JPH03217374A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To simplify a steering device in structure by installing a first central processing unit, which inputs all data from each sensor, and a second central processing unit which inputs indispensable minimum data for performing a diagnosis of the first CPU, respectively, and making a trouble diagnosis by comparing each fail-safe signal of these central processing units. CONSTITUTION:In this steering device, there are provided with a central processing unit 1 for control use and another central processing unit 2 for diagnosing this CPU 1, and each desired steering angle of rear wheels is operated on the basis of each output of wheel speed sensors 3, 4 for both front and rear wheels and steering angle sensors 5, 6 at the CPU 1, thereby outputting a control signal consisting of a directional signal and a PWM output signal. In addition, only this directional signal is outputted to the diagnosing CPU 2, while at time of trouble discrimination, a trouble signal is outputted to one side input terminal of a NAND circuit 7. The CPU 2 diagnoses the CPU 1 from the directional signal out of the CPU 1 and each output of those of wheel speed sensor 3 and steering angle sensors 5, 6 for front-wheel use, and the diagnosed result is inputted into the other side input terminal of the NAND circuit 7, outputting a fail-safe signal from the NAND circuit 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a four-wheel steering device that controls the turning angle of the rear wheels of a four-wheel steering vehicle, and particularly to a four-wheel steering device that reduces costs without impairing reliability. It relates to the steering device.

(Prior Art) This type of four-wheel steering system includes, for example, the one shown in Fig. 4. Fig. 4 shows a control circuit, and a central processing unit 1 for control.
In order to diagnose the central processing unit 1, a diagnostic central processing unit 2 is provided in parallel. Both central processing units 1,
2, wheel speed data for obtaining the vehicle speed is inputted via an interface from wheel speed sensors 3 and 4 for front wheels and rear wheels, respectively, and from steering angle sensors 5 and 6 for front wheels and rear wheels. Turning angle data for the front and rear wheels is input via an interface. Based on the data from each sensor 3, 4, 5, 6, both central processing units 1
, 2 calculates the target steering angle of the rear wheels and outputs a control signal consisting of a direction signal and a PWM signal, and each sensor 3,
4, 5, and 6 as well as both central processing units 1 and 2, and outputs a fail-safe signal in the event of a failure. and,
Output signals from both central processing units 1 and 2 are sent to a NAND circuit 21
, 22, 23, 24, and 25, and a control signal and a fail-safe signal are output to the rear wheel drive motor.

[Problem to be solved by the invention]

By the way, the above-mentioned device is equipped with a central processing unit 1 for control and a central processing unit 2 for diagnosis in parallel to diagnose the central processing unit 1, and in both central processing units 1 and 2, each sensor 3, While inputting data from 4, 5, and 6 in parallel, output signals are compared via NAND circuits 21, 22, 23, 24, and 25, and a rear wheel control signal and a fail-safe signal are output. The system performs steering control while ensuring system reliability. However, since signals are input from the sensors 3, 4, 5, and 6 to the central processing units 1 and 2 on the input side, not only the number of interfaces increases, but also many comparators are required on the output side. For this reason, there was a problem of high cost.

The present invention was devised in view of the above-mentioned circumstances, and aims to provide a four-wheel steering system that can reduce costs without impairing reliability.

[Means to solve the problem]

In order to achieve the above object, the present invention has a first central processing unit and a second central processing unit, and these central processing units are provided with a wheel speed control unit for front wheels and a rear wheel for obtaining vehicle body speed data. It inputs data from sensors and steering angle sensors provided for the front and rear wheels to obtain steering angle data for the front and rear wheels, calculates a target steering angle for the rear wheels, and outputs a control signal to the rear wheel drive system. In a four-wheel steering system that diagnoses each sensor and a first central processing unit and outputs a fail-safe signal, the first central processing unit collects data from wheel speed sensors for front wheels and rear wheels, and diagnoses each sensor and first central processing unit and outputs a fail-safe signal. The second central processing unit inputs the control signal from the first central processing unit and outputs a control signal to the rear wheel drive device and the second central processing unit. Diagnosis of the first central processing unit is performed by inputting data from wheel speed sensors for the front wheels and steering angle sensors for the front and rear wheels.

