A PHYSIOLOGICAL METHOD FOR RELAYING FRICTIONAL INFORMATION TO A HUMAN TELEOPERATOR

The ability to sense and respond to frictional variations is important for dexterous manipulation. It has been demonstrated that humans apply forces to an object on the basis of its anticipated frictional properties. After contact, tactile receptors provide information on the actual frictional properties and ensure that the applied finger tip forces allow for a safety margin against slips during the ensuing manipulation. With inappropriate forces, incipient and overt slips occur which produce receptor discharges and elicit automatic adjustments of the finger tip forces to increase the safety margins against future slips. It 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 index finger. While the object was held in air, rapid but small sliding movements were invoked between the object and either contact plate and caused a load force redistribution. This reliably triggered a grasp force increase similar to the ones elicited by natural slips occurring during normal manipulation. An important application of this finding is in relaying frictional information from a slave hand to a human operator. Furthermore, it may make it possible to reduce disparity between master and slave hands in force reflective telemanipulation systems.