JP2020203499A - Turning controller - Google Patents

Abstract

To provide a turning controller capable of making a value of a derivative gain dependent on various required elements.SOLUTION: Through steering manipulation quantity calculation processing M16, a steering manipulation quantity Ts* is calculated as a manipulation quantity for feed-back controlling a steering torque Th into a target steering toque Th*. An axial force Taf that is a sum of the steering manipulation quantity Ts* and the steering torque Th is used as an input to calculate a pinion angle command value θp* in standard model arithmetic processing M20. Through angle manipulation quantity calculation processing M40, an angle manipulation quantity Tt* for controlling a pinion angle θp into a pinion angle command value θp* is calculated. An electric motor is operated based on a sum of the steering manipulation quantity Ts* and the angle manipulation quantity Tt*. A value obtained by multiplying a time differential value of the steering torque Th by a derivative gain is employed in the steering manipulation quantity calculation processing M16. The derivative gain is varied and designated depending on the axial force Taf and a vehicle speed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a steering control device for which a steering actuator having a built-in electric motor and steering a steering wheel is operated.

For example, Patent Document 1 below describes a control device that steers a steering wheel based on an operation amount for feedback-controlling a steering torque to a target steering torque. Specifically, this manipulated variable is calculated according to the sum of the output values of the proportional element, the integral element, and the differential element.

Japanese Unexamined Patent Publication No. 2004-203089

By the way, when the gain of feedback control is set to a fixed value, it is difficult to meet various requirements such as suppressing disturbance, ensuring stability, and optimizing steering feeling.

Hereinafter, means for solving the above problems and their actions and effects will be described.
1. 1. The target steering torque calculation process for calculating the target steering torque, which is the target value of the steering torque input by the driver, for the steering actuator that has a built-in electric motor and steers the steering wheels, and the steering torque are described above. Steering operation amount calculation for calculating the steering operation amount, which is the operation amount of the electric motor for steering the steering wheel for feedback control to the target steering torque and is the operation amount that can be converted into the torque required for the electric motor. The processing and the operation processing for operating the drive circuit of the electric motor based on the steering operation amount are executed, and the target steering torque calculation processing is a force that exerts the steering operation amount and the steering torque on the same object. It is a process of calculating the target steering torque based on the sum of the converted amounts, and the steering operation amount calculation process is a proportional term based on the difference between the steering torque and the target steering torque, and the time of the steering torque. The process of calculating the steering operation amount based on the process of adding the differential term proportional to the change, and the differential gain, which is the proportional coefficient of the time change in the differential term, are the target steering with respect to the amount of increase in the magnitude of the sum. It is a steering control device including a differential gain variable process for setting different values depending on whether the amount of increase in the magnitude of torque is a first value and a second value.

The inventor controls feedback control of steering torque when the amount of increase in the magnitude of the target steering torque is different from the amount of increase in the sum of the amounts obtained by converting the steering operation amount and the steering torque into the forces acting on the same object. It was found that the appropriate magnitude of the differential gain is different in order to maintain high controllability. Therefore, in the above configuration, by setting the differential gain variably depending on whether the amount of increase is the first case or the second case, the differential gain value is set to an appropriate value in each of the first case and the second case. Can be set to.

2. 2. In the differential gain variable processing, among the regions related to the magnitude of the sum and the target steering torque, the differentiation is larger than when the increase in the magnitude of the target steering torque is large in the first region. The process of setting the gain to a large value is executed, and in the second region where the magnitude of the sum is larger than that of the first region, the differentiation is larger than when the increase in the magnitude of the target steering torque is large. The steering control device according to 1 above, which executes a process of reducing the gain to a small value.

In the above configuration, the disturbance can be suppressed by setting the differential gain value to a larger value when the amount of increase in the magnitude of the target steering torque is larger than when it is small in the first region. Further, in the second region, stability can be ensured by setting the differential gain value to a smaller value when the amount of increase in the magnitude of the target steering torque is large than when it is small.

3. 3. The steering control device according to 1 or 2 above, wherein the differential gain variable processing includes a processing of variably setting the differential gain by inputting a sum of quantities converted into forces acting on the same object as an input.

In the above configuration, the sum, which is the input for the target steering torque calculation process, is used as the input when the differential gain is variably set, so that the steering operation amount and the steering torque are converted into the forces acting on the same object. An appropriate differential gain can be set according to the amount of increase in the magnitude of the target steering torque with respect to the amount of increase in the magnitude of the sum.

4. The target steering torque calculation process is a process of calculating the target steering torque based on the vehicle speed in addition to the sum of the amounts converted into the forces acting on the same object, and the differential gain variable process is the vehicle speed. The steering control device according to 1 above, which includes a process of variably setting the differential gain with the input of.

When the target steering torque is calculated according to the vehicle speed, the amount of increase in the magnitude of the target steering torque changes according to the vehicle speed even if the sum of the amounts converted into the forces acting on the same object is the same. .. Therefore, in the above configuration, by variably setting the differential gain based on the vehicle speed, the magnitude of the target steering torque with respect to the increase in the sum of the amounts obtained by converting the steering operation amount and the steering torque into the forces acting on the same object. The differential gain can be set more appropriately according to the amount of increase in the torque.

5. 4. The method according to any one of 1 to 4 above, which executes a proportional gain variable process for variably setting the proportional gain, which is a proportional coefficient of the difference between the steering torque and the target steering torque in the proportional term, according to the vehicle speed. It is a steering control device.

