Motor control apparatus

A motor control apparatus comprising:

• an encoder that outputs a pulse signal every time when a rotor of an electric motor, which rotates a rotatable member of a control subject, is rotated by a predetermined rotational angle;
• an encoder counter that counts up or down the pulse signal of the encoder;
• an exciting phase change counter that counts up or down every time when an exciting phase of the electric motor is changed;
• a feedback controlling unit that executes a feedback control operation of the electric motor by sequentially changing the exciting phase of the electric motor based on a count value of the encoder counter to rotate the rotor until the count value of the encoder counter reaches a feedback target count value, which corresponds to a target rotational position of the rotor;
• a failure monitoring unit that monitors whether a failure exists in the feedback control operation of the electric motor;
• and
• a fail-safe unit that changes the feedback control operation to an open loop control operation when the failure of the feedback control operation is sensed with the failure monitoring unit, wherein when the fail-safe unit executes the open loop control operation, the fail-safe unit sequentially changes the exciting phase of the electric motor without executing feedback of information of the count value of the encoder counter in the open loop control operation and rotates the rotor until a count value of the exciting phase change counter reaches an open loop target count value, which corresponds to the target rotational position of the rotor, wherein:
• when the fail-safe unit changes the feedback control operation to the open loop control operation upon the sensing of the failure of the feedback control operation, the fail-safe unit changes a setting method, which sets the open loop target count value, based on a control state of the electric motor at the time of sensing the failure of the feedback control operation.