Integration Techniques of Fault Detection and Isolation Using Interval Observers

An interval observer has been illustrated to be a suitable approach to detect and isolate faults affecting complex dynamical industrial systems. Concerning fault detection, interval observation is an appropriate passive robust strategy to generate an adaptive threshold to be used in residual evaluation when model uncertainty is located in parameters (interval model). In such approach, the observer gain is a key parameter since it determines the time evolution of the residual sensitivity to a fault and the minimum detectable fault. This thesis illustrates that the whole fault detection process is ruled by the dynamics of the fault residual sensitivity functions and by the time evolution of the adaptive threshold related to the interval observer. Besides, it must be taken into account that these two observer fault detection properties depend on the used observer gain. As a consequence, the observer gain becomes a tuning parameter which allows enhancing the observer fault detection performance while avoiding some drawbacks related to the analytical models, as the wrapping effect. In this thesis, the effect of the observer gain on fault detection and how this parameter can avoid some observer drawbacks (i.e. wrapping effect) are deeply analyzed. One of the results of this analysis is the determination of the minimum detectable fault function related to a given fault type. This function allows introducing a fault classification according to the fault detectability time evolution: permanently (strongly) detected, non-permanently (weakly) detected or just non-detected. In this fault detection part of this thesis, two examples have been used to illustrate the derived results: a mineral grinding-classification process and an industrial servo actuator. Concerning the interface between fault detection and fault isolation, this thesis shows that both modules can not be considered separately since the fault detection process has an important influence on the fault isolation result. This influence is not only due to the time evolution of the fault signals generated by the fault detection module but also to the fact that the fault residual sensitivity functions determines the faults which are affecting a given fault signal and the dynamics of this fault signal for each fault. This thesis illustrates this point suggesting that the interface between fault detection and fault isolation must consider a set of fault signals properties: binary property, sign property, fault residual sensitivity property, occurrence order property and occurrence time instant property. Moreover, as a result of the influence of the observer gain on the fault detection stage and on the fault residual sensitivity functions, this thesis demonstrates that the observer gain has also a key role in the fault isolation module which might allow enhancing its performance when this parameter is tuned properly (i.e. fault distinguishability may be increased). As a last point, this thesis analyzes the timed discrete-event nature of the fault signals generated by the fault detection module. As a consequence, it suggests using timed discrete-event models to model the fault isolation module. This thesis illustrates that this kind of models allow enhancing the fault isolation result. Moreover, as the monitored system is modelled using an interval observer, this thesis shows as this qualitative fault isolation model can be built up on the grounds of this system analytical model. Finally, the proposed fault isolation method is applied to detect and isolate faults of the Barcelona’s urban sewer system limnimeters. Keywords: Fault Detection, Fault Diagnosis, Robustness, Observers, Intervals, Discrete-event Systems.En la presente tesis se demuestra que el uso de observadores intervalares para detectar y aislar fallos en sistemas dinámicos complejos constituye una estrategia apropiada. En la etapa de detección del fallo, dicha estrategia permite determinar el umbral adaptativo usado en la evaluación del residuo (robustez pasiva). Dicha metodología, responde a la consideración de modelos con parámetros inciertos (modelos intervalares). En dicho enfoque, la ganancia del observador es un parámetro clave que permite determinar la evolución temporal de la sensibilidad del residuo a un fallo y el mínimo fallo detectable para un tipo de fallo determinado. Esta tesis establece que todo el proceso de detección de fallos viene determinado por la dinámica de las funciones sensibilidad del residuo a los diferentes fallos considerados y por la evolución temporal del umbral adaptativo asociado al observador intervalar. Además, se debe tener en cuenta que estas dos propiedades del observador respecto la detección de fallos dependen de la ganancia del observador. En consecuencia, la ganancia del observador se convierte en el parámetro de diseño que permite mejorar las prestaciones de dicho modelo respecto la detección de fallos mientras que permite evitar algunos defectos asociados al uso de modelos intervalares, como el efecto wrapping. Uno de los resultados obtenidos es la determinación de la función fallo mínimo detectable para un tipo de fallo dado. Esta función permite introducir una clasificación de los fallos en función de la evolución temporal de su detectabilidad: fallos permanentemente detectados, fallos no permanentemente detectados y fallos no detectados. En la primera parte de la tesis centrada en la detección de fallos se utilizan dos ejemplos para ilustrar los resultados obtenidos: un proceso de trituración y separación de minerales y un servoactuador industrial. Respecto a la interfaz entre la etapa de detección de fallos y el proceso de aislamiento, esta tesis muestra que ambos módulos no pueden considerarse separadamente dado que el proceso de detección tiene una importante influencia en el resultado de la etapa de aislamiento. Esta influencia no es debida sólo a la evolución temporal de las señales de fallo generados por el módulo de detección sino también porque las funciones sensibilidad del residuo a los diferentes posibles fallos determinan los fallos que afectan a un determinado señal de fallo y la dinámica de éste para cada uno de los fallos. Esta tesis ilustra este punto sugiriendo que el interfaz entre detección y aislamiento del fallo debe considerar un conjunto de propiedades de dichos señales: propiedad binaria, propiedad del signo, propiedad de la sensibilidad del residuo a un fallo dado, propiedad del orden de aparición de las señales causados por los fallos y la propiedad del tiempo de aparición de estos. Además, como resultado de la influencia de la ganancia del observador en la etapa de detección y en las funciones sensibilidad asociadas a los residuos, esta tesis ilustra que la ganancia del observador tiene también un papel crucial en el módulo de aislamiento, el cual podría permitir mejorar el comportamiento de dicho módulo diseñando éste parámetro del observador de forma adecuada (Ej. Incrementar la distinción de los fallos para su mejor aislamiento). Como último punto, esta tesis analiza la naturaleza temporal de eventos discretos asociada a las señales de fallo generados por el módulo de detección. A consecuencia, se sugiere usar modelos de eventos discretos temporales para modelizar el módulo de aislamiento del fallo. Esta tesis muestra que este tipo de modelos permite mejorar el resultado de aislamiento del fallo. Además, dado que el sistema monitorizado es modelado usando un observador intervalar, esta tesis muestra como este modelo cualitativo de aislamiento puede ser construido usando dicho modelo analítico del sistema. Finalmente, el método propuesto de aislamiento del fallo es aplicado para detectar y aislar fallos en los limnimetros del sistema de alcantarillado de Barcelona. Palabras clave: Detección de Fallos, Diagnosis de Fallos, Robusteza, Observadores, Intervalos, Sistemas de Eventos Discretos

