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Effectiveness in flight control is achieved by maintaining specified performance despite the presence of faults and reliability implies taking the necessary measures to correct the fault before it leads to substantial performance deterioration and instability. In order to achieve both effectiveness and reliability, in this paper, we propose a fault-tolerant control (FTC) approach that is able to simultaneously compensate for actuator faults, model mismatch and parameter variations in aircraft systems. The proposed control design successfully combines the properties of active and passive FTCs to accommodate faults while retaining acceptable system performance. A passive baseline controller is designed using sliding mode theory and an active controller is designed using a model reference adaptive approach. The proposed control paradigm retains system performance under fault free conditions and triggers corrective measures only when necessary, hence ensuring flight effectiveness and enhancing system's reliability. The proposed approach was validated using an aircraft system subject to a wide range of fault scenarios. Comparison analysis of the system performance, when only the passive controller is considered, was also carried out to highlight the effectiveness of the proposed approach. The obtained results show that the proposed fault-tolerant flight controller is able to maintain acceptable performance and retain system stability even in the event of major loss in actuator effectiveness.

This article proposes a fast reaching finite time synchronization approach for chaotic systems along with its application to medical image encryption. First, an adaptive terminal sliding mode tracking approach with fast reaching condition is designed to synchronize the chaotic systems at the transmitter and receiver ends in finite time. Then, a chaotic cryptosystem, using synchronized chaotic systems as secret keys generator, is proposed to enhance the security of medical image transmission and/or storage. The applicability and efficiency of the proposed synchronization approach is assessed using a simulation as well as an analytical study. The analysis encompassed security tools such as histogram analysis, correlation test, and information entropy change the rate of the number of pixels and unified average changing intensity. The obtained results confirmed the robustness and fast convergence rate of the proposed synchronization approach. The security analysis also shows that the proposed cryptosystem displays acceptable levels of resistance to various attacks. INDEX TERMSChaos synchronization; fast reaching condition; medical image encryption; MORE method encryption.

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