KR20180120826A - Motor driven power steering system and control method thereof - Google Patents

Abstract

According to the present invention, disclosed are an electric steering device and a control method thereof. The electric steering device of the present invention comprises: a vehicle speed sensor detecting a vehicle speed of a vehicle; a yaw rate sensor detecting an inclined state of the vehicle to output a yaw rate value; a steering detecting portion detecting a steering state of a driver; and a recovery control portion estimating a recovery force based on the vehicle speed, the yaw rate value, and the steering state each inputted from the vehicle speed sensor, the yaw rate sensor, and the steering detecting portion, when a failure of a torque sensor is detected, and outputting a final recovery force by improving reactivity in accordance with steering intention.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electric power steering system,

More particularly, the present invention relates to an electric steering apparatus and a control method thereof, and more particularly, to an electric steering apparatus and a control method thereof that are capable of estimating a restoring force of a vehicle using a yaw rate value of a vehicle when a steering sensor can not be steered due to a failure of a torque sensor, And more particularly, to an electric steering apparatus and a control method thereof that enable steering performance by improving the responsiveness of a vehicle.

Generally, Motor Driven Power Steering (MDPS) uses electric motors to provide auxiliary torque in the direction the driver steers, thereby making handling lighter.

Unlike the conventional hydraulic power steering (HPS), the electric steering system can improve the steering performance and the steering feeling by automatically controlling the operation of the electric motor according to the driving conditions of the vehicle.

At this time, the electric steering apparatus includes a torque sensor for measuring a steering torque of the driver input to the steering wheel, a steering angle sensor for measuring the steering angle of the steering wheel, and a vehicle speed sensor for measuring the vehicle speed.

On the other hand, if the driver determines that the turning has been performed after applying the steering input at the turning of the vehicle, the driver slowly releases his or her hand from the steering wheel, but the steering wheel returns to the center by the restoring action.

The restoring action of the steering wheel is generated by the self-alignment torque of the tire, and is a useful function when the vehicle speed of the vehicle is normally turning from 5 km / h to 30 km / h.

However, the restoring force (Self Alignment Torque) applied to the steering wheel is not sufficient to return the steering wheel to the center as the steering residual angle remains due to the frictional action of the steering system.

Therefore, in order to completely return the steering wheel to the center, it is necessary to additionally provide a function for assisting the restoration operation.

Therefore, the electric power steering system improves the restoration performance by restoring the steering wheel by applying the restoring torque calculated based on the steering angle.

Related prior art is "Steering Restoration Method of Electric Steering Device" of Korean Patent Publication No. 2010-0114995 (Oct. 27, 2010).

In order to enable the steering according to the driver's steering intention in such an electric steering apparatus, the torque amount of the driver sensed by the torque sensor must be used. Therefore, when the torque sensor fails, the electric steering apparatus is switched to the manual mode, .

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an electric steering system in which, when a steering sensor can not be steered due to a failure of a torque sensor, And to improve the responsiveness of the vehicle due to the steering intention of the driver so as to enable the steering, and a control method thereof.

An electric steering apparatus according to an aspect of the present invention includes: a vehicle speed sensor for detecting a vehicle speed of a vehicle; A yaw rate sensor for detecting a tilted state of the vehicle and outputting a yaw rate value; A steering angle sensor for sensing a steering state of the driver; And the torque sensor are detected, the restoring force is estimated based on the vehicle speed, the yaw rate value and the steering state respectively inputted from the vehicle speed sensor, the yaw rate sensor and the steering angle sensor, and the reactivity is improved according to the steering will, And a restoration control unit.

In the present invention, the steering angle sensor is one of a steering angle sensor for measuring the steering angle of the steering wheel and a motor angle sensor for measuring the motor angle of the drive motor.

In the present invention, the restoration controller estimates a restoration force by multiplying a yaw rate, a vehicle speed and a restoration constant; And a reactive processing unit for multiplying the steering angle velocity, the slip constant, the vehicle speed and the restitution constant calculated from the steering angle to improve the reactivity of the vehicle.

In the present invention, the restoration controller estimates a restoration force by multiplying a yaw rate, a vehicle speed and a restoration constant; And a reactive processing unit for multiplying the motor angular velocity, slip constant, vehicle speed and restitution constant calculated from the motor angle to improve the reactivity of the vehicle.

In the present invention, the restitution constant is a gain value per vehicle speed obtained through a vehicle running test.

In the present invention, the slip constant is a gain value according to the road surface condition.

