JPS6341282A - Actual steering angle control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent vibration of yo rate characteristics in a high speed area, by a method wherein a rear wheel steering angle is controlled by means of given transmission characteristics based on the steering angle of a steering handle, and the constant of transmission characteristics is variably set depending upon a car speed. CONSTITUTION:An arithmetic processing unit 1 is formed with a microcomputer, and a steering angle thetas of a steering handle 8, detected by a handle steering angle sensor 2, is provided as a steering command input. A car speed V detected by a car speed sensor 3 is inputted to the arithmetic processing unit 1, computation processing is effected based on the car speed V and the steering angle thetas to output a command value deltaR of a control amount of the steering angle of each of rear wheels 11 and 12. A rear wheel steering device 5 actuates a hydraulic cylinder 7 in response to the rear wheel steering angle command value deltaR inputted from the arithmetic processing device 1, and is actuated so that the actual steering angle of each of the rear wheels is coincided with the rear wheel steering angle command value deltaR.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vehicle actual steering angle control device for steering rear wheels as the front wheels are steered to improve steering performance.

(Prior Art) Conventionally, in Japanese Patent Application Laid-open No. 60-248481, a detector for the steering angle θ of a steering wheel and an actuator for steering the rear wheels are provided, and the rear wheels are controlled in accordance with the steering of the front wheels. A steering device is disclosed.

This device uses a control circuit to adjust the steering angle δ of the rear wheels.

is controlled so that it has the following relationship with respect to the steering angle θ of the steering wheel.

However, Kd and Ke are constants having a relationship of O<Kd<Ke, T is a time constant, and S is a differential operator.

By controlling the actual rear wheel steering angle in this way, this device turns the rear wheels in the opposite phase to the front wheels for fast steering, improving turning performance, and for slow steering and steady state.
By turning the rear wheels in phase with the front wheels, it is possible to increase the equivalent cornering power of the rear wheels and improve stability.

(Problems to be Solved by the Invention) However, in the conventional device described above, the actual steering angle of the rear wheels is simply controlled based on the steering amount and steering speed of the steering wheel. This will cause such inconvenience.

In other words, the dynamic characteristics of a vehicle change significantly as the vehicle speed changes, so simply turning the rear wheels in response to steering wheel operations as described above will not result in proper steering and turning performance. It is difficult to achieve this condition in all vehicle speed ranges.

This will be explained specifically. The characteristic shown by the solid line in Fig. 7 (bl) is that the front wheels are given a steering angle change as shown in Fig. 7 (a) at a vehicle speed of 50 km/h, and the rear wheels are given the same change as the steering angle changes. The solid line in Figure fb) shows the change in yaw rate when the vehicle is steered, and the solid line in Figure fb) shows the change in the steering angle of the front wheels as shown in Figure (d) when the vehicle speed is 1100 km/h. is given, and the rear wheels are steered as shown by the solid line in FIG.
The change in yaw rate when the front wheels are given a change in steering angle as shown in (g) in the same figure, and the rear wheels are steered as shown by the solid line in (1) in the same figure as a result of the change in steering angle. be.

As can be seen from these characteristics, the response characteristics of the yaw rate become more oscillatory as the speed increases, and the steady-state yaw rate gain is dependent on the vehicle speed.

On the other hand, the ideal yaw rate characteristic is shown in the same figure (bl,
(Non-oscillatory, as shown by the dashed line in eL fhl,
Steady yaw rate gain is low to medium speed range (30-70km/
In h), the bundle is larger than the conventional bundle and can improve turning performance.
In a high speed range (80 km/h or higher), the characteristics need to be such that the yaw rate gain can be reduced to improve stability.

In order to obtain such ideal yaw rate characteristics, as shown by the broken lines in (c), (f), and (1) of the same figure, even for the same steering angle change, the rear wheel steering must be adjusted differently depending on the vehicle speed. A change in angle must be given.

