An Optimal Homogenous Stability-Based Disturbance Observer and Sliding Mode Control for Secure Communication System

To prevent the loss of data or distortion of the real sent data in the secure communication, the disturbance and uncertainty rejection is very important technique. Especially, the secure communication of the chaotic system, where the master and slave systems are used to encrypt and decrypt the signal. These systems are should be a chaotic. The chaotic system is unpredictable and unstable. The security is obtained if the master and slave systems are synchronizing. Therefore, this paper proposes a new disturbance observer (DO) for estimating attacked signals on public channels and uncertain values of the secure communication system (SCS). First, a new condition of the reaching law was proposed via a homogenous stability condition, which was used to construct the disturbance observer and synchronization controller. Second, the proposed stability is applied to design a new DO for estimating the attacked signals on the public channels and the variations of the parameters of all master and slave systems (MSSs). Third, the MSSs were synchronized by the sliding mode control (SMC) with the same reaching law with the proposed DO. The calculations of controller and observer designs were based on the Takagi-Sugeno fuzzy (TSF) system, where the MSSs were taken into account as the fuzzy system. However, the TSF was used for calculation only. The original chaotic of MSSs were used to keep the characteristics of the chaos phenomenon. Final, the mathematically proven was provided to show the corrections of the proposed methods. To show the superior powers of the proposed method, the simulation of MATLAB software and experiment of local network via the internet router were used to conduct the logical analysis. The tested disturbances and uncertainties were mostly compensated by the proposed DO.