Development of artificial finger skin to detect incipient slip for realization of static friction sensation

The goal of our study is realization of static friction sensation using a piece of artificial finger skin for robot hand manipulation. In order to realize the sensation, we recall the importance of incipient slip detection. First, artificial finger skin is designed which is mimicked to have characteristics similar to that of a human finger with respect to the shape and a part of the sensing functions which such enable the incipient slip detection: The finger skin has ridges on the surface in each of which a pair of artificial FAI receptors are embedded. The design process of artificial finger skin is also shown that includes three phases. Design phase #1 is to design the characteristics of a FAI receptor as the transducer of which, we choose PVDF film sheets which have a dynamic stress rate characteristic. Design phase #2 involves determination of the shape and size of artificial finger skin, and the location of the transducers in a ridge. We analyze the stress in the finger skin when incipient slip occurs at the surface. The signal from transducer is analyzed what the best situation of the position of transducer and the using information of transducer at the future process. Design phase #3 is to manufacture artificial finger skin. Experimental result that incipient slip occurs at the surface of artificial finger skin reveal that the differential output voltage signal from a pair of artificial FAI receptors embedded in a ridge captures not only low-frequency vibration to generate a predictive signal which warns incipient slip of the ridge, hut also high frequency vibratory signal which indicates slip of the ridge. In order to judge automatically that incipient slip occurs we use multi-layered ANN. The result to judge incipient slip use ANN shows that the system is robust to noise and can detect the incipient slip.