JP2020075547A - Electric power steering device - Google Patents

Abstract

To set optimal target steering angle speed according to a steering state of a driver.SOLUTION: An electric power steering device comprises: a target steering angle speed setting part 120 that sets target return steering angle speed ωt for returning a steering shaft 2 to a neutral position according to a steering angle θ of the steering shaft 2, vehicle speed V and actual steering angle speed ω; handle returning control electric current calculating parts 103, 140, 141, 142 and 104 that calculate handle return control electric currents on the basis of the target return steering angle speed ωt; and a driving part 37 that drives a motor at an electric current command value corrected on the basis of the handle return control electric currents.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an electric power steering apparatus that drives a motor based on a current command value and assists a steering system by controlling the drive of the motor.

BACKGROUND ART An electric power steering device (EPS) that applies an assist torque to a steering mechanism of a vehicle by a rotational force of a motor transmits a driving force of a motor through a reduction gear to assist steering on a steering shaft or a rack shaft. It has a structure applied as force.
In such an electric power steering device, friction is large due to the reduction gear and the rack and pinion, and the equivalent moment of inertia about the steering shaft is large due to the motor for generating the assist torque.

Therefore, in the low vehicle speed range where the self-aligning torque (SAT) is small, the steering wheel return becomes worse due to the larger friction. This is because the steering angle does not return to the neutral point only with the SAT in the straight traveling state, so it is necessary to return the steering angle to the neutral point by the driver's steering intervention, which is a burden on the driver.
On the other hand, in the high vehicle speed range where the SAT is large, the steering angular velocity for returning the steering wheel tends to be higher than that in the low vehicle speed range because the SAT is large, but since the inertia moment is large, the inertia torque is also large, and the steering wheel at the neutral point of the steering angle Does not converge and overshoots, which may make the vehicle characteristics unstable.

As described above, the electric power steering apparatus needs compensation of different characteristics depending on the vehicle speed or the steering state, and various controls have been devised to achieve appropriate compensation when the steering wheel returns. ..
For example, Patent Document 1 below proposes an electric power steering device for the purpose of performing smooth steering wheel return control even during steering intervention by a driver.

  In Patent Document 1, in steering wheel return control that performs PID (Proportional Integral Differential) control according to a deviation between a target steering angular velocity calculated from a vehicle speed and a steering angle and a steering angular velocity, steering of a driver included in a steering torque and an assist current. It is described that the steering wheel return control suitable for the driver's intention is performed by using only the intention or the vehicle characteristic for the calculation / correction of the target steering angular velocity.

International Publication No. 2018/142650 pamphlet

However, in Patent Document 1 described above, the steering angular velocity generated by the driver's steering is not taken into consideration when calculating or correcting the target steering angular velocity, and there is a problem that the optimum target steering angular velocity may not be obtained depending on the steering state of the driver. ..
The present invention has been made in view of the above problems, and an object thereof is to set an optimum target steering angular velocity according to the steering state of a driver.

  In order to achieve the above object, an electric power steering apparatus according to an aspect of the present invention calculates a current command value based on at least a steering torque, drives a motor based on the current command value, and steers the motor by drive control. Assist control of the system. An electric power steering apparatus includes a steering angle detection unit that detects a steering angle of a steering shaft, a steering angular velocity detection unit that detects a steering angular velocity of a steering shaft, a vehicle speed detection unit that detects a vehicle speed, a steering angle, a vehicle speed, and a steering angle. A target steering angular velocity setting unit that sets a target return steering angular velocity for returning the steering shaft to the neutral position according to the angular velocity, and a steering wheel return control current calculation unit that calculates a steering wheel return control current based on the target return steering angular velocity, A drive unit that drives the motor with a current command value corrected by the handle return control current.

  According to the present invention, it is possible to set the optimum target steering angular velocity according to the steering state of the driver.

It is a block diagram which shows the outline of an example of the electric power steering apparatus of embodiment. FIG. 3 is a block diagram showing an example of a functional configuration of a control unit in FIG. 1. It is a block diagram which shows an example of a functional structure of the electric current command value correction | amendment part of FIG. It is a characteristic view showing an example of steering torque gain Th set by a steering torque gain part. It is a block diagram showing an example of functional composition of a target steering angular velocity setting part of a 1st embodiment. FIG. 6 is a characteristic diagram showing an example of a steering angle shift Δθ set by a steering angle shift setting unit. FIG. 9 is a characteristic diagram showing an example of a target return steering angular velocity ωt calculated by a target return steering angular velocity calculation unit. (A) is a characteristic diagram showing an example of the target return steering angular velocity ωt set according to the positive actual steering angular velocity ω, and (b) is a target return steering angular velocity set according to the negative actual steering angular velocity ω It is a characteristic view which shows an example of ωt. (A) is a schematic explanatory drawing which shows the effect | action at the time of additional steering, and (b) is a schematic explanatory drawing which shows the effect | action at the time of reverse steering. It is a characteristic view which shows an example of the vehicle speed gain KP set by the vehicle speed gain part. It is a characteristic view which shows an example of the viscosity coefficient C output from a viscosity coefficient output part. 6 is a flowchart showing an operation example of a current command value correction unit of the embodiment. 12 is a flowchart showing an example of target return steering angular velocity setting processing of FIG. 11. It is a block diagram showing an example of functional composition of a target steering angular velocity setting part of a 2nd embodiment. (A) is a characteristic diagram showing an example of the correction amount Δωt calculated by the correction amount calculation unit, and (b) is a characteristic diagram showing an example of the target return steering angular velocity ωt corrected by the correction amount Δωt. It is a block diagram showing an example of functional composition of a target steering angular velocity setting part of a 3rd embodiment. (A) is a characteristic diagram showing an example of the correction gain Kωt at the time of the steering-back steering, and (b) is a characteristic diagram showing an example of the target return steering angular velocity ωt at the time of the steering-back steering. (A) is a characteristic diagram showing an example of a correction gain Kωt at the time of further steering, and (b) is a characteristic diagram showing an example of a target return steering angular velocity ωt at the time of further steering.

  Embodiments of the present invention will be described in detail with reference to the drawings. The embodiments of the present invention described below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the configuration and arrangement of components. Is not specified below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims described in the claims.

