Steering control device and steering control method

Abstract

The present invention is configured to execute torque feedback processing (M40), operation processing (M42), and a characteristic change processing (M60, M74, M86). The torque feedback processing includes processing of calculating the operation amount for applying feedback control to a steering torque to attain a target steering torque. The steering torque is a torque input to an operation member. The operation processing is processing of operating a drive circuit for a motor on the basis of the operation amount. The characteristic change processing is processing of changing a response characteristic of the feedback control according to the magnitude of the torque of the motor.

Description

[Technical Field]

[0001] The present disclosure relates to a steering control device and a steering control method. [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 processing including processing for operating a drive circuit of the motor based on the operation amount, and the characteristic change processing including processing for changing a response characteristic of the feedback control in accordance with the magnitude of the torque of the motor.

[0006] Another aspect of the present disclosure provides a steering control method for operating a motor mechanically coupled to an operating member operated by a driver to steer a vehicle, the steering control method including: executing a torque feedback process; executing an operation process; and executing a characteristic change process, the torque feedback process including a process of 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 including a process of operating a drive circuit of the motor based on the operation amount, and the characteristic change process including a process of changing a response characteristic of the feedback control in accordance with the magnitude of the torque of the motor. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing a configuration of a vehicle according to a first embodiment. [Figure 2] 1 is a block diagram showing a part of the processing executed by a steering control device according to a first embodiment. [Figure 3] 1 is a block diagram showing a part of the processing executed by a steering control device according to a first embodiment. [Figure 4] FIG. 6 is a block diagram showing part of the processing executed by a steering control device according to a second embodiment. [Figure 5] 10 is a flowchart showing the procedure of processing executed by a steering control device according to a third embodiment. [Figure 6] FIG. 10 is a block diagram showing part of the processing executed by a steering control device according to a third embodiment. [Figure 7] FIG. 10 is a block diagram showing part of the processing executed by a steering control device according to a fourth embodiment. [Figure 8] FIG. 10 is a block diagram showing part of the processing executed by a steering control device according to a fifth embodiment. [Figure 9] FIG. 10 is a block diagram showing part of the processing executed by a steering control device according to a sixth embodiment. [Figure 10]FIG. 13 is a block diagram showing part of the processing executed by a steering control device according to a seventh embodiment. [Figure 11] FIG. 13 is a block diagram showing part of the processing executed by a steering control device according to an eighth embodiment. [Figure 12] FIG. 13 is a block diagram showing part of the processing executed by a steering control device according to a ninth embodiment. [Figure 13] FIG. 20 is a block diagram showing part of the processing executed by a steering control device according to a tenth embodiment. [Figure 14] FIG. 22 is a block diagram showing part of the processing executed by the steering control device according to the eleventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] 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.

[0010] The reaction motor 20 is a three-phase brushless 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.

[0011] 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.

[0012] 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 .

[0013] 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.

[0014] 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.

[0015] 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.

[0016] "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.

[0017] 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. Therefore, there is also a one-to-one correspondence between pinion angle θp and the steering angle of steered wheels 44.

[0018] 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.

[0019] 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 feedback-control the pinion angle θp to the target pinion angle θp*.

[0020] 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.

[0021] 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. The axial force Taf is an amount that depends on the lateral force acting on the steered wheels 44, so 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 a base target torque Thb* depending on the lateral force determined from the axial force Taf.

[0022] In detail, the base target torque calculation process M20 includes a process for variably setting 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 base target torque Thb* when the vehicle speed V is low to be equal to or less than the base target torque Thb* when the vehicle speed V is high. This can be realized, for example, by having the PU 72 calculate the base target torque Thb* using a map 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 used as input variables, and the base target torque Thb* is used as an output variable.

[0023] 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.

[0024] The end reaction force calculation process M22 is a process for calculating the end reaction force Ten. The end reaction force Ten is an amount of torque required of the reaction force motor 20 to prevent the steering angle θh from changing in a direction that would further increase the magnitude of the pinion angle θp when the magnitude of the pinion angle θp is equal to or greater than the end threshold θpth. The end reaction force calculation process M22 includes a process for setting the end reaction force Ten to zero when the magnitude of the pinion angle θp is less than the end threshold θpth. The end reaction force calculation process M22 includes a process for setting the end reaction force Ten when the magnitude of the pinion angle θp is large to be equal to or greater than the end reaction force Ten when the magnitude of the pinion angle θp is small when the magnitude of the pinion angle θp is equal to or greater than the end reaction force Ten when the pinion angle θp is small when the magnitude of the pinion angle θp is equal to or greater than the end reaction force Ten when the magnitude of the pinion angle θp is small. This process can be realized by having the PU 72 perform map calculations on the end reaction force Ten while map data is stored in advance in the storage device 74. This map data is data that uses the pinion angle θp as an input variable and the end reaction force Ten as an output variable.

