Contributions to fuzzy polynomial techniques for stability analysis and control

The present thesis employs fuzzy-polynomial control techniques in order to improve the stability analysis and control of nonlinear systems. Initially, it reviews the more extended techniques in the field of Takagi-Sugeno fuzzy systems, such as the more relevant results about polynomial and fuzzy polynomial systems. The basic framework uses fuzzy polynomial models by Taylor series and sum-of-squares techniques (semidefinite programming) in order to obtain stability guarantees. The contributions of the thesis are: ¿ Improved domain of attraction estimation of nonlinear systems for both continuous-time and discrete-time cases. An iterative methodology based on invariant-set results is presented for obtaining polynomial boundaries of such domain of attraction. ¿ Extension of the above problem to the case with bounded persistent disturbances acting. Different characterizations of inescapable sets with polynomial boundaries are determined. ¿ State estimation: extension of the previous results in literature to the case of fuzzy observers with polynomial gains, guaranteeing stability of the estimation error and inescapability in a subset of the zone where the model is valid. ¿ Proposal of a polynomial Lyapunov function with discrete delay in order to improve some polynomial control designs from literature. Preliminary extension to the fuzzy polynomial case. Last chapters present a preliminary experimental work in order to check and validate the theoretical results on real platforms in the future.Pitarch Pérez, JL. (2013). Contributions to fuzzy polynomial techniques for stability analysis and control [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34773TESI

Optimisation of transient and ultimate inescapable sets with polynomial boundaries for nonlinear systems

[EN] This paper addresses the problem of bounding the trajectories of nonlinear systems (transient and ultimate bounds) from initial conditions in given sets, when subject to possibly nonvanishing disturbances constrained by some finite-interval integral bounds, with a suitable controller. The so-called robustly inescapable sets are determined from such initial conditions and disturbance bounds. In order to get numerical results, the approach considers embedding the nonlinear dynamics in a convex combination of polynomials, and solving sum-of-squares (SOS) problems on them, optimising some inescapable-set size parameters. Determination of approximate (locally) optimal solutions usually requires an iterative evaluation of SOS problems, because of products of decision variables. (C) 2016 Elsevier Ltd. All rights reserved.The research leading to these results has received funding from the European Union (FP7/2007-2013 no 604068) and from the Spanish Government (MINECO/FEDER DPI2015-70975-P, DPI2016-81002). The material in this paper was not presented at any conference. This paper was recommended for publication in revised form by Associate Editor Graziano Chesi under the direction of Editor Richard Middleton.Sala, A.; Pitarch, JL. (2016). Optimisation of transient and ultimate inescapable sets with polynomial boundaries for nonlinear systems. Automatica. 73:82-87. https://doi.org/10.1016/j.automatica.2016.06.017S82877

Report on Dynamic Data Reconciliation of Large-Scale Processes

Producción CientíficaAvailability of reliable process information in real time is key in any decision-making procedure. Thus, good industrial decision-support implementations require dealing with gross errors and consideration of process transients in order to get a set of measurements which will be coherent with the basic underlying process dynamics. This report presents dynamic data reconciliation methods and tools adapted to the requirements of industrial environments (large-scale systems and noisy/faulty data). Moreover, basic concepts in literature are extended to artificially increase system redundancy as well as to cope with time-varying parameter estimation. The procedure summarized in this report has been tested in the Lenzing case study.Ingeniería de Sistemas y AutomáticaEuropean Union Horizon 2020 program (grant nº 723575

Real-time optimisation for a heat-recovery section with equipment degradation

[Abstract] This work aims to optimise the operation of an industrial heat-recovery section in a fibre-production factory. The section is formed by a network of heat exchangers able to be supplied with different hot sources. The goal is minimising the resource utilisation in real time (the sources usage) while satisfying a set of operational constrains. Hence, problems of economically optimal hot-sources allocation to heat exchangers arise. The problem is formulated and solved via mixed-integer non-linear programming. Furthermore, concerns about the practical implementation and the degradation of the equipment due to the fouling effect are also taken into account in the optimisation. In this way, the decision-support tool not only provides the optimal allocation, but also suggestions on which heat exchangers are potentially beneficial to be clean.Ministerio de Ciencia, Innovación y Universidades; PGC2018-099312-B-C3

Fatigue testing and properties of hardmetals in the gigacycle range

Hardmetal products are frequently fatigue loaded in service, such as e.g. cutting tools for milling or percussion drills. In the present work, the fatigue behaviour of hardmetals was investigated into the gigacycle range using ultrasonic resonance fatigue testing at 20 kHz in push-pull mode at R = - 1. Liquid cooling was afforded using water with addition of a corrosion inhibitor. Hourglass shaped specimens were prepared, the surface being ground and polished with subsequent stress-relieving anneal to remove the high compressive residual stresses introduced during grinding. S-N curves with fairly low scatter were obtained, which indicates microstructure-controlled and not defect-controlled failure. Low binder content as well as fine WC grains were found to improve the fatigue endurance strength. In no case, however, a horizontal branch of the S-N curve was observed, i.e. there is no fatigue “limit” at least up to 1010 cycles. The initiation sites were in part difficult to identify; in such cases when the site was clearly visible, decohesion of the binder from large WC grains seems to have caused crack initiation. This further corroborates that microstructural features and not singular defects as e.g. inclusions are the initiation sites, which underlines the high purity of the hardmetal grades used. Based on fracture mechanical consideration a damage diagram was determined allowing to deduce critical defect sizes.Peer ReviewedPostprint (author's final draft

