Steering apparatus controller for electric power steering apparatus

A steering apparatus controller for an electric power steering apparatus, wherein the electric power steering apparatus includes an electric motor for generating assist torque for assisting steering of a steering wheel of a vehicle, wherein an actual current that flows through the electric motor is detected by an actual current sensor, and wherein the steering apparatus controller executes a feedback control of an applied voltage to the electric motor based on a detection result of an actual current that flows through the electric motor, the steering apparatus controller comprising:

• a motor drive circuit for driving the electric motor;
• a torque sensor for detecting a steering torque for steering the steering wheel;
• a vehicle speed sensor for detecting a speed of the vehicle;
• a current command value calculator for calculating a present current command value based on the detected steering torque and the detected vehicle speed;
• a current controller for receiving the actual current value detected by the actual current sensor and computing a current command value of a normal state based on the present current command value and the detected actual current value to generate assist torque corresponding to the detected steering torque and the detected vehicle speed;
• and
• a PWM calculator for performing a PWM calculation based on the current command value of the normal state and sending the calculation result to the motor drive circuit as a drive voltage command value,
• wherein the steering apparatus controller controls the electric motor via the motor drive circuit according to the drive voltage command value to obtain assist torque of the motor in accordance with the detected steering torque and the detected vehicle speed, and wherein, when said actual current sensor detects an abnormal decrease of a drive voltage of the sensor, the voltage controller maintains the applied voltage to the electric motor to a drive voltage at a predetermined time before the drive voltage abnormally decreased.