Modeling and observer-based compensation of slip in a friction drive for servo positioning

This paper studies slip in friction drives in the context of a precision servo positioner equipped with a twist-roller friction drive. The servo positioner is modeled using a two-mass model that includes the experimentally-identified nonlinear slip dynamics of the friction drive. The model is then used to design an observer-based compensation scheme aimed at reducing the slip-induced performance degradation of the servo positioner's linear time invariant controller. The compensation scheme is validated in simulations and experiments using state feedback controllers. Tracking performance with the proposed slip compensation scheme, compared with the original controller and an intuitive high pass filter approach, is shown to improve considerably.