Practical-Oriented Pressure Sensor Placement For Model-Based Leakage Location In Water Distribution Networks

In order to bring remarkable benefits to operation and management of water networks, the analysis of sensed data can be used to locate water leaks using of a model-based methodology. However, the number of sensors installed is usually limited because of budget constraints and hence a strategy for optimizing their number and placement is required. This optimization is tightly coupled to the performance of the real-time model-based leakage diagnosis operation and hence the former should consider the requirements of the latter: (1) high distinguishability among all potential leaks to be detected; and (2) strong robustness in front of model-reality mismatches and other uncertainties. This paper describes a model-based pressure sensor placement optimization technique that focuses on the previous aspects and addresses practicality issues that arise in a real deployment. The technique uses an optimization method based on Genetic Algorithms that, unlike most common approaches in literature, avoids using a binary reasoning process. This increases the information granularity resulting in an improvement of both the leak distinguishability and the method robustness. Moreover, the technique also addresses the practical concerns by deriving an enhanced cost function. Finally, the method is validated in a District Metered Area of the Barcelona water distribution network. Results indicate that a good enough detection accuracy can be achieved with a low number of optimally placed sensors

Advanced integrated real-time control of combined Urban drainage systems using MPC

Combined urban drainage system (CUDS) collect both wastewater and raining water through sewer networks to wastewater treatment plants (WWTP) before releasing to the environment. During storm weather, rain and wastewater can overload the capacity of the CUDS and/or the WWTPs, producing combined sewer overflows (CSO). In order to improve the management efficiency of CUDS, advanced real-time control (RTC) of detention and diversion infrastructures in the sewer systems has been proven to contribute to reducing the CSO volumes. This work considers the integrated RTC of sewer network and WWTPs based on model predictive control (MPC) and taking into account the water quality as well as quantity, with the objective of minimizing the environmental impact of CSO on receiving waters. The control approach is validated using a real pilot Badalona sewer network in Spain. The first results, discussion and conclusions are also provided.Peer ReviewedPostprint (author's final draft

