JPH06278637A - Power steering control device - Google Patents

Abstract

PURPOSE:To reduce hysteresis and friction feeling by determining return side assist gain lower than turn side assist gain which is determined by speed in the case of detecting return of the steering wheel and applying a corresponding electric current on an electric motor in a controller for a power steering device for performing power assist. CONSTITUTION:A steering wheel torque sensor 11 detects steering wheel torque so that a steering wheel torque signal T is input into a torque detection part 14. The torque detection part 14 judges the steering direction based on an absolute value of the input steering wheel torque signal T and seeks derivative by a return detection part 15 so as to judge whether it is turning or returning of the steering wheel. When it is judged as returning of the steering wheel, a computing part 16 determines return side assist gain lower than a turn side assist gain to be determined by speed V at that time and an electric current corresponding to that value is applied on an electric motor 9 so as to perform operation control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a power steering system.

[0002]

2. Description of the Related Art FIG. 5 shows a general power steering system which variably assists the steering force depending on the vehicle speed. An input side pinion 7 is directly connected to the steering wheel 5 via an intermediate shaft 6, and an input side rack arranged on a rack shaft 4 for steering the tire 1 is engaged with the input side pinion 7. There is. Then, the torque sensor 11 arranged on the outer peripheral portion of the input side pinion 7
And the information from the vehicle speed sensor 12 arranged separately,
In the controller 8, a current controlled to assist the manual steering force of the steering wheel 5 is applied to the electric motor 9. As a result, the manual steering force is reduced to the optimum steering force in real time. Also, the electric motor 9
As shown in FIG. 7, the current is applied according to a map uniquely determined by the vehicle speed. If the vehicle speed is the same, the current is applied according to the same map when the steering wheel is turned and when the steering wheel is returned. It is supposed to be done.
The speed reducer 10 between the electric motor 9 and the output side pinion 3 converts the characteristic of the electric motor 9 of high rotation and low torque into low rotation and high torque.

[0003]

As described above, in the power steering apparatus which controls the steering force variably according to the vehicle speed, the steering wheel can be lightly turned compared with the manual steering, but the vehicle speed is uniquely determined. Due to the fact that the steering wheel cut and return are controlled according to the same curve and the mechanical friction, the relationship between the steering wheel torque and the rack thrust is a hysteresis curve with the vehicle speed as a parameter as shown in FIG. That is, as the vehicle speed changes from the low speed to the high speed, the hysteresis characteristic becomes A to B.
It changes like. On this tip, A ₁ and B ₁ are rack thrust curves when the handle is cut, and A ₂ and B ₂
Shows the rack thrust curve when the steering wheel is returned. Particularly when the steering wheel returns at a low speed, the rack thrust increases as shown by A ₂ in FIG. 6, so that the steering wheel returns due to the restoring force from the tires. Therefore, an object of the present invention is to reduce the feeling of hysteresis and friction while maintaining the characteristics of the power steering device that allows the steering wheel to be turned lighter than the manual steering, improve the steering wheel returning property, and realize a good steering feeling. It is to be.

[0004]

A control device for a power steering apparatus according to the present invention is obtained by a vehicle speed determination unit for determining a vehicle speed based on a signal from a vehicle speed sensor and a signal from a torque sensor for detecting a torque of a steering wheel. A torque determination unit that determines the magnitude and direction of the steering wheel torque, a turning-back determination unit that determines whether the steering wheel is in the cut state or the returning state based on the steering wheel torque, and an assist for the steering wheel based on the determination result of the vehicle speed determination unit. A gain and a current value corresponding to the gain, and a calculation unit that determines a current application direction to the electric motor for power assisting the steering wheel based on the determination result of the torque determination unit. Then, when the return of the steering wheel is detected by the turning return determination unit, it is determined by the vehicle speed at that time. Determining the return side assist gain which is lower than the cut side assist gain to be, characterized in that the current corresponding to the value to be applied to the motor.

[Action]

A torque sensor for detecting the torque of the steering wheel and a signal from the vehicle speed sensor determine the assist gain for the steering wheel in the controller.
A current value corresponding to the value is applied to the electric motor so as to correspond to the turning direction, so that the manual steering force of the steering wheel is controlled. At this time, the steering direction and the cut or return state are determined based on the change in the torque data from the torque sensor. In the case of the cut state, the steering force is controlled by the above method according to the vehicle speed. On the other hand, when the steering wheel is in the return state, the steering wheel return control is performed by determining the return side assist gain that is lower than the assist gain that should be determined by the vehicle speed at that time and applying a current corresponding to this value to the electric motor. I do. As a result, the rack thrust is reduced compared to the control by the electric current applied to the motor when turning the steering wheel.
The handle returns better, the sense of hysteresis decreases,
Good steering feeling is obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in FIGS. 1 to 4 are power steering devices in which the steering force is variably power assisted depending on the vehicle speed. Is the same. Then, the controller 8 is shown in FIG.
As shown in, the speed determination unit 13 and the torque determination unit 14
The switchback determination unit 15 and the calculation unit 16 are used to make determinations and calculations based on signals input from the vehicle speed sensor 12 and the torque sensor 11 to control the electric motor 9. An input side pinion 7 is directly connected to the steering wheel 5 via an intermediate shaft 6, and an input side rack arranged on a rack shaft 4 for steering the tire 1 is engaged with the input side pinion 7. There is. Then, the torque sensor 11 arranged on the outer peripheral portion of the input side pinion 7
And the information from the vehicle speed sensor 12 arranged separately,
In the controller 8, a current controlled to assist the manual steering force of the steering wheel 5 is applied to the electric motor 9. As a result, the manual steering force is reduced to the optimum steering force in real time.

