Simultaneous Sensing of Contact Force and Edge Orientation by Using Excitation From Fingernail

In order to record and remotely transmit dexterous operations carried out by human finger pad, tactile sensors that capture finger pad contact information play a critical role. However, when a sensing device covers the finger pad, the natural sense of touch is obstructed. We have addressed this problem by mounting an eccentric motor and an IMU sensor on a fingernail. By measuring the vibrations transmitted through the fingernail, estimation of finger contact information can be achieved, without covering the finger pad. Since the vibration of the finger induced by the eccentric motor changes when it contacts an object, it can be used to estimate contact details. This paper examines whether the proposed method can simultaneously estimate the contact force and the orientation of an object’s edge. Experimental findings indicated that the edge orientation could be estimated at 74.05% accuracy, while the contact force could be estimated at 59.29% accuracy, with especially high performance when using angular velocity data compared to other data sets. Moreover, increasing the contact force improved edge orientation accuracy, reaching nearly 90% at 300 g or more.