Modeling of ContactMechanics and Friction Limit Surfaces for Soft Fingers in Robotics, with Experimental Results

摘要

A new theory in contact mechanics for modeling of soft fingers is pro- posed to define the relationship between the normal force and the radius of contact for soft fingers by considering general soft-finger materials, including linearly and nonlinearly elastic materials. The results show that the radius of contact is proportional to the normal force raised to the power ofγ, which ranges from 0 to 1/3. This new theory subsumes the Hertzian contact model for linear elastic ma- terials, where γ= 1/3. Experiments are conducted to validate the theory using artificial soft fingers made of various materials such as rubber and silicone. Results for human fingers are also compared. This theory provides a basis for numerically constructing friction limit surfaces. The numerical friction limit surface can be approxi- mated by an ellipse, with the major and minor axes as the maximum friction force and the maximum moment with respect to the normal axis of contaci, respectively. Combining the results of the contact- mechanics model with the contact-pressure distribution, the normal- ized friction limit surface can be derived for anthropomorphic soft fingers. The results of the contact-mechanics model and the pressure distribution for soft fingers facilitate the construction of numerical friction limit surfaces, and will enable us to analyze and simulate contact behaviors of grasping and manipulation in robotics.