JPH042573A - Rear wheel steering angle control device for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To allow a motor to converge on the target position stably without steady-state deviation by subtracting the present position of the motor and the differential value of the present position from the integrated value of the deviation value between the target position and present position of the motor to obtain the current command value to be outputted to a motor driver. CONSTITUTION:A rear wheel steering angle control device steers rear wheels directly using a motor driver 10 and a motor 11, and is provided with a computing element 5 for performing the operation of a rear wheel target steering angle, the operation of the current command value 8 to the motor driver 10, the cycle instrumentation of a vehicle speed sensor, and the like in a control device 7. In this computing element 5, the rear wheel target steering angle, that is, the deviation value between the target position and present position of the motor 11 is computed at every sampling cycle, and this deviation value is integrated at every sampling cycle. The speed of the motor 11 is then obtained by subtracting the value obtained by multiplying the present position of the motor 11 by Kp, the present position of the motor 11 and the present position one cycle before from the value obtained by multiplying the integrated value by a coefficient Ki, and the values obtained by multiplying the speed by Kd are respectively subtracted to obtain the current command values 8 to be outputted to the motor driver 10.

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.

2. Description of the Related Art Conventionally, a rear wheel steering angle control device for a four-wheel steering vehicle has been used to adjust the vehicle speed to a predetermined speed after a predetermined vehicle speed value, as shown in, for example, Japanese Patent Laid-Open No. 22675/1999. When the vehicle is traveling at a speed lower than the specified 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, and when the vehicle is traveling at a higher speed than the predetermined vehicle speed value. A system has been proposed in which the steering ratio is set to a value such that the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle is traveling.

The main advantage of four-wheel steering vehicles is that cornering forces can be generated from the front and rear tires almost simultaneously, so the vehicle can move laterally after steering wheel operations more quickly than a vehicle with only front-wheel steering. In other words, if the front wheels and rear wheels are steered at an appropriate steering angle ratio such that the front and rear wheels are out of phase 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.

For example, the method of steering the rear wheels is to mechanically transmit the steering angle of the front wheels to the rear wheels, tilt the rotating surface of the yoke incorporated therein, and continuously change the steering direction and steering ratio. Recently, a method has been proposed in which the rear wheels are operated hydraulically.

However, since it is a method of operating the rear wheels with hydraulic pressure,
Turning the oil pump causes engine power loss. It also has the drawbacks of difficult hydraulic control, detailed matching of rear wheel steering control, and limited potential for development.

Therefore, a Nostem 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 Application Laid-Open No. 63162376).

FIG. 6 shows a block diagram of a conventional rear wheel steering angle control method. A computing unit 35 in the control device 30 computes the target steering angle of the rear wheels 380, that is, the target position of the electric motor 33, from the steering wheel angle sensor 31, vehicle speed sensor 32, and the like. A first gain calculation that calculates the deviation value between the target position of the electric motor 33 and the current position of the motor obtained from the position detector 34 provided on the electric motor 33, and sets a gain for the deviation value, and a gain calculation that performs an integral calculation of the deviation value. The gain calculation results of the second gain calculation to be set and the third gain calculation to set the gain by differentiating the deviation value are added in the calculator 35 and a current command is sent to the motor driver 37 via the interface circuit 36. Output the value.

However, in the conventional rear wheel steering angle control method configured as described above, a phenomenon occurs in which the current command value jumps due to proportional control and differential control due to sudden changes in the target value. There was a problem that the rotation of the electric motor became unstable and the current consumption increased.

Means for Solving the Problems In order to solve the above problems, the present invention includes a position detector for the electric motor that controls the rear wheel steering angle, and an interface circuit that determines the current position of the electric motor from the position detector in the control device. to detect the current position of the motor. Further, there is provided an arithmetic unit that calculates a rear wheel target steering angle, that is, a target position of the electric motor, etc. from the input value of the sensor, and an interface circuit that provides a current command value from the arithmetic unit to the electric motor driver.

As a first means, the deviation value between the target position and the current position of the electric motor is calculated in a computing unit, and the current position of the electric motor and the value obtained by differential calculation of the current position are subtracted from the value obtained by integrating the deviation value, and the interface It is output as a current command value to the motor driver via a circuit.

As a second means, the deviation value between the target position and the current position of the motor is calculated in a calculator, the value obtained by proportional calculation and the value obtained by integral calculation of the deviation value are added, and the value obtained by differential calculation of the current position of the motor is calculated. The result is subtracted and output as a current command value to the motor driver via the interface circuit. In addition, if the deviation value calculated by the calculator exceeds a certain value, the integral calculation value is set to zero, and the value obtained by differential calculation of the current position of the motor is subtracted from the value obtained by proportional calculation of the deviation value, and the result is calculated via the interface circuit. It is output as a current command value to the motor driver.

According to the above-described configuration, the present invention calculates the deviation value between the target position and the current position of the electric motor using the calculating unit in the control device, and the first means calculates the current position of the electric motor from the integrally calculated value of the deviation value. By outputting the feedbank value of the speed obtained by differential calculation of the current position to the motor driver as a current command value via the interface circuit, the motor is stably converged to the target position without steady-state deviation.

In the second method, the deviation value between the target position and the current position of the motor is calculated in a calculator, the value obtained by proportional calculation and the value obtained by integral calculation of the deviation value are added, and the current position of the motor is obtained by differential calculation. A value obtained by feeding back the obtained speed is outputted as a current command value to the motor via an interface circuit. In addition, if the deviation value calculated by the calculator exceeds a certain value, the integral calculation value is set to zero, and the value obtained by feeding back the speed obtained by differentially calculating the current position of the motor from the value obtained by proportionally calculating the deviation value is fed back via the interface circuit. By outputting the current command value to the motor driver as a current command value, the motor can be stably converged to the target position without steady-state deviation.

