Four-wheel steering control system for vehicle

A steering system for a vehicle having at least steerable front wheels comprising:

• steering input means comprising a steering wheel and a steering sensor for determining a steering input which is an angular displacement of the steering wheel,
• front steering means connected with the steering input means for determining a first output angle from the steering input in accordance with a first transfer characteristic between the steering input and the first output angle and controlling a steering angle of the front wheels so that the steering angle of the front wheels is maintained equal to the first output angle, the first transfer characteristic being a function of steering frequency such that both the gain and phase difference of the first transfer characteristic vary as the steering frequency varies, and
• rear steering means connected with the steering input means for determining a second output angle from the steering input in accordance with a second transfer characteristic between the steering input and the second output angle which is different from the first transfer characteristic, and controlling a steering angle of the rear wheels so that the steering angle of the rear wheels is maintained equal to the second output angle.