Coulomb friction joint and drive effects in robot mechanisms

Robot design and evaluation requires an extensive analysis of the nature and the quantitative interrelations of the dynamic factors that govern the operation of a manipulator. Coulomb friction is an inherent phenomenon in devices with moving parts. In multi-degree of freedom mechanical devices, Coulomb friction causes highly nonlinear coupling of the corresponding differential equations of motion. Furthermore, the presence of Coulomb friction is responsible for motion inaccuracies. This paper addresses the fundamental issues associated with Coulomb friction and investigates their consequences on design and performance considerations. Moreover, it develops the reasoning that permits the incorporation of Coulomb friction into the study of the dynamic response of a robot. Within this framework, a recursive approach that reveals the motion progress of a manipulator may be developed for digital simulation-oriented applications, implementation of the properties and principles discussed therein, may help uncover critical aspects of a manipulator´s functionality and suggest ways for design improvements.