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 first invention. The rear wheel 12 is an electric motor driver 10
．． The electric motor 11 is used for direct steering. The control device 7 includes an interface circuit 4 that converts the value of a position detector 9 attached to the electric motor 10 into a digital value to determine the current position of the electric motor, and an interface circuit 4 that converts the detection signal of the /X steering angle sensor 1 into a digital value. An interface circuit 3, an interface circuit 6 for supplying a current command value to the electric motor, and a calculator 5 for calculating a rear wheel target steering angle, calculating a current command value 8 for the electric motor driver, and measuring the period of the vehicle speed sensor are provided.

The algorithm inside the computing unit will be explained. The rear wheel target steering angle, that is, the deviation value between the target position of the electric motor and the current position is calculated every sampling period. This deviation value is integrated every sampling period. The speed of the motor is determined by subtracting the value obtained by multiplying the current position of the motor by Kp, the current position of the motor, and the current position before the cycle from the value obtained by multiplying this integrated value by a coefficient of 1, and then multiplying the speed by Kd. The calculated values are subtracted from each other and output as a current command value to the motor driver via the interface circuit.

FIG. 3 shows the waveform of the step response in the first invention. As shown in the figure, it is possible to converge to the target value without overcoating/coating.

FIG. 2 shows a block diagram of a rear wheel steering angle control device for a four-wheel steering vehicle, which is an embodiment of the second invention. The configuration other than the algorithm in the arithmetic unit is the same as that of the first invention.

The algorithm in the calculator calculates the rear wheel target steering angle, that is, the deviation value between the target position of the electric motor and the current position, every sampling period. The value obtained by multiplying this deviation value by a coefficient Kp and the integrated value obtained by integrating the deviation value for each sampling period are
Add the multiplied values. The speed of the motor is determined by subtracting the current position of the motor and the current position one cycle before from this added value, and the value obtained by multiplying the speed by Kd is subtracted and output as a current command value to the motor driver via the interface circuit. do.

FIG. 4 shows the waveform of the step response in this example.

Due to the influence of the integral calculation, some O7s+- shoots occur.

FIG. 5 shows a waveform of a step response in another embodiment of the second invention. In this embodiment, if the deviation value calculated by the calculator is greater than or equal to a certain value, the integral calculation value is set to zero, and the current position of the motor is calculated by differentiating the deviation value multiplied by Kp. The multiplied value is subtracted and output as a current command value to the motor driver via the interface circuit. When such a method is adopted, the effect of integration is limited to a certain deviation value, and as shown in the figure, it is possible to converge to the target value without any open errors.

As mentioned above, the first effect is as follows. In both the second invention, the problem that occurred in the prior art where the current command value jumps due to a sudden change in the target value due to differential control, the movement of the motor becomes unstable and the current consumption increases is solved, and the current This has the effect of reducing consumption and making the motor run more smoothly.

[Brief explanation of the drawing]

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 first invention, FIG. 2 is a block diagram of an embodiment of the second invention, and FIG. FIG. 4 and FIG. 5 are step response diagrams in each embodiment of the second invention. FIG. 6 is a block diagram of a rear wheel steering angle control device of a conventional four-wheel steering vehicle. It is a diagram. Co-・・・Steering wheel steering angle sensor, 2・・・・・・
Vehicle speed sensor, 34.6... Interface circuit, 5... Arithmetic unit, 7... Control device, 8
......Current command value, 9...Position detector,
10... Electric motor driver 11... Electric motor, 12... Rear wheel. Name of agent Patent attorney Shigetaka Awano 1 person Figure 1 I%2 Figure layer W Equipment% I 2 electric 6 3ii 6 value tn i 轡 書 h electric 1 power atsun tiger 1 hat #jI YR ik tii calculation@H@den lll1l Iff love X high school 111w milk injury

Claims (3)

[Claims] (1) In a rear wheel steering angle control device for a four-wheel steering vehicle, in which the rear wheels are directly steered by an electric motor according to vehicle driving conditions detected from sensors for steering wheel angle and vehicle speed, a detector, an interface circuit in the control device that determines the current position of the electric motor from the position detector, a computing unit that computes a target steering angle of the rear wheels, etc. from the input value of the sensor, and a computing unit that calculates the target steering angle of the rear wheels from the input value of the sensor; an interface circuit that provides a current command value to the driver, calculates a deviation value between the target position and the current position of the electric motor in the calculator, and calculates a value of the current position of the electric motor from a value obtained by integrating the deviation value; and a rear wheel steering angle control device for a four-wheel steering vehicle that subtracts a value obtained by differentially calculating the current position and outputs the resultant value as a current command value to the electric motor driver via the interface circuit. (2) Calculate the deviation value between the target position of the motor and the current position in the calculator, add the value obtained by proportional calculation and the value obtained by integral calculation of the deviation value, and subtract the value calculated by differential calculation of the current position of the motor. 2. The rear wheel steering angle control device for a four-wheel steering vehicle according to claim 1, wherein the control device outputs a current command value to a motor driver via the interface circuit. (3) The rear wheel steering angle control device for a four-wheel steering vehicle according to claim 2, wherein the integral calculation value is set to zero if the deviation value calculated by the calculator is equal to or greater than a certain value.