In the above configuration, in view of the fact that the amount of increase in the magnitude of the target steering torque changes according to the vehicle speed, the proportional gain can be variably set according to the amount of increase in the magnitude of the target steering torque, which in turn provides stability. A suitable compromise with responsiveness can be achieved.

6. One of the above 1 to 4 for executing the proportional gain variable processing in which the proportional gain, which is the proportional coefficient of the difference between the steering torque and the target steering torque in the proportional term, is variably set according to the steering torque. The steering control device described.

In the above configuration, by setting the proportional gain according to the steering torque, it is easier to deal with various required elements as compared with the case where the proportional gain is fixed.
7. The operation process includes an angle command value calculation process for calculating an angle command value which is a command value of a convertible angle that can be converted into a steering angle of the steering wheel according to the steering operation amount, and the convertible angle. The angle operation amount calculation process for calculating the angle operation amount, which is the operation amount for feedback control to the angle command value and can be converted into the torque required for the electric motor, and the drive circuit based on the angle operation amount. The steering control device according to any one of 1 to 6 above, which includes an operation signal generation process for generating an operation signal to be operated.

In the above configuration, since the drive circuit is operated based on the angle manipulated variable, the steering angle is controlled to the target value regardless of the state of the road surface on which the vehicle travels. Therefore, the reverse input from the road surface can be suppressed. Further, in the above configuration, the steering feeling can be adjusted according to how the angle command value is calculated based on the steering operation amount.

8. The steering control device according to 7 above, wherein the operation signal generation process is a process of generating the operation signal based on the angle operation amount without inputting the steering operation amount.

The figure which shows the electric power steering apparatus which concerns on 1st Embodiment. The block diagram which shows the process executed by the steering control device which concerns on the same embodiment. The block diagram which shows the steering operation amount calculation process which concerns on the same embodiment. The figure which illustrates the setting of the differential gain concerning the same embodiment. The figure which shows the electric power steering apparatus which concerns on 2nd Embodiment. The block diagram which shows the process executed by the steering control device which concerns on the same embodiment.

<First Embodiment>
Hereinafter, the first embodiment of the steering control device will be described with reference to the drawings.
As shown in FIG. 1, the electric power steering device 10 includes a steering mechanism 20 that steers the steering wheel 12 based on the operation of the driver's steering wheel 22, and a steering actuator 30 that electrically steers the steering wheel 12. It has.

The steering mechanism 20 includes a steering wheel 22, a steering shaft 24 fixed to the steering wheel 22, and a rack and pinion mechanism 27. The steering shaft 24 includes a column shaft 24a connected to the steering wheel 22, an intermediate shaft 24b connected to the lower end of the column shaft 24a, and a pinion shaft 24c connected to the lower end of the intermediate shaft 24b. doing. The lower end of the pinion shaft 24c, together with the rack shaft 26, constitutes a rack and pinion mechanism 27. Left and right steering wheels 12 are connected to both ends of the rack shaft 26 via tie rods 28. Therefore, the rotational movement of the steering wheel 22, that is, the steering shaft 24 is converted into a reciprocating linear motion in the axial direction (left-right direction in FIG. 1) of the rack shaft 26 via the rack and pinion mechanism 27. The reciprocating linear motion is transmitted to the steering wheels 12 via the tie rods 28 connected to both ends of the rack shaft 26, so that the steering angle of the steering wheels 12 changes.

On the other hand, the steering actuator 30 shares the rack shaft 26 with the steering mechanism 20, and also includes an electric motor 32, an inverter 33, a ball screw mechanism 34, and a belt type reduction mechanism 36. The electric motor 32 is a source of power for steering the steering wheel 12, and in the present embodiment, a three-phase surface magnet synchronous motor (SPMSM) is exemplified as the electric motor 32. The ball screw mechanism 34 is integrally attached around the rack shaft 26, and the belt type speed reduction mechanism 36 transmits the rotational force of the output shaft 32a of the electric motor 32 to the ball screw mechanism 34. The rotational force of the output shaft 32a of the electric motor 32 is converted into a force that causes the rack shaft 26 to reciprocate linearly in the axial direction via the belt type reduction mechanism 36 and the ball screw mechanism 34. The steering wheel 12 can be steered by the axial force applied to the rack shaft 26.

The steering control device 40 controls the steering wheel 12, and operates the steering actuator 30 in order to control the steering angle, which is the controlled amount thereof. The steering control device 40 determines the steering torque Th, which is the torque input by the driver via the steering wheel 22, and the vehicle speed V detected by the vehicle speed sensor 52, which are detected by the torque sensor 50 when controlling the control amount. refer. Further, the steering control device 40 refers to the rotation angle θm of the output shaft 32a detected by the rotation angle sensor 54 and the currents iu, iv, and iwa flowing through the electric motor 32. The currents iu, iv, and iw may be detected as voltage drops in the shunt resistors provided on each leg of the inverter 33.

The steering control device 40 includes a CPU 42, a ROM 44, and peripheral circuits 46, which are connected via a communication line 48. The peripheral circuit 46 includes a circuit that generates a clock signal that defines the internal operation, a power supply circuit, a reset circuit, and the like.

