A robust trajectory tracking control of a polishing robot system based on CAM data

Polishing a die that has Free-form surfaces is a Lime-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed in this research. The polishing system is composed of two subsystems, a three-axis machining center and a two-axis polishing robot. The developed polishing system with five degrees of freedom is able to keep the polishing tool normal to the d ie surface during operation. A sliding mode control algorithm with velocity compensation is proposed to reduce tracking errors. Trajectory tracking ex periments showed that the effect of reducing the tracking error by the prop osed sliding mode control is superior to that by the proportional derivativ e control. The polishing data is generated from computer-aided design (CAD) data or from teaching data by PolyCAM, a computer-aided manufacturing (CAM ) system consisting of 4 modules: a geometric modeller, a CAD data exchange module, a polishing data generation module, and a graphic simulator. To ev aluate the performance of the polishing robot system, some polishing experi ments on a shadow-mask die were performed. (C) 2001 Elsevier Science Ltd. A ll rights reserved.