JPH08332972A - Front-rear wheel steering system for vehicle - Google Patents

Abstract

PURPOSE: To stabilize the behavior of a turning vehicle with high lateral acceleration generated by providing a gain adjusting means for making a yaw rate feedback gain larger than one at the normal time upon judging the execution of operation having influence on driving force of a driver during high G turning at high speed. CONSTITUTION: A vehicle speed signal, and an actual yaw rate outputted from a vehicle 1 through a low-pass filter 6 are inputted to a turning lateral G judging circuit 5, and lateral G obtained therein is inputted to an F/B parameter adjusting circuit 7. A yaw rate F/B gain obtained by an F/B compensator 4 from vehicle speed and the difference between the actual yaw rate and a normal yaw rate outputted from a normal yaw rate computing circuit 3, that is, yaw rate deviation, is also inputted to the F/B parameter adjusting circuit 7. The F/B parameter adjusting circuit 7 obtains a feedback tuning gain according to specified procedure. An F/B gain obtained by multiplying the feedback tuning gain by the F/B gain, and an F/F gain outputted from an F/F compensator 2 are added and inputted to a rear wheel control device 11 so as to be inputted as a rear wheel steering angle to the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front and rear wheel steering system for a yaw rate feed bag type vehicle.

[0002]

2. Description of the Related Art Conventionally, a passenger vehicle equipped with a front / rear wheel steering device (4WS) that steers rear wheels by feeding back a yaw rate obtained from a vehicle lateral acceleration and a vehicle speed. ABS that tends to be unstable
It is known that the control parameters of the front and rear wheel steering device are switched when the (anti-lock braking system) is activated (see Japanese Patent Laid-Open No. 4-176780). this is,
When ABS is activated, the signal is taken into the front and rear wheel steering system,
The vehicle speed (wheel speed) immediately before or immediately after the operation is held, and the control parameter at the vehicle speed is used,
When the S operation is performed, the operation is performed so as to have a larger feedback effect than in other cases.

On the other hand, while the vehicle is driving, a high lateral acceleration is generated other than during the ABS operation (high G), and the behavior of the vehicle is likely to be unstable due to an inadvertent operation of the driver during turning. is there. For example, in a front-wheel drive vehicle, the vehicle behavior tends to oversteer when the accelerator is suddenly returned, when the brake is lightly depressed or when the vehicle is downshifted, and when the accelerator is suddenly depressed or the brake is strongly depressed. Vehicle behavior tends to be understeer. Therefore, it has been desired that the effect of the feedback control works even more in the above situation.

However, in order to increase the effect of the feedback control, it is generally sufficient to increase the gain of the feedback parameter. However, the rear wheel steering angle is controlled hypersensitively even by a slight change in the yaw rate due to unevenness of the road surface or the like. This will give the driver an unpleasant feeling.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and suppresses excessive feedback control during normal running and causes high lateral acceleration. The purpose is to stabilize the vehicle behavior during turning.

[0006]

According to the present invention, the rear wheel is fed back with the yaw rate obtained from the lateral acceleration detecting means for detecting the lateral acceleration of the vehicle and the vehicle speed detecting means for detecting the vehicle speed. In a front and rear wheel steering system for steering a vehicle, a high G turning determination means for determining whether the vehicle is turning at a high speed and a high G from the vehicle speed detection means and the lateral acceleration detection means, and a driver's drive The influence determining means for determining that an operation affecting the force is performed, the high G turning determination means and the influence determining means perform an operation that affects the driving force during a high G turning at a high speed. It is achieved by providing a front / rear wheel steering system for a vehicle, which is provided with a gain adjusting means for increasing the gain of the yaw rate feedback when it is determined that the steering wheel is broken.

[0007]

As described above, it is detected that the driver is performing a high-speed turn in which a high lateral acceleration is occurring and that the driver has performed an operation that makes the behavior of the vehicle unstable. By making the gain larger than usual, it is possible to identify the situation where the vehicle behavior becomes unstable and increase the feedback gain only in that case,
Without changing the yaw rate feedback gain at low speed,
It becomes possible not to affect the handling at low speed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a main configuration of a yaw rate feedback type 4WS to which the present invention is applied. In the present embodiment, accelerator operation, brake operation, and shift position change are assumed as operations by the driver such that the behavior of the vehicle becomes unstable during high-speed turning when high lateral acceleration occurs.

