Novel control, haptic and calibration methods for teleoperated electrohydraulic servo systems

The aim of this thesis is to propose a novel control method for teleoperated electrohydraulic servo systems that implements a reliable haptic sense between the human and manipulator interaction, and an ideal position control between the manipulator and the task environment interaction. The proposed method has the characteristics of a universal technique independent of the actual control algorithm and it can be applied with other suitable control methods as a real-time control strategy. The motivation to develop this control method is the necessity for a reliable real-time controller for teleoperated electrohydraulic servo systems that provides highly accurate position control based on joystick inputs with haptic capabilities. The contribution of the research is that the proposed control method combines a directed random search method and a real-time simulation to develop an intelligent controller in which each generation of parameters is tested on-line by the real-time simulator before being applied to the real process. The controller was evaluated on a hydraulic position servo system. The simulator of the hydraulic system was built based on Markov chain Monte Carlo (MCMC) method. A Particle Swarm Optimization algorithm combined with the foraging behavior of E. coli bacteria was utilized as the directed random search engine. The control strategy allows the operator to be plugged into the work environment dynamically and kinetically. This helps to ensure the system has haptic sense with high stability, without abstracting away the dynamics of the hydraulic system. The new control algorithm provides asymptotically exact tracking of both, the position and the contact force. In addition, this research proposes a novel method for re-calibration of multi-axis force/torque sensors. The method makes several improvements to traditional methods. It can be used without dismantling the sensor from its application and it requires smaller number of standard loads for calibration. It is also more cost efficient and faster in comparison to traditional calibration methods. The proposed method was developed in response to re-calibration issues with the force sensors utilized in teleoperated systems. The new approach aimed to avoid dismantling of the sensors from their applications for applying calibration. A major complication with many manipulators is the difficulty accessing them when they operate inside a non-accessible environment; especially if those environments are harsh; such as in radioactive areas. The proposed technique is based on design of experiment methodology. It has been successfully applied to different force/torque sensors and this research presents experimental validation of use of the calibration method with one of the force sensors which method has been applied to.

Stochastic particle models: mean reversion and burgers dynamics. An application to commodity markets

The aim of this study is to propose a stochastic model for commodity markets linked with the Burgers equation from fluid dynamics. We construct a stochastic particles method for commodity markets, in which particles represent market participants. A discontinuity in the model is included through an interacting kernel equal to the Heaviside function and its link with the Burgers equation is given. The Burgers equation and the connection of this model with stochastic differential equations are also studied. Further, based on the law of large numbers, we prove the convergence, for large N, of a system of stochastic differential equations describing the evolution of the prices of N traders to a deterministic partial differential equation of Burgers type. Numerical experiments highlight the success of the new proposal in modeling some commodity markets, and this is confirmed by the ability of the model to reproduce price spikes when their effects occur in a sufficiently long period of time.

Characterizing Dynamic Optimization Benchmarks for the Comparison of Multi-Modal Tracking Algorithms

Population-based metaheuristics, such as particle swarm optimization (PSO), have been employed to solve many real-world optimization problems. Although it is of- ten sufficient to find a single solution to these problems, there does exist those cases where identifying multiple, diverse solutions can be beneficial or even required. Some of these problems are further complicated by a change in their objective function over time. This type of optimization is referred to as dynamic, multi-modal optimization. Algorithms which exploit multiple optima in a search space are identified as niching algorithms. Although numerous dynamic, niching algorithms have been developed, their performance is often measured solely on their ability to find a single, global optimum. Furthermore, the comparisons often use synthetic benchmarks whose landscape characteristics are generally limited and unknown. This thesis provides a landscape analysis of the dynamic benchmark functions commonly developed for multi-modal optimization. The benchmark analysis results reveal that the mechanisms responsible for dynamism in the current dynamic bench- marks do not significantly affect landscape features, thus suggesting a lack of representation for problems whose landscape features vary over time. This analysis is used in a comparison of current niching algorithms to identify the effects that specific landscape features have on niching performance. Two performance metrics are proposed to measure both the scalability and accuracy of the niching algorithms. The algorithm comparison results demonstrate the algorithms best suited for a variety of dynamic environments. This comparison also examines each of the algorithms in terms of their niching behaviours and analyzing the range and trade-off between scalability and accuracy when tuning the algorithms respective parameters. These results contribute to the understanding of current niching techniques as well as the problem features that ultimately dictate their success.

