Adaptive Output Feedback Control for Uncertain Nonlinear Systems with Unknown Modeling Errors

It is well known that unknown modeling errors cannot be avoided in practice. Such unmeasured uncertainties are usually denoted as unknown nonlinear functions that exist in every channel of the system equation. This paper aims to develop an output feedback adaptive control scheme by constructing state estimation filters to address such unknown modeling errors. In the controller design, these uncertainties caused by modeling errors will be accumulated to the last step for compensation. Unknown parameters existing in the upper bound functions of unknown nonlinear functions and system parameters are estimated synchronously based on tuning function approaches. It is shown that the designed output feedback controller can ensure the stability and tracking performance of the closed-loop system, and the transient performance in terms of a truncated norm is also established. An adaptive output feedback controller has been proposed for uncertain nonlinear systems with unknown modeling errors. Unlike existing results, the model error considered here may exist in each state equation of the system and is bounded by a function with an unknown parameter. The stability of the controlled systems can be guaranteed by the proposed controller.image