A steering wheel angle signal from a steering wheel angle sensor (not shown) is input to the vehicle 1, the feedforward compensator 2 and the reference yaw rate calculator 3. The vehicle speed signal output from the vehicle 1 is input to the feedforward compensator 2, the feedback compensator 4, the turning lateral acceleration determination circuit 5, and the reference yaw rate calculator 3. An actual yaw rate output from the vehicle 1 is also input to the turning lateral acceleration determination circuit 5 via the low-pass filter 6, and a lateral acceleration flag Flag obtained from the vehicle speed and the actual yaw rate by a procedure described later.
G is input to the feedback parameter adjusting circuit 7. The difference between the reference yaw rate output from the reference yaw rate calculator 3 and the actual yaw rate output from the vehicle 1 via the low-pass filter 6, that is, the yaw rate deviation, is also input to the feedback compensator 4. From these vehicle speed and yaw rate deviation, The calculated yaw rate feedback gain is input to the feedback parameter adjusting circuit 7 for adjusting the yaw rate feedback gain.

On the other hand, an accelerator opening signal, a brake signal, and a shift position signal are input to an accelerator operation determination circuit 8, a brake operation determination circuit 9, and a shift change determination circuit 10 by respective sensors (not shown). An accelerator operation determination flag FlagTh, a brake operation determination flag FlagBr, and a shift change determination flag FlagSh, which are obtained from these determination circuits according to the procedure described below, are output and input to the feedback parameter adjustment circuit 7.

The feedback parameter adjusting circuit 7 is
The above flags FlagTh, FlagBr, Fla
The feedback tuning gain P is obtained from gSh, FlagG, and the feedback gain by the procedure described later, and this is multiplied by the feedback gain output from the feedback compensator 4 and output. The feedback gain multiplied by the feedback tuning gain P and the feedforward gain output from the feedforward compensator 2 are subjected to addition processing and input to the rear wheel control device 11 and input to the vehicle 1 as a rear wheel steering angle. It is like this.

The operation procedure of this embodiment will be described below with reference to FIGS.
This will be described with reference to FIG. First, the processing performed in the present embodiment will be generally described. As shown in FIG. 1, the turning lateral acceleration determination circuit 5 determines that a high lateral acceleration is generated during traveling and that a high-speed turning is being performed, and the behavior of the vehicle becomes unstable by the driver. The accelerator operation determination circuit 8, the brake operation determination circuit 9, and the shift change determination circuit 10 determine that an operation, that is, an accelerator operation, a brake operation, or a shift change has been performed, and the feedback parameter adjustment circuit 7 provides feedback based on these. Find the tuning gain P. As described above, this is multiplied by the feedback gain, that is, the yaw rate feedback gain of the rear wheel steering is changed, and the feedback gain multiplied by this feedback tuning gain P and the feedforward gain output from the feedforward compensator 2 are set. The addition processing is performed and the result is input to the rear wheel control device 11, and is input to the vehicle 1 as the rear wheel steering angle.

Next, the processing of the turning lateral acceleration determination circuit 5 will be described. As shown in FIG. 2, first, the vehicle speed V is read (step 11), and it is determined whether or not the vehicle is traveling at high speed depending on whether the vehicle speed V is higher than a predetermined speed V0 (step 12). If there is, the yaw rate γ is read (step 13) and the lateral acceleration α is calculated (step 1)
4) It is determined whether or not the lateral acceleration α is larger than the predetermined lateral acceleration α0 for a predetermined time T0 or longer (steps 15 and 16). If it continues for T0 or longer, a high lateral acceleration occurs. It is judged that the vehicle is turning at high speed.
Set agG to "1" (step 17), otherwise set FlagG to "0" (step 1).
8) Output to the feedback parameter adjustment circuit 7.

In addition, in the accelerator operation determination circuit 8, as shown in FIG.
Read the accelerator opening as shown in (step 21),
The rate of change is calculated by a known pseudo-differential method or the like to remove the influence of noise (step 22), and it is determined whether or not the absolute value of the rate of change exceeds a predetermined value (step 2).
3) If it exceeds, FlagT is assumed to have been operated by the driver so that the behavior of the vehicle becomes unstable.
Set "1" to h (step 24), otherwise set FlagTh to "0" (step 25)
Output to the feedback parameter adjusting circuit 7.

In addition, in the brake operation determination circuit 9, as shown in FIG.
Read the brake signal as shown in (step 31),
Determine if the brake is on (step 3
2) If it is on, it is determined that the driver has operated the brake so that the behavior of the vehicle becomes unstable.
"1" is set to r (step 33), otherwise "0" is set to FlagBr (step 34).
Output to the feedback parameter adjusting circuit 7.