The speed reducer 10 between the electric motor 9 and the output pinion 3 converts the characteristic of the electric motor 9 of high rotation and low torque into low rotation and high torque. The steering wheel torque signal T is obtained as a voltage having a constant inclination with respect to the steering angle, as shown in FIG. The steering direction is determined by the absolute value of T, and the steering wheel return state is determined by obtaining the derivative. In this embodiment, in the straight traveling state, T
= T ₁ (V), if T> T ₁ (V), the steering direction is to the right, and at the same time, when the derivative of T is positive, it is a cutting state, and when it is negative, it is a returning state. If T <T ₁ (V), the steering direction is to the left, and in that case, the derivative is a return state when the derivative of T is positive.

After making the above judgment, the steering wheel 5
When the steering wheel return control according to the present invention is carried out at the time of return of the steering wheel to reduce the rack thrust force with respect to the steering wheel torque, the rack thrust curve at the time of steering wheel return becomes A ₂ , B shown in FIG. _{From 2} to A ₃ and B ₃ shown in FIG. 2, the steering wheel returns better at each vehicle speed. When the vehicle speed is low, the amount of decrease in the assist gain is controlled to be larger than when the vehicle speed is high. As described above, by changing the steering wheel return control according to the vehicle speed, the steering wheel return becomes particularly fast at low speeds, and a good steering feeling with a feeling of response can be obtained at high speeds.

The control of the electric motor 9 will be described with reference to the flowchart of FIG. First, the torque signal T from the torque sensor is read, and it is determined whether or not there is a change in the signal T. If there is a change, it is determined that the steering wheel 5 has been steered (steps 10 and 15). Then
It is determined whether the steering wheel 5 is in the right-turning state or the left-turning state in the steering direction (step 20).
At the same time, by determining the torque value from the torque signal T and the derivative thereof, it is determined whether the steering wheel is turned or returned (step 30).

When it is determined in step 30 that the steering wheel is turned, the signal V from the vehicle speed sensor is output.
Is read to determine whether the current vehicle speed is low or not (steps 40 and 50). When it is determined that the vehicle is traveling at a low speed, a low-speed side assist gain is determined, and a current value corresponding to the value is applied to the electric motor 9 so as to correspond to the single direction determined in step 20. (Step 60). Further, in the step 50,
When it is determined that the vehicle is traveling at a high speed, the turning side assist gain for high speed is determined, and the current value corresponding to the value is applied to the electric motor 9 so as to correspond to the steering direction determined in step 20. (Step 70).

On the other hand, if it is determined in step 30 that the steering wheel 5 is returning, it is determined whether the current vehicle speed is low or not (step 3).
5, 80), at the time of low speed, a return-side assist gain smaller than the low-speed cut-off side assist gain is determined, and the electric current value corresponding to the value is set to the electric motor 9 so as to correspond to the direction determined in step 20. Apply (step 90). If it is determined that the vehicle is traveling at a high speed, a return assist gain smaller than the high-speed turning-side assist gain is determined, and the current value corresponding to that value is made to correspond to the direction determined in step 20. To the electric motor 9. At this time, the amount of decrease in the assist gain is changed when the vehicle speed is low and when the vehicle speed is high, and the amount of decrease in the assist gain is smaller when the vehicle speed is high. In the present embodiment, the vehicle speed is divided into two types, high speed and low speed, and the control is performed according to each, but the vehicle speed can be divided more finely.

[0012]

According to the control device of the present invention, the hysteresis feeling is reduced, and the steering wheel returning property and the steering feeling are improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a controller according to an embodiment.

FIG. 2 is a graph showing the relationship between the handle torque and the rack thrust when the control of the present invention is performed.

FIG. 3 is a flowchart of control processing.

FIG. 4 is a graph of a steering wheel torque signal.

FIG. 5 is a configuration diagram of a conventional power steering apparatus.

FIG. 6 is a graph showing the relationship between the handle torque and the rack thrust when the conventional control is performed.

FIG. 7 is a graph showing the relationship between steering torque, electric motor current, and vehicle speed when conventional control is performed.

[Explanation of symbols]

 8 controller 9 electric motor 11 torque sensor 12 vehicle speed sensor 13 speed determination unit 14 torque determination unit 15 cutback determination unit 16 arithmetic unit

Claims (1)

[Claims] 1. A vehicle speed determination unit that determines a vehicle speed based on a signal from a vehicle speed sensor, and a torque determination unit that determines a magnitude and a direction of a steering wheel torque obtained from a signal from a torque sensor that detects a torque of a steering wheel. The steering wheel is in the cut state or the return state based on the steering wheel torque, and the steering wheel return determination unit that determines whether the steering wheel is in the return state, and the assist gain for the steering wheel based on the determination result of the vehicle speed determination unit and the current value corresponding to the value are determined. And a calculation unit that determines the direction of current application to the electric motor for performing power assist on the steering wheel based on the determination result of the torque determination unit. When the vehicle is running, the return is lower than the cut-side assist gain that should be determined by the vehicle speed at that time. A controller for a power steering apparatus, characterized in that a side assist gain is determined and a current corresponding to the value is applied to the electric motor.