[0025] The reference steering angle calculation process M24 is a process that calculates a reference steering angle θhr using the pinion angle θp and the steering angle ratio Dr as inputs. The reference steering angle θhr is the angle at which the ratio between the pinion angle θp and the steering angle θh becomes the steering angle ratio Dr when the steering angle θh is the reference steering angle θhr. In other words, it is a value obtained by converting the value of the pinion angle θp into the value of the corresponding steering angle θh. The value of the steering angle θh corresponds to the displacement of the operating member when the operating member is the steering wheel 12. If the reference steering angle θhr deviates significantly from the steering angle θh, it indicates that the pinion angle θp is not following the target pinion angle θp*.

[0026] The deviation calculation process M26 is a process for outputting a steering angle deviation Δθh, which is a value obtained by subtracting the steering angle θh from the reference steering angle θhr. The deviation compensation reaction force calculation process M28 is a process for calculating the deviation compensation reaction force Tcom. The deviation compensation reaction force Tcom is an amount of torque required of the reaction force motor 20 to suppress deviation between the reference steering angle θhr and the steering angle θh. The deviation compensation reaction force calculation process M28 includes a process for setting the deviation compensation reaction force Tcom to zero when the magnitude of the steering angle deviation Δθh is less than the compensation threshold Δcom. The deviation compensation reaction force calculation process M28 includes a process for setting the magnitude of the deviation compensation reaction force Tcom when the magnitude of the steering angle deviation Δθh is large to be equal to or greater than the magnitude of the deviation compensation reaction force Tcom when the magnitude of the steering angle deviation Δθh is small when the magnitude of the steering angle deviation Δθh is equal to or greater than the compensation threshold Δcom. This process can be realized by having the PU 72 perform map calculations of the deviation compensation reaction force Tcom with map data stored in advance in the storage device 74. The map data is data with the steering angle deviation Δθh as an input variable and the deviation compensation reaction force Tcom as an output variable.

[0027] The hysteresis processing M30 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 M30 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 M30 includes a processing for calculating the hysteresis correction amount Thys so that the absolute value of the target steering torque Th* is larger when it is being turned back than when it is being turned back. The hysteresis processing M30 includes a processing for variably setting the hysteresis correction amount Thys according to the vehicle speed V.

[0028] The addition process M32 is a process for calculating the target steering torque Th* by adding the end reaction force Ten, the deviation compensation reaction force Tcom, and the hysteresis correction amount Thys to the base target torque Thb*.

[0029] The target reaction force calculation process M40 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.

[0030] The reaction force operation process M42 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 M42 includes a process of calculating dq-axis current command values ​​based on the target reaction force Ts*. The reaction force operation process M42 also includes a process of calculating dq-axis currents based on the currents iu1, iv1, iw1 and the rotation angle θa. The reaction force operation process M42 then includes a process of calculating an operation signal MSs for operating the reaction force inverter 22 so that the dq-axis currents become command values.

[0031] FIG. 3 shows the details of the target reaction force calculation process M40. The deviation calculation process M50 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.

[0032] The absolute value calculation process M60 is a process for calculating the absolute value of the target steering torque Th*. The proportional element M70 is a process that receives the torque deviation ΔTh as an input and outputs a value proportional to the torque deviation ΔTh. Specifically, the proportional gain multiplication process M72 multiplies the torque deviation ΔTh by the proportional gain Kp. The proportional variable gain calculation process M74 receives the output value of the absolute value calculation process M60 as an input and calculates the proportional variable gain Gp. The proportional variable gain calculation process M74 sets the proportional variable gain Gp when the output value of the absolute value calculation process M60 is large to be equal to or smaller than the proportional variable gain Gp when the output value of the absolute value calculation process M60 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 output value of the absolute value calculation process M60 as an input variable and the value of the proportional variable gain Gp as an output variable.

[0033] Specifically, the proportional variable gain Gp has different constant values ​​when the output value of the absolute value calculation process M60 is equal to or less than the first threshold T1 and equal to or greater than the second threshold T2. Furthermore, when the output value of the absolute value calculation process M60 is greater than the first threshold T1 and less than the second threshold T2, the proportional variable gain Gp has a value that monotonically decreases according to the output value of the absolute value calculation process M60.

[0034] Proportional variable gain multiplication processing M76 is processing that multiplies the output value of proportional gain multiplication processing M72 by proportional variable gain Gp. The output value of proportional variable gain multiplication processing M76 is the output value of proportional element M70. The output value of proportional element M70 is a value obtained by multiplying torque deviation ΔTh by proportional gain Kp and proportional variable gain Gp. In other words, the gain of proportional element M70 is the product of proportional gain Kp and proportional variable gain Gp.

[0035] The differential element M80 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 M82 calculates the first-order time differential of the torque deviation ΔTh. The differential gain multiplication M84 multiplies the output value of the linear operator M82 by a differential gain Kd. The differential variable gain calculation M86 receives the output value of the absolute value calculation M60 as input and calculates the differential variable gain Gd. The differential variable gain calculation M86 sets the differential variable gain Gd when the output value of the absolute value calculation M60 is large to be equal to or greater than the differential variable gain Gd when the output value of the absolute value calculation M60 is small. This process may be, for example, map calculation of the differential variable gain Gd by the PU 72 with map data stored in the storage device 74. Here, the map data is data in which the output value of the absolute value calculation process M60 is used as an input variable and the value of the differential variable gain Gd is used as an output variable.