FIG. 2 shows a part of the processing executed by the steering control device 40. The process shown in FIG. 2 is realized by the CPU 42 executing the program stored in the ROM 44.
The base target torque calculation process M10 calculates the base target torque Thb *, which is the base value of the target steering torque Th * that the driver should input to the steering shaft 24 via the steering wheel 22, based on the axial force Taf described later. It is a process. Here, the axial force Taf is an axial force applied to the rack shaft 26. Since the axial force Taf is an amount corresponding to the lateral force acting on the steering wheel 12, the lateral force can be grasped by the axial force Taf. On the other hand, it is desirable that the torque to be input to the steering shaft 24 by the driver via the steering wheel 22 is determined according to the lateral force. Therefore, the base target torque calculation process M10 is a process of calculating the base target torque Thb * according to the lateral force grasped from the axial force Taf.

Specifically, in the base target torque calculation process M10, even if the magnitude (absolute value) of the axial force Taf is the same, the magnitude (absolute value) of the base target torque Thb * is larger than that when the vehicle speed V is small. Is a process of calculating to a smaller value. This is based on, for example, by the CPU 42 in a state where map data having the lateral acceleration and vehicle speed V grasped from the axial force Taf or the axial force Taf as input variables and the base target torque Thb * as the output variable is stored in the ROM 44 in advance. This can be achieved by performing map calculation of the target torque Thb *. Here, the map data is a set of data of discrete values of input variables and values of output variables corresponding to the values of the input variables. In the map calculation, for example, when the value of the input variable matches any of the values of the input variable of the map data, the value of the output variable of the corresponding map data is used as the calculation result, whereas when they do not match, the map is used. The processing may be performed on the value obtained by interpolating the values of a plurality of output variables included in the data as the calculation result.

The hysteresis processing M14 calculates the hysteresis correction amount This that corrects the base target torque Thb * based on the rotation angle (pinion angle θp) of the pinion shaft 24c, which is a convertible angle that can be converted into the steering angle of the steering wheel 12. It is a process to output. Specifically, the hysteresis processing M14 identifies the turning time and the turning back time of the steering wheel 22 based on the change of the pinion angle θp and the like, and the magnitude of the target steering torque Th * at the cutting time is smaller than that at the turning back time. A process of calculating the hysteresis correction amount Thys so as to be larger is included. Specifically, the hysteresis process M14 includes a process of variably setting the hysteresis correction amount This according to the vehicle speed V.

The addition process M12 is a process of calculating the target steering torque Th * by adding the hysteresis correction amount Thys to the base target torque Thb *.
The steering operation amount calculation process M16 is a process of calculating the steering operation amount Ts *, which is the operation amount for feedback-controlling the steering torque Th to the target steering torque Th *. The steering operation amount Ts * is an amount corresponding to the required torque Td for the electric motor 32 for feedback-controlling the steering torque Th to the target steering torque Th *. However, in the present embodiment, the steering operation amount Ts * is , It is an amount converted into the torque applied to the steering shaft 24.

The axial force calculation process M18 is a process of calculating the axial force Taf by adding the steering torque Th to the steering operation amount Ts *. Since the steering torque Th is the torque applied to the steering shaft 24, the axial force Taf in the present embodiment is a value obtained by converting the force applied in the axial direction of the rack shaft 26 into the torque applied to the steering shaft 24. ..

The normative model calculation process M20 is a process of calculating the pinion angle command value θp *, which is the command value of the pinion angle θp, based on the axial force Taf. Specifically, the normative model calculation process M20 is a process of calculating the pinion angle command value θp * using the model formula expressed by the following formula (c1).

Taf = K · θp * + C · θp *'+ J · θp *''… (c1)
The model expressed by the above equation (c1) is a model of the value indicated by the pinion angle θp when a torque equal to the axial force Taf is input to the steering shaft 24. In the above equation (c1), the viscosity coefficient C is a model of the friction of the electric power steering device 10, and the inertial coefficient J is a model of the inertia of the electric power steering device 10. The coefficient K is a model of specifications such as suspension and wheel alignment of a vehicle on which the electric power steering device 10 is mounted. This model is not a model that accurately represents the actual electric power steering device 10 or the vehicle on which the electric power steering device 10 is mounted, but is designed to make the behavior of the steering angle with respect to the input ideal. It is a normative model. That is, in the present embodiment, it is possible to adjust the steering feeling through the design of the normative model.

The integration process M30 is a process for calculating the integrated value Inθ of the rotation angle θm of the electric motor 32. In the present embodiment, the steering angle of the steering wheel 12 when the vehicle travels straight is set to "0", and the integrated value Inθ when the steering angle is "0" is set to "0". The conversion process M32 is a process of calculating the pinion angle θp by dividing the integrated value Inθ by the reduction ratio Km from the steering shaft 24 to the electric motor 32. When the pinion angle θp is “0”, it indicates that the vehicle is going straight, and depending on whether it is positive or negative, it is the turning angle on the right turning side or the turning angle on the left turning side. Indicates whether it is.

The angle manipulated variable calculation process M40 is a process of calculating the angle manipulated variable Tt *, which is the manipulated variable for feedback-controlling the pinion angle θp to the pinion angle command value θp *. The angle manipulation amount Tt * is an amount corresponding to the required torque Td for the electric motor 32 for feedback-controlling the pinion angle θp to the pinion angle command value θp *, but in the present embodiment, it is a torque applied to the steering shaft 24. It is the converted amount.

