Failure diagnosing device of drive mechanism, method of diagnosing failure, and mechanical apparatus provided with failure diagnosing device

A failure diagnosing device configured to diagnose a failure of a drive mechanism of a mechanical apparatus provided with:

• a body including a motor, a speed reducer configured to slow down rotational power of the motor, and an operation part configured to operate by the rotational power slowed down by the speed reducer;
• and
• a vibration-proof controller configured to perform a vibration-proof control to prevent vibration of the body,
• wherein the drive mechanism includes the motor and the speed reducer,
• wherein the failure diagnosing device sends a command for suspending the vibration-proof control to the vibration-proof controller of the mechanical apparatus, then identifies an acceleration-and-deceleration period during which operation of the mechanical apparatus of which the vibration-proof control is suspended accelerates and decelerates, and determines whether the drive mechanism indicates a sign of failure based on a change in a frequency spectrum of load current of the motor or a current value having a correlation with the load current (hereinafter, referred to as “the motor current”) to a change in a rotational speed of the motor, during the acceleration-and-deceleration period.