Stability analysis of coupled ordinary differential systems with a string equation: application to a drilling mechanism

Cette thèse porte sur l'analyse de stabilité de couplage entre deux systèmes, l'un de dimension finie et l'autre infinie. Ce type de systèmes apparait en physique car il est intimement lié aux modèles de structures. L'analyse générique de tels systèmes est complexe à cause des natures très différentes de chacun des sous-systèmes. Ici, l'analyse est conduite en utilisant deux méthodologies. Tout d'abord, la séparation quadratique est utilisée pour traiter le côté fréquentiel de ce système couplé. L'autre méthode est basée sur la théorie de Lyapunov pour prouver la stabilité asymptotique de l'interconnexion. Tous ces résultats sont obtenus en utilisant la méthode de projection de l'état de dimension infinie sur une base polynomiale. Il est alors possible de prendre en compte le couplage entre les deux systèmes et ainsi d'obtenir des tests numériques fiables, rapides et peu conservatifs. De plus, une hiérarchie de conditions est établie dans le cas de Lyapunov. L'application au cas concret du forage pétrolier est proposée pour illustrer l'efficacité de la méthode et les nouvelles perspectives qu'elle offre. Par exemple, en utilisant la notion de stabilité pratique, nous avons montré qu'une tige de forage controlée à l'aide d'un PI est sujette à un cycle limite et qu'il est possible d'estimer son amplitude.This thesis is about the stability analysis of a coupled finite dimensional system and an infinite dimensional one. This kind of systems emerges in the physics since it is related to the modeling of structures for instance. The generic analysis of such systems is complex, mainly because of their different nature. Here, the analysis is conducted using different methodologies. First, the recent Quadratic Separation framework is used to deal with the frequency aspect of such systems. Then, a second result is derived using a Lyapunov-based argument. All the results are obtained considering the projections of the infinite dimensional state on a basis of polynomials. It is then possible to take into account the coupling between the two systems. That results in tractable and reliable numerical tests with a moderate conservatism. Moreover, a hierarchy on the stability conditions is shown in the Lyapunov case. The real application to a drilling mechanism is proposed to illustrate the efficiency of the method and it opens new perspectives. For instance, using the notion of practical stability, we show that a PI-controlled drillstring is subject to a limit cycle and that it is possible to estimate its amplitude

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A New Controller for the Acquisition and Guiding Unit for the Gemini South Telescope : New architecture and control schemes to use Power PMAC

When the Gemini Telescopes were built 20 years ago, the control architecture for the high precision requirements was the same for all systems. It consisted of VME cards, Programmable Multi Axis Con-trollers (PMAC) with specific amplifiers and a central computer. It was the state of the art. Nevertheless such an infrastructure takes up a lot of space. It is also difficult to maintain mainly because of obsoles-cence and the lack of support of the engineers who do not consider this system adapted to the control.The code, documentation and wiring were complex and not fully understood. Thus, it led the Gemini Observatory to consider the acquisition of a new controller for one of the most critical unit: the Acquisition and Guidance (A&G). To address these issues, I propose an alternative control system which will not only solve the current issues but also improve the performance. The new generation of controller from Delta Tau is more efficient, more reliable and with a high level of integration. The main concern of compatibility with the current motors and encoders of the Acquisition and Guidance has been solved by testing 27 motors out of the 29 present in the unit. Results were obtained using a test bench and mechanical systems built during the internship. A fully functional test bench has been delivered. Furthermore, a new control scheme for the backlash compensation is proposed. It consumes half the energy of the current one, is nearly two times faster and without oscillations. This will reduce the frequency of maintenance and the reliability of the unit. A cross gantry control for the skew compensation of the Science fold leads to a smarter control of the differences between the motors to prevent the mirror from breaking. Finally, an identification technique for the tilt mechanism provides more robustness and takes into account the ageing of the equipment

Stabilité et stabilisation de systèmes linéaires à l’aide d’inégalités matricielles linéaires

National audienceCet article étudie la stabilité de systèmes modélisés par une équation différentielle potentiellement non-linéaire. Après des définitions générales, le cas particulier des systèmes linéaires invariants dans le temps est étudié beaucoup plus précisément et des conditions algébriques sont énoncées pour établir sa stabilité asymptotique. L'analyse de stabilité est aussi statuée via le théorème de Lyapunov, utilisant alors des algorithmes venant de la programmation semi-définie. Tous les résultats sont rigoureusement démontrés dans les cas généraux et un exemple d'application sur la stabilité d'une nacelle est proposé et enrichi au cours de l'exposé

A New Controller for the Acquisition and Guiding Unit for the Gemini South Telescope : New architecture and control schemes to use Power PMAC

When the Gemini Telescopes were built 20 years ago, the control architecture for the high precision requirements was the same for all systems. It consisted of VME cards, Programmable Multi Axis Con-trollers (PMAC) with specific amplifiers and a central computer. It was the state of the art. Nevertheless such an infrastructure takes up a lot of space. It is also difficult to maintain mainly because of obsoles-cence and the lack of support of the engineers who do not consider this system adapted to the control.The code, documentation and wiring were complex and not fully understood. Thus, it led the Gemini Observatory to consider the acquisition of a new controller for one of the most critical unit: the Acquisition and Guidance (A&G). To address these issues, I propose an alternative control system which will not only solve the current issues but also improve the performance. The new generation of controller from Delta Tau is more efficient, more reliable and with a high level of integration. The main concern of compatibility with the current motors and encoders of the Acquisition and Guidance has been solved by testing 27 motors out of the 29 present in the unit. Results were obtained using a test bench and mechanical systems built during the internship. A fully functional test bench has been delivered. Furthermore, a new control scheme for the backlash compensation is proposed. It consumes half the energy of the current one, is nearly two times faster and without oscillations. This will reduce the frequency of maintenance and the reliability of the unit. A cross gantry control for the skew compensation of the Science fold leads to a smarter control of the differences between the motors to prevent the mirror from breaking. Finally, an identification technique for the tilt mechanism provides more robustness and takes into account the ageing of the equipment

