JP2528918B2 - Rear wheel steering angle control device - Google Patents

Description

The present invention relates to a rear wheel steering angle control device for a vehicle.

(Prior Art) As a conventional art of this kind, for example, “4WS (four-wheel steering)” held by the Society of Automotive Engineers of Japan on June 5, 1987.
Vehicles: Frontiers of active control technology "Mazda vehicle speed-sensitive four-wheel steering" described in pages 34-41 of the preprint of the symposium.

(Problems to be Solved by the Invention) However, in such a conventional rear wheel steering control device, when the vehicle speed is constant, δ _r / δ _f = constant, so that stability in steady turning is stable. However, there is a problem that there is little margin for improvement in vehicle responsiveness when an emergency avoidance steering wheel operation or a dynamic steering wheel operation such as slalom traveling is performed.

(Means for Solving Problems) In order to solve the above problems, in the present invention, the vehicle speed and the steering angle of the steering wheel are detected to detect the front wheel steering angle δ _f (S).
For the rear wheel steering angle δ _r (S), In the control device based on (1), the rear wheel control is performed by changing the distance l ₃ between the center of gravity of the vehicle and the position where the side slip angle of the vehicle body is 0 according to the steering angle or steering angular velocity.

(Operation) As described above, according to the present invention, δ _r (S) / δ
_Since the transfer function of _f (S) has a linear / first-order form and the position where the side slip angle of the vehicle body is 0 is set within a predetermined range to perform rear wheel control, the vehicle response to steering wheel steering Improves stability.

In particular, in the present invention, l ₃ is changed according to the steering angle of the steering wheel or the steering angular velocity, so that the degree of freedom in tuning the control constants for improving the agility at low speed is increased, and at any speed including low speed. It is possible to improve agility in a running state (a sharp turning ability).

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view for explaining the present invention. In the figure, 1 is the front wheel, 2 is the rear wheel, 3 is the steering wheel, and g is the center of gravity of the vehicle. Moreover, each code | symbol in a figure is as follows.

M: vehicle weight I: yaw moment of inertia l: wheel base 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 l ₃ : 0 for the center of gravity of the vehicle and the sideslip angle of the vehicle body Distance between positions (plus the rear wheel direction) F ₁ : Front wheel lateral force (for two wheels) F ₂ : Rear wheel lateral force (for two wheels) C ₁ : Front wheel cornering power (for two wheels) C ₂ : Rear wheel cornering power (for two wheels) β ₁ : Front wheel tire side slip angle β ₂ : Rear wheel tire side slip angle V: Vehicle speed v: Lateral movement speed ω: Yaw rate N: Steering gear ratio In the linear two-degree-of-freedom model shown, when the equation of motion is expressed in the form of Laplace transform, If δ ₁ = θ / N (front wheel steering angle) and δ ₂ is the rear wheel steering angle, If the lateral moving speed at the distance l ₃ behind the center of gravity is v ₃ , then v ₃ = v−l ₃ ω ...

Here, the rear wheel steering control function when steering the rear wheels is obtained so that the lateral movement speed v ₃ becomes 0 at the position of l ₃ .

From v ₃ = 0, v = l ₃ ω ... Substituting this into ~ above, The relational expression of is obtained.

In response to the front wheel steering angle δ ₁ , the rear wheel steering angle δ _{2 is changed} to δ ₂ (S) =
When control is performed by the transfer function G (S) that is G (S) · δ ₁ (S), G (S) can be obtained using the above equation.

Re-assemble with ω and δ ₁ , When G is calculated with A and B in the left-side term {}, respectively, here, Therefore, The yaw rate characteristic with respect to the steering angle is Then, the formula becomes as follows.

Therefore, in the present invention, the vehicle speed and the steering angle of the steering wheel are detected, and the rear wheel steering angle δ _r (S) is calculated by the following equation with respect to the front wheel steering angle δ _f (S). And the rear wheel control is performed by changing the distance l ₃ between the center of gravity of the vehicle and the position where the side slip angle is 0 according to the steering angle of the steering wheel or the steering angular velocity.

FIG. 2 and FIG. 3 show an example of a vehicle and a control device therefor embodying the present invention. In the figure, 1L and 1R are left and right front wheels respectively, and 2L and 2R are left and right rear wheels respectively. When the front wheels 1L and 1R can be steered by the steering wheel 3 via the steering gear 4, the front wheel steering angle δ _f is δ, where θ is the steering wheel steering angle and N is the steering gear ratio.
It is represented by _f = θ / N. The rear suspension device including the transverse rings 5L, 5R and the upper arms 6L, 6R also enables the rear wheels 2L, 2R suspended on the rear suspension member 7 of the vehicle body to be steered, and for this purpose, the knuckle arms 8L, The 8Rs are connected to each other by the actuator 9 and side rods 10L and 10R at both ends thereof.

