Patent ID: 8423245

Claim:
An electric power steering control apparatus comprising: a steering torque detection section that detects steering torque generated by a driver of a vehicle; a motor that generates assist torque to assist the steering torque; a rotational speed detection section that detects the rotational speed of the motor; a torque control section that calculates an assist torque current corresponding to the assist torque based on the steering torque; and a damping control section that calculates a damping current to be added to the assist torque current for suppressing vibrations generated in a steering system of the vehicle; wherein the damping control section reduces a damping control gain for calculation of the damping current when a steering wheel is in a steering holding state or in a slight steering state that occurs when the rotational speed of the motor is equal to or less than a predetermined speed and there is less movement of the steering wheel, wherein the rotational speed detection section comprises: at least one of a current detection section and an addition section; a voltage calculation section; a rotational speed estimation section; a current detection section; a voltage detection section; and wherein the current detection section detects a motor drive current to be supplied to the motor; the addition section calculates a target motor current to be supplied to the motor by adding the assist torque current and the damping current to each other; the voltage calculation section calculates a target motor voltage to he impressed to the Motor; the rotation speed estimation section estimates the rotational speed of the motor based on the target motor current or the motor target voltage, and based on the motor drive current; the voltage detection section detects a motor drive voltage to be impressed to the motor; and the rotation speed estimation section estimates the rotational speed of the motor based on the motor drive current and the motor drive voltage.