Coulomb friction effects on the dynamics of bearings and transmissions in precision robot mechanisms

General guidelines for analyzing friction at the joints are discussed. It is shown that friction can be related to the joint coordinates and their first and second time derivatives. The resulting extended robot dynamics formulation is investigated as it applies to the inverse and forward robot dynamics problems. The analytical dependency of Coulomb friction on joint interactions is explicitly examined. As an illustration of friction effects in transmissions, the friction in harmonic drives is considered and a method is developed for its evaluation. The quantitative characterization of several specific cases is provided. The study is significant for the design and control achieving of high-speed precision robot motion