An adaptive speed observers’ design for a class of nonlinear mechanical systems

Abstract

An adaptive speed observer for mechanical systems, which are linear in the velocity (momenta) after a change of coordinates (Venkatraman et al. [2010]), was recently reported in the literature (Romero and Ortega [2015]). The velocity observer considers input disturbances and some unknown friction parameters in the design. In this note, we relax some assumptions imposed in that work so that, the class of systems is enlarged and quadratic terms in the velocity(momenta) and all the friction parameters are included in the design of the velocity observer. Simulation results using the robotic–leg system illustrate the performance of the proposed adaptive observer.