Steering control device and steering control method

Abstract

Provided is steering torque control processing (M26) including processing of using a proportional element (M50) and a differential element (M60) corresponding to a difference between a steering torque and a target steering torque to calculate an operation amount for controlling the steering torque to achieve the target steering torque. An extension phase controller is provided to at least one element of two of the proportional element and the differential element. Extension phase controllers (M54, M66) are controllers each of which extend the advancement of the phase of the differential element with respect to the phase of the proportional element.

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 that operates a motor mechanically connected to an operating member operated by a driver to steer a vehicle, the steering control device being configured to execute a steering torque control process and an operating process, the steering torque control process including a process of calculating an operating amount for controlling the steering torque to a target steering torque using a proportional element and a derivative element corresponding to a difference between the steering torque and the target steering torque, the operating process being a process of operating a drive circuit of the motor to control the torque of the motor according to the operating amount, the steering torque being a torque input to the operating member, at least one of the proportional element and the derivative element being provided with an enlargement phase controller, and the enlargement phase controller being configured to enlarge a degree of lead of the phase of the derivative element relative to the phase of the proportional element.

[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 steering torque control process and executing an operation process, the steering torque control process including a process of calculating an operation amount for controlling the steering torque to a target steering torque using a proportional element and a derivative element corresponding to a difference between the steering torque and the target steering torque, the operation process including a process of operating a drive circuit of the motor to control the torque of the motor according to the operation amount, the steering torque being a torque input to the operating member, and the steering torque control process including a process of providing an enlarging phase controller in at least one of the proportional element and the derivative element to enlarge a degree of lead of the phase of the derivative element relative to a phase of the proportional element. [Brief explanation of the drawings]

[0007] [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. 3 is a diagram illustrating the characteristics of a filter according to the first embodiment. [Figure 5] 5A and 5B are time charts showing the response characteristics of the first embodiment. [Figure 6] 6A and 6B are diagrams illustrating the effects of the first embodiment. [Figure 7] Fig. 7A is a time chart showing the characteristics of the first embodiment, and Fig. 7B is a time chart showing the characteristics of a comparative example. [Figure 8] 8A and 8B are diagrams illustrating the effects of the first embodiment. [Figure 9]Fig. 9A is a time chart showing the characteristics of the first embodiment, and Fig. 9B is a time chart showing the characteristics of a comparative example. [Figure 10] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a second embodiment. [Figure 11] 11A and 11B are diagrams illustrating the effects of the second embodiment. [Figure 12] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a third embodiment. [Figure 13] 13A and 13B are diagrams illustrating the effects of the third embodiment. [Figure 14] FIG. 10 is a block diagram showing details of some processes executed by a control device according to a fourth embodiment. [Figure 15] FIG. 11 is a block diagram showing details of some processes executed by a control device according to a fifth 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] The pinion angle calculation process M12 is a process that uses the rotation angle θb as an input and calculates the pinion angle θp, which is the rotation angle of the pinion shaft 52. The pinion angle calculation process M12, for example, counts the number of rotations of the steering motor 60 from the rack neutral position, which is the position of the steering shaft 40 when the vehicle is traveling straight, to calculate the pinion angle θp. The rotation angle θb isThe pinion angle calculation process M12 includes a process for converting the rotation angle θb of the pinion shaft 52 into an integrated angle that includes a range exceeding 360°. The pinion angle calculation process M12 includes a process for calculating pinion angle θp, which is the actual rotation angle of pinion shaft 52, by multiplying the integrated angle obtained by the conversion by a conversion coefficient based on the rotational speed ratio of speed reduction mechanism 56. 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. 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 obtained from rotation angle θb of steering motor 60. Furthermore, pinion shaft 52 is meshed with steering shaft 40. Therefore, there is also a one-to-one correspondence between pinion angle θp and the amount of movement of steering shaft 40. That is, the pinion angle θp is a value that reflects the steering angle of the 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 input. 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 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 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.

[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 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The proportional element M50 receives the torque deviation ΔTh as input and outputs a value proportional to the torque deviation ΔTh. Specifically, the proportional gain multiplication process M52 multiplies the torque deviation ΔTh by the proportional gain Kp. The proportional phase controller M54 performs low-pass filtering on the output value of the proportional gain multiplication process M52. Specifically, the proportional phase controller M54 is a first-order lag filter as described below.

[0029] 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 M54 is the output value of the proportional element M50.

