Adaptive synchronization of hyperchaotic systems via passivity feedback control with time-varying gains

A passivity feedback control scheme with time-varying gains is proposed for adaptive synchronization of hyperchaotic systems. By transforming the synchronization error dynamics into an equivalent passive system, a synchronization control law with time-varying gains is achieved and the convergence of the synchronization errors is guaranteed. The feasibility and effectiveness of the proposed scheme is demonstrated through its application to hyperchaotic Lü systems.