(First embodiment)
(Constitution)
FIG. 1 shows an outline of an example of the electric power steering device of the embodiment. The steering shaft (column shaft, handle shaft) 2 of the steering wheel 1 is steered via a reduction gear 3, universal joints 4a and 4b, a rack and pinion mechanism 5, tie rods 6a and 6b, and further via hub units 7a and 7b. It is connected to wheels 8L and 8R.

  The steering shaft 2 is provided with a torque sensor 10 that detects the steering torque Td of the steering wheel 1 and a steering angle sensor 14 that detects the steering angle θ of the steering shaft 2, and a motor that assists the steering force of the steering wheel 1. 20 is connected to the steering shaft 2 via a reduction gear 3 (reduction gear ratio N). Electric power is supplied from the battery 13 to the control unit (ECU) 30 that controls the electric power steering device, and an ignition key signal is input via the ignition key 11.

The control unit 30 calculates the current command value of the assist (steering assist) command based on the steering torque Td detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and compensates for the current command value. The current supplied to the motor 20 is controlled by the voltage control command value Vref that has been subjected to the above.
The control unit 30 is connected to a CAN (Controller Area Network) 50 that sends and receives various vehicle information, and the vehicle speed V can also be received from the CAN 50. The control unit 30 can also be connected to a non-CAN 51 other than the CAN 50 that exchanges communication, analog / digital signals, radio waves, and the like.

The control unit 30 may include, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).
The storage device may include any one of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include a memory such as a register, a cache memory, a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main storage device.
The functions of the control unit 30 described below are realized, for example, by the processor of the control unit 30 executing a computer program stored in a storage device.

The control unit 30 may be formed of dedicated hardware for executing each information processing described below.
For example, the control unit 30 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the control unit 30 may have a programmable logic device (PLD: Programmable Logic Device) such as a field programmable gate array (FPGA).

An example of the functional configuration of the control unit 30 will be described with reference to FIG. The steering torque Td detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12 are input to a current command value calculation unit 31 that calculates a current command value Iref. The current command value calculation unit 31 may acquire the steering torque Td and the vehicle speed V via the CAN 50.
The current command value calculation unit 31 calculates the current command value Iref, which is the control target value of the current supplied to the motor 20, using an assist map or the like based on the input steering torque Td and vehicle speed V.

The current command value correction unit 32 acquires the corrected current command value Irefn by correcting the current command value Iref based on the steering torque Td, the vehicle speed V, the steering angle θ of the steering shaft 2, and the actual steering angular velocity ω. Details of the configuration and operation of the current command value correction unit 32 will be described later.
The corrected current command value Irefn is input to the current limiting unit 33, and the maximum current-limited current command value Irefm is input to the subtracting unit 34.

  The subtraction unit 34 calculates a deviation I (= Irefm-Im) obtained by subtracting the fed back motor current value Im from the current command value Irefm, and the deviation I is the PI control unit 35 for improving the characteristic of the steering operation. Entered in. The voltage control command value Vref whose characteristics have been improved by the PI control unit 35 is input to the PWM control unit 36, and the motor 20 is PWM-driven via the inverter 37 as a drive unit.

The current value Im of the motor 20 is detected by the motor current detector 40 and fed back to the subtraction unit 34. The angular velocity conversion unit 38 detects the actual steering angular velocity ω of the steering shaft 2 based on the change in the steering angle θ. The actual steering angular velocity ω may be obtained in consideration of the motor angle information obtained from a position sensor (not shown) that detects the position of the motor and the reduction gear ratio N.
The inverter 37 uses a FET (Field Effect Transistor) as a drive element and is configured by a FET bridge circuit.

  Next, the current command value correction unit 32 will be described. In the electric power steering device, the operation is blocked by the friction of the reduction gears and the rack and pinion for transmitting the assist force, and the steering wheel does not return to the neutral point even if the vehicle is in the running state where it is desired to return to the straight traveling state, but the vehicle is in the straight traveling state. It can be difficult to become. Therefore, by correcting (compensating) the current command value with the steering wheel return control current according to the steering angle and the vehicle speed, the steering wheel can be positively returned to the neutral point in the traveling state in which the vehicle is returned to the straight traveling state.

  Therefore, the current command value correction unit 32 sets the target return steering angular velocity (-ωt) according to the steering angle θ, the actual steering angular velocity ω and the vehicle speed V, and the steering torque and the assist torque (current The target steering angular velocity ω0 is calculated by adding the target velocity value calculated from the command value) to the target return steering angular velocity (−ωt) and multiplying the addition result by the transfer characteristic according to the virtual steering system characteristic. To do.

  The current command value correction unit 32 performs at least one control of P (proportional) control, I (integral) control, and D (differential) control on the deviation between the target steering angular velocity ω0 and the actual steering angular velocity ω. .. The current command value correction unit 32 corrects the target return steering angular velocity (-ωt) by the target velocity value calculated by dividing the sum of the steering torque Td and the assist torque Ta by the viscosity coefficient C to obtain the target steering angular velocity. By performing feedback control using, the steering wheel return control with a natural feeling is realized even during steering intervention by the driver.

  Here, the current command value correction unit 32 calculates the target steering angular velocity ω0 using a simple virtual vehicle model. The simple virtual vehicle model of the embodiment means a target speed value obtained based on the steering angle θ, the actual steering angular velocity ω, and the target return steering angular velocity (−ωt) obtained from the vehicle speed V, the steering torque Td, and the assist torque Ta. The target steering angular velocity ω0 is calculated by applying the steering system transfer function corresponding to the virtual inertia moment J and the viscosity coefficient C of the steering system to the total of

  By using the virtual vehicle model, the virtual inertia moment J and the viscosity coefficient C of the steering system can be set. Therefore, the vehicle characteristics can be arbitrarily determined. Further, since the virtual vehicle model also considers the steering intervention of the driver in consideration of the assist torque Ta, it is possible to provide a smooth steering wheel return even when the driver is steering.

  Here, assuming that the steering system does not have static friction, Coulomb friction, and elastic terms, the force balance equation of the self-aligning torque SAT, the steering torque Td, and the assist torque Ta is the following equation (1).

  Here, J is the inertia moment of the virtual steering system, and C is the viscosity coefficient of the virtual steering system. Since the actual steering angular velocity ω is the time derivative of the steering angle θ, the following equation (2) is established.

Therefore, when the target steering angular velocity is ω0, the following equation (3) is obtained.

