High speed servo control of multi-axis machine tools

Advances in high-speed machining technology, including those in spindle spe eds and cutters, are outpacing advances in the servo control performance of machine tools. To close this gap, new machine tools and improved controls must be developed. Improvements to machine tools under development include special-purpose machine tools, the use of advanced materials, the replaceme nt of ball screws and ways with linear motors and roller guides, and the us e of parallel link actuators. This paper focuses on the control issues that will become increasingly important as these high-speed machining and high- speed machine tool advances are realized. The main issues in high-speed servo control are feed rate planning, and ser vo loop control laws. A method is developed in this paper which takes advan tage of the full performance envelope of each axis in an arbitrary path. Th is near-complete usage of the servo capabilities of a machine tool results in reduced cycle time or reduced path error. A servo loop control law is th en developed that uses the axis performance envelope as well as instantaneo us position, velocity, and acceleration information of the target path and machine axis to improve servo performance in the presence of disturbances. (C) 1999 Elsevier Science Ltd. All rights reserved.