Observer-based approach for synchronization of a time-delayed, Chua's circuit

In this paper, we develop a reduced-order observer-based approach for synchronization of time-delayed chaotic systems. Indeed, in a recent work, Wang et al. proposed an interesting technique to enhance the complexity of the chaotic behavior of the standard Chua's circuit, through a time-delay feedback. We provide here a specific solution to ensure the synchronization of this class of nonlinear systems, even in the case of an unknown (or time-varying) delay. Our synchronization scheme relies on the design of a reduced-order observer, whose efficiency is tested on the numerical example provided in (X. Wang et al, IEEE Trans. Circuit Syst. 1, vol.48, no.9, p.1151-1156, 2001). This work is the first step in the design of a secure communications scheme.