Development of a grey model for a medium density fibreboard dryer in ecosimpro

[Abstract] This work contains the design and testing of a greybox model based on first principles for the drying section of a Medium Density Fiberboard (MDF) manufacturing plant for use in a Model-Predictive Controller (MPC).The fitting of the model to experimental data has been solved with the data reconciliation technique, and the model has then been implemented and tested in simulation for proper behavior. Due to lac k of information in a number of relevant process values, as well as low trustworthiness of some measurements,state and disturbance estimators have been determined as necessary to include in the final MPC control schema.Ministerio de Economía y Competitividad; DPI2015-70975-

Diagnóstico anatomopatológico de las principales lesiones encontradas en rumiantes sacrificados en matadero

El sistema utilizado para la inspección postmortem en todos los mataderos de la Unión Europea está basado en la inspección visual de los órganos identificados como patológicos y su posterior destrucción como material especificado de riesgo. En numerosas ocasiones, el diagnóstico certero de la enfermedad queda simplificado a neumonías, parasitosis, enteritis, sin disponer de un diagnóstico microscópico que describa apropiadamente la lesión e intente aproximarse a un diagnóstico presuntivo de la enfermedad que padecen los animales sacrificados. El objetivo de este trabajo es realizar el estudio anatomopatológico de las lesiones más frecuentes encontradas en los rumiantes sacrificados en matadero y que por tanto son causa de decomiso. Para ello, se ha llevado a cabo un muestreo de los principales órganos afectados, haciendo hincapié en los aparatos respiratorio y digestivo para comprobar si el diagnóstico macroscópico realizado en los mataderos es eficiente, correcto y suficiente. Se ha observado que los órganos más frecuentemente decomisados son los pulmones y el hígado, tanto en bovino como en pequeños rumiantes. Las principales causas son el síndrome respiratorio bovino y las neumonías catarrales por micoplasmas en ganado bovino y ovino respectivamente. En el caso del hígado las principales razones de no aptitud en bovino son las parasitosis por fasciola y en los pequeños rumiantes las cisticercosis. Se ha concluido que el sistema de inspección oficial empleado en los mataderos españoles es eficaz y detecta los procesos patológicos que suponen un problema para la salud pública y que las leyes que rigen dichas actividades son correctas y suficientes

Closed-form estimates of the domain of attraction for nonlinear systems via fuzzy-polynomial models

In this work, the domain of attraction of the origin of a nonlinear system is estimated in closed-form via level sets with polynomial boundary, iteratively computed. In particular, the domain of attraction is expanded from a previous estimate, such as, for instance, a classical Lyapunov level set. With the use of fuzzy-polynomial models, the domain-of-attraction analysis can be carried out via sum of squares optimization and an iterative algorithm. The result is a function wich bounds the domain of attraction, free from the usual restriction of being positive and decrescent in all the interior of its level sets

A systematic grey-box modeling methodology via data reconciliation and SOS constrained regression

Producción CientíficaDeveloping the so-called grey box or hybrid models of limited complexity for process systems is the cornerstone in advanced control and real-time optimization routines. These models must be based on fundamental principles and customized with sub-models obtained from process experimental data. This allows the engineer to transfer the available process knowledge into a model. However, there is still a lack of a flexible but systematic methodology for grey-box modeling which ensures certain coherence of the experimental sub-models with the process physics. This paper proposes such a methodology based in data reconciliation (DR) and polynomial constrained regression. A nonlinear optimization of limited complexity is to be solved in the DR stage, whereas the proposed constrained regression is based in sum-of-squares (SOS) convex programming. It is shown how several desirable features on the polynomial regressors can be naturally enforced in this optimization framework. The goodnesses of the proposed methodology are illustrated through: (1) an academic example and (2) an industrial evaporation plant with real experimental data.Ministerio de Economía, Industria y Competitividad (grant DPI2016-81002-R

Investigations on micro-mechanical properties of polycrystalline Ti(C,N) and Zr(C,N) coatings

Micro-mechanical properties of Ti(C,N) and Zr(C,N) coatings deposited by chemical vapor deposition on a WC-Co cemented carbide substrate were examined by micro-compression testing using a nanoindenter equipped with a flat punch. Scanning Electron Microscopy, Focused Ion Beam, Electron Backscattered Diffraction and Finite Element Modeling were combined to analyze the deformation mechanisms of the carbonitride layers at room temperature. The results revealed that Ti(C,N) undergoes a pure intergranular crack propagation and grain decohesion under uniaxial compression; whereas the fracture mode of Zr(C,N) was observed to be inter/transgranular failure with unexpected plastic deformation at room temperature.Peer ReviewedPostprint (author's final draft