A study of response to short torque pulses and fuzzy control of positioning for devices with stick-slip friction

The paper describes a novel approach to very accurate positioning control of mechanical devices with nonlinear (stick-slip) friction. The controller applies narrow torque pulses to achieve the desired displacement of the mechanism. The pulse shapes are computed through fuzzy logic approximation of the dependence between the desired displacement and the pulse shape. A detailed experimental study of the system response to the rectangular torque pulses and a detailed controller design are presented for a direct-drive manipulator setup. It is experimentally demonstrated that the developed controller achieves positioning precision up to the limits of the position encoder resolution.