Nonlinear friction phenomena in direct-drive robotic arms: an experimental set-up for rapid modelling and control prototyping

Abstract

This paper considers the design and the experimental validation of digital control algorithms when both low and high velocity precision issues are important for the quality of the controlled equipment. At low velocities friction phenomena are dominant, while at high velocities the nonlinear coupled and configuration-dependent dynamics plays a major role. Since rapid control prototyping (RCP) requires "finely-tuned" models of the equipment under investigation, an accurate definition of the nonlinear friction model is of capital importance for assessing the qualification of the proposed algorithms. An experimental validation of the proposed models and control algorithms with friction compensation is presented and discussed for a two-arms planar manipulator with brushless directdrive actuators.