Rear wheel turning system for four-wheel steered vehicle

Claim 1

A rear wheel turning system for a four-wheel steered vehicle comprising a rear wheel turning mechanism for turning the rear wheels of the vehicle; a front wheel turning angle detecting means for detecting a turning angle of front wheels θ F and generating a signal indicative thereof; a vehicle speed detecting means for detecting a vehicle speed V and generating a signal indicative thereof; a yaw rate detecting means for detecting a yaw rate Ψ of the vehicle and generating a signal indicative thereof; a yaw acceleration detecting means for detecting a yaw acceleration Ψ of the vehicle and generating a signal indicative thereof; and a control means for receiving signals indicative of the detected values from said front wheel turning angle detecting means, said vehicle speed detecting means, said yaw rate detecting means and said yaw acceleration detecting means and for controlling said rear wheel turning mechanism in accordance with those detected values to turn the rear wheels by a target rear wheel turning angle TGθ R which is defined by a formula: TGθ.sub.R =-K.sub.1 θ.sub.F +K.sub.2 ·V·Ψ+K.sub.3 ·V·Ψ wherein K 1 , K 2 and K 3 respectively represent positive coefficients, and the coefficient K 3 is increased with an increase in the vehicle speed V over a predetermined range of vehicle speed where the coefficient K 2 is constant.