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Evaluation of hybrid-electric propulsion systems for unmanned aerial vehiclesMatlock, Jay Michael Todd 14 January 2020 (has links)
The future of aviation technology is transitioning to cleaner, more efficient and higher endurance aircraft solutions. As fully electric propulsion systems still fall short of the operational requirements of modern day aircraft, there is increasing pressure and demand for the aviation industry to explore alternatives to fossil fuel driven propulsion systems. The primary focus of this research is to experimentally evaluate hybrid electric propulsion systems (HEPS) for Unmanned Aerial Vehicles (UAV) which combine multiple power sources to improve performance. HEPS offer several potential benefits over more conventional propulsion systems such as a smaller environmental impact, lower fuel consumption, higher endurance and novel configurations through distributed propulsion. Advanced operating modes are also possible with HEPS, increasing the vehicle’s versatility and redundancy in case of power source failure.
The primary objective of the research is to combine all of the components of a small-scale HEPS together in a modular test bench for evaluation. The test bench uses components sized for a small-scale UAV including a 2.34kW two-stroke 35cc engine and a 1.65kW brushless DC motor together with an ESC capable of regenerative braking. Individual components were first tested to characterize performance, and then all components were assembled together in a parallel configuration to observe system-level performance. The parallel HEPS is capable of functioning in the four required operating modes: EM Only, ICE Only, Dash Mode (combined EM and ICE power) as well as Regenerative Mode where the onboard batteries get recharged. Further, the test bench was implemented with a supervisory controller to optimize system performance and run each component in the most efficient region to achieve torque requirements programmed into mission profiles. The logic based controller operates with the ideal operating line (IOL) concept and is implemented with a custom LabView GUI.
The system is able to run on electric power or ICE power interchangeably without making any modifications to the transmission as the one-way bearing assembly engages for whichever power source is rotating at the highest speed. The most impressive of these sets of tests is the Dash mode testing where the output torque of the propeller is supplied from both the EM and ICE. Working in tandem, it was proved that the EM was drawing 19.9A of current which corresponds to an estimated 0.57Nm additional torque to the propeller for a degree of hybridization of 49.91%. Finally, the regenerative braking mode was proven to be operational, capable of recharging the battery systems at 13A. All of these operating modes attest to the flexibility and convenience of having a hybrid-electric propulsion system.
The results collected from the test bench were validated against the models created in the aircraft simulation framework. This framework was created in MATLAB to simulate the performance of a small UAV and compare the performance by swapping in various propulsion systems. The purpose of the framework is to make direct comparisons of HEPS performance for parallel and series architectures against conventional electric and gasoline configuration UAVs, and explore the trade-offs. Each aircraft variable in the framework was modelled parametrically so that parameter sweeps could be run to observe the impact on the aircraft’s performance. Finally, rather than comparing propulsion systems in steady-state, complex mission profiles were created that simulate real life applications for UAVs. With these experiments, it was possible to observe which propulsion configurations were best suited for each mission type, and provide engineers with information about the trade-offs or advantages of integrating hybrid-electric propulsion into UAV design.
