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

In this paper, adaptive output feedback tracking control is studied for a class of nonlinear systems with input unmodeled dynamics and prescribed performance based on dynamics surface control method. Prescribed performance tracking control is implemented by introducing a transformation with respect to tracking error. A normalization signal is used to restrict the nonlinear input unmodeled dynamics. Assisted to Nussbaum function, the control gain sign does not need to be known in the controller design. By the theoretical analysis, all the signals in the closed-loop system are proved to be semi-globally uniformly ultimately bounded, and the steady-state and transient tracking performance can be ensured. A numerical example is provided to illustrate the effectiveness of the proposed approach.