In addition to the angle manipulated variable Tt * and the steering torque Th, the angle manipulated variable calculation process M40 includes a disturbance observer M42 that estimates a torque affecting the pinion angle θp as a disturbance torque and uses this as the estimated disturbance torque Tlde. In the present embodiment, the estimated disturbance torque Tlde is converted into the torque applied to the steering shaft 24.

The disturbance observer M42 uses a three-row, one-column matrix L that defines the inertial coefficient Jp, the estimated value θpe of the pinion angle θp, the angle manipulation amount Tt0 *, and the observer gains l1, l2, and l3 in the following equation (c2). The estimated disturbance torque Tlde and the estimated value θpe are calculated. The inertia coefficient Jp is a model of the inertia of the electric power steering device 10, and is a value that expresses the inertia of the actual electric power steering device 10 with high accuracy as compared with the inertia coefficient J. ..

The differential calculation process M44 is a process of calculating the pinion angular velocity command value by the differential calculation of the pinion angular velocity command value θp *.

The feedback term calculation process M46 is a differential term according to the difference between the pinion angle command value θp * and the estimated value θpe, and the differential value according to the difference between the differential value of the pinion angle command value θp * and the differential value of the estimated value θpe. This is a process for calculating the feedback operation amount Ttfb, which is the sum of the terms.

The second-order differential process M48 is a process for calculating the second-order time derivative value of the pinion angle command value θp *. The feedforward term calculation process M50 is a process of calculating the feedforward manipulated variable Ttff by multiplying the output value of the second-order differential process M48 by the inertia coefficient Jp. The two-degree-of-freedom manipulated variable calculation process M52 is a process of subtracting the estimated disturbance torque Tlde from the sum of the feedback manipulated variable Ttfb and the feedforward manipulated variable Ttff to calculate the angle manipulated variable Tt0 *.

The steering torque compensation process M54 is a process of subtracting the steering torque Th from the angle manipulated variable Tt0 * to calculate the angle manipulated variable Tt * that is the output of the angle manipulated variable calculation process M40.
The addition process M60 is a process of adding the steering operation amount Ts * and the angle operation amount Tt * to calculate the required torque Td for the electric motor 32.

The conversion process M62 is a process of converting the required torque Td into the torque command value Tm *, which is the command value of the torque for the electric motor 32, by dividing the required torque Td by the reduction ratio Km.

The operation signal generation process M64 is a process of generating and outputting the operation signal MSt of the inverter 33 for controlling the torque of the electric motor 32 to the torque command value Tm *. The operation signal MSt is actually an operation signal for each arm of each leg of the inverter 33.

FIG. 3 shows the details of the steering operation amount calculation process M16.
As shown in FIG. 3, the deviation calculation process M70 is a process of subtracting the target steering torque Th * from the steering torque Th. The proportional gain setting process M72 is a process for setting the proportional gain Kp based on the vehicle speed V and the steering torque Th. This process is a process in which the CPU 42 performs a map calculation of the proportional gain Kp in a state where map data having the vehicle speed V and the steering torque Th as input variables and the proportional gain Kp as the output variable is stored in the ROM 44 in advance. The proportional term calculation process M74 is a process of calculating the proportional term Tfbp by multiplying the output value of the deviation calculation process M70 by the proportional gain Kp. The proportional gain Kp is a positive value, and when both the steering torque Th and the target steering torque Th * are positive, the larger the steering torque Th is than the target steering torque Th *, the larger the proportional term Tfbp is. Has.

The differential process M76 is a process for calculating the first-order time derivative value of the steering torque Th. The first differential gain setting process M78 is a process for setting the first differential gain Kd1 based on the vehicle speed V. Specifically, the CPU 42 performs map calculation of the first differential gain Kd1 in a state where the map data with the vehicle speed V as the input variable and the first differential gain Kd1 as the output variable is stored in the ROM 44 in advance. The first differential term calculation process M80 is a process of calculating the first differential term Tfbd1 by multiplying the output value of the differential process M76 by the first differential gain Kd1.

The second differential gain setting process M82 is a process for setting the second differential gain Kd2 based on the axial force Taf and the vehicle speed V. Specifically, the CPU 42 performs a map calculation of the second differential gain Kd2 in a state where the map data in which the axial force Taf and the vehicle speed V are input variables and the second differential gain Kd2 is the output variable is stored in the ROM 44 in advance. The second differential term calculation process M84 is a process of calculating the second differential term Tfbd2 by multiplying the output value of the differential process M76 by the second differential gain Kd2.

The differential term calculation process M86 is a process of calculating the differential term Tfbd by adding the first differential term Tfbd1 and the second differential term Tfbd2.
The addition process M88 is a process of outputting the value obtained by adding the proportional term Tfbp and the differential term Tfbd as the steering operation amount Ts *.

FIG. 4 shows a method for setting the second differential gain Kd2 by the second differential gain setting process M82. FIG. 4 shows the relationship between the axial force Taf and the second differential gain Kd2 when the vehicle speed V is constant, and when the vehicle speed V is different, the value of the second differential gain Kd2 according to the axial force Taf itself. The tendency of the change of the second differential gain Kd2 with respect to the change of the axial force Taf is the same.

