Friction Compensation by the use of Friction Observer

Sammanfattning: The deteriorating effects of friction on the control of mechanical systems is a major problem in a multitude of applications such as high-performance robotics and pointing systems. This thesis aims at improving control by using a nonlinear friction observer to detect friction in the system and use this information to modify the control input. After some initial attempts with the LuGre friction model, the observer was decided to be based on the Dahl model of friction. Simulations and experiments were made using the unstable Furuta pendulum and the efficiency of the observer aproach was compared to other standard methods for friction compensation. Although being able to serve its purpose very well in the simulated environment the observer friction compensation could not outperform the other compensation methods in the experiments, only being capable of slightly improving the control of the pendulum. The cause of this lack of success is still unclear.