System for controlling the steering angle of the rear wheels of a four-wheel-steerable motor vehicle

• US 4,942,532 A
• Filed: 05/17/1988
• Issued: 07/17/1990
• Est. Priority Date: 05/20/1987
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Mori, Kazunori
• Primary Examiner(s): Black, Thomas G.
• Application Number:
  US07/195,078
• Time in Patent Office: 791 Days
• Field of Search: 364/424.01, 364/424.05, 280/91, 180/140, 180/141, 180/142, 180/79.1, 74/388 PS, 318/580
• US Class Current: 701/42
• CPC Class Codes: B62D 7/1581 characterised by comprising an electrical interconnecting system between the steering control means of the different axles
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A system for controlling the steering angle of the rear wheels of a four-wheel-steerable motor vehicle has a controller which steers the rear wheels in a manner to satisfy the following equation: ##EQU1## where: δf(s): Laplace transform of the front wheel steering angle;

δr(s): Laplace transform of the rear wheel steering angle;

A: function A(V) of vehicle speed V;

B: function B(V, φ₀) of vehicle speed V and normal yaw rate gain φ₀ ;

C: function C(V,φ₀) of vehicle speed V and normal yaw rate gain φ₀ ;

D: function D(V,φ₀) of vehicle speed V and yaw rate gain φ₀ ; and

s: Laplace transform variable.

Claims

1. A system for controlling the steering angle of the rear wheels of a four-wheel-steerable motor vehicle comprising:

rear-wheel steering means for steering the rear wheels of the vehicle;

first calculating means for calculating the Laplace transform δ

f(s) of the front wheel steering angle of the front wheels of the vehicle;

second calculating means for calculating the Laplace transform δ

r(s) of the rear heel steering angle of the rear wheels of the vehicle;

third calculating means for calculating a value G according to the equation

space="preserve" listing-type="equation">G=[(BS.sup.2 +CS+D)/(AS+1)] ?(Bs.sup.2 +Cs+D)/(As+1)

wherein;

A is a function A(V) of the vehicle speed V,

B is a function B(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀,

C is a function C(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀,

D is a function D(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀, and

s is the Laplace transform variable; and

control means for controlling the rear-wheel steering means so that the relationship between the front wheel steering angle and the rear wheel steering angle satisfies the equation

space="preserve" listing-type="equation">δ

r(s)/δ

f(s)=G.

3. A system as claimed in claim 1, wherein A, B, C and D are represented by the following equations:

##EQU11## where;

a;

distance between front axle and center of gravity of vehicle

b;

distance between rear axle and center of gravity of vehicle,

Cf;

cornering power of front wheels,

Cr;

cornering power of rear wheels,

M;

mass of vehicle,

V;

vehicle speed,

l;

wheel base,

φ

.sub. ;

normal yaw rate gain,

I;

yaw inertia moment,

ζ

;

damping ratio,

ω

_n ;

natural frequency.

2. A system as claimed in 1 in which said rear-wheel steering means comprises:

a hydraulic actuator;

side rods which connect the hydraulic actuator to the rear wheels;

an electromagnetic proportional pressure control valve which is responsive to said control means and which is connected to said hydraulic actuator to supply the actuator with a pressurized working fluid; and

a fluid supply which is fluidly connected to said control valve.

4. A system for controlling the steering angle of the rear wheels of a four-wheel-steerable motor vehicle comprising:

rear-wheel steering means for steering the rear wheels of the vehicle;

a vehicle speed sensor for generating a signal indicative of the vehicle speed V;

a steering angle sensor for generating a signal indicative of the steering angle of a steering wheel of the vehicle; and

a controller responsive to the signals from the vehicle speed sensor and the steering angle sensor and comprising;

first calculating means for calculating the Laplace transform δ

f(s) of the front wheel steering angle of the front wheels of the vehicle;

second calculating means for calculating the Laplace transform δ

r(s) of the rear wheel steering angle of the rear wheels of the vehicle;

third calculating means for calculating a value G according to the equation

space="preserve" listing-type="equation">G=[(BS.sup.2 +CS+D)/(AS+1)] (Bs.sup.2 +Cs+D)/(As+1)

wherein;

A is a function A(V) of the vehicle speed V,

D is a function B(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀,

C is a function C(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀,

D is a function D(V,φ

₀) of the vehicle speed V and the normal yaw rate gainφ

₀, and

s is the Laplace transform variable;

an

control means for controlling the rear-wheel steering means so that the relationship between the front wheel steering angle and the rear wheel steering angle satisfies the equation

space="preserve" listing-type="equation">δ

r(s)/δ

f(s)=G.