Global output-feedback stabilization for high-order nonlinear systems with unknown control coefficients

Abstract

This paper is concerned with the global stabilization via time-varying outputfeedback for a class of high-order uncertain nonlinear systems. The remarkable feature of the systems, that is, the unknown time-varying control coefficients and the unmeasured states dependent growth with unknown time-varying rate, makes the existing control design methods unapplicable. By skillfully combining time-varying approach and certainty equivalence principle, a time-varying output-feedback control design scheme is proposed in the paper. It is worth mentioning that the serious unknowns and time-variations in the systems are compensated by introducing time-varying design functions, rather than employing adaptive approach. With the appropriate choices of the design functions, all the states of the closed-loop system are globally bounded and converge to zero.