Abstract: A vehicle rear wheel steering control system includes a steering actuator for varying an actual rear wheel steer angle in accordance with a control signal, a steering input sensor, and a controller for producing the control signal in accordance with the steering input. The controller has a first functional section for determining a first desired rear wheel steer angle so as to obtain a flat characteristic of a yaw rate gain with respect to a steering frequency, a second functional section for determining a second desired rear wheel steer angle in accordance with a steering acceleration, and a third functional section for adding the second desired rear wheel steer angle to the first desired rear wheel steer angle.

Abstract: In a 4WD vehicle, a drive control system for controlling a driving force distribution between front and rear wheels is combined with a steer angle control system which applies an auxiliary steering quantity in accordance with a derivative of a steering input, to the front or rear wheels. The steer angle control system is arranged to vary the auxiliary steering quantity responsive to the derivative of the steering input, in accordance with the front and rear wheel speed difference so as to maintain an optimum steering characteristic.