Control method and device for steering the rear wheel of a vehicle

Abstract

Various steering coefficients (KB, KC, KG) are decided in accordance with a detected car speed (V), while a correction amount (X) and a correction factor (Y) are determined by fuzzy reasoning in accordance with a detected road surface friction coefficient (.mu.), road surface gradient (.alpha.), and lateral acceleration (G). A reference in-phase steering amount (.delta.RB), equal to a product of a reference in-phase steering coefficient (KB) and a detected steering wheel angle (.theta.H), is corrected by an in-phase correction steering amount (.delta.RC), which is equal to a product of an in-phase steering coefficient (KC) and the detected steering wheel angle (.theta.H), with a delay determined by a time constant (T) calculated from the correction amount (X), to thereby determine a corrected in-phase steering amount (.delta.R). A corrected anti-phase steering amount (.delta.G), obtained by multiplying a reference anti-phase steering amount (.delta.GB), equal to a product of the anti-phase correction coefficient (KG) and a detected steering wheel angular velocity (.theta.HA), by the correction factor (Y), is added to the corrected in-phase steering amount (.delta.R), to thereby obtain a rear-wheel steering amount (.delta.) on which the rear wheels are so steered as to match the road surface friction coefficient, road surface gradient, and lateral acceleration.