High Performance Motion Control of Rotary Axis for Simultaneous Multi-axis Controlled Motions

Abstract

This paper describes the motion control techniques of rotary tables for 5-axis machining centers. Especially, in the machining of complex shapes such as impellers, three translational axes and two rotary ones are simultaneously controlled. A tilting rotary table powered by the worm gear is generally applied as the rotary axes for the 5-axis machining centers, and various causes of inaccuracy exist in the rotary axes. In this study, the causes of inaccuracy are investigated by the experiments and simulations. As the result, it is clarified that the main causes of inaccuracy : servo response, fluctuation of rotational velocity, backlash and the signal delay of rotary encoder. Motor torque saturation of the rotary axis also yields a problem. Based upon the investigated results, some compensators for the problems were proposed. In order to confirm the effectiveness of the proposed compensators, the compensators were applied to an experimental set-up including a rotary axis. As the results, it is clarified that the proposed compensators can much improve the synchronous accuracy.