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1
Östlin, Christofer. "Single-molecule X-ray free-electron laser imaging : Interconnecting sample orientation with explosion data." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231009.
Повний текст джерелаАнотація:
X-ray crystallography has been around for 100 years and remains the preferred technique for solving molecular structures today. However, its reliance on the production of sufficiently large crystals is limiting, considering that crystallization cannot be achieved for a vast range of biomolecules. A promising way of circumventing this problem is the method of serial femtosecond imaging of single-molecules or nanocrystals utilizing an X-ray free-electron laser. In such an approach, X-ray pulses brief enough to outrun radiation damage and intense enough to provide usable diffraction signals are employed. This way accurate snapshots can be collected one at a time, despite the sample molecule exploding immediately following the pulse due to extreme ionization. But as opposed to in conventional crystallography, the spatial orientation of the molecule at the time of X-ray exposure is generally unknown. Consequentially, assembling the snapshots to form a three-dimensional representation of the structure of interest is cumbersome, and normally tackled using algorithms to analyze the diffraction patterns. Here we explore the idea that the explosion data can provide useful insights regarding the orientation of ubiquitin, a eukaryotic regulatory protein. Through two series of molecular dynamics simulations totaling 588 unique explosions, we found that a majority of the carbon atoms prevalent in ubiquitin are directionally limited in their respective escape paths. As such we conclude it to be theoretically possible to orient a sample with known structure based on its explosion pattern. Working with an unknown sample, we suggest these discoveries could be applicable in tandem with X-ray diffraction data to optimize image assembly.
2
Lewis, Christopher James. "Development of a Methodology for Numerical Simulation of a D C ARC Discharge in a Liquid Dielectric." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2394.
Повний текст джерелаАнотація:
The majority of literature regarding the numerical simulation of arc discharges in gaseous environments has used a plasma physics approach. Virtually all simulations treat the discharge as an idealized gaseous plasma, which can be described by temperature, pressure, and electric field. This approach can work well if the media is a shielding gas such as Argon; however, the approach does not work well for processes such as underwater welding, EDM, and underwater discharges used to generate high purity particles. The reason these discharges do not have many extensive simulation efforts as described in the literature is because they occur in liquid dielectric media (Oil and water) which complicates the simulation efforts. Most research efforts in these areas describe experimental methods to evaluate discharge properties In this research a new method to investigate discharges in a dielectric media using an electrostatic and particle physics approach is proposed and validated. A commercial code that has been developed to simulate charged particle beams, dielectric materials, and perform multi-physics analyses, is the Vector Fields suite of solvers from Cobham Technical Services. This research demonstrates a simulation methodology that can be used to simulate a DC electric arc discharge in a lossy dielectric media using the Vector Fields environment. This simulation is the first of its kind to simulate this type of a discharge with a commercial FEA code. As such there are some limitations to the simulation. However, the simulation can be used to investigate the following:
1.Any metal, electrode geometry, discharge gap, or dielectric media can be studied
2.Primary Beam Physics
– Electron velocity/acceleration (direct calculation of electron temperature)
– Energy deposition on the anode from all emission sources
– Effect of dielectric media on beam physics (trajectories, velocity, constriction, beam induced magnetic fields, space chare, and secondary emission)
– Beam current
– Particle trajectories (including relativistic effects)
3. Secondary Particle Generation and physics
– Atomic species (neutral particles or ions) and secondary electron emission
– Particle trajectories
– Back ion bombardment on the cathode
3
Suares, Ian Greg. "Ice particle trajectory simulation." Thesis, Wichita State University, 2005. http://hdl.handle.net/10057/1610.
Повний текст джерелаАнотація:
Large ice particles shed from an airframe can cause damage to downstream
aerodynamic surfaces and aft mounted engines. A simulation tool was developed to
compute the trajectories of shed ice particles and determine the probability of these
particles passing through a particular downstream location. The flowfield into which the
ice particles shed was determined using CFD. The aerodynamic forces and moments
acting on the ice particles were obtained from published literature and experimental data.
Three, four and six degree of freedom trajectory simulation models were developed to
compute the trajectories of shed ice particles. Monte Carlo simulations were performed
by varying the aerodynamic and geometric properties of the ice particles to obtain a
probability map depicting the regions where the ice particles were most likely to strike.Includes bibliographical references (p.117-120)
4
Kozák, Josef. "Scintilační detektor sekundárních elektronů s řízeným prouděním plynů pro EREM." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217926.
Повний текст джерелаАнотація:
This master’s thesis deals with a design and optimization of an experimental scintillation secondary electron detector for the environmental scanning electron microscope and with a description of a detector operation principle. The experiment is founded on simulations of a gas flow in detector inner sections and on simulations of secondary electron trajectories in electrostatic fields of the detector. On the basis of the simulations, new solutions of the detector designs are proposed. For these designs, same simulations as previous are performed and designs that seem to be feasible for the secondary electron detection in environmental scanning electron microscope are selected.
5
Santiteerakul, Wasana. "Trajectory Analytics." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801885/.
Повний текст джерелаАнотація:
The numerous surveillance videos recorded by a single stationary wide-angle-view camera persuade the use of a moving point as the representation of each small-size object in wide video scene. The sequence of the positions of each moving point can be used to generate a trajectory containing both spatial and temporal information of object's movement. In this study, we investigate how the relationship between two trajectories can be used to recognize multi-agent interactions. For this purpose, we present a simple set of qualitative atomic disjoint trajectory-segment relations which can be utilized to represent the relationships between two trajectories. Given a pair of adjacent concurrent trajectories, we segment the trajectory pair to get the ordered sequence of related trajectory-segments. Each pair of corresponding trajectory-segments then is assigned a token associated with the trajectory-segment relation, which leads to the generation of a string called a pairwise trajectory-segment relationship sequence. From a group of pairwise trajectory-segment relationship sequences, we utilize an unsupervised learning algorithm, particularly the k-medians clustering, to detect interesting patterns that can be used to classify lower-level multi-agent activities. We evaluate the effectiveness of the proposed approach by comparing the activity classes predicted by our method to the actual classes from the ground-truth set obtained using the crowdsourcing technique. The results show that the relationships between a pair of trajectories can signify the low-level multi-agent activities.
6
Kayumbi-Kabeya, Gabin-Wilfried. "Algorithms for trajectory integration in multiple views." Thesis, Queen Mary, University of London, 2009. http://qmro.qmul.ac.uk/xmlui/handle/123456789/573.
Повний текст джерелаАнотація:
This thesis addresses the problem of deriving a coherent and accurate localization of moving objects from partial visual information when data are generated by cameras placed in di erent view angles with respect to the scene. The framework is built around applications of scene monitoring with multiple cameras. Firstly, we demonstrate how a geometric-based solution exploits the relationships between corresponding feature points across views and improves accuracy in object location. Then, we improve the estimation of objects location with geometric transformations that account for lens distortions. Additionally, we study the integration of the partial visual information generated by each individual sensor and their combination into one single frame of observation that considers object association and data fusion. Our approach is fully image-based, only relies on 2D constructs and does not require any complex computation in 3D space. We exploit the continuity and coherence in objects' motion when crossing cameras' elds of view. Additionally, we work under the assumption of planar ground plane and wide baseline (i.e. cameras' viewpoints are far apart). The main contributions are: i) the development of a framework for distributed visual sensing that accounts for inaccuracies in the geometry of multiple views; ii) the reduction of trajectory mapping errors using a statistical-based homography estimation; iii) the integration of a polynomial method for correcting inaccuracies caused by the cameras' lens distortion; iv) a global trajectory reconstruction algorithm that associates and integrates fragments of trajectories generated by each camera.