[0030] The differential element M60 receives the torque deviation ΔTh as input and outputs a value proportional to the time differential value of the torque deviation ΔTh. In more detail, the linear operator M62 receives the torque deviation ΔTh as input and outputs the time differential value of the torque deviation ΔTh. The differential gain multiplication process M64 multiplies the output value of the linear operator M62 by a differential gain Kd. The differential phase controller M66 advances the phase of a predetermined frequency component of the output value of the differential gain multiplication process M64. The differential phase controller M66 is a phase controller with zero order difference shown below.

[0031] {ad Td s+1} / (Td s+1) Here, "Td" is a time constant, and "ad>1". Fig. 4 shows a phase diagram of the differential phase controller M66. As shown in Fig. 4, the differential phase controller M66 advances the phase of frequency components near a predetermined center frequency f1. The output value of the differential phase controller M66 is the output value of the differential element M60.

[0032] Returning to FIG. 3, the addition process M70 is a process of adding the output value of the proportional element M50 and the output value of the derivative element M60 and outputting the result as the PD manipulated variable Tpd. The second manipulated variable calculation process M80 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 M80 may include, for example, at least one of the processes (A) to (H) described below.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 a steering angle ratio determined in the target pinion angle calculation process M14 according to the vehicle speed V.

[0039] The addition process M82 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 M80. <Actions and Effects of This Embodiment> 5A and 5B show Bode diagrams of the steering system 10 of this embodiment, particularly the steering wheel 12, the steering shaft 14, and the reaction force actuator Ar. Fig. 5A is a gain diagram, and Fig. 5B is a phase diagram.

[0040] 5A and 5B, in this embodiment, the plant characteristics have a resonance frequency in a frequency range slightly lower than frequency f2. Frequency f2 is also an anti-resonance frequency. Both resonance and anti-resonance occur because the torque sensor 80 has a torsion bar, and therefore a dual inertia system is formed by the inertia systems connected to both sides of the torsion bar.

[0041] The resonance and anti-resonance phenomena become apparent in a region where the magnitude of the steering torque Th is relatively large. This is thought to be because, in a region where the magnitude of the steering torque Th is small, the friction component becomes prominent when the steering wheel 12 is displaced, making the resonance and anti-resonance phenomena less likely to become apparent. Furthermore, the plant characteristics shown in FIGS. 5A and 5B tend to become apparent in a steer-by-wire steering device, as in this embodiment. This is thought to be because, when the magnitude of the steering torque Th is large enough to overcome the friction component, the load applied to the steering wheel 12 is small. In other words, when the steering wheel 12 and the steered wheels 44 are mechanically coupled, a load torque from the steered wheels 44 side is applied to the steering wheel 12. It is thought that this load torque tends to suppress the resonance and anti-resonance phenomena from becoming apparent.

[0042] If there is a resonance frequency, there is a risk that vibrations will occur due to control to the target steering torque Th*. If the proportional gain Kp is reduced to address this, the responsiveness will decrease. 6A and 6B show Bode diagrams when the controllers of this embodiment and the comparative example are used. FIG. 6A is a gain diagram. FIG. 6B is a phase diagram. In FIGS. 6A and 6B, the solid lines indicate the gain diagram and phase diagram of this embodiment. In FIGS. 6A and 6B, the dashed dotted lines indicate the gain diagram and phase diagram of the comparative example. The comparative example is a case where the proportional phase controller M54 and the differential phase controller M66 are not provided. The comparative example is an example in which the gain is reduced by, for example, reducing the proportional gain Kp in order to suppress instability due to resonance.

[0043] In the comparative example, a phase delay occurs because the gain is reduced. In contrast, in the illustrated embodiment, the proportional phase controller M54 and the differential phase controller M66 increase the gain and suppress the phase delay.

[0044] 7A and 7B show lamp responses having the characteristics shown in FIGS. 6A and 6B. Fig. 7A shows the lamp response characteristics according to this embodiment. Fig. 7B shows the lamp response characteristics in a comparative example shown by the dashed line in Figs. 6A and 6B.

[0045] As shown in Fig. 7A, in this embodiment, the steering torque Th follows the target steering torque Th* by increasing the responsiveness. In contrast, as shown in Fig. 7B, in the comparative example, the responsiveness is low, so the steering torque Th does not follow the target steering torque Th* well.

[0046] 8A and 8B show step response characteristics of steering torque Th. Specifically, FIG. 8A shows the step response characteristics of steering torque Th in this embodiment. FIG. 8B shows the step response characteristics of steering torque Th in a comparative example. The comparative example is a case where the proportional phase controller M54 and the differential phase controller M66 are not provided. However, the comparative example shown in FIG. 8B is an example in which the gain is not reduced as compared to the comparative example shown by the dashed dotted line in FIGS. 6A and 6B.

