http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/130 Thu, 01 Oct 2026 07:01:13 GMT 2026-10-01T07:01:13Z http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/14860 L1 Adaptive Control for Fractional-Order Systems Boulham, Ihab Abderraouf; Boubakir, Ahsene (Encadreur) Fractional-order calculus has attracted the attention of scholars in the areas of control and system analysis.However, despite its notable advantages, ℒ1 adaptive control technique remains unexplored in this field.This thesis introduces an extension of this technique to fractional-order systems. Firstly, a new fractional-order ℒ1 adaptive controller is proposed for a class of fractional-order systems with matched uncertaintiesand external disturbances. Then, the controller is generalized to the case of multiple-input multiple-outputincommensurate systems. The extension of the methodology is possible thanks to the use of a fractional-order sliding surface, simplifying the control architecture and facilitating stability analysis. In the pursuitof enhancing the developed controller, neural networks are employed to handle time-varying input gainand unmodeled dynamics. Additionally, fuzzy logic systems are implemented to tackle various sources ofuncertainty within the system. These include unknown input nonlinearities, unmodeled system dynamics,and external disturbances. The analysis of the obtained theoretical and simulation results confirms thatthe developed strategies guarantee closed-loop stability maintaining the key features of the ℒ1adaptivecontroller. Wed, 03 Jul 2024 00:00:00 GMT http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/14860 2024-07-03T00:00:00Z http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/14509 Contribution to the control of photovoltaic systems Boubekri, Noureddine; Doubou, Sofiane (Encadreur) Solar photovoltaic energy is a clean, sustainable and inexhaustible source of electrical energy production, making it a promising alternative to fossil fuels in energy transition and avoiding environmental damage resulting from the combustion of fossil fuels. However, the PV energy production systems remains to this day uncompetitive due to the high cost of solar cells and low conversion efficiency. To increase the efficiency of PV systems, MPPT control algorithms are developed to ensure the full exploitation of available solar energy. This thesis proposes two new MPPT control approaches to improve the efficiency of energy transfer in a standalone PV system: Design of a robust MPPT controller based on T-S fuzzy model approach with H_2⁄H_∞ performance and taking into account the problem of actuator saturation. Development of a saturate robust MPPT controller based on polynomial SOF control approach, which enables for system cost reduction by reducing the number of sensors required. The effectiveness of the proposed MPPT control system was verified under different climatic conditions, through Matlab/Simulink simulations and numerical comparisons to many different approaches. The obtained results were satisfactory, and confirmed that the proposed controllers provide high performance, allowing full exploitation of the solar energy. Mon, 01 Jan 2024 00:00:00 GMT http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/14509 2024-01-01T00:00:00Z http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11358 Contribution to chaotic and fractional data cryptography Bouridah, Mohamed salah; Bouden, Toufik (encadreur) With the rapid development of network technology and multimedia, digital information can be transported in different form conveniently. People can exchange information and trade online easily. The internet does not just bring convenience to people's lives but also involves risks. Some sensitive information can be stolen and even distributed illegally. It is linked to political, diplomatic and military life, economic, social and commercial security. Since chaos has good cryptography properties such as randomness, aperiodicity, extremely sensitive to initial conditions and parameters, forcing the robustness of data cryptography. This thesis revolves around two main objectives. The first is to design chaotic and fractional order synchronization systems. The development of new chaos based cryptography and transmission schemes is the second objective of this thesis. Thu, 17 Mar 2022 00:00:00 GMT http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11358 2022-03-17T00:00:00Z http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11307 Contribution to the conception of chaotic systems for secure data transmission Benkouider, Khaled; Bouden, Toufik (encadreur) Since the main characteristics of chaos, such as sensitivity to initial conditions, randomness, unpredictability and complexity can be attached with the well-known confusion and diffusion properties of cryptography, there has been tremendous interest world-wide in the possibility of using chaos in communication systems. Therefore, it is of significant interest to design suitable chaotic systems for secure, cost-effective and robust communications. The first contribution of this thesis is to design a new chaotic system with high complexity and large bandwidth compared with the existing chaotic systems. The second contribution is to develop a new n-dimensional multistable hyperchaotic system with (n>7) and multiple coexisting attractors. The third contribution is to construct new n-dimensional hyperchaotic systems with (n>7) and (n-2) positive Lyapunov exponents. The last contribution is to construct a new delayed discrete-time hyperchaotic system and propose a new approach for delay estimation and information recovery for delayed discrete-time chaos-based secure communication. Thu, 15 Jul 2021 00:00:00 GMT http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11307 2021-07-15T00:00:00Z