JPH0550928A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To prevent an unstable condition of steering control of rear wheels immediately after the time a power source is turned on by controlling the rear wheel steering according to the detecting signals of detecting means other than a yaw rate sensor, for a period from the time the power source is turned on until the detecting accuracy of the yaw rate sensor is stabilized. CONSTITUTION:In a control unit 1 which controls a rear wheel steering device 2 by inputting the detecting signals of a car speed sensor 4, a yaw rate sensor 5, the front and the rear wheel steering angle sensors 7 and 6, a brake switch 8, and the like, the first control means 101 to control the rear wheel steering depending on the yaw rate, the car speed, and the front and the rear wheel steering angles, and the second control means 102 to control the rear wheel steering depending on the car speed, and the front and the rear wheel steering angles, are provided, and the control signals of the first and the second controllers 101 and 102 are output to a rear wheel steering device 2 selectively through a converting means 103. And the converting means 103 is controlled by a timer 104 to output a time-up signal at the time when a specific time has passed from the power source ON time until the detecting accuracy of the yaw rate sensor 5 is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention detects yaw rate,
The present invention relates to an improvement of a rear wheel steering system for a vehicle that controls steering of rear wheels using the yaw rate as a parameter.

[0002]

2. Description of the Related Art Conventionally, in a rear wheel steering system that steers the rear wheels based on only the vehicle speed and the steering angle, when the vehicle turns, the rear wheels generate a slip angle and a lateral force. May be steered or, conversely, the steering of the rear wheels may be delayed. That is,
The driver may travel inside the desired line or the rear wheels may be delayed in turning.

Therefore, as shown in the rear wheel steering system disclosed in Japanese Patent Laid-Open No. 57-44568, a yaw rate generated by a yaw motion around a vertical line passing through the center of gravity of the vehicle is detected by using a yaw rate sensor, and the yaw motion is detected. When a lateral force is exerted on the rear wheels, the rear wheels are steered to achieve proper turning.

[0004]

The yaw rate sensor, however, differs from an immediate response type vehicle speed sensor and a steering angle sensor, which can obtain a stable detection signal in a short time after the power is turned on, unlike the yaw rate sensor after the power is turned on. A stable detection signal cannot be obtained unless time has passed.

That is, since the detection signal that is output varies until the yaw rate sensor of the time-stable type stabilizes, a proper rear wheel steering is performed using the yaw rate until the detection signal of the yaw rate sensor stabilizes. There is a problem that it is difficult to control the above.

The present invention solves the above problem, and controls the steering of the rear wheels according to the detection signals of other detection means without using the yaw rate until the detection accuracy of the yaw rate sensor stabilizes. Thus, it is an object of the present invention to provide a rear wheel steering system for a vehicle that improves the reliability of the rear wheel steering control.

[0007]

In order to achieve the above object, the present invention provides a yaw rate sensor for detecting a yaw rate, and a first control for controlling steering of rear wheels using a detection signal from the yaw rate sensor as a parameter. Means, second control means for controlling steering of the rear wheels in accordance with a detection signal from the detection means other than the yaw rate, and accuracy stabilization corresponding to the time from when the power is turned on until the detection accuracy of the yaw rate sensor stabilizes. The determination means for determining whether or not time has elapsed and the second control means when the power source is turned on are operated, and after it is confirmed by the determination means that the accuracy stabilization time has elapsed, Switching means for switching from the control state of the second control means to the control state of the first control means.

Further, in claim 2, the second control means is:
The steering of the rear wheels is controlled according to the detection signals from the vehicle speed and steering angle detection means.

Further, according to a third aspect of the present invention, the yaw rate sensor for detecting the yaw rate, the control means for controlling the steering of the rear wheels using the detection signal from the yaw rate sensor as a parameter, and the detection accuracy of the yaw rate sensor from the moment the power is turned on are Discriminating means for discriminating whether or not the accuracy stable time corresponding to the time until stabilization has elapsed, and until it is confirmed by the judging means that the accuracy stable time has elapsed,
The control means is provided with restriction means for restricting control of steering of the rear wheels.

[0010]

According to the rear wheel steering system for a vehicle of claim 1,
The steering of the rear wheels is controlled according to the detection signal of the detection means other than the yaw rate until the accuracy stabilization time when the detection accuracy of the yaw rate sensor stabilizes after the power is turned on. After the confirmation, the steering of the rear wheels is controlled by using the yaw rate detected by the yaw rate sensor as a parameter.