However, in the conventional example, as mentioned above, the vehicle speed is 110
Even if the setting is made so that the rear wheel steering angle changes as shown by the solid lines in Figure 7 (C1, (f) and (11) at 0 km/h, the change in rear wheel steering angle is as shown by the solid lines in Figure 7 (C1, (f), (11)), at a vehicle speed of 50 +w/h (low speed side) , the yaw rate gain decreases, the turning performance deteriorates, and the vehicle speed is 200 km/h.
h (high speed side), not only is the vibrational behavior not sufficiently suppressed, but the overshoot at the initial stage of steering may become large.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes means shown in FIG.

The rear wheel steering mechanism 100 steers the rear wheels 102 in response to the applied control signal Sd.

The steering δ of the rear wheels 102 is controlled by the steering handle 101.
With respect to the steering angle θ, controlled by.

The constant setting means 103 sets the constant Kd in the transfer characteristic.

At least one of Ke and T is variably set depending on the vehicle speed.

(Function) According to the first aspect of the invention, by controlling the steering angle of the rear wheels 102 according to the above-mentioned transmission characteristics, the steering performance and turning performance can be improved as in the conventional example.

Furthermore, by providing the constant setting means 103, the steering angle control of the rear wheels 102 can be corrected according to changes in vehicle speed, and good steering performance is always achieved in all vehicle speed ranges. And the effect of improving turning ability can be obtained.

(Example) The configuration of one embodiment of the present invention is shown in FIG.

The arithmetic processing device 1 is configured using a microcomputer or other electric circuit, and receives a steering angle θ of a steering wheel 8 detected by a steering wheel steering angle sensor 2 as a steering command input.

Furthermore, the vehicle speed ■ detected by the vehicle speed sensor 3 is input to the arithmetic processing device 1, and this vehicle speed ■ and the steering angle θ,
A predetermined calculation process is executed based on the rear wheel 11.1.
A command value (hereinafter referred to as "rear wheel steering angle command value") δ of the steering angle operation amount of No. 2 is output.

The rear wheels 11, 12 are configured to be steered by a hydraulic steering device 7. This hydraulic steering device 7 is controlled by the rear wheel steering device 5.

The rear wheel steering device 5 changes the hydraulic pressure applied to the hydraulic steering device 7 in accordance with the rear wheel steering angle command value δ inputted from the arithmetic processing device 1, so that the actual steering angle of the rear wheels 11° and 12 changes. It operates to match the wheel steering angle command value δ (details are described in Japanese Patent Application No. 59-188153).

The front wheels 9 , 10 are steered by a steering handle 8 by means of a conventional mechanically linked steering device 6 .

The arithmetic processing device 1 has the following functions: S (where Kd and Ke are constants determined according to the vehicle speed, and T
S is a time constant determined according to the vehicle speed, and S is a Laplace operator).

When this arithmetic processing device 1 is constituted by an arithmetic circuit,
For example, as shown in FIG. 3, function generators 20.21.
22, multipliers 23, 24, 25, integrators 26, and subtracters 27, 28.

Furthermore, when the arithmetic processing device 1 is configured using a microcomputer, it is configured to execute processing as shown in FIG.

That is, in step 31, the steering angle θ of the steering wheel 8 and the vehicle speed ■ are read, and in step 32, first,
Vehicle speed is determined from a data table stored in memory in advance.
Find the constants Kd, Ke, and T corresponding to .

These constants Kd, Ke, and T are shown in Figure 7 (cl,
(f), The rear wheel steering angle required to obtain the ideal yaw rate characteristics shown by the broken line in (1) is set in advance for each vehicle speed and stored in the data table. There is. The relationship between these constants Kd, Ke, and T with the vehicle speed is set, for example, as shown in FIGS. 5(a) to 5(C).

Then, in step 33, the transfer characteristic G (S
), the rear wheel steering angle is determined from the steering angle θ, and this is set as the rear wheel steering angle command value δ7.

The specific calculation executed in step 33 is as follows.

x = f xdt - (3)
Woman = −−x+Ke−θ, ...(4) δ
,=Kd-θ,-;c-(5
) The rear wheel steering angle command value δ3 obtained in this way is outputted to the rear wheel steering device 5 in step 34, so that the actual steering angle of the rear wheels 11° 12 becomes equal to the rear wheel steering angle command value δ. controlled by.

