66 research outputs found
Nemlineáris dinamikus rendszerek analĂzis alapĂş irányĂtása = Analysis-based control of nonlinear dynamical systems
Rövid összefoglalĂł Nemlineáris dinamikus rendszerek analĂzisĂ©nek Ă©s irányĂtásának terĂĽletĂ©n folytattunk kutatásokat. Az analĂzis eredmĂ©nyeit kĂĽlönbözĹ‘ irányĂtási cĂ©lokat megvalĂłsĂtĂł szabályozási struktĂşrák tervezĂ©sĂ©hez használtuk fel. 1. Nemlineáris dinamikus rendszerek analĂzise Ă©s identifikáciĂłja GráfelmĂ©letti megközelĂtĂ©sen alapulĂł mĂłdszert adtunk arra, hogy differenciál-algebrai rendszermodellek egyszerűsĂtĂ©se során hogyan kaphatunk 1-es indexű modellt eredmĂ©nyĂĽl. Kapcsolatot találtunk kvázipolinomiális (QP) rendszerek globális stabilitása Ă©s lokális disszipatĂv hamiltoni leĂrása között. Polinomiális idejű algoritmust adtunk QP rendszerek invariánsainak a modellegyenletekbĹ‘l törtĂ©nĹ‘ visszanyerĂ©sĂ©re. Megmutattuk, hogy a lineárisan fĂĽggetlen reakciĂłvektorokkal rendelkezĹ‘ reverzibilis reakciĂłhálĂłzatok egyensĂşlyi pont körĂĽli lokális disszipatĂv hamiltoni struktĂşrával rendelkeznek. Nyomottvizes reaktorok primerköri dinamikáját identifikáltuk a modell rĂ©szrendszerekre törtĂ©nĹ‘ szĂ©tválasztása alapján. 2. Nemlineáris dinamikus rendszerek irányĂtása Bilineáris mátrixegyenlĹ‘tlensĂ©g megoldására vezetĹ‘ stabilizálĂł visszacsatolást terveztĂĽnk QP rendszerekre. A terhelĹ‘nyomatĂ©k on-line becslĂ©sĂ©t is tartalmazĂł adaptĂv referenciakövetĹ‘ szabályozĂłt terveztĂĽnk kisteljesĂtmĂ©nyű gázturbuna modelljĂ©re. Az identifikált atomerĹ‘művi primerköri modellre az elĹ‘Ărt korlátozásokat betartĂł modell-prediktĂv szabályozĂłkat terveztĂĽnk. KĂ©tszintű szabályozĂłt terveztĂĽnk gĂ©pjárművek aktĂv felfĂĽggesztĂ©sĂ©hez. | Short summary An interdisciplinary research has been conducted in the field of analysis and control of nonlinear dynamical systems. The results of the analysis have been used to design feedback structures for different control goals. 1. Analysis and identification of nonlinear dynamical systems A method based on graph theory has been proposed for the construction of index-1 models during model simplification. Connections have been found between the global stability and local dissipative-Hamiltonian description of quasi-polynomial (QP) systems. A polynomial time algorithm has been worked out for obtaining invariants of QP systems from the model equations. It has been shown that reversible reaction networks with independent reaction vectors possess a local dissipative Hamiltonian structure around the equilibrium point. The identification of the primary circuit dynamics of pressurized water reactors have been carried out based on the decomposition of the overall model. 2. Control of nonlinear dynamical systems Stabilizing feedback has been computed for QP systems that leads to the solution of a bilinear matrix inequality. An adaptive reference tracking controller has been designed for a low power gas turbine that contains the on-line estimation of the load torque. Model-predictive controllers have been designed for the identified primary circuit dynamics that satisfy the predefined constraints. A two-level controller has been designed for the active suspension of road vehicles
RendszermodellezĂ©s mĂ©rĂ©si adatokbĂłl, hibrid-neurális megközelĂtĂ©s = System modelling from measurement data: hybrid-neural approach
A kutatás cĂ©lja mĂ©rĂ©si adatok alapján törtĂ©nĹ‘ rendszermodellezĂ©si eljárások kidolgozása Ă©s vizsgálata volt, kĂĽlönös tekintettel a nemlineáris rendszerek modellezĂ©sĂ©re. A kutatás során többfĂ©le megközelĂtĂ©st alkalmaztunk: egyrĂ©szt a rendszermodellezĂ©si feladatok megoldásánál a lineáris rendszerekre kidolgozott eljárásokbĂłl indultunk ki nemlineáris hatásokat is figyelembe vĂ©ve, másrĂ©szt fekete doboz megközelĂtĂ©seket alkalmaztunk, ahol elsĹ‘dlegesen input-output adatokbĂłl törtĂ©nik a modell konstrukciĂł. Az elĹ‘bbi megközelĂtĂ©s kĂĽlönösen gyengĂ©n nemlineáris rendszerek modellezĂ©sĂ©nĂ©l tűnik járhatĂł Ăştnak, ahol a gyengĂ©n nemlineáris rendszereket, mint nemlineárisan torzĂtott lineáris rendszereket tekintjĂĽk. A nemlineáris torzĂtások hatásának megĂ©rtĂ©sĂ©re egy teljes elmĂ©letet dolgoztunk ki. A fekete doboz modellezĂ©snĂ©l általános modell-struktĂşrákbĂłl indulunk ki, melyek paramĂ©tereit a rendelkezĂ©sre állĂł mĂ©rĂ©si adatok felhasználásával, tanulással határozhatjuk meg. Ekkor az alapvetĹ‘ kĂ©rdĂ©sek a megfelelĹ‘ kiindulĂł adatbázis kialakĂtására Ă©s az adatokkal kapcsolatos problĂ©mákra (zajos adatok, kiugrĂł adatok, inkonzisztens adatok, redundáns adatok, stb.) irányultak, továbbá arra hogy hogyan lehet a fekete doboz modellstruktĂşra komplexitását kĂ©zben tartani Ă©s az adatokon tĂşl meglĂ©vĹ‘ egyĂ©b informáciĂł hatĂ©kony figyelembevĂ©telĂ©t biztosĂtani. A fekete doboz modellezĂ©snĂ©l neuronhálĂłkat Ă©s szupport vektor gĂ©peket vettĂĽnk figyelembe Ă©s a minĂ©l kisebb modell-komplexitás elĂ©rĂ©sĂ©re törekedtĂĽnk. | The goal of the research was to develop and analyse system modelling procedures, especially for modelling non-linear systems. To reach the goal different approaches were applied. One approach