Adaptive event-triggered output tracking for nonlinear systems with function control coefficients and unknown growth rate

This paper studies the problem of adaptive event-triggered practical tracking control by output feedback for a class of uncertain nonlinear systems with function control coefficients and unknown growth rate. Unlike previous studies, the control coefficients are known functions of the output, while the growth rate is an unknown polynomial function of the output. To address this issue, we construct an adaptive observer and two dynamic gains to re-construct the unmeasurable system states. One dynamic high-gain is increasing and could become large enough to compensate the extra nonlinearities from the function control coefficients, the other dynamic gain is designed to counteract the polynomial-function rate. Furthermore, to reduce the frequency of control signal transmissions, we incorporate an event-triggering mechanism based on a fixed threshold strategy. It is proved that the developed control scheme guarantees that all the closed-loop signals are globally bounded, the tracking error can be made arbitrarily small after a finite time and the Zeno-behavior is avoided. A simulation example is given to illustrate the effectiveness of the proposed scheme.