Vid��osurveillance intelligente pour la d��tection de chutes chez les personnes ��g��es

Les pays industrialis��s comme le Canada doivent faire face au vieillissement de leur population. En particulier, la majorit�� des personnes ��g��es, vivant �� domicile et souvent seules, font face �� des situations �� risques telles que des chutes. Dans ce contexte, la vid��osurveillance est une solution innovante qui peut leur permettre de vivre normalement dans un environnement s��curis��. L���id��e serait de placer un r��seau de cam��ras dans l���appartement de la personne pour d��tecter automatiquement une chute. En cas de probl��me, un message pourrait ��tre envoy�� suivant l���urgence aux secours ou �� la famille via une connexion internet s��curis��e. Pour un syst��me bas co��t, nous avons limit�� le nombre de cam��ras �� une seule par pi��ce ce qui nous a pouss�� �� explorer les m��thodes monoculaires de d��tection de chutes. Nous avons d���abord explor�� le probl��me d���un point de vue 2D (image) en nous int��ressant aux changements importants de la silhouette de la personne lors d���une chute. Les donn��es d���activit��s normales d���une personne ��g��e ont ��t�� mod��lis��es par un m��lange de gaussiennes nous permettant de d��tecter tout ��v��nement anormal. Notre m��thode a ��t�� valid��e �� l���aide d���une vid��oth��que de chutes simul��es et d���activit��s normales r��alistes. Cependant, une information 3D telle que la localisation de la personne par rapport �� son environnement peut ��tre tr��s int��ressante pour un syst��me d���analyse de comportement. Bien qu���il soit pr��f��rable d���utiliser un syst��me multi-cam��ras pour obtenir une information 3D, nous avons prouv�� qu���avec une seule cam��ra calibr��e, il ��tait possible de localiser une personne dans son environnement gr��ce �� sa t��te. Concr��tement, la t��te de la personne, mod��lis��e par une ellipsoide, est suivie dans la s��quence d���images �� l���aide d���un ���ltre �� particules. La pr��cision de la localisation 3D de la t��te a ��t�� ��valu��e avec une biblioth��que de s��quence vid��os contenant les vraies localisations 3D obtenues par un syst��me de capture de mouvement (Motion Capture). Un exemple d���application utilisant la trajectoire 3D de la t��te est propos��e dans le cadre de la d��tection de chutes. En conclusion, un syst��me de vid��osurveillance pour la d��tection de chutes avec une seule cam��ra par pi��ce est parfaitement envisageable. Pour r��duire au maximum les risques de fausses alarmes, une m��thode hybride combinant des informations 2D et 3D pourrait ��tre envisag��e.

Une nouvelle m��thode smoothed particle hydrodynamics : simulation des interfaces immerg��es et de la dynamique Brownienne des mol��cules avec des interactions hydrodynamiques

Dans cette th��se, nous pr��sentons une nouvelle m��thode smoothed particle hydrodynamics (SPH) pour la r��solution des ��quations de Navier-Stokes incompressibles, m��me en pr��sence des forces singuli��res. Les termes de sources singuli��res sont trait��s d'une mani��re similaire �� celle que l'on retrouve dans la m��thode Immersed Boundary (IB) de Peskin (2002) ou de la m��thode r��gularis��e de Stokeslets (Cortez, 2001). Dans notre sch��ma num��rique, nous mettons en oeuvre une m��thode de projection sans pression de second ordre inspir��e de Kim et Moin (1985). Ce sch��ma ��vite compl��tement les difficult��s qui peuvent ��tre rencontr��es avec la prescription des conditions aux fronti��res de Neumann sur la pression. Nous pr��sentons deux variantes de cette approche: l'une, Lagrangienne, qui est commun��ment utilis��e et l'autre, Eulerienne, car nous consid��rons simplement que les particules SPH sont des points de quadrature o�� les propri��t��s du fluide sont calcul��es, donc, ces points peuvent ��tre laiss��s fixes dans le temps. Notre m��thode SPH est d'abord test��e �� la r��solution du probl��me de Poiseuille bidimensionnel entre deux plaques infinies et nous effectuons une analyse d��taill��e de l'erreur des calculs. Pour ce probl��me, les r��sultats sont similaires autant lorsque les particules SPH sont libres de se d��placer que lorsqu'elles sont fixes. Nous traitons, par ailleurs, du probl��me de la dynamique d'une membrane immerg��e dans un fluide visqueux et incompressible avec notre m��thode SPH. La membrane est repr��sent��e par une spline cubique le long de laquelle la tension pr��sente dans la membrane est calcul��e et transmise au fluide environnant. Les ��quations de Navier-Stokes, avec une force singuli��re issue de la membrane sont ensuite r��solues pour d��terminer la vitesse du fluide dans lequel est immerg��e la membrane. La vitesse du fluide, ainsi obtenue, est interpol��e sur l'interface, afin de d��terminer son d��placement. Nous discutons des avantages �� maintenir les particules SPH fixes au lieu de les laisser libres de se d��placer. Nous appliquons ensuite notre m��thode SPH �� la simulation des ��coulements confin��s des solutions de polym��res non dilu��s avec une interaction hydrodynamique et des forces d'exclusion de volume. Le point de d��part de l'algorithme est le syst��me coupl�� des ��quations de Langevin pour les polym��res et le solvant (CLEPS) (voir par exemple Oono et Freed (1981) et ��ttinger et Rabin (1989)) d��crivant, dans le cas pr��sent, les dynamiques microscopiques d'une solution de polym��re en ��coulement avec une repr��sentation bille-ressort des macromol��cules. Des tests num��riques de certains ��coulements dans des canaux bidimensionnels r��v��lent que l'utilisation de la m��thode de projection d'ordre deux coupl��e �� des points de quadrature SPH fixes conduit �� un ordre de convergence de la vitesse qui est de deux et �� une convergence d'ordre sensiblement ��gale �� deux pour la pression, pourvu que la solution soit suffisamment lisse. Dans le cas des calculs �� grandes ��chelles pour les alt��res et pour les cha��nes de bille-ressort, un choix appropri�� du nombre de particules SPH en fonction du nombre des billes N permet, en l'absence des forces d'exclusion de volume, de montrer que le co��t de notre algorithme est d'ordre O(N). Enfin, nous amor��ons des calculs tridimensionnels avec notre mod��le SPH. Dans cette optique, nous r��solvons le probl��me de l'��coulement de Poiseuille tridimensionnel entre deux plaques parall��les infinies et le probl��me de l'��coulement de Poiseuille dans une conduite rectangulaire infiniment longue. De plus, nous simulons en dimension trois des ��coulements confin��s entre deux plaques infinies des solutions de polym��res non dilu��es avec une interaction hydrodynamique et des forces d'exclusion de volume.

Synthesis of ZnO nanoparticles by hydrothermal method

Stable, OH free zinc oxide (ZnO) nanoparticles were synthesized by hydrothermal method by varying the growth temperature and concentration of the precursors. The formation of ZnO nanoparticles were confirmed by x-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies. The average particle size have been found to be about 7-24 nm and the compositional analysis is done with inductively coupled plasma atomic emission spectroscopy (ICP-AES). Diffuse reflectance spectroscopy (DRS) results shows that the band gap of ZnO nanoparticles is blue shifted with decrease in particle size. Photoluminescence properties of ZnO nanoparticles at room temperature were studied and the green photoluminescent emission from ZnO nanoparticles can originate from the oxygen vacancy or ZnO interstitial related defects.

Normalization factors for magnetic relaxation of small particle systems in non-zero magnetic field.

We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors can be obtained from experimental data by using the Tln (t/t0) scaling method without making any assumptions about the nature of the energy barrier distribution. The validity of the procedure is tested using a ferrofluid of Fe3O4 particles.

