A PHYSIOLOGICAL METHOD FOR RELAYING FRICTIONAL INFORMATION TO A HUMANTELEOPERATOR

The ability to sense and respond to frictional variations is important for dexterous manipulation. It has been demonstrated that humans appl y forces to an object on the basis of its anticipated frictional prope rties. After contact, tactile receptors provide information on the act ual frictional properties and ensure that the applied finger tip force s allow for a safety margin against slips during the ensuing manipulat ion. With inappropriate forces, incipient and overt slips occur which produce receptor discharges and elicit automatic adjustments of the fi nger tip forces to increase the safety margins against future slips. I t is demonstrated that it is possible to elicit rapid, nonhabituating and sustained grasp responses by means of a tactile display. Subjects grasped and lifted an instrumented test object using the thumb and ind ex finger. While the object was held in air, rapid but small sliding m ovements were invoked between the object and either contact plate and caused a load force redistribution. This reliably triggered a grasp fo rce increase similar to the ones elicited by natural slips occurring d uring normal manipulation. An important application of this finding is in relaying frictional information from a slave hand to a human opera tor. Furthermore, it may make it possible to reduce disparity between master and slave hands in force reflective telemanipulation systems.