JPH01309873A - Device for controlling motor-driven power steering - Google Patents

Abstract

PURPOSE:To improve a restoring property at the time of releasing the hold and obtain a good steering feeling by controlling an electric motor for assistingly steering a steering shaft in a condition of releasing the hold of a steering wheel based on the steering angle and vehicle speed at that time. CONSTITUTION:A steering shaft 2 steered by a steering wheel 1 is assisted in its steering by means of an electric motor 6 via a reduction gear 5. In this case, a torque sensor 7 for detecting the steering force of the steering wheel 1 and a steering angle sensor 8 for detecting the steering angle thereof are installed on the steering shaft 2. Based on the detected signals of the sensors 7, 8 and a vehicle speed, an electric motor 6 is controlled by a motor-driven power steering control device 9. That is, a returning force is operated based on the steering angle and vehicle speed in a condition that a driver released his hold of the steering wheel 1, to control the electric motor 6. Thereby, a restoring property at the time of releasing the hold can be improved obtaining a favorable steering feeling.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power steering control device for an automobile that generates an appropriate auxiliary steering force depending on the steering force, for example, and achieves a good steering feeling. In particular, it relates to a device with improved restorability when steering only to the left or right.

Conventional technology In the conventional electric power steering control device,
The steering torque applied to the steering shaft during steering is detected, the electric motor is controlled based on the output signal of this torque sensor, and auxiliary steering force is generated via the reduction gear. It has been proposed to reduce the steering force in this way and improve the steering feeling.

Problems to be Solved by the Invention However, the motor control amount is determined by adding the control amount obtained based on the output signal of the torque sensor to the current motor control amount, and then multiplying the resultant by a correction coefficient depending on the driving state of the vehicle. ing. As a result, when steering is finished and you release your hands, even though the output of the torque sensor becomes zero, the motor control amount does not immediately become zero, and an auxiliary steering force is applied for a while in the opposite direction to which the steering wheel is trying to return. Therefore, there is a problem that the restorability of the steering system is reduced.

In addition, in such an electric type, since the electric motor is connected to the steering shaft via a reduction gear or the like, restorability tends to deteriorate due to friction of the reduction gear, inertia of the electric motor, etc.

To solve this problem, Japanese Patent Application Laid-Open No. 61-89170 discloses a system in which the electric motor is controlled by combining the assist force generated by the steering torque of the steering system with a return force according to the steering angle, thereby relaxing the steering force. There are some that aim to improve restorability by immediately exerting a returning force. However, the restoring force is generated by the self-lining torque of the steering wheel, and since this changes depending on the vehicle speed,
If the return force is always based on the steering angle, the return performance is poor at low speeds,
Furthermore, at high speeds, the return force is large and tends to become unstable.

Means for Solving the Problems The present invention is designed to cause an electric motor to generate an appropriate return force in accordance with the steering angle and vehicle speed at that time, when the steering is completed and the steering wheel is in a state of being released. It is characterized by control.

Operation The present invention has the above-mentioned configuration, detects the hand-off state, sets the motor control amount to zero when the vehicle speed is around O, generates a large return force at low speeds, and conversely generates a negative return force at high speeds. This improves the ability to recover when the driver lets go of the steering wheel, providing a good steering feel.

Example An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the basic configuration of the present invention. 1 is a steering wheel, 2 is a steering shaft, 3 is a steering gear, and 4 is a tire. An electric motor 6 is connected to the steering shaft 2 via a reduction gear 5, and by driving the electric motor 6, an auxiliary steering force is generated. 7 is a torque sensor attached to the steering shaft;
An output corresponding to the steering force of the steering wheel 1 can be obtained. 8 is a steering angle sensor that outputs a signal according to the steering angle of the steering wheel; 9 is an electric power steering control device of the present invention;
A RAM (random access memory), a ROM (read-only memory) in which processing programs are stored, and an analog converter that converts the outputs of the torque sensor 7, vehicle speed sensor (not shown), and steering angle sensor 8 into digital values. A digital converter (A/D converter) is included. The electric steering control device 9 includes a torque sensor 7,
It is configured to determine the motor control amount based on information from the vehicle speed sensor and the steering angle sensor 8, and to control the motor 6.

FIG. 2 shows the operation flow of the electric power steering control device of the present invention. In step ■, the output Vf of the vehicle speed sensor is
In step (2), the output θi of the steering angle sensor (2) is read, and in step 3, the output Ti of the torque sensor 7 is read.

In step 4, it is determined whether the absolute value of the steering torque T1 is larger than the specified value Ts of the steering torque. That is, it detects whether the steering wheel is being turned. If the steering torque Ti is smaller than the specified value Ts, the process moves to step (2), and if it is larger, the process moves to step (2). In step (2), it is determined whether the absolute value of the steering angle θi is larger than the specified value θS of the steering angle. That is, it is detected whether the steering wheel is near the neutral position, and if the steering angle θi is smaller than the specified value θS, the process moves to step (2), and if it is larger, the process moves to step (2). In step (2), since the steering torque is small and the turning angle is small, it is determined that the vehicle is traveling straight and the control amount of the electric motor is set to zero. In step 2, it is determined that the steering torque is below the specified value and the turning angle is above the specified value, that is, the hand is in a hands-off state, and the return force is calculated from the vehicle speed Vt and the turning angle i using a map obtained in advance. ■ Outputs to the electric motor. In step ■, since the steering torque Ti is larger than the specified value Ts, it is determined that the steering state is present, and the assist force is determined by calculation from the steering torque Ti, vehicle speed Vi, steering angle θi, etc., and is output to the electric motor in step ■. . By repeating the above routine, the power steering system using the electric motor is controlled. The calculation performed in step (2) will be explained in detail using FIG. In order to determine the return force Ro, first the basic return force R is determined from the steering angle θi.
Find c. In FIG. 3a, the horizontal axis is the steering angle θi, and the vertical axis is the basic return force RC. This table was taken in advance from a car equipped with this power steering system, and is used to determine the basic return force Rc from the steering angle θi.

Next, the basic return force Re is corrected based on the vehicle speed. In FIG. 3, the horizontal axis is the vehicle speed Vi and the vertical axis is the correction coefficient Kr. This correction table is also obtained in advance, and the correction coefficient Kr is determined from the vehicle speed Vi. The return force Ro is determined by the product of the basic return force Rc based on the steering angle and the correction coefficient Kr based on the vehicle speed. The assist force calculation performed in step (3) is already obtained using known means.

Effects of the Invention As described above, the present invention detects the hand-off state, calculates the return force based on the vehicle speed and steering angle, and controls the electric motor to ensure appropriate restorability according to the steering angle and vehicle speed. be able to. In other words, at low speeds, the return force is increased,
At high speeds, the return force is small to ensure stability and provide a comfortable steering feel.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of the electric power steering control device of the present invention, FIG. 2 is a flowchart showing the operation flow of the device, and FIG. 3 is a table used to determine the return force. 1... Steering wheel, 2... Steering shaft, 3... Steering gear, 4... Tire, 5... Speed reducer, 6... Electric motor, 7...・
Torque sensor, 8... Steering angle sensor, 9... Control device. Name of agent: Patent Attorney Toshio Tsuchinakao Haka18 2nd address

Claims (1)

[Claims] The electric motor is controlled based on the detection output of a torque sensor that detects the steering force of the steering wheel, and generates an auxiliary steering force in the steering system.
An electric power steering control device, characterized in that the electric motor is controlled by a turning angle signal of the steering wheel and a vehicle speed signal at that time.