[Effect]

According to the configuration of the present invention, the first central processing unit and the second central processing unit are provided with wheel speed sensors provided for the front wheels and rear wheels to obtain vehicle body speed data, and wheel speed sensors provided for the front wheels and the rear wheels for obtaining vehicle body speed data. It inputs data from a steering angle sensor for obtaining wheel turning angle data, calculates a target steering angle for the rear wheels, outputs a control signal to the rear wheel drive system, and diagnoses each sensor and the first central processing unit. outputs a fail-safe signal, but
The first central processing unit inputs the data of the wheel speed sensors for the front wheels and the rear wheels and the data of the steering angle sensors for the front wheels and the rear wheels, and sends control signals to the rear wheel drive unit and the second central processing unit. On the other hand, the second central processing unit inputs the control signal from the first central processing unit, and also inputs data only from the wheel speed sensor for the front wheels and the steering angle sensors for the front wheels and rear wheels. Diagnoses the central processing unit.

〔Example〕

The present invention will be explained based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing a circuit configuration, and FIGS. 2 and 3 are flowcharts showing control operations of a control central processing unit and a diagnostic central processing unit, respectively.

This system has a central processing unit 1 for control and a central processing unit 2 for diagnosis in parallel to diagnose the central processing unit 1.

The central processing unit 1 for control uses a 16-bit microprocessor, and wheel speed data for obtaining the vehicle speed is inputted via an interface from wheel speed sensors 3 and 4 for front wheels and rear wheels. Ru. Furthermore, data on the direction and magnitude of the steering angles of the front and rear wheels is input to the central processing unit 1 for control from the front wheel and rear wheel steering angle sensors 5 and 6 via an interface. Rudder angle sensor 5,
6 are respectively equipped with encoders 5a, 5a, center switch tips 5b, 6b, and potentiometers 5c, 6c that can obtain the direction and magnitude of the steering angle, and each output terminal is connected to a central processing unit for control via an interface. 1
is connected to the input terminal of

On the other hand, the central processing unit 2 for diagnosis uses a 3-bit microprocessor, and a wheel speed sensor 3 for the front wheels is used.
Wheel speed data for obtaining the vehicle body speed is inputted via the interface, but unlike the central processing unit 1 for control described above, it is not inputted from the wheel speed sensor 4 for the rear wheels. Moreover, turning angle data of the front and rear wheels is inputted to this central processing unit 2 for diagnosis via an interface from steering angle sensors 5 and 6 for front wheels and rear wheels. Unlike the potentiometer 5C, which can obtain the direction and magnitude of the center switch tips 5b, 6b and the steering angle without inputting from each encoder 5a, 6a.
, input only from 6C.

The central processing unit 1 for control also includes the sensors 3,
The target steering angle of the rear wheels is calculated based on the data from 4, 5, and 6, and a control signal consisting of a direction signal and a PWM output signal is output to the rear wheel drive motor, and only the direction signal is processed centrally for diagnosis. Outputting to device 2. In addition, the central processing unit l for this control is also
, 4, 5, and 6, a failure signal is output to one input terminal of the NAND circuit 7.

Moreover, the central processing unit 2 for diagnosis compares the direction signal from the central processing unit 1 for control with the data of each of the sensors 3, 5, and 6 except for the wheel speed sensor 4 for the rear wheels. The control central processing unit 1 is diagnosed, and the diagnosis results are output to the other input terminal of the NAND circuit 7. Note that 8 is a signal line connecting the two central processing units 1 and 2, and data communication is performed via this signal line 8, and both the central processing units 1 and 2 mutually detect runaway.

Further, 9 is a current sensor, and the current value of the rear wheel drive motor is controlled based on data from this current sensor +9.

Next, the control operations by the central processing units 1 and 2 are performed in a second manner.
This will be explained based on the flowcharts shown in FIG. 3 and FIG. 3, respectively.

