JPH0354076A - Rear wheel steering angle control device for four-wheel steering car - Google Patents

Abstract

PURPOSE:To prevent production of a change with a time and to improve reliability of a device by a method wherein a deviation value between the target position and the present position of an electric motor is computed, PID processing is applied on the deviation value, and the computing result is added to output a current command value to the electric motor. CONSTITUTION:A control device 9 counts a detecting value from a position detector 3, mounted to an electric motor, by a counter 6 by using a digital amount to determine the present position of the electric motor. Detecting values from a handle angle sensor 1 and a car speed sensor 2 are converted into a digital value by means of a plurality of A/D converters 4 and 5. A current command value is inputted to the electric motor by a D/A converter 8. Meanwhile, the target position of the electric motor is computed by a microcomputer 7. In this case, a deviation value between the target position and the present position of the electric motor is computed, a gain is set based on the deviation value, and by integrating and differentiating the deviation value, respective gains are set. Each gain computing result is added to output a current command value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to rear wheel steering angle control of a four-wheel steering vehicle in which the rear wheel steering angle is controlled by an electric motor according to vehicle driving conditions such as steering angle. It is related to the device.

BACKGROUND OF THE INVENTION Conventionally, a rear wheel steering angle control device for a four-wheel steering vehicle has been disclosed, for example, in Japanese Unexamined Patent Publication No. 01-22 [I75].
When the vehicle is running at a speed lower than the predetermined vehicle speed value, the steering angle ratio of the front wheels and rear wheels is set to a value where the rear wheel steering angle is in the opposite phase to the front wheel steering angle. It has also been proposed to set the steering ratio to a value where the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle is traveling at a higher speed than a predetermined vehicle speed value. There is.

The main advantage of four-wheel steering vehicles is that the cornering force of the front and rear tires can be generated almost simultaneously, so the vehicle can move laterally after steering wheel operation faster than a vehicle with only front-wheel steering.

That is, if the front wheels and rear wheels are steered at an appropriate steering angle ratio such that the front and rear wheels are in opposite phases at low speeds and in phase at high speeds, the rotational motion starts earlier, thereby reducing the delay in lateral acceleration response to steering. Practical effects include improved maneuverability at low speeds and improved ability to avoid emergency situations at high speeds.

One way to steer the rear wheels is to transmit the meandering angle of the front wheels to the mechanical rear wheels, tilt the rotating surface of the yoke incorporated there, and continuously change the steering direction and steering ratio. A method of operating the rear wheels using hydraulic pressure has been proposed.

However, with the method of operating the rear wheels using hydraulic pressure,
Turning the oil pump causes engine power loss. The disadvantages are that it is difficult to control hydraulic pressure, and there is little possibility of detailed matching and development of rear wheel steering control.

Therefore, a system has been proposed that enables various possibilities for rear wheel steering control by directly steering the rear wheels with an electric motor (for example, Japanese Patent Laid-Open Publication No. 1983-1 [I2376]).

FIG. 2 shows a block diagram of a conventional rear wheel steering angle control device. The electric motor is provided with a position detector 12, and the control device 19 is provided with a counter 15 that counts the value of the position detector in digital quantities to determine the current position of the electric motor. Steering wheel angle sensor 1
01 Based on the steering wheel angle and vehicle speed input from the vehicle speed sensor 11 via the A/D converters 13 and 14, the microprocomputer 17 in the control device calculates the deviation value between the target position of the electric motor and the current position counted by the counter. is calculated, the gain is set for the deviation value, and the gain setting result is sent to the motor.
It is output as a current command value via the A converter 18 and the motor is driven so that the deviation value becomes O.

In addition, the position signal of the position detector of the electric motor is transmitted to the F/V converter 16.
The damping is improved by converting it into a speed signal, performing gain setting on the speed signal value, and feeding back the gain setting result to the current command value.

Problems to be Solved by the Invention However, in the conventional rear wheel steering angle control device configured as described above, the speed signal value requires adjustment. If this adjustment is performed using a volume, there is a problem that changes over time, temperature characteristics, etc. cannot be ignored. Further, since the conventional rear wheel steering angle control device does not perform integral compensation, a problem arises in that a steady-state deviation remains.

Means for Solving the Problems In order to solve the above problems, in the present invention, a position detector is provided in the electric motor that controls the rear wheel steering angle, and the value of the position detector is counted in a digital quantity within the control device. A counter that determines the current position of the motor, an A/D converter that converts the detection signals from the steering angle and vehicle speed sensors into digital values, a D/A converter that provides a current command value to the motor, and the motor. A first gain calculation that calculates a deviation value between the target position of the motor calculated by the microcomputer and the current position counted by a counter, and sets a gain for the deviation value. The results of the second gain calculation, which sets the gain by integrating the deviation value, and the third gain calculation, which sets the gain by differentiating the deviation value, are added in the microcomputer to perform D/A. A current command value is output to the motor via a converter to drive the motor stably and without steady-state deviation.

Further, when the deviation value is larger than a certain value, the second gain setting value for setting the gain by integrating the deviation value is set to O to ensure stability during a transient response.