  When s is a Laplace operator, the above equation (3) can be transformed into the following equation (4), and the following equation (5) can be obtained by rearranging the following equation (4).

  Therefore, the target steering angular velocity ω0 is given by the following equation (6).

  By rearranging the above equation (6), the following equation (7) is obtained.

  The target steering angular velocity ω0 is obtained by the above equation (7). Here, SAT / C can be considered as a steering angular velocity generated by the self-aligning torque SAT and a return steering angular velocity set according to the vehicle characteristics.

Is a transfer characteristic obtained from the virtual vehicle model.

Is a steering angular velocity generated by the steering torque Td and the assist torque Ta.

  Generally, the self-aligning torque SAT is set by the steering angle θ and the vehicle speed V, but in the present invention, the dynamic characteristics of the self-aligning torque SAT are taken into consideration. Since the self-aligning torque SAT is the multiplication of the cornering force and the caster rail, the dynamic characteristic of the self-aligning torque SAT is considered to be equivalent to the dynamic characteristic of the cornering force.

  Now, consider a case where the sideslip angle B suddenly occurs in a tire traveling in the same direction as the tire rotating direction. At this time, a lateral force F is generated on the tire, and it is considered that the ground contact surface is laterally deformed with respect to the tire body by y. Since the lateral velocity of the contact surface is the differential value of y, the sideslip angle of the contact surface is

  Becomes Therefore, assuming that the cornering power is K, the lateral force F of the tire at this time is

  Becomes Further, if the lateral rigidity of the tire is ky, it can be expressed as F = ky × y. If y is deleted from these equations, the following equation (12) is obtained.

  When this is Laplace transformed and expressed by the transfer function of the lateral force F with respect to the sideslip angle B,

And can be approximated by a first-order lag element whose time constant is T1.
As described above, the self-aligning torque SAT has a first-order lag characteristic with respect to the steering of the steering wheel 1. Therefore, the target return steering angular velocity ωt is configured to be set according to the vehicle speed V, the steering angle θ, and the actual steering angular velocity ω.
The steering torque Td can be detected by the torque sensor 10, and the assist torque Ta can be calculated from the current command value Iref in consideration of the motor torque constant, the reduction gear ratio N, and the multiplication value Kt of the gear efficiency. By dividing the sum of the steering torque Td and the assist torque Ta by a virtual viscosity coefficient C of the steering, the steering angular velocity generated by the steering torque Td and the assist torque Ta is calculated, and the sum is calculated to obtain the target steering. The angular velocity is ω0.

  The steering torque Td and the assist torque Ta include a fluctuation component due to road surface disturbance, but this is not due to the driver's intention. When this is reflected in the target steering angular velocity ω0, the vehicle may behave unintentionally by the driver, and may feel uncomfortable. Therefore, in the current command value correction unit 32, the steering input intended by the driver or the vehicle motion characteristic based on the steering input (yaw, roll, etc.) is provided in the subsequent stage of the target speed value ω1 calculated by the steering torque Td and the assist torque Ta. A filter (LPF) for attenuating higher frequency components is provided to realize stable control, smooth return, and steering feeling that suits the driver's intention. Generally, it is said that the steering frequency of the driver and the vehicle motion due to the steering of the driver are up to about 10 Hz, so that the filter characteristic has an attenuation characteristic of 10 Hz and a gain of 3 dB or more lower than the gain of 0.

The functional configuration of the current command value correction unit 32 will be described with reference to FIG. The steering torque Td is input to the steering torque gain unit 110 and the addition unit 102 that output the steering torque gain Th.
The steering angle θ is input to the target steering angular velocity setting unit 120 that sets the target return steering angular velocity ωt.
The vehicle speed V is input to the target steering angular velocity setting unit 120, the vehicle speed gain unit 130 that outputs the vehicle speed gain KP, and the viscosity coefficient output unit 133 that outputs the viscosity coefficient C.

The actual steering angular velocity ω is subtracted and input to the target steering angular velocity setting unit 120 and the subtraction unit 103. The current command value Iref is multiplied by the gain Kt in the gain unit 111 and input to the addition unit 102 as the assist torque Ta. Therefore, the addition result of the addition unit 102 is the sum of the steering torque Td and the assist torque Ta, and the total value is input to the first steering system characteristic unit 150 having the transfer function “1 / C”.
The target speed value ω1 from the first steering system characteristic unit 150 is input to the low-pass filter (LPF) 151, and the LPF 151 attenuates a frequency (10 Hz-) that is equal to or higher than the steering input of the driver or equal to or higher than the vehicle motion characteristic based on the steering input. The calculated target speed value ω2 is obtained and is input to the addition unit 101.

The target steering angular velocity setting unit 120 sets the target return steering angular velocity ωt based on the self-aligning torque SAT based on the steering angle θ, the actual steering angular velocity ω, and the vehicle speed V. Details of the configuration and operation of the target steering angular velocity setting unit 120 will be described later.
The target return steering angular velocity ωt is inverted (-ωt) in the inverting unit 121 and input to the adding unit 101, and the target velocity value ω3 that is the addition result of the adding unit 101 is transferred function "1 / (J / Cs + 1). ) ”Is input to the second steering system characteristic unit 160.

The viscosity coefficient C from the viscosity coefficient output unit 133 is input to the first steering system characteristic unit 150 and the second steering system characteristic unit 160, and the second steering system characteristic unit 160 calculates the inertia moment J, the viscosity coefficient C, and the above equation. The target steering angular velocity ω0 is obtained by multiplying the target velocity value ω3 by the transfer function determined based on (8).
The target steering angular velocity ω0 is added and input to the subtractor 103, and the actual steering angular velocity ω is subtracted and input to the subtractor 103. The subtraction unit 103 calculates a deviation SG1 between the target steering angular velocity ω0 and the actual steering angular velocity ω, and the deviation SG1 is input to the multiplication unit 132.

Further, the steering torque gain Th output from the steering torque gain unit 110 is input to the multiplication unit 132 and the limiter 142, and the vehicle speed gain KP from the vehicle speed gain unit 130 is also input to the multiplication unit 132 and the limiter 142.
The multiplication unit 132 multiplies the deviation SG1 by the steering torque gain Th and the vehicle speed gain KP to obtain a steering wheel return control gain SG2 (proportional control value).

