WO2020066183A1

WO2020066183A1 - Steering control device and power steering device

Info

Publication number: WO2020066183A1
Application number: PCT/JP2019/025351
Authority: WO
Inventors: 漢宇孫; 遠藤　修司
Original assignee: 日本電産株式会社
Priority date: 2018-09-26
Filing date: 2019-06-26
Publication date: 2020-04-02
Also published as: JPWO2020066183A1; CN112770960B; DE112019004813T5; CN112770960A; JP7342876B2

Abstract

One aspect of a steering control device is a steering control device which controls the rotation angle of a motor which drives a steering mechanism in accordance with the rotation angle of a steering wheel, the steering control device comprising: a disturbance absorber which calculates a steering reaction torque generated in accordance with a change in a steering angle by the steering mechanism; and a motor control unit which reduces a difference between a target steering angle and the steering angle in the steering mechanism by driving the motor with the rotation angle of the steering wheel and the steering reaction torque as a command value.

Description

Steering control device and power steering device

The present invention relates to a steering control device and a power steering device.

BACKGROUND ART Conventionally, a steering control device that performs steering control on a power steering device has been known. Conventional steering control is mainly assist control.

For example, a control device disclosed in Patent Document 1 calculates a current command value that is a control target of a motor based on a steering torque detected by a torque sensor, and calculates a current alignment value based on a self-aligning torque estimated by a disturbance observer. To define the steering reaction force and feed back to the steering torque.

JP 2003-200844 A

In a control device as disclosed in Patent Document 1, the provision of a torque feedback loop increases the degree of freedom in designing a controller, and realizes system stability and processing for road surface information and disturbance information.

However, the performance of following the target torque due to the torque feedback is affected by the loss torque and the torque ripple of the motor. In order to suppress such an effect, a complicated compensation process is required. Further, the design of the compensator is not easy due to the influence of manufacturing variations and aging of the motor. Therefore, an object of the present invention is to perform steering control with little influence of torque ripple.

One aspect of a steering control device according to the present invention is a steering control device that controls a rotation angle of a motor that drives a steering mechanism according to a rotation angle of a steering wheel, wherein a steering reaction torque generated when the steering mechanism changes the steering angle. And a motor control unit that reduces the difference between the target steering angle and the steering angle in the steering mechanism by driving the motor with the rotation angle of the steering wheel and the steering reaction torque as a command value. , Is provided.

One embodiment of a power steering device according to the present invention includes the steering control device, a motor controlled by the steering control device, and a power steering mechanism driven by the motor.

According to the present invention, it is possible to perform steering control with little influence of torque ripple.

FIG. 1 is a schematic diagram showing an embodiment of the power steering device of the present invention. FIG. 2 is a block diagram illustrating a configuration of the electric power steering device. FIG. 3 is a diagram illustrating a modified example of the steering control device. FIG. 4 is a diagram illustrating another modified example of the steering control device. FIG. 5 is a diagram showing a modification of the electric power steering device.

Hereinafter, embodiments of a steering control device and a power steering device according to the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following description from being unnecessarily redundant and to make it easier for those skilled in the art to understand, a detailed description more than necessary may be omitted. For example, a detailed description of a well-known item or a redundant description of substantially the same configuration may be omitted. FIG. 1 is a schematic diagram showing an embodiment of the power steering device of the present invention.

As shown in FIG. 1, in the present embodiment, a column type electric power steering device is exemplified. The electric power steering device 9 is mounted on a steering mechanism of a vehicle wheel. The electric power steering device 9 is a column-type power steering device that directly reduces a steering force by the power of a steering control device 1 having a built-in motor. The electric power steering device 9 includes the steering control device 1, a steering shaft 914, and an axle 913.

The steering shaft 914 transmits the input torque transmitted from the handle 911 via the torsion bar 915 to the axle 913 having the wheels 912. In other words, the handle 911 applies a torque to the steering mechanism including the wheel 912, the axle 913, and the steering shaft 914 via the torsion bar 915.

The power of the steering control device 1 is transmitted to the steering shaft 914 via gears or the like. The motor used in the column-type electric power steering device 9 is provided inside an engine room (not shown). Although the electric power steering device 9 shown in FIG. 1 is a column type as an example, the power steering device of the present invention may be a rack type.

The steering angle θh, which is the rotation angle of the handle 911, is detected by the angle sensor 916. The value detected by the angle sensor 916 is input to the steering control device 1 and used for calculating the target output of the steering control device 1. The torque transmitted from the torsion bar 915 to the steering shaft 914 is detected by a torque sensor 917. The value detected by the torque sensor 917 is also input to the steering control device 1 and used for calculating the target output of the steering control device 1.

When the steering torque transmitted from the handle 911 via the torsion bar 915 and the assist torque by the power of the steering control device 1 are applied to the steering shaft 914, a steering angle θs, which is the rotation angle of the steering shaft 914, is generated. FIG. 2 is a block diagram illustrating a configuration of the electric power steering device 9. In FIG. 2, θh indicates a steering angle, θs indicates a steering angle, _Ktor indicates a torsion coefficient of the torsion bar 915, and STG (s) indicates a steering characteristic.