Operation With the above-described configuration, the present invention calculates the deviation value between the target position of the motor calculated by the microphone port computer in the control device and the current position counted by the counter, and calculates the PI for the deviation value.
D filter processing is performed, the calculation results are added in the microcomputer, and a current command value is output to the motor via the D/A converter.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a block diagram of a rear wheel steering angle control device for a four-wheel steering vehicle according to the present invention.

Inside the control device 9, there is a counter 6 that calculates the current position of the motor by counting the value of the position detector 3 attached to the motor in digital quantities, and a counter 6 that converts the detection signals from the steering wheel steering angle sensor 1 and the vehicle speed sensor 2 into digital values. A/D converters 4 and 5 are provided, a D/A converter 8 provides a current command value to the motor, and a microcomputer 7 calculates the target position of the motor.

FIG. 3 shows a block diagram of the PID filter.

The deviation value between the target position and the current position of the motor is calculated every sampling period. FIG. 3 represents the proportional term, integral term, and differential term individually in a discrete system.

The coefficients P, b, and a of each term are set to optimal values in consideration of the stability of the control system, etc. FIG. 4 shows a diagrammatic representation of the flow of calculations based on FIG. 3. The current deviation value is (a1), and the value of (a4) is the sum of (a1) and (a3) (the value of (a4) one cycle ago, the initial value is O).

Let the value of (a1) one cycle ago be (a2), (a2),
Let (a5L (a6), (a7) be the result of multiplying (al) and (a4) by -aSa+PX b, respectively).

The final output value (a8) to the D/A converter is (a5L
(a6). This is the value obtained by adding (a?) and performing Limit processing in accordance with the number of bits of the D/A converter. As described above, after PID filter processing is performed on the deviation value within the microcomputer, the current command value is output to the motor via the D/A converter, thereby operating the motor stably and without steady-state deviation. Can be driven.

FIG. 5(a) shows a schematic PAD diagram of the arithmetic processing performed within the microcomputer in the first embodiment of the present invention. Inside the microcomputer, signals from each sensor are first input (S1) and the target position of the motor is calculated (S1).
2). After that, the deviation value from the current position of the motor counted by the counter is calculated (S3), and this value is calculated by the PTD filter (
S4) After setting L, output it to the motor as a current command value (S
5).

FIG. 5(b) shows a schematic PAD diagram of the arithmetic processing performed within the microcomputer in the second embodiment of the present invention. (S6) to (S8) are (S1) to (S8) of the first embodiment.
This is the same as 3). If this deviation value is larger than the constant K, the deviation value is subjected to PD filter calculation (S9), and if it is smaller than the constant K, the deviation value is subjected to PID filter calculation (SIO
)L, then outputs it to the motor as a current command value. Using the second embodiment improves stability during transient response.

Effects of the Invention As described above, according to the present invention, the feedback of the speed signal value which was configured with hardware, which was necessary in the prior art, is eliminated, and the processing in position control is performed by digital processing. This reduces the circuit scale, improves the safety and reliability of the device, and improves its versatility and productivity. Moreover, since data processing can be performed by a microcomputer, it has a self-diagnosis function, and the maintainability of the device can be improved, resulting in remarkable effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a rear wheel steering angle control device for a four-wheel steering vehicle according to an embodiment of the present invention, FIG. 2 is a block diagram of a rear wheel steering angle control device for a conventional four-wheel steering vehicle, and FIG. Figure 4 is a block diagram of the PID filter, Figure 4 is an explanatory diagram of the operation of the PID filter, Figure 5 (a) is a schematic PAD diagram of arithmetic processing in the first embodiment of the present invention, Figure 5 (b) is the invention FIG. 3 is a schematic PAD diagram of arithmetic processing in the second embodiment. 1, 10... Steering wheel steering angle sensor, 2, 1l... Vehicle speed sensor, 3, 12... Electric motor position detector, 4, 5, 13,
14... A/D converter, 7, 17... Microcomputer, 8, 18... D/A converter, 9, 19... Control device. younger brother 3 figure

Claims (2)

[Claims] (1) In a rear wheel steering angle control device for a four-wheel steering vehicle, in which a rear wheel steering angle is controlled by an electric motor according to a driving state of the vehicle detected from a sensor such as a steering wheel angle, the position of the electric motor is detected. a counter for calculating the current position of the motor by counting the value of the position detector in a digital quantity in the control device; and an A/D converter for converting the detection signal from the sensor into a digital value. A D/A converter that provides a current command value to the electric motor and a microcomputer that calculates a target position of the electric motor are provided, and the target position of the electric motor calculated by the microcomputer and the current position counted by the counter are provided. A first gain calculation that calculates a deviation value and sets a gain for the previous deviation value, a second gain calculation that performs an integral calculation of the deviation value and sets a gain, and a second gain calculation that performs a differential calculation of the deviation value and sets a gain. A rear wheel steering angle control device for a four-wheel steered vehicle, which adds up each gain calculation result by a third gain calculation in the microcomputer and outputs a current command value to the electric motor via a D/A converter. (2) A first gain calculation that sets a gain for the deviation value if the deviation value calculated in the microcomputer is greater than a certain value, and a second gain calculation that sets a gain by differentially calculating the deviation value. 2. The rear wheel steering angle control device for a four-wheel steering vehicle according to claim 1, wherein the results of each gain calculation are added in said microcomputer and a current command value is output to said electric motor via a D/A converter.