Position control on nanometer scale based on an adaptive friction compensation scheme

This work concerns a non-model-based friction compensation scheme for dynamic position control on nanometer scale. The main goal of this work is to build up and implement a simple dynamic friction observer which allows an estimation of the friction force in combination with the system inertia against displacement. Experiments in the pre-sliding and sliding friction regimes are conducted on an experimental setup. After a short review of friction compensation, the experimental setup is explained in detail. Next, the observer is modeled mathematically and the used control scheme is presented. Finally, the friction observer is utilized as a non-model-based friction estimator combined with a classical feedback controller to compensate the nonlinear friction force and reduce tracking errors significantly. It is shown that the proposed controlling approach is able to realize a fast and ultra precise positioning over long distances.