Master of Science, University of Akron, 2006, Mechanical Engineering

This thesis illustrates the application of a non-linear robust control to deal with friction variations in a hydraulic positioning system. The hydraulic system is modeled using analytical and experimental identification techniques considering both linear and nonlinear dynamics of the system. In the literature the friction is usually modeled as a function of velocity which has static, Coulomb and viscous friction components. However, there are several fascinating properties observed in systems with friction. This research is aimed at investigating the friction phenomenon and performing experiments on hydraulic positioning system to validate the identification of dynamic friction model (behavior in pre-sliding friction regime). The LuGre friction model which combines the pre-sliding behavior as well as the steady state characteristics is used to model and predict the friction for the controller design. A sliding mode controller is developed which has a feedback linearizing component plus additional terms that explicitly deal with system uncertainties due to friction and other unknowns. The sliding mode controller performed well during the experiments and simulations.

Committee: Celal Batur (Advisor) Subjects: