Patent ID: 8901874

Claim:
An electric power steering system, comprising a motor that applies assist force to a steering system, a storage unit within an electronic control unit that stores a resistance map; wherein an induced voltage of the motor is calculated as an estimated induced voltage, based on a current of the motor and a voltage of the motor, and a resistance value of the motor, which is set for calculation, is updated when a magnitude of the estimated induced voltage is equal to or smaller than a determination value that is set in accordance with a level of the current of the motor, wherein the resistance map defines a relation between the current of the motor and the resistance value of the motor, and wherein, when the magnitude of the estimated induced voltage is equal to or smaller than the determination value that is set in accordance with the level of current of the motor, the resistance value of the motor is calculated and the resistance map is updated in the storage unit based on the calculated resistance value of the motor.