A new approach to the design of teleoperation systems is presented. It is proposed that the teleoperation slave be a coarse-fine manipulator with a fine-motion wrist identical to the teleoperation master. By using a combination of position and rate control, such a system would require only small operator hand motions but would provide low mechanical impedance, high motion resolution and force feedback over a substantial volume. A new teleoperation system, consisting of a conventional manipulator and two identical magnetically levitated wrists, has been developed using this approach and is described in this paper. Aspects of mechanical, system and computational design are discussed. It is shown that the best way to position the slave is by decoupling position and rate control, with the conventional robot controlled in rate mode and its wrist in position mode. Kinesthetic feedback is achieved through wrist-level coordinated force control. Transparency is improved through feedforward of sensed hand forces to the master and environment forces to the slave. To maintain stability, the amount of damping in the system is controlled by the sensed environment forces. Experimental results demonstrating excellent performance are presented.
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