Results presented in this paper have been obtained through experimentation on a pneumatic actuator used for VGT system. Considering the effects of aerodynamic force an adaptive Lu-Gre model is presented. The Hunting effect caused by friction stick-slip and controller integral action, have been explained and illustrated with simulation results. Friction compensation has been suggested to counter the Hunting effect. Two friction
compensation techniques have been proposed. In simulation and experimentations, both methods have provided good results. The use of a Knocker has been found to be more simple than compensation through observer. But continuous switching input required for the knocker results in extra energy consumption, as compared to the state observer. Moreover, compensation technique with observer is more robust than knocker. Experiments to verify the robustness of the controller will be performed on the test bench by inducing the external forces
(e.g. aerodynamic force ) into the system.