Adaptive output feedback control of nonlinear systems with unmodeled dynamics and prescribed tracking performance

In this paper, adaptive output feedback dynamic surface control is developed for a class of nonlinear systems with unmodeled dynamics and prescribed tracking performance. Unmodeled dynamics is handled by introducing a novel description on Lyapunov function. Prescribed performance is satisfied through a transformation with respect to tracking error. With the help of Nussbaum function, the problem of the control gain sign not being known is solved in the controller design. In the theoretical analysis, by a constructed method, all the signals in the closed-loop system are proved to be semi-globally uniformly ultimately bounded, and transient tracking performance can also be preserved. A numerical example is provided to illustrate the effectiveness of the proposed approach.