2025 Volume 20 Issue 1 Pages 24-00052
This study proposes a motion analysis method for human-machine systems involving contact phenomena. When human skin comes into surface contact with objects, the flexibility of the skin and the friction between the epidermis and the object can result in different state distributions on the skin surface, such as stick/slip and contact/floating. We introduce a discretized model for motion analysis to express the state distributions and internal deformations. In the proposed method, contact phenomena, including friction, are formulated as a mathematical problem called the linear complementarity problem (LCP), and the flexibility of the skin is modeled using a mass-spring-damper model. We propose a hybrid integration method (Moreau’s midpoint method for epidermis motion analysis and the Runge-Kutta method for subcutaneous tissue motion analysis) to simultaneously address non-smooth phenomena such as friction and large deformations. In this method, the motion of the epidermis and subcutaneous tissue affect each other via virtual springs and dampers. As a preliminary investigation, real motion measurements are conducted for a fingertip sliding on a plane surface to verify the phenomena occurring on the skin. Subsequently, the analysis using the proposed method revealed trends similar to those observed in the motion measurements, demonstrating the effectiveness of the proposed method for analyzing the motion of skin in contact with objects.
