UNKNOWN INPUT OBSERVERS FOR MESSAGE-EMBEDDED CHAOS SYNCHRONIZATION OF DISCRETE-TIME SYSTEMS

Abstract

This paper is concerned with chaos synchronization of discrete-time systems for communication purposes. The information to be masked is embedded in the chaotic dynamics of the transmitter and acts as an external input. It cannot be transmitted to the receiver for the sake of security. Hence, the receiver system must be designed such that the information can be unmasked, given the only available output data consisting of a function of the state vector. This problem is solved with an Unknown Input Observers based approach which achieves an Input Independent Global Synchronization. The conditions of existence of such kind of observers along with the systematic procedure to design the gains of the observers are based on the notion of polyquadratic stability and expressed in terms of Linear Matrix Inequalities.