Observer-based monitoring of Hybrid Dynamical Systems

Cette thèse s’intéresse à la détection et la localisation de défaillances pour des Systèmes Dynamiques Hybrides (SDH), en utilisant des indicateurs de défauts, appelés résidus. Une méthodologie par observateur hybride utilisant deux modules d'observation est proposée : un module dédié à l’identification du mode actif, permettant la détection des défauts discrets (défauts entraînant un changement de mode de fonctionnement) et l’autre module réalisant l’estimation d’état continu, permettant la détection et la localisation des défaillances des capteurs et actionneurs. Dans le cas réel, les systèmes se trouvent dans un environnement bruité. Une méthode d’évaluation basée sur la norme des résidus est proposée afin de détecter le mode actif en présence de ces perturbations. Une méthode de placement de pôle classique ainsi qu’une technique utilisant des fonctions de Lyapunov multiples sont étudiées. Des observateurs à entrée inconnue (UIO : Unknown Input Observers) sont conçus pour générer des résidus sensibles aux défauts et robustes aux perturbations afin de répondre au Problème Fondamental de Génération des Résidus (PFGR). Une analyse de la robustesse/sensibilité sous une formulation LMI est présentée. Afin de garantir la détection des changements de modes et donc des défauts de type « discrets », une condition nécessaire de discernabilité entre modes est proposée. Une méthodologie de surveillance utilisant des graphes de comportements normaux et défaillants est enfin proposée afin de minimiser le nombre de résidus calculés à chaque instant. Les résultats théoriques et méthodologiques de cette thèse sont illustrés sur des exemples académiques en simulation.This thesis focuses on Fault Detection and Isolation (FDI) of Hybrid Dynamical Systems (HDS) using fault indicator signals, known as residuals. A method based on hybrid observers is proposed. It uses two observation modules: a module whose aim is to identify the active mode, allowing the detection of discrete faults (faults making the system switch to a new – abnormal - operation mode) and the other module performing the continuous state estimation, allowing the sensors and actuators FDI. In the real case, the system operates in a noisy environment. An evaluation method based on the norm of the residuals (estimation errors) is proposed to detect the active mode in the presence of these disturbances. The observer design is done through a classical pole placement method and a technique using multiple Lyapunov functions to ensure the exponential convergence of the estimation of SDH in the no fault situation. Unknown Input Observers (UIO) are also designed to generate residuals which are sensitive to faults and robust to disturbances, as requested in the Fundamental Problem of Residual Generation (FPRG). The robustness / sensitivity of the residuals is studied through an LMI formulation. To ensure the detection of mode switching and therefore detect the “discrete-type” faults, a necessary condition of mode discernability (distinguishability between modes) is proposed. A FDI methodology using normal and faulty behavioral graphs is finally described whose objective is to minimize the number of residuals to be on-line calculated at each time-instant. The theoretical and methodological results of this thesis are illustrated on academic simulation examples

Surveillance par observateur des systèmes dynamique hybrides

Cette thèse s intéresse à la détection et la localisation de défaillances pour des Systèmes Dynamiques Hybrides (SDH), en utilisant des indicateurs de défauts, appelés résidus. Une méthodologie par observateur hybride utilisant deux modules d'observation est proposée : un module dédié à l identification du mode actif, permettant la détection des défauts discrets (défauts entraînant un changement de mode de fonctionnement) et l autre module réalisant l estimation d état continu, permettant la détection et la localisation des défaillances des capteurs et actionneurs. Dans le cas réel, les systèmes se trouvent dans un environnement bruité. Une méthode d évaluation basée sur la norme des résidus est proposée afin de détecter le mode actif en présence de ces perturbations. Une méthode de placement de pôle classique ainsi qu une technique utilisant des fonctions de Lyapunov multiples sont étudiées. Des observateurs à entrée inconnue (UIO : Unknown Input Observers) sont conçus pour générer des résidus sensibles aux défauts et robustes aux perturbations afin de répondre au Problème Fondamental de Génération des Résidus (PFGR). Une analyse de la robustesse/sensibilité sous une formulation LMI est présentée. Afin de garantir la détection des changements de modes et donc des défauts de type discrets , une condition nécessaire de discernabilité entre modes est proposée. Une méthodologie de surveillance utilisant des graphes de comportements normaux et défaillants est enfin proposée afin de minimiser le nombre de résidus calculés à chaque instant. Les résultats théoriques et méthodologiques de cette thèse sont illustrés sur des exemples académiques en simulation.This thesis focuses on Fault Detection and Isolation (FDI) of Hybrid Dynamical Systems (HDS) using fault indicator signals, known as residuals. A method based on hybrid observers is proposed. It uses two observation modules: a module whose aim is to identify the active mode, allowing the detection of discrete faults (faults making the system switch to a new abnormal - operation mode) and the other module performing the continuous state estimation, allowing the sensors and actuators FDI. In the real case, the system operates in a noisy environment. An evaluation method based on the norm of the residuals (estimation errors) is proposed to detect the active mode in the presence of these disturbances. The observer design is done through a classical pole placement method and a technique using multiple Lyapunov functions to ensure the exponential convergence of the estimation of SDH in the no fault situation. Unknown Input Observers (UIO) are also designed to generate residuals which are sensitive to faults and robust to disturbances, as requested in the Fundamental Problem of Residual Generation (FPRG). The robustness / sensitivity of the residuals is studied through an LMI formulation. To ensure the detection of mode switching and therefore detect the discrete-type faults, a necessary condition of mode discernability (distinguishability between modes) is proposed. A FDI methodology using normal and faulty behavioral graphs is finally described whose objective is to minimize the number of residuals to be on-line calculated at each time-instant. The theoretical and methodological results of this thesis are illustrated on academic simulation examples.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Distinguishability and Similarity between modes in Hybrid System Monitoring

