Experimental Investigation of Human Soft Tissue Behavior for Constructing Human-Robot Contact Force-Displacement Measuring System

Abstract

Lack of knowledge in the human soft tissue deformation during contact between humans and robots is an important obstacle to the development of a standard safety testing device in human-robot interaction (HRI). Human dummies and commercial devices are used to test safety criteria during contact in HRI. However, the responses of these dummies still do not correctly reflect the soft tissue deformation for different human body parts. In this study, we investigate the net behavior of the human upper arm soft tissue deformation during constrained impacts. The net behavior included the soft tissue deformation when is directly and indirectly subjected to impact forces. Using a pendulum device, dynamic and quasi-static (Q.S) impacts were applied to human upper arms, and the differences between soft tissue deformation at the impact location and at the opposite side of the impact for two impactor shapes were measured. Impact force-displacement curves showed a nonlinear behavior for dynamic and Q.S impacts, with greater nonlinearity during dynamic than during Q.S impacts. Our results also demonstrated that soft tissue deformation at the impact location is lower than that at the opposite side of the impact. We also found that the radius of the impactor shape affects the upper arm soft tissue deformation, demonstrating that a larger radius impactor led to a greater soft tissue deformation than a smaller radius impactor. These findings are important for developing testing devices for HRI.