Дисертації з теми "Linear camera"
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1
Lawn, Jonathan Marcus. "Linear methods for camera motion recovery." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313704.
2
Kim, Jae-Hak, and Jae-Hak Kim@anu edu au. "Camera Motion Estimation for Multi-Camera Systems." The Australian National University. Research School of Information Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20081211.011120.
Анотація:
The estimation of motion of multi-camera systems is one of the most important tasks in computer vision research. Recently, some issues have been raised about general camera models and multi-camera systems. Using many cameras as a single camera is studied [60], and the epipolar geometry constraints of general camera models is theoretically derived. Methods for calibration, including a self-calibration method for general camera models, are studied [78, 62]. Multi-camera systems are an example of practically implementable general camera models and they are widely used in many applications nowadays because of both the low cost of digital charge-coupled device (CCD) cameras and the high resolution of multiple images from the wide field of views. To our knowledge, no research has been conducted on the relative motion of multi-camera systems with non-overlapping views to obtain a geometrically optimal solution. ¶
In this thesis, we solve the camera motion problem for multi-camera systems by using linear methods and convex optimization techniques, and we make five substantial and original contributions to the field of computer vision. First, we focus on the problem of translational motion of omnidirectional cameras, which are multi-camera systems, and present a constrained minimization method to obtain robust estimation results. Given known rotation, we show that bilinear and trilinear relations can be used to build a system of linear equations, and singular value decomposition (SVD) is used to solve the equations. Second, we present a linear method that estimates the relative motion of generalized cameras, in particular, in the case of non-overlapping views. We also present four types of generalized cameras, which can be solvable using our proposed, modified SVD method. This is the first study finding linear relations for certain types of generalized cameras and performing experiments using our proposed linear method. Third, we present a linear 6-point method (5 points from the same camera and 1 point from another camera) that estimates the relative motion of multi-camera systems, where cameras have no overlapping views. In addition, we discuss the theoretical and geometric analyses of multi-camera systems as well as certain critical configurations where the scale of translation cannot be determined. Fourth, we develop a global solution under an L∞ norm error for the relative motion problem of multi-camera systems using second-order cone programming. Finally, we present a fast searching method to obtain a global solution under an L∞ norm error for the relative motion problem of multi-camera systems, with non-overlapping views, using a branch-and-bound algorithm and linear programming (LP). By testing the feasibility of LP at the earlier stage, we reduced the time of computation of solving LP.¶
We tested our proposed methods by performing experiments with synthetic and real data. The Ladybug2 camera, for example, was used in the experiment on estimation of the translation of omnidirectional cameras and in the estimation of the relative motion of non-overlapping multi-camera systems. These experiments showed that a global solution using L∞ to estimate the relative motion of multi-camera systems could be achieved.
3
Uudelepp, Oscar. "Positional calibration methods for linear pipetting robot." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414666.
Анотація:
This thesis aims to investigate and develop two positional calibration methods that can be applied to a linear pipetting robot. The goal of the calibration is to detect displacements that have been made to objects that are located in the the robot’s reference system and try to estimate their new position. One of the methods utilizes the pressure system that is mounted on the robot’s arm. The pressure system was able to detect surfaces by blowing air through a pipette against desired surfaces. Positional information of targeted objects are acquired by using the surface detection feature against an extruded square landmark that acts as a reference for estimating displacements. The other method uses a barcode scanning camera by using its images to detect and retrieve positional information on Aruco markers. Estimation of the targeted object is done by tracking the movement of the Arucos position and orientation. Tests were made in order to analyse the performance of both methods and to verify that the requirement of 0.1 mm accuracy and precision could be obtained. The tests were limited to analysing the methods performance on stationary targets to guarantee that the methods did not detect incorrect displacements. It was found that the camera method could fulfill the requirement when it came to estimating XY-coordinates by using multiple images and placing the Aruco marker within a reasonable distance to the targeted object. However, the camera method was not accurate when it came to estimating the Z-coordinates of objects. As for the pressure method, it was able to fulfill the requirement when it came to estimating Z-coordinates, but its ability to estimate the XY-coordinates of an object was not sufficient. A recommendation would be combine both methods so that they can compensate each other by using the camera method for estimating the XY-coordinates and the pressure method for estimating the Z-coordinates.
