Controller of rotary axis

A controller of a rotary axis that decelerates the rotary axis to a predetermined speed at a predetermined position, the controller comprising:

• a total movement command calculating unit that calculates a remaining movement amount S2 by subtracting a movement command M1 for each control cycle in every control cycle from a total movement amount S1 from a current position until the predetermined position, in a case in which a positioning request to decelerate the rotary axis to the predetermined speed at the predetermined position is issued;
• a movement command calculating unit that calculates the movement command M1 for each control cycle from the remaining movement amount S2;
• a storage unit that stores in advance data of a braking distance for each rotation number of the rotary axis, the data of the braking distance being based on a maximum torque characteristic with respect to a rotation number of a motor for driving the rotary axis, refers to the data of the braking distance, and provides a current braking distance S3 corresponding to a current rotation number of the rotary axis;
• a deceleration command calculating unit that calculates a speed command V2 of the rotary axis on a basis of the remaining movement amount S2 and the current braking distance S3;
• and
• a speed control unit that causes a speed of the motor to follow the speed command V2,
• wherein the deceleration command calculating unit
• calculates the speed command V2 to maintain the current rotation number of the rotary axis in a case in which a difference S4 between the remaining movement amount S2 and the current braking distance S3 is equal to or greater than a predetermined value, and
• calculates the speed command V2 to start deceleration of the rotary axis in a case in which the difference S4 is less than the predetermined value.