In another aspect of the present invention, there is provided a control method of an electric power steering apparatus, comprising: receiving a vehicle speed, a yaw rate value and a steering state from a vehicle speed sensor, a yaw rate sensor and a steering angle sensor, ; Estimating a restoration force based on a vehicle speed and a yaw rate; And the restoration control unit processes the reactivity of the restoring force according to the steering effort based on the vehicle speed, the yaw rate value, and the steering state, and outputs the final restoring force.

In the present invention, the restoration control unit estimates the restoration force by multiplying the yaw rate, the vehicle speed, and the restoration constant by the restoration control unit.

In the present invention, the restitution constant is a gain value per vehicle speed obtained through a vehicle running test.

The present invention is characterized in that the steering state is any one of a steering angle input from a steering angle sensor of a steering sensor and an angle of a motor input from a motor angle sensor.

The step of processing the reactivity of the restoring force in the present invention is characterized in that the restoring control section multiplies the steering angle velocity, the slip constant, the vehicle speed and the restitution constant calculated from the steering angle to improve the reactivity of the vehicle.

The step of processing the responsiveness of the restoring force in the present invention is characterized in that the restoration control section multiplies the angular speed of the motor, the slip constant, the vehicle speed and the restitution constant calculated from the motor angle to improve the responsiveness of the vehicle.

In the present invention, the slip constant is a gain value according to the road surface condition.

An electric power steering apparatus and a control method thereof according to an aspect of the present invention estimate a restoration force of a vehicle using a yaw rate value of a vehicle when a steering sensor fails due to a failure of a torque sensor in an electric steering system, It is possible to improve the responsiveness and output the restoring force so that the steering can be performed even in the fault state of the torque sensor.

1 is a block diagram illustrating an electric power steering apparatus according to an embodiment of the present invention.
2 is a graph illustrating restoration constants in an electric steering system according to an embodiment of the present invention.
3 is a graph showing slip constants in an electric steering system according to an embodiment of the present invention.
4 is a graph showing a result of a running test by an electric power steering apparatus according to an embodiment of the present invention.
5 is a flowchart illustrating a method of controlling an electric steering system according to an embodiment of the present invention.

Hereinafter, an electric steering apparatus and a control method thereof according to the present invention will be described with reference to the accompanying drawings. In this process, the thicknesses of the lines and the sizes of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

FIG. 1 is a block diagram illustrating an electric steering system according to an embodiment of the present invention. FIG. 2 is a graph illustrating restoration constants in an electric steering system according to an embodiment of the present invention. FIG. FIG. 4 is a graph showing a running test result of an electric power steering apparatus according to an embodiment of the present invention. FIG. 4 is a graph showing slip constants in an electric power steering apparatus according to an embodiment.

FIG. 1 is a block diagram illustrating an electric steering system according to an embodiment of the present invention. The steering system includes a vehicle speed sensor 10, a yaw rate sensor 20, a steering angle sensor 30, and a restoration control unit 40.

The vehicle speed sensor 10 senses the vehicle speed of the vehicle and outputs it to the restoration control unit 40.

The yaw rate sensor 20 senses the tilted state of the vehicle and outputs the yaw rate value to the restoration control unit 40.

The torque sensor (not shown) detects the torque applied to the steering shaft (not shown) when the driver operates the steering wheel (not shown) to turn left or right or change the lane, Thereby making it possible to generate a restoring force in an electric steering system.

However, in the present invention, in order to estimate the restoring force in the case of failure of the torque sensor, the present embodiment will exemplify the case where the torque sensor is not applied.

The steering sensing unit 30 measures the steering state of the driver and outputs the measured steering state to the restoration control unit 40.

In the present embodiment, the steering sensing unit 30 may be any one of the steering angle sensor 32 and the motor angle sensor 34.

The steering angle sensor 32 measures the steering angle at which the steering wheel is steered by the driver and the motor angle sensor 34 measures the motor angle at which the driving motor (not shown) of the electric steering system rotates in accordance with the steering of the driver .

Therefore, in the present embodiment, the steering condition of the driver can be measured through the steering angle and the motor angle measured from the steering angle sensor 32 and the motor angle sensor 34. [

When a failure of the torque sensor is detected, the restoration control unit 40 restores the restoring force based on the vehicle speed, the yaw rate value, and the steering state inputted from the vehicle speed sensor 10, the yaw rate sensor 20 and the steering angle sensor 30 And the final restoring force can be outputted by improving the reactivity according to the steering intention.

Here, the restoration control unit 40 may include a restoring force estimating unit 42 for estimating the restoring force and a reactive processing unit 44 for improving the reactivity of the vehicle.

