OPTIMAL-CONTROL OF MANIPULATORS WITH ANY NUMBER OF PASSIVE JOINTS

This article discusses the problem of controlling robot manipulators w ith passive joints, when the number of passive joints is larger than t he number of active joints. Assuming that brakes and position sensors are available at each passive joint, we investigate the following issu es: (1) what is a sufficient condition for controllability of the pass ive joints via dynamic coupling with the active joints and how can we quantify the controllability at a given configuration; (2) what is the optimal control and locking sequence of the passive joints; and (3) h ow can we control both passive and active joints to an equilibrium poi nt in joint space. We propose an optimal control method and demonstrat e its validity with both simulation and experimental results. The work presented here is significant because it provides a better understand ing and a guideline for utilizing manipulators with passive joints for energy efficiency and fault-tolerant design in applications such as s pace robotics, hyperredundant robots, and sport mechanics. (C) 1998 Jo hn Wiley & Sons, Inc.