Numerical control device

A numerical control device for controlling a relative displacement between a tool and a workpiece in a machine tool using a command to drive circuitry driving a motor, the numerical control device comprising:

• tool-side displacement measurement circuitry to measure a physical quantity related to a displacement of the tool;
• workpiece-side displacement measurement circuitry to measure a physical quantity related to a displacement of the workpiece;
• drive signal measurement circuitry to measure a drive signal outputted from the drive circuitry to the motor;
• relative displacement calculation circuitry to calculate a relative displacement between the tool and the workpiece from the physical quantity related to the displacement of the tool and the physical quantity related to the displacement of the workpiece;
• relative displacement prediction circuitry to calculate a relative displacement predicted value that is a predicted value of the relative displacement from the drive signal, based on a prediction model representing a relationship between the drive signal and the relative displacement;
• model parameter operation circuitry to generate prediction model parameters constituting the prediction model, based on the drive signal, the relative displacement generated by the relative displacement calculation circuitry, and the relative displacement predicted value;
• and
• command value correction circuitry to output as the command a post-correction position command obtained by correcting a position command to the drive circuitry using the prediction model parameters,
• wherein the model parameter operation circuitry changes the prediction model parameters to reduce a difference between the relative displacement generated by the relative displacement calculation circuitry and the relative displacement predicted value.