Two Globally Convergent Adaptive Speed Observers for Mechanical Systems

TL;DR

This paper introduces two new adaptive speed observers for mechanical systems that are globally convergent, robust against disturbances, and capable of estimating unknown friction coefficients, enhancing practical applicability.

Contribution

It presents an adaptive observer that is robust to disturbances and a new globally convergent observer that also estimates friction coefficients, extending previous work.

Findings

Observers are globally exponentially stable.

The methods effectively reject constant disturbances.

Friction coefficients can be accurately estimated.

Abstract

A globally exponentially stable speed observer for mechanical systems was recently reported in the literature, under the assumptions of known (or no) Coulomb friction and no disturbances. In this note we propose and adaptive version of this observer, which is robust vis--a--vis constant disturbances. Moreover, we propose a new globally convergent speed observer that, besides rejecting the disturbances, estimates some unknown friction coefficients for a class of mechanical systems that contains several practical examples.