A Reduced Mass-Spring-Mass-Model of Compliant Robots Dedicated to the Evaluation of Impact Forces

Abstract The introduction of intrinsic compliance in the design of robots allows to reduce the risk for humans working in the vicinity of a robotic cell. Indeed, it permits to decouple the dynamic effects of the links’ inertia from those of the rotors’ inertia, thus reducing the maximum impact force in case of a collision. However, robot designers are lacking modeling tools to help simulate numerous collision scenarios, analyze the behavior of a compliant robot, and optimize its design. In this article, we introduce a method to reduce the dynamic model of a multi-link compliant robot to a simple translational mass-spring-mass system. Simulation results show that this reduced model allows to accurately predict the maximal impact force in case of a collision with a constrained human body part. Multiple impact scenarios are conducted on two case studies, a planar serial elastic robot and the R-Min robot, an underactuated parallel planar robot, designed for collaboration.