Adaptive Dual High-Gain Output Feedback Global in Unknown Parameters for a Class of Nonlinear Systems

In a recent result, we proposed a dynamic dual high-gain observer/controller architecture for nonlinear systems of the generalized output-feedback canonical form. The designed output-feedback controller was shown to be robust to functional and parametric uncertainties coupled with all states. However, a magnitude bound on the unknown parameters was required. In this paper, we propose two output-feedback controllers, one time-varying and the other time-invariant that can handle time-varying nonlinear parametric uncertainty coupled with all states without requiring any a priori magnitude bounds on the unknown parameters. The proposed dynamic controller designs provide globally asymptotically stabilizing output-feedback solutions for the benchmark open problem proposed in our earlier work with no magnitude bounds or sign information on the unknown parameter being necessary.