[0047] As shown in Fig. 8B, in the comparative example, vibration occurs in response to a step response, resulting in unstable control. This is a phenomenon caused by the plant characteristics shown in Figs. 5A and 5B. In contrast, as shown in Fig. 8A, in this embodiment, vibration is suppressed. This is achieved in this embodiment by delaying the phase of proportional element M50 by proportional phase controller M54 and advancing the phase of derivative element M60 by derivative phase controller M66.

[0048] That is, the phase of the proportional element M50 is delayed to suppress vibration, while the phase of the derivative element M60 is advanced to improve responsiveness. In other words, the actual phase lead of the derivative element M60 relative to the proportional element M50 is increased relative to the phase lead of the derivative element M60 relative to the proportional element M50, which is determined by the proportional gain Kp and the derivative gain Kd. This makes it possible to achieve both stability and responsiveness.

[0049] 9A and 9B show changes in the column shaft torque, the output value of the proportional element M50, and the output value of the derivative element M60. The column shaft torque is a torque corresponding to the sum of the steering torque Th and the torque of the reaction force motor 20. FIG. 9A shows changes in this embodiment. FIG. 9B shows changes in a comparative example. This comparative example is an example in which the gain is not lowered as compared to the comparative example shown by the dashed dotted line in FIGS. 6A and 6B. In particular, the comparative example uses settings that do not generate vibrations in a steering system in which the steering wheel 12 is mechanically connected to the steered wheels 44.

[0050] As shown in Fig. 9B, in the comparative example, as the column shaft torque increases, the column shaft torque, the output value of the proportional element M50, and the output value of the derivative element M60 oscillate. The column shaft torque deviates significantly from zero when friction occurring in the steering shaft 14 has been completely overcome. When friction has been completely overcome, the column shaft torque, the output value of the proportional element M50, and the output value of the derivative element M60 oscillate. In the case of the steer-by-wire steering system 10, this is presumably due to the fact that the steering shaft 14 is in a nearly unloaded state when friction has been completely overcome.

[0051] According to the present embodiment described above, the following actions and effects can be further obtained. (1-1) The differential phase controller M66 is a phase controller that advances the phase of a predetermined frequency component. By setting the center frequency f1 to a value near the frequency "f2" that exhibits the anti-resonance phenomenon, it is possible to increase the responsiveness near the frequency "f2" that exhibits the anti-resonance phenomenon while preventing the responsiveness in other frequency bands from being excessively increased. The center frequency f1 may be a frequency equal to or higher than the frequency "f2" that exhibits the anti-resonance phenomenon.

[0052] (1-2) The proportional phase controller M54 is a first-order lag element. This means that the adjustment element by the proportional phase controller M54 becomes a single cutoff frequency, making it possible to easily reduce the responsiveness of the proportional element M50 in a frequency band where it is desired to reduce the responsiveness.

[0053] (1-3) The differential phase controller M66 is a phase controller whose relative order is "0" and whose numerator and denominator orders are "1." This prevents the number of matching parameters from becoming excessively large.

[0054] (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 system. Even if a controller does not generate vibrations in a steering system in which the steering wheel 12 and the steered wheels 44 are mechanically connected, vibrations may occur in a steer-by-wire steering system. Therefore, the control of FIG. 3 is particularly useful.

[0055] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0056] Details of the target reaction force calculation process M26 according to this embodiment are shown in Fig. 10. For convenience, the processes in Fig. 10 that correspond to the processes shown in Fig. 3 are denoted by the same reference numerals.

[0057] 10, this embodiment does not include a proportional phase controller M54. However, this embodiment also includes a differential phase controller M66. Therefore, compared to a case where neither the proportional phase controller M54 nor the differential phase controller M66 is included, the degree of lead of the phase of the differential element M60 relative to the phase of the proportional element M50 can be increased.

[0058] <Actions and Effects of the Second Embodiment> 11A and 11B show step response characteristics in this embodiment and a comparative example. Specifically, FIG. 11A shows the step response characteristics of the steering torque Th in this embodiment. FIG. 11B shows the step response characteristics of the steering torque Th in a comparative example. The comparative example is the same as that in FIG. 8B.

[0059] As shown in FIGS. 11A and 11B, this embodiment also makes it possible to improve stability without reducing responsiveness. Third Embodiment The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0060] Details of the target reaction force calculation process M26 according to this embodiment are shown in Fig. 12. For convenience, the processes in Fig. 12 that correspond to the processes shown in Fig. 3 are denoted by the same reference numerals.

