JPH01145273A - Device for controlling rear wheel steering angle - Google Patents

Abstract

PURPOSE:To improve quickness in low speeds and response stability in medium and high speeds by modifying the distance between the center of gravity of vehicle and a position making the side slip angle of a vehicle body zero depending on vehicle speeds in a device wherein the rear wheel steering angle is controlled against front wheel steering angle based on vehicle speeds and steering angle. CONSTITUTION:When control constants operated by a formula I be K, T1 and T2, the steering angle theta of a handle and vehicle speeds V are detected by a steering angle sensor and a vehicle speed sensor respectively, the rear wheel steering angle deltar(S) is controlled against the front wheel steering angle deltaf(S) based on a formula II. In this case, when the distance between the center of gravity of a vehicle and a position making the side slip angle of a vehicle of a vehicle body zero is l3 (the direction toward rear wheels shall be positive), the distance l3 is modified depending on vehicle speeds so as to control the rear wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering angle control device for a vehicle.

(Prior art) This type of conventional technology includes, for example, the preprint collection of the "Frontline of near-active control technology for r4WS (four-wheel steering) vehicles" symposium held by the Society of Automotive Engineers of Japan on June 5, 1986. There is something disclosed in "Mazda Vehicle Speed Sensitive Four-Wheel Steering J" described on pages 34-41.

(Problems to be Solved by the Invention) However, in such a conventional rear wheel steering angle control device, if the vehicle speed is constant, δf/δ.

= constant, which improves stability in steady turns, but 1! However, there has been a problem in that the responsiveness of the vehicle is only slightly improved when evasive steering operations and dynamic steering operations such as slalom driving are performed.

(Means for Solving the Problem) In order to solve the above-mentioned problem, the present invention detects the vehicle speed and the steering wheel steering angle, and calculates the front wheel steering angle δt (S).
The distance between the center of gravity of the vehicle and the position where the sideslip angle of the vehicle body is set to 0 is obtained by setting the rear wheel steering angle δf (S) to the following formula. A control device is provided that controls the rear wheels by changing the speed of the vehicle according to the vehicle speed.

(Function) As described above, according to the present invention, δf (S)/δt
Since the transfer function of (S) is in the linear/linear form and the position where the sideslip angle of the vehicle body becomes 0 is set within a predetermined range to perform rear wheel control, the response of the vehicle to steering wheel steering is Improved stability.

In particular, in the present invention, the distance between the center of gravity of the vehicle and the position where O is the sideslip angle of the vehicle body! 3 is changed according to the vehicle speed, it is possible to achieve both low speed agility and mid-high speed response stability at a high level.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory plan view of the present invention, and in the figure 1 is a front wheel;
2 is the rear wheel, 3 is the steering wheel, and g is the center of gravity of the vehicle. Further, each reference numeral in the figure is as follows.

M: Vehicle weight ■: Yaw moment of inertia l: Wheelbase a: Distance between the center of gravity of the vehicle and the center of the front wheels b: Distance between the center of gravity of the heavy vehicle and the center of the rear wheels 2: The sideslip angle between the center of gravity of the vehicle and the vehicle body is assumed to be 0. Distance P between the positions: Front wheel lateral force (2 wheels) F2: Rear wheel lateral force (2 wheels) C8: Front wheel cornering power (2 wheels) C2: Rear wheel cornering power (2 wheels) β1: Front tire side slip angle β2: Rear tire side slip angle ■Second vehicle speed■=lateral movement speed ω: Yaw rate N Steering gear ratio In the linear two-degree-of-freedom model shown in Figure 1, the equation of motion is Laplace-transformed. Expressed as, here δ1=θ/N
(front wheel steering angle), and δ2 is the rear wheel steering angle. (2) Now, if the lateral movement speed at the distance 23 behind the center of gravity is F3, v, = v - f, ω ~ (2).

Here, so that the lateral movement speed v3 becomes 0 at position 23,
Find the rear wheel steering control function when steering the rear wheels.

■, from =0, v=j! , ω −■. By substituting this into the above-mentioned equations (1) to (2), the following relational expressions are obtained.

In response to the front wheel steering angle δ1, the rear wheel steering angle δ2 is set to 62(S)=
Transfer function G (S) that becomes G (S) ・δ1 (S)
When controlling by G (
S) can be obtained.

Regroup with ω and δ1, If we calculate G by setting the terms () on the left as A and B, respectively, we get (act-bczG)A=(60C2G)Bwhere, Molecule of G = aC, A-C, B Denominator of G = bCzA + CJ Therefore, ・－・■ The yaw rate characteristic with respect to the steering wheel angle is ω 1 ω θ　N　δ1 M(13S+V)+□ ■ here Then, the formula 0 becomes as follows.

Therefore, in the present invention, the vehicle speed and the steering wheel steering angle are detected, and the front wheel steering angle δf (S) is controlled based on the front wheel steering angle δf (S). The distance! , is changed according to the vehicle speed to control the rear wheels.

FIG. 2 and FIG. 3 show an example of a vehicle and its control device implementing the present invention. In the figure, IL and IR are left and right front wheels, respectively, and 2L and 2R are left and right rear wheels, respectively. Front wheel I
L and IR can be steered by the steering wheel 3 via the steering gear 4, and the front wheel steering angle δf is determined by the steering wheel steering angle θ and the steering gear ratio N.
Then, it is expressed as δf=θ/N. A rear wheel 2L is suspended on a rear suspension member 7 of a vehicle body by a rear suspension device including transverse links 5L, 5R and upper arms 6L, 6R.