[0036] Specifically, the derivative variable gain Gd has different constant values ​​when the output value of the absolute value calculation process M60 is equal to or less than the third threshold T3 and equal to or greater than the fourth threshold T4. Furthermore, when the output value of the absolute value calculation process M60 is greater than the third threshold T3 but less than the fourth threshold T4, the derivative variable gain Gd has a value that monotonically increases in accordance with the output value of the absolute value calculation process M60. The first threshold T1 and the third threshold T3 may be the same. The second threshold T2 and the fourth threshold T4 may be the same.

[0037] The differential variable gain multiplication process M88 multiplies the output value of the differential gain multiplication process M84 by the differential variable gain Gd. The output value of the differential variable gain multiplication process M88 is the output value of the differential element M80. That is, the output value of the differential element M80 is the value obtained by multiplying the first-order time differential value of the torque deviation ΔTh by the differential gain Kd and the differential variable gain Gd. That is, the gain of the differential element M80 is the product of the differential gain Kd and the differential variable gain Gd.

[0038] The addition process M90 is a process of adding the output value of the proportional element M70 and the output value of the derivative element M80 together and outputting the result as the PD manipulated variable Tpd. The second manipulated variable calculation process M92 is a process for calculating a manipulated variable other than the PD manipulated variable Tpd for generating the target reaction force Ts*. The second manipulated variable calculation process M92 may include, for example, at least one of the processes (A) to (H) described below.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] The addition process M94 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 M92. <Actions and Effects of the First Embodiment> When the magnitude of the pinion angle θp is equal to or greater than the end threshold value θpth, the PU 72 superimposes the end reaction force Ten on the target steering torque Th*. Therefore, when the magnitude of the pinion angle θp is equal to or greater than the end threshold value θpth, the magnitude of the target steering torque Th* increases. Also, when the steering angle θh deviates significantly from the reference steering angle θhr, the PU 72 superimposes the deviation compensation reaction force Tcom on the target steering torque Th*. Therefore, when the steering angle θh deviates significantly from the reference steering angle θhr, the magnitude of the target steering torque Th* increases. When the magnitude of the target steering torque Th* increases, the control of the steering torque Th is more likely to become unstable than when the magnitude of the target steering torque Th* is small.

[0043] Therefore, the PU 72 variably sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the target steering torque Th*. This makes it possible to obtain an appropriate gain according to the target steering torque Th*. Therefore, it is possible to achieve a favorable balance between the responsiveness and stability of the control of the steering torque Th. Therefore, according to this embodiment, it is possible to achieve a favorable compromise between the stability and responsiveness of the feedback control of the steering torque Th.

[0044] The steering angle θh may deviate significantly from the reference steering angle θhr, for example, when the steering of the steered wheels 44 is hindered by a curb. According to the present embodiment described above, the following actions and effects can be further obtained.

[0045] (1-1) The gain of the proportional element M70 when the magnitude of the target steering torque Th* is large is set equal to or smaller than the gain of the proportional element M70 when the magnitude of the target steering torque Th* is small. As a result, among steering devices in which control becomes unstable due to the magnitude of the target steering torque Th*, instability can be suppressed by reducing the proportional gain, and this can suppress instability of control. Moreover, by increasing the gain of the proportional element M70 when the magnitude of the target steering torque Th* is small, the responsiveness of the control of the steering angle θh can also be increased.

[0046] (1-2) The gain of the derivative element M80 when the magnitude of the target steering torque Th* is large is set to be equal to or greater than the gain of the derivative element M80 when the magnitude of the target steering torque Th* is small. As a result, among steering devices in which the control becomes unstable due to the large magnitude of the target steering torque Th*, in a steering device in which the instability can be suppressed by increasing the derivative gain, the instability of the control can be suppressed.

[0047] (1-3) 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 steering device 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.

[0048] 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.

[0049] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0050] Fig. 4 shows details of the target reaction force calculation process M40 according to this embodiment. For convenience, the same reference numerals are used in Fig. 4 to designate processes corresponding to those shown in Fig. 3. In this embodiment, the end reaction force Ten is input to the absolute value calculation process M60. That is, the absolute value calculation process M60 is a process for calculating the absolute value of the end reaction force Ten.

[0051] <Actions and Effects of the Second Embodiment> The PU72 sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the end reaction force Ten. When the magnitude of the pinion angle θp exceeds the end threshold value θpth, the magnitude of the end reaction force Ten increases. Therefore, the end reaction force Ten is a variable that causes the magnitude of the target steering torque Th* to increase to the extent that it causes control instability. Therefore, by setting the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the end reaction force Ten, it is possible to achieve an appropriate compromise between stability and responsiveness of the feedback control of the steering torque Th.

[0052] Third Embodiment The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0053] In this embodiment, the determination result of the high load determination process is used to set the proportional variable gain Gp and the derivative variable gain Gd. Figure 5 shows the procedure for the process related to high load determination. The process shown in Figure 5 is realized by the PU 72 repeatedly executing the steering control program 74a, for example, at a predetermined interval. Note that, below, the step number of each process is represented by a number preceded by "S."

