Contact Operations Using an Instrumented Compliant Wrist

Teleprogramming was developed as a solution to problems of teleoperation systems with significant time delays [5]. In teleprogramming, the human operator interacts in real time with a graphical model of the remote site, which provides for real time visual and force feedback. The master system automatically generates symbolic commands based on the motions of the master arm and the manipulator/model interactions, given predefined criteria of what types of motions are to be expected. These commands are then sent via a communication link, which may delay the signals, to the remote site. Based upon a remote world model, predefined and possibly refined as more information is obtained, the slave carries out commanded operations in the remote world and decides whether each step has been executed correctly. Contact operations involve the remote site manipulator interacting with the environment, including planned collisions, and motion with contact with the environment. A hybrid position/force control scheme using a instrumented compliant wrist has been demonstrated to be very effective for these types of operations. In particular, switching between position and force modes (when contacting a surface, for example) does not present problems for the system. A brief introduction of teleprogramming and contact operations is presented, including a model of sliding motions and early experimental results. Problems with these early experiments are presented, and solutions discussed. The criteria for an object to slide rather than tip over are presented, relating to the geometry of the object and the applied forces. Finally, methods are presented to match the experimental results to a simple model, to help the remote manipulator to quickly and robustly sense collisions