A Novel Observer Design for LuGre Friction Estimation and Control
Caner Odabaş, Ömer Morgül
TL;DR
The paper addresses friction-induced performance limitations in motion control by introducing a stand-alone LuGre friction observer that estimates the internal state $z$ and the friction force $F$ using velocity error. The method provides Lyapunov-based stability guarantees, achieving asymptotic (and under stronger design, exponential) convergence of estimation errors under mild input conditions. Through simulations with representative LuGre parameters, the observer demonstrates enhanced velocity and position tracking when integrated with friction compensation, and it is designed to be applicable with arbitrary controllers. Overall, the work offers a simple, controller-agnostic observer that enables effective LuGre-based friction compensation in mechanical systems.
Abstract
Dynamic components of the friction may directly impact the stability and performance of the motion control systems. The LuGre model is a prevalent friction model utilized to express this dynamic behavior. Since the LuGre model is very comprehensive, friction compensation based on it might be challenging. Inspired by this, we develop a novel observer to estimate and compensate for LuGre friction. Furthermore, we present a Lyapunov stability analysis to show that observer dynamics are asymptotically stable under certain conditions. Compared to its counterparts, the proposed observer constitutes a simple and standalone scheme that can be utilized with arbitrary control inputs in a straightforward way. As a primary difference, the presented observer estimates velocity and uses the velocity error to estimate friction in addition to control input. The extensive simulations revealed that the introduced observer enhances position and velocity tracking performance in the presence of friction.