  The steering wheel return control gain SG2 is input to the addition unit 104, an integration control unit including an integration unit 140 and an integration gain unit 141 for improving characteristics, and further input to the limiter 142 via the integration gain unit 141. Then, the signal SG4, the output of which is limited according to the steering torque gain Th and the vehicle speed gain KP, is added to the steering wheel return control gain SG2 in the addition unit 104 and output as the steering wheel return control current HR.

  The integration of the integrator 140 compensates for a low steering torque range that is easily affected by friction, and particularly allows the integration to be used in a region where the friction is lost by letting go. The corrected current command value Irefn obtained by adding (correcting) the steering wheel return control current HR to the current command value Iref in the adder 105 and inputting the corrected current command value Irefn is input to the motor drive system.

  The steering angle sensor 14 is an example of the steering angle detection unit described in the claims. The angular velocity conversion unit 38 is an example of the steering angular velocity detection unit described in the claims. The vehicle speed sensor 12 is an example of the vehicle speed detection unit described in the claims. The subtraction unit 103, the integration unit 140, the integration gain unit 141, the limiter 142, and the addition unit 104 are an example of the handle return control current calculation unit described in the claims. The inverter 37 is an example of the drive unit described in the claims.

The steering torque gain Th set by the steering torque gain unit 110 has characteristics as shown in FIG. The steering torque gain Th is a constant value gain Th1 until the steering torque Td reaches T1, and the steering torque gain Th gradually decreases when the steering torque Td exceeds T1 and has an output characteristic that the gain becomes 0 when T2 or more. Although it decreases linearly in FIG. 4, it may be non-linear.
Next, the configuration and function of the target steering angular velocity setting unit 120 of the first embodiment will be described. Please refer to FIG.

  The target steering angular velocity setting unit 120 of the first embodiment sets the target return steering angular velocity ωt according to the steering angle θ, the actual steering angular velocity ω, and the vehicle speed V. Specifically, the target steering angular velocity setting unit 120 corrects the steering angle θ by a steering angle shift Δθ according to the actual steering angular velocity ω and the vehicle speed V, and sets the corrected steering angle (θ−Δθ) and the vehicle speed V. Accordingly, the target return steering angular velocity ωt is calculated. The target steering angular velocity setting unit 120 includes a steering angle shift setting unit 200, a subtraction unit 201, and a target return steering angular velocity calculation unit 202.

  The steering angle shift setting unit 200 calculates a steering angle shift Δθ according to the actual steering angular velocity ω. The steering angle shift Δθ has the characteristics shown in FIG. If the absolute value of the actual steering angular velocity ω is below a certain value, the steering angle shift Δθ is 0, and if it exceeds this value, the absolute value gradually increases. Further, when the sign of the actual steering angular velocity ω is positive, the sign of the steering angle shift Δθ is positive. When the sign of the actual steering angular velocity ω is negative, the sign of the steering angle shift Δθ is negative. Further, the higher the vehicle speed V, the larger the absolute value of the steering angle shift Δθ, and the narrower the range of the actual steering angular velocity ω where the steering angle shift Δθ is 0.

  Please refer to FIG. The subtraction unit 201 inputs the corrected steering angle (θ−Δθ) obtained by subtracting the steering angle shift Δθ from the steering angle θ to the target return steering angular velocity calculation unit 202. The target return steering angular velocity calculation unit 202 calculates the target return steering angular velocity ωt according to the corrected steering angle (θ−Δθ) and the vehicle speed V. Thus, by subtracting the steering angle shift Δθ from the steering angle θ according to the actual steering angular velocity ω, the phase delay of the self-aligning torque SAT with respect to the change of the steering angle θ can be reflected in the target return steering angular velocity ωt. ..

  The target return steering angular velocity ωt calculated by the target return steering angular velocity calculation unit 202 has the characteristics shown in FIG. 7. The target return steering angular velocity ωt is an increasing function whose absolute value increases as the absolute value of the corrected steering angle (θ-Δθ) increases, and the target return steering angular velocity ωt also gradually increases as the steering angle θ increases. Become. Further, the target return steering angular velocity ωt is 0 when the corrected steering angle (θ−Δθ) is 0, and the sign of the target return steering angular velocity ωt when the corrected steering angle (θ−Δθ) is positive. Is positive, and the sign of the target return steering angular velocity ωt is negative when the sign of the corrected steering angle (θ−Δθ) is negative. Furthermore, the higher the vehicle speed V, the larger the absolute value of the target return steering angular velocity ωt.

Next, a change in the characteristic of the target return steering angular velocity (-ωt) depending on the actual steering angular velocity ω will be described. FIG. 8A shows a change in the target return steering angular velocity (−ωt) when the sign of the steering angle shift Δθ is positive.
Since the subtraction unit 201 subtracts the positive steering angle shift Δθ from the steering angle θ, an angle smaller than the original steering angle θ is input to the target return steering angular velocity calculation unit 202. Therefore, the characteristic curve (solid line) of the target return steering angular velocity (-ωt) shifts in the positive direction of the steering angle θ more than the characteristic curve (broken line) without correction by the actual steering angular velocity ω.
As a result, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω increases even when there is no correction by the actual steering angular velocity ω in the vertical axis direction. That is, it moves in the positive direction along the vertical axis.

Here, since the sign of the steering angle shift Δθ is positive, the sign of the actual steering angular velocity ω is also positive. Therefore, additional steering is performed in the range where the steering angle θ is positive. The return steering is performed in the range where the steering angle θ is negative.
Further, in the range where the steering angle θ is positive, the direction of change of the steering angle θ that returns the steering shaft 2 to the neutral position is a negative direction, and in the range where the steering angle θ is negative, the steering shaft 2 that returns to the neutral position is steered. The direction of change in the angle θ is the positive direction.

Therefore, in the range in which the additional steering is performed, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω causes the steering shaft 2 to be in the neutral position as compared with the case where there is no correction by the actual steering angular velocity ω. It moves in the opposite direction (upward direction) to the direction of change of the steering angle θ (negative direction, downward direction in the vertical axis direction).
Therefore, if the direction of change of the steering angle θ that returns the steering shaft 2 to the neutral position is considered as the increasing direction of the target return steering angular velocity (−ωt), the target return steering angular velocity (−ωt) decreases.

