Patent attributes
An electric power assisted steering system comprising a steering mechanism which operatively connects a steering wheel to the road wheels of the vehicle, a torque sensing means (6) adapted to produce a first output signal indicative of the torque carried by a portion of the steering mechanism (7), a means (6) for producing a second output signal indicative of the angular velocity of the steering wheel, a difference means (21) for determining the difference in value of the torque carried by a portion of the column between two points in time to produce a third output value, an electric motor (1) operatively connected to the steering mechanism, a signal processing unit (7) adapted to receive the two signals and to produce a torque demand signal representative of a torque to be applied to the steering mechanism by the motor (1), and a motor drive stage adapted to provide a drive current to the motor (1) responsive to the torque demand signal, and in which the torque demand signal (1) includes a damping component that is dependent upon both the first output signal, the second output signal and the third output signal.
