Bare finger tactile sensing for edge orientation and contact position using excitation from fingernail

In recording and reproducing skills involving the fingertips, a sensor that measures tactile information of fingertips is important. However, when the sensor covers the finger pad, the inherent sense of touch is compromised. We introduce a new tactile sensor, a pair of a vibration motor and a 6 degrees-of-freedom sensor attached to a fingernail that enables tactile sensing without covering the fingertip. This sensor estimates finger contact information by measuring vibrations caused by an eccentric motor positioned on the fingernail. The time series of the acquired angular velocity and acceleration data were utilized to identify the edge orientation and the contact position of the touching object. The results of the conducted experiments indicated that this setup can simultaneously identify both the edge orientation and the contact position with an accuracy of 71.67%. Potential applications include remote tactile transmission, integration with a robotic finger, and the detection of grasping postures in real objects.