Motor Control Device

A motor control device having:

• a power conversion unit that converts DC power into three-phase AC power and outputs the converted three-phase AC power to a motor,
• a rotation angle sensor that detects the phase of the motor, and
• an AD converter that converts an analog signal outputted from the rotation angle sensor into a digital signal,
• the motor control device comprising a rotational-position detection unit that includes:
• a recording unit that records a plurality of sets of data which includes a sine wave signal and a cosine wave signal of the phase of the motor which are included in the digital signal;
• a calibration necessity determination unit that determines, on the basis of the plurality of sets of data, whether or not calibration of the phase of the motor is required;
• and
• an elliptical approximation unit that, in a case where calibration of the phase of the motor is required, performs elliptical approximation on the basis of the plurality of sets of data and calculates an elliptical constant;
• a calibration unit that calibrates the sine wave signal and the cosine wave signal on the basis of the elliptical constant;
• and
• a phase computation unit that computes the phase on the basis of the sine wave signal and the cosine wave signal calibrated by the calibration unit,
• wherein the plurality of sets of data are distributed to a predetermined number of divided regions spanning one or more electrical angle cycles.