Patent ID: 7100735

Claim:
An electric power assisted steering system comprising: a steering mechanism for a vehicle having a steering wheel and a plurality of road wheels which operatively connects said steering wheel to at least one of said road wheels of said vehicle, a torque sensor arranged to produce a first output signal indicative of a torque carried by a portion of said steering mechanism, a velocity sensor for producing a second output signal indicative of an angular velocity of said steering wheel, a difference means for determining the difference in value of said torque carried by a portion of said column between two points in time to produce a third output signal, an electric motor operatively connected to said steering mechanism, a signal processing unit adapted to receive said first signal, said second signal and said third signal and to produce a torque demand signal representative of a torque to be applied to said steering mechanism by said motor, and a motor drive stage adapted to provide a drive current to said motor responsive to said torque demand signal, wherein said torque demand signal comprises a steering assistance component which is dependent upon said first signal and a damping component that is dependent upon both said first output signal, said second output signal and said third output signal.