Global stabilization via output-feedback for high-order uncertain nonlinear systems

This paper is devoted to the global stabilization via output-feedback for a class of high-order uncertain time-varying nonlinear systems. Mainly due to the time-varying control coefficients and the unknown time-varying growth, the problem has not yet been solved. By introducing time-varying transformation and observer, and skillfully employing adding a power integrator, time-varying technique and certainty equivalence principle, a time-varying output-feedback control design scheme is developed. It is shown that, with the appropriate choice of the design functions, all the signals of the closed-loop system are globally bounded, and furthermore converge to zero. It is worth mentioning that, in this paper, the serious system unknowns are effectively tackled by time-varying technique, rather than by adaptive technique as in most existing literature.