Through such control, this embodiment can achieve the results shown in FIG. 6 (al to f
As shown in c), in the middle to low speed range to high speed range, the seventh
The rear wheel steering angle can be controlled with a characteristic that is extremely close to the change in the rear wheel steering angle to obtain the ideal yaw rate characteristic, as shown by the broken line in Figures (C1, (f) and (11)).

Therefore, the vehicle equipped with the device of this embodiment is shown in FIG.
It has the ideal yaw rate characteristics shown by the broken lines in , tel, and fhl, and it is possible to reduce vibrational behavior at high speeds and significantly improve turning performance and stability.

Note that the above transfer characteristic G (s) can be rewritten as
-esT, bi-dimensional transformation, etc.), and each constant Kd, Ke
, T can also be configured as a pushal filter in which T is given as a function of the vehicle speed V.

With such a configuration, generally the above formulas (3) to (5
) Compared to the calculation shown in ), Z-transformation allows processing closer to continuous filter characteristics, and has the advantage of improving responsiveness in a high-speed range.

(Effects of the Invention) The present invention controls the rear wheel steering angle using a predetermined transfer characteristic with respect to the steering angle of the steering wheel, and also sets the constant of the transfer characteristic variably depending on the vehicle speed. This prevents the yaw rate characteristics from oscillating in the high speed range, and allows ideal yaw rate gain to be obtained in the entire vehicle speed range, greatly improving maneuverability and stability.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention; FIG. 2 is a block diagram of an embodiment of the present invention; FIG. 3 is a block diagram showing an example in which the arithmetic processing device in FIG. 2 is configured with an arithmetic circuit; Fig. 4 is a flowchart showing the processing executed when the arithmetic processing unit is configured using a microcomputer, Fig. 5 is a characteristic diagram showing the relationship between constants set in the same embodiment and vehicle speed, and Fig. 6 is A characteristic diagram showing changes in the rear wheel steering angle controlled in the same embodiment at different vehicle speeds, FIG. 7 shows changes in the steering angle at different vehicle speeds in the conventional example,
FIG. 7 is a characteristic diagram showing a yaw rate change and an ideal yaw rate change when the steering angle changes, a rear wheel steering angle change accompanying a conventional steering angle change, and a rear wheel steering angle change to obtain the ideal yaw rate change. . 100... Rear wheel steering mechanism 101... Steering handle 102... Rear wheel 103... Constant setting device θ,... Steering angle δ. ...Rear wheel steering angle G
(s)...Transmission characteristics 1...Arithmetic processing unit 2...Handle steering angle sensor 3...Vehicle speed sensor 5...Rear wheel steering device 7.
... Hydraulic steering device 8 ... Steering handles 11, 12 ... Rear, wheels Patent applicant: Nissan Motor Co., Ltd. Representative Patent Attorney Hidetoshi Sugimura Patent Attorney Oki Sugimura
Figure 1: "4, -" (-- Figure 2

Claims (1)

[Claims] 1. A rear wheel steering mechanism is provided that steers the rear wheels in response to an applied control signal, and the rear wheel steering angle relative to the steering angle of the steering wheel is such that G(s)=Kd− (TS/1+TS)Ke (However, Kd and Ke are constants, T is a time constant, and S is a Laplace operator) in the actual steering angle control device for a vehicle that is controlled to have a transfer characteristic expressed as: An actual steering angle control device for a vehicle, comprising a constant setting means for variably setting at least one of the constants Kd, Ke, and T in the transmission characteristic depending on the vehicle speed. 2. The constant Kd increases in accordance with the vehicle speed in a direction in which the rear wheels are steered in the same phase as the front wheels as the vehicle speed increases. Actual steering angle control device for vehicles. 3. The constant Kd is set in accordance with the vehicle speed so that the rear wheels are steered in a direction opposite to the front wheels when the vehicle speed is below a predetermined vehicle speed. 2
The actual steering angle control device for a vehicle as described in 2. 4. The actual steering for a vehicle according to any one of claims 1 to 3, wherein the time constant T is set to be small when the vehicle speed is high and large when the vehicle speed is low. Angle control device.