Global output feedback tracking controller based on hybrid estimation for a class of uncertain nonlinear systems

A global output-feedback tracking controller based on a hybrid estimation scheme is proposed for a class of uncertain nonlinear systems. The hybrid estimation scheme combines a general estimator, that provides an input-to-state practical stabilizing control law with a locally exact differentiator, based on higher-order sliding modes. The key idea is to design a switching law to select between both estimators in such a way that stability properties are preserved and in addition exact tracking is achieved. As an example, the proposed control scheme is shown to solve the global output feedback tracking control problem of a class of uncertain Euler-Lagrange systems.