477 research outputs found
Algorithmes et architectures pour la commande et le diagnostic de systĂšmes critiques de vol
Flight-Critical Systems such as Electromechanical Actuators driven by Engine Control Units (ECU) or Flight Control Units (FCU) are designed and developed regarding drastic safety requirements. In this study, an actuator control and monitoring ECU architecture based on analytic redundancy is proposed. In case of fault occurrences, material redundancies in avionic equipment allow certaincritical systems to reconfigure or to switch into a safe mode. However, material redundancies increase aircraft equipment size, weight and power (SWaP). Monitoring based on dynamical models is an interesting way to further enhance safetyand availability without increasing the number of redundant items. Model-base dfault detection and isolation (FDI) methods [58, 26, 47] such as observers and parity space are recalled in this study. The properties of differential flatness for nonlinear systems [80, 41, 73] and endogenous feedback linearisation are used with nonlinear diagnosis models. Linear and nonlinear observers are then compared with an application on hybrid stepper motor (HSM). A testing bench was specially designed to observe in real-time the behaviour of the diagnosis models when faults occur on the stator windings of a HSM.Les systĂšmes critiques de vol tels que les actionneurs Ă©lectromĂ©caniques ainsi que les calculateurs de commande moteur (ECU) et de vol (FCU),sont conçus en tenant compte des contraintes aĂ©ronautiques sĂ©vĂšres de suretĂ© defonctionnement. Dans le cadre de cette Ă©tude, une architecture calculateur pourla commande et la surveillance dâactionneurs moteur et de surfaces de vol est proposĂ©e et Ă fait lâobjet dâun brevet [13]. Pour garantir ces mesure de suretĂ©, les ECU et FCU prĂ©sentent des redondances matĂ©rielles multiples, mais engendrent une augmentation de lâencombrement, du poids et de lâĂ©nergie consommĂ©e. Pour ces raisons, les redondances Ă base de modĂšles dynamiques, prĂ©sentent un atout majeur pour les calculateurs car elles permettent dans certains cas de maintenir les exigences dâintĂ©gritĂ© et de disponibilitĂ© tout en rĂ©duisant le nombre de capteurs ou dâactionneurs. Un rappel sur les mĂ©thodes de diagnostic par gĂ©nĂ©rateurs de rĂ©sidus et estimateurs dâĂ©tats [58, 26, 47] est effectuĂ© dans cette Ă©tude. Les propriĂ©tĂ©s de platitude diffĂ©rentielle et la linĂ©arisation par diffĂ©omorphisme et bouclage endogĂšne [80, 41, 73] permettent dâutiliser des modĂšles linĂ©aires Ă©quivalents avec les gĂ©nĂ©rateurs de rĂ©sidus. Un banc dâessai a Ă©tĂ© conçu afin de valider les performances des algorithmes de diagnostic
Contribution au diagnostic de pannes pour\ud les systÚmes différentiellement plats
Cette thĂšse sâintĂ©resse au diagnostic de pannes dans les systĂšmes diffĂ©rentiellement plats, ceci constituant une large classe de systĂšmes non linĂ©aires. La propriĂ©tĂ© de platitude diffĂ©rentielle est caractĂ©risĂ©e par des relations qui permettent dâexprimer les Ă©tats dâun systĂšme et ses entrĂ©es en fonction de ses sorties plates et de leurs dĂ©rivĂ©es. Ces relations qui sont Ă la base de la commande plate sont aussi utiles pour la rĂ©alisation du diagnostic de pannes. Ainsi sont introduites les notions de minimalitĂ© pour les sorties plates, de platitude stricte et de degrĂ© additionnel de redondance. Ceci conduit Ă la proposition dâune mĂ©thode globale de dĂ©tection de pannes basĂ©e sur la platitude. Partant alors de la constatation que les systĂšmes diffĂ©rentiellement plats de complexitĂ© Ă©levĂ©e sont souvent constituer de sous systĂšmes eux mĂȘmes diffĂ©rentiellement plats, lâapproche de dĂ©tection de pannes prĂ©cĂ©dente peut ĂȘtre dĂ©multipliĂ©e au sein de cette structure de façon Ă en identifier les sous systĂšmes dĂ©faillants. On sâintĂ©resse alors au cas courant de la platitude diffĂ©rentielle implicite et on montre dans le cadre dâune application aĂ©ronautique comment les rĂ©seaux de neurones permettent de constituer une solution numĂ©rique au problĂšme de dĂ©tection de pannes. La disponibilitĂ© en temps rĂ©el de dĂ©rivĂ©es successives des sorties Ă©tant essentielle pour la mise en oeuvre de ces mĂ©thodes, on Ă©tudie alors les performances dâun filtre dĂ©rivateur alors que le systĂšme est lui-mĂȘme soumis Ă une commande plate, ceci conduira a modifiĂ© lĂ©gĂšrement une telle loi de commande afin dâeffectuer lâeffet des erreurs dâestimation. On sâintĂ©resse finalement Ă la dĂ©tection des pannes dans les systĂšmes chaotiques diffĂ©rentiellement plats. On montre sur plusieurs exemples comment la propriĂ©tĂ© de platitude peut ĂȘtre mise Ă profit pour dĂ©tecter et identifier des variations paramĂ©triques au sein dâun tel type de systĂšme chaotique. Des rĂ©sultats de simulation sont prĂ©sentĂ©s. Finalement des thĂšmes de recherche complĂ©mentaires Ă cette approche sont relevĂ©s. --------------------------------------------------------------------- This thesis is devoted to the diagnostic of faults in differentially flat systems, where\ud
