Recursive state-dependent scaling design of robust output feedback control for global stabilization

A state-dependent scaling approach to robust backstepping is proposed for global robust stabilization of nonlinear systems via output feedback. The design procedure handles output-feedback stabilization of strict-feedback systems with various kinds of uncertainty structures in a unified way. The backstepping is ready for numerical computation. The paper shows a condition of allowable uncertainty size under which an uncertain system is globally robustly stabilized by output feedback. A special class of systems is shown to be always globally stabilizable for arbitrarily large nonlinear size of uncertainties. The design procedure is developed by using the Schur complements instead of Young's inequality. A recursive procedure of robust observer design is proposed.