[0061] 12, this embodiment does not include a differential phase controller M66. However, this embodiment also includes a proportional phase controller M54. Therefore, compared to a case where neither the proportional phase controller M54 nor the differential phase controller M66 is included, the degree of lead of the phase of the differential element M60 relative to the phase of the proportional element M50 can be increased.

[0062] <Actions and Effects of the Third Embodiment> 13A and 13B show step response characteristics in this embodiment and a comparative example. Specifically, FIG. 13A shows the step response characteristics of the steering torque Th in this embodiment. FIG. 13B shows the step response characteristics of the steering torque Th in a comparative example. The comparative example is the same as that in FIG. 8B.

[0063] As shown in FIGS. 13A and 13B, this embodiment also makes it possible to improve stability without reducing responsiveness. <Fourth embodiment> The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0064] Fig. 14 shows details of the target reaction force calculation process M26 according to this embodiment. For convenience, in Fig. 14, the processes corresponding to those shown in Fig. 3 are denoted by the same reference numerals.

[0065] 14, this embodiment includes a differential phase controller M68, which is a second differential phase controller, in addition to a differential phase controller M66, which is a first differential phase controller. The differential phase controller M68 is a first-order lag element shown below.

[0066] 1 / (Td1 s+1) The cutoff frequency of the differential phase controller M68 is a frequency higher than the center frequency f1 shown in Fig. 4. In other words, the differential phase controller M68 is a phase controller that delays the phase of a frequency band higher than the frequency at which the phase is desired to be advanced by the differential phase controller M66.

[0067] <Actions and Effects of the Fourth Embodiment> The differential phase controller M66 advances the phase in a frequency band where a phase delay due to anti-resonance occurs. However, the differential phase controller M66 also advances the phase in a frequency range higher than the frequency band where a phase delay due to anti-resonance occurs. If the phase in a high frequency band is excessively advanced, noise is more likely to occur in the steering system 10. Therefore, in this embodiment, for a frequency range higher than the frequency band where a phase delay due to anti-resonance occurs, the phase advanced by the differential phase controller M66 is delayed by the differential phase controller M68. This makes it possible to suppress noise from occurring in the steering system 10.

[0068] Fifth Embodiment The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the fourth embodiment.

[0069] Details of the target reaction force calculation process M26 according to this embodiment are shown in Fig. 15. For convenience, the processes in Fig. 15 corresponding to those shown in Fig. 14 are denoted by the same reference numerals.

[0070] As shown in Fig. 15, in this embodiment, the input of the derivative element M60 is the steering torque Th. Therefore, the linear operator M62 is a process for calculating a first-order time derivative of the steering torque Th. Furthermore, the derivative gain multiplication process M64 is a process for multiplying the first-order time derivative of the steering torque Th by a derivative gain Kd. Furthermore, the PD manipulated variable is set to a value obtained by subtracting the output value of the derivative element M60 from the output value of the proportional element M50 in the subtraction process M70a.

[0071] 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 with each other within the scope of technical compatibility.

[0072] "On proportional elements" For example, the proportional phase controller M54 may be provided upstream of the proportional gain multiplication process. "About differential elements" For example, the differential phase controller M66 may be provided between the linear operator M62 and the differential gain multiplication process M64. Also, for example, the differential phase controller M66 may be provided upstream of the linear operator M62.

[0073] For example, the differential phase controller M68 may be provided between the differential phase controller M66 and the differential gain multiplication process M64. Also, for example, the differential phase controller M68 may be provided between the linear operator M62 and the differential gain multiplication process M64.

[0074] "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.

[0075] αp·(Tp2·s+1) / (Tp1·s+1) However, "αp<1". "About a differential phase controller that advances the phase of a specified frequency" The differential phase controller that advances the phase of a predetermined frequency is not limited to the one exemplified in the above embodiment.

[0076] "About the second differential phase controller" The embodiment in which the differential phase controller M68 is provided is not limited to the configuration in which the proportional element M50 is provided with the proportional phase controller M54.

[0077] The second differential phase controller, which is a differential phase controller that delays the phase, 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.

[0078] αd1·(Td2·s+1) / (Td1·s+1) However, "αd1<1". "About the phase controller for magnification" The phase controller for expansion when the PD manipulated variable Tpd is the manipulated variable of the preceding differential PD control is not limited to the controller exemplified in Fig. 15. For example, the phase controllers exemplified in Fig. 10, Fig. 12, etc. may be used.

