A Slip Sensor with Surface Ridges Which is Mounted on a Robot Hand Generates High-Frequency Signals for Isolating Slip Phases

Abstract

This paper deals with a slip sensor that has ridges on the sensor surface and is capable of isolating a slip phase from other contact states between an object and the sensor surface, which has not been verified by using conventional slip sensors. The proposed structure of the sensor enables it to detect high-frequency slip vibration with vertically molded strip-shaped ridges of the sensor, in each of which a piece of PVDF film is fixed. We were convinced through wavelet analysis that the vibration corresponded to a free vibration mode of the strip-shaped ridges and that the vibration did not depend upon the surface condition. We showed that the slip sensor generated a slip signal which was characterized by distinction of only slip phases from other contact, release, or roll phases. Especially, the last two phases could be discriminated by the characteristic waveform of release-phase overshoot. The sensor output signal was also shown to be very different from the noise signal which originated in the vibration caused by driving a motor of the experimental setup. Finally, we demonstrated that a two-fingered planar robot hand successfully arrested a slipped-off notebook using the distinctive slip information acquired from the sensor after the necessity of detecting not an incipient but a total slip phase.