Simplified Interval Observer Scheme: A New Approach for Fault Diagnosis in Instruments

There are different schemes based on observers to detect and isolate faults in dynamic processes. In the case of fault diagnosis in instruments (FDI) there are different diagnosis schemes based on the number of observers: the Simplified Observer Scheme (SOS) only requires one observer, uses all the inputs and only one output, detecting faults in one detector; the Dedicated Observer Scheme (DOS), which again uses all the inputs and just one output, but this time there is a bank of observers capable of locating multiple faults in sensors, and the Generalized Observer Scheme (GOS) which involves a reduced bank of observers, where each observer uses all the inputs and m-1 outputs, and allows the localization of unique faults. This work proposes a new scheme named Simplified Interval Observer SIOS-FDI, which does not requires the measurement of any input and just with just one output allows the detection of unique faults in sensors and because it does not require any input, it simplifies in an important way the diagnosis of faults in processes in which it is difficult to measure all the inputs, as in the case of biologic reactors

Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?

<p>Abstract</p> <p>Background</p> <p>A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41°S to 56°S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chiloé Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillín or Southern river otter (<it>Lontra provocax</it>).</p> <p>Results</p> <p>We examined mtDNA sequences of the control region, ND5 and Cytochrome-b (2151 bp in total) in 75 samples of <it>L. provocax </it>from 21 locations in river and marine habitats. Phylogenetic analysis illustrates two main divergent clades for <it>L. provocax </it>in continental freshwater habitat. A highly diverse clade was represented by haplotypes from the marine habitat of the Southern Fjords and Channels (SFC) region (43°38' to 53°08'S), whereas only one of these haplotypes was paraphyletic and associated with northern river haplotypes.</p> <p>Conclusions</p> <p>Our data support the hypothesis of the persistence of <it>L. provocax </it>in western Patagonia, south of the ice sheet limit, during last glacial maximum (41°S latitude). This limit also corresponds to a strong environmental change, which might have spurred <it>L. provocax </it>differentiation between the two environments.</p

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

Representación De Sistemas No Lineales Y Diagnóstico De Fallas Basado En Un Enfoque Multi-Modelos

In this article are developed a method for the representation of nonlinear systems as well as a scheme of fault diagnosis, both use a multi-model approach. The dynamic behavior of the system is described using different points of operation for every linear time invariant model. For every model a decoupled Kalman filter of faults is used. This allows the creation of a bank of residuals to estimate the robust weighting functions. This bank is directly linked to a scheme for detecting, isolating and estimating faults in order to improve its effectiveness. A simulation example to test the performance of the developed method is presented.En este artículo se desarrolla un método para la representación de sistemas no lineales, así como un esquema de diagnóstico de fallas; en donde ambos utilizan un enfoque multi-modelos. El comportamiento dinámico del sistema se describe mediante el uso de diferentes puntos de operación por cada modelo lineal invariante en el tiempo. Por cada modelo un filtro de Kalman desacoplado de fallas es utilizado. Esto permite la generación de un banco de residuos con la finalidad de estimar funciones de ponderación robusta a fallas. Estas últimas se enlazan directamente al esquema de detección, localización y estimación de fallas con objeto de mejorar su eficacia. Finalmente, se realiza un ejemplo de simulación a fin de probar el desempeño del método desarrollado

Diagnóstico de fallas basado en un filtro desacoplado para sistemas no lineales representados por un enfoque multi-modelos

In this article, a fault detection and diagnosis method is developed for nonlinear systems described by multimodels approach. The main contribution consists in the detection, isolation and estimation of faults for the nonlinear systems using a faultdecoupled adaptive filter. Based on the assumption that the dynamic behavior of the process is described by a multimodel approach around different operating points, a set of residuals is established in order to generate weighting functions robust to faults. These robust weighting functions are directly linked to the adaptive filter effectiveness which provides multiple fault magnitude estimations for the whole operating range of the system. Stability conditions of the adaptive filter are studied and its performance is tested using a threetank hydraulic system.En este artículo se presenta el desarrollo de un método de diagnóstico de fallas para sistemas no lineales representado por el enfoque de múltiples modelos. La principal contribución consiste en el diseño de un esquema de diagnóstico de fallas (FDD) a través de un filtro adaptativo desacoplado de fallas. El comportamiento del sistema está dado mediante múltiples modelos lineales alrededor de diferentes puntos de operación. Los residuos se establecen de tal manera que permiten estimar funciones de activación robustas a fallas. El filtro adaptivo diseñado permite la detección, localización y estimación de fallas múltiples o simultáneas. Las condiciones de estabilidad del filtro son estudiadas a través de LMI (Linear Matrix Inequality). El desempeño del esquema propuesto se valida en un sistema de tres tanque

Experimental validation of a high-gain observer for composition estimation in an ethanol-water distillation column

International audienceIn this paper a high-gain observer used to estimate the product compositions in a distillation column for a non-ideal mixture (ethanol-water) through the tray temperature measurements is presented. The design of this observer is based on a simplified mathematical model. One of the main advantages of this observer is its constant gain, therefore its tuning depends only on choosing a few constant parameters satisfying some simple algebraic inequalities. The effectiveness of the proposed method is demonstrated through on-line experiments in a distillation pilot plant

Nonlinear continuous-discrete observer. Application to distillation columns

Accessible ici : http://www.ijicic.org/ijicic-10-09060.pdfInternational audienceIn this paper, the composition estimation for the light component in a dis-tillation column is performed experimentally by a continuous-discrete observer. Thisobserver is an extension of a continuous-time constant-gain observer developed for sys-tems having a triangular form. The constant gain allows an easy tuning of the observerand makes it suitable for its implementation in on-line applications. The main advan-tage of the continuous-discrete approach is to increase the sampling time of the observer.This feature is suitable for systems with slow dynamics. The proposed observer is usedto estimate experimentally the molar fractions for a binary mixture (Ethanol-Water) ina distillation column. The estimates performed for the continuous-discrete observer areacceptable using long sampling times appropriated for the distillation proces