Naturally-transitioning rate-to-force controller for manipulators

A novel controller, the naturally-transitioning rate-to-force controller (NTRFC), is presented for remote telerobotic systems. The controller involves shared control with a resolved-rate algorithm running concomitantly with a force accommodation algorithm, for all Cartesian axes. When the manipulator motion is unconstrained, it performs like a rate controller, where the hand controller displacement is proportional to the manipulator rate. When the manipulator contacts the environment, the control naturally transitions to a force controller, where the hand controller displacement is proportional to the manipulator force exerted. The force accommodation enables stable equilibrium in contact, with suitable gains. The transition requires no controller change and is thus termed natural. If a force reflecting hand controller is used in conjunction with the NTRFC, the force of the operator´s hand is proportional to the manipulator force exerted. The NTRFC has been shown to possess excellent control characteristics for simulated Space tasks in the laboratory