Adaptive synchronization of chaotic systems based on speed gradient method and passification

A problem of synchronizing two nonlinear multidimensional systems with unknown parameters is considered. Two general procedures for adaptive synchronization law design based on speed-gradient method are proposed. Conditions ensuring the synchronization are given. The second procedure is based on passification of error system (making it passive by feedback). The results are illustrated by examples: synchronizing a pair of Chua's circuits and a pair of circuits with tunnel diodes. Computer simulation results confirming theoretical analysis are given.