Optimized state feedback regulation of 3DOF helicopter system via extremum seeking

In this paper, an optimized state feedback regulation of a 3 degree of freedom (DOF) helicopter is designed via extremum seeking (ES) technique. Multi-parameter ES is applied to optimize the tracking performance via tuning State Vector Feedback with Integration of the Control Error (SVFBICE). Discrete multivariable version of ES is developed to minimize a cost function that measures the performance of the controller. The cost function is a function of the error between the actual and desired axis positions. The controller parameters are updated online as the optimization takes place. This method significantly decreases the time in obtaining optimal controller parameters. Simulations were conducted for the online optimization under both fixed and varying operating conditions. The results demonstrate the usefulness of using ES for preserving the maximum attainable performance

Flexible structure control laboratory development and technology demonstration

An experimental structure is described which was constructed to demonstrate and validate recent emerging technologies in the active control and identification of large flexible space structures. The configuration consists of a large, 20 foot diameter antenna-like flexible structure in the horizontal plane with a gimballed central hub, a flexible feed-boom assembly hanging from the hub, and 12 flexible ribs radiating outward. Fourteen electrodynamic force actuators mounted to the hub and to the individual ribs provide the means to excite the structure and exert control forces. Thirty permanently mounted sensors, including optical encoders and analog induction devices provide measurements of structural response at widely distributed points. An experimental remote optical sensor provides sixteen additional sensing channels. A computer samples the sensors, computes the control updates and sends commands to the actuators in real time, while simultaneously displaying selected outputs on a graphics terminal and saving them in memory. Several control experiments were conducted thus far and are documented. These include implementation of distributed parameter system control, model reference adaptive control, and static shape control. These experiments have demonstrated the successful implementation of state-of-the-art control approaches using actual hardware

Digital Communication System with High Security and High Immunity

Today, security issues are increased due to huge data transmissions over communication media such as mobile phones, TV cables, online games, Wi-Fi and satellite transmission etc. for uses such as medical, military or entertainment. This creates a challenge for government and commercial companies to keep these data transmissions secure. Traditional secure ciphers, either block ciphers such as Advanced Encryption Standard (AES) or stream ciphers, are not fast or completely secure. However, the unique properties of a chaotic system, such as structure complexity, deterministic dynamics, random output response and extreme sensitivity to the initial condition, make it motivating for researchers in the field of communication system security. These properties establish an increased relationship between chaos and cryptography that create strong and fast cipher compared to conventional algorithms, which are weak and slow ciphers. Additionally, chaotic synchronisation has sparked many studies on the application of chaos in communication security, for example, the chaotic synchronisation between two different systems in which the transmitter (master system) is driving the receiver (slave system) by its output signal. For this reason, it is essential to design a secure communication system for data transmission in noisy environments that robust to different types of attacks (such as a brute force attack). In this thesis, a digital communication system with high immunity and security, based on a Lorenz stream cipher chaotic signal, has been perfectly applied. A new cryptosystem approach based on Lorenz chaotic systems was designed for secure data transmission. The system uses a stream cipher, in which the encryption key varies continuously in a chaotic manner. Furthermore, one or more of the parameters of the Lorenz generator is controlled by an auxiliary chaotic generator for increased security. In this thesis, the two Lorenz chaotic systems are called the Main Lorenz Generator and the Auxiliary Lorenz Generator. The system was designed using the SIMULINK tool. The system performance in the presence of noise was tested, and the simulation results are provided. Then, the clock-recovery technique is presented, with real-time results of the clock recovery. The receiver demonstrated its ability to recover and lock the clock successfully. Furthermore, the technique for synchronisation between two separate FPGA boards (transmitter and receiver) is detailed, in which the master system transmits specific data to trigger a slave system in order to run synchronously. The real-time results are provided, which show the achieved synchronisation. The receiver was able to recover user data without error, and the real-time results are listed. The randomness test (NIST) results of the Lorenz chaotic signals are also given. Finally, the security analysis determined the system to have a high degree of security compared to other communication systems

