Abnormality determination device and abnormality determining method

An abnormality determination device comprising:

• an oscillating signal sending unit configured to send out an oscillating signal which causes a rotary shaft of a servomotor to rotate and swing in a predetermined pattern, to a motor control unit configured to control the servomotor;
• a measuring unit configured to measure a physical quantity representing a state of the servomotor when the rotary shaft is swung;
• a comparing unit configured to compare a measurement signal of the measured physical quantity with a reference signal that is configured to represent a periodically varying value corresponding to the oscillating signal, to thereby calculate a difference therebetween;
• and
• an abnormality determination unit configured to determine an occurrence of an abnormality in a drive system based on a comparison result from the comparing unit,
• wherein the abnormality determination unit is configured to determine that the drive system is abnormal when the difference is equal to or greater than a threshold.