[0054] 5, PU 72 first acquires pinion angle θp, target pinion angle θp*, pinion angular velocity ωp, and q-axis current iqt (S10). q-axis current iqt is the q-axis component of the current flowing through steering motor 60. PU 72 calculates q-axis current iqt using currents iu2, iv2, iw2 and rotation angle θb as inputs.

[0055] Next, PU 72 determines whether or not high load determination flag F is "1" (S12). When high load determination flag F is "1", this indicates that the magnitude of the torque of steering motor 60 required to make pinion angle θp follow target pinion angle θp* becomes excessively large. When high load determination flag F is "0", this indicates that the above-mentioned situation does not exist.

[0056] When the PU 72 determines that the high load determination flag F is not "1" (S12: NO), it determines whether the logical product of the following conditions (α) to (γ) is true (S14). Condition (α): The condition is that the absolute value of the difference between the target pinion angle θp* and the pinion angle θp is equal to or greater than a threshold value Δth. The threshold value Δth may be set to, for example, equal to or greater than the maximum value of the difference between the target pinion angle θp* and the pinion angle θp that can occur when feedback control by the pinion angle feedback process M16 is performed normally.

[0057] Condition (β): The absolute value of the pinion angular velocity ωp is equal to or less than a predetermined velocity ωth. The predetermined velocity ωth is set to be less than the minimum value of the pinion angular velocity ωp that is realized when the absolute value of the difference between the target pinion angle θp* and the pinion angle θp is large and feedback control by the pinion angle feedback process M16 is performed normally.

[0058] Condition (γ): The condition that the magnitude of the q-axis current iqt is equal to or greater than a threshold value Ith. The threshold value Ith is set according to the allowable upper limit of the q-axis current that can be passed through the steering motor 60.

[0059] If the logical product is determined to be true (S14: YES), the PU 72 sets "1" to the high load determination flag F (S16). On the other hand, if the PU 72 determines that the high load determination flag F is "1" (S12: YES), it determines whether the logical product of the above conditions (α) to (γ) is false (S18). If the PU 72 determines that the logical product is false (S18: YES), it assigns "0" to the high load determination flag F (S20).

[0060] The PU 72 temporarily terminates the series of processes shown in FIG. 5 when it completes the processes of S16 and S20 or when it makes a negative determination in the processes of S14 and S18. Fig. 6 shows details of the target reaction force calculation process M40 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.

[0061] As shown in Fig. 6, the high load determination flag F is input to a variable conversion process M62. The variable conversion process M62 converts a binary label variable into a real value. The output value of the variable conversion process M62 is input to a gradual change process M64. The gradual change process M64 reduces the rate of change of the output variable relative to a change in the input variable. The gradual change process M64 may be, for example, a first-order lag filter process.

[0062] The output value of the gradual change process M64 is input to the proportional variable gain calculation process M74 and the differential variable gain calculation process M86. <Actions and Effects of the Third Embodiment> The PU 72 sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the real number of the high load determination flag F. When the high load determination flag F is "1," the target steering torque Th* increases. That is, for example, when the condition (α) is met, the steering angle θh deviates significantly from the reference steering angle θhr. As a result, the magnitude of the deviation compensation reaction force Tcom increases. Therefore, the high load determination flag F being "1" is a variable that causes the magnitude of the target steering torque Th* to increase to the point where it causes control instability. Therefore, by setting the gain of the proportional element M70 and the gain of the derivative element M80 according to the value of the high load determination flag F, a good compromise can be achieved between stability and responsiveness of the feedback control of the steering torque Th.

[0063] According to the present embodiment described above, the following actions and effects can be further obtained. (3-1) The PU 72 sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the value of the high load determination flag F gradually changed by the gradual change process M64. This makes it possible to prevent the gain from suddenly changing.

[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 M40 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. In this embodiment, the steering angle θh is input to the absolute value calculation process M60, which calculates the absolute value of the steering angle θh.

[0066] <Actions and Effects of the Fourth Embodiment> The PU72 sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the steering angle θh. When the magnitude of the steering angle θh is large, the magnitude of the pinion angle θp also becomes large. When the magnitude of the pinion angle θp exceeds the end threshold value θpth, the magnitude of the end reaction force Ten becomes large. Therefore, the magnitude of the steering angle θh is a variable that indicates whether the magnitude of the target steering torque Th* becomes large enough to cause control instability. Therefore, by setting the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the steering angle θh, a good compromise can be achieved between stability and responsiveness of the feedback control of the steering torque Th.

[0067] Fifth Embodiment The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0068] Fig. 8 shows details of the target reaction force calculation process M40 according to this embodiment. For convenience, in Fig. 8, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals. In this embodiment, the deviation compensation reaction force Tcom is input to the absolute value calculation process M60, which calculates the absolute value of the deviation compensation reaction force Tcom.