Digital Communication System with High Security and High Immunity

Today, security issues are increased due to huge data transmissions over communication media such as mobile phones, TV cables, online games, Wi-Fi and satellite transmission etc. for uses such as medical, military or entertainment. This creates a challenge for government and commercial companies to keep these data transmissions secure. Traditional secure ciphers, either block ciphers such as Advanced Encryption Standard (AES) or stream ciphers, are not fast or completely secure. However, the unique properties of a chaotic system, such as structure complexity, deterministic dynamics, random output response and extreme sensitivity to the initial condition, make it motivating for researchers in the field of communication system security. These properties establish an increased relationship between chaos and cryptography that create strong and fast cipher compared to conventional algorithms, which are weak and slow ciphers. Additionally, chaotic synchronisation has sparked many studies on the application of chaos in communication security, for example, the chaotic synchronisation between two different systems in which the transmitter (master system) is driving the receiver (slave system) by its output signal. For this reason, it is essential to design a secure communication system for data transmission in noisy environments that robust to different types of attacks (such as a brute force attack). In this thesis, a digital communication system with high immunity and security, based on a Lorenz stream cipher chaotic signal, has been perfectly applied. A new cryptosystem approach based on Lorenz chaotic systems was designed for secure data transmission. The system uses a stream cipher, in which the encryption key varies continuously in a chaotic manner. Furthermore, one or more of the parameters of the Lorenz generator is controlled by an auxiliary chaotic generator for increased security. In this thesis, the two Lorenz chaotic systems are called the Main Lorenz Generator and the Auxiliary Lorenz Generator. The system was designed using the SIMULINK tool. The system performance in the presence of noise was tested, and the simulation results are provided. Then, the clock-recovery technique is presented, with real-time results of the clock recovery. The receiver demonstrated its ability to recover and lock the clock successfully. Furthermore, the technique for synchronisation between two separate FPGA boards (transmitter and receiver) is detailed, in which the master system transmits specific data to trigger a slave system in order to run synchronously. The real-time results are provided, which show the achieved synchronisation. The receiver was able to recover user data without error, and the real-time results are listed. The randomness test (NIST) results of the Lorenz chaotic signals are also given. Finally, the security analysis determined the system to have a high degree of security compared to other communication systems

Commande non-linéaire et analyse de stabilité de réseaux multi-terminaux haute tension à courant continu

This dissertation was devoted to the study of multi-terminal high voltage direct current (MTDC) networks. The main contributions were in the field of nonlinear automatic control, applied to power systems, power electronics and renewable energy sources. The research work was started with the intention of filling some gaps between the theory and the practice, in particular: 1) to investigate various control approaches for the purpose of improving the performance of MTDC systems; 2) to establish connections between existing empirical control design and theoretical analysis; 3) to improve the understanding of the multi-time-scale behavior of MTDC systems characterized by the presence of slow and fast transients in response to external disturbances. As a consequence, this thesis work can be put into three areas, namely nonlinear control design of MTDC systems, analysis of MTDC system's dynamic behaviors and application of MTDC systems for frequency control of AC systems.Cette thèse a été consacrée à l'étude des réseaux multi-terminaux haute tension à courant continu (MTDC). Les principales contributions étaient dans le domaine du contrôle automatique non linéaire, appliquées aux systèmes électriques, électronique de puissance et les sources d'énergie renouvelables. Le travail de recherche a été lancé avec l'intention de combler certaines lacunes entre la théorie et la pratique, en particulier: 1) d'enquêter sur diverses approches de contrôle pour le but d'améliorer la performance des systèmes MTDC; 2) d'établir des connexions entre la conception du contrôle empiriques existantes et analyse théorique; 3) d'améliorer la compréhension du comportement multi-échelle de temps des systèmes MTDC caractérisés par la présence de transitoires lents et rapides en réponse aux perturbations externes. En conséquence, ce travail de thèse peut être mis en trois domaines, à savoir la conception non linéaire de commande de systèmes MTDC, analyse des comportements dynamiques de système MTDC et l'application de systèmes MTDC pour le contrôle de fréquence des systèmes de climatisation

Synchronisation des systèmes chaotiques par observateurs et applications à la transmission d'informations.