In other words, the restoring force estimating unit 42 can estimate the restoring force by multiplying the yaw rate, the vehicle speed and the restitution constant, and the reactive processing unit 44 calculates the slip constant, the vehicle speed, and the restitution constant in the angular speed, which is the steering speed according to the driver's steering intention The reactivity of the vehicle can be improved.

Here, the angular velocity may be the steering angle velocity calculated by differentiating the steering angle inputted in the steered state, or the motor angular velocity calculated by differentiating the motor angle.

The restoration constant F_SAT is a gain value per vehicle speed obtained through a vehicle running test and has characteristics as shown in Fig. 2 with respect to the vehicle speed V. Fig.

The slip coefficient F_Slip is a gain value according to the road surface state and has characteristics as shown in FIG. 3 for angular velocity.

The final restoration force (T_SAT) output from the restoration control unit 40 can be defined as shown in Equation (1).

Here, T_SAT is a final restoring force, F_SAT is a restitution constant, V is a vehicle speed,? Is a yaw rate value, A is a steering angle, and F_Slip is a slip constant.

At this time, when the motor angle is input as the steering state, A can be calculated by applying the motor angle.

This is because when the driver rotates the steering wheel when the driving motor of the electric steering apparatus is installed on the steering shaft to rotate the steering shaft, the steering angle speed due to the rotation of the steering shaft and the angular speed of the motor due to the rotation of the driving motor are in a corresponding relationship .

As a result of performing the running test on the electric power steering apparatus according to the present invention and verifying its effectiveness, it can be seen that the steering force can be estimated by estimating the restoring force based on the yaw rate value as shown in FIG. 4 (a). That is, even if the torque sensor fails, the restoring force can be estimated based on the yaw rate value, and the steering response can be improved by improving the responsiveness of the vehicle by the steering intention of the driver.

Also, when comparing the waveforms before and after the failure of the torque sensor, the auxiliary torque required in the electric steering system is about -11.0 Nm to 11.0 Nm when the torque sensor operates normally as in (B). The assist torque required here can be expressed by the sum of the driver's torque and the motor torque.

Then, when the torque sensor fails in the same vehicle speed as in (C), the necessary assist torque calculated from the restoring force estimated by the restoration control section is about -13.0 Nm to 13.0 Nm, which is slightly larger than before the failure of the torque sensor, have.

As described above, according to the electric power steering apparatus according to the embodiment of the present invention, when the steering is impossible due to the failure of the torque sensor in the electric steering system, the restoring force of the vehicle is estimated using the yaw rate value of the vehicle, So that steering can be performed even in a fault state of the torque sensor.

5 is a flowchart illustrating a method of controlling an electric steering system according to an embodiment of the present invention.

As shown in FIG. 5, in the control method of the electric power steering apparatus according to an embodiment of the present invention, the restoration control unit 40 determines whether the torque sensor (not shown) is malfunctioning (S10).

If the torque sensor is failed in step S10, the restoration controller 40 receives the vehicle speed, the yaw rate, and the steering state from the vehicle speed sensor 10, the yaw rate sensor 20, and the steering angle sensor 30, respectively (S20) .

The present invention is an invention for estimating a restoring force using a yaw rate value in the case of a failure of a torque sensor, and terminates in order to calculate a restoring force based on a torque sensor when the torque sensor is normal.

After receiving the vehicle speed, the yaw rate value, and the steering state in step S20, the restoration control unit 40 estimates the restoration force based on the vehicle speed and the yaw rate value (S30).

At this time, the steering state may include the steering angle measured from the steering angle sensor 32 of the steering sensing unit 30, or the motor angle measured from the motor angle sensor 34.

Therefore, the restoration controller 40 can estimate the restoration force by multiplying the yaw rate, the vehicle speed, and the restoration constant.

At this time, the restitution constant (F_SAT) may have the same characteristic as the graph shown in FIG. 2 as the gain value per vehicle speed obtained through the vehicle running test.

In addition, the restoration control unit 40 processes the responsiveness according to the driver's will to improve the responsiveness of the vehicle to the restoring force (S40).

Here, the restoration control unit 40 can improve the reactivity of the vehicle by multiplying the angular velocity, the slip constant, the vehicle speed, and the restoration constant.

Here, the angular velocity may be the steering angle velocity calculated by differentiating the steering angle inputted in the steered state, or the motor angular velocity calculated by differentiating the motor angle.

The slip coefficient F_Slip is a gain value according to the road surface state and may have characteristics as shown in FIG. 3 for the angular velocity.

