Patent ID: 7312595

Claim:
A motor control apparatus comprising: a single motor having a single rotor, a single stator, and at least two drive coils wound on the single stator and operable independently to rotate the single rotor; an encoder for producing a pulse signal in synchronism with rotation of the single rotor of the motor, the motor rotating a control object; feedback control means for performing a feedback control for rotating the rotor to a target position by detecting a rotation position of the rotor on a basis of a count of the pulse signal of the encoder and sequentially switching a current supply phase of the motor; at least two systems each of which includes one of the drive coils of the motor and a drive circuit for separately driving the drive coil of the motor in that one of the at least two systems, wherein each of the at least two systems are independently operable from other of the at least two systems, the drive coil and the drive circuit of each system are provided so as to be able to rotate the rotor independently of the drive coil and the drive circuit of the other of the at least two systems, and the drive coil in each of the at least two independently operable systems includes a plurality of phase coils; abnormality diagnosis means for determining presence or absence of an abnormality in the drive coil and/or the drive circuit of each system; and open-loop control means for sequentially switching, when the abnormality diagnosis means has detected an abnormality in one of the at least two systems including a drive coil and a drive circuit, the current supply phase by supplying a drive signal to a drive circuit of a remaining system of the at least two systems by an open-loop control, counting pulses of the drive signal, and rotating the rotor to the target position on a basis of a resulting count.