Friction compensation via variable structure control: regulation and low-velocity tracking

In this paper a robust adaptive nonlinear controller based on variable structure control is utilized to significantly reduce the effect of friction in positioning applications. Although the controller is designed to utilize the properties of a good dynamic model, the compensator is robust to both parametric and dynamic uncertainties in the model. Furthermore, the control design does not attempt to directly estimate the various parameters in the friction model in order to effectively cancel the friction force predicted by the model. The controller through its direct adaptation manages to produce a counteracting force to practically eliminate the friction effects. To show the efficacy of our control design, a stochastic dynamic model of friction is utilized in our simulation studies. Finally, experimental results have been included.