Modeling Switched Behavior with Hybrid Bond Graph : Application to a Tank System

Abstract Different approaches have been used in the development of system models. In addition, modeling and simulation approaches are essential for design, analysis, control, and diagnosis of complex systems. This work presents a Simulink model for systems with mixed continuous and discrete behaviors. The model simulated was developed using the bond graph methodology and we model hybrid systems using hybrid bond graphs (HBGs), that incorporates local switching functions that enable the reconfiguration of energy flow paths. This approach has been implemented as a software tool called the MOdeling and Transformation of HBGs for Simulation (MOTHS) tool suite which incorporates a model translator that create Simulink models. Simulation model of a three-tank system that includes a switching component was developed using the bond graph methodology, and MoTHS software were used to build a Simulink model of the dynamic behavior

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

contribution a la repartition dynamique des taches entre operateur et calculateur pour la supervision des procedes automatises

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

A comparison of two methods for actuators fault detection and isolation for nonlinear systems: application to a waste water treatment process

International audienc

On the Representation of Actuator Faults Diagnosis and Systems Invertibility

International audienceIn this work, the main problem considered is the detection and the isolation of the actuator fault. A new formulation of the linear system is generated to obtain the conditions of the actuator fault diagnosis. The proposed method is based on the representation of the actuator as a subsystem connected with the process system in cascade manner. The designed formulation is generated to obtain the conditions of the actuator fault detection and isolation. Detectability conditions are expressed in terms of the invertibility notions. An example and a comparative analysis with the classic formulation illustrate the performances of such approach for simple actuator fault diagnosis by using the linear model of nuclear reactor

A Comparative Analysis of Two Formulations for Actuator Faults Detection and Isolation: Application to a Waste Water Treatment Process

International audienceThe goal in many fault detection and isolation (FDI) schemes is to increase the isolation and identification speed. This paper compares two methods for FDI. The first method is based on adaptive nonlinear observer. This approach uses the model of the system and a bank of adaptive observers to generate residuals in such way to isolate the faulty actuator after detecting the fault occurrence. The second method based on interval observers. The practical domain of the value of each actuator parameter is divided into a certain number of intervals. After verifying all the intervals whether one of them contains the faulty actuator, the faulty value is identified and the corresponding fault is isolated to achieve faster isolation speed. Simulation results show the effectiveness and the difference between the two proposed detection and isolation methods using an example of the waste water treatment process described by a nonlinear system model

Détection et isolation de défauts actionneurs basées sur un modèle de l'organe de commande

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

On the integration of actuator fault detection and isolation in model based fault diagnosis

International audienceThe main goal of the Fault Detection and Isolation (FDI) is to effectively detect faults and accurately isolate them to a failed component in the shortest time possible. This capability leads to reduction in diagnostic time, therefore, increased the system availability. Also, a good inherent diagnostic of a system enhances the operating system confidence. This paper proposes a new formulation of the linear system to obtain the conditions of the actuator fault detection and isolation. We consider the actuator as a dynamic subsystem connected with the process subystem in a cascade manner and we look for the fault detectability and isolability problems. An example illustrates the performances of such interval observer approach for simple actuator fault diagnosis. In fact two mathematical models are given: a simple model for the actuator subsystem and a continuous time state-space description for the process subsystem of a speed governor for large diesel engines

System inversion actuators fault detection and isolation for linear systems: application to a nuclear reactor

International audienc