Dans ce travail de thèse, nous développons des méthodes de synchronisation des systèmes chaotiques pour les applications de transmission d'informations. La première méthode de synchronisation que nous proposons est basée sur les observateurs adaptatifs à entrées inconnues pour une classe des systèmes chaotiques présentant des incertitudes paramétriques et des perturbations dans leurs dynamiques et du bruit dans les signaux de sortie (bruit dans le canal de communication). La méthode développée repose sur les techniques adaptatives pour la compensation des non-linéarités et des incertitudes paramétriques et pour la restauration des messages transmis. Elle se base également sur les méthodes de synthèse d'observateurs à entrées inconnues pour supprimer l'influence des perturbations et du bruit. Ensuite, nous développons une deuxième méthode de synchronisation utilisant un observateur adaptatif à modes glissants" pour une classe des systèmes chaotiques présentant des entrées inconnues et dont les signaux de sortie sont bruités. La synthèse de l'observateur s'appuie sur la théorie des modes glissants, les techniques de synthèse d'observateurs singuliers et les techniques adaptatives dans le but d'estimer conjointement l'état et les entrées inconnues malgré la présence du bruit dans les équations de sortie. Cette approche de synchronisation est ensuite employée dans un nouveau schéma de communication chaotique sécurisée dont l'objectif est d'augmenter le nombre et l'amplitude des messages transmis, améliorer le niveau de sécurité ainsi que la robustesse aux bruits présents dans le canal de communication. En outre, le scénario de présence des retards de transmission est étudié en élaborant une troisième approche de synchronisation à base d'observateurs adaptatifs pour une classe des systèmes chaotiques de Lur'e avec des non-linéarités à pente restreinte et des signaux de sortie retardés. En se basant sur la théorie de Lyapunov-Krasovskii et en utilisant une hypothèse d'excitation persistante, l'observateur adaptatif proposé garantit la synchronisation maitre-esclave et la restauration des informations transmises malgré l'existence des retards de transmission. Les résultats théoriques obtenus dans ce travail de thèse sont vérifiés à travers des applications de transmission d'informations utilisant différents modèles des systèmes chaotiques tout en étudiant les différents scénarios et cas de figure pouvant se présenter en pratique et en analysant les aspects de sécurité de ces systèmes.In this thesis, we develop synchronization methods of chaotic systems for information transmission applications. The first proposed method is based on adaptive unknown input observers for a class of chaotic systems subject to parametric uncertainties and perturbations in their dynamics and noise in outputs signals (Channel communication noise). The developed method is based on adaptive techniques to compensate nonlinearities to compensate nonlinearities and parametric uncertainties and to reconstruct the transmitted messages. Furthermore, this approach is based on unknown input observers design to reject the influence of perturbations and noise. Then, we develop a second synchronization method using an adaptive sliding mode observer for a class of chaotic systems subject to unknown inputs and such that the output equations are subject to noise. The observer design is based on sliding modes theory, descriptor observers design and adaptive control in order to join state and unknown input estimation despite the presence of noise in output equations. The latter synchronization approach is then exploited in a new secured communication scheme where the objective is to increase the number and amplitude of the transmitted messages, improve the level of security and the robustness to noise present in the communication channel. Moreover, the case of presence of transmission time-delays was investigated and a synchronization approach based on adaptive observers for a class of Lur e systems with slope restricted nonlinearities and delayed outputs. Based on the Lyapunov-Krasovskii theory and using a persistency of excitation property, the proposed adaptive observer ensures master-slave synchronization and the reconstruction of the transmitted messages despite the existence of transmission time-delays. The obtained theoretical results in this thesis are verified through transmission information applications using different models of chaotic systems in different scenarios and case-studies which may occur in practice. Cryptanalysis and security aspects of the proposed communication systems are also investigated.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Modelling and Adaptive Control; Proceedings of an IIASA Conference, Sopron, Hungary, July 1986

One of the main purposes of the workshop on Modelling and Adaptive Control at Sopron, Hungary, was to give an overview of both traditional and recent approaches to the twin theories of modelling and control which ultimately must incorporate some degree of uncertainty. The broad spectrum of processes for which solutions of some of these problems were proposed was itself a testament to the vitality of research on these fundamental issues. In particular, these proceedings contain new methods for the modelling and control of discrete event systems, linear systems, nonlinear dynamics and stochastic processes

Aeronautical Engineering: A Continuing Bibliography with Indexes (supplement 194)

This bibliography lists 369 reports, articles and other documents introduced into the NASA scientific and technical information system in November 1985