7
Anjum, Nadeem. "Trajectory based video analysis in multi-camera setups." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/629.
Повний текст джерелаАнотація:
This thesis presents an automated framework for activity analysis in multi-camera setups. We start with the calibration of cameras particularly without overlapping views. An algorithm is presented that exploits trajectory observations in each view and works iteratively on camera pairs. First outliers are identified and removed from observations of each camera. Next, spatio-temporal information derived from the available trajectory is used to estimate unobserved trajectory segments in areas uncovered by the cameras. The unobserved trajectory estimates are used to estimate the relative position of each camera pair, whereas the exit-entrance direction of each object is used to estimate their relative orientation. The process continues and iteratively approximates the configuration of all cameras with respect to each other. Finally, we refi ne the initial configuration estimates with bundle adjustment, based on the observed and estimated trajectory segments. For cameras with overlapping views, state-of-the-art homography based approaches are used for calibration. Next we establish object correspondence across multiple views. Our algorithm consists of three steps, namely association, fusion and linkage. For association, local trajectory pairs corresponding to the same physical object are estimated using multiple spatio-temporal features on a common ground plane. To disambiguate spurious associations, we employ a hybrid approach that utilises the matching results on the image plane and ground plane. The trajectory segments after association are fused by adaptive averaging. Trajectory linkage then integrates segments and generates a single trajectory of an object across the entire observed area. Finally, for activities analysis clustering is applied on complete trajectories. Our clustering algorithm is based on four main steps, namely the extraction of a set of representative trajectory features, non-parametric clustering, cluster merging and information fusion for the identification of normal and rare object motion patterns. First we transform the trajectories into a set of feature spaces on which Meanshift identi es the modes and the corresponding clusters. Furthermore, a merging procedure is devised to re fine these results by combining similar adjacent clusters. The fi nal common patterns are estimated by fusing the clustering results across all feature spaces. Clusters corresponding to reoccurring trajectories are considered as normal, whereas sparse trajectories are associated to abnormal and rare events. The performance of the proposed framework is evaluated on standard data-sets and compared with state-of-the-art techniques. Experimental results show that the proposed framework outperforms state-of-the-art algorithms both in terms of accuracy and robustness.
8
Bereza-Jarocinski, Robert, and Therese Persson. "Autonomous Trajectory Tracking and Obstacle Avoidance." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214704.
Повний текст джерелаАнотація:
Autonomous ground vehicles (AGVs), such as selfdrivingcars, are expected to become a central part of infrastructurein future smart cities. There are many technicalchallenges with making vehicles autonomous. They have to beable to find their way in both free environments as well asin environments with obstacles and other vehicles. To achievethis, they require many sensors to analyze their surroundings.The aim with this paper is to investigate the sensor typesnormally used in AGVs, describe their functionality and alsoprovide a model of how an autonomous vehicle can navigate indifferent environments, and verify this model through simulation.Lidar, Radar, accelerometers, gyroscopes, positioning systems andcameras are the sensors that are listed. It is described whatthey measure and what this data can be used for. To model theautonomous vehicle, a car-like vehicle model is used. A trajectorytracking controller is proposed, together with a proof of itsstability using Lyapunov functions. A way to avoid stationaryobstacles using potential fields is also described. Both the trackingcontroller and the obstacle avoidance controller are shown towork as expected through simulation. The used model only allowsfor the vehicle to travel in directions within a span of ±45 of itsforward direction. Lastly, a new application for AGVs in smartcities is also proposed.
9
Bereza, Robert, and Therese Persson. "Autonomous Trajectory Tracking and Obstacle Avoidance." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214704.
Повний текст джерелаАнотація:
Autonomous ground vehicles (AGVs), such as selfdrivingcars, are expected to become a central part of infrastructurein future smart cities. There are many technicalchallenges with making vehicles autonomous. They have to beable to find their way in both free environments as well asin environments with obstacles and other vehicles. To achievethis, they require many sensors to analyze their surroundings.The aim with this paper is to investigate the sensor typesnormally used in AGVs, describe their functionality and alsoprovide a model of how an autonomous vehicle can navigate indifferent environments, and verify this model through simulation.Lidar, Radar, accelerometers, gyroscopes, positioning systems andcameras are the sensors that are listed. It is described whatthey measure and what this data can be used for. To model theautonomous vehicle, a car-like vehicle model is used. A trajectorytracking controller is proposed, together with a proof of itsstability using Lyapunov functions. A way to avoid stationaryobstacles using potential fields is also described. Both the trackingcontroller and the obstacle avoidance controller are shown towork as expected through simulation. The used model only allowsfor the vehicle to travel in directions within a span of ±45 of itsforward direction. Lastly, a new application for AGVs in smartcities is also proposed.
10
Lam, Hoi-yee. "Voltage-current trajectory a 2-dimensional approach to understand electrical load signatures /." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B3890861X.
Повний текст джерела
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Müller, Daniel. "Trajectory Generation under Metric Interval Temporal Logic Specifications." Thesis, KTH, Reglerteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217122.
Повний текст джерелаАнотація:
Metric interval temporal logic (MITL) provides a tool to formulate high level tasks in an easyway. This allows to specify behaviour of a dynamical system in a given environment which liesbeyond the scope of simple stabilization. Finding an input of the system which satises the MITLformula, demands new techniques and algorithms. In this thesis, a novel approach is presented whichabstracts the dynamical system into a time optimal weighted transition system (WTS) and convertsthe MITL formula into a Timed Buchi Automaton (TBA). From the graph product of the WTS andTBA a sequence of environment states together with time constraints is obtained. Together with auser specied cost function, the sequence is translated into an optimization problem. The solutionof this nal optimization problem satises the MITL formula for the dynamical system in the givenenvironment and is obtained by using methods from optimal control.Metric interval temporal logic (MITL) ger ett verktyg för att formulera uppgifter på hög nivåpå ett enkelt sätt. Detta gör det möjligt att specificera beteendet hos ett dynamiskt system i engiven miljö som ligger utanför ramen för enkel stabilisering. Att hitta en insignal till systemet somuppfyller MITL-formeln kräver nya tekniker och algoritmer. I denna avhandling presenteras ett nytttillvägagångssätt som abstraherar det dynamiska systemet till ett tidsoptimerat weighted transitionsystem (WTS) och omvandlar MITL-formeln till en Timed Büchi Automaton (TBA). Frångrafprodukten av WTS och TBA erhålls en sekvens av sakens tillstånd tillsammans med tidsbegränsningar. Tillsammans med en användardefinierad kostnadsfunktion är sekvensen översatt till ettoptimeringsproblem. Lösningen av det här slutliga optimeringsproblemet uppfyller MITL-formelnför det dynamiska systemet i den givna miljön och erhålls genom att använda metoder från optimalkontroll.
12
Glamheden, Mikael, and Simon Eriksson. "Autonomous Trajectory Tracking for a Differential Drive Vehicle." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239351.
Повний текст джерелаАнотація:
This paper explores controlling a two-wheeled differential drive vehicle using path planning algorithms and potential fields in order to track a target area while avoiding obstacles. Additionally, formation control was investigated using potential fields and a virtual structure approach separately. Finally, analysis of communication constraints in the form of sampling, disturbances and quantization are taken into account and theoretical or analysis results are given. It was concluded that the potential fields method result in an intuitive and dynamic controller that can be used to navigate within a large-scale and dynamic environment, as well as be used for formation control. The virtual structure approach is more robust when dealing with formation control, but it does not consider obstacle avoidance on its own.