Capillary electrophoresis characterisation of a rapid prototyped PMMA chip for particle analysis

M��ster en Nanoci��ncia i Nanotecnologia

Lagrangian approximations and weak solutions of the Navier-Stokes equations

The motion of a viscous incompressible fluid flow in bounded domains with a smooth boundary can be described by the nonlinear Navier-Stokes equations. This description corresponds to the so-called Eulerian approach. We develop a new approximation method for the Navier-Stokes equations in both the stationary and the non-stationary case by a suitable coupling of the Eulerian and the Lagrangian representation of the flow, where the latter is defined by the trajectories of the particles of the fluid. The method leads to a sequence of uniquely determined approximate solutions with a high degree of regularity containing a convergent subsequence with limit function v such that v is a weak solution of the Navier-Stokes equations.

The Navier-Stokes Equations with Particle Methods

The non-stationary nonlinear Navier-Stokes equations describe the motion of a viscous incompressible fluid flow for 0<t���T in some bounded three-dimensional domain. Up to now it is not known wether these equations are well-posed or not. Therefore we use a particle method to develop a system of approximate equations. We show that this system can be solved uniquely and globally in time and that its solution has a high degree of spatial regularity. Moreover we prove that the system of approximate solutions has an accumulation point satisfying the Navier-Stokes equations in a weak sense.

Analyse selbsterregter Str��mungsfelder im Verdichter-Leitrad durch Kopplung von Particle Image Velocimetry und Hitzdrahtanemometrie mittels Fast Fourier Transformation

Der Einsatz der Particle Image Velocimetry (PIV) zur Analyse selbsterregter Str��mungsph��nomene und das daf��r notwendige Auswerteverfahren werden in dieser Arbeit beschrieben. Zur Untersuchung von solchen Mechanismen, die in Turbo-Verdichtern als Rotierende Instabilit��ten in Erscheinung treten, wird auf Datens��tze zur��ckgegriffen, die anhand experimenteller Untersuchungen an einem ringf��rmigen Verdichter-Leitrad gewonnen wurden. Die Rotierenden Instabilit��ten sind zeitabh��ngige Str��mungsph��nomene, die bei hohen aerodynamischen Belastungen in Verdichtergittern auftreten k��nnen. Aufgrund der fehlenden Phaseninformation kann diese instation��re Str��mung mit konventionellen PIV-Systemen nicht erfasst werden. Die K��rm��nsche Wirbelstra��e und Rotierende Instabilit��ten stellen beide selbsterregte Str��mungsvorg��nge dar. Die ��hnlichkeit wird genutzt um die Funktionalit��t des Verfahrens anhand der K��rm��nschen Wirbelstra��e nachzuweisen. Der mittels PIV zu visualisierende Wirbeltransport erfordert ein besonderes Verfahren, da ein externes Signal zur Festlegung des Phasenwinkels dieser selbsterregten Str��mung nicht zur Verf��gung steht. Die Methodik basiert auf der Kopplung der PIV-Technik mit der Hitzdrahtanemometrie. Die gleichzeitige Messung mittels einer zeitlich hochaufgel��sten Hitzdraht-Messung erm��glicht den Zeitpunkten der PIV-Bilder einen Phasenwinkel zuzuordnen. Hierzu wird das Hitzdrahtsignal mit einem FFT-Verfahren analysiert, um die PIV-Bilder entsprechend ihrer Phasenwinkel zu gruppieren. Daf��r werden die aufgenommenen Bilder auf der Zeitachse der Hitzdrahtmessungen markiert. Eine systematische Analyse des Hitzdrahtsignals in der Umgebung der PIV-Messung liefert Daten zur Festlegung der Grundfrequenz und erlaubt es, der markierten PIV-Position einen Phasenwinkel zuzuordnen. Die sich aus den PIV-Bildern einer Klasse ergebenden Geschwindigkeitskomponenten werden anschlie��end gemittelt. Aus den resultierenden Bildern jeder Klasse ergibt sich das zweidimensionale zeitabh��ngige Geschwindigkeitsfeld, in dem die Wirbelwanderung der K��rm��nschen Wirbelstra��e ersichtlich wird. In hierauf aufbauenden Untersuchungen werden Zeitsignale aus Messungen in einem Verdichterringgitter analysiert. Dabei zeigt sich, dass zus��tzlich Filterfunktionen erforderlich sind. Im Ergebnis wird schlie��lich deutlich, dass die ��bertragung der anhand der K��rm��nschen Wirbelstra��e entwickelten Methode nur teilweise gelingt und weitere Forschungsarbeiten erforderlich sind.

