Control of fluid flows and other systems governed by partial differential-algebraic equations

The motion of fluids, such as air or water, is central to many engineering systems of significant economic and environmental importance. Examples range from air/fuel mixing in combustion engines to turbulence induced noise and fatigue on aircraft. Recent advances in novel sensor/actuator technologies have raised the intriguing prospect of actively sensing and manipulating the motion of the fluid within these systems, making them ripe for feedback control, provided a suitable control model exists. Unfortunately, the models for many of these systems are described by nonlinear, partial differential-algebraic equations for which few, if any, controller synthesis techniques exist. In stark contrast, the majority of established control theory assumes plant models of finite (and typically small) state dimension, expressed as a linear system of ordinary differential equations. Therefore, this thesis explores the problem of how to apply the mainstream tools of control theory to the class of systems described by partial differential-algebraic equations, that are either linear, or for which a linear approximation is valid. The problems of control system design for infinite-dimensional and algebraically constrained systems are treated separately in this thesis. With respect to the former, a new method is presented that enables the computation of a bound on the n-gap between a discretisation of a spatially distributed plant, and the plant itself, by exploiting the convergence rate of the v-gap metric between low-order models of successively finer spatial resolution. This bound informs the design, on loworder models, of H[infinity] loop-shaping controllers that are guaranteed to robustly stabilise the actual plant. An example is presented on a one-dimensional heat equation. Controller/estimator synthesis is then discussed for finite-dimensional systems containing algebraic, as well as differential equations. In the case of fluid flows, algebraic constraints typically arise from incompressibility and the application of boundary conditions. A numerical algorithm is presented, suitable for the semi-discrete linearised Navier-Stokes equations, that decouples the differential and algebraic parts of the system, enabling application of standard control theory without the need for velocity-vorticity type methods. This algorithm is demonstrated firstly on a simple electrical circuit, and secondly on the highly non-trivial problem of flow-field estimation in the transient growth region of a flat-plate boundary layer, using only wall shear measurements. These separate strands are woven together in the penultimate chapter, where a transient energy controller is designed for a channel-flow system, using wall mounted sensors and actuators

University Textbooks: An Acceptable Conflict of Interest?

Étude de cas / Case studyCette étude de cas examine les conflits d'intérêts qui surviennent lorsque les professeurs d'université utilisent leurs propres manuels comme lectures obligatoires dans leurs cours.This case study examines the conflicts of interest that arise when university professors use as required course readings their own textbooks

Somatic Cell Therapy: A Genetic Rescue for a Tattered Immune System?

Étude de cas / Case studyLe cas de M. Andrew Gobea, le premier enfant à recevoir une thérapie génique expérimentale pour le déficience immunitaire combinée sévère (DICS), et une réflexion sur les implications éthiques associées à la recherche en thérapie génique.The case of Andrew Gobea, the first child to receive experimental gene therapy for severe combined immunodeficiency (SCID), and a reflection on the associated ethical implications of gene therapy research

Canadian Bioethics Research and Scholarship: A Need for Explicit Leadership and Support by Research Funders

La tribune de l'éditeur / Editor's Soapbo

Academics are weird

BrynStormingOn being neurodiverse or differentÊtre neurodivers ou differen

Hobbies are good, guilt is bad

BrynStormingFinding balance in academic life is a challengeTrouver un équilibre dans la vie universitaire est un déf

BioéthiqueOnline: Towards a Bilingual (English-French) Bioethics Community / Vers une communauté bilingue (anglais-français) en bioéthique

Éditorial / Editoria

Choosing Thesis Juries: The Costs of Taking a Strict Line on Conflicts of Interest

Étude de cas / Case studyCette étude de cas examine les conflits d'intérêts (CI) qui peuvent survenir lors de la sélection des membres du jury pour évaluer une thèse de doctorat et les coûts (temps, personnel, expertise) associés aux tentatives d'éviter les CI.This case study examines the conflicts of interest (COI) that can arise in the selection of jury members to evaluate a PhD thesis, and the costs (time, personnel, expertise) associated with trying to avoid COI

Conflits d’intérêts au sein de l’université : politiques et pratiques

[À l'origine dans / Was originally part of : ESPUM - Dép. médecine sociale et préventive - Travaux et publications]IRS

The path less travelled

BrynStormingInterdisciplinarity involves getting lost to find your directionL'interdisciplinarité s’implique de se perdre pour trouver sa voi