Due to the difference between the steering angle θh and the steering angle θs of the handle 911, the torsion bar 915 is twisted to generate torque. The steering angle θh is detected by the angle sensor 916 and is input to the steering control device 1. The torque generated in the torsion bar 915 is detected by the torque sensor 917 and is input to the steering control device 1.

The steering control device 1 includes a motor 10. The motor 10 is a so-called electromechanical motor, and receives a command value representing a target output torque and outputs the output torque. The steering control device 1 corresponds to an embodiment of a steering control device that controls a rotation angle of a motor 10 that drives a steering mechanism according to a rotation angle of a steering wheel 911.

The torque generated in the torsion bar 915, the output torque of the motor 10, and the torque of the disturbance D (s) are applied to the steering mechanism including the wheels 912 to the steering shaft 914 and exhibiting the steering characteristic STG (s). The steering angle θs is generated by the sum of the torques. The disturbance D (s) applied to the steering mechanism is mainly a steering reaction torque generated when the steering angle (steering angle θs) is changed by the steering mechanism or a torque given to the wheels 912 by irregularities on the ground. It works in a direction opposite to the steering force and the torque of the motor 10. The steering reaction torque includes a self-aligning torque (SAT) and a torque associated with a frictional force between the wheel 912 and the ground. The steering control device 1 drives the motor 10 based on the steering angle θh to bring the steering angle θs closer to the steering angle θh.

The steering control device 1 includes an angle feedback unit 21, a target steering angle estimation unit 22, a steering reaction torque estimation unit 23, and a disturbance observer 30. The disturbance observer 30 includes a motor torque calculation unit 31, a steering torque estimation unit 32, and a filter 33.

The drive current value Imotor of the motor 10, the detection value of the torque sensor 917, and the steering angle θs are input to the disturbance observer 30. Here, the steering angle θs is obtained from the rotation speed of the motor 10 detected by a rotation sensor provided in the motor 10.

The rotation shaft (output shaft) of the motor 10 and the steering shaft 914 are mutually connected via a reduction gear or the like. Therefore, regardless of whether the torque for rotating the steering shaft 914 is the torque by the motor 10 or another torque, the motor 10 and the steering shaft 914 always rotate together. Therefore, the steering angle θs is calculated from the rotation speed of the motor 10 based on the gear ratio and the like.

The motor torque calculator 31 of the disturbance observer 30 inputs the drive current value Imotor of the motor 10 to the characteristic K of the motor 10 to calculate the output torque of the motor 10. However, the torque calculated by the motor torque calculator 31 is a torque used for steering among the output torque of the motor 10.

Further, the steering torque estimator 32 of the disturbance observer 30 calculates the total torque applied to the steering system by inputting the steering angle θs to the inverse characteristic of the steering characteristic STG (s).

The estimated value of the disturbance D (s) is obtained by adding the calculated value of the motor torque calculating unit 31 to the detected value of the torque sensor 917 and further subtracting the calculated value of the steering torque estimating unit 32. Since the estimated value includes various disturbance components, the disturbance observer 30 calculates a self-aligning torque (SAT) of the steering reaction torque by performing a filter process using the filter 33.

The self-aligning torque (SAT) calculated by the disturbance observer 30 is input to the steering reaction torque estimation unit 23, and is converted into a steering reaction torque Tk generated in the steering wheel 911 based on a specific conversion characteristic.

The combination of the disturbance observer 30 and the steering reaction torque estimation unit 23 shown in FIG. 2 corresponds to an example of the disturbance observer according to the present invention. In the present embodiment, the steering reaction force torque Tk is calculated using the detection value of the torque sensor 917 corresponding to the measured value of the torque applied to the steering mechanism by the rotation of the handle 911. Therefore, the calculation accuracy of the steering reaction torque Tk is high.

The target steering angle estimating unit 22 estimates the target steering angle θs0 based on the steering reaction torque Tk obtained by the steering reaction torque estimating unit 23 and the steering angle θh detected by the angle sensor 916. The estimation of the target steering angle θs0 is obtained by the following equations (1) and (2).

Δθ × K _tor = Tk (1)

θs0 = θh + Δθ (2)

The difference between the target steering angle θs0 and the steering angle θs estimated in this way is input to the angle feedback unit 21, and the larger the difference, the larger the torque is calculated. The command value representing the calculated torque is input to the motor 10 to generate the assist torque.

Since the angle component Δθ added to the steering angle θh in the above equation (2) is the angle component Δθ added to maintain the current steering angle θh against the steering reaction torque Tk, the steering control device is ultimately completed. In 1, the angle control for reducing the difference between the steering angle θs and the steering angle θh is performed. Further, since the target steering angle θs0 is estimated using the above equation (1) including the torsion bar 915's torsion coefficient K _tor , the amount of torsion of the torsion bar 915 is suppressed as a result of the angle control.

The combination of the angle feedback unit 21 and the target steering angle estimating unit 22 drives the motor 10 with the rotation angle of the steering wheel 911 (steering angle θh) and the steering reaction torque Tk as command values, thereby setting the target steering angle θs0. And a steering angle control unit that reduces the difference between the steering angle and the steering angle of the steering mechanism (the steering angle θs).

