Patent ID: 7141948

Claim:
An electromotive power steering system for performing power-assisted steering by applying to a steering mechanism torque generated by a motor, the system comprising: a d-q command value setting unit for determining, for current to be applied to the motor, d-axis and q-axis current command values in a d-q coordinate system; a current detector for detecting a three-phase AC current actually flowing in the motor; a three-phase AC/d-q coordinate transformer for transforming a three-phase AC current detected by the current detector into a d-axis current detection value and a q-axis current detection value in the d-q coordinate system; a voltage controller for controlling a voltage applied to the motor, based on the d-axis current command value and the q-axis current command value determined by the d-q command value setting unit, and on the d-axis current detection value and the q-axis current detection value outputted from the three-phase AC/d-q coordinate transformer; and an abnormality judging unit for judging, by either comparing the q-axis current command value with the q-axis current detection value, or comparing the d-axis current command value with the d-axis current detection value, whether a system-control abnormality has occurred.