Motion Control Techniques for Synchronous Motions of Translational and Rotary Axes

This study proposes motion control techniques which can improve dynamic synchronous accuracy between translational and rotary axes in five-axis machining centres. The proposed techniques consist of servo gain tuning, feed forward controller design, signal delay and backlash compensator, rotational fluctuation compensator and jerk limited acceleration process design. In order to evaluate the effect of proposed techniques, experimental tests are carried out. An experimental apparatus consists of X, Y, and C axes is provided for the experiments. Any control algorithm can be implemented into the experimental apparatus because the system is controlled by a personal computer with a DSP board. Translational X and Y axes are powered by AC servo motors and ball screws. A rotary C axis is powered by an AC servo motor, spur and worm gears. Three kinds of synchronous motions are applied to evaluate the dynamic synchronous accuracies. They are; non-uniformed simultaneous 3-axis motion, simultaneous 2-axis motion of X and C axes, and ellipse shape machining motion using simultaneous 3-axis motion. It is clarified from the experiments various factors including signal delay of rotary encoders influence the dynamic synchronous accuracy between translational and rotary axes, and the proposed motion control techniques can significantly improve the dynamic synchronous accuracy without velocity limitations.