The work concerns the "observability problem"--the reconstruction of a dynamic process's full state from a partially measured state-- for nonlinear dynamic systems. The Extended Kalman Filter (EKF) is a widely-used observer for such nonlinear systems. However it suffers from a lack of theoretical justifications and displays poor performance when the estimated state is far from the real state, e.g. due to large perturbations, a poor initial state estimate, etc. . . We propose a solution to these problems, the Adaptive High-Gain (EKF). Observability theory reveals the existence of special representations characterizing nonlinear systems having the observability property. Such representations are called observability normal forms. A EKF variant based on the usage of a single scalar parameter, combined with an observability normal form, leads to an observer, the High-Gain EKF, with improved performance when the estimated state is far from the actual state. Its convergence for any initial estimated state is proven. Unfortunately, and contrary to the EKF, this latter observer is very sensitive to measurement noise. Our observer combines the behaviors of the EKF and of the high-gain EKF. Our aim is to take advantage of both efficiency with respect to noise smoothing and reactivity to large estimation errors. In order to achieve this, the parameter that is the heart of the high-gain technique is made adaptive. Voila, the Adaptive High-Gain EKF. A measure of the quality of the estimation is needed in order to drive the adaptation. We propose such an index and prove the relevance of its usage. We provide a proof of convergence for the resulting observer, and the final algorithm is demonstrated via both simulations and a real-time implementation. Finally, extensions to multiple output and to continuous-discrete systems are given.

L'observateur est un outil essentiel pour accéder à l'information, non mesurable directement, d'un système dynamique. Dans le cas des systèmes non linéaires, il y a une grande carence concernant la synthèse d'observateur. Motivée par l'absence d'une solution générique, cette thèse élargit la classe des systèmes non linéaires pour lesquels on peut appliquer les observateurs connus. Dans l'approche adoptée, le système non linéaire est transformé à travers un changement de coordonnées sous forme normale d'observabilité qui a une structure adéquate à la synthèse d'observateurs. Les difficultés liées aux conditions d'existence d'un changement de coordonnées sont mises en évidence et des solutions sont proposées. Par conséquent, la classe des systèmes non linéaires qui peuvent se mettre sous une forme normale d'observabilité est élargie. Dans un premier temps, nous avons proposé une forme normale d'observabilité étendue dépendante de la sortie en augmentant l'espace d'état par des variables auxiliaires. Ainsi, nous avons établi les conditions nécessaires et suffisantes à l'existence d’un changement de coordonnées permettant d’obtenir une telle forme. En outre, nous avons proposé, pour certains modèles, des procédures heuristiques pour la mise sous forme normale d'observabilité étendue dépendante de la sortie. Dans un deuxième temps, nous avons traité la mise sous forme normale d'observabilité d'un système non linéaire partiellement observable. Enfin, nous avons abordé la transformation d'une classe spéciale de systèmes non linéaires sous la forme normale d'observabilité réduite. L'efficacité et l'intérêt des méthodes développées sont établis au travers de plusieurs applications. / Observer is an essential means to access to no-measurable information of a dynamical system. In the case of nonlinear systems, there is a great deficiency concerning the observer design theory. Motivated by the lack of a generic solution to observer design, this thesis enlarges the class of nonlinear systems which admit a standard observer. Using a geometrical approach, the considered nonlinear systems are transformed through a change of coordinates into observer form, which has an adequate structure to the observer design. The difficulties related to the conditions on the existence of such a change of coordinates are highlighted and solutions are proposed. Therefore, the class of nonlinear systems which can be transformed under an observer form is expanded. Firstly, we proposed an extended output depending observer form which does not preserve the size of the original state space and we established the sufficient conditions for the existence of a change of coordinates enabling to construct the proposed form. Moreover, we proposed a heuristic procedure to construct the extended output depending observer form of some models. Secondly, we dealt with the observer form for some partially observable nonlinear systems. Finally, we discussed the transformation into the reduced observer form for a class of nonlinear systems. The efficiency and interest of the developed methods is established through several applications.

La chirurgie minimalement invasive est un domaine de recherche très actif puisqu’elle permet d’envisagerdes thérapies ciblées et des diagnostics in situ tout en minimisant traumatismes, effets secondaires et tempsde convalescence. En particulier, l’utilisation de systèmes miniaturisés actionnés à distance ouvre la voie àune navigation dans le système cardiovasculaire, permettant ainsi le ciblage et l’intervention sur zones dif-ficilement accessibles du corps humain. L’objectif de cette thèse est de proposer i) un état de l’art sur lamodélisation des forces s’exerçant sur un ou plusieurs microrobots naviguant dans des vaisseaux sanguins,ii) des représentations d’état exploitables à des fins de commande et d’observation, iii) différentes synthèsesde lois de commande pour stabiliser un ou plusieurs microrobots le long d’une trajectoire de référence, iv)des observateurs d’état pour reconstruire les états non mesurables du système. Un microrobot magnétiquenaviguant dans un vaisseau sanguin subit la force de traînée, les forces surfaciques, de contact, d’interactionmagnétique, et son poids apparent. Son actionnement est assuré par l’application de champs ou de gradientsde champ magnétiques, et sa localisation est assurée par un imageur médical. La dynamique du ou desmicrorobots (système réduit) est sous forme d’état non linéaire affine en la commande avec dérive, et dé-pend de plusieurs paramètres physiologiques incertains, en particulier de la vitesse du sang, qui est difficileà mesurer. La dynamique du flux sanguin (système fluidique) est alors modélisée sous forme d’une repré-sentation d’état autonome, combinée avec le système réduit pour aboutir au système étendu. L’objectif decommande est de stabiliser les états du système réduit le long d’une trajectoire de référence. Une commandestabilisante est synthétisée par backstepping, mais elle n’est pas utilisable en l’état. Des observateurs baséssur le théorème de la valeur moyenne et sur une immersion sont synthétisés respectivement dans le cas oùla pulsation cardiaque est connue ou non. La stabilité du retour de sortie est alors démontrée. La stabilitéet la robustesse aux bruits de mesure, aux incertitudes paramétriques, et aux erreurs de modélisation desapproches proposées sont alors illustrées par des simulations. / Minimally invasive surgery is an active research area since such systems have the potential to perform complex surgical procedures such as targeted therapies or in situ diagnosis, while minimizing trauma, side effects and recovery time. Miniaturized systems magnetically propelled by remote actuation can achieve swimming through the blood vessels network in order to provide targeted therapy, even for hard-to-reach human organs. This PhD thesis aims at addressing i) a review on the modeling of microrobots immersed in blood vessels, ii) a classification of the state space forms of such systems, iii) the synthesis of state feedbacks ensuring the stabilization of the microrobots along a reference trajectory, iv) the synthesis of observers to rebuild the unmeasured state variables. Magnetic microrobots swimming in a blood vessel face the hydrodynamic drag, surfacic and contact forces, magnetic interactions, and their apparent weight. These untethered robots are actuated by magnetic fields or magnetic gradients generation, and their localization is ensured by a medical imager. The microrobots dynamics (the so-called reduced system) lead to a nonlinear affine control subsystem with drift, and exhibits many uncertain physiological parameters, such as the blood velocity which can hardly be measured. The blood flow dynamics (the so-called fluidic system) are then modeled as an autonomous subsystem. These two subsystems result in an extended system describing the whole (robot and fluid) dynamics. The control objective is to stabilize the state of the reduced system along a reference trajectory, which is performed by an adaptive backstepping synthesis. Yet the full state is not accessible. We then synthesize either MVT or immersion based observers for the extended system, when the blood pulsation is either known or not. The output feedback stability is then proved. The stability and robustness to output noise, parametric uncertainty, and modeling errors are then illustrated by simulations.

In order to reduce the cost of the current switched resonant power converters, a state observer is introduced to provide the controller with the required information for the effective switching of the converter without the need of expensive sensory inputs from the resonant circuit. This Master's thesis investigates the usage of Matlab/Simulink and Xilinx System Generator as an implementation tool for Field Programmable Gate Array (FPGA) development of the Observer Model. The main aim is to keep the model size to a minimum while keeping the error within a reasonable range, allowing the observer to converge.

