Patent ID: 7486043

Claim:
A controller for a motor adapted to control an operation of a permanent magnet field type rotary motor including a first rotor and a second rotor, which have a plurality of fields made of permanent magnets and which are disposed around a rotating shaft, by carrying out field control as a result of changing a rotor phase difference as a phase difference between the first rotor and the second rotor, the controller comprising: a rotor phase difference changing means for changing the rotor phase difference on the basis of a command value of the rotor phase difference in the field control; a current detecting means for detecting a current flowing through an armature of the motor; a rotor position detecting means for detecting a position of the first rotor; an angular velocity detecting means for detecting an angular velocity of the motor; an induced voltage constant calculating means which converts the motor into an equivalent circuit based on a two-phase AC fixed coordinate system or a two-phase DC rotary coordinate system based on a position of the first rotor and which calculates an induced voltage constant of the motor on the basis of the converted values of a voltage between the terminals of the armature of the motor and a current flowing through the armature in the equivalent circuit and the angular velocity of the motor; a rotor phase difference estimating means for estimating the rotor phase difference on the basis of the induced voltage constant; and an energization controlling means for controlling the energization of the motor on the basis of the estimated value of the rotor phase difference provided by the rotor phase difference estimating means.