Electric power assisted steering apparatus

A method of controlling an electric power assisted steering apparatus for a vehicle having a steering mechanism, the method comprising the following steps:

• (a) measuring the torque in a part of the steering apparatus;
• (b) calculating a torque demand signal indicative of the torque to be applied to the steering mechanism by an electric motor;
• and
• (c) applying a drive current to the motor in response to the torque demand signal, wherein at least one of the torque and the maximum rate of increase of the torque that can be applied by the electric motor is limited following a shutdown and next following restart, with the at least one of the limit of the torque and the maximum rate of increase of the torque being determined at least in part by information indicative of a state of the system prior to the restart, and, in the event that the information indicates that the system shutdown normally while a drive current was not being provided to the motor prior to restart, the at least one of the limit and the maximum rate of increase of the torque applied is different than that applied in the event that the information indicates that the system shutdown abnormally while a drive current was being provided to the motor prior to the restart.

A power assisted steering apparatus for a vehicle comprising:

• a steering mechanism adapted to operatively connect a steering wheel to road wheels of a vehicle;
• a motor operatively connected to the steering mechanism;
• a torque sensor adapted to produce a first output signal indicative of a torque carried by a portion of the steering mechanism;
• a vehicle speed sensor adapted to produce a second output signal indicative of a speed of the vehicle;
• a signal processor responsive to the first output signal and the second output signal for producing a torque demand signal that is representative of at least one of a torque and a rate of increase of torque to be applied by the motor to the steering mechanism following a shutdown and restart of the apparatus, wherein the signal processor produces different torque demand signals depending upon whether the shutdown occurred (1) normally while a drive current was not being provided to the motor prior to restart or (2) abnormally while a drive current was being provided to the motor prior to the restart;
• and
• a motor controller that provides a drive current to the motor in response to the torque demand signal.

A power assisted steering apparatus for a vehicle having a steering mechanism adapted to operatively connect a steering wheel to road wheels of a vehicle, the power assisted steering apparatus comprising;

• a motor adapted to be operatively connected to a steering mechanism;
• a torque sensor adapted to produce a first output signal indicative of a torque carried by a portion of the steering mechanism;
• a vehicle speed sensor adapted to produce a second output signal indicative of a speed of the vehicle;
• a signal processor responsive to the first output signal and the second output signal for producing a torque demand signal that is representative of at least one of a torque and a rate of increase of torque to be applied by the motor to the steering mechanism following a shutdown and restart of the apparatus, wherein the signal processor produces different torque demand signals depending upon whether the shutdown occurred (1) normally while a drive current was not being provided to the motor prior to restart or (2) abnormally while a drive current was being provided to the motor prior to the restart;
• and
• a motor controller that provides a drive current to the motor in response to the torque demand signal.