[0069] <Functions and Effects of Fifth Embodiment> The PU72 sets the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the deviation compensation reaction force Tcom. When the steering angle θh deviates significantly from the reference steering angle θhr, the magnitude of the deviation compensation reaction force Tcom increases. Therefore, the deviation compensation reaction force Tcom is a variable that causes the magnitude of the target steering torque Th* to increase to the point where it causes control instability. Therefore, by setting the gain of the proportional element M70 and the gain of the derivative element M80 according to the magnitude of the deviation compensation reaction force Tcom, an appropriate compromise can be achieved between stability and responsiveness of the feedback control of the steering torque Th.

[0070] Sixth Embodiment The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0071] Fig. 9 shows details of the target reaction force calculation process M40 according to this embodiment. For convenience, in Fig. 9, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals. As shown in Fig. 9, the proportional element M70 includes a proportional phase controller M100 and proportional characteristic varying processing M102. The proportional phase controller M100 performs low-pass filtering on the output value of the proportional gain multiplication processing M72. More specifically, the proportional phase controller M100 is a first-order lag filter as described below.

[0072] 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 M70.

[0073] The proportional characteristic varying process M102 is a process for varying the characteristic of the proportional phase controller M100 in accordance with the output value of the absolute value calculation process M60. Specifically, the proportional characteristic varying process M102 varies the cutoff frequency fc of the proportional phase controller M100 in accordance with the output value of the absolute value calculation process M60. 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 output value of the absolute value calculation process M60 is used as an input variable and the value of the time constant Tp is used as an output variable.

[0074] Specifically, the cutoff frequency fc is a constant value that differs when the output value of the absolute value calculation process M60 is equal to or less than the first threshold T1 and when the output value of the absolute value calculation process M60 is equal to or greater than the second threshold T2. Furthermore, when the cutoff frequency fc is greater than the first threshold T1 and less than the second threshold T2, the cutoff frequency fc is a value that monotonically decreases according to the output value of the absolute value calculation process M60.

[0075] The differential element M80 includes a differential phase controller M110 and differential characteristic variable processing 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 processing M84. The differential phase controller M110 is a phase controller with zero order difference as shown below.

[0076] {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.

[0077] The differential characteristic varying process M112 is a process for varying the characteristics of the differential phase controller M110 in accordance with the output value of the absolute value calculation process M60. Specifically, the differential characteristic varying process M112 varies the predetermined frequency component in accordance with the output value of the absolute value calculation process M60. This process may be, for example, a process in which the PU 72 performs map calculation of 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 output value of the absolute value calculation process M60 is used as an input variable and the value of the time constant Td or the variable ad is used as an output variable.

[0078] <Actions and Effects of the Sixth Embodiment> The PU 72 variably sets the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80 according to the magnitude of the target steering torque Th*. This makes it possible to obtain appropriate frequency characteristics according to the target steering torque Th*. Therefore, it is possible to achieve a favorable balance between responsiveness and stability in the control of the steering torque Th. Therefore, according to this embodiment, it is possible to achieve a favorable compromise between stability and responsiveness in the feedback control of the steering torque Th.

[0079] According to the present embodiment described above, the following actions and effects can be further obtained. (6-1) The cutoff frequency fc of the proportional phase controller M100 when the magnitude of the target steering torque Th* is large is set to be equal to or lower than the cutoff frequency fc of the proportional phase controller M100 when the magnitude of the target steering torque Th* is small. In other words, the responsiveness of the proportional element M70 when the magnitude of the target steering torque Th* is large is set to be equal to or lower than the responsiveness of the proportional element M70 when the target steering torque Th* is small. As a result, among steering devices in which control becomes unstable due to the large magnitude of the target steering torque Th*, in a steering device in which instability can be suppressed by reducing the responsiveness of the proportional element M70, it is possible to suppress instability of control. Moreover, by increasing the responsiveness of the proportional element M70 when the magnitude of the target steering torque Th* is small, it is also possible to increase the responsiveness of the control of the steering angle θh.

[0080] (6-2) The characteristics of the differential phase controller M110 are variably set according to the magnitude of the target steering torque Th*. This allows the frequency characteristics of the differential element M80 to be set to appropriate characteristics according to the frequency characteristics of the proportional element M70.

[0081] Seventh Embodiment The seventh embodiment will be described below with reference to the drawings, focusing on the differences from the sixth and second embodiments.

[0082] Fig. 10 shows details of the target reaction force calculation process M40 according to this embodiment. For convenience, in Fig. 10, the processes corresponding to those shown in Fig. 4 and Fig. 9 are denoted by the same reference numerals.

[0083] In this embodiment, the end reaction force Ten is input to the absolute value calculation process M60. That is, the absolute value calculation process M60 calculates the absolute value of the end reaction force Ten. The proportional characteristic varying process M102 and the derivative characteristic varying process M112 use the output value of the absolute value calculation process M60 as input.

[0084] <Actions and Effects of Seventh Embodiment> The PU72 sets the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80 according to the magnitude of the end reaction force Ten. This makes it possible to variably set the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80 according to the magnitude of the target steering torque Th* becoming so large that it causes control instability. This makes it possible to achieve an appropriate compromise between stability and responsiveness in the feedback control of the steering torque Th.