First, FIG. 2(A) shows the main routine of the central processing unit 1 for control. First, each sensor 3, 4, 5, and 6 is diagnosed (step 101), and then an interrupt is received (
Step 102), the target steering angle is calculated based on the data provided from each sensor +3, 4, 5, and 6 (
Step 103) outputs a control signal consisting of a direction signal and a PWM output signal to the rear wheel drive motor, and outputs only the direction signal to the central processing unit 2 for diagnosis (step 104), and returns to step 101 at an appropriate cycle. Return and diagnose each sensor 3, 4, 5, and 6 again (stenop 105).

In the steno panel 101, a subroutine shown in FIG. 2(B) is executed. In the subroutine, first, each sensor 3, 4,
The operating states of 5 and 6 are checked (step 106).

Then, if it is determined that there is a failure in the stethop 107,
NAND circuit 7 for fail-safe signal with stenop 108
Output to. If the steno knob 107 fails, the process returns to the main routine shown in FIG. 2(A), whereupon the necessary processing is continued, and the above procedure is repeated.

On the other hand, FIG. 3 shows the routine of the central processing unit 2 for diagnosis. A failure of the central processing unit 1 is diagnosed by comparing input data of direction signals (step 201), and if a failure is determined in step 202, a fail-safe signal is outputted to the NAND circuit 7 by the stepshop 203. do. If there is no failure in step 202, the process returns to step 201 and the above procedure is repeated.

In this way, the central processing unit 1 for control includes each sensor 3,
All data is input from sensors 4, 5, and 6, but the central processing unit 2 for diagnosis has input from each sensor 3, 5, and 6 except for the central processing unit 1 for control and the wheel speed sensor 4 for rear wheels. While inputting data, on the output side, only the fail-safe signals from both central processing units 1 and 2 are compared and outputted by a NAND circuit 7, and the control signal for the rear wheel target steering angle is outputted as is without comparison. As a result, it is possible to reduce the number of interfaces on the input side and the number of NAND circuits 7 on the output side, thereby achieving a significant reduction in cost while ensuring reliability.

Further, in the above embodiment, data is inputted to the central processing unit 2 for diagnosis only from the center switch positions 5b, 6b and potentiometers 5c, 6c among the steering angle sensors 5, 6, and data is inputted from the encoders 5a, 6a. Since no input is required, the number of interfaces can be further reduced.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, all data from each sensor is input to the first central processing unit, but the second central processing unit is required to be able to diagnose the first central processing unit. By inputting only the minimum amount of data, comparing only the fail-safe signals of both central processing units on the output side, and outputting the control signal for the rear wheel target steering angle as is without comparing it, the interface on the input side Since the number of comparators can be reduced on the output side, it is possible to significantly reduce costs while ensuring reliability.

[Brief explanation of drawings]

The drawings show an embodiment of a four-wheel steering device according to the present invention,
Fig. 1 is a block diagram showing the circuit configuration, Figs. 2 and 3 are flowcharts showing the control operations of the central processing unit for control and the central processing unit for diagnosis, respectively, and Fig. 4 shows the circuit configuration of the conventional example. FIG. (Explanation of symbols in drawings showing main parts) 1, 2...Central processing unit 3, 4...Wheel speed sensor

Claims (1)

[Claims] It has a first central processing unit and a second central processing unit, and both central processing units have wheel speed sensors provided for the front wheels and rear wheels for obtaining vehicle speed data, and wheel speed sensors provided for the front wheels and the rear wheels. Inputs data from the steering angle sensor to obtain turning angle data of the front and rear wheels, calculates the target steering angle of the rear wheels, outputs a control signal to the rear wheel drive system, and diagnoses each sensor and the first central processing unit. In a four-wheel steering system that outputs a fail-safe signal, the first central processing unit inputs data from wheel speed sensors for front wheels and rear wheels and data from steering angle sensors for front wheels and rear wheels. The second central processing unit outputs the control signal to the rear wheel drive device and the second central processing unit, while the second central processing unit inputs the control signal from the first central processing unit and outputs the control signal to the rear wheel drive device and the second central processing unit. A four-wheel steering system characterized by inputting data from a steering angle sensor for diagnosing a first central processing unit.