A framework for large-force task planning of mobile and redundant manipulators

A framework tackling the problem of large wrench application using robotic systems with limited force or torque actuators is presented. It is shown th at such systems can apply a wrench to a limited set of Cartesian locations called force workspace (FW), and its force capabilities are improved by emp loying base mobility and redundancy. An efficient numerical algorithm. base d on 2(n)-tree decomposition of Cartesian space is designed to generate FW. Based on the FW generation algorithm, a planning method is presented resul ting in proper base positioning relative to large-force quasistatic tasks. Additionally, the case of tasks requiring application of a wrench along a g iven path is considered. Task workspace, the set of Cartesian space locatio ns that are feasible starting positions for such tasks, is shown to be a su bset of FW. This workspace is used for identifying prc,per base or task pos itions guaranteeing task execution along desired paths. Finally, to plan re dundant manipulator postures during large-force-tasks, a new method based o n a min-max optimization scheme is developed. Unlike norm-based methods, th is method guarantees no actuator capabilities are exceeded, and force or to rque of the most loaded joint is minimized. Illustrative examples are given demonstrating validity and usefulness of the proposed framework. (C) 1999 John Wiley & Sons, Inc.