On the other hand, in the range where the return steering is performed, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω causes the steering shaft 2 to be neutralized as compared with the case where there is no correction by the actual steering angular velocity ω. It moves in the same direction as the direction in which the steering angle θ returning to the position changes (positive direction, upward in the vertical axis direction).
Therefore, assuming that the direction of change of the steering angle θ that returns the steering shaft 2 to the neutral position is the increasing direction of the target return steering angular velocity (-ωt), the target return steering angular velocity (-ωt) increases.

FIG. 8B shows a change in the target return steering angular velocity (−ωt) when the sign of the steering angle shift Δθ is negative.
Since the subtraction unit 201 subtracts the negative steering angle shift Δθ from the steering angle θ, an angle larger than the original steering angle θ is input to the target return steering angular velocity calculation unit 202. Therefore, the characteristic curve (solid line) of the target return steering angular velocity (-ωt) shifts in the negative direction of the steering angle θ more than when there is no correction by the actual steering angular velocity ω (broken line). As a result, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω decreases even when there is no correction by the actual steering angular velocity ω in the vertical axis direction. That is, it moves in the negative direction along the vertical axis.

Here, since the sign of the steering angle shift Δθ is negative, the sign of the actual steering angular velocity ω is also negative. Therefore, the return steering is performed within the range where the steering angle θ is positive. Further steering is performed in the range where the steering angle θ is negative.
Therefore, in the range where the additional steering is being performed, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω makes the steering shaft 2 neutral compared to the case where there is no correction by the actual steering angular velocity ω. It moves in the opposite direction (downward) to the direction in which the steering angle θ returning to the position changes (positive direction, upward in the vertical axis direction).
Therefore, if the direction of change of the steering angle θ that returns the steering shaft 2 to the neutral position is considered as the increasing direction of the target return steering angular velocity (−ωt), the target return steering angular velocity (−ωt) decreases.

On the other hand, in the range where the return steering is performed, the target return steering angular velocity (-ωt) set according to the actual steering angular velocity ω causes the steering shaft 2 to be neutralized as compared with the case where there is no correction by the actual steering angular velocity ω. It moves in the same direction as the direction in which the steering angle θ returning to the position changes (negative direction, downward in the vertical axis direction).
Therefore, assuming that the direction of change of the steering angle θ that returns the steering shaft 2 to the neutral position is the increasing direction of the target return steering angular velocity (-ωt), the target return steering angular velocity (-ωt) increases.

The operation of setting the target return steering angular velocity (−ωt) as described above will be described with reference to FIGS. 9A and 9B. In addition, in order to simplify the description, the transfer function by the second steering system characteristic unit 160 is omitted.
The solid line is the characteristic curve of the target speed value ω3 calculated based on the target return steering angular velocity (−ωt) set according to the positive actual steering angular velocity ω, and the broken line is the case where there is no correction by the actual steering angular velocity ω. It is a characteristic curve of the target speed value ω3. As described above, since the target speed value ω3 is the sum of the target return steering angular speed (−ωt) and the target speed value ω2, it is offset from the target return steering angular speed (−ωt) by the target speed value ω2. There is. The chain double-dashed line is the locus of the actual steering angular velocity ω and is shown on the plane of the target velocity value ω3 and the steering angle θ.

Reference will be made to FIG. Now, it is assumed that the actual steering angular velocity ω and the steering angle θ are both in the positive range, and the steering is being increased.
At the intersection of the characteristic curve (solid line) of the target speed value ω3 and the locus of the actual steering angular speed ω indicated by the chain double-dashed line, there is no deviation between the target speed value ω3 and the actual steering angular speed ω, and the steering wheel return control current HR is 0. Become. In a region where the steering angle θ is larger than this intersection point, the target speed value ω3 is smaller than the actual steering angular speed ω, so the target speed value ω3 works to delay the positive actual steering angular speed ω. That is, it works in the direction in which the additional steering is hindered.

  Here, by setting the target return steering angular velocity (−ωt) as shown in FIG. 8A, the positive direction opposite to the direction (negative direction) of the change of the steering angle θ for returning the steering shaft 2 to the neutral position is set. When the target speed value ω3 moves in the direction of, the magnitude of the speed deviation Δ1 between the target speed value ω3 and the actual steering angular speed ω is smaller than the magnitude of the speed deviation Δ0 when there is no correction by the actual steering angular speed ω. Become. As a result, the steering wheel return control current HR in the direction opposite to the additional turn steering direction becomes small, and the damping effect that hinders the additional turn steering is reduced. This allows the driver to steer without feeling excessive viscosity.

Next, it is assumed that the actual steering angular velocity ω is in the negative range, the steering angle θ is in the positive range, and the switchback steering is performed. Reference is made to FIG.
In a region where the steering angle θ is larger than the intersection of the characteristic curve (one-dot chain line) of the actual steering angular velocity ω and the target velocity value ω3 indicated by the two-dot chain line, the target velocity value ω3 is smaller than the actual steering angular velocity ω. ω3 works to accelerate the negative actual steering angular velocity ω. That is, it works in a direction to assist the steering back.

  Here, by setting the target return steering angular velocity (−ωt) as shown in FIG. 8B, the direction of the steering angle θ returning the steering shaft 2 to the neutral position is changed to the same direction (negative direction). When the target speed value ω3 moves, the magnitude of the speed deviation Δ1 between the target speed value ω3 and the actual steering angular speed ω becomes larger than the magnitude of the speed deviation Δ0 when there is no correction by the actual steering angular speed ω. As a result, the steering wheel return control current HR in the same direction as the turning-back steering direction becomes large, and it becomes easy to return the steering shaft 2 to the neutral position.

  Further, in a region where the steering angle θ is smaller than the intersection of the locus of the actual steering angular velocity ω and the characteristic curve of the target velocity value ω3, the target velocity value ω3 is larger than the actual steering angular velocity ω, so the target velocity value ω3 is negative. It works to slow down the steering angular velocity ω. That is, it works in the direction of hindering the return steering.

  Here, by setting the target return steering angular velocity (−ωt) as shown in FIG. 8B, the direction of the steering angle θ returning the steering shaft 2 to the neutral position is changed to the same direction (negative direction). When the target speed value ω3 moves, the magnitude of the speed deviation Δ3 between the target speed value ω3 and the actual steering angular speed ω becomes smaller than the magnitude of the speed deviation Δ2 when there is no correction by the actual steering angular speed ω. As a result, the damping effect that hinders the return steering is reduced. This allows the driver to steer without feeling excessive viscosity.