As shown in FIG. 4, in the first region A1 where the magnitude of the axial force Taf is small, the value at which the second differential gain Kd2 is larger than when the axial force Taf is small (for example, Taf1) and large (for example, Taf2). Is set to. Here, in the present embodiment, in the first region A1, the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf becomes smaller as the axial force Taf increases. Therefore, in the first region A1, the second differential gain Kd2 is set to a larger value than when the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf is large and small. There is. This is a setting for suppressing disturbances such as brake vibration.

On the other hand, in the second region A2 in which the magnitude of the axial force Taf is large, the second differential gain Kd2 is set to a larger value than when the axial force Taf is large (for example, Taf4) and small (for example, Taf3). To. In addition, "Taf3> Taf2". Here, in the present embodiment, in the second region A2, the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf becomes smaller as the axial force Taf increases. Therefore, in the second region A2, the second differential gain Kd2 is set to a smaller value than when the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf is large. There is. This is a setting to ensure the stability of the system.

Here, the operation and effect of this embodiment will be described.
The CPU 42 variably sets the magnitude of the second differential gain Kd2 based on the axial force Taf. Thereby, the second differential gain Kd2 can be set so as to satisfy the requirement element for suppressing the disturbance and the requirement element for stabilizing the system.

According to the present embodiment described above, the effects described below can be further obtained.
(1) By variably setting the second differential gain Kd2 with the axial force Taf as an input, the second differential gain Kd2 is set according to the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf. It can be set variably.

(2) The target steering torque Th * was calculated based on the vehicle speed V, and the second differential gain Kd2 was variably set based on the vehicle speed V. As a result, the second differential gain Kd2 can be appropriately set in view of the fact that the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf changes according to the vehicle speed V.

(3) By variably setting the first differential gain Kd1 according to the vehicle speed V, the steering feeling can be appropriately adjusted by the first differential term Tfbd1.
(4) The proportional gain Kp was variably set according to the vehicle speed V. As a result, the proportional gain Kp can be variably set according to the increase in the magnitude of the target steering torque Th * in view of the fact that the increase in the magnitude of the target steering torque Th * changes according to the vehicle speed V. As a result, a suitable compromise between stability and responsiveness can be achieved.

(5) The proportional gain Kp was variably set according to the steering torque Th. Thereby, the steering feeling can be appropriately adjusted.
(6) The pinion angle command value θp * was calculated by the norm model calculation process M20 based on the above equation (c1) expressing the norm model, and the pinion angle θp was controlled to the pinion angle command value θp *. As a result, the steering characteristics can be adjusted by the normative model.

(7) The target steering torque Th * was set according to the sum of the steering operation amount Ts * and the steering torque Th. Here, the target torque required to improve the steering feeling by the driver tends to be determined according to the lateral force. On the other hand, since the sum of the steering operation amount Ts * and the steering torque Th can be converted into the lateral force of the vehicle, the target steering torque Th * can be calculated by determining the target steering torque Th * based on the above sum. Easy to design.

<Second embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

FIG. 5 shows the configuration of the electric power steering device 10 according to the present embodiment. Of the members shown in FIG. 5, the members corresponding to the members shown in FIG. 1 are designated by the same reference numerals for convenience.

In this embodiment, a clutch 60 capable of blocking the transmission of power to and from the steering wheel 22 is provided. That is, the pinion shaft 24c is connected to one side of the clutch 60, and the input shaft 24d connected to the steering wheel 22 is connected to the other side of the clutch 60. In the present embodiment, the input shaft 24d and the pinion shaft 24c are referred to as a steering shaft 24.

The power of the electric motor 72 is applied to the input shaft 24d via the speed reducer 70. The voltage of the inverter 74 is applied to each terminal of the electric motor 72. The drag actuator 80 is composed of an input shaft 24d, a speed reducer 70, an electric motor 72, and an inverter 74. In the present embodiment, the steering control device 40 refers to the rotation angle (steering angle θh) of the steering wheel 22 detected by the steering angle sensor 82.

FIG. 6 shows a part of the processing executed by the steering control device 40 according to the present embodiment. The process shown in FIG. 6 is realized by the CPU 42 executing the program stored in the ROM 44. In FIG. 6, the same reference numerals are given to the processes corresponding to the processes shown in FIG. 2 for convenience.

As shown in FIG. 6, in the present embodiment, in the normative model calculation process M20, a steering angle command value (steering angle command value θh *) is calculated instead of the pinion angle command value θp *. On the other hand, the steering angle ratio variable processing M90 adjusts the adjustment amount Δa for making the steering angle ratio variable, which is the ratio of the target value of the steering angle (pinion angle command value θp *) to the steering angle command value θh *, as the vehicle speed. This is a process of variably setting according to V. Specifically, the adjustment amount Δa is set so that the change in the steering angle with respect to the change in the steering angle is larger than when the vehicle speed V is low and high. The addition process M92 sets the pinion angle command value θp * by adding the adjustment amount Δa to the steering angle command value θh *.

The drag calculation process M94 is a process of calculating the torque command value Tr * of the electric motor 72 as an operation amount for feedback-controlling the steering angle θh to the steering angle command value θh *. The operation signal generation process M96 is a process of outputting operation signals MSs to the inverter 74 to operate the inverter 74 in order to control the torque of the electric motor 72 to the torque command value Tr *.