13
Lam, Hoi-yee, and 林凱儀. "Voltage-current trajectory: a 2-dimensional approach to understand electrical load signatures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3890861X.
Повний текст джерела
14
Malisetty, Saideepthi. "Real-time optimal trajectory smoothing for Unmanned Aerial Vehicle in three dimensions." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/5038.
Повний текст джерелаАнотація:
This thesis presents a dynamically feasible and real-time trajectory path generation algorithm for unmanned aerial vehicles (UAVs) flying through a sequence of a random N number of waypoints (WPs) in three dimensions. Pontryagin’s minimum principle was used to show that the straight-line path segments connecting the sequence of waypoints are time optimal [1]. An algorithm was designed so that the total trajectory path length of a UAV is approximately equal to the straight-line path of the waypoints. The trajectory path obtained was also compared with the one-circle method, and it was found that the proposed method has less path length. Issues related to this algorithm are explained in detail. Simulation results show the efficiency of the method.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science
15
Willis, Jacob B. "Trajectory Generation and Tracking Control for Winged Electric Vertical Takeoff and Landing Aircraft." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/8952.
Повний текст джерелаАнотація:
The development of high-energy-density batteries, advanced sensor technologies, and advanced control algorithms for multirotor electric vertical takeoff and landing (eVTOL) unmanned aerial vehicles (UAVs) has led to interest in using these vehicles for a variety of applications including surveillance, package delivery, and even human transportation. In each of these cases, the ideal vehicle is one that can maneuver in congested spaces, but is efficient for traveling long distances. The combination of wings and vectored thrust make winged eVTOLs the obvious choice. However, these aircraft experience a much wider range of flight conditions that makes them challenging to model and control. This thesis contributes an aerodynamic model and a planning and control method for small, 1-2 m wingspan, winged eVTOLs. We develop the aerodynamic model based on first-principles, lumped-element aerodynamics, extending the lift and drag models to consider high-angle-of-attack flight conditions using models proposed in the literature. We present two methods for generating spline trajectories, one that uses the singular value decomposition to find a minimum-derivative polynomial spline, and one that uses B-splines to produce trajectories in the convex hull of a set of waypoints. We compare the quality of trajectories produced by both methods. Current control methods for winged eVTOL UAVs consider the vehicle primarily as a fixed-wing aircraft with the addition of vertical thrust used only during takeoff and landing. These methods provide good long-range flight handling but fail to consider the full dynamics of the vehicle for tracking complex trajectories. We present a trajectory tracking controller for the full dynamics of a winged eVTOL UAV in hover, fixed-wing, and partially transitioned flight scenarios. We show that in low- to moderate-speed flight, trajectory tracking can be achieved using a variety of pitch angles. In these conditions, the pitch of the vehicle is a free variable that we use to minimize the necessary thrust, and therefore energy consumption, of the vehicle. We use a geometric attitude controller and an airspeed-dependent control allocation scheme to operate the vehicle at a wide range of airspeeds, flight path angles, and angles of attack. We provide theoretical guarantees for the stability of the proposed control scheme assuming a standard aerodynamic model, and we present simulation results showing an average tracking error of 20 cm, an average computation rate of 800 Hz, and an 85% reduction in tracking error versus using a multirotor controller for low-speed flight.
16
Fernandez-Real, Marti. "Stochastic Model Predictive Control for Trajectory Planning." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285501.
Повний текст джерелаАнотація:
Trajectory planning constitutes an essential step for proper autonomous vehicles’performance. This work aims at defining and testing a stochastic approach providingsafe, length-optimal and comfortable trajectories accounting for road, model anddisturbance uncertainties. A Stochastic Model Predictive Control (SMPC) problemis formulated using a Linear Parameter Varying Bicycle Model, state-probabilisticconstraints and input constraints. The SMPC is transformed into a tractable quadraticoptimisation problem after assuming independent and gaussian uncertainties.The proposed trajectory planning methodology is intended to be implemented onlinein a Receding Horizon fashion in a real vehicle. Results are presented after computersimulatedtests have been carried out to study the influence of model uncertaintiesand SMPC parameters on the planned and executed trajectories in standard drivingsituations. Particularly, road crosswind is modelled, its effect on vehicles withdifferent steering characteristics is studied and it is considered for improved trajectoryplanning. The approach constitutes a promising method to provide robust trajectoriesto unmodeled errors reaching an equilibrium between conservativeness and quality ofthe solution.Banplanering utgör ett väsentligt steg för riktiga autonoma fordons prestanda.Syftet med detta arbete är att definiera och testa stokastiska strategier som gersäkra, optimala och bekväma banor som tar hänsyn till vägen, modelbrus ochosäkerheter. En stokastisk Model Predictive Control (SMPC) problem är formuleratmed hjälp av Linear Parameter Varying Bicycle Model, tillstånds-sannolikhetsbivillkoroch inmatningsbivillkor. SMPC transformeras till ett lätthanterlig kvadratiskoptimeringsproblem efter oberoende gaussfördelade osäkerheter antagits.Den föreslagna banplaneringsmetoden är avsedd att implementeras online meden Receding Horizon för ett riktigt fordon. Resultatet är presenterat efterdatorsimulerade experiment har blivit genomförda för att studera påverkan avmodelosäkerheter och SMPC parametrar på den planerade och genomförda banorför standard körsituationer. I synnerhet, är sidovind modellerat, dens effekt påfordon med olika styrkaraktäristik är studerad och är tagen hänsyn till för förbättradbanplanering. Tillvägagångssättet utgör en lovande metod för att tillhandahållarobusta banor för icke-model fel som når en jämvikt mellan konservativitet och kvalitethos lösningen.
17
Guan, Tianyi [Verfasser], and J. [Akademischer Betreuer] Beyerer. "Predictive energy-efficient motion trajectory optimization of electric vehicles / Tianyi Guan ; Betreuer: J. Beyerer." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1202111963/34.
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Janmohammadi, Siamak. "Classifying Pairwise Object Interactions: A Trajectory Analytics Approach." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801901/.
Повний текст джерелаАнотація:
We have a huge amount of video data from extensively available surveillance cameras and increasingly growing technology to record the motion of a moving object in the form of trajectory data. With proliferation of location-enabled devices and ongoing growth in smartphone penetration as well as advancements in exploiting image processing techniques, tracking moving objects is more flawlessly achievable. In this work, we explore some domain-independent qualitative and quantitative features in raw trajectory (spatio-temporal) data in videos captured by a fixed single wide-angle view camera sensor in outdoor areas. We study the efficacy of those features in classifying four basic high level actions by employing two supervised learning algorithms and show how each of the features affect the learning algorithms’ overall accuracy as a single factor or confounded with others.
19
Chen, Zhuo, and 陈卓. "A methodology for trajectory based learning and prediction of human motions in visual surveillance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47145985.
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Greinsmark, Vidar, and Tommy Hjertberg. "Finding an Optimal Trajectory for Autonomous Parking Under Uncertain Conditions." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254217.
Повний текст джерелаАнотація:
Path planning that considers accurate vehicle dynamics and obstacle avoidance is an important problem in the area of autonomous driving. This paper describes a method of implementing trajectory planning for autonomous parking in conditions where the starting point and the position of fixed obstacles are uncertain. The narrow spaces and complicated manoeuvres required for parking demands a lot from the trajectory planning algorithm. It needs to have the ability to accurately model vehicle dynamics and find an efficient way around obstacles. Having obstacles in the way of the parking vehicle makes this a nonconvex problem the goal can usually not be reached by travelling in a straight line and finding a perfect trajectory around them is generally not computationally tractable. This paper reviews a two tiered approach to solving this problem. First a rough path is found using a modified Rapidly-exploring Random Tree (RRT) algorithm called Forward-Backward RRT, which runs two treebuilding processes in parallel and constructs a feasible path from where they intersect. Using optimisation this is then improved into a trajectory that is at least a local optimum. These methods will be demonstrated to produce efficient and feasible trajectories that respects the dynamic constraints of the vehicle and avoids collisions.