As described above, since the steering control device 1 performs the angle control, the influence of the cogging torque depending on the rotation angle of the motor 10 is smaller than that of the torque control. Further, under the angle control, the compensation of the torque ripple is easier than the torque control. For this reason, in the steering control device 1 of the present embodiment, the influence of the torque ripple on the steering control is small. Then, in the electric power steering device 9 of the present embodiment, smooth power assist is realized. Next, a modified example of the electric power steering device 9 and the steering control device 1 will be described. FIG. 3 is a diagram showing a modification of the steering control device 1. As shown in FIG.

In the modified example shown in FIG. 3, a speed loop unit 24 is provided between the angle feedback unit 21 of the steering control device 1 and the motor 10. The speed loop unit 24 performs a feedforward control in which a loss torque generated depending on the rotation speed of the motor 10 such as friction is calculated, and a compensation value for compensating the loss torque is input to the motor 10.

The motor 10 outputs the total torque of the torque indicated by the command value input from the angle feedback unit 21 and the torque indicated by the compensation value input from the speed loop unit 24. Thus, power assist in which loss torque due to friction or the like is compensated is realized. FIG. 4 is a diagram showing another modified example of the steering control device 1.

In the modification shown in FIG. 4, the disturbance estimator 34 is provided in the disturbance observer 30 of the steering control device 1. The torque estimating unit 34 calculates the torque applied to the steering mechanism via the torsion bar 915 by the rotation of the steering wheel 911, the steering angle θs calculated from the rotation speed of the motor 10, and the steering angle detected by the angle sensor 916. The estimation is performed based on θh and the torsion bar 915 torsion coefficient K _tor . By estimating the torque in this way, a torque sensor is not required, and the configuration around the steering is simplified. FIG. 5 is a diagram illustrating a modification of the electric power steering device 9.

The modification shown in FIG. 5 is a so-called steer-by-wire electric power steering device 9 in which a steering wheel 911 and a steering shaft 914 are physically separated. That is, the handle 911 is in a state where the physical transmission path of the torque is separated from the steering mechanism. Therefore, there is no physical torque transmission from the handle 911 to the steering mechanism.

The steering angle θh of the steering wheel 911 is detected by the angle sensor 916 and is input to the steering control device 1. In the modified example shown in FIG. 5, the steering torque for the steering shaft 914 is generated by the motor 10 in the steering control device 1. In order to give the driver a response to the steering wheel operation, a motor not shown generates a torque corresponding to the steering reaction torque estimated by the steering reaction torque estimating unit 23 and applies the generated torque to the steering wheel 911. .

Further, it is preferable that the steering control device 1 provided in the electric power steering device 9 of the modified example shown in FIG. 5 is a steering control device 1 having feedforward control as shown in FIG. By performing the feedforward control described above, the steering mechanism exhibits a natural response to the operation of the steering wheel 911.

In such a steer-by-wire electric power steering device 9, since the torsion bar does not exist and the torque which is the control target of the torque control is not generated, the above-described angle control is more useful than the torque control.

In the above description, an example is shown in which the motor 10 is built in the steering control device 1. However, the steering control device of the present invention may be a device on the control side without a built-in motor.

The above-described embodiments and modifications are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1: steering control device 9: electric power steering device 911: steering wheel 912: wheels 913: axle 914: steering shaft 915: torsion bar 916: angle sensor 917: torque sensor 10: motor 21: angle feedback unit 22: target steering angle estimation Unit 23: steering reaction torque estimation unit 24: speed loop unit 30: disturbance observer 31: motor torque calculation unit 32: steering torque estimation unit 33: filter 34: torque estimation unit

Claims

In a steering control device that controls a rotation angle of a motor that drives a steering mechanism according to a rotation angle of a steering wheel,

A disturbance observer that calculates a steering reaction torque generated in accordance with a change in the steering angle by the steering mechanism;

A steering angle control unit that reduces a difference between a target steering angle and a steering angle in the steering mechanism by driving the motor with the rotation angle of the steering wheel and the steering reaction torque as a command value;

A steering control device comprising:
The steering control device according to claim 1, further comprising a feedforward control unit that performs feedforward control on the motor with a control amount dependent on a rotation speed of the motor.
The handle applies torque to the steering mechanism via a torsion bar,

The steering control device according to claim 1, further comprising a target steering angle calculation unit that calculates the target steering angle using a torsional coefficient of the torsion bar.
The steering control device according to claim 3, wherein the disturbance observer calculates the steering reaction torque by using a measured value of a torque applied to the steering mechanism by rotation of the steering wheel.
The steering control device according to claim 3, wherein the disturbance observer calculates the steering reaction torque by using an estimated value of a torque applied to the steering mechanism by rotation of the steering wheel.
The steering control device according to claim 2, wherein a physical transmission path of torque is separated from the steering mechanism with respect to the steering mechanism.
A steering control device according to any one of claims 1 to 6,

A motor whose driving is controlled by the steering control device;

A power steering mechanism driven by the motor;

A power steering device comprising: