M70 may include the differential phase controller M110, but may not include the differential characteristic varying process M112. About Filtering (a) Proportional phase controller The proportional phase controller is not limited to a first-order lag element. For example, it may be a second-order lag element. It may also be a phase controller with a relative order of 0, as shown below.

[0088] αp·(Tp2·s+1) / (Tp1·s+1) However, "αp<1". (b) Differential phase controller M110 The differential phase controller is not limited to the one exemplified in the above embodiment.

[0089] (c) Other It is not essential to provide a phase controller for both the proportional element M60 and the differential element M70. For example, a controller that adjusts the phase of the output value of the addition process M80 or the phase of the output value of the subtraction process M80a may be used.

[0090] "The degree of influence of friction on the displacement of the operating member" The input variables for quantifying the degree of influence of friction on the displacement of the operating member are not limited to the methods exemplified in the above embodiment. For example, if the reaction motor 20 is an interior permanent magnet synchronous motor, the torque estimated from both the q-axis current iq1 and the d-axis current id1 may be used as the torque variable. Furthermore, the torque command value for the reaction motor 20 may be used as the torque variable.

[0091] For example, as described in the section "Regarding the Steering Device" below, in the case of a steering device in which the steering wheel 12 and the steerable wheels 44 are mechanically coupled, the following may be done: That is, a variable indicating the degree of influence of friction may be constructed from the absolute value of the sum of the torque of the motor that steers the steerable wheels 44 and the steering torque Th.

[0092] The variable that quantifies the degree of influence of friction on the displacement of the operating member is not limited to one that can take three or more values. For example, the state identification variable Sc may be a binary variable that indicates whether the output value of the absolute value calculation process M58 is equal to or greater than a threshold value.

[0093] "About characteristic change processing" (a) Changes to the proportional element M60 The magnitude relationship of the gain of the proportional element M60 for the first operation state and the second operation state is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0094] The magnitude relationship between the cutoff frequency fc of the proportional phase controller M100 for the first operation state and the second operation state is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0095] The magnitude relationship of the gain of the proportional element M60 when the degree of influence of friction is large and when it is small is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0096] The magnitude relationship between the cutoff frequency fc of the proportional phase controller M100 when the degree of influence of friction is large and when it is small is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0097] The gain of the proportional element M60 may be changed by the proportional variable gain Gp, and the frequency characteristics of the proportional phase controller M100 may be changed. (b) Changes to differential element M70 The magnitude relationship of the gain of the derivative element M70 for the first operation state and the second operation state is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0098] The magnitude relationship of the gain of the differential element M70 when the degree of influence of friction is large and when it is small is not limited to the setting exemplified in the above embodiment. For example, it may be reversed depending on the characteristics of the steering device.

[0099] The gain of the differential element M70 may be changed by the differential variable gain Gd, and the frequency characteristics of the differential phase controller M110 may be changed. (c) Other The process of changing the gain of the proportional element M60 using the proportional variable gain Gp does not necessarily require the process of changing the gain of the derivative element M70 using the derivative variable gain Gd. That is, for example, while the process of changing the gain of the proportional element M60 using the proportional variable gain Gp is ​​executed, the process of changing the gain of the derivative element M70 using the derivative variable gain Gd may not be executed.

[0100] The process of changing the frequency characteristics of the proportional phase controller M100 does not necessarily require the process of changing the frequency characteristics of the differential phase controller M110. That is, for example, it is possible to execute the process of changing the frequency characteristics of the proportional phase controller M100 without executing the process of changing the frequency characteristics of the differential phase controller M110.

[0101] The process of changing the responsiveness of the feedback control in accordance with the value of the state identification variable Sc is not limited to the process of adjusting the PD manipulated variable Tpd. For example, it may be a process of adjusting the output value of an integral element that outputs an integrated value of a value obtained by multiplying the torque deviation ΔTh by a gain. In this case, the gain of the integral element may be variably set in accordance with the state identification variable Sc. Also, for example, the output value of a phase controller to which the integrated value is input may be used as the output value of the integral element, and the characteristics of the phase controller may be adjusted in accordance with the value of the state identification variable Sc. Also, for example, both the gain and the characteristics of the phase controller may be adjusted in accordance with the state identification variable Sc.

[0102] (d) Methods for quantifying operational status Instead of using the state identification variable Sc as the product of the steering angle θh and the steering angular velocity, it may be a binary variable depending on the sign of the product of the steering angle θh and the steering angular velocity.

[0103] Instead of using the state identification variable Sc as the product of the steering torque Th and the steering angular velocity, it may be a binary variable depending on the sign of the product of the steering torque Th and the steering angular velocity. The displacement amount of the steering wheel 12, which is an operating member, is not limited to an amount calculated based on an integration process of the rotation angle θa. For example, it may be a value detected by a steering angle sensor that directly detects the rotation angle of the steering shaft 14. Note that the steering angle sensor may be provided, for example, closer to the steering wheel 12 than the torque sensor 80.