In this embodiment, the steering torque compensation process M54 is not provided, and the output of the angle manipulated variable calculation process M40 is the angle manipulated variable Tt0 *. Further, in the present embodiment, the angle manipulated variable Tt0 * output by the angle manipulated variable calculation process M40 is the required torque Td. That is, in the present embodiment, the torque command value Tm * is calculated only from the angle manipulated variable Tt0 *.

<Correspondence>
The correspondence between the matters in the above embodiment and the matters described in the column of "Means for Solving the Problem" is as follows. In the following, the correspondence is shown for each number of the solution means described in the column of "Means for solving the problem". [1] The target steering torque calculation process corresponds to the base target torque calculation process M10, the addition process M12, and the hysteresis process M14. The operation processing includes the normative model arithmetic processing M20 in FIG. 2, angle manipulation amount calculation processing M40, addition processing M60, conversion processing M62 and operation signal generation processing M64, normative model arithmetic processing M20 in FIG. 6, and steering angle ratio variable processing M90. , Addition process M92, angle operation amount calculation process M40, conversion process M62, and operation signal generation process M64. The drive circuit corresponds to the inverter 33. The differential gain corresponds to the second differential gain Kd2. The first value and the second value correspond to the values at which the axial force Taf is any two of the four Taf1, Taf2, Taf3, and Taf4. [2] Corresponds to the process of FIG. [3 to 6] Corresponds to the process of FIG. [7] The angle command value calculation process corresponds to the norm model calculation process M20 of FIG. 2, the norm model calculation process M20 of FIG. 6, the steering angle ratio variable process M90, and the addition process M92. The convertible angle corresponds to the pinion angle θp. [8] Corresponds to the process of FIG.

<Other Embodiments>
In addition, this embodiment can be implemented by changing as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

・ "About variable differential gain processing"
In the above embodiment, the relationship between the magnitude of the axial force Taf and the magnitude of the second differential gain Kd2 is reversed in the first region A1 and the second region A2, but the present invention is not limited to this. For example, in any region, when the axial force Taf is large, the second differential gain Kd2 may be set to a larger value than when it is small to ensure the stability of the system.

In the above embodiment, the second differential gain Kd2 is variably set according to the vehicle speed V and the axial force Taf, but the present invention is not limited to this. For example, the second differential gain Kd2 may be variably set according to the vehicle speed V and the target steering torque Th *. Also by this, the second differential gain Kd2 can be variably set according to the amount of increase in the magnitude of the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf. Further, since the steering torque Th is considered to be close to the target steering torque Th *, the second differential gain Kd2 may be variably set based on the steering torque Th and the vehicle speed V.

The second differential gain Kd2 is variably set based on only one of the axial force Taf, the target steering torque Th *, and the steering torque Th, without variably setting the second differential gain Kd2 according to the vehicle speed V. You may.

・ "About proportional gain variable processing"
In the above embodiment, the proportional gain Kp is variably set based on the steering torque Th and the vehicle speed V, but the present invention is not limited to this. For example, the steering torque Th and the vehicle speed V may be variably set based on only one of them.

Further, instead of the steering torque Th, the proportional gain Kp may be variably set according to the axial force Taf and the target steering torque Th *. Since the amount of increase in the target steering torque Th * with respect to the increase in the magnitude of the axial force Taf can be grasped from the steering torque Th, the axial force Taf, and the target steering torque Th *, the same as the second differential gain Kd2. , The proportional gain Kp may be variably set according to the amount of increase in the magnitude of the target steering torque Th * based on any one of these three parameters or the vehicle speed V. This makes it possible to strike a compromise between stability and responsiveness.

・ "About steering operation amount calculation processing"
In the above embodiment, the second differential gain Kd2 is set as the proportional coefficient of the first-order time derivative value of the steering torque Th, but the present invention is not limited to this, and for example, 1 is the value obtained by subtracting the target steering torque Th * from the steering torque Th. It may be a proportional coefficient of the fractional time derivative value. Even in this case, the second differential gain Kd2 can be regarded as a proportional coefficient of the first-order time differential value of the steering torque Th. Further, for example, the second differential gain Kd2 is set as the proportional coefficient of the first-order time differential value of the steering torque Th, and the third differential gain Kd3 is provided as the proportional coefficient of the first-order time differential value of the target steering torque Th *. The steering operation amount Ts * may be calculated by further adding the three differential terms. In this case, the third differential gain Kd3 may be variably set according to the same parameters as the second differential gain Kd2.

It is not essential to provide the first differential term Tfbd1.
It is not essential to calculate the steering operation amount Ts * only from the operation amount for feedback control exemplified in the above embodiment, for example, the operation amount of open loop control and the feedback exemplified in the above embodiment. It may be the sum of the operation amount for control.

-"About the required torque Td that is the input of the conversion process M62"
In FIG. 2, the sum of the angle operation amount Tt * and the steering operation amount Ts * is set as the required torque Td which is the input of the conversion process M62, but the present invention is not limited to this. For example, the angle manipulated variable Tt * may be the required torque Td that is the input of the conversion process M62. However, the required torque Td that is the input of the conversion process M62 is not limited to the amount corresponding to the angle manipulation amount Tt *. For example, the normative model calculation process M20, the angle operation amount calculation process M40, and the like in the process of FIG. 2 may be deleted, and the steering operation amount Ts * may be the required torque Td to be input to the conversion process M62.

In the process of FIG. 6, the angle manipulated variable Tt * is set to the required torque Td which is the input of the conversion process M62, but the present invention is not limited to this. For example, the sum of the angle manipulated variable Tt * and the steering manipulated variable Ts * may be the required torque Td that is the input of the conversion process M62.