  As described above, according to the present embodiment, by setting the target return steering angular velocity ωt according to the actual steering angular velocity ω, it becomes possible to reduce the occurrence of an excessive steering reaction force in the additional steering. Further, it is possible to prompt the steering shaft 2 to return to the neutral position in the steering back steering.

  Returning to the explanation of the current command value correction unit 32 again. The vehicle speed gain KP set by the vehicle speed gain unit 130 has a characteristic as shown in FIG. The vehicle speed gain KP is constant at a small gain KP1 until the vehicle speed V reaches at least the vehicle speed V1, becomes gradually higher at a vehicle speed V1 or higher, and is constant at a large gain KP2 at a vehicle speed V2 or higher. However, the vehicle speed gain KP is not limited to such a characteristic.

  The viscous resistance C set by the viscosity coefficient output unit 133 that changes the viscosity coefficient C according to the vehicle speed V has a characteristic as shown in FIG. Until the vehicle speed V reaches at least the vehicle speed V3, the viscosity coefficient C is a small viscosity coefficient C1 which is constant, the vehicle speed V3 or more increases gradually below the vehicle speed V4 (> V3), and the vehicle speed V4 or more remains a large viscosity coefficient C2. .. However, the viscous resistance C is not limited to such characteristics.

(Operation example)
Next, an operation example of the current command value correction section 32 will be described with reference to FIG.
First, the steering torque Td, the current command value Iref, the vehicle speed V, the steering angle θ, and the actual steering angular velocity ω are input (read) (step S1), and the steering torque gain unit 110 outputs the steering torque gain Th (step S2). The gain unit 111 multiplies the current command value Iref by the gain Kt to calculate the assist torque Ta (step S3), adds the steering torque Td by the addition unit 102, and inputs the total value to the first steering system characteristic unit 150. Yes (step S4).

Further, the target steering angular velocity setting unit 120 sets the target return steering angular velocity ωt based on the input steering angle θ, actual steering angular velocity ω and vehicle speed V (step S5).
FIG. 13 is a flowchart of target return steering angular velocity setting processing by the target steering angular velocity setting unit 120.

In step S30, the steering angle shift setting unit 200 calculates the steering angle shift Δθ according to the actual steering angular velocity ω.
In step S31, the subtraction unit 201 inputs the corrected steering angle (θ−Δθ), which is obtained by subtracting the steering angle shift Δθ from the steering angle θ, to the target return steering angular velocity calculation unit 202. The target return steering angular velocity calculation unit 202 calculates the target return steering angular velocity ωt according to the corrected steering angle (θ−Δθ) and the vehicle speed V.
After that, the target return steering angular velocity setting process ends.

  Referring to FIG. The inverting unit 121 inverts the sign of the target return steering angular velocity ωt (step S6), inputs the inverted target return steering angular velocity “−ωt” to the adding unit 101, and performs addition. The vehicle speed gain unit 130 outputs the vehicle speed gain KP according to the vehicle speed V (step S7), and the viscosity coefficient output unit 133 outputs the viscosity coefficient C according to the vehicle speed V (step S8).

The viscosity coefficient C is input to the first steering system characteristic unit 150 (step S9), and the transfer characteristic 1 / C is multiplied by the total value of the steering torque Td and the assist torque Ta to output the target speed value ω1 (step S10). The target speed value ω1 is input to the LPF 151 and filtered (step S11).
The target speed value ω2 filtered by the LPF 151 is added to the target return steering angular speed “−ωt” by the adder 101, and the added target speed value ω3 is input to the second steering system characteristic unit 160 (step S12). ..

The target steering angular velocity ω0 from the second steering system characteristic unit 160 is additionally input to the subtracting unit 103, the actual steering angular velocity ω is subtractively input to the subtracting unit 103, and the subtracting unit 103 calculates the deviation SG1 (step S13).
The deviation SG1 is input to the multiplication unit 132, multiplied by the steering torque gain Th and the vehicle speed gain KP (step S14), and the steering wheel return control gain SG2 is obtained by the multiplication.

  The steering wheel return control gain SG2 is integrated by the integration control unit (step S15), and further proportionally processed by the integration gain unit 141 (step S16), and the steering wheel return control gain SG3 is output. The steering wheel return control gain SG3 is input to the limiter 142, and is limited by the limiter 142 using the steering torque gain Th and the vehicle speed gain KP (step S17).

  The handle return control gain SG4 subjected to the limit processing by the limiter 142 is input to the adder 104 and added to the handle return control gain SG2 (step S18), and the handle return control current HR is output. The handle return control current HR is added to the current command value Iref by the adder 105 to correct it (step S19), and the corrected current command value Irefn is output (step S20).

(Effects of the first embodiment)
(1) The electric power steering device calculates the current command value Iref based on at least the steering torque Td, drives the motor 20 based on the current command value Iref, and assists the steering system by the drive control of the motor 20. The electric power steering device includes a steering angle sensor 14 that detects a steering angle θ of the steering shaft 2, an angular velocity conversion unit 38 that detects an actual steering angular velocity ω of the steering shaft 2, a vehicle speed sensor 12 that detects a vehicle speed V, and a steering wheel. A target steering angular velocity setting unit 120 that sets a target return steering angular velocity ωt for returning the steering shaft 2 to the neutral position according to the angle θ, the vehicle speed V, and the actual steering angular velocity ω, and a steering wheel based on the target return steering angular velocity ωt. The subtraction unit 103 for calculating the return control current, the integration unit 140, the integration gain unit 141, the limiter 142, and the addition unit 104, and the inverter 37 for driving the motor 20 with the current command value Irefn corrected by the handle return control current are provided.

  As a result, the target steering angular velocity can be corrected according to the actual steering angular velocity ω. As a result, the optimum target steering angular velocity can be set according to the steering state of the driver.

  (2) The target steering angular velocity setting unit 120 corrects the target return steering angular velocity ωt calculated according to the steering angle θ and the vehicle speed V according to the actual steering angular velocity ω. As a result, the target steering angular velocity can be corrected according to the actual steering angular velocity ω.

  (3) The target steering angular velocity setting unit 120 reflects the phase delay of the self-aligning torque with respect to the change of the steering angle θ on the target return steering angular velocity ωt according to the actual steering angular velocity ω. As a result, the optimum target return steering angular velocity ωt can be set in consideration of the phase delay of the self-aligning torque.

