Real-time failure-tolerant control of kinematically redundant manipulators

This work considers real-time fault-tolerant control of kinematically redun dant manipulators to single locked-joint failures. The fault-tolerance meas ure used is a worst-case quantity, given by the minimum, over all single jo int failures, of the minimum singular value of the post-failure Jacobians. Given any end-effector trajectory, the goal is to continuously follow this trajectory with the manipulator in configurations that maximize the fault-t olerance measure. The computation required to track these optimal configura tions with brute-force methods is prohibitive for real-time implementation, We address this issue by presenting algorithms that quickly compute estima tes of the worst-case fault-tolerance measure and its gradient. Comparisons show that the performance of the best method is indistinguishable from tha t of brute-force implementations. An example demonstrating the real-time pe rformance of the algorithm on a commercially available seven degree-of-free dom manipulator is presented.