Patent ID: 8633663

Claim:
A control device comprising: a sinusoidal command signal generation unit configured to generate a sinusoidal command signal to any one of a position command signal, a speed command signal, and a torque command signal supplied to a permanent magnet synchronous motor; a current value acquisition unit configured to acquire a current value of a current flowing through said permanent magnet synchronous motor; an acceleration value acquisition unit configured to acquire an acceleration value of the permanent magnet synchronous motor; an estimated torque constant calculation unit configured to calculate an estimated torque constant relating to said permanent magnet synchronous motor from any one set of a first set, which consists of an average current obtained by averaging the absolute value of the maximum value of a current feedback value and the absolute value of the minimum value of the current feedback value in each period of the sinusoidal command signal over a plurality of periods and an average acceleration obtained by averaging the absolute value of the maximum value of an acceleration value and the absolute value of the minimum value of the acceleration value in each period of the sinusoidal command signal over the plurality of periods, and a second set, which consists of the sum of the absolute values of the current feedback values over a plurality of periods of the sinusoidal command signal the sum of the absolute values of the acceleration feedback values over a plurality of periods of the sinusoidal command signal, and a predetermined inertia relating to said permanent magnet synchronous motor; and a demagnetization detection unit configured to detect whether or not irreversible demagnetization has occurred in a permanent magnet of said permanent magnet synchronous motor based on a difference between said estimated torque constant and a predetermined torque constant relating to said permanent magnet synchronous motor.