SummaryThis paper investigates the problem of global practical tracking control via dynamic output‐feedback for a family of uncertain nonlinear systems with unknown output function. The nonlinear terms of the system under consideration are assumed to be bounded by an unknown parameter multiplied by a function of unmeasured states. Furthermore, contrary to the previous works, the system output is presented with a multiplicative unknown measurement noise. Based on a high‐gain observer to reconstruct the unmeasured system states and handle the unknown output function, an adaptive output feedback controller is designed to guarantee the reference trajectory tracking. The boundedness of all the closed‐loop signals is verified by Lyapunov analysis and the tracking errors are proved to be sufficiently small prescribed after a finite time. A practical example is given to illustrate the effectiveness of the proposed design scheme.

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UDC 517.9 This paper deals with the problem of stability of nonlinear differential equations with perturbations. Sufficient conditions for global uniform asymptotic stability in terms of Lyapunov-like functions and integral inequality are obtained. The asymptotic behavior is studied in the sense that the trajectories converge to a small ball centered at the origin. Furthermore, an illustrative example in the plane is given to verify the effectiveness of the theoretical results.