Instantaneous evaluation of friction based on ARTC tactile sensor

A human can lift up an object with almost minimal grasping force regardless of the friction coefficient between the fingers and the object, but the sensing mechanism for this remarkable task has not been well explained yet. We propose a tactile sensor to detect a friction coefficient at the moment of touch. With this sensor output we evaluate the largest lifting-force just before a slip happens, without any preliminary motions. The sensor has a sensing cell in the elastic body, which measures strain/stress components parallel and vertical to the surface. Those plural stress/strain parameters at a point gives the friction coefficient. A prototype sensor is fabricated with acoustic resonant tensor cell, and we examine its principles in experiments