Real‐time trajectory resolution for a two‐manipulator machining system

Abstract

AbstractRecent research has considered robotic machining as an alternative to traditional computer numerical control machining, particularly for prototyping applications. However, unlike traditional machine tools, robots are subject to relatively larger dynamic disturbances and operate closer to their torque limits. Combined with inaccurate models of the manipulators and the machining process, joint actuators can often saturate during operation. Once a joint is saturated, tool‐path tracking may not be possible and the blank and/or tool may be damaged. This paper presents a real‐time trajectory planner designed to mitigate the effect of unmodeled disturbances, thus avoiding controller saturation and potential tool/blank damage. The forces acting on the end effectors are monitored to identify the onset of a disturbance so that the system can be slowed down before saturation actually occurs. In response to disturbances, a time‐scaling method reduces the tool speed, thereby reducing the demand on the joint torques and allowing the precomputed process plan to continue. When there is sufficient torque available, the tool speed is returned to its planned magnitude. The effectiveness of the proposed time‐scaling algorithm has been demonstrated with simulations. © 2006 Wiley Periodicals, Inc.