Dynamic Simulation of Modular Robot Joint with Friction and Flexibility

Abstract

Nonlinear factors such as friction, flexibility, hysteresis and kinematic error is introduced due to harmonic drives are used as transmission system in modular joints, which affect performance of robotic joint. Hence characterization and control of these nonlinear attributes is important to improve the precision. Nonlinear attributes including friction and flexibility in robotic joint is mainly studied in this paper. The modular joint is divided into high-speed and low-speed side respectively based on the joint characteristics. An accurate and practical mixed friction model based on the static, Coulomb and Stribeck friction are built for the complex friction characteristics in the high-speed and low-speed side, velocity is used as the switching condition of the mixed friction model. Flexibility model is established by the linear spring model. The joint dynamic model is realized and simulated by Simulink to validate the dynamic model. The results showed that the Mixed friction model can better reflect the various friction phenomenon in the joint compared with the traditional friction model.