"About angle command value calculation processing"
In the above embodiment, the pinion angle command value θp * and the steering angle command value θh * are calculated by inputting the axial force Taf, but the present invention is not limited to this, and for example, the steering operation amount Ts * may be input. In the above embodiment, the axial force Taf is input and the pinion angle command value θp * and the steering angle command value θh * are calculated based on the above equation (c1) and the like, but the pinion angle command value θp * and the steering angle command value are calculated. The logic (model) for calculating θh * is not limited to this.

Further, for example, in the process of FIG. 6, the rudder angle ratio variable process M90 and the addition process M92 may be deleted, and the output of the norm model calculation process M20 may be set to the steering angle command value θh * and the pinion angle command value θp *.

・ "About the disturbance observer"
In the above embodiment, the disturbance observer is configured by a simple model in which the torque acting on the steering wheel 12 is balanced with the torque proportional to the angular acceleration of the steering angle, but the present invention is not limited to this. For example, the disturbance observer may be configured by using a model in which the torque acting on the steering wheel 12 is balanced with the sum of the torque proportional to the angular acceleration of the steering angle and the torque proportional to the angular velocity of the steering angle.

The method for calculating the estimated disturbance torque Tlde is not limited to the one illustrated in the above embodiment. For example, in the processing of FIG. 2, the angle manipulation amount Tt * and the steering manipulation amount Ts * are obtained from the second-order time differential value of the pinion angle command value θp * or the second-order time differential value of the pinion angle θp multiplied by the inertia coefficient Jp. And may be calculated by subtracting the steering torque Th.

・ "About angle manipulation amount calculation processing"
In the above embodiment, the feed forward operation amount Ttff is calculated based on the second-order time derivative value of the pinion angle command value θp *, but is not limited to this, and is calculated based on, for example, the second-order time derivative value of the pinion angle θp. , It may be calculated based on the second-order time derivative value of the estimated value θpe.

In the above embodiment, the feed forward term is calculated by modeling the electric power steering device 10 with a simple model in which the torque acting on the steering wheel 12 is balanced with the torque proportional to the angular acceleration of the steering angle. However, it is not limited to this. For example, the feed forward term may be calculated using a model in which the torque acting on the steering wheel 12 is balanced with the sum of the torque proportional to the angular acceleration of the steering angle and the torque proportional to the angular velocity of the steering angle. .. This is, for example, the value obtained by multiplying the second-order time derivative value of the pinion angle command value θp * by the inertial coefficient Jp and the value obtained by multiplying the first-order time derivative value of the pinion angle command value θp * by the viscosity coefficient Cp. This can be achieved by setting the sum to the feed forward operation amount Ttff. Here, the viscosity coefficient Cp, which is a proportional coefficient of the angular velocity, is different from the viscosity coefficient C used in the normative model calculation process M20 in that the aim is different, and the actual behavior of the electric power steering device 10 is modeled with as high accuracy as possible. It is desirable to make it.

The feedback control amount in the input of the feedback term calculation process M46 is not limited to the estimated value θpe and its first-order time derivative value. For example, instead of the estimated value θpe or its first-order time derivative value, the pinion angle θp or its time derivative value itself may be used.

The feedback term calculation process M46 is not limited to the process of outputting the sum of the output values of the proportional element and the differential element. For example, the output value of the proportional element may be output, or the output value of the differential element may be output, for example. Further, for example, it may be a process of outputting the sum of at least one of the output value of the proportional element and the output value of the differential element and the output value of the integrating element. When using the output value of the integrating element, it is desirable to delete the disturbance observer. However, it is not essential to use the disturbance observer when the output value of the integrating element is not used.

・ "About convertible angle"
In the above embodiment, the pinion angle θp is used as the convertible angle, but the present invention is not limited to this. For example, it may be the steering angle itself of the steering wheel.

・ "About steering operation amount"
In the above embodiment, the steering operation amount Ts * is converted into the torque of the steering shaft 24, but the present invention is not limited to this. For example, it may be the torque of the electric motor 32. However, in that case, for example, the sum of the steering torque Th divided by the reduction ratio Km and the steering operation amount Ts * is used as the axial force Taf, or the steering operation amount Ts * multiplied by the reduction ratio Km and the steering torque Th. The sum of and is taken as the axial force Taf.

・ "About angle manipulation amount"
In the above embodiment, the angular manipulated variable Tt * is converted into the torque of the steering shaft 24, but the present invention is not limited to this. For example, it may be the torque of the electric motor 32. However, for example, when the steering operation amount Ts * is converted into the torque of the steering shaft 24, the required torque Td is the sum of the angle operation amount Tt * multiplied by the reduction ratio Km and the steering operation amount Ts *. To do.

・ "Target steering torque calculation process"
The base target torque calculation process is not limited to the process of calculating the base target torque Thb * according to the axial force Taf and the vehicle speed V. For example, the process may be a process of calculating the base target torque Thb * based only on the axial force Taf.

It is not essential to correct the base target torque Thb * with the hysteresis correction amount Thys.
・ "About the steering control device"
The steering control device is not limited to the one provided with the CPU 42 and the ROM 44 to execute software processing. For example, a dedicated hardware circuit (for example, ASIC or the like) for hardware processing at least a part of the software processed in the above embodiment may be provided. That is, the steering control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the processing may be executed by a processing circuit including at least one of one or more software processing circuits and one or more dedicated hardware circuits.

