Machine learning device for machine tool and thermal displacement compensation device

A machine learning device that optimizes a coefficient of an equation established in advance for estimating a thermal displacement amount of a machine element that thermally expands by way of machine learning, based on operating state data representing an operating state of the machine element of a machine tool having the machine element, wherein the equation is not an equation based on weighting by a neural network, but is an equation which defines time and operating state data of the machine element as variables, and includes integration by a predetermined coefficient or an exponent, the machine learning device comprising:

• a computer including processor and a non-transitory memory having stored thereon executable instructions, which when executed, causes the computer to function as:
• a data acquisition unit for acquiring the operating state data of the machine element;
• a thermal displacement amount acquisition unit for acquiring measured values for a thermal displacement amount of the machine element;
• a storage unit for storing the operating state data of the machine element acquired by the data acquisition unit and the measured values for the thermal displacement amount of the machine element acquired by the thermal displacement amount acquisition unit as training data associated with each other as a label;
• an equation setting unit for setting a coefficient of the equation for calculating the thermal displacement amount of the machine element, by performing machine learning of the coefficient related to the equation without using a neural network, based on the operating state data of the machine element and the measured values for the thermal displacement amount of the machine element;
• a thermal displacement amount calculation unit for calculating an estimated value for the thermal displacement amount of the machine element, by substituting operating state data of the machine element within a predetermined time period stored as training data in the storage unit, into the equation set by the equation setting unit;
• and
• a determination unit for determining whether a difference between the estimated value for the thermal displacement amount of the machine element within the predetermined time period calculated by the thermal displacement amount calculation unit and the measured value for the thermal displacement amount of the machine element within the predetermined time period stored as training data in the storage unit is no more than a predetermined threshold,
• wherein the equation setting unit sets again the coefficient of the equation in a case of being determined that the difference is not no more than a predetermined threshold by way of the determination unit, and sets said coefficient of the equation as an optimal equation in a case of being determined that the difference is no more than a predetermined threshold by way of the determination unit.