In the Pipeline Inspection mission, the exact payload capacities of each aircraft configuration could be observed in the fuel burn versus CL,cruise parameter sweep exercise. It was observed that the parallel HEPS configuration has an average of 3.52kg lower payload capacity for the 35kg aircraft (17.6%), but has a fuel consumption reduction of up to 26.1% compared to the gasoline aircraft configuration. In the LIDAR Data collection mission, the electric configuration could be suitable for collection ranges below 100km but suffers low LIDAR collection times. However, at 100km LIDAR collection range, the series HEPS has an endurance of 16hr and the parallel configuration has an endurance of 19hr. In the Interceptor mission, at 32kg TOW, the parallel HEPS configuration has an endurance/TOW of 1.3[hr/kg] compared to 1.15[hr/kg] for the gasoline aircraft. This result yields a 13% increase in endurance from 36.8hr for gasoline to 41.6hr for the parallel HEPS. Finally, in the Communications Relay mission, the gasoline configuration is recommended for all TOW above 28kg as it has the highest loiter endurance. / Graduate
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Hybrid Approaches in Test Suite PrioritizationNurmuradov, Dmitriy 05 1900 (has links)
The rapid advancement of web and mobile application technologies has recently posed numerous challenges to the Software Engineering community, including how to cost-effectively test applications that have complex event spaces. Many software testing techniques attempt to cost-effectively improve the quality of such software. This dissertation primarily focuses on that of hybrid test suite prioritization. The techniques utilize two or more criteria to perform test suite prioritization as it is often insufficient to use only a single criterion. The dissertation consists of the following contributions: (1) a weighted test suite prioritization technique that employs the distance between criteria as a weighting factor, (2) a coarse-to-fine grained test suite prioritization technique that uses a multilevel approach to increase the granularity of the criteria at each subsequent iteration, (3) the Caret-HM tool for Android user session-based testing that allows testers to record, replay, and create heat maps from user interactions with Android applications via a web browser, and (4) Android user session-based test suite prioritization techniques that utilize heuristics developed from user sessions created by Caret-HM. Each of the chapters empirically evaluate the respective techniques. The proposed techniques generally show improved or equally good performance when compared to the baselines, depending on an application under test. Further, this dissertation provides guidance to testers as it relates to the use of the proposed hybrid techniques.
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Investigation of the higher mode effects on the dynamic behaviour of reinforced concrete shear walls through a pseudo-dynamic hybrid test / Étude de l’effet des modes supérieurs sur le comportement dynamique des murs de refend en béton armé à l’aide d’un essai pseudo-dynamique avec sous-structureFatemi, Hassan January 2017 (has links)
La plupart des bâtiments de moyenne et grande hauteur en béton armé sont munis de murs
de refend ductiles afin résister aux charges latérales dues au vent et aux séismes. Les murs de
refend ductiles sont conçus selon des règles conception stricts. Ces murs sont généralement
conçus de façon à forcer la formation d’une rotule plastique à leur base dans l’éventualité d’un
séismemajeur. Lors de la conception d’un mur, l’enveloppe des moments fléchissants ainsi que
l’enveloppe des efforts tranchants dans la portion du mur situé au-dessus de la rotule plastique
sont basés sur la résistance probable en flexion du mur dans la région de la rotule plastique.
Plusieurs études sur les murs de refend conçus selon cette philosophie de conception on fait le
constat que l’effort tranchant maximum dans un mur peut être sous-estimé lors d’un séisme,
et que des rotules plastiques peuvent également se former à d’autres endroits qu’à la base
du mur, ce qui constitue un mécanisme de ruine indésirable. Ces effets sont principalement
attribuables à la contribution des modes supérieures à la réponse dynamique globale des bâtiments
lors d’un séisme. L’effet des modes supérieurs est particulièrement important dans les
bâtiments élancés de grande hauteur ayant une période propre de vibration longue.
L’essai pseudo-dynamique avec sous-structure est uneméthode efficace et économique d’évaluer
expérimentalement l’effet des modes supérieurs sur le comportement sismique des murs de
refend dans les bâtiments. Lors de tels essais, comme la masse du bâtiment est modélisée
numériquement, ceci permet de tester des structures à de relativement grandes échelles sans
avoir à combattremécaniquement les forces d’inerties générées lors d’un séisme. Dans le cadre
de la présente étude, la portion constituant la base d’un mur de refend correspondant à la zone
de rotule plastique faisant partie d’un bâtiment de huit étages à l’échelle 1/2,75 a été testé. Les
dimensions générales de la portion de mur testée étaient de 1800 mm de longueur, par 2200 mm
de hauteur par 160 mm d’épaisseur. Le mur étudié a été conçu selon l’édition 2015 du Code
National du Bâtiment du Canada (CNBC 2015) ainsi que selon la norme CSA A23.3-14 (Calcul
des ouvrages en béton), où le facteur d’amplification de l’effort tranchant causé par l’effet des
modes supérieurs n’a pas été pris en compte.
