An electric power assisted steering apparatus for a vehicle, comprises a
steering mechanism, which operatively connects a steering wheel to the
road wheels of the vehicle, an electric motor operatively connected to
the steering mechanism, a torque sensing means adapted to produce a first
output signal indicative of the torque carried by a portion of the
steering mechanism, a vehicle speed sensing means for producing a second
output signal indicative of the speed of the vehicle, a signal processing
unit adapted to receive the first and second signals and to produce a
torque demand signal representative of a torque to be applied to the
steering mechanism by the motor; and a motor drive stage adapted to
provide a drive current to the motor responsive to the torque demand
signal. The apparatus includes torque limiting means, arranged to limit
the magnitude of the torque to be applied to the steering mechanism to a
maximum of a value that increases in time from a first value to a second
value at a rate that is dependent on the second signal. Additionally or
alternatively, it may be arranged to limit the maximum torque to a value
that increases from a first to a second value at a rate that varies with
time.