Telerobotic grasping of unmodeled objects

Telerobotic retrieval of objects in unstructured environments requires a manipulation system which is adaptable in the presence of incomplete sensory information. Objects for which no a priori model is available may be grasped using a strategy in which the manipulator arms being to close around the object when it is within reach. During the grasp, various proximity, and tactile sensors are used to monitor the state of the object and alter the grasping strategy. A grasping strategy which accepts data from proximity, tactile and joint-torque sensors drives the manipulators so that the number of manipulator links in contact with the object is maximized, and form-closure about the object is attained. A computer model of NASA´s EVA Retriever telerobot has been developed to test various strategies for grasping objects in space. Tests have shown that a relatively simple strategy is sufficient to successfully grab a large variety of objects. A computer-controlled prototype grasping system is also being constructed to implement the strategies.<>