Active end effector control of a low precision robot in deburring

An active end effector is developed to improve precision in robotic deburring. The design objectives are obtained from a dynamic analysis of the combined system of robot arm, end effector, and deburring process dynamics. The unit allows robot-independent positioning, over a range of ±15 mm in two orthogonal directions with an accuracy of better than 0.01 mm and a bandwidth of 20 Hz. A combination of d.c. servo motors with linear ball screws achieves both high precision and a large mechanical advantage. A high quality chamfer is obtained by performing position adjustments normal to the part edge for constant cutting force. An extended discrete PID controller based on an ARMAX plant model is designed and simulated off-line prior to real-time implementation. In real-time force control tests, the active end effector system is shown to improve the precision of a PUMA-560 robot by an order of magnitude over the open-loop case.