・ "About electric motors and drive circuits"
The electric motor is not limited to SPMSM, and may be IPMSM or the like. Further, the machine is not limited to the synchronous machine and may be an induction machine. Further, for example, it may be a DC motor with a brush. In that case, an H-bridge circuit may be adopted as the drive circuit.

・ "About steering actuator"
The steering actuator is not limited to the one illustrated in the above embodiment. For example, a so-called dual pinion type may be provided, which is provided with a second pinion shaft for transmitting the power of the electric motor 32 to the rack shaft 26 in addition to the pinion shaft 24c. Further, for example, the output shaft 32a of the electric motor 32 may be mechanically connected to the steering shaft 24. In that case, the steering actuator shares the steering shaft 24 and the rack and pinion mechanism 27 with the steering mechanism.

·"others"
For example, in FIG. 6, the clutch 60 may be deleted, and instead, the input shaft 24d may be mechanically connected to the pinion shaft 24c via a gear ratio variable mechanism that makes the gear ratio variable. Even in that case, the same processing as that illustrated in the case of steer-by-wire can be realized.

10 ... Electric power steering device, 12 ... Steering wheel, 16 ... Rack housing, 20 ... Steering mechanism, 22 ... Steering wheel, 24 ... Steering shaft, 24a ... Column shaft, 24b ... Intermediate shaft, 24c ... Pinion shaft, 24d ... Input shaft, 26 ... Rack shaft, 27 ... Rack and pinion mechanism, 28 ... Tie rod, 30 ... Steering actuator, 32 ... Electric motor, 32a ... Output shaft, 33 ... Inverter, 34 ... Ball screw mechanism, 36 ... Belt type reduction mechanism , 40 ... Steering control device, 42 ... CPU, 44 ... ROM, 46 ... Peripheral circuit, 48 ... Communication line, 50 ... Torque sensor, 52 ... Vehicle speed sensor, 54 ... Rotation angle sensor, 60 ... Clutch, 70 ... Reducer , 72 ... Electric, 74 ... Inverter, 80 ... Torque actuator, 82 ... Steering angle sensor.

Claims (8)

The operation target is a steering actuator that has a built-in electric motor and steers the steering wheel.
Target steering torque calculation processing that calculates the target steering torque, which is the target value of the steering torque input by the driver, and
Calculates the steering operation amount, which is the operation amount of the electric motor for steering the steering wheel in order to feedback control the steering torque to the target steering torque, which is the operation amount that can be converted into the torque required for the electric motor. Steering operation amount calculation processing to be performed and
The operation process of operating the drive circuit of the electric motor based on the steering operation amount is executed.
The target steering torque calculation process is a process of calculating the target steering torque based on the sum of the amounts obtained by converting the steering operation amount and the steering torque into a force acting on the same object.
The steering operation amount calculation process is a process of calculating the steering operation amount based on a process of adding a differential term proportional to a time change of the steering torque to a proportional term based on the difference between the steering torque and the target steering torque. And the differential gain, which is the proportional coefficient of the time change in the differential term, is obtained when the amount of increase in the magnitude of the target steering torque with respect to the amount of increase in the magnitude of the sum is the first value and the second value. A steering control device that includes variable differential gain processing that sets different values from each other. In the differential gain variable processing, among the regions related to the magnitude of the sum and the target steering torque, the differentiation is larger than when the increase in the magnitude of the target steering torque is large in the first region. The process of setting the gain to a large value is executed, and in the second region where the magnitude of the sum is larger than that of the first region, the differentiation is larger than when the increase in the magnitude of the target steering torque is large. The steering control device according to claim 1, wherein the process of reducing the gain to a small value is executed. The steering control device according to claim 1 or 2, wherein the differential gain variable processing includes a processing of variably setting the differential gain by inputting a sum of quantities converted into forces acting on the same object as an input. The target steering torque calculation process is a process of calculating the target steering torque based on the vehicle speed in addition to the sum of the amounts converted into the forces acting on the same object.
The steering control device according to claim 1, wherein the differential gain variable processing includes a processing of variably setting the differential gain with the vehicle speed as an input. The item according to any one of claims 1 to 4, wherein the proportional gain variable processing for variably setting the proportional gain, which is the proportional coefficient of the difference between the steering torque and the target steering torque in the proportional term, is set according to the vehicle speed. Steering control device. Any one of claims 1 to 4 for executing proportional gain variable processing in which the proportional gain, which is the proportional coefficient of the difference between the steering torque and the target steering torque in the proportional term, is variably set according to the steering torque. The steering control device according to. The operation process is
An angle command value calculation process for calculating an angle command value which is a convertible angle command value that can be converted into a steering angle of the steering wheel according to the steering operation amount, and
The angle operation amount calculation process for calculating the angle operation amount which is the operation amount for feedback-controlling the convertible angle to the angle command value and which is the operation amount which can be converted into the torque required for the electric motor.
The steering control device according to any one of claims 1 to 6, further comprising an operation signal generation process for generating an operation signal for operating the drive circuit based on the angle operation amount. The steering control device according to claim 7, wherein the operation signal generation process is a process of generating the operation signal based on the angle operation amount without inputting the steering operation amount.