The goal of our study is the 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 has characteristics similar to those of a human finger with respect to the shape and sensing functions which enable incipient slip detection: the finger skin has ridges on the surface in 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 involves designing the characteristics of a FAI receptor, which has a transducer for which we chose PVDF film sheets, which have a dynamic stress rate characteristic. Design phase 2 involves determination of the shape and size of the artificial finger skin, and the location of the transducer is analyzed to find its best position. Design phase 3 involves manufacturing artificial finger skin. Experimental results show that incipient slip occurs at the surface of artificial finger skin and 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 of incipient slip of the ridge, but also a high frequency vibratory signal which indicates slip of the ridge. In order to judge automatically that incipient slip occurs, we use a multi-layered ANN (artificial neural network). Judging incipient slip using an ANN shows that the system is robust to noise and can detect incipient slip.
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