Analyse de stabilité de systèmes différentiels ordinaires couplés avec une équation des ondes : application aux mécanismes de forage

National audienceThis thesis is about the stability analysis of a coupled finite dimensional system and an infinite dimensional one. This kind of systems emerges in the physics since it is related to the modeling of structures for instance. The generic analysis of such systems is complex, mainly because of their different nature. Here, the analysis is conducted using different methodologies. First, the recent Quadratic Separation framework is used to deal with the frequency aspect of such systems. Then, a second result is derived using a Lyapunov-based argument. All the results are obtained considering the projections of the infinite dimensional state on a basis of polynomials. It is then possible to take into account the coupling between the two systems. That results in tractable and reliable numerical tests with a moderate conservatism. Moreover, a hierarchy on the stability conditions is shown in the Lyapunov case. The real application to a drilling mechanism is proposed to illustrate the efficiency of the method and it opens new perspectives. For instance, using the notion of practical stability, we show that a PI-controlled drillstring is subject to a limit cycle and that it is possible to estimate its amplitude.Cette thèse porte sur l'analyse de stabilité de couplage entre deux systèmes, l'un de dimension finie et l'autre infinie. Ce type de systèmes apparait en physique car il est intimement lié aux modèles de structures. L'analyse générique de tels systèmes est complexe à cause des natures très différentes de chacun des sous-systèmes. Ici, l'analyse est conduite en utilisant deux méthodologies. Tout d'abord, la séparation quadratique est utilisée pour traiter le côté fréquentiel de ce système couplé. L'autre méthode est basée sur la théorie de Lyapunov pour prouver la stabilité asymptotique de l'interconnexion. Tous ces résultats sont obtenus en utilisant la méthode de projection de l'état de dimension infinie sur une base polynomiale. Il est alors possible de prendre en compte le couplage entre les deux systèmes et ainsi d'obtenir des tests numériques fiables, rapides et peu conservatifs. De plus, une hiérarchie de conditions est établie dans le cas de Lyapunov. L'application au cas concret du forage pétrolier est proposée pour illustrer l'efficacité de la méthode et les nouvelles perspectives qu'elle offre. Par exemple, en utilisant la notion de stabilité pratique, nous avons montré qu'une tige de forage controlée à l'aide d'un PI est sujette à un cycle limite et qu'il est possible d'estimer son amplitude

Analyse de stabilité de systèmes couplés - Application au forage pétrolier

National audienceThis thesis is about the stability analysis of a coupled finite dimensional system and an infinite dimensional one. This kind of systems emerges in the physics since it is related to the modeling of structures for instance. The generic analysis of such systems is complex, mainly because of their different nature. Here, the analysis is conducted using different methodologies. First, the recent Quadratic Separation framework is used to deal with the frequency aspect of such systems. Then, a second result is derived using a Lyapunov-based argument. All the results are obtained considering the projections of the infinite dimensional state on a basis of polynomials. It is then possible to take into account the coupling between the two systems. That results in tractable and reliable numerical tests with a moderate conservatism. Moreover, a hierarchy on the stability conditions is shown in the Lyapunov case.The real application to a drilling mechanism is proposed to illustrate the efficiency of the method and it opens new perspectives. For instance, using the notion of practical stability, we show that a PI-controlled drillstring is subject to a limit cycle and that it is possible to estimate its amplitude.Cette thèse porte sur l’analyse de stabilité de couplage entre deux systèmes, l’un de dimension finie et l’autre infinie. Ce type de système apparait en physique car il est intimement lié aux modèles de structures. L’analyse générique de tels systèmes est complexe à cause des natures très différentes de chacun des sous-systèmes.Ici, l’analyse est conduite en utilisant deux méthodologies. Tout d’abord, la séparation quadratique est utilisée pour traiter le côté fréquentiel de tels systèmes. L’autre méthode est basée sur la théorie de Lyapunov pour prouver la stabilité asymptotique de l’interconnexion. Tous ces résultats sont obtenus en utilisant la méthode de projection de l’état de dimension infinie sur une base polynomiale. Il est alors possible de prendre en compte le couplage entre les deux systèmes et ainsi d’obtenir des tests numériques fiables, rapides et peu conservatifs.De plus, une hiérarchie de conditions est établie dans le cas de Lyapunov. L’application au cas concret du forage pétrolier est proposée pour illustrer l’efficacité de la méthode et les nouvelles perspectives qu’elle offre. Par exemple, en utilisant la notion de stabilité pratique, nous avons montré qu’une tige de forage contrôlée à l’aide d’un PI est sujette `a un cycle limite et qu’il est possible d’estimer son amplitude

Stabilization of an unstable wave equation using an infinite dimensional dynamic controller

International audienceThis paper deals with the stabilization of an anti-stable string equation with Dirichlet actuation where the instability appears because of the uncontrolled boundary condition. Then, infinitely many unstable poles are generated and an infinite dimensional control law is therefore proposed to exponentially stabilize the system. The idea behind the choice of the controller is to extend the domain of the PDE so that the anti-damping term is compensated by a damping at the other boundary condition. Additionally, notice that the system can then be exponentially stabilized with a chosen decay-rate and is robust to uncertainties on the wave speed and the anti-damped coefficient of the wave equation, with the only use of a point-wise boundary measurement. The efficiency of this new control strategy is then compared to the backstepping approach