Further, in the shift change determination circuit 10,
As shown in FIG. 5, the shift position signal is read (step 41), it is determined whether or not the vehicle is downshifted (step 42), and if the vehicle is downshifted, the driver's behavior makes the vehicle behavior unstable. Is set and "1" is set in FlagSh (Step 4
3) If not, FlagSh is set to "0" (step 44) and output to the feedback parameter adjusting circuit 7.

On the other hand, in the feedback parameter adjusting circuit 7, as shown in FIG. 6, FlagG is first "1" and FlagTh, FlagBr and FlagS are set.
It is determined whether any of h is “1” (steps 1 and 2), and if so, that is, the behavior of the vehicle is unstable by the driver during high-speed turning when high lateral acceleration occurs. If any of the following operations is performed, the feedback tuning gain P is gradually changed and set (step 3), and the feedback gain output from the feedback compensator is multiplied by the feedback tuning gain P to output. (Step 4). Also, F
flagG is "0" or flag FlagT
h, FlagBr and FlagSh are all “0”
If it is, the feedback tuning gain P is set to "1" (step 5).

Here, when it is determined that the driver has performed any operation that makes the behavior of the vehicle unstable during high-speed turning in which high lateral acceleration is generated by each flag as described above, As shown in part A of FIG. 7, the feedback tuning gain P is set to be gradually increased and set to a target value so that the feedback gain does not change abruptly. On the contrary, when the feedback tuning gain P is larger than "1", the Flag G becomes "0", or all the flags FlagTh, FlagBr, and FlagSh become "0", the part B in FIG. As shown in, the feedback tuning gain P is set to be gradually reduced and set to "1" so that the feedback gain does not change abruptly.

[0020]

As is apparent from the above description, according to the front and rear wheel steering system of the present invention, the vehicle behavior becomes unstable due to the fact that the driver is performing a high-speed turn in which a high lateral acceleration is occurring and the driver. It is possible to identify the situation where the vehicle behavior becomes unstable without changing the yaw rate feedback gain at low speed by detecting that such an operation is performed and increasing the yaw rate feedback gain based on this Only in that case, the feedback gain can be increased. Therefore, it is possible to stabilize the behavior of the vehicle during a turn in which a high lateral acceleration occurs without affecting the handling at low speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a yaw rate feedback type front and rear wheel steering device to which the present invention is applied.

FIG. 2 is a flowchart illustrating a processing procedure of a turning lateral acceleration determination circuit of the front and rear wheel steering device of FIG.

FIG. 3 is a flowchart illustrating a processing procedure of an accelerator operation determination circuit of the front and rear wheel steering device of FIG.

FIG. 4 is a flowchart illustrating a processing procedure of a brake operation determination circuit of the front and rear wheel steering device of FIG.

5 is a flowchart illustrating a processing procedure of a shift change determination circuit of the front and rear wheel steering device of FIG.

6 is a flowchart illustrating a processing procedure of a feedback parameter adjustment circuit of the front and rear wheel steering system of FIG.

7 is a graph illustrating a method of setting a feedback tuning gain P by a feedback parameter adjusting circuit of the front and rear wheel steering system of FIG.

[Explanation of symbols]

 1 Vehicle 2 Feedforward Compensator 3 Reference Yaw Rate Calculator 4 Feedback Compensator 5 Turning Lateral Acceleration Judgment Circuit 6 Low Pass Filter 7 Feedback Parameter Adjustment Circuit 8 Accelerator Operation Judgment Circuit 9 Brake Operation Judgment Circuit 10 Shift Change Judgment Circuit 11 Rear Wheel Control Device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B62D 113: 00 137: 00

Claims (1)

[Claims] 1. A front / rear wheel steering system for a vehicle, wherein a yaw rate obtained from a lateral acceleration detecting means for detecting a lateral acceleration of a vehicle and a vehicle speed detecting means for detecting a vehicle speed is fed back to steer the rear wheels. A high-G turning determination means for determining whether the vehicle is turning at a high speed and a high G from the vehicle speed detection means and the lateral acceleration detection means, and it is determined that an operation affecting the driving force of the driver has been performed. The yaw rate feedback gain is normally set when the influence determining means, the high G turning determination means and the influence determining means determine that an operation affecting the driving force is performed during the high G turning at high speed. A front and rear wheel steering device for a vehicle, comprising: a gain adjusting means for increasing the gain.