Method and apparatus for controlling a machine tool

An apparatus for controlling a machine tool in which a main spindle on which a tool is mounted and a table that holds a workpiece are moved relative to each other by two or more translation axes and at least one rotation axis to machine the workpiece with the tool, at least one of the main spindle and the table is provided in plural number, wherein

• an error in a position of the tool with respect to the workpiece due to an error of the machine tool is calculated from a position of the tool in presence of the error of the machine tool, which is obtained by a homogeneous coordinate transformation from a tool coordinate system to a workpiece coordinate system with consideration of the error of the machine tool, and an ideal position of the tool, which is obtained by the homogeneous coordinate transformation from the tool coordinate system to the workpiece coordinate system without consideration of the error of the machine tool, and the error in the position of the tool is corrected to calculate a translation axis command value for controlling the translation axis and a rotation axis command value for controlling the rotation axis, the apparatus comprising:
• a selection unit that selects an arbitrary axis configuration having an arbitrary translation axis included in the two or more translation axes and an arbitrary rotation axis included in the at least one rotation axis;
• a translation axis correction value calculation unit that calculates a correction value for the translation axis for correcting the error in the position of the tool in a command value coordinate system of the translation axis, based on a homogeneous coordinate transformation of the error in the position of the tool from the workpiece coordinate system to the command value coordinate system of the translation axis included in the arbitrary axis configuration selected in the selection unit;
• a rotation axis correction value calculation unit that calculates a correction value for the rotation axis for correcting the error in the position of the tool in a command value coordinate system of the rotation axis, based on the error of the machine tool in a rotation direction of the rotation axis included in the arbitrary axis configuration selected by the selection unit;
• and
• an update unit that updates the translation axis command value by adding the correction value calculated by the translation axis correction value calculation unit to the translation axis command value, and updates the rotation axis command value by adding the correction value calculated by the rotation axis correction value calculation unit to the rotation axis command value.