Nonlinear friction compensation of a 2-DOF planar parallel manipulator

The friction compensation method based on a nonlinear friction model is developed for a 2-DOF planar parallel manipulator. This nonlinear friction model enables reconstruction of viscous, Coulomb, and Stribeck friction effects of the parallel manipulator. Identification experiments are carried out, and parameters in the nonlinear friction model are estimated by nonlinear optimization. The dynamic control experiments are designed for the trajectory tracking of the parallel manipulator to study the friction compensation. The friction compensation performances are compared between the Coulomb + viscous friction model and the nonlinear friction model, also, the control performances without the friction compensation are given. Experiment results demonstrate that the tracking accuracy of the parallel manipulator can be improved obviously with the nonlinear friction compensation.