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

Claim 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 δf(s) of the front wheel steering angle of the front wheels of the vehicle; second calculating means for calculating the Laplace transform δr(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 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 δr(s)/δf(s)=G.

Claim 2

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 δf(s) of the front wheel steering angle of the front wheels of the vehicle; second calculating means for calculating the Laplace transform δr(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 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 δr(s)/δf(s)=G.

Claim 3

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.

Claim 5

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 δf(s) of the front wheel steering angle of the front wheels of the vehicle; second calculating means for calculating the Laplace transform δr(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 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 δr(s)/δf(s)=G.

Claim 6

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 δf(s) of the front wheel steering angle of the front wheels of the vehicle; second calculating means for calculating the Laplace transform δr(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 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 δr(s)/δf(s)=G.