4
Anwar, Qaiser. "Optical Navigation by recognition of reference labels using 3D calibration of camera." Thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-18453.
Анотація:
In this thesis a machine vision based indoor navigation system is presented. This is achieved by using rotationally independent optimized color reference labels and a geometrical camera calibration model which determines a set of camera parameters. All reference labels carry one byte of information (0 to 255), which can be designed for different values. An algorithm in Matlab has been developed so that a machine vision system for N number of symbols can recognize the symbols at different orientations. A camera calibration model describes the mapping between the 3-D world coordinates and the 2-D image coordinates. The reconstruction system uses the direct linear transform (DLT) method with a set of control reference labels in relation to the camera calibration. The least-squares adjustment method has been developed to calculate the parameters of the machine vision system. In these experiments it has been demonstrated that the pose of the camera can be calculated, with a relatively high precision, by using the least-squares estimation.
5
Ben-Naser, Abdusalam. "Measurement of range of motion of human finger joints, using a computer vision system." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/12531.
Анотація:
Assessment of finger range of motion (ROM) is often required for monitoring the effectiveness of rehabilitative treatments and for evaluating patients' functional impairment. There are several devices which are used to measure this motion, such as wire tracing, tracing onto paper and mechanical and electronic goniometry. These devices are quite cheap, excluding electronic goniometry; however the drawbacks of these devices are their lack of accuracy and the time- consuming nature of the measurement process. The work described in this thesis considers the design, implementation and validation of a new medical measurement system utilized in the evaluation of the range of motion of the human finger joints instead of the current measurement tools. The proposed system is a non-contact measurement device based on computer vision technology and has many advantages over the existing measurement devices. In terms of accuracy, better results are achieved by this system, it can be operated by semi-skilled person, and is time saving for the evaluator. The computer vision system in this study consists of CCD cameras to capture the images, a frame-grabber to change the analogue signal from the cameras to digital signals which can be manipulated by a computer, Ultra Violet light (UV) to illuminate the measurement space, software to process the images and perform the required computation, a darkened enclosure to accommodate the cameras and UV light and to shield the working area from any undesirable ambient light. Two calibration techniques were used to calibrate the cameras, Direct Linear Transformation and Tsai. A calibration piece that suits this application was designed and manufactured. A steel hand model was used to measure the fingers joint angles. The average error from measuring the finger angles using this system was around 1 degree compared with 5 degrees for the existing used techniques.
6
Rydström, Daniel. "Calibration of Laser Triangulating Cameras in Small Fields of View." Thesis, Linköpings universitet, Datorseende, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-94210.
Анотація:
A laser triangulating camera system projects a laser line onto an object to create height curveson the object surface. By moving the object, height curves from different parts of the objectcan be observed and combined to produce a three dimensional representation of the object.The calibration of such a camera system involves transforming received data to get real worldmeasurements instead of pixel based measurements. The calibration method presented in this thesis focuses specifically on small fields ofview. The goal is to provide an easy to use and robust calibration method that can complementalready existing calibration methods. The tool should get as good measurementsin metric units as possible, while still keeping complexity and production costs of the calibrationobject low. The implementation uses only data from the laser plane itself making itusable also in environments where no external light exist. The proposed implementation utilises a complete scan of a three dimensional calibrationobject and returns a calibration for three dimensions. The results of the calibration havebeen evaluated against synthetic and real data.
7
Arnošt, David. "Systémy průmyslového vidění a snímání 3D obrazu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229958.
Анотація:
Master´s thesis is describing basic concepts in machine vision. Used camera systems and possible imaging 2D and 3D are described. Practical part deals with constructin of scanning device with linear actuator, conveyor belt, camera and laser. For experimental use is construction of scanning device made for 2D and 3D image using several methods.
8
Navrátil, Pavel. "Konstrukