APPROXIMATE SOLUTIONS TO UNREACHABLE COMMANDS IN TELEOPERATION OF A ROBOT

A method is presented for finding approximate solutions to unreachable commands for a serial link manipulator. It deals with the difficultie s of joint limits and singularities in a teleoperational, task space c ontroller. Damped least squares with dynamic weighting is used to solv e the inverse Jacobian problem. Previously reported benefits of damped least squares are reviewed, and an additional benefit is demonstrated ; a convergence to an approximate position when the command is outside a singularity-defined workspace boundary. The utility of damped least squares is extended by incorporating dynamic weighting matrices, allo wing an approximate position to be found when the command is outside a joint-limit-defined workspace boundary. A real-time control scheme fo r calculating the dynamic weights and damping factor is presented. A h ardware implementation, that used a six degree of freedom teleoperator , is discussed. In this implementation the approximate position soluti on, a new concept in dealing with workspace boundaries in teleoperatio n, resulted in improved operation. (C) 1998 Elsevier Science Ltd. All rights reserved.