[0085] Eighth Embodiment The eighth embodiment will be described below with reference to the drawings, focusing on the differences from the third and sixth embodiments.

[0086] In this embodiment, the determination result of the high load determination process is used to set the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80. Details of the target reaction force calculation process M40 according to this embodiment are shown in Fig. 11. For convenience, the same reference numerals are used in Fig. 11 to designate processes corresponding to those shown in Fig. 6 and Fig. 9.

[0087] As shown in Fig. 11, the high load determination flag F is input to a variable conversion process M62. The variable conversion process M62 converts a binary label variable into a real value. The output value of the variable conversion process M62 is input to a gradual change process M64. The gradual change process M64 reduces the rate of change of the output variable relative to a change in the input variable. The gradual change process M64 may be, for example, a first-order lag filter process.

[0088] The output value of the gradual change processing M64 becomes the input to the proportional characteristic change processing M102 and the differential characteristic change processing M112. <Actions and Effects of Eighth Embodiment> The PU 72 sets the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80 according to the magnitude of the real-numbered value of the high load determination flag F. This allows the frequency characteristics of the proportional element M70 and the frequency characteristics of the derivative element M80 to be variably set according to the magnitude of the target steering torque Th* becoming so large that it causes control instability. This makes it possible to achieve an appropriate compromise between stability and responsiveness of the feedback control of the steering torque Th.

[0089] Ninth Embodiment The ninth embodiment will be described below with reference to the drawings, focusing on the differences from the fourth and sixth embodiments.

[0090] Details of the target reaction force calculation process M40 according to this embodiment are shown in Fig. 12. For convenience, the processes in Fig. 12 corresponding to those shown in Fig. 7 and Fig. 9 are denoted by the same reference numerals.

[0091] In this embodiment, the steering angle θh is input to the absolute value calculation process M60. That is, the absolute value calculation process M60 calculates the absolute value of the steering angle θh. The output value of the absolute value calculation process M60 is input to the proportional characteristic changing process M102 and the differential characteristic changing process M112.

[0092] Tenth Embodiment The tenth embodiment will be described below with reference to the drawings, focusing on the differences from the fifth and sixth embodiments.

[0093] Details of the target reaction force calculation process M40 according to this embodiment are shown in Fig. 13. Note that in Fig. 13, processes corresponding to those shown in Fig. 8 and Fig. 9 are denoted by the same reference numerals for convenience.

[0094] In this embodiment, the deviation compensation reaction force Tcom is input to the absolute value calculation process M60. That is, the absolute value calculation process M60 calculates the absolute value of the deviation compensation reaction force Tcom. The output value of the absolute value calculation process M60 is input to the proportional characteristic changing process M102 and the differential characteristic changing process M112.

[0095] Eleventh Embodiment The eleventh embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0096] Details of the target reaction force calculation process M40 according to this embodiment are shown in Fig. 14. For convenience, the processes in Fig. 14 that correspond to the processes shown in Fig. 3 are denoted by the same reference numerals.

[0097] As shown in Fig. 14, in this embodiment, the input of the derivative element M80 is the steering torque Th. Therefore, the linear operator M82 is a process for calculating a first-order time derivative of the steering torque Th. Furthermore, the derivative gain multiplication process M84 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 M80 from the output value of the proportional element M70 in the subtraction process M90a.

[0098] 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.

[0099] "About proportional elements" The proportional variable gain multiplication process M76 may be provided upstream of the proportional gain multiplication process M72. In other words, the torque deviation ΔTh may be multiplied by the proportional variable gain Gp.

[0100] For example, the proportional phase controller M100 may be provided upstream of the proportional gain multiplication process M72. The proportional element M70 may include the proportional phase controller M100 but may not include the proportional characteristic varying process M102.

[0101] "About differential elements" The differential variable gain multiplication process M88 may be provided upstream of the differential gain multiplication process M84. In other words, the output value of the linear operator M82 may be multiplied by the differential variable gain Gd. Also, for example, the differential variable gain multiplication process M88 may be provided upstream of the linear operator M82. In other words, the torque deviation ΔTh may be multiplied by the differential variable gain Gd.

[0102] For example, the differential phase controller M110 may be provided between the linear operator M82 and the differential gain multiplication process M84. Also, for example, the differential phase controller M110 may be provided upstream of the linear operator M82.

[0103] The differential element M80 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.

[0104] 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.

[0105] (c) Other It is not essential to provide a phase controller for both the proportional element M70 and the differential element M80. For example, a controller that adjusts the phase of the output value of the addition process M90 or the output value of the subtraction process M90a may be used.

[0106] "About characteristic change processing" (a) Changes to the proportional element M70 The process for setting the gain of the proportional element M70 according to the magnitude of the torque of the reaction force motor 20 is not limited to the process exemplified in the above embodiment. For example, depending on the characteristics of the steering device, the gain when the torque of the reaction force motor 20 is large may be set to be equal to or greater than the gain when the torque is small.