[0104] "Regarding the amount of control required to control the steering torque to the target steering torque" The manipulated variable for controlling the steering torque to the target steering torque is not limited to the target reaction force Ts*. In other words, it is not limited to the target value of the torque for the reaction force motor 20. For example, if the reaction force motor 20 is a surface permanent magnet synchronous motor, it may be a command value for the q-axis current. Also, if the reaction force motor 20 is an interior permanent magnet synchronous motor, it may be a set of command values ​​for the d-axis current and the q-axis current.

[0105] The operation amount for controlling the steering torque to the target steering torque is not limited to a variable indicating the reaction force applied to the steering wheel 12. For example, as described in the section "About the steering system" below, in the case of a device capable of transmitting power between the steering wheel 12 and the steered wheels 44, the operation amount is a variable indicating a torque that assists the torque applied to the steering wheel 12 by the driver.

[0106] "About torque feedback processing" The target reaction force calculation process M26, which is torque feedback processing, does not necessarily include the second manipulated variable calculation process M90.

[0107] "Calculation process of base target torque Thb*" The process of calculating the base target torque Thb* using the axial force Taf as an input is not limited to the process of using the vehicle speed V as an input in addition to the axial force Taf.

[0108] It is not essential to calculate the base target torque Thb* using the axial force Taf as an input. For example, the base target torque Thb* may be calculated using the steering torque Th and the vehicle speed V as inputs. This can be achieved by, for example, having map data stored in the storage device 74, and having the PU 72 perform map calculations to calculate the base target torque Thb*. Here, the map data is data that uses the steering torque Th and the vehicle speed V as inputs and the base target torque Thb* as an output variable.

[0109] "About operation processing" The control method for the reaction motor 20 is not limited to dq-axis current feedback processing. For example, if a DC motor is used as the reaction motor 20 and the drive circuit is an H-bridge circuit, it is sufficient to simply control the current flowing through the reaction motor 20.

[0110] The operation processing does not necessarily have to be processing in which the PD operation amount Tpd or the sum of the PD operation amount and the second operation amount Ts2 is used as the command value for the reaction force motor 20. For example, the operation processing may include processing in which the PD operation amount Tpd or the sum of the PD operation amount and the second operation amount Ts2 is used as an input to calculate a command value for the rotation angle of the reaction force motor 20. This can be performed, for example, as follows. That is, the PU 72 calculates the torque applied to the steering shaft 14 in accordance with the sum of the PD operation amount Tpd or the PD operation amount and the second operation amount Ts2. This calculation processing may take into account the steering torque Th. Then, the PU 72 calculates the rotation angle of the steering shaft 14 by inputting the torque applied to the steering shaft 14 into a model equation for the steering device. The PU 72 calculates the command value for the rotation angle of the reaction force motor 20 in accordance with this rotation angle.

[0111] "Regarding steering angle control" Instead of the pinion angle feedback process M16, a process may be used that controls the detected value of the movement amount of the steered shaft 40 to a target value. In this case, in the above embodiment, the control amount and the like related to the pinion angle θp are replaced with the control amount and the like related to the movement amount of the steered shaft 40.

[0112] It is not essential that the control of the steering angle include a process of calculating a manipulated variable for controlling a control variable indicating the steering angle, such as pinion angle θp, by feedback control. For example, the control of the steering angle may include a process of calculating a manipulated variable for controlling a control variable indicating the steering angle to a target value by open-loop control. Also, for example, the control of the steering angle may include a process of calculating the sum of the manipulated variable for open-loop control and the manipulated variable for feedback control.

[0113] The control method for steering motor 60 is not limited to dq-axis current feedback processing. For example, if a DC motor is used as steering motor 60 and the drive circuit is an H-bridge circuit, it is sufficient to simply control the current flowing through steering motor 60.

[0114] "About the operating parts" The operating member operated by the driver to steer the vehicle is not limited to the steering wheel 12. For example, it may be a joystick.

[0115] "Motors mechanically connected to operating members" (a) Reaction Actuator Ar The reaction motor 20 mechanically connected to the steering wheel 12 is not limited to a three-phase brushless motor. For example, it may be a DC motor with brushes.

[0116] (b) Motor drive circuit The drive circuit for the motor mechanically connected to the operating member is not limited to the reaction force inverter 22. For example, it may be an H-bridge circuit.

[0117] (c) Other The provision of the reduction mechanism 16 is not essential. "About steering control devices" The steering control device is not limited to one that includes a PU 72 and a storage device 74 and executes software processing. For example, it may include a dedicated hardware circuit, such as an ASIC, that executes at least part of the processing executed in the above embodiment. That is, the control device may include a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit that includes a processing device that executes all of the above processing in accordance with a program, and a program storage device, such as a storage device, that stores the program. (b) A processing circuit that includes a processing device and a program storage device that executes part of the above processing in accordance with a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit that includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices that include a processing device and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0118] "About steering actuators" The steering actuator At may be, for example, one in which steering motor 60 is arranged coaxially with steering shaft 40. Alternatively, for example, one connected to steering shaft 40 via a belt-type reducer using a ball screw mechanism may be used.