Further, according to the vehicle rear wheel steering system of the second aspect, from the moment the power is turned on until the accuracy stabilization time for stabilizing the detection accuracy of the yaw rate sensor elapses, an immediate response type vehicle speed sensor or steering wheel is provided. The steering of the rear wheels is controlled according to the vehicle speed and the steering angle that are the detection signals of the angle sensor, and after it is confirmed that the accuracy stabilization time has elapsed, the yaw rate detected by the yaw rate sensor is used as a parameter for the rear wheels. Steering is controlled.

Further, according to the vehicle rear wheel steering system of the third aspect, the steering control of the rear wheels by the control means is performed from the time when the power is turned on until the accuracy stabilization time during which the detection accuracy of the yaw rate sensor stabilizes. After it is confirmed that the accuracy stabilization time has elapsed, the steering of the rear wheels is controlled using the yaw rate detected by the yaw rate sensor as a parameter.

[0013]

FIG. 2 is a schematic configuration diagram showing an example of a vehicle to which a rear wheel steering system according to the present invention is applied. Front wheel steering device 3
Is for steering the front wheels 9L, 9R based on the steering of the steering wheel 11. The rear-wheel steering device 2 receives the rear wheels 10L and 10R based on the control signal from the control unit 1.
To steer.

On the other hand, there are a vehicle speed sensor 4, a yaw rate sensor 5, a rear wheel steering angle sensor 6, a front wheel steering angle sensor 7 and a brake switch 8 as means for detecting the driving state, and these sensors are turned on, that is, an ignition switch. It turns on by turning on. The vehicle speed sensor 4 detects the vehicle speed V and outputs it to the control unit 1.

The yaw rate sensor 5 is a time-stable sensor that can obtain a stable detection signal when a certain amount of time elapses after the power is turned on, and the yaw rate ψ generated by a yaw motion around a vertical line passing through the center of gravity of the vehicle when turning. Is detected and output to the control unit 1. The rear wheel steering angle sensor 6 detects the steering angle θR of the rear wheels 10L and 10R and outputs it to the control unit 1. The front wheel steering angle sensor 7 detects the steering angle θF of the front wheels 9L, 9R and outputs it to the control unit 1. The brake switch 8 detects that the brake pedal is stepped on (turned on).

The control unit 1 includes a vehicle speed sensor 4
In order to control the steering of the rear wheels 10L and 10R based on the detection signals from the yaw rate sensor 5, the rear wheel steering angle sensor 6, the front wheel steering angle sensor 7, the brake switch 8, etc., a control signal is sent to the rear wheel steering device 2. It is output.

That is, as shown in FIG. 1, the control unit 1 includes a first control means 101, a second control means 102, a switching means 103, and a timer (discriminating means).
104 and a correction means 105 and the like. The first control means 101 controls the steering of the rear wheels 10L, 10R based on the yaw rate ψ, the vehicle speed V, the steering angle θR, and the steering angle θF, and the rear wheel steering device 2 via the switching means 103. The control signal is output to. Second control means 1
Reference numeral 02 controls the steering of the rear wheels 10L and 10R based on the vehicle speed V, the steering angle θR, and the steering angle θF without using the yaw rate ψ, and controls the rear wheel steering device 2 via the switching means 103. I am trying to output a signal.

That is, as shown in the characteristic diagram of FIG. 4, for example, the second control means 102 steers the rear wheels 10L, 10R in the opposite phase direction to the front wheels 9L, 9R at low vehicle speeds such as during turning. In order to improve the turning performance of the vehicle, the rear wheels 10L and 10R are adjusted so that the turning ratio (θR / θF) becomes a negative value.
Control the steering of. In addition, the second control means 102 turns the steering ratio to 0 when the vehicle speed reaches a predetermined value, and the front wheels 9L and 9R.
The rear wheels 10L and 10R are controlled to be held in the neutral position regardless of the steering angle θF. Furthermore, the second control means 10
2 is the rear wheel 1 when the vehicle speed is higher than a predetermined value.
In order to steer 0L and 10R in the same phase direction as the front wheels 9L and 9R to improve the stability of the vehicle, steering of the rear wheels 10L and 10R is controlled so that the steering ratio becomes a positive value.

