Global adaptive output-feedback control of nonlinear systems

The authors address the problem of designing global adaptive controls for a class of single-input-single-output nonlinear systems which are linear with respect to the input and to an unknown constant parameter vector. They determine via geometric conditions a class of systems which can be globally controlled by a dynamic (adaptive), observer-based, output-feedback compensator. In suitable coordinates each system admits observers with linear error dynamics and has linear asymptotically stable zero dynamics: the feedback linearizability property is not required. When the parameters are shown, new sufficient conditions for global output-feedback control of nonlinear systems are obtained as a special case. The class of systems determined strictly contains the class of linear minimum phase ones with unknown poles and zeros, known sign of high frequency gain, and known relative degree