Unidad residencial en El Cabañal

Dentro de la parcela se proyectan dos bloques de viviendas de distinta tipología, una guardería y una cafetería. El proyecto genera una gran plaza en la que conviven pavimento duro y zonas verdes. En cuanto a los dos bloques de viviendas, uno es de mayor tamaño, con 8 alturas y con actividades comerciales en los bajos; en el otro bloque de menor altura se deja exenta la planta baja permitiendo el paso de peatones a través del bloque. La guardería y la cafetería hacen la función de nexo entre lo público y lo residencial, utilizando piezas ligeras y transparentes.Miragall Meseguer, J. (2011). Unidad residencial en El Cabañal. http://hdl.handle.net/10251/34871.Archivo delegad

Approximating fault detection linear interval observers using -order interval predictors

"This is the peer reviewed version of the following article:Meseguer, J., Puig, V., and Escobet, T. (2017) Approximating fault detection linear interval observers using ¿-order interval predictors. Int. J. Adapt. Control Signal Process., 31: 1040–1060., which has been published in final form at https://doi.org/10.1002/acs.2746. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."Interval observers can be described by an autoregressive-moving-average model while ¿-order interval predictors by a moving-average model. Because an autoregressive-moving-average (ARMA) model can be approximated by a moving-average model, this allows establishing the equivalence between interval observers and interval predictors. This paper deals with the fault detection application and focuses on the equivalence between the ¿-orderintervalpredictorsand the interval observers from the point of view of the fault detection performance. The paper also proves that it is possible to obtain an equivalent ¿ - order interval predictor for a given interval observer with the same fault detection properties by the appropriate selection of the ¿ - order. A condition for selecting the minimal order that provides the ¿ - order interval predictor equivalent to a given interval observer is derived. Moreover, because the wrapping effect could be avoided by tuning properly the interval observer, we can find an equivalent ¿ - order interval predictor such that it also avoids the wrapping effect. Finally, an example based on an industrial servo actuator will be used to illustrate the derived results. Copyright © 2016 John Wiley & Sons, Ltd.Peer ReviewedPostprint (author's final draft

Pumps condition assessment in water distribution networks

Postprint (published version

A feedback simulation procedure for real-time control of urban drainage systems

This paper presents a feedback simulation procedure for the real-time control (RTC) of urban drainage systems (UDS) with the aim of providing accurate state evolutions to the RTC optimizer as well as illustrating the optimization performance in a virtual reality. Model predictive control (MPC) has been implemented to generate optimal solutions for the multiple objectives of UDS using a simplified conceptual model. A high-fidelity simulator InfoWorks ICM is used to carry on the simulation based on a high level detailed model of a UDS. Communication between optimizer and simulator is realized in a feedback manner, from which both the state dynamics and the optimal solutions have been implemented through realistic demonstrations. In order to validate the proposed procedure, a real pilot based on Badalona UDS has been applied as the case study.Peer ReviewedPostprint (author's final draft

Fault-tolerant model predictive control applied to integrated urban drainage and sanitation systems for environmental protection

This paper presents a FTC framework for a Real-Time MPC-based Controller applied to Integrated Urban Drainage and Sanitation Systems (UDSSs) which was proposed in the LIFE EFFIDRAIN project. This project deals with the pollution of surface waters due to CSOs and overflows from UDSSs during wet weather. The main purpose of the proposed FTC framework is to preserve as much as possible, the performance of the MPC-based Controller in terms of operation objectives when anomalies affecting the integrated ICT elements (sensors and actuators) occurs. The performance of the FTC controller has been tested using a realistic case of study.Peer ReviewedPostprint (author's final draft

E‐learning y desarrollo de competencias: la micronización de contenidos en economía y empresa