21
Jie, Lu Billy, and Michael Bettar. "Trajectory Tracking, Formation Control and Obstacle Avoidance for Autonomous Ground Vehicles." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293838.
Повний текст джерелаАнотація:
The usage of autonomous ground vehicles is growingextensively. Therefore, it is important to gain a better understand-ing for the fundamentals of their communication network. Inthis paper, three important areas will be considered: Trajectorytracking, formation control and collision avoidance. Firstly,trajectory tracking is implemented for unicycles to direct them toa reference path. Secondly, formation control is examined for twoapproaches: A method based on virtual structure with a presettrajectory for unicycles and a method based on displacement forpoint agents. Finally, collision avoidance is incorporated withthe displacement-based controller. For this case, agents keepformation without colliding within formation and with staticobstacles in the workspace. The proposed controllers are verifiedthrough simulations in MATLAB.Användningen av autonoma markfordon har ökat kraftigt de senaste åren. Således är det viktigt att få en bättre förståelse för grunderna i deras kommunikationsnätverk. I detta projekt studeras tre essentiella områden: projektilspårning, formationshållning och undvikning av kollisioner. Först och främst implementeras projektilspårning för en enhjuling där den styrs mot en önskad projektilbana. Därefter betraktas formationshållning genom två metoder: Den första metoden handlar om virtuella strukturer med en förutbestämd bana för enhjulingar. Den andra metoden baseras på en förskjutningsbaserad regulator. Slutligen införs undvikning av kollisioner tillsammans med den förskjutningsbaserade regulatorn för att uppnå ett kollisionsundvikande robotsystem. Samtliga objektiv inom de tre områdena nås med varierande precision.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
22
Yu, Zitian. "Integrated Estimation and Motion Control for Electric Vehicles." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531778655719369.
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Parsons, Mark Andrew. "Electrode recording of field potentials along an axial trajectory: An approach for target localization improvement in deep brain stimulation implant surgery." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256391.
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Kwon, Kybeom. "A novel numerical analysis of Hall Effect Thruster and its application in simultaneous design of thruster and optimal low-thrust trajectory." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34777.
Повний текст джерелаАнотація:
Hall Effect Thrusters (HETs) are a form of electric propulsion device which uses external electrical energy to produce thrust. When compared to various other electric propulsion devices, HETs are excellent candidates for future orbit transfer and interplanetary missions due to their relatively simple configuration, moderate thrust capability, higher thrust to power ratio, and lower thruster mass to power ratio. Due to the short history of HETs, the current design process of a new HET is a largely empirical and experimental science, and this has resulted in previous designs being developed in a narrow design space based on experimental data without systematic investigations of parameter correlations. In addition, current preliminary low-thrust trajectory optimizations, due to inherent difficulties in solution procedure, often assume constant or linear performances with available power in their applications of electric thrusters. The main obstacles come from the complex physics involved in HET technology and relatively small amounts of experimental data. Although physical theories and numerical simulations can provide a valuable tool for design space exploration at the inception of a new HET design and preliminary low-thrust trajectory optimization, the complex physics makes theoretical and numerical solutions difficult to obtain. Numerical implementations have been quite extensively conducted in the last two decades. An investigation of current methodologies reveals that to date, none provide a proper methodology for a new HET design at the conceptual design stage and the coupled low-thrust trajectory optimization. Thus, in the first half of this work, an efficient, robust, and self-consistent numerical method for the analysis of HETs is developed with a new approach. The key idea is to divide the analysis region into two regions in terms of electron dynamics based on physical intuition. Intensive validations are conducted for existing HETs from 1 kW to 50 kW classes. The second half of this work aims to construct a simultaneous design optimization environment though collaboration with experts in low-thrust trajectory optimization where a new HET and associated optimal low-thrust trajectory can be designed simultaneously. A demonstration for an orbit raising mission shows that the constructed simultaneous design optimization environment can be used effectively and synergistically for space missions involving HETs. It is expected that the present work will aid and ease the current expensive experimental HET design process and reduce preliminary space mission design cycles involving HETs.
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Veeramani, Lekamani Sarangi. "Model Based Systems Engineering Approach to Autonomous Driving : Application of SysML for trajectory planning of autonomous vehicle." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254891.
Повний текст джерелаАнотація:
Model Based Systems Engineering (MBSE) approach aims at implementing various processes of Systems Engineering (SE) through diagrams that provide different perspectives of the same underlying system. This approach provides a basis that helps develop a complex system in a systematic manner. Thus, this thesis aims at deriving a system model through this approach for the purpose of autonomous driving, specifically focusing on developing the subsystem responsible for generating a feasible trajectory for a miniature vehicle, called AutoCar, to enable it to move towards a goal. The report provides a background on MBSE and System Modeling Language (SysML) which is used for modelling the system. With this background, an MBSE framework for AutoCar is derived and the overall system design is explained. This report further explains the concepts involved in autonomous trajectory planning followed by an introduction to Robot Operating System (ROS) and its application for trajectory planning of the system. The report concludes with a detailed analysis on the benefits of using this approach for developing a system. It also identifies the shortcomings of applying MBSE to system development. The report closes with a mention on how the given project can be further carried forward to be able to realize it on a physical system.Modellbaserade systemteknikens (MBSE) inriktning syftar till att implementera de olika processerna i systemteknik (SE) genom diagram som ger olika perspektiv på samma underliggande system. Detta tillvägagångssätt ger en grund som hjälper till att utveckla ett komplext system på ett systematiskt sätt. Sålunda syftar denna avhandling att härleda en systemmodell genom detta tillvägagångssätt för autonom körning, med särskild inriktning på att utveckla delsystemet som är ansvarigt för att generera en genomförbar ban för en miniatyrbil, som kallas AutoCar, för att göra det möjligt att nå målet. Rapporten ger en bakgrund till MBSE and Systemmodelleringsspråk (SysML) som används för modellering av systemet. Med denna bakgrund, MBSE ramverket för AutoCar är härledt och den övergripande systemdesignen förklaras. I denna rapport förklaras vidare begreppen autonom banplanering följd av en introduktion till Robot Operating System (ROS) och dess tillämpning för systemplanering av systemet. Rapporten avslutas med en detaljerad analys av fördelarna med att använda detta tillvägagångssätt för att utveckla ett system. Det identifierar också bristerna för att tillämpa MBSE på systemutveckling. Rapporten stänger med en omtale om hur det givna projektet kan vidarebefordras för att kunna realisera det på ett fysiskt system.
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Rust, Jack W. "Fuel optimal low thrust trajectories for an asteroid sample return mission." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FRust.pdf.
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Li, Sujuan. "Evaluating ambient fine particulate matter source regions in the Ohio River Valley Region." Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1070550479.
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Lopez, Colin. "Développement de sources haute-résolution de particules chargées grâce au contrôle de leur trajectoire par corrélation temps-position." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASP013.