Linear switched reluctance motor (LSRM) drives are investigated and proved as an alternative actuator for vertical linear transportation applications such as a linear elevator. A one-tenth scaled prototype elevator focused on a home elevator with LSRMs is designed and extensive experimental correlation is presented for the first time. The proposed LSRM has twin stators and a set of translator poles without back-iron. The translators are placed between the two stators. The design procedures and features of the LSRM and the prototype elevator are described. The designed LSRM is validated through a finite element analysis (FEA) and experimental measurements. Furthermore, a control strategy for the prototype elevator is introduced consisting of four control loops, viz., current, force, velocity, and position feedback control loops. For force control, a novel force distribution function (FDF) is proposed and compared with conventional FDFs. A trapezoidal velocity profile is introduced to control vertical travel position smoothly during the elevator's ascent, descent, and halt operations. Conventional proportional plus integral (PI) controller is used for the current and velocity control loops and their designs are described. The proposed control strategy is dynamically simulated and experimentally correlated. Analytical and experimental results of this research prove that LSRMs are one of the strong candidates for ropeless linear elevator applications. However, the proposed FDF is assuming that the feedback current signals are ideal currents indicating actual phase currents without any measurement disturbances mainly arising from sensor noise, DC-link voltage ripple, measurement offset, and variations in the plant model. Meanwhile, real control systems in industry have measurement disturbance problems. Phase current corrupted by measurement disturbances increases torque or force ripple, acoustic noise and EMI. Therefore, this dissertation also presents a novel current control method to suppress measurement disturbances without extra hardware. The controller is based on an extended state observer (ESO) and a nonlinear P controller (NLP). The proposed method does not require an accurate mathematical model of system and can be implemented on a low-cost DSP controller. The proposed ESO is exploited to estimate the measurement disturbances on measured phase currents, and the proposed NLP compensates for the measurement disturbances estimated by the ESO. The performance of the proposed current control is validated through extensive dynamic simulations and experiments. Moreover, this rejection of measurement disturbances results in a reduction of force ripple and acoustic noise. Due to superior and robust current control performance, it is believed that the proposed method can be successfully applied into other motor drive systems to suppress measurement disturbances with the same promising results without extra hardware. / Ph. D.

Work-related musculoskeletal disorders are associated with high costs and it is essential to prevent them. Occupational Health Services(OHS) provide expert services regarding work environment, health and rehabilitation of work related disorders. Risk assessments of the work environment can be an initial step for preventive measures, and ergonomists can be assigned by clients to assess exposures in the work environment. For such assignments different tools can be used. The aim of this thesis was to explore prerequisites, processes and practices of OHS consultants in Sweden within the domain of primary prevention of work-related musculoskeletal disorders. This was explored through the work of ergonomists in their role of assessing ergonomics risks. The research methodology was both quantitative and qualitative. Data collection includes a web questionnaire, semi-structured interviews and inter- and intra-observer reliability tests. The results shows that ergonomics risk assessments were most commonly initiated reactively and a systematic work methodology for the risk assessment process was often lacking. Swedish ergonomists used only a few standardized tools for risk assessment. The Ergonomics provision from the Swedish Work Environment Authority, AFS-98, was widely used, but other observation-based tools were used far less often. Ergonomics risks were often assessed solely by means of observation, based on ergonomists’ knowledge and experience. The results also pointed to that that the reliability was not acceptable when risk assessment was performed without any standardized tool. Furthermore, the results point to that support from the OHS organizations is an important prerequisite for ergonomists to work with primary prevention. Further, opportunities for specialization within a specific industry sector seem to facilitate ergonomic interventions. It is also important to have close relationships with clients and to make them aware about ergonomists competence. Conclusively, this thesis identifies a numbers of areas in which OHS must develop to improve primary preventive services regarding work environment. / <p>QC 20170127</p>

Chronic liver disease is a worldwide health problem, and hepatic fibrosis (HF) is one of the hallmarks of the disease. Pathology diagnosis of HF is based on textural change in the liver as a lobular collagen network that develops within portal triads. The scale of collagen lobules is characteristically on order of 1mm, which close to the resolution limit of in vivo Gd-enhanced MRI. In this work the methods to collect training and testing images for a Hotelling observer are covered. An observer based on local texture analysis is trained and tested using wet-tissue phantoms. The technique is used to optimize the MRI sequence based on task performance. The final method developed is a two stage model observer to classify fibrotic and healthy tissue in both phantoms and in vivo MRI images. The first stage observer tests for the presence of local texture. Test statistics from the first observer are used to train the second stage observer to globally sample the local observer results. A decision of the disease class is made for an entire MRI image slice using test statistics collected from the second observer. The techniques are tested on wet-tissue phantoms and in vivo clinical patient data.

