A New Multifunctional Tactile Sensor for Detection of Material Hardness

This paper proposes a new multifunctional tactile sensor for detection of material hardness. The proposed sensor is the semielliptic structure imitating the human finger and consists of several piezoelectric ceramic transducers arranged on the surface part and a parallel plate condenser on the upper side. Capacitance values are simultaneously measured by the front electrodes of piezoelectric ceramic transducers and the parallel plate condenser. They depend on material hardness, and their values exhibit different characteristics versus the hardness. Therefore, higher detection ability is provided from two types of capacitance values. In the experiment, three kinds of materials - aluminum, acrylic resin, and silicone rubbers with four grades of hardness - were prepared. The detection of hardness was demonstrated by two types of capacitance measurements: the front electrodes and the parallel plate condenser. The results indicated that the proposed tactile sensor was useful for detection of material hardness although there are some problems that must be clearly addressed.