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1

Spacecraft attitude fault tolerant control based on multi-objective optimization

Moradi Rouzbeh, Alikhani Alireza, Fathi Jegarkandi Mohsen

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 4

983--996

EN

An active fault tolerant controller is designed for the attitude control of a faulty spacecraft. Feedback linearization and Lyapunov’s direct method are used to solve angular velocity equations and to ensure convergence of the system outputs to reference inputs, respectively. In order to ensure finite time convergence, final time constraints are proposed. Three con- structive objective functions are considered as performance measures and optimized using multi-objective optimization. The results show that the outputs converge to the reference attitudes, even for severe actuator faults/failures.

2

Redukcja hałasu w pomieszczeniu z zaburzeniem wibroakustycznym poprzez optymalny rozkład materiału dźwiękochłonnego

Błażejewski A.

Pomiary Automatyka Kontrola

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2012

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R. 58, nr 6

536-539

PL

Praca dotyczy zagadnienia rozmieszczenia porowatego materiału absorbującego o zespolonej impedancji akustycznej na brzegach obszaru (pomieszczenia), w którym umieszczone zostało harmoniczne źródło wibroakustyczne. Uproszczony model rozkładu ciśnienia akustycznego w pomieszczeniu uzyskano stosując analizę modalną. Do rozwiązania problemu optymalizacji wykorzystano algorytm genetyczny. Połączenie uproszonego modelu oraz algo-rytmu genetycznego, pozwala na znaczne szybsze i mniej kosztowne obliczeniowo, uzyskiwanie wyników optymalizacji, w postaci rozkładu materiału absorpcyjnego w pomieszczeniu.

EN

In the paper a problem how to properly influence an acoustic field in the enclosure with a Vibro-acoustical source [1] inside is considered. Particularly, optimization of the configuration of an acoustic absorber, i.e. porous material characterized by a complex impedance on the boundary, is presented [2]. The combination of the modal approach to modeling of the room acoustic field and the artificial intelligence methods to the optimization is a new attitude to the problem. In order to describe the acoustic pressure distribution inside the enclosure, the modal analysis with modal coupling was applied and presented in Section 2. In this case the acoustic pressure distribution in the room is a sum over a set of the room eigenfunctions and proper time components i.e. modal amplitudes [2, 3]. The formulae describing these amplitudes were obtained and eventually introduced into the multi-objective function definition [2, 4] in Section 3. The acoustic impedances on the room boundaries correlated with the material thickness were selected as design variables. In order to solve the optimization problem defined in Section 3 directly, a genetic algorithm was applied. The non-dominated solutions were searched in the process [2, 4, 5, 6]. The main ingredients of the algorithm and its settings are described in Section 4. In Section 5 the example object (room) is specified and shown in detail in Tab. 1. Applying a specific acoustic absorber on the boundary [2, 7], the room with the harmonic source was modified according to the optimization method. As the result, the set of the Pareto-optimal solutions was obtained (see Fig. 1). One solution of the Pareto set was selected and corresponding, particular boundaries covering with the acoustic absorber are shown in Fig. 2. Last, the model accuracy and the optimization results, i.e. noise reduction, are presented in Figs. 3a and 3b. The result verification was performed by comparison with the acoustic measurements (see Figs. 3c and 3d).

3

Multi - criteria decision making using fuzzy preference relations

Borzęcka H.

Operations Research and Decisions

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2012

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Vol. 22, No. 3

5--21

EN

When dealing with multi-criteria decision making problems, the concept of Pareto-optimality and Pareto-dominance may be inefficient (e.g. generally multiple solutions exist), especially when there is a large number of criteria. Our paper considers the fuzzy multi-criteria decision making problem based on Zadeh’s linguistic approach to P-optimality and P-dominance. The construction, analysis and application of a model of multi-criteria decision making using a fuzzy preference relation are considered. The paper is dedicated to the problem of modeling preferences in terms of fuzzy binary relations and provides an introduction to the important problem of forming fuzzy preference relations to analyze models of multi-attribute decision making. The key features of the multi-criteria evaluation, comparison, choice and ordering of alternatives in a fuzzy environment using fuzzy preference relations have been introduced.