Повний текст джерелаАнотація:
L’objet de cette thèse consiste en un développement de sources de particules chargées (ions ou électrons) dont la résolution en énergie, position et temps approchent les limites permises par les lois physiques. Le principe est d’utiliser la détection sensible en temps et position pour l’une des deux particules chargées corrélées, produites par photoionisation d’un nuage d’atomes froids, pour corriger en temps réel la trajectoire 3D de la particule partenaire afin d’en maîtriser le plus finement possible les caractéristiques spatio-temporelles. Le projet a pour but de créer, à partir de l’ionisation d’atomes de césium refroidis par laser, un nouveau type de source d’ions et d’électrons permettant une meilleure focalisation des faisceaux. Ce travail permet d’envisager de nouvelles expériences basées sur le contrôle de particules chargées uniques et ainsi de s’affranchir des effets de répulsion coulombienne dégradant les sources actuelles.Le but ultime étant d’arriver à déposer sur une surface un ion ou un électron avec des caractéristiques de vitesse, de position et de temps d’une précision jamais atteinte jusque-là. Des applications évidentes en implantation d’ions sont envisagées (lithographie). Les potentialités de ce dispositif en termes de correction de trajectoire ouvrent la voie d’un contrôle total du temps, de la position et de la vitesse d’arrivée des ions sur la cible. Une augmentation du flux est déjà envisagée, en vue d’application d’imagerie, en améliorant la vitesse de traitement en temps réel des informations temps/position des électrons.Le projet présenté ici s’inscrit désormais dans un projet plus vaste : une source d’ions basée sur ce principe est en cours d’étude avec la société Orsay Physics spécialisée dans la conception et la fabrication de colonnes à faisceaux d’ions focalisés (FIB)The topic of this thesis is the development of charged particle sources (ions or electrons) whose energy resolution, position and time approach the limits permitted by physic laws. The idea is to use the sensitive detection in time and position for one of the two correlated charged particles produced by the photoionization of an cold atoms cloud, to correct in real time the 3D trajectory of the particle partner to know as thinly as possible its spatiotemporal characteristics. The project aims to create, from the ionization of cesium atoms cooled by laser, a new type of ion or electron source allowing a better beam. We can now consider new experiences based on the unique control of charged particles and thus overpass the Coulomb repulsion effects that degrades the common sources.The ultimate goal is to be able to depose an ion or an electron on a surface with the speed, position and time characteristics never reached. Some applications in ions implantation are expected (lithography). In terms of trajectory correction it could allow a full control of time, position and velocity of ions reaching the target. A further increase of the flow is already considered for purposes of imaging (real-time processing of time-position data). The project presented here is now part of a larger project: an ion source based on this concept is under study with the Orsay Physics Company specialized in the design and manufacture of columns Focused ion beam (FIB)
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Manathunga, Madushanka. "Impact of Electronic State Mixing on the Photoisomerization Timescale of Natural and Synthetic Molecular Systems." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1541548724939953.
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Mensing, Felicitas. "Optimal energy utilization in conventional, electric and hybrid vehicles and its application to eco-driving." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-01071383.
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The transportation sector has been identified as one of many sources of today's energetic and environmental problems. With constantly increasing numbers of vehicles on the road, non-renewable fossil fuels are becoming scarce and expensive. In addition, due to the pollutant emissions of internal combustion engines, the transportation sector is a major producer of greenhouse gas emissions. To resolve these problems researcher are looking for technological solutions, such as more efficient components and alternative drive train technologies, on one hand. On the other hand, work is being done to ensure the most efficient utilization of available technological resources. Eco driving is one way to immediately reduce a driver's energy consumption. In this thesis the potential gains of eco driving for passenger vehicles will be discussed. The main objective of this work is to, first, identify and compare drive train specific, optimal vehicle operation. Secondly, the effect of real-life constraints on potential gains of eco driving is evaluated. In addition, an approach to integrate mathematical optimization algorithms in an advanced driver assist system for eco driving is proposed. Physical vehicle models are developed for three representative vehicles: the conventional, electric and power-split hybrid vehicle. Using real-life and standard drive cycles a baseline mission is defined by specifying trip and road constraint. Applying the dynamic programming algorithms the trajectory optimization problem is solved, minimizing energy consumption for the trip. The effect of traffic on potential gains of eco driving is discussed, considering a vehicle following situation. Integrating emission constraints in the optimization algorithm the environmental advantages of eco driving are discussed. Finally, the developed algorithms were integrated in a driver assist system. Experimental tests on a driving simulator were used to verify the effectiveness of the system, as well as driver acceptance.
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Arslan, Ali Erkin. "Range Parameterized Bearings-only Tracking Using Particle Filter." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614888/index.pdf.
Повний текст джерелаАнотація:
In this study, accurate target tracking for bearings-only tracking problem is investigated. A new tracking filter for this nonlinear problem is designed where both range parameterization and Rao-Blackwellized (marginalized) particle filtering techniques are used in a Gaussian mixture formulation to track both constant velocity and maneuvering targets. The idea of using target turn rate in the state equation in such a way that marginalization is possible is elaborated. Addition to nonlinear nature, unobservability is a major problem of bearings-only tracking. Observer trajectory generation to increase the observability of the bearings-only tracking problem is studied. Novel formulation of observability measures based on mutual information between the state and the measurement sequences are derived for the problem. These measures are used as objective functions to improve observability. Based on the results obtained better understanding of the required observer trajectory for accurate bearings-only target tracking is developed.
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Almilaji, Karam N. "Fabricating Superhydrophobic and Superoleophobic Surfaces with Multiscale Roughness Using Airbrush and Electrospray." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4460.
Повний текст джерелаАнотація:
Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag reduction, anti-icing, anti-fogging, energy conservation, noise reduction, and self-cleaning. In fact, the same concept could be applied in designing and producing surfaces that repel organic contaminations (e.g. low surface tension liquids). However, superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided. In this study, simple, cost-effective and potentially scalable techniques, i.e., airbrush and electrospray, were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness. Different types of silicon dioxide were utilized in this work to in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability. The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure, multiscale surface roughness, and low surface energy obtained from chemically treating the fabricated surfaces. In addition to that, the experimental observations regarding producing textured surfaces in mask-assisted electrospray were further validated by simulating the actual working conditions and geometries using COMSOL Multiphysics.
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Figueroa, Shana Suzanne. "Ion scattering in a self-consistent cylindrical plasma sheath." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-051006-112304/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: orbital trajectory, ion collection, turning point method, spherical probes, turning angle, ion scattering, cylindrical probes. Includes bibliographical references (p.60-63).
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Soldera, John. "Detecção de movimentos suspeitos em seqüências de vídeo." Universidade do Vale do Rio do Sinos, 2007. http://www.repositorio.jesuita.org.br/handle/UNISINOS/2250.
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Made available in DSpace on 2015-03-05T13:59:41Z (GMT). No. of bitstreams: 0
Previous issue date: 28Hewlett-Packard Brasil Ltda
É proposto neste trabalho novas técnicas para automatizar processos em vigilância eletrônica. A entrada (input) do algoritmo descrito são trajetórias das pessoas capturadas de seqüências de vídeo filmadas, as quais são utilizadas para definição de padrões de comportamentos de pedestres. O modelo proposto se baseia em dois critérios para a definição de comportamentos como usuais ou não-usuais: a ocupação espacial e as relações entre as pessoas. O critério de ocupação espacial inclui um determinado tempo de treinamento onde a cena é avaliada para gerar uma base de dados que contabiliza a ocupação espacial em cada região da cena. Através desta base de dados, novas trajetórias são classificadas como usuais ou não-usuais. As trajetórias usuais são aquelas coerentes com o banco de dados gerado pelo treinamento, correspondendo às áreas mais ocupadas, enquanto que as trajetórias não-usuais são aquelas nas quais andaram em regiões de baixa ocupação espacial. O critério das relações interpessoais utiliza Diagramas de V
It’s proposed in this work new techniques to automate processes in electronic surveillance systems. The input of the algorithm described is the trajectories of people captured from real filmed sequences, which are used to define pedestrian behavior patterns. The proposed model is based in two criteria to define behaviors as usual or unusual: spatial occupancy and relations among people. The spatial occupancy criterion includes a certain training period when the scene is evaluated in order to generate a database which accounts for the spatial occupancy in each scene region. Through this database, new trajectories are classified as usual or unusual. Usual trajectories are those coherent with the training database, corresponding to the most occupied areas; whereas unusual trajectories are those that occur in low spatial occupancy regions. The interpersonal relation analysis criterion employs Voronoi Diagrams in order to evaluate a set of parameters (such as distance between neighbors and other psychosocial char
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Peddle, Iain K. "Acceleration based manoeuvre flight control system for unmanned aerial vehicles." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1172.
