Trilateral teleoperation control of kinematically redundant robotic manipulators

Teleoperation control of kinematically redundant robots requires a strategy for resolving their redundancy. A trilateral two-master/one-slave control approach is proposed for delay-free applications in which the first master controls a primary task control frame, e.g. the slave end-effector frame; meanwhile, another master device can manipulate a secondary task frame attached to the slave robot, e.g. to avoid collision with obstacles in the task environment. Any remaining degrees of motion are resolved autonomously. Teleoperation control is achieved in three steps employing joint-space Lyapunov-based adaptive motion/force controllers, a velocity-level redundancy resolution method, and task-space coordinating reference commands. Priority can be given to either the primary or secondary control frame so that the high-priority task can be transparently carried out without interference from the other task. Whenever applicable, the lower-priority task control frame would be restricted to the natural constraints imposed by prioritization or otherwise, decoupling between the tasks is achieved with the use of an arbitrarily weighted pseudo-inverse. Experiments with a planar teleoperation system consisting of two master devices controlling a closed-chain four degree-of-motion redundant slave robot show the feasibility of the approach.