Speech encryption based on synchronisation of chaotic Takagi-Sugeno systems using PI observer

This paper presents a synchronisation method of nonlinear chaotic systems using Takagi-Sugeno representation with unmeasurable premise variables. An extended PI observer with unknown input is designed to achieve the synchronisation objective. The proposed PI observer estimates both the states and the unknown input. The convergence of the PI observer is established in an LMI formulation framework. An application to speech encryption and decryption is performed to illustrate the efficiency of the proposed approach.