[0079] The expansion phase controller is not limited to the controllers exemplified in the above-described embodiments and their modifications. For example, both the proportional phase controller and the differential phase controller may be first-order lag elements. However, the degree of phase lag compensation by the proportional phase controller is set to be greater than the degree of phase lag compensation by the differential element. This also makes it possible to configure a controller that expands the degree of phase lead of the differential element relative to the phase of the proportional element.

[0080] "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.

[0081] 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, Device As described in the "About" section, in the case of a device capable of transmitting power between the steering wheel 12 and the steered wheels 44, this is a variable indicating the torque that assists the torque applied to the steering wheel 12 by the driver.

[0082] "Steering torque control processing" The target reaction force calculation process M26, which is the steering torque control process, does not necessarily include the second operation amount calculation process M80.

[0083] "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.

[0084] 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 input. This can be realized by, for example, calculating the base target torque Thb* using the PU 72 in a map manner with map data stored in the storage device 74. Here, the map data is calculated by inputting the steering torque Th and the vehicle speed V. variable and the base target torque Thb* is used as an output variable.

[0085] "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.

[0086] 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 a command value for a motor such as 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: 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. The PU 72 then 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.

[0087] "Control of steering angle" Instead of the pinion angle feedback process M16, a process may be used in which a detected value of the movement amount of the steered shaft 40 is controlled to a target value by feedback control. 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.

[0088] 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.

[0089] 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.

[0090] "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.

[0091] "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.

[0092] (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.

[0093] (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.

[0094] "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.

[0095] 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.

[0096] "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 that operates a motor mechanically connected to an operating member that a driver operates to steer a vehicle, The steering control device is configured to execute a steering torque control process and an operation process, the steering torque control process includes a process of calculating an operation amount for controlling the steering torque to a target steering torque by using a proportional element and a derivative element according to a difference between the steering torque and the target steering torque, the operation process is a process of operating a drive circuit of the motor so as to control the torque of the motor in accordance with the operation amount, the steering torque is a torque input to the operation member, At least one of the two elements, the proportional element and the differential element, is provided with an enlargement phase controller; The steering control device, wherein the magnification phase controller is configured to magnify the degree of lead of the phase of the differential element relative to the phase of the proportional element.

2. the proportional element includes a proportional phase controller that is the magnification phase controller, the proportional phase controller is configured to delay the phase of the proportional element; the differential element includes a differential phase controller that is the magnification phase controller, 2. The steering control device according to claim 1, wherein the differential phase controller is configured to advance the phase of the differential element.

3. the proportional element includes a proportional phase controller that is the magnification phase controller, 2. The steering control device according to claim 1, wherein the proportional phase controller is configured to delay the phase of the proportional element.

4. the differential element includes a differential phase controller that is the magnification phase controller, 2. The steering control device according to claim 1, wherein the differential phase controller is configured to advance the phase of the differential element.

5. 5. A steering control device according to claim 2 or 4, wherein the differential phase controller is configured to advance the phase of a predetermined frequency component.

6. the differential phase controller is a first differential phase controller, the differential element includes a second differential phase controller in addition to the first differential phase controller, 6. A steering control device according to claim 5, wherein the second differential phase controller is configured to delay the phase of a frequency component higher than the predetermined frequency component in the output of the differential element.

7. 4. A steering control device according to claim 2, wherein the proportional phase controller is a first-order delay element.

8. 5. A steering control device according to claim 2, wherein the differential phase controller is a phase controller with a relative order of zero.

9. 7. A steering control device according to claim 6, wherein the second differential phase controller is a first-order lag element.

10. 10. The steering control device according to claim 1, wherein the differential element receives the difference between the steering torque and the target steering torque as an input.

11. 10. The steering control device according to claim 1, wherein the differential element receives the steering torque as an input.

12. 12. The steering control device according to claim 1, wherein the operation process is executed in a state where the operation member and the steered wheels of the vehicle are mechanically separated.

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 steering torque control process and executing an operation process; the steering torque control process includes a process of calculating an operation amount for controlling the steering torque to a target steering torque by using a proportional element and a derivative element according to a difference between the steering torque and the target steering torque, the operation process is a process of operating a drive circuit of the motor so as to control the torque of the motor in accordance with the operation amount, the steering torque is a torque input to the operation member, The steering torque control process includes a process of amplifying the degree of phase advance of the differential element relative to the phase of the proportional element by providing an amplifying phase controller in at least one of the two elements, the proportional element and the differential element.

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