On the other hand, the first control means 101 controls the steering of the rear wheels 10L, 10R using the yaw rate ψ as a parameter. That is, for example, the target rear wheel steering angle TGθR is obtained from the following equation, and the rear wheels 10L and 10R are controlled so that the steering angle θR becomes the target rear wheel steering angle TGθR.
The steering of L and 10R is controlled.

TGθR = θF (f1 (V) │ψ│-f
2 (V) · | θF |) f1 (V), f2 (V); a function of vehicle speed V, and the rear wheels 10L with the yaw rate ψ as a parameter,
When the front wheels 9L and 9R are steered from a steering angle of zero by steering 10R, the rear wheels 1 immediately after the start of steering of the front wheels.
0L and 10R are steered to the opposite phase side to the front wheels 9L and 9R, and then steered to the same phase side due to the generation of the yaw rate ψ,
So-called phase inversion control can be performed, and both turning performance and directional stability can be achieved.

The switching means 103 operates from the steering control of the rear wheels 10L and 10R by the second control means 102 based on the time-up signal from the timer 104 to the first control means 10.
The steering control of the rear wheels 10L and 10R by 1 is switched. The timer 104 outputs a time-up signal to the switching means 103 when the accuracy stabilization time corresponding to the time from when the power is turned on until the detection accuracy of the yaw rate sensor 5 stabilizes has elapsed.

The correcting means 105 corrects the drift based on the stopped state of the vehicle in order to reduce the detection error due to the drift of the yaw rate sensor 5.

Next, one embodiment of the operation of the above configuration will be described with reference to the flowchart of FIG. When the power is turned on, that is, the ignition switch is turned on, the timer 104 starts operating (step S1).
Then, until the above-described accuracy stabilization time elapses, that is, until the yaw rate sensor 5 stabilizes (NO in step S2), the rear wheels 10L, 10 by the second control means 102.
R steering control is performed (step S3). That is, without using the unstable detection signal of the yaw rate sensor 5, the rear wheel 10 is calculated based on the vehicle speed V, the steering angle θR, and the steering angle θF.
L and 10R steering control is performed.

When the accuracy stabilization time has elapsed (time up) (YES in step S2), the drift of the yaw rate sensor 5 is corrected to reduce the detection error. Therefore, the vehicle speed V is 0 until the vehicle stops. The second control means 10 continues until the brake is turned on (NO in step S4 or step S5).
The steering control of the rear wheels 10L and 10R by 2 is performed (step S6).

After that, when the vehicle speed V becomes 0 and the brake is turned on (YES in both step S4 and step S5), drift correction of the yaw rate sensor 5 is performed, and then the first control means 101 performs the rearward correction. Wheel 10L,
Steering control of 10R is performed (steps S7 and S8).

As described above, after the power is turned on, the detection signals of the yaw rate sensor 5 are not used until the yaw rate sensor 5 becomes stable, and the detection signals of the immediate response type vehicle speed sensor 4 and the steering angle sensors 6 and 7 are used. Since the steering control of the rear wheels 10L, 10R is performed based on the certain vehicle speed V, the steering angle θR, and the steering angle θF, the unstable steering control of the rear wheels 10L, 10R due to the variation of the detection signal of the yaw rate sensor 5 is performed. Is prevented.

Next, another embodiment of the rear wheel steering system according to the present invention will be described with reference to the flowchart of FIG. In this embodiment, in place of the second control means 102 and the switching means 103, the first control means is provided from the time of power-on until the time-out signal is output from the timer 104 (the accuracy stabilization time has elapsed). Rear wheel 10 by 101
In order to regulate the steering control of the L and 10R, for example, a regulation unit that puts the control of the first control unit 101 on standby is provided. That is, the rear wheel 10
L and 10R are held in a neutral position, and only the front wheels 9L and 9R are steered based on the steering of the steering wheel 11.

That is, the timer 104 is turned on when the power is turned on.
Of the rear wheels 10L, 10 until the accuracy stabilization time has elapsed (NO in step S12).
The steering control of R is waited (step S13). That is, the rear wheels 10L and 10R are held in the neutral position, and the front wheels 9L
Only L and 9R are steered.

