Incipient Slip Detection Method With Vision-Based Tactile Sensor Based on Distribution Force and Deformation

Slip detection, especially incipient slip, plays a very important role in achieving stable robot grasp, whereas the fine and reliable measurement of incipient slip has not been well addressed. In this paper, we propose a novel incipient slip detection method based on contact distribution force and deformation information using vision-based tactile sensor, which has the advantages of clear physical meaning, rich measurement information and high robustness. This paper firstly reveals the mechanism of slip generation from the perspective of force equilibrium, and gives a vector expression for slip calculation. Then a method is proposed to determine the stick-center region based on the analysis of distribution force. The relative rigid body motion between the sensor and the object can be further calculated using the deformation of the tactile sensor in this region. Finally, the incipient slip is obtained by subtracting the rigid body displacement from the deformation field. Based on the slip field information, this paper further proposes a criterion for determining the stick/slip region and evaluating the degree of incipient slippage. With the help of finite element method, a complex contact condition with both tangential force and torque between the sensor and the objects having different surface morphologies is constructed. The results demonstrate the accuracy and applicability of the proposed slip detection method. Furthermore, by developing a slip detection experimental setup, which captures the true slip field through an external camera for the first time, the validity of the proposed slip detection method is directly and quantitatively verified.