differentially flat systems constitute a rather large class of non linear systems. The flatness\ud
property is characterized by relations allowing to express states and input as functions of the\ud
outputs and their derivatives up to a finite order. These relations are the basis for the synthesis\ud
of flat control laws and are, is it displayed here, useful to perform an efficient diagnostic of\ud
additional redundancy degree. Then a global fault detection method based on the flatness\ud
property is proposed. It is shown that many differentially flat subsystems so that the proposed\ud
fault detection method can be applied within the corresponding structure allowing then the\ud
identification of faulty subsystems. Then the frequent case of implicitly differentially flat\ud
systems is considered and it is shown through an aeronautical application that neural networks\ud
can provide a numerical solution approach to this fault detection problem. Since with this\ud
approach the one line availability of successive derivatives of the outputs is imperative, the\ud
performance of a derivative filter is studied. To eliminate the effect of the resulting estimation\ud
errors, some improvements are introduced to the current flat control law. In the last section of\ud
the report the diagnostic of differentially flat chaotic systems is considered. In different cases it is shown how the differential flatness property can be used to detect and identify variations of the parameters of the chaotic system. Simulation results are displayed. Finally some complementary fields of research are pointed out\u
SIRU development. Volume 1: System development
A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results
A Novel Collision Avoidance Logic for Unmanned Aerial Vehicles Using Real-Time Trajectory Planning
An effective collision avoidance logic should prevent collision without excessive
alerting. This requirement would be even more stringent for an
automatic collision avoidance logic, which is probably required by Unmanned
Aerial Vehicles to mitigate the impact of delayed or lost link issues.
In order to improve the safety performance and reduce the frequency
of false alarms, this thesis proposes a novel collision avoidance logic based
on the three-layer architecture and a real-time trajectory planning method.
The aim of this thesis is to develop a real-time trajectory planning algorithm
for the proposed collision avoidance logic and to determine the integrated
logicâs feasibility, merits and limitations for practical applications.
To develop the trajectory planning algorithm, an optimal control problem
is formulated and an inverse-dynamic direct method along with a two
stage, derivative-free pattern search method is used as the solution approach.
The developed algorithm is able to take into account the flyability
of three dimensional manoeuvres, the robustness to the intruder state uncertainty
and the field-of-regard restriction of surveillance sensors. The
testing results show that the standalone executable of the algorithm is able
to provide a flyable avoidance trajectory with a maximum computation
time less than 0.5 seconds.
To evaluate the performance of the proposed logic, an evaluation framework
for Monte Carlo simulations and a baseline approach for comparison
are constructed. Based on five Monte Carlo simulation experiments, it is
found that the proposed logic should be feasible as 1) it is able to achieve
an update rate of 2Hz, 2) its safety performance is comparable with a reference
requirement from another initial feasibility study, and 3) despite a
0.5 seconds computation latency, it outperforms the baseline approach in
terms of safety performance and robustness to sensor and feedback error
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