Workpiece mass estimation device

A workpiece mass estimation device for estimating a mass of a workpiece, for a machine comprising:

• a workpiece loading unit on which the workpiece is loaded;
• a motor comprising a rotor and a stator for rotating the rotor;
• a transmission mechanism for transmitting a motor output as a force for rotating the rotor to the workpiece loading unit;
• a sensor for detecting motor information indicating a state of the motor;
• and a motor control unit for controlling the motor based on the detected motor information, wherein the machine drives a driven object comprising the rotor, the transmission mechanism, the workpiece loading unit, and the workpiece by the motor output,
• the workpiece mass estimation device comprising:
• an oscillation unit configured to command the motor control unit to perform sweep oscillation that oscillates the motor output and varies an oscillation frequency;
• a calculation unit configured to, based on the motor information detected at a plurality of detection time points within an execution period of the sweep oscillation, calculate a total inertia as an inertia of the driven object for each detection time point;
• an identification unit configured to identify a time point of an oscillation frequency at which it is determined that a change in the total inertia accompanying a change to an adjacent oscillation frequency is minimized within the execution period;
• and
• an estimation unit configured to estimate the mass of the workpiece by calculating an inertia of the workpiece by subtracting an inertia of a general driven object comprising the rotor, the transmission mechanism, and the workpiece loading unit from the total inertia corresponding to the identified time point.