Initial Slip Detection and Its Application in Biomimetic Robotic Hands

The detection of initial slip is very important for biomimetic robotic hands to adjust the grasping force in time and achieve a stable grasp when environmental disturbances are exerted on the grasped objects and the grasping force is insufficient. An initial slip detection method is proposed in this paper. First, a dynamical model of initial slip is built based on the theory of friction-induced vibration at near-zero slip velocity. Then, the responses for typical disturbances are derived analytically. Theoretical analyses show that the grasping force is oscillating and discontinuous when a disturbance is exerted on the grasped object, resulting in slip at near-zero velocity. Finally, the high-frequency component of the grasping force signals, which corresponds to the time of initial slip, is extracted by wavelet transform, and the sudden change of wavelet coefficients can be used to detect the onset of slip in time. The experimental results demonstrate that the proposed slip detection method is effective and feasible for improving the grasping stability of biomimetic robotic hands.