(4) The target steering angular velocity setting unit 120 increases the higher the actual steering angular velocity ω and decreases the target return steering angular velocity ωt during steering, and the higher the actual steering angular velocity ω increases the target return steering angular velocity ωt during reverse steering. ..
This makes it possible to reduce the steering wheel return control current that hinders the steering during the additional steering or the returning steering. This allows the driver to steer without feeling excessive reaction force. In addition, the steering wheel return control current for assisting the steering back can be increased. Therefore, it becomes easy to return the steering shaft 2 to the neutral position.

(5) The target steering angular velocity setting unit 120 calculates the target return steering angular velocity ωt according to the steering angle (θ−Δθ) corrected according to the actual steering angular velocity and the vehicle speed V.
Thereby, the phase delay of the self-aligning torque with respect to the change of the steering angle θ can be reflected in the target return steering angular velocity ωt. As a result, the steering wheel return control current that hinders the steering can be reduced during the additional steering and the steering back steering. This allows the driver to steer without feeling excessive reaction force. In addition, the steering wheel return control current for assisting the steering back can be increased. Therefore, it becomes easy to return the steering shaft 2 to the neutral position.

(Second embodiment)
Next, a second embodiment will be described. The target steering angular velocity setting unit 120 according to the second embodiment adds the correction value Δωt according to the actual steering angular velocity ω to the basic target return steering angular velocity ωt * calculated according to the steering angle θ and the vehicle speed V, to thereby obtain the steering angle. The target return steering angular velocity ωt is set based on θ, the actual steering angular velocity ω, and the vehicle speed V.
Reference is made to FIG. The target steering angular velocity setting unit 120 includes a correction amount calculation unit 203, a target return steering angular velocity calculation unit 202, and an addition unit 204.

The correction amount calculation unit 203 calculates a correction value Δωt according to the actual steering angular velocity ω and the vehicle speed V. The correction value Δωt calculated by the correction amount calculation unit 203 may have a characteristic as shown in FIG. If the absolute value of the actual steering angular velocity ω is less than a certain value, the correction value Δωt is 0, and if it exceeds this value, the absolute value gradually increases. Although it changes linearly in FIG. 15A, it may change nonlinearly.
Further, when the sign of the actual steering angular velocity ω is positive, the sign of the correction value Δωt is negative. When the sign of the actual steering angular velocity ω is negative, the sign of the correction value Δωt is positive. Further, the higher the vehicle speed V, the larger the absolute value of the correction value Δωt, and the narrower the range of the actual steering angular velocity ω where the correction value Δωt is 0.

  The target return steering angular velocity calculation unit 202 calculates the basic target return steering angular velocity ωt * according to the steering angle θ and the vehicle speed V. The characteristic of the basic target return steering angular velocity ωt * with respect to the steering angle θ is similar to the characteristic of the target return steering angular velocity ωt with respect to (θ−Δθ) shown in FIG. 7. The addition unit 204 calculates the target return steering angular velocity ωt by adding the correction value Δωt to the basic target return steering angular velocity ωt *.

FIG. 15B is an explanatory diagram of the characteristic of the target return steering angular velocity (-ωt) in the second embodiment. In the second embodiment, as in the first embodiment, when the actual steering angular velocity ω is positive (dashed line), the target return steering angular velocity (−ωt) is not corrected by the actual steering angular velocity ω (broken line). ) More than. When the actual steering angular velocity ω is negative (solid line), the target return steering angular velocity (−ωt) is smaller than when the actual steering angular velocity ω is not corrected (broken line).
Therefore, also in the second embodiment, the same effect as in the first embodiment can be obtained.

(Effects of Second Embodiment)
The target steering angular velocity setting unit 120 sets the target return steering angular velocity ωt by adding the correction value Δωt corresponding to the actual steering angular velocity ω to the basic target return steering angular velocity ωt * calculated according to the steering angle and the vehicle speed. ..
As a result, similar to the first embodiment, the phase delay of the self-aligning torque with respect to the change of the steering angle θ can be reflected in the target return steering angular velocity ωt. As a result, the steering wheel return control current that hinders the steering can be reduced during the additional steering and the steering back steering. This allows the driver to steer without feeling excessive reaction force. In addition, the steering wheel return control current for assisting the steering back can be increased. Therefore, it becomes easy to return the steering shaft 2 to the neutral position.

(Third Embodiment)
Next, a third embodiment will be described. The target steering angular velocity setting unit 120 according to the third embodiment multiplies the basic target return steering angular velocity ωt * calculated according to the steering angle θ and the vehicle speed V by the correction gain Kωt corresponding to the actual steering angular velocity ω to obtain the steering angle. The target return steering angular velocity ωt is set based on θ, the actual steering angular velocity ω, and the vehicle speed V.
Reference is made to FIG. The target steering angular velocity setting unit 120 includes a correction gain calculation unit 205, a target return steering angular velocity calculation unit 202, and a multiplication unit 206.

  The correction gain calculator 205 calculates the correction gain Kωt according to the steering angle θ, the actual steering angular velocity ω, and the vehicle speed V. The target return steering angular velocity calculation unit 202 calculates the basic target return steering angular velocity ωt * according to the steering angle θ and the vehicle speed V. The characteristic of the basic target return steering angular velocity ωt * with respect to the steering angle θ is similar to the characteristic of the target return steering angular velocity ωt with respect to (θ−Δθ) shown in FIG. 7. The multiplication unit 206 calculates the target return steering angular velocity ωt by multiplying the basic target return steering angular velocity ωt * by the correction gain Kωt.

  The correction gain calculation unit 205 compares the sign of the steering angle θ with the sign of the actual steering angular velocity ω to determine whether additional steering or reverse steering is being performed. When the sign of the steering angle θ and the sign of the actual steering angular velocity ω are the same, the correction gain calculation unit 205 determines that the steering is being increased, and when the sign of the steering angle θ is different from the sign of the actual steering angular velocity ω. It is determined that the return steering is being performed.

  The correction gain calculation unit 205 increases the correction gain Kωt from 1 according to the actual steering angular velocity ω during the return steering, and reduces the correction gain Kωt below 1 according to the actual steering angular velocity ω during the additional steering. Therefore, when the correction gain Kωt becomes larger than 1 during the switch-back steering, the absolute value of the target return steering angular velocity ωt increases more than before the correction, and when the correction gain Kωt becomes smaller than 1 during the additional steering, the target return steering angular velocity ωt becomes smaller. The absolute value is smaller than before correction.