[0107] For example, both the change in the gain of the proportional element M70 by the proportional variable gain Gp and the change in the frequency characteristics of the proportional phase controller M100 may be performed. (b) Changes to differential element M80 The process of setting the gain of the derivative element M80 according to the magnitude of the torque of the reaction force motor 20 is not limited to the setting exemplified in the above embodiment. For example, depending on the characteristics of the steering device, the gain when the torque of the reaction force motor 20 is large may be set equal to or smaller than the gain when the torque is small.

[0108] The gain of the differential element M80 may be changed by the differential variable gain Gd, and the frequency characteristics of the differential phase controller M110 may be changed. (c) Input The variable indicating the difference between the steering angle and the value obtained by converting the steering angle variable value into the corresponding steering angle is not limited to the deviation compensation reaction force Tcom. For example, it may be the difference between the reference steering angle θhr and the steering angle θh.

[0109] The input variable indicating the magnitude of the torque of the motor mechanically connected to the steering wheel 12, which is an operating member, is not limited to the target torque variable, which is a variable indicating the magnitude of the target steering torque. For example, in the case of a steering device in which the steering wheel 12 and the steerable wheels 44 are mechanically connected as described in the "About the Steering Device" section below, the input variable may be a variable indicating the magnitude of the torque of the motor that steers the steerable wheels 44.

[0110] (d) Other The process of changing the gain of the proportional element M70 using the proportional variable gain Gp does not necessarily require the process of changing the gain of the derivative element M80 using the derivative variable gain Gd. That is, for example, while the process of changing the gain of the proportional element M70 using the proportional variable gain Gp is ​​executed, the process of changing the gain of the derivative element M80 using the derivative variable gain Gd may not be executed.

[0111] 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.

[0112] The characteristic change process when the PD manipulated variable Tpd is the manipulated variable of the advanced differential PD control is not limited to the controller exemplified in Fig. 14. For example, the processes exemplified in Figs. 4 to 13 may be used.

[0113] "About the end reaction force Ten" In the above embodiment, the end reaction force Ten is calculated using the pinion angle θp as an input, but this is not limiting. For example, the steering angle θh may be used as a steering angle variable that indicates the steering angle. In other words, since the magnitude of the steering angle θh and the magnitude of the steering angle have a positive correlation, the steering angle θh is a variable that indicates the steering angle.

[0114] "About the variables that determine the increase in the end reaction force Ten" 7 and 12, the steering angle θh is used as a variable for determining whether the end reaction force Ten is large or not, but this is not limiting. For example, the pinion angle θp may be used as a steering angle variable that indicates the steering angle.

[0115] "About high load judgment processing" In the process illustrated in Fig. 5, when the logical product of the conditions (α), (β), and (γ) is false, the high load determination flag F is set to "0." However, this is not limited to this. For example, hysteresis may be provided to suppress hunting in the determination. That is, for example, the condition that the condition (α) in the process of S18 is not satisfied may be replaced with the condition that the absolute value of the difference is equal to or less than "Δth-δ."

[0116] In the condition (β), the pinion angular velocity ωp is used as the steering angular velocity variable, but this is not limitative. For example, the steering angular velocity, which is the rate of change of the steering angle θh, may be used. The high load determination process is not limited to the process illustrated in Fig. 5. For example, if the logical product of the above conditions (α) and (β) is true, the high load determination flag F may be set to "1."

[0117] "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.

[0118] 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.

[0119] "About torque feedback processing" The target reaction force calculation process M40, which is torque feedback processing, does not necessarily include the second manipulated variable calculation process M92.

[0120] "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.

[0121] 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 input variables and the base target torque Thb* as an output variable.

[0122] "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.

[0123] "Control of steering angle" 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.

[0124] 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.

[0125] 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.

[0126] "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.

[0127] "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.

[0128] (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.

[0129] (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.

[0130] "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 in which steering motor 60 is connected to steering shaft 40 via a belt-type reducer using a ball screw mechanism may be used.

[0131] 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.

[0132] "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 includes processing for operating a drive circuit of the motor based on the operation amount, the torque feedback processing includes a 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 and an output value of a derivative element, The characteristic change process is a process of changing at least one of the gain of the proportional element and the gain of the differential element depending on the magnitude of the torque of the motor, and includes a process of making the at least one gain when the magnitude of the torque is large equal to or greater than the at least one gain when the magnitude of the torque is small.

2. 2. The steering control device according to claim 1, wherein the characteristic change process includes a process of setting a gain of the differential element when the magnitude of the torque is large to be equal to or greater than a gain of the differential element when the magnitude of the torque is small.

3. 2. The steering control device according to claim 1, wherein the characteristic change process includes a process of setting a gain of the proportional element when the magnitude of the torque is large to be equal to or greater than a gain of the proportional element when the magnitude of the torque is small.

4. 3. The steering control device according to claim 2, wherein the characteristic change process includes a process of setting a gain of the proportional element when the magnitude of the torque of the motor is large to a gain of the proportional element equal to or smaller than a gain of the proportional element when the magnitude of the torque of the motor is small.