2R can also be steered, and for this purpose, the knuckle arms 8L and 8R of the rear wheels are interconnected by an actuator 9 and side rods IOL and IOR at both ends thereof.

The actuator 9 is a spring center type double-acting hydraulic cylinder, and its two chambers are connected to an electromagnetic proportional pressure control valve 12 through conduits 11L and IIR, respectively. The control valve 12 is further connected to a hydraulic pressure line 15 and a drain line 16 of a hydraulic pressure source including a pump 13 and a reservoir tank 14, respectively. The control valve 12 is a spring center type 3-position valve, and when both solenoids 12L and 12ROOFF, the conduit 11L and IIR are in a non-pressure state, and a pressure proportional to the ON/N path energization amount of the solenoid 12L is supplied to the conduit 11L, and the solenoid 12R is turned off. ON
It is assumed that a pressure proportional to the amount of N-way energization is supplied to the conduit 11R.

The ON/OFF and energization amounts of the solenoids 12L and 12R are electronically controlled by a controller 17, and as shown in FIG. 3, this controller 17 includes a digital calculation circuit 17a,
Digital input detection circuit 17b, storage circuit 17c, and D
It consists of a /A converter 17d and a drive circuit 17e. The controller 17 receives a signal from a steering angle sensor 18 that detects the steering angle θ of the steering wheel 3, and a vehicle speed V.
The signals from the vehicle speed sensor 19 that detects the vehicle speed are respectively inputted through the digital input detection circuit 17b. The digital calculation circuit 17a of the controller 17 calculates the above equation 0 based on the input information and the storage constant of the storage circuit 17c, and converts the digital signal related to the rear wheel steering angle δf corresponding to the calculation result into an analog signal using the D/A converter 17d. Convert to signal. This analog signal is converted by the drive circuit 17e into a current i corresponding to the rear wheel steering angle δf, and is supplied to the control valve 12.

At this time, the controller 17 determines which solenoid 12L or 12R of the control valve 12 should be supplied with the current i from the steering angle θ, and supplies the current i to the corresponding conduit 11L or IIR.
(calculated rear wheel steering angle δf). The actuator 9 strokes in a direction according to this hydraulic pressure and by a distance according to this hydraulic pressure, and steers the rear wheels 2L and 2R in the corresponding direction by an angle according to the calculation result via the side rods IOL and IOR. Can be done.

Next, the effect will be explained. By changing 13 according to the vehicle speed, various vehicle characteristics can be obtained, and the following example shows one example thereof.

That is, at low speeds to increase low speed agility! 3 is brought forward from the center of gravity, and as the vehicle speed increases, 23 is gradually shifted to the rear in order to ensure stability.

FIG. 4 is a graph showing the dependence of TI and T2 on vehicle speed in the embodiment of the present invention.

Further, FIG. 5 shows a graph showing changes depending on the vehicle speed of 23.

(Effects of the Invention) As explained above, according to the present invention, δf (s
) /δf (s) is in the linear/first-order form, and the rear wheel control is performed by setting the position where the sideslip angle of the vehicle body is 0 within a predetermined range, so that the vehicle's response to steering wheel steering is Improves responsiveness and stability.

In particular, in the present invention, the distance between the center of gravity of the vehicle and the position where the sideslip angle of the vehicle body is 0 is 2. By changing the speed according to the vehicle speed, it is possible to achieve both low-speed agility and mid-to-high speed response stability at a high level.

[Brief explanation of the drawing]

FIG. 1 is a plan view for explaining the present invention, FIG. 2 is a diagram of a control device for a vehicle to which the present invention is applied, FIG. 3 is a block diagram of the control device, and FIGS. It is various characteristic diagrams for explanation. 1, IL, IR...front wheel 2, 2L, 2R...rear wheel 3...steering wheel 4...steering gear 5L, 5R...transverse link 6L, 6R...
- Upper arm 7... Rear suspension member 9... Actuator 12... Electromagnetic proportional pressure control valve 17... Controller 18... Steering angle sensor 19... Vehicle speed sensor Figure 4 Figure 5 I length;

Claims (1)

[Claims] 1. Detect the vehicle speed and steering angle, and determine the front wheel steering angle δ.
For _f(S), rear wheel steering angle δ_r is expressed as (S) by the following formula δ_
r(S)/δ_f(S)=K+T1・S/1+T2・S
A control device that performs rear wheel control by changing the distance l_3 (rear wheel direction is positive) between the center of gravity of the vehicle and the position where the sideslip angle of the vehicle body is 0 according to the vehicle speed. A rear wheel steering angle control device. However, S: Laplace operator K, T1, T2: control constant K=C_1{aMV^2+C_2l(l_3-b)}/
C_2{bMV^2+C_1l(l_3-a)}T1=
C_1V(aMl_3-I)/C_2{bMV^2+C_1l(l_3+a)}T2=
V(bMl_3+I)/bMV^2+C_1l(l_3+a) M: Vehicle weight I: Yaw moment of inertia l: Wheelbase a: Distance between the center of gravity of the vehicle and the center of the front wheels b: Distance between the center of gravity of the vehicle and the center of the rear wheels C_1: Front wheels Cornering power (2 wheels) C_2:
Rear wheel cornering power (2 wheels) V: Vehicle speed.