  The correction gain calculation unit 205 calculates the correction gain Kωt having the characteristic shown in FIG. When the absolute value of the actual steering angular velocity ω is below a certain value, the correction gain Kωt is 1, and when it exceeds this value, the absolute value gradually increases. Although it changes linearly in FIG. 17A, it may change nonlinearly. When the correction gain Kωt reaches the upper limit value, it becomes constant at the upper limit value. Further, the higher the vehicle speed V, the narrower the range of the actual steering angular speed ω where the correction gain Kωt is 1.

  FIG. 17B is an explanatory diagram of the characteristic of the target return steering angular velocity (−ωt) corrected by the correction gain Kωt of FIG. 17A. When the correction gain Kωt becomes larger than 1, the absolute value of the target return steering angular velocity (−ωt) after correction (solid line) becomes larger than that when no correction is made (broken line).

  On the other hand, during the additional steering, the correction gain calculation unit 205 calculates the correction gain Kωt having the characteristic shown in (a) of FIG. The correction gain Kωt is 1 when the absolute value of the actual steering angular velocity ω is less than a certain value, and when it exceeds this value, the absolute value gradually decreases. Although it changes linearly in FIG. 18A, it may change nonlinearly. When the correction gain Kωt reaches the lower limit value, it becomes constant at the lower limit value. Further, the higher the vehicle speed V, the narrower the range of the actual steering angular speed ω where the correction gain Kωt is 1.

  18B is an explanatory diagram of the characteristic of the target return steering angular velocity (−ωt) corrected by the correction gain Kωt of FIG. 18A. Since the correction gain Kωt becomes smaller than 1, the absolute value of the target return steering angular velocity (−ωt) after correction (solid line) becomes larger than that when no correction is made (broken line).

  As described above, also in the third embodiment, the target return steering angular velocity (−ωt) increases in the direction of the change of the steering angle θ that returns the steering shaft 2 to the neutral position during the return steering as in the first embodiment. It will decrease during additional steering. Therefore, also in the second embodiment, the same effect as in the first embodiment can be obtained.

(Effect of the third embodiment)
The target steering angular velocity setting unit 120 sets the target return steering angular velocity ωt by multiplying the basic target return steering angular velocity ωt * calculated according to the steering angle θ and the vehicle speed V by the correction gain Kωt corresponding to the actual steering angular velocity ω. ..

  Thus, as in the first embodiment, the phase delay of the self-aligning torque with respect to the change of the steering angle θ can be reflected in the target return steering angular velocity ωt. As a result, the steering wheel return control current that hinders the steering can be reduced during the additional steering and the reverse steering. This allows the driver to steer without feeling excessive reaction force. In addition, the steering wheel return control current for assisting the steering back can be increased. Therefore, it becomes easy to return the steering shaft 2 to the neutral position.

  1 ... Steering wheel, 2 ... Steering shaft, 3 ... Reduction gear, 4a, 4b ... Universal joint, 5 ... Rack and pinion mechanism, 6a ... Tie rod, 6b ... Tie rod, 7a, 7b ... Hub unit, 8L ... Steering wheel, 8R ... Steering wheels, 10 ... Torque sensor, 11 ... Ignition key, 12 ... Vehicle speed sensor, 13 ... Battery, 14 ... Rudder angle sensor, 20 ... Motor, 30 ... Control unit, 31 ... Current command value computing section, 32 ... Current command value correction unit, 33 ... Current limiting unit, 34 ... Subtraction unit, 35 ... PI control unit, 36 ... PWM control unit, 37 ... Inverter, 38 ... Angular velocity conversion unit, 40 ... Motor current detector, 101, 102, 104, 105, 204 ... Addition unit, 103, 201 ... Subtraction unit, 110 ... Steering torque gain unit, 111 ... Gain unit, 120 ... Target steering angular velocity setting unit, 121 ... Inversion unit, 130 ... Vehicle speed gain unit, 132, 206 ... Multiplying section 133 ... Viscosity coefficient output section, 140 ... Integrating section, 141 ... Integral gain section, 142 ... Limiter, 150 ... First steering system characteristic section, 151 ... Low pass filter, 160 ... Second steering system characteristic section, 200 ... Steering angle shift setting unit, 202 ... Target return steering angular velocity calculation unit, 203 ... Correction amount calculation unit, 205 ... Correction gain calculation unit

Claims (7)

An electric power steering device that calculates a current command value based on at least a steering torque, drives a motor based on the current command value, and assist-controls a steering system by driving control of the motor,
A steering angle detection unit that detects the steering angle of the steering shaft,
A steering angular velocity detector for detecting the steering angular velocity of the steering shaft,
A vehicle speed detector for detecting the vehicle speed,
A target steering angular velocity setting unit that sets a target return steering angular velocity for returning the steering shaft to a neutral position according to the steering angle, the vehicle speed, and the steering angular velocity;
A steering wheel return control current calculation unit that calculates a steering wheel return control current based on the target return steering angular velocity;
A drive unit for driving the motor with the current command value corrected by the handle return control current;
An electric power steering device comprising:   The electric power steering apparatus according to claim 1, wherein the target steering angular velocity setting unit corrects the target return steering angular velocity calculated according to the steering angle and the vehicle speed according to the steering angular velocity. ..   The said target steering angular velocity setting part reflects the phase delay of the self-aligning torque with respect to the change of the said steering angle in the said target return steering angular velocity according to the said steering angular velocity. Electric power steering device.   The target steering angular velocity setting unit further increases the steering angular velocity to decrease the target return steering angular velocity during steering, and the higher the steering angular velocity increases the target return steering angular velocity during cutback steering. The electric power steering device according to claim 1.   5. The target steering angular velocity setting unit calculates the target return steering angular velocity according to the steering angle corrected according to the steering angular velocity and the vehicle speed, according to any one of claims 1 to 4. The electric power steering device described.   5. The target steering angular velocity setting unit adds a correction value according to the steering angular velocity to the target return steering angular velocity calculated according to the steering angle and the vehicle speed. The electric power steering device according to the item.   5. The target steering angular velocity setting unit multiplies the target return steering angular velocity calculated according to the steering angle and the vehicle speed by a correction gain according to the steering angular velocity. The electric power steering device according to the item.

Images