International audienceThe general principle of model-based Fault Detection and Isolation (FDI) algorithms aims to compare the expected behavior of the system, given by a model, with its actual behavior, known through on-line observations. Accordingly, this paper considers Hybrid Dynamical Systems (HDS), since the behavior is determined by the interaction between continuous and discrete dynamics. The proposed FDI method is based on Luenberger observers. The resulting faults indicators allow detecting both continuous and discrete faults. The property of distinguishability will be considered to guarantee modes identification and the similarity between modes is given in order to reduce residuals calculation

Behavior graphs for hybrid systems monitoring

International audienceHybrid Dynamical Systems (HDS) constitute a wide class of common industrial applications, where the behavior is determined by the interaction between continuous and discrete dynamics, i.e. behavioral modes succession. The general principle of model-based Fault Detection and Isolation (FDI) algorithms is to compare the expected behavior of the system, given by a model, with its actual behavior, known through on-line observations. Faults in HDS may corrupt the two dynamics. In that paper, we propose to limit the set of possible mode candidates by using a priori information on the discrete evolution under normal and faulty hypothesis. Two kinds of graphs are derived from the initial hybrid model, namely Normal Behavior Graphs (NBG), Faulty Behavior Graphs (FBG). Using these graphs allows us not only to identify efficiently the actual mode but also to directly interpret (diagnose) the discrete faulty evolution in terms of faults. The whole FDI methodology is described and applied to a two tanks system example

Mode Identification and Fault Detection for Hybrid Dynamical Systems using Luenberger Observers

International audienc

Relationship Between Teacher’s and Therapist’s Evaluations on Handwriting Performance in First-grade Children

Objectives: Handwriting dysfunction may harm children’s wellbeing. Therapists and elementary school teachers help to identify and improve children’s handwriting performance. The present study aimed to assess the relationship between therapists’ assessment and teachers’ perception of handwriting performance in first graders. Methods: This cross-sectional study involved (n=31) first-grade students, aged 6-8 years from an international school in Riyadh City, Saudi Arabia. Teachers evaluated the handwriting proficiency using the Handwriting Proficiency Screening Questionnaire (HPSQ), and the explored students were rated as proficient and non-proficient hand writers. Furthermore, therapists assessed students’ handwriting proficiency using the Minnesota Handwriting Assessment (MHA) (manuscript & D’Nealian styles) scores. The Mann–Whitney U test was used to assess the differences in MHA scores between proficient and non-proficient hand writers. Moreover, Spearman’s correlation coefficient was used to assess the relationship between the scores of MHA and HPSQ. Results: There was a significant difference in all component scores of MHA (except the rate) and both writing styles between the proficient and non-proficient writers (P<0.05). There was also a significant relationship between the MHA and the HSPQ scores (P<0.05). However, further analysis of these scales’ components suggested no significant association between teachers’ and therapists’ evaluation of the handwriting speed domain. Discussion: There was a significant relationship between the teacher’s and therapist’s evaluation of handwriting performance using standardized measures. Thus, therapists should work in collaboration with teachers to identify and treat handwriting difficulties in school children

Wide Area Uniform Illumination Scheme Using LED Matrix for Optogenetic Cardiac Pacing

Control of heart rhythm is vital in the case of arrhythmia. Cardiac optogenetics is a promising technique to replace electrical stimulation in a next generation of pacemakers and defibrillators. Therefore, further research towards optimizing light delivery methods is essential. A major requirement is the uniform stimulation of all cells in the area of interest while reducing side effects such as photodamage. Here, a 2 × 2 blue (470 nm, InGaN-based) light-emitting diode (LED) optoelectronic module for uniform ex vivo cardiac muscle illumination is demonstrated. It satisfies two important requirements in optogenetics, which are high illumination homogeneity and high irradiance. CCD camera images show an average 90% homogeneity over the central illumination area of close to 38 mm2 at 1 cm distance from the light source. The module is used to perform physiological experiments on channelrhodopsin 2-expressing Langendorff-perfused mouse hearts. Successful ventricular pacing is obtained for an optical power density threshold below 2 mW/mm2 with light pulses as short as 1 ms. For 10 ms long pulses, the threshold was below 0.2 mW/mm2. The large homogeneous illumination area enabled optogenetic pacing with less than half the optical power of previous attempts with smaller areas of 2 mm2 and thus, presumably, will result in less phototoxicity