Adaptive output feedback variable-structure control design for uncertain dynamic systems

In this paper, an adaptive feedback variable-structure control design scheme is presented for the systems with a linear time-invariant modelled part and nonlinear uncertain dynamics by using only input and output measurements. The main idea of this control strategy is the introduction of auxiliary signals and normalized signals with memory, and the combination of the variable-structure control with the adaptive control. Compared with the results obtained by Bondarev et al. (1985) and Emelyanov et al. (1992), our results show that the parameters of the linear modelled part can be unknown. The global stability of the closed-loop system is guaranteed and the output of the system can be bounded by an arbitrarily sufficiently small fixed value by appropriate design of control parameters. The states of the system can be regulated to a small neighbourhood of the system origin.