Повний текст джерелаАнотація:
Thesis (PhD (Electrical and Electronic Engineering))--Stellenbosch University, 2008.A strategy for the design of an effective, practically feasible, robust, computationally efficient autopilot for three dimensional manoeuvre flight control of Unmanned Aerial Vehicles is presented. The core feature of the strategy is the design of attitude independent inner loop acceleration controllers. With these controllers implemented, the aircraft is reduced to a point mass with a steerable acceleration vector when viewed from an outer loop guidance perspective. Trajectory generation is also simplified with reference trajectories only required to be kinematically feasible. Robustness is achieved through uncertainty encapsulation and disturbance rejection at an acceleration level. The detailed design and associated analysis of the inner loop acceleration controllers is carried out for the case where the airflow incidence angles are small. For this case it is shown that under mild practically feasible conditions the inner loop dynamics decouple and become linear, thereby allowing the derivation of closed form pole placement solutions. Dimensional and normalised non-dimensional time variants of the inner loop controllers are designed and their respective advantages highlighted. Pole placement constraints that arise due to the typically weak non-minimum phase nature of aircraft dynamics are developed. A generic, aircraft independent guidance control algorithm, well suited for use with the inner loop acceleration controllers, is also presented. The guidance algorithm regulates the aircraft about a kinematically feasible reference trajectory. A number of fundamental basis trajectories are presented which are easily linkable to form complex three dimensional manoeuvres. Results from simulations with a number of different aircraft and reference trajectories illustrate the versatility and functionality of the autopilot. Key words: Aircraft control, Autonomous vehicles, UAV flight control, Acceleration control, Aircraft guidance, Trajectory tracking, Manoeuvre flight control.
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Ferdeen, Mats. "Reducing Energy Consumption Through Image Compression." Thesis, Linköpings universitet, Datorteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134335.
Повний текст джерелаАнотація:
The energy consumption to make the off-chip memory writing and readings are aknown problem. In the image processing field structure from motion simpler compressiontechniques could be used to save energy. A balance between the detected features suchas corners, edges, etc., and the degree of compression becomes a big issue to investigate.In this thesis a deeper study of this balance are performed. A number of more advancedcompression algorithms for processing of still images such as JPEG is used for comparisonwith a selected number of simpler compression algorithms. The simpler algorithms canbe divided into two categories: individual block-wise compression of each image andcompression with respect to all pixels in each image. In this study the image sequences arein grayscale and provided from an earlier study about rolling shutters. Synthetic data setsfrom a further study about optical flow is also included to see how reliable the other datasets are.Energikonsumtionen för att skriva och läsa till off-chip minne är ett känt problem. Inombildbehandlingsområdet struktur från rörelse kan enklare kompressionstekniker användasför att spara energi. En avvägning mellan detekterade features såsom hörn, kanter, etc.och grad av kompression blir då en fråga att utreda. I detta examensarbete har en djuparestudie av denna avvägning utförts. Ett antal mer avancerade kompressionsalgoritmer förbearbetning av stillbilder som tex. JPEG används för jämförelse med ett antal utvaldaenklare kompressionsalgoritmer. De enklare algoritmerna kan delas in i två kategorier:individuell blockvis kompression av vardera bilden och kompression med hänsyn tillsamtliga pixlar i vardera bilden. I studien är bildsekvenserna i gråskala och tillhandahållnafrån en tidigare studie om rullande slutare. Syntetiska data set från ytterligare en studie om’optical flow’ ingår även för att se hur pass tillförlitliga de andra dataseten är.
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Mustaree, Shayla. "The •OH scavenging effect of bromide ions on the yield of H[subscript 2]O[subscript 2] in the radiolysis of water by [superscript 60]Co γ-rays and tritium β-particles at room temperature : a Monte Carlo simulation study". Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8183.
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Abstract: Monte Carlo simulations were used here to compare the radiation chemistry of pure water and aqueous bromide solutions after irradiation with two different types of radiation, namely, tritium β-electrons (~7.8 keV) and [superscript 60]Co γ-rays/fast electron (~1 MeV) or high energy protons. Bromide ions (Br-) are known to be selective scavengers of hydroxyl radicals •OH precursors of hydrogen peroxide H[subscript 2]O[subscript 2]. These simulations thus allowed us to determine the yields (or G-values) of H[subscript 2]O[subscript 2] in the radiolysis of dilute aqueous bromide solutions by the two types of radiations studied, the first with low linear energy transfer (LET) (~0.3 keV/μm) and the second with high LET (~6 keV/μm) at 25 °C. This study was carried out under a wide range of Br- concentrations both in the presence and the absence of oxygen. Simulations clearly showed that irradiation by tritium β-electrons favored a clear increase in G(H[subscript 2]O[subscript 2]) compared to [superscript 60]Co γ-rays. We found that these changes could be related to differences in the initial spatial distributions of radiolytic species (i.e., the structure of the electron tracks, the low-energy β-electrons of tritium depositing their energy as cylindrical “short tracks” and the energetic Compton electrons produced by γ-radiolysis forming mainly spherical “spurs”). Moreover, simulations also showed that the presence of oxygen, a very good scavenger of hydrated electrons (e-[subscript aq]) and H• atoms on the 10[superscript-7] s time scale (i.e., before the end of spur expansion), protected H[subscript 2]O[subscript 2] from further reactions with these species in the homogeneous stage of radiolysis. This protection against e-[subscript aq] and H• atoms therefore led to an increase in the H[subscript 2]O[subscript 2] yields at long times, as seen experimentally. Finally, for both deaerated and aerated solutions, the H[subscript 2]O[subscript 2] yield in tritium β-radiolysis was found to be more easily suppressed than in the case of cobalt-60 γ-radiolysis, and interpreted by the quantitatively different chemistry between short tracks and spurs. These differences in the scavengeability of H[subscript 2]O[subscript 2] precursors in passing from low-LET [superscript 60]Co γ-ray to high-LET tritium β-electron irradiation were in good agreement with experimental data, thereby lending strong support to the picture of tritium-β radiolysis in terms of short tracks of high local LET.Résumé: Les simulations Monte Carlo constituent une approche théorique efficace pour étudier la chimie sous rayonnement de l'eau et des solutions aqueuses. Dans ce travail, nous avons utilisé ces simulations pour comparer l’action de deux types de rayonnement, à savoir, le rayonnement γ de [indice supérieur 60]Co (électrons de Compton ~1 Me V) et les électrons β du tritium (~ 7,8 keV), sur la radiolyse de l’eau et des solutions aqueuses diluées de bromure. Les ions Br- sont connus comme d’excellents capteurs des radicaux hydroxyles •OH, précurseurs du peroxyde d’hydrogène H[indice inférieur 2]O[indice inférieur 2]. Les simulations Monte Carlo nous ont donc permis de déterminer les rendements (ou valeurs G) de H[indice inférieur 2]O[indice inférieur 2] à 25 °C pour les deux types de rayonnements étudiés, le premier à faible transfert d'énergie linéaire (TEL) (~0,3 keV/μm) et le second à haut TEL (~6 keV/μm). L’étude a été menée pour différentes concentrations d’ions Br-, à la fois en présence et en absence d'oxygène. Les simulations ont montré que l’irradiation par les électrons β du tritium favorisait nettement la formation de H[indice inférieur 2]O[indice inférieur 2] comparativement aux rayons γ du cobalt. Ces changements ont pu être reliés aux différences qui existent dans les distributions spatiales initiales des espèces radiolytiques (i.e., la structure des trajectoires d'électrons, les électrons β du tritium déposant leur énergie sous forme de «trajectoires courtes» de nature cylindrique, et les électrons Compton produits par la radiolyse γ formant principalement des «grappes» de géométrie plus ou moins sphérique). Les simulations ont montré également que la présence d'oxygène, capteur d’électrons hydratés et d’atomes H• sur l'échelle de temps de ~10[indice supérieur -7] s (i.e., avant la fin des grappes), protégeait H[indice inférieur 2]O[indice inférieur 2] d’éventuelles réactions subséquentes avec ces espèces. Une telle «protection» conduit ainsi à une augmentation de G(H[indice inférieur 2]O[indice inférieur 2]) à temps longs. Enfin, en milieu tant désaéré qu’aéré, les rendements en H[indice inférieur 2]O[indice inférieur 2] obtenus lors de la radiolyse par les électrons β du tritium ont été trouvés plus facilement supprimés que lors de la radiolyse γ. Ces différences dans l’efficacité de capture des précurseurs de H[indice inférieur 2]O[indice inférieur 2] ont été interprétées par les différences quantitatives dans la chimie intervenant dans les trajectoires courtes et les grappes. Un excellent accord a été obtenu avec les données expérimentales existantes.