In pneumatic pressure control applications the influence of tubes that connect the valve with the control volume ist mainly neglected. This can lead to stability and robustness issues and limit either control performance or tube length. Modeling and considering tube behavior in controller design procedure allows longer tubes while maintaining the required performance and robustness properties without need for manual tuning. The author\'s previously published Simplified Fluid Transmission Line Model and the proposed model-based controller design enable the specification of a desired pressure trajectory in the control volume while the pressure sensor is mounted directly at the valve. Thus wiring effort is reduced as well as cost and the chance of cable break or sensor disturbance. In order to validate the simulated results the proposed control scheme is implemented on a real-time system and compared to a state-of-the-art pressure regulating valve

This dissertation sets out to explore the animal presence in the novels of contemporary French writer Michel Houellebecq. Focusing on this often overlooked aspect in the growing number of publications dedicated to Houellebecq’s literary production, this study argues that the presence of animals is central to understanding how his novels are structured around borders between not only animals and humans but also between humans themselves. By pitting animals against humans the novels simultaneously show how these borders are created within the narratives only to be repeatedly broken down and/or transgressed. Whereas in previous research a posthumanvision in Houellebecq’s works has been largely attributed to the theme of a technological surpassing of the human, this study advances the idea that animals constitute an inherent part of Houellebecq’s questioning of an anthropocentric worldview. The first chapter of the thesis, which lays the foundation for the study, explores how descriptions structure two major ways in which animals are present: either as a backdrop setting where the characters, while trying to maintain the border between themselves and animals, are transformed into observers of animals in their natural habitat, or as metaphors used to describe appearances and seemingly unwanted personality traits of some of the characters. The second chapter expands on the idea of a frontier between animals and humans but contrary to the previous chapter it studies the porosity of these borders by showing how humans and animals are depicted and narrated in similar ways. Drawing on the theories of Giorgio Agamben, Dominique Lestel and Tristan Garcia the study concludes by proposing to read Houellebecq’s novels both as a form of life stories relating a common history between animals and humans and as an attempt to highlight the untenable project of maintaining an anthropocentric worldview.

Baigiamajame darbe tiriamas dažninės asinchroninės pavaros greičio stebiklis ir charakteristikos. Įvade yra išnagrinėti greičio stebiklio panaudojimo privalumai. Aptarta dažnio keitiklių svarba asinchroninių variklių valdyme. Analitinėje dalyje nagrinėjamas dažnio keitiklių veikimo principas bei aptariamas dažninių elektros pavarų jėgos grandinių schemos. Aptariami vektorinio ir skaliarinio valdymo privalumai bei trūkumai. Pateikiami pagrindiniai greičio jutikliai bei jų trūkumai ir privalumai. Projektinėje dalyje pateiktas asinchroninio variklio matematinis modelis nejudančioje koordinačių sistemoje bei dažninės pavaros skaliarinio valdymo modelis. Išnagrinėti du greičio stebiklių modeliai. Tiriamojoje dalyje pateikti greičio stebikių modeliai ir dinaminės charakteristikos. / The final project presents the AC induction motor drive control methods and characteristics. In the preface of this project the frequency controlled electric drives and the importance of speed observer are described. In the analytic part frequency controlled electric drives power circuits, speed measuaring and observer operational principle are described. The field oriented or vector and V/Hz or scalar control is analyzed. In the design part the AC induction motor drive mathematical model in stationary reference frame is presented and AC drive scalar control method is considered. Two types of speed observer models are elaborated. In the investigation part of the project the dynamic characteristics of frequency controlled drive and speed observers are presented.