JPH037659A - Four-wheel steering system - Google Patents

Abstract

PURPOSE:To enhance the steering feeling and the running stability by feeding back the rear wheel steering angle and its velocity component, converting into the angle acceleration, providing a rear wheel steering motor with torque controllability, and thereby accormplishing smooth steering of the rear wheels. CONSTITUTION:Deviation value (deviation angle) of the rear wheel steering angle (e) given by a rear wheel steering angle sensor 2c from the target rear wheel steering angle 10 calculated from a front wheel steering angle signal (d) is subjected to angular velocity conversion 13, while the velocity component of the rear wheel ateering angle (e) extracted by a differentiator device 14 is fed back to determine the angular velocity deviation value 15. Further the angular velocity deviation value is converted 16 into angle acceleration, compared with the current value 18 of a rear wheel steering motor 2a in a comparator 17, coordinated appropriately, and given out as the torque deviation value to serve controlling the motor 2a. This enables the motor 2a to be torque controlled in accordance with the load, the deviation from the target position can be lessened. Further, feeding back the velocity component of the rear wheel steering angle (e) will enhance the response.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel steering system, and particularly to control of an electric motor for steering rear wheels.

[Conventional technology]

FIG. 3 is a configuration diagram showing a four-wheel steering system for boat fishing. In the figure, 1 is a front wheel steering device, 1a is a front wheel steering angle detector, 1b is a column sensor, 2 is a rear wheel steering device, 2a is a rear wheel steering electric motor, 2b is a reduction gear, and 2c is an electric motor 2a.
Rear wheel steering angle detector installed on the shaft driven by 2d
3 is a centering spring, 3 is a controller to which vehicle speed signal a, engine rotation signal S, column sensor signal C2, front steering angle signal d, and rear wheel steering angle signal e are input; 4 is electric motor 2
Safety relay as a relay for power supply to a, 5
is a fuse, 6 is an ignition switch, and T is a power terminal to which power is supplied from the battery. In FIG. 4, the rear wheel steering electric motor 2a steers the rear wheels, and the rear wheel steering angle is detected by the rear wheel steering angle detector 2C.

Next, a conventional four-wheel steering system will be explained using FIG. 4. In the figure, 10 is a target rear wheel steering angle calculator, 11 is a comparator, and 12 is a PWM signal generator. In FIG. 4, the same or equivalent parts as in FIG. 3 are given the same reference numerals. be. In addition, the target rear wheel steering angle calculator 10, the comparator 11, and the P
The WM signal signal generating section code 12 constitutes the controller 3.

The target rear wheel steering angle calculator 10 inputs the front wheel steering angle signal d output from the front wheel steering angle detector 1a, calculates a target rear wheel steering angle, and outputs it to the comparator 11. The comparator 11 compares the target rear wheel steering angle and the rear wheel steering angle e, and outputs the deviation value to the PWM signal generator 12. PWM signal signal generator 12 generates a PWM signal with a duty ratio according to the deviation value, and drives the rear wheel steering electric motor 2a with the duty ratio.

[Problem to be solved by the invention]

In a four-wheel steering system with such a configuration, the rear wheel steering electric motor @ 2a is controlled by voltage, that is, rotation speed control, and when the motor load such as friction load between the tires and the road surface is large, the torque of the electric motor 2a follows. However, the actual rear wheel steering behavior was jerky and not smooth, resulting in poor steering feel and running stability.

The present invention has been made in view of these points, and its purpose is to provide a four-wheel steering system with good steering feel and running stability.

[Means to solve the problem]

In order to solve such problems, the four-wheel steering system according to the present invention steers the rear wheels according to the steering angle of the front wheels. A means for driving the electric motor by current control is provided.

[Effect]

In the four-wheel steering system according to the present invention, the rear wheels are smoothly steered.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of a four-wheel steering system according to the present invention. In the figure, 13 is an angular velocity converter, 14 is a differentiator, 15 is a comparator, 16 is an angular acceleration converter, 17 is a comparator, and 18 is a current detector. Or equivalent parts have the same numerals.
It is shi. Note that the devices 10 to 18 constitute the controller 3.

Next, the operation will be explained. The comparator 11 outputs a deviation value between the target rear wheel steering angle output from the target rear wheel steering angle calculator 10 and the rear wheel steering angle e output from the rear wheel steering angle detector 2C. This deviation value is converted into an angular velocity by an angular velocity converter 13, and compared with the velocity component of the rear wheel steering angle e extracted by a differentiator]4 by a comparator 15. The angular velocity deviation value which is the output of the comparator 15 is converted into angular acceleration by the angular acceleration converter 16, and compared with the current value of the rear wheel steering electric motor 2a by the comparator 17. Both angular acceleration and current represent torque,
As a result, the torque deviation value is input from the comparator 17 to the PWM signal generator 12, and the rear wheel steering electric motor 2a is controlled.

As mentioned above, in this embodiment, since the rear wheel steering electric motor 2a is torque controlled, torque control according to the load is possible, and the deviation from the target position can be reduced. Furthermore, since the speed component of the rear wheel steering angle e is extracted by the differentiator 14 and fed back, responsiveness can be improved.

FIG. 2 shows the responsiveness of the rear wheel steering angle in the conventional example and the present example. A dotted line S1 indicates the responsiveness of the conventional example, and a solid line S2 indicates the responsiveness of the present embodiment.

From Figure 2, it can be seen that the rear wheels are being steered smoothly. This improves the steering feel and improves driving stability.

〔Effect of the invention〕

As explained above, the present invention provides means for feeding back the speed component of the rear wheel steering angle and means for driving the electric motor by current control, thereby making it possible to smoothly steer the rear wheels. It has the effect of improving feeling and running stability.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a four-wheel steering system according to the present invention;
Figure 2 is a rear wheel steering angle response characteristic diagram comparing the characteristics of the conventional example and the system characteristics of Figure 1, Figure 3 is a configuration diagram showing a general four-wheel steering system, and Figure 4 is FIG. 1 is a system diagram showing a conventional four-wheel steering system. 1... Front wheel steering device, 1a... Front wheel steering angle detector, 1
b... Column sensor, 2... Rear wheel steering device, 2a.
...Rear wheel steering electric motor, 2b... Reduction gear, 2C...
・Rear wheel steering angle detector, 2d...Centering spring, 3...Controller, 4...Safety relay,
5...Fuse, 6...Ignition switch,
T...Power terminal, 10...Target rear wheel steering angle calculator, 1
1.15.17... Comparator, 12... PWM signal generator, 13... Angular velocity converter, 14... Differentiator, 1
6... Angular acceleration converter, 18... Current detector.

Claims (1)

[Claims] A four-wheel steering system in which rear wheels are steered by an electric motor according to a steering angle of the front wheels, comprising means for feeding back a speed component of the rear wheel steering angle in response to an angular velocity command, and means for driving the electric motor by current control. A four-wheel steering system is featured.