After the accuracy stabilization time has elapsed (YES in step S12), the vehicle speed V becomes 0, and the rear wheels 10L, 10R are continuously steered until the brake is turned on (NO in step S14 or step S15). The control is on standby (step S16).

Thereafter, when the vehicle speed V becomes 0 and the brake is turned on (steps S14 and S15).
After the drift correction of the yaw rate sensor 5 is performed, the rear wheel 10 by the first control unit 101 is corrected.
L and 10R steering control is performed (steps S17 and S).
18).

In this way, the steering control of the rear wheels 10L and 10R may be performed after the yaw rate sensor 5 becomes stable.

Incidentally, step S13 or step S
The steering control of the rear wheels 10L and 10R by the second control means 102 may be performed by either one of the sixteen.

Further, the above-described accuracy stabilization time may be arbitrarily set as long as it is at least the time from when the yaw rate sensor 5 is turned on until it becomes stable.

[0034]

According to the present invention, the steering of the rear wheels is controlled according to the detection signal of the detection means other than the yaw rate from the time when the power is turned on until the detection accuracy of the yaw rate sensor stabilizes.
When the accuracy stabilization time has elapsed, the steering of the rear wheels is controlled using the yaw rate as a parameter, so it is possible to prevent the steering control of the rear wheels from becoming unstable due to variations in the detection signal of the yaw rate sensor immediately after the power is turned on. Can
On the other hand, during normal operation, the steering control of the rear wheels based on the detection signal of the yaw rate sensor can be properly performed.

That is, until the detection accuracy of the yaw rate sensor becomes stable, the steering of the rear wheels is controlled according to the vehicle speed and the steering angle, which are the detection signals of the immediate response type vehicle speed sensor and the steering angle sensor. It is possible to perform stable rear wheel steering control.

Further, the steering control of the rear wheels is restricted until the detection accuracy of the yaw rate sensor stabilizes, and when the accuracy stabilization time elapses, the yaw rate is used as a parameter to control the steering of the rear wheels, so that the steering becomes unstable. It is possible to reliably prevent the rear wheel steering from being performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a configuration of a control unit of a rear wheel steering system according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a vehicle to which a rear wheel steering device according to the present invention is applied.

FIG. 3 is a flowchart showing an embodiment of the operation of the rear wheel steering system according to the present invention.

FIG. 4 is a characteristic diagram of rear wheel steering control based on a vehicle speed and a steering angle.

FIG. 5 is a flow chart showing another embodiment of the operation of the rear wheel steering system according to the present invention.

[Explanation of symbols]

 1 Control Unit 2 Rear Wheel Steering Device 3 Front Wheel Steering Device 4 Vehicle Speed Sensor 5 Yaw Rate Sensor 6 Rear Wheel Steering Angle Sensor 7 Front Wheel Steering Angle Sensor 8 Brake Switch 9L, 9R Front Wheel 10L, 10R Rear Wheel 101 First Control Means 102 No. 2 control means 103 switching means 104 timer 105 correcting means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B62D 113: 00 137: 00

Claims (3)

[Claims] 1. A yaw rate sensor for detecting a yaw rate, a first control means for controlling steering of rear wheels using a detection signal from the yaw rate sensor as a parameter, and a rear control device for detecting a yaw rate other than the yaw rate. The second control means for controlling the steering of the wheels, the determination means for determining whether or not the accuracy stabilization time corresponding to the time until the detection accuracy of the yaw rate sensor stabilizes after the power is turned on, and the power supply are After being turned on, the second control means is operated, and after it is confirmed by the determination means that the accuracy stabilization time has elapsed, the second control means changes the control state to the first control means. A rear wheel steering system for a vehicle, comprising: a switching means for switching to a controlled state. 2. The vehicle according to claim 1, wherein the second control means controls steering of the rear wheels in accordance with detection signals from vehicle speed and steering angle detection means. Rear wheel steering system. 3. A yaw rate sensor for detecting a yaw rate, a control means for controlling steering of rear wheels using a detection signal from the yaw rate sensor as a parameter, and a time from when the power is turned on until the detection accuracy of the yaw rate sensor is stabilized. The determination means for determining whether or not the accuracy stabilization time has elapsed, and the control means for controlling the steering of the rear wheels until the accuracy stabilization time is confirmed by the determination means. A rear-wheel steering system for a vehicle, characterized by comprising a regulation means for regulating.