5. 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 includes processing for operating a drive circuit of the motor based on the operation amount, the torque feedback processing includes a processing for calculating the manipulated variable based on an output value of a derivative element, and a differentiation filter processing for advancing or delaying a phase of a predetermined frequency component of the derivative element, A steering control device, wherein the characteristic change process includes a process of changing the predetermined frequency component in accordance with the magnitude of the torque of the motor.

6. the characteristic change process is a process in which a target torque variable is input and a response characteristic of the feedback control is changed in accordance with the magnitude of the value of the target torque variable, the target torque variable is a variable corresponding to the magnitude of the target steering torque, 6. The steering control device according to claim 1, wherein the magnitude of the torque of the motor is controlled to a larger value as the target steering torque increases by the operation process.

7. configured to execute a target steering torque calculation process, the target steering torque calculation process includes a process of calculating the target steering torque in accordance with an end reaction force when the magnitude of the value of the steering angle variable is equal to or greater than an end threshold value, so as to prevent the magnitude of the steering angle from becoming further larger, the steering angle variable is a variable indicating a steering angle, The steering angle is a turning angle of a steered wheel of the vehicle, 7. A steering control device according to claim 6, wherein the target torque variable is a variable corresponding to the end reaction force.

8. configured to execute a target steering torque calculation process, the target steering torque calculation process includes a process of calculating the target steering torque in accordance with an end reaction force when the magnitude of the value of the steering angle variable is equal to or greater than an end threshold value, so as to prevent the magnitude of the steering angle from becoming further larger, the steering angle variable is a variable indicating a steering angle, The steering angle is a turning angle of a steered wheel of a vehicle, 7. A steering control device according to claim 6, wherein the target torque variable is the value of the steering angle variable.

9. The control unit is configured to execute a steering angle feedback process, a high load determination process, and a target steering torque calculation process, the steering angle feedback processing is processing for controlling the value of a steering angle variable to the value of a target steering angle variable by feedback control, the steering angle variable is a variable indicating a steering angle, The steering angle is a turning angle of a steered wheel of the vehicle, the high load determination process is a process for determining that the motor is in a high load state on the condition that a logical product of a difference between a value of the steering angle variable and a value of the target steering angle variable is equal to or greater than a predetermined value and a magnitude of a value of the steering angular velocity variable is equal to or less than a predetermined velocity is true, the steering angular velocity variable is a variable indicating a rate of change of the value of the steering angle variable, the target steering torque calculation process includes, when the high load determination process determines that the motor is under a high load, calculating the target steering torque in accordance with a high load reaction force to prevent the difference from becoming even larger, 7. The steering control device according to claim 6, wherein the target torque variable is a variable indicating a result of the high load determination process.

10. configured to perform a gradual change process; 10. The steering control device according to claim 9, wherein the gradual change process includes a process of generating the value of the target torque variable by gradually changing a change in a binary variable indicating a result of the high load determination process.

11. the vehicle includes a steering device capable of changing the relationship between a displacement amount of an operating member and a steering angle, The steering angle is a turning angle of a steered wheel of the vehicle, The steering angle control unit is configured to execute a steering angle control process and a target steering torque calculation process, the steering angle control process is a process of controlling a value of a steering angle variable to a value of a target steering angle variable, the steering angle variable is a variable indicating a steering angle, the value of the target steering angle variable is set in accordance with the displacement amount of the operation member, the target steering torque calculation process includes a process of calculating the target steering torque in accordance with an operation amount for controlling the steering angle variable to reduce a difference between a value obtained by converting the value of the steering angle variable into a corresponding displacement amount of the operation member and the displacement amount of the operation member, 7. A steering control device according to claim 6, wherein the target torque variable is a variable indicating a difference between a value converted into a displacement amount of the operating member and the displacement amount of the operating member.

12. 12. The steering control device according to claim 1, wherein the operation process is executed in a state where power transmission between the operation member and the steered wheels is interrupted.

13. A steering control method for operating a motor mechanically connected to an operating member operated by a driver to steer a vehicle, comprising: the steering control method includes executing a torque feedback process, executing an operation process, and executing a characteristic change process; 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 includes processing for operating a drive circuit of the motor based on the operation amount, the torque feedback processing includes a 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 and an output value of a derivative element, The steering control method includes a process in which the characteristic change process changes at least one of the gain of the proportional element and the gain of the differential element according to the magnitude of the torque of the motor, and a process in which the at least one gain when the magnitude of the torque is large is equal to or greater than the at least one gain when the magnitude of the torque is small.

14. A steering control method for operating a motor mechanically connected to an operating member operated by a driver to steer a vehicle, comprising: the steering control method includes executing a torque feedback process, executing an operation process, and executing a characteristic change process; 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 includes processing for operating a drive circuit of the motor based on the operation amount, the torque feedback processing includes a processing for calculating the manipulated variable based on an output value of a derivative element, and a differentiation filter processing for advancing or delaying a phase of a predetermined frequency component of the derivative element, The steering control method, wherein the characteristic change process includes a process of changing the predetermined frequency component in accordance with the magnitude of the torque of the motor.

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