Device and method of controlling machine tool, to control synchronized operation of spindle axis and feed axis

A controller of a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the controller comprising:

• a numerical control section configured to prepare a spindle-axis command and a feed-axis command based on a tapping program;
• a spindle-axis control section configured to control a rotational motion of the spindle axis in accordance with the spindle-axis command;
• a rotation detecting section configured to detect a rotational position of the spindle axis;
• and
• a feed-axis control section configured to control a feed motion of the feed axis in accordance with the feed-axis command, based on the rotational position;
• the numerical control section comprising:
• a spindle-axis command outputting section configured to obtain, from the tapping program, a total rotation amount and a maximum rotation speed of the spindle axis during a period when the spindle axis operates from a starting position to a target position, and to send the total rotation amount and the maximum rotation speed as the spindle-axis command to the spindle-axis control section;
• the spindle-axis control section comprising:
• an initial-motion control section configured to make the spindle axis perform an accelerated rotation at maximum capacity from the starting position, by a velocity control in which the maximum rotation speed is set as a target value;
• a maximum-acceleration detecting section configured to detect a maximum acceleration of the spindle axis during the accelerated rotation at maximum capacity, based on the rotational position;
• a residual rotation-amount detecting section configured to detect a residual rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the target position, based on the total rotation amount and the rotational position;
• a current-speed detecting section configured to detect a current speed of the spindle axis based on the rotational position;
• a decelerating-motion control section configured to execute a velocity control for making the spindle axis perform a decelerated rotation at maximum capacity so as to reach a predetermined intermediate speed, after the accelerated rotation at maximum capacity;
• a positioning-motion control section configured to execute a position control for making the spindle axis perform a decelerated rotation so as to reach the target position, after the spindle axis reaches the intermediate speed;
• a flux-content predicting section configured to predict an actual motor-flux content at the intermediate speed, based on a motor-flux-content command value for making the spindle axis reach the intermediate speed;
• and
• a deceleration determining section configured to determine a deceleration during the decelerated rotation by the position control, based on the maximum acceleration, the motor-flux-content command value and the motor-flux content;
• the positioning-motion control section configured to execute the position control, based on the residual rotation amount, the current speed and the deceleration.