Entre las nuevas necesidades de formación y de aprendizaje surgidas de la definición de un Espacio Europeo de Enseñanza Superior (EEES) común, destaca la necesidad de profundizar en una mejor enseñanza científica y técnica, así como en el desarrollo de competencias genéricas y transversales de cara a un aprendizaje permanente a lo largo de la vida. De acuerdo con este marco general, en este artículo se define una metodología educativa adaptada a la formación virtual, y aplicada a la enseñanza y aprendizaje en el área de conocimiento de economía y empresa, que permita la integración de las principales competencias genéricas al currículum docente. Así, después de establecer en la primera parte del artículo cuales son estas competencias, que clasificamos en instrumentales, personales, sistémicas y en transferibles, se propone una metodología que permita encajarlas en cada uno de los objetivos de aprendizaje propuestos para los grados de economía y empresa. La micronización de los contenidos, es decir, la división sucesiva de contenidos en unidades menores, permitirá en la parte central del artículo definir lo que llamamos el mapa de competencias y de contenidos para la formación virtual, concretando en donde se trabaja una u otra competencia. Se definen estas unidades menores, producto de la micronización de contenidos, de forma que contemplen la posibilidad de que haya diferentes niveles de dificultad, y diferentes niveles de profundidad. Asimismo se propone que contengan ejercicios y actividades, elementos que permitan la evaluación de su aprendizaje, y la relación de contenidos relacionados. En la parte final del artículo, se desarrolla una aplicación práctica de la metodología propuesta alrededor de un objetivo de formación concreto en economía y empresa, como es el estudio de las estructuras de mercado. Esta implementación, nos ha permitido crear un ejemplo de un nuevo material de aprendizaje, identificando tanto los diferentes niveles de dificultad como de profundidad, así como aquellas competencias concretas que se desarrollan con su trabajo.One of the formation and learning priorities that has appeared from the definition of the European Space for Higher Education, is the need to study in depth a better scientific and technical education, as well as the development of generic and transversal competences based on the lifelong learning. In this article an educative methodology adapted to e‐learning is defined and applied to the area of economic and business knowledge, which allows the integration of the main generic competences to the educational curriculum. After setting these competences and its classification on the first part of the article, we propose a methodology that allows fitting each of them with the learning objectives proposed for the Economy and Business Degrees. Micronization or the successive division of contents in smaller units will allow us to define the map of competences and contents for e‐learning, indicating where each competence is developed. These small units, outcomes of the micronization, are defined in order to consider different levels of difficulty and depth. It also contains exercises and activities, elements that permit us to relate contents and evaluate its learning and performance. Finally, a practical application of the proposed methodology about a formative objective is developed, as it is the study of the market structures. This implementation has permitted us to create an example of a new learning material, identifying the different levels of difficulty and depth, as well as the development of competences

On The Structure Of The Objective Function For A Pressure Sensor Placement Optimizing Methodology Based On Genetic Algorithms Applied To Model-Based Leakage Localization In Distribution Water Networks

Real-time monitoring of distribution water networks relies on the deployment of sensors and the availability of their measurements in order to predict the system state and assess its performance. A meaningful application of this methodology is the detection and localization of leaks using model-based approaches. Since the number of sensors is limited because of budget constraints, it is important to place these devices in locations where the effectiveness of the leakage diagnosis is maximized. Finding the best sensor distribution is a global optimization problem defined by an objective function that might depend on different factors. Therefore, deriving the correct structure of such function is a crucial step as a wrong definition would lead towards a confusing optimal solution affecting negatively the monitoring performance. In general, sensor placement optimization methods describe objective functions using factors related to the amount of undistinguishable leaks. More concretely, the methods first compute groups of locations where leaks cannot be differentiated and then maximize this number of groups or minimize their size. In this paper, additional factors are presented to accurately represent the requirements of the leak diagnosis phase. These include other statistical figures related to the size of groups, geographical characteristics like the group’s extension area, levels of sensitivity that indicate whether a location is more or less sensible to pressure changes, etc. The objective of this study is to review several factors in order to comprehend their behaviour and justify or discard them for the objective function. The indicators under study are evaluated by means of a cross-correlation analysis applied to the scenario defined by the District Metered Area of the Barcelona water distribution. Results indicate the existence of different independency levels between the indicators that allow us to select those with less redundancy