Patent ID: 7696709

Claim:
A controller for an electric power steering apparatus comprising a motor which applies a steering assist force to a steering mechanism, the controller comprising: a torque command value calculating portion which calculates a torque command value based on a steering torque generated in a steering shaft, and a vehicle speed; a current command value calculating portion which calculates a current command value for the motor based on the torque command value, the motor being controlled based on the current command value; and a cogging torque compensation value calculating portion which calculates a cogging torque compensation value for the motor, wherein the current command value is corrected based on the cogging torque compensation value, and wherein the current command value calculating portion calculates a d-axis current command value and a q-axis current command value in d-q axes of the motor, and corrects the d-axis current command value based on the cogging torque compensation value so as to weaken flux of the motor.