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Fan, Chi-Hsiang. "MONTE CARLO SIMULATION OF ELECTRON TRAJECTORY AND DESIGN OF AN ELECTRON BEAM POSITION MONITOR SYSTEM FOR MULTIPLE ELECTRON BEAM DIRECT-WRITE LITHOGRAPHY." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-3007200822593100.
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Yves, Alain Bernard. "Applications of Posmom in Quantum Chemistry." Phd thesis, 2010. http://hdl.handle.net/1885/49402.
Повний текст джерелаАнотація:
The context of this Thesis is a new approach to the electron correlation problem based on two ideas. The first idea states that the correlation energy can be approximated simply by a linear operator which contains information about both the position, r, and the momentum, p, of an electron, i.e. a phase-space operator. The second idea proposes the use of two-electron operators, as the electron correlation occurs between pairs of electrons. The combination of these two ideas gave birth to Intracule Function Theory, where intracules are two-electron distributions. To include position and momentum information, Intracule Functional Theory uses the Wigner distribution, a quasi-phase-space distribution, as a true phase-space distribution does not exist because of the Heisenberg Uncertainty Principle. In this Thesis, we study two new phase-space variables, the one-particle Posmom variable, s=r.p, and the two-particle Posmom intracule variable, x=(r1- r2).(p1- p2), and their respective distributions, the Posmom density, S(s), and the Posmom intracule, X(x). The one-particle Posmom variable, s, and its associated operator are known in physics and have been used, for example, in the development of scattering theory. However, they have never been used in quantum chemistry and we present, for the first time, the quantum distribution S(s) for several relevant systems. The two-particle equivalent variable, x, has been introduced previously in Intracule Functional Theory and an intracule, based on the Wigner distribution, has been proposed; the Dot intracule D(x). Within Intracule Functional Theory, we use the Dot intracule to calculate the correlation energy of small atoms and molecules. Furthermore, we derive the exact two-particle Posmom operator and its exact distribution, and show that the Dot intracule appears as an approximation of the exact Posmom intracule. The Posmom variables, s and x, are dot products between position and momentum vectors and contain information about both the position and the momentum of one or two electrons. Furthermore, the associated Posmom operators are quantum mechanical observables, and thus respect the Heisenberg Uncertainty Principle. We show that they are connected to types of electron trajectories and give us new information about the behaviour of electrons. They could form the basis of a new type of spectroscopy. This Thesis introduces the first applications of Posmom in quantum chemistry. We first review the theory of quantum mechanics, quantum chemistry and Intracule Functional Theory. We then present an entire development of the Posmom intracule X(x) by starting from the simple and well known spherically averaged position and momentum densities, followed by the new Posmom density S(s) and the Wigner-based Dot intracule D(x).
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Robin, Abel. "Trajectory and channeling effects in the scattering of ions off a metal surface - Probing the electronic density corrugation at a surface by grazing axial ion channeling." Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003112519.
Повний текст джерелаАнотація:
The presented work investigates planar and axial channeling effects in ion-surface collisions. Therefore, energy loss and charge state distributions depending on the crystalline surface direction are recorded and analyzed. Several additional scattering parameters, like the primary energy, the outgoing charge state, the scattering angle, and the angle of incidence are varied. Multi-peak structures in the energy spectra are observed under axial channeling conditions and attributed to different trajectory classes. Using combined trajectory and inelastic energy loss calculations we are able to unambiguously assign the different peaks in the energy spectra to the different types of trajectories found in the calculations. By this, we investigate the electronic density corrugation at different metal surfaces. Die vorliegende Arbeit untersucht den Einfluß von axialem und planarem Channeling auf den Energieverlust von oberflächengestreuten Ionen. Es werden Energieverlustspektren und Ladungsverteilungen in Abhängigkeit der Parameter Primärenergie, gestreuter Ladungszustand, Streuwinkel, Einfallswinkel und der azimuthalen Ausrichtung der Oberfläche gemessen. Im Fall von axialem Channeling beobachten wir in den Energiespektren eine Multi-Peak Struktur. Diese läßt sich auf unterschiedliche Teilchentrajektorien zurückführen. Zusammen mit theoretischen Berechnungen des inelastischen Energieverlustes kann eine eindeutige Zuordnung zwischen dem gemessenen Energieverlust und der dazugehörigen Trajektorienart gemacht werden. Diese Technik erlaubt es uns, die elektronische Dichtekorrugation an Oberflächen zu studieren.
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Rowell, Timothy. "Obstacle avoidance and trajectory optimisation for a power line inspection robot." Thesis, 2012. http://hdl.handle.net/10413/9640.
Повний текст джерелаАнотація:
This dissertation presents the research, development and application of trajectory creation, obstacle avoidance and trajectory optimisation methods for an existing serial manipulator power line inspection robot (PLIR). The obstacle avoidance implementation allows the robot to navigate around an obstacle obstructing its navigation along the line. The algorithm generated end effector
trajectory waypoints autonomously based on bounding box obstacle descriptions in Cartesian space, and connected them with a fifth order basis-spline end effector trajectory command. The trajectories were created taking into account the dynamic torque and velocity constraints of the
robot while ignoring non-linearities. Performance was inspected and evaluated in a simulated workspace environment. The trajectory optimisation was designed to maximise the robot’s operating range, with constraints
on the battery power supply, by minimising charge consumed during obstacle avoidance trajectories. The temporal components of the basis-spline trajectories were optimised by minimising a timeenergy type of cost function subject to the dynamic constraints of the robot. Cost function analyses are presented for a simple frictionless robot model based on the recursive Newton-Euler method,
and for a more realistic model including viscous, Coulomb and static friction as well as gearbox backlash. It is shown that the Nelder-Mead simplex method was appropriate for optimisation. For representative trajectories that were studied, the optimiser was capable of finding global minima
with satisfactory speed and accuracy in simulation. The validity of trajectory optimisation with regard to the cost function behaviour was confirmed. This was based on experiments carried out on the robot hardware in the laboratory, examining the predicted and actual actuator current profiles. The engineering design and implementation of hardware and software for the base station and on-board system is presented, together with the layout of the PLIR’s control system and PID (proportional-integral-derivative) controller design. Trajectory commands are sent from the base station to the robot via Wi-Fi for execution. Furthermore, live video feed from the robot can be sent to the ground station computer. Furthermore, high voltage testing of the PLIR showed that
the engineering design of the robot and communication platform is robust.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.
