Patent ID: 8660752

Claim:
An electric power steering system that includes a motor which is driven based on a target current value computed in line with a steering wheel torque exerted by a driver, and that alleviates a driver's steering effort using an assistant torque generated by the motor, comprising: an overheat protection current value arithmetic unit that computes an overheat protection current value to which a current flowing into the motor is limited; and an overheat protection control unit that limits the current, which flows into the motor, on the basis of the computed overheat protection current value, suppresses heat dissipation caused by the current flowing into the motor, and thus protects onboard equipment, wherein information relevant to the computed overheat protection current value is stored, and whether a newly computed overheat protection current value is abnormal is decided based on comparison of the newly computed overheat protection current value with the stored information relevant to the overheat protection current value.