Thereafter, the restoration control unit 40 outputs the final restoring force T_SAT by summing up the estimated restoring force and the result of improving the reactivity of the restoring force (S50).

The final restoration force (T_SAT) output from the restoration control unit 40 can be defined as in Equation (2).

Here, T_SAT is a final restoring force, F_SAT is a restitution constant, V is a vehicle speed,? Is a yaw rate value, A is a steering angle, and F_Slip is a slip constant.

At this time, when the motor angle is input as the steering state, A can be calculated by applying the motor angle.

This is because when the driver rotates the steering wheel when the driving motor of the electric steering apparatus is installed on the steering shaft to rotate the steering shaft, the steering angle speed due to the rotation of the steering shaft and the angular speed of the motor due to the rotation of the driving motor are in a corresponding relationship .

As described above, according to the control method of the electric power steering apparatus according to the embodiment of the present invention, when the steering is impossible due to the failure of the torque sensor in the electric steering system, the restoring force of the vehicle is estimated using the yaw rate value of the vehicle, It is possible to improve the responsiveness of the vehicle by the steering effort and to output the restoring force, thereby making it possible to steer the vehicle even in the failure state of the torque sensor.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. I will understand.

Accordingly, the true scope of the present invention should be determined by the following claims.

10: vehicle speed sensor 20: yaw rate sensor
30: steering sensor 32: steering angle sensor
34: motor angle sensor 40: restoration control section
42: restoring force estimating unit 44:

Claims (13)

A vehicle speed sensor for detecting a vehicle speed of the vehicle;
A yaw rate sensor for detecting a tilted state of the vehicle and outputting a yaw rate value;
A steering angle sensor for sensing a steering state of the driver; And
Estimating a restoring force based on the vehicle speed, the yaw rate value, and the steering state respectively input from the vehicle speed sensor, the yaw rate sensor, and the steering angle sensing unit, when the failure of the torque sensor is detected, And outputting a final restoring force to the steering wheel.
The electric steering system according to claim 1, wherein the steering sensor is any one of a steering angle sensor for measuring a steering angle of the steering wheel and a motor angle sensor for measuring a motor angle of the drive motor.
[Claim 3] The system of claim 2, wherein the restoration controller estimates the restoration force by multiplying the yaw rate, the vehicle speed and the restoration constant, And
And a reactive processing unit for multiplying the steering angle velocity and the slip constant calculated from the steering angle by the vehicle speed and the restitution constant to improve reactivity of the vehicle.
[Claim 3] The system of claim 2, wherein the restoration controller estimates the restoration force by multiplying the yaw rate, the vehicle speed and the restoration constant, And
And a reactive processing unit for multiplying the angular speed of the motor and the slip constant calculated from the motor angle by the vehicle speed and the restitution constant to improve the reactivity of the vehicle.
The electric steering system according to claim 3 or 4, wherein the restitution constant is a gain value per vehicle speed obtained through a vehicle running test.
The electric steering system according to claim 3 or 4, wherein the slip constant is a gain value according to a road surface condition.
Receiving a vehicle speed, a yaw rate value, and a steering state from the vehicle speed sensor, the yaw rate sensor, and the steering angle sensing unit when the restoration control unit detects a failure of the torque sensor;
Estimating a restoring force based on the vehicle speed and the yaw rate; And
And outputting a final restoring force by processing the reactivity of the restoring force according to the steering intention based on the vehicle speed, the yaw rate value, and the steering state.
8. The method according to claim 7, wherein the restoring force estimating step estimates the restoring force by multiplying the yaw rate, the vehicle speed and the restitution constant by the restoration controller.
8. The method according to claim 7, wherein the restoration constant is a gain value per vehicle speed obtained through a vehicle running test.
8. The method according to claim 7, wherein the steering state is one of a steering angle input from a steering angle sensor of the steering angle sensor and an angle of a motor input from a motor angle sensor.
11. The method of claim 10, wherein the step of processing the reactivity of the restoring force comprises: increasing the steering angle, the slip constant, the vehicle speed and the restitution constant calculated from the steering angle to improve the responsiveness of the vehicle. A method of controlling a steering device.
11. The method of claim 10, wherein the step of processing the responsiveness of the restoring force comprises: increasing the motor angular speed and the slip constant calculated from the motor angle by the restoration control unit, and increasing the reactivity of the vehicle by multiplying the vehicle speed and the restoration constant Control method of electric steering system.
The control method of an electric steering system according to claim 11 or 12, wherein the slip constant is a gain value according to a road surface condition.

Images