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Cheng, Shih-Siang, and 程智祥. "Electronic Measuring System Applied to the Trajectory Analysis of the Water-Propelled Rocket." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/72995454979740022564.
Повний текст джерелаАнотація:
碩士逢甲大學
航空工程所
92
The purpose of this paper is to propose a practical way to compute the accurate trajectory of the water-propelled rocket at any given firing angles. The maximum velocity and drag coefficient have to be known before solving the equations of motion of the water-propelled rocket. Then, a set of velocity measuring system equipped with an electronic sensing timer and a compatible launching device is developed to measure the maximum velocity of the water-propelled rocket under various combinations of water volumes and air pressures .Another system equipped with the same electronic sensing timer is designed to obtain the drag coefficient of zero-angle-of-attack of the water-propelled rocket. The drag coefficient is verified by a vertical launching test. The trajectories and ranges of the water-propelled rocket under various combinations of water volumes and air pressures are calculated by MATLAB coding program. The calculated results should be corrected by the firing data and the correction factors (so-called form factors) are generated. Form factor is actually the function of firing angle, and three from factors at three specific firing angles are found in this research. Finally, the trajectories and ranges of the water-propelled rocket at any given firing angles can be calculated with their form factors obtained by linear interpolation criteria.
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Silva, Gonçalo Barros da. "Airborne Wind Energy Systems: Modelling, Simulation and Trajectory Control." Master's thesis, 2018. https://repositorio-aberto.up.pt/handle/10216/114026.
Повний текст джерелаАнотація:
In this dissertation, we address the generation of electrical power using Airborne Wind Energy Systems, comprising a kite connected through a tether to a generator on the ground. We do simulations of the kite model, both in 2D and 3D. Then we design a controller to steer the kite to follow a pre-defined periodic path, which includes a production mode, a tether retrieval mode, and a safe mode capable of handling wind gusts. Finally, we desing a controller based on a nonlinear guidance logic for trajectory tracking and compare the results.
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Silva, Gonçalo Barros da. "Airborne Wind Energy Systems: Modelling, Simulation and Trajectory Control." Dissertação, 2018. https://repositorio-aberto.up.pt/handle/10216/114026.
Повний текст джерелаАнотація:
In this dissertation, we address the generation of electrical power using Airborne Wind Energy Systems, comprising a kite connected through a tether to a generator on the ground. We do simulations of the kite model, both in 2D and 3D. Then we design a controller to steer the kite to follow a pre-defined periodic path, which includes a production mode, a tether retrieval mode, and a safe mode capable of handling wind gusts. Finally, we desing a controller based on a nonlinear guidance logic for trajectory tracking and compare the results.
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Shimmin, Rogan. "Trajectory design for a very-low-thrust lunar mission." Thesis, 2013. http://hdl.handle.net/2440/80842.
Повний текст джерелаАнотація:
The University of Stuttgart is conducting a research program to build a succession of small satellites. The ultimate goal of this program is to build and launch a craft named Lunar Mission BW-1 (after the federal state that Stuttgart is situated in, Baden-Wurttemberg) into lunar orbit, for eventual impact with the Moon. As with the majority of space missions, launch cost is a severely limiting factor so it is necessary to carefully plan the trajectory before launch, to ensure lunar capture and minimise the amount of fuel needed by the spacecraft. This thesis outlines work conducted to find a robust fuel-optimal trajectory for Lunar Mission BW-1 to reach the Moon. Several unique aspects of this craft require a novel approach to that optimisation. Firstly, the spacecraft uses a new low-cost propulsion system, severely limiting manoeuvrability and accessibility of transfer trajectories. Secondly, to reduce the mass and complexity of moving parts, the solar panels are fixed to the body; consequently, the craft must rotate itself to point its solar panels towards the Sun to recharge. No thrusting can occur during this time. This magnifies the effect of the third design decision, which is to restrict the dry mass of the craft by giving it very little on-board power storage. After approximately an hour of accelerating it is expected to need to coast for several hours to recharge its batteries, resulting in a relatively high frequency stop-go-stop thrust profile. Due to these constraints, the trajectory optimisation is one of the most complex ever attempted. Since the craft will be built and launched, many simplifications made in purely theoretical studies could not be utilised, such as neglecting the weaker forces acting on the spacecraft in cis-lunar space. The very low thrust results in very long transfer times, during which even small magnitude forces acting on the spacecraft can significantly perturb its trajectory. However, including these forces creates non-linearities in the equations of motion associated with spacecraft trajectories, limiting the optimisation methods that could be used, and increasing computational complexity. Optimisation methods for low-thrust spacecraft trajectories have been the subject of much research, but most studies conclude that knowledge is still lacking in this area. Furthermore, many optimisation methods investigated in existing literature are incompatible with the intermittent thrust profile required by the Lunar Mission BW-1 thrusters. For this reason it was necessary to thoroughly review available optimisation methods and determine which may be adapted to this scenario. The resulting optimisation method was applied to the Lunar Mission BW-1 scenario to determine an efficient thrusting profile that will get the craft to the Moon. It was found that very few established optimisation algorithms can support the number of variables required for such a complex, long duration trajectory. The Sparse Optimal Control Software (SOCS) marketed by The Boeing Corporation was used via an interface developed at the University of Stuttgart called the the Graphical Environment for Simulation and Optimisation (GESOP). Due to unknown constraints such as launch date, the phases defined by the mission architecture were modelled and optimised independently. This approach allows mission planning flexibility while still providing reliable estimates for optimal fuel use, mission duration and power limitations. A trajectory is presented for each of the phases, ascending from the intial geosynchronous transfer orbit (GTO) to the eventual low lunar orbit (LLO). The resulting science phase is propagated forward in time to ensure orbital lifetime meets the mission requirements. Recommendations are subsequently made for the continuing development of the mission architecture. The primary outcome of this study is a procedure for developing an operational trajectory for Lunar Mission BW-1 after launch details are known. Given the current mission architecture and assumed launch details, the thermal arcjet requires 1205 hours (50.2 days) of operation while consuming 93 kg of ammonia propellant, and the pulsed plasma thrusters require 29177 hours (3.3 years) of operation while consuming 19 kg propellant. Power constraints were not found to be mission limiting for the current spacecraft configuration. Consequently, although the laboratory testing burden on the PPTs is already quite heavy, it is recommended that the mission architecture be adjusted to shorten arcjet phases and lengthen PPT phases. Furthermore, this project found that the optimisation package SOCS was the best commercially available option for low-thrust trajectory optimisation, but that it would benefit greatly by adaptation to a parallel shooting algorithm that may be distributed amongst multiple computer processors.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2013
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Robin, Abel [Verfasser]. "Trajectory and channeling effects in the scattering of ions off a metal surface : probing the electronic density corrugation at a surface by grazing axial ion channeling / von Abel Robin." 2003. http://d-nb.info/970387180/34.
Повний текст джерела