The actuator 9 is a spring-centered backward hydraulic cylinder, and its two chambers are connected to the electromagnetic proportional pressure control valve 12 by pipe lines 11L and 11R, respectively. The control valve 12 is further connected to a hydraulic line 15 and a drain line 16 of a hydraulic source including a pump 13 and a reservoir tank 14, respectively. The control valve 12 is a spring center type 3-position valve, the solenoid lines 12L and 12R are in the OFF state when the pipe lines 11L and 11R are in a non-pressurized state, and a pressure proportional to the energization amount of the solenoid 12L when ON is supplied to the pipe line 11L. Turn on solenoid 12R
It is assumed that the pressure proportional to the hourly current amount is supplied to the pipeline 11R.

The ON / OFF and energizing amounts of the solenoids 12L and 12R are electronically controlled by a controller 17, and the controller 17 includes a digital operation circuit 17a, a digital input detection circuit 17b, a storage circuit 17c, and a D / A as shown in FIG. Converter 17d and drive circuit 17
and e. A signal from the steering angle sensor 18 that detects the steering angle θ of the steering wheel 3 and a signal from the vehicle speed sensor 19 that detects the vehicle speed V are input to the controller 17 via the digital input detection circuit 17b. And θ,
When V is measured and the steering angular velocity is calculated by the digital arithmetic circuit 17a, the values of K, T1 and T2 stored in advance by calculation are recalled from the map based on the values of θ and V. Then, a control output signal corresponding to these values is input to the solenoid portion of the pressure control valve 12 via the D / A converter 17d and the drive circuit 17e to control the rear wheel steering generated hydraulic pressure.

At this time, the controller 17 determines from the steering angle θ which solenoid 12L or 12R of the control valve 12 should be supplied with the current i, and the current i (calculated rear wheel steering angle δ _r ) is supplied to the corresponding pipeline 11L or 11R. Generates a corresponding hydraulic pressure. The actuator 9 strokes in the direction corresponding to this hydraulic pressure and the distance corresponding to this hydraulic pressure, and the rear wheel 2L and
2R can be steered in the corresponding direction by an angle according to the calculation result.

Next, the operation will be described. When traveling on a road with a gentle curve, the steering angle θ and the steering angular velocity are relatively small, so l ₃
Remains the same as before. However, in a running condition where a sharp curve continues continuously, that is, when both θ and θ increase, moving l ₃ closer to the front wheel side than the former will further improve agility and facilitate control.

4 and 5 show an example in which l ₃ is changed according to θ, FIG. 4 shows the case of low speed, and FIG. 5 shows the case of high speed. That is, at low speeds, as θ increases, l ₃ is moved to the front wheel side as shown in FIG. On the other hand, at high speed, θ,
Regardless of the magnitude of, l ₃ is invariant and is located near the center of gravity to ensure the stability of steering response.

(Effects of the Invention) As described above, according to the present invention, δ _r (S) / δ
_Since the transfer function of _f (S) has a linear / first-order form and the position where the side slip angle of the vehicle body is 0 is set within a predetermined range to perform rear wheel control, the vehicle response to steering wheel steering Improves stability.

In particular, in the present invention, l ₃ is changed according to the steering angle of the steering wheel or the steering angular velocity, so that the degree of freedom in tuning the control constants for improving the agility at low speed is increased, and at any speed including low speed. It is also possible to obtain the effect of improving the agility in the running state (crisp turning ability).

[Brief description of drawings]

 1 is a plan view for explaining the present invention, FIG. 2 is a control device diagram of a vehicle to which the present invention is applied, FIG. 3 is a block diagram of the control device, and FIGS. 4 and 5 show the present invention. It is a characteristic view for explanation. 1,1L, 1R …… 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

Claims (1)

(57) [Claims] 1. A vehicle speed detecting means for detecting a vehicle speed and a steering angle of a steering wheel and a steering wheel steering angle detecting means are provided to calculate a rear wheel steering angle δ _r (S) with respect to a front wheel steering angle δ _f (S). In the device for controlling the rear wheel, the distance l ₃ between the center of gravity of the vehicle and the position where the side slip angle of the vehicle body is zero (the rear wheel direction is positive) is changed according to the steering angle of the steering wheel or the steering angular velocity. A rear wheel steering angle control device comprising a control device for performing control. However, S: Laplace operator K, T1, T2: Control constant M: Vehicle weight I: Yaw moment of inertia l: Wheel base 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 wheel cornering power (for two wheels) C ₂ : Rear wheel cornering power (for 2 wheels) V: Vehicle speed.