Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2006. / Includes bibliographical references (p. 91).

Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (M.E.)--University of Canterbury, 1997. / Typescript (photocopy). Includes bibliographical references (leaf 39). Also available via the World Wide Web.

Thesis (M.S. in environmental science)--Washington State University, August 2007. / Includes bibliographical references (p. 19).

No description available.

The aim of this study is to perform the dynamic force analysis of a 3-degrees-of-freedom excavator during digging the soil and to simulate the motion on computer screen. Standard load calculations are done statically, therefore the effects of forces changing with time on the system cannot be observed. The dynamic analysis method used in the thesis is Recursive Newton &ndash / Euler Method and the numerical analysis method for simulation is 4th Order Runge &ndash / Kutta Method. After this study, the effects of sudden velocity changes / i.e, accelerational movements on construction machines, positions of bodies and dynamic forces on joints will be appointed and it will be possible to plan and control the motion.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on November 18, 2009). Thesis advisor: Dr. Roger Fales. Includes bibliographical references.

Automotive active suspension, advanced seismic testing, and force/torque emulations of space manipulators are examples of applications, where the hydraulic actuator force control is required. In double-rod hydraulic actuators, the actuator force is the differential pressure across the actuator multiplied by the piston effective area. The focus of this work is to control the actuator force of a double-rod hydraulic actuator by controlling the differential pressure across the actuator. The double-rod hydraulic actuator of this study is run by two independent circuits: 1) electro-hydraulic actuation and 2) electro-hydrostatic actuation. In general, developing controllers for hydraulic actuators is challenging due to the presence of parametric uncertainties and uncertain nonlinearities. Also, a specific challenge in force control of hydraulic actuators is the limiting effect of environment dynamics on the maximum achievable tracking bandwidth. Considering the above challenges, in this research for the first time, quantitative feedback theory (QFT) is employed to control the hydraulic actuator force. Using QFT, a robust, linear, fixed-gain, and low-order controller is designed for each actuation system which: (i) keeps the closed-loop response within desired tracking bounds (ii) guarantees the closed-loop stability around desired operating points, (iii) rejects disturbance, and (iv) achieves desired tracking bandwidth. Among the performance criteria, special attention is paid to achieve high tracking bandwidth. Trade-offs between different performance criteria towards achieving high tracking bandwidth, are discussed. Experimental results are presented to validate that the performance criteria are satisfied by the designed QFT controllers. The QFT controllers are synthesized based on the families of frequency responses of the hydraulic actuation systems, which limits the stability results of the closed-loop system, only for these families of the frequency responses. In this thesis, to investigate the nonlinear stability of the closed-loop systems with QFT controllers, for the first time, Takagi-Sugeno (T-S) fuzzy modeling and its corresponding stability theory are used. The stability conditions are presented in the form of linear matrix inequalities (LMIs). As a result, the nonlinear stability of the designed QFT controllers for both the actuation systems is proven in the presence of parametric uncertainties. / February 2016

La surverse d’une digue fluviale (levée) peut conduire au développement d’une brèche par érosion externe, suivie d’une rupture brutale de la digue. Cela provoquerait une vague de submersion dans la plaine protégée, laquelle peut présenter des enjeux humains, économiques et financiers majeurs. La gestion et la prévention du risque d’inondation passe par une détermination précise de l’aléa. Pour ce faire, il est nécessaire d’avoir une estimation fiable du débit au travers de la brèche, donc du mécanisme de formation de la brèche et de sa dynamique d’expansion. Les approches existantes sont souvent adaptées pour les digues frontales (barrage et remblai en terre) soumises aux surverses. La transposition de ces approches pour les digues fluviales demeure peu fiable. Les processus qui régissent la formation des brèches dans les digues fluviales restent donc encore du domaine de la recherche. Un programme expérimental visant à améliorer notre compréhension des processus physiques qui régissent la rupture graduelle des digues fluviales par surverse a été mené conjointement par le Laboratoire National d’Hydraulique et Environnement (LNHE) de la division R&D d’EDF et le groupe de recherche Hydraulics in Environmental and Civil Engineering (HECE) de l’Université de Liège. Les travaux ont été conduits sur deux dispositifs expérimentaux distincts, chacun constitué d’un canal principal et d’une plaine d’inondation, séparés par une digue fluviale. Nous nous sommes focalisés sur les surverses localisées de digues homogènes non-cohésives. Une métrologie adaptée, incluant la mesure détaillée de l’évolution de la géométrie de la brèche en continu, par une technique non intrusive (profilométrie laser), a été développée et exploitée dans les travaux de cette thèse. Les tests, réalisés sous conditions contrôlées, ont permis d’investiguer l’évolution de la bèche et des débits sortants pour différentes conditions hydrauliques (débits d’entrée dansle canal principal, régulation du débit sortant en aval du canal principal, confinement de la plaine inondable). Les effets des dimensions du canal principal, de la taille des sédiments et de la cohésion apparente ou encore de la mobilité des fonds au pied de la digue ont fait également l’objet d’étude. En exploitant les mesures, l’évolution des écoulements au voisinage de la brèche a été simulée avec le code de calcul bidimensionnel TELEMAC-2D, permettant d’évaluer les performances de ce code pour des cas d’écoulements, en rupture de digue fluviale, hautement transitoires et complexes. Le couplage avec le code morpho dynamique 2-D SISYPHE a permis d’apprécier l’apport d’une modélisation hydro-morpho dynamique détaillée à l’étude des brèches dans les digues fluviales / Overtopping of fluvial dikes (dykes or embankment levees) can promote external erosion, leading to the initiation of breaching and potentially brutal dike failure and inundation of the protected area. This can generate major human, economic, and financial losses. Flood risk management and prevention require precise hazard quantification. Accurate estimate of the flow through the breach is paramount, for which a precise understanding of the breach formation and expansion is required. Existing methods are often the result of investigations conducted on overtopping of frontal dikes (embankment dams). The application of such approaches to fluvial dikes is not reliable and processes underpinning breach expansion are still under research. An innovative experimental program was conducted to fill this gap by investigating the physical processes involved in overtopping induced fluvial dike gradual breaching. Experiments were conducted in the framework of collaboration between the National Laboratory for Hydraulics and Environment (LNHE) of the R&D division of EDF and the research team Hydraulics in Environmental and Civil Engineering (HECE) of University of Liège. Experiments were conducted on two distinct experimental setups, each consisting of a main channel and floodplain area separated by an erodible fluvial dike. The focus was made on overtopping induced spatial erosion of homogenous, non-cohesive dikes. Measurements included continuous scanning of the dike geometry using a non-intrusive method (Laser Profilometry Technique), which was designed and developed specifically for the present works. Tests conducted under controlled flow and dike configurations allowed assessing the effects of channel inflow discharge, downstream channel regulation system, and floodplain confinement on the breach development and outflow. Effects of main channel size, dike material size, apparent cohesion, and bottom erodibility were studied as well. Using the experimental data, the flow features near the breach area was simulated using the two-dimensional depth-averaged hydrodynamic code TELEMAC-2D, which allowed assessing the performance of the code for highly transient and complex flows such as involved in dike breaching. Coupling TELEMAC-2D with the morphodynamic model SISYPHE enabled investigating the interest of a detailed hydro-morphodynamic modeling for fluvial dike breaching studies