Patent ID: 8175773

Claim:
An electric power steering system for use in a vehicle incorporated with a vehicle behavior control system, comprising; a steering wheel; a steering mechanism for converting a rotational movement of the steering wheel into a steering movement of front wheels of a vehicle; an electric motor for providing an assist steering torque to the steering mechanism; a steering torque sensor for detecting a manual steering torque applied to the steering wheel; a target current setting unit for setting a target electric current for the electric motor at least according to a detection signal of the steering torque sensor; a corrective current setting unit for setting a corrective electric current for the electric motor according to a state of the vehicle behavior control system; a motor drive control unit for modifying the target electric current for the electric motor according to the corrective electric current, and controlling the electric motor according to the modified target electric current; an actual current detecting unit for detecting an actual electric current fed to the electric motor; a failure detecting unit for detecting a failure of the electric power steering system according to at least an operating condition of the electric power steering system; and a drive restricting unit for restricting a control action of the motor drive control unit when a failure is detected by the failure detecting unit; wherein a criterion for detecting a failure by the failure detecting unit is changed when the vehicle behavior control system is activated.