[0119] The steering actuator At is not limited to a configuration in which the right steered wheels 44 and the left steered wheels 44 are linked together. In other words, the steering actuator At may be one that can control the right steered wheels 44 and the left steered wheels 44 independently.

[0120] "About the steering device" The steering device capable of changing the relationship between the steering angle and the turning angle is not limited to a steering device in which the transmission of power between the steering wheel 12 and the steered wheels 44 is cut off. For example, a steering device capable of changing the relationship between the steering angle and the turning angle may be configured by using a variable gear as the gear that enables the transmission of power between the steering wheel 12 and the steered wheels 44. Furthermore, the steering device is not limited to a steering device in which the relationship between the steering angle and the turning angle is changeable. For example, a steering device in which the steering wheel 12 and the steered wheels 44 are mechanically connected may be used.

Claims

1. A steering control device configured to operate a motor mechanically coupled to an operating member operated by a driver to steer a vehicle, the steering control device is configured to perform torque feedback processing, operation processing, and characteristic change processing; the torque feedback processing includes a processing for calculating an operation amount for controlling the steering torque to a target steering torque by feedback control, the steering torque is a torque input to the operation member, the operation processing is processing for operating a drive circuit of the motor based on the operation amount in a state in which the operation member and the steered wheels of the vehicle are mechanically separated from each other, The characteristic change process is a process for changing the response characteristic of the feedback control in accordance with the operation state of the operation member.

2. 2. The steering control device according to claim 1, wherein the characteristic change process includes a process of switching the response characteristic between a first operation state in which the operating member is operated to move away from a neutral position and a second operation state in which the operating member is operated to move closer to the neutral position.

3. 3. A steering control device according to claim 2, wherein the characteristic change process is a process for identifying the first operation state and the second operation state according to the sign of the product of the displacement amount of the operating member and the rate of change of the displacement amount, and includes a process for switching the response characteristic using the value of the product as an input.

4. 3. The steering control device according to claim 2, wherein the characteristic change process is a process for distinguishing between the first operation state and the second operation state according to the sign of the product of the rate of change of the displacement amount of the operating member and the steering torque, and includes a process for switching the response characteristic using the value of the product as an input.

5. the torque feedback processing is processing for calculating the operation amount based on an output value of a proportional element of a difference between the steering torque and the target steering torque, 5. The steering control device according to claim 2, wherein the characteristic change process includes a process of making the gain of the proportional element in the first operation state larger than the gain of the proportional element in the second operation state.

6. the torque feedback processing is processing for calculating the manipulated variable based on an output value of a differential element, 5. The steering control device according to claim 2, wherein the characteristic change process includes a process of making the gain of the differential element in the first operation state larger than the gain of the differential element in the second operation state.

7. the torque feedback processing includes filtering; A steering control device according to any one of claims 2 to 4, wherein the characteristic change processing includes processing that makes the frequency characteristics of the filter processing in the first operation state different from the frequency characteristics of the filter processing in the second operation state.

8. the torque feedback processing is processing for calculating the operation amount based on an output value of a proportional element of a difference between the steering torque and the target steering torque, the filtering process includes low-pass filtering to suppress high-frequency components of the proportional element; The steering control device according to claim 7 , wherein the characteristic change process includes a process of making a cutoff frequency of the low-pass filter process in the first operation state lower than the cutoff frequency in the second operation state.

9. 2. The steering control device according to claim 1, wherein the characteristic change process includes a process of changing the response characteristic depending on the degree of influence of friction on the displacement of the operating member.

10. 10. The steering control device according to claim 9, wherein the characteristic change process includes a process of changing the response characteristic in accordance with an absolute value of the sum of the steering torque and a torque variable of the motor, and the larger the absolute value, the smaller the degree of influence of the friction is considered to be.

11. the torque feedback processing is processing for calculating the operation amount based on an output value of a proportional element of a difference between the steering torque and the target steering torque, 11. The steering control device according to claim 9, wherein the characteristic change process includes a process of setting a gain of the proportional element when the degree of influence is large to be equal to or greater than a gain of the proportional element when the degree of influence is small.

12. the torque feedback processing is processing for calculating the manipulated variable based on an output value of a differential element, The steering control device according to claim 9 , wherein the characteristic change process includes a process of setting a gain of the differential element when the degree of influence is large to be equal to or greater than a gain of the differential element when the degree of influence is small.

13. the torque feedback processing includes filtering; The steering control device according to any one of claims 9 to 11, wherein the characteristic change process includes a process of changing a frequency characteristic of the filtering process in accordance with the magnitude of the degree of influence.

14. the torque feedback processing is processing for calculating the operation amount based on an output value of a proportional element of a difference between the steering torque and the target steering torque, the filtering process includes low-pass filtering process that suppresses high-frequency components of the output value of the proportional element, The steering control device according to claim 13, wherein the characteristic change process includes a process of setting a cutoff frequency of the low-pass filter process when the degree of influence is large to be equal to or lower than the cutoff frequency when the degree of influence is small.

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