is to use procedures developed for linear system modelling, where nonlinear effects are taken into consideration. The other approach applied is black box modelling, where model-construction is mainly based on input-output data. The first approach proved to be successful especially for the modelling of weakly non-linear systems, where these systems are considered as linear ones with the presence of nonlinear distortion. To understand nonlinear distortions a whole theory has been developed. For black box modelling the starting point was the use of certain general model-structures, where the parameters of these structures are determined by training using measurement data. The most relevant questions in this case are related to the construction of data base, and the problems of quality of the available data (noisy data, missing data, outliers, inconsistent data, redundant data, etc.), A further important goal was to find proper ways to utilise additional knowledge and at the same time to reduce model complexity. For black box modelling some special neural network architectures and support vector machines were considered
From Nonlinear Identification to Linear Parameter Varying Models: Benchmark Examples
Linear parameter-varying (LPV) models form a powerful model class to analyze
and control a (nonlinear) system of interest. Identifying a LPV model of a
nonlinear system can be challenging due to the difficulty of selecting the
scheduling variable(s) a priori, which is quite challenging in case a first
principles based understanding of the system is unavailable.
This paper presents a systematic LPV embedding approach starting from
nonlinear fractional representation models. A nonlinear system is identified
first using a nonlinear block-oriented linear fractional representation (LFR)
model. This nonlinear LFR model class is embedded into the LPV model class by
factorization of the static nonlinear block present in the model. As a result
of the factorization a LPV-LFR or a LPV state-space model with an affine
dependency results. This approach facilitates the selection of the scheduling
variable from a data-driven perspective. Furthermore the estimation is not
affected by measurement noise on the scheduling variables, which is often left
untreated by LPV model identification methods.
The proposed approach is illustrated on two well-established nonlinear
modeling benchmark examples
Algebraic observer design for PEM fuel cell system
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, the concept of the algebraic observer is applied to Proton Exchange Membrane Fuel Cell (PEMFC) system. The aim of the proposed observer is to reconstruct the oxygen excess ratio through estimation of their relevant states in real time from the measurement of the supply manifold air pressure. A robust differentiation method is adopted to estimate in finite-time the time derivative of the supply manifold air pressure. Then, the relevant states are reconstructed based on the output-state inversion model. The objective is to minimize the use of extra sensors in order to reduce the costs and enhance the system accuracy. The performance of the proposed observer is analyzed through simulations considering measurement noise and different stack-current variations. The results show that the algebraic observer estimates in finite time and robustly the oxygen-excess ratio.Peer ReviewedPostprint (author's final draft
Towards a Computer Algebraic Algorithm for Flat Output Determination
This contribution deals with nonlinear control systems. More precisely, we are interested in the formal computation of a so-called flat output, a particular generalized output whose property is, roughly speaking, that all the integral curves of the system may be expressed as smooth functions of the components of this flat output and their successive time derivatives up to a finite order (to be determined). Recently, a characterization of such flat output has been obtained in [14, 15], in the framework of manifolds of jets of infinite order (see e.g. [18, 9]), that yields an abstract algorithm for its computation. In this paper it is discussed how these conditions can be checked using computer algebra. All steps of the algorithm are discussed for the simple (but rich enough) example of a non holonomic car
Flatness Characterization: Two Approaches
We survey two approaches to flatness necessary and sufficient conditions and compare them on examples
Fractional equations and diffusive systems: an overview
The aim of this discussion is to give a broad view of the links between fractional differential equations (FDEs) or fractional partial differential equations (FPDEs) and so-called diffusive representations (DR). Many aspects will be investigated: theory and numerics, continuous time and discrete time, linear and nonlinear equations, causal and anti-causal operators, optimal diffusive representations, fractional Laplacian.
Many applications will be given, in acoustics, continuum mechanics, electromagnetism, identification, ..
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