Detection and measurement of fingertip slip in multi-fingered precision manipulation with rolling contact

This paper describes a new method of detection and measurement of fingertip slip on the surface of a manipulated object in a multi-fingered precision manipulation with rolling contact. Due to the fact that slip sensors are still in a basic research phase and no slip sensor is compatible with the actual fingertip manipulation, our method is based on the multi-sensor fusion of vision, joint-encoders of the fingers, and fingertip force/torque sensors. Position of the contact between an object and the fingertip is computed in realtime from the measured pose of the object and the fingertip position. Tangential slip displacement of the fingertip contact is then separated from the displacement by rolling motion of the fingertip. Reliability of the slip detection from the noisy data is improved using the tangential-to-normal ratio of the measured force at the contact and the mutual relationship between the tangential force and the direction of the contact displacement.