A new criterion for redundancy resolution of human arm in reaching tasks

This paper proposes a new criterion for redundancy resolution of human arm in reaching tasks. First, an assumption of minimum Total Potential Energy (TPE) principle is proposed to explain how human exploit the kinematic redundancy of their arms to choose the natural arm postures in reaching tasks. This is the basis as well as the physical meaning of the new criterion. The TPE of human arm includes Gravitational Potential Energy (GPE) and Elastic Potential Energy (EPE) stored in the muscles. Then, a creative simple equivalent model, a virtual torsion spring model with variable stiffness, is proposed to represent the EPE. The stiffness of the torsion spring is related to the target point. Last, to obtain the stiffness of the torsion spring in different target points, many experiments are performed, and multiple linear regression analysis is introduced to determine the relation between the stiffness and target point.