Robust Control of Uncertain Nonlinear Systems by Output Feedback

The problem of global robust stabilization by output feedback is investigated, for a class of uncertain nonlinear systems that are dominated by both linear and higher-order nonlinearities multiplying by an output dependent growth rate. There are two ingredients in this paper. One is to exploit the idea of how to handle polynomial growth conditions via homogeneity and domination, without introducing an observer gain updated law. Another one is the development of a recursive design algorithm for the construction of reduced-order observers, which is not only interesting in its own right but also has a valid counterpart that turns out to be effective when dealing with strongly nonlinear systems, even lack of uniform observability and smooth stabilizability.