A Conservative Front Tracking Algorithm

The discontinuities in the solutions of systems of conservation laws are widely considered as one of the difficulties in numerical simulation. A numerical method is proposed for solving these partial differential equations with discontinuities in the solution. The method is able to track these sharp discontinuities or interfaces while still fully maintain the conservation property. The motion of the front is obtained by solving a Riemann problem based on the state values at its both sides which are reconstructed by using weighted essentially non oscillatory (WENO) scheme. The propagation of the front is coupled with the evaluation of "dynamic" numerical fluxes. Some numerical tests in 1D and preliminary results in 2D are presented.

An Immersed Interface Method for the Incompressible Navier-Stokes Equations in Irregular Domains

We present an immersed interface method for the incompressible Navier Stokes equations capable of handling rigid immersed boundaries. The immersed boundary is represented by a set of Lagrangian control points. In order to guarantee that the no-slip condition on the boundary is satisfied, singular forces are applied on the fluid at the immersed boundary. The forces are related to the jumps in pressure and the jumps in the derivatives of both pressure and velocity, and are interpolated using cubic splines. The strength of singular forces is determined by solving a small system of equations at each time step. The Navier-Stokes equations are discretized on a staggered Cartesian grid by a second order accurate projection method for pressure and velocity.

On the Fabrication of Microparticles Using Electrohydrodynamic Atomization Method

A new approach for the control of the size of particles fabricated using the Electrohydrodynamic Atomization (EHDA) method is being developed. In short, the EHDA process produces solution droplets in a controlled manner, and as the solvent evaporates from the surface of the droplets, polymeric particles are formed. By varying the voltage applied, the size of the droplets can be changed, and consequently, the size of the particles can also be controlled. By using both a nozzle electrode and a ring electrode placed axisymmetrically and slightly above the nozzle electrode, we are able to produce a Single Taylor Cone Single Jet for a wide range of voltages, contrary to just using a single nozzle electrode where the range of permissible voltage for the creation of the Single Taylor Cone Single Jet is usually very small. Phase Doppler Particle Analyzer (PDPA) test results have shown that the droplet size increases with increasing voltage applied. This trend is predicted by the electrohydrodynamic theory of the Single Taylor Cone Single Jet based on a perfect dielectric fluid model. Particles fabricated using different voltages do not show much change in the particles size, and this may be attributed to the solvent evaporation process. Nevertheless, these preliminary results do show that this method has the potential of providing us with a way of fine controlling the particles size using relatively simple method with trends predictable by existing theories.

Fabrication of Controlled Release Devices Using Supercritical Antisolvent Method

In this study, the supercritical antisolvent with enhanced mass transfer method (SASEM) is used to fabricate micro and nanoparticles of biocompatible and biodegradable polymer PLGA (poly DL lactide co glycolic acid). This process may be extended to the encapsulation of drugs in these micro and nanoparticles for controlled release purposes. Conventional supercritical antisolvent (SAS) process involves spraying a solution (organic solvent + dissolved polymer) into supercritical fluid (CO[subscript 2]), which acts as an antisolvent. The high rate of mass transfer between organic solvent and supercritical CO[subscript 2] results in supersaturation of the polymer in the spray droplet and precipitation of the polymer as micro or nanoparticles occurs. In the SASEM method, ultrasonic vibration is used to atomize the solution entering the high pressure with supercritical CO[subscript 2]. At the same time, the ultrasonic vibration generated turbulence in the high pressure vessel, leading to better mass transfer between the organic solvent and the supercritical CO���. In this study, two organic solvents, acetone and dichloromethane (DCM) were used in the SASEM process. Phase Doppler Particle Analyzer (PDPA) was used to study the ultrasonic atomization of liquid using the ultrasonic probe for the SASEM process. Scanning Electron Microscopy (SEM) was used to study the size and morphology of the polymer particles collected at the end of the process.