Lors des essais pseudo-dynamiques avec sous-structure, une nouvelle méthode de contrôle à
trois degrés de liberté convenant à des spécimens d’essai très rigides axialement a été développée
et validée. Une procédure novatrice de redémarrage d’un essai interrompu en cours de
route a également été développée et validée. Lors des essais, le bâtiment de huit étages incluant
la portion de mur dans le laboratoire a été soumis à trois séismes. Le premier séisme était
de très faible intensité, l’intensité du deuxième séisme correspondait au séisme de conception,
et le troisième séisme correspondait au séisme de conception dont l’intensité a été doublé. Durant
les deux séismes de forte intensité, le mur testé s’est comporté de manière ductile et des
fissures de cisaillement et de flexion importantes ont été observées. Même si l’effort tranchant
maximum mesuré durant le séisme de conception a atteint 2,16 fois la valeur de conception
du mur, et 3,01 fois la valeur de conception du mur dans le cas du séisme amplifié, aucun mécanisme
de ruine n’a été observé. Suite aux essais pseudo-dynamiques avec sous-structure, un
essai par poussée progressive a également été effectué.
Les résultats des essais pseudo-dynamiques avec sous-structure portent à croire que la valeur
de l’effort tranchant de conception d’un mur selon la norme CSA A23.3-14 est sous-estimé. De
plus, l’essai poussée progressive a permis de démontrer que lemur était beaucoup plus résistant
qu’anticipé, puisque l’effort tranchant avait été sous-estimé lors de la conception. L’essai par
poussée progressive a également permis de démontrer que le mur peut atteindre des niveaux
de ductilité en déplacement supérieur à celui prévu par la norme CSA A23.3-14. / Abstract: Most mid- and high-rise reinforced concrete (RC) buildings rely on RC structural walls as their seismic force resisting system. Ductile RC structural walls (commonly called shear walls) designed according to modern building codes are typically detailed to undergo plastic hinging at their base. Both the design moment envelope for the remaining portion of the wall and the design shear forces are evaluated based on the probable flexural resistance of the wall in the plastic hinge region. Several analytical studies have shown that so-designed structural walls can be subjected to shear forces in excess of the design values. Plastic hinging can also develop in the upper portion of the walls. These effects are mainly attributed to higher mode response and, hence, are more severe in taller or slender walls with long fundamental periods. Considering the literature, there is a significant uncertainty regarding the behavior of the structural walls under the higher mode of vibrations excited under earthquake excitations. Hybrid testing is an effective experimentalmethod to study the natural behaviour of structures such as shear walls. The hybrid testing method enables the simulation of the seismic response of large structural elements like RC shear walls without the need to include large masses typically encountered in multi-storey buildings. In this study a barbell shaped RC shear wall specimen of 1800mm in length including a 300mm × 300mm boundary element at each end that is 2200mm in height, and 160mm thick was investigated. A test specimen corresponding to the base plastic hinge zone of an 8-storey shear wall was tested in a laboratory evolvement whilst the reminder of the building structure was modeled numerically. The reference wall was scaled down by a factor of 1/2.75 to obtain dimensions of the test specimen. The RC wall was designed in accordance with the 2015 edition of the National Building Code of Canada (NBCC 2015) and the Canadian Standard Association A23.3-14 code. The amplification of the base design shear force accounting for the inelastic effects of higher modes specified by the CSAA23.3-14 standard was not taken into account in order to evaluate the amplification experimentally. In order to investigate the response of ductile RC walls under earthquake ground motions and track the effect of the higher vibration modes on the shear force demand, three earthquakes with different intensities were applied on the hybrid model successively. The RC wall exhibited a ductile behaviour under the ground motions and flexural and shear cracks developed all over the height of the wall. In spite of amplifying the shear force demand by a factor of 2.16 under the design level earthquake and 3.01 under a high intensity earthquake, no shear failure was observed. The test results indicated that the amplification of the design shear forces at the base of ductile RC shear walls are underestimated by the CSAA23.3-14 standard. A new method for controlling three degrees of freedomin hybrid simulation of the earthquake response of stiff specimens was developed and verified in this study. Also, an innovative procedure to restore an interrupted hybrid test was programmed and verified. The hybrid tests were followed by a push-over test under a lateral force distribution equal to the square root of sum of the squares of the first five modes in order to evaluate the displacement ductility of the RC wall. Findings of the final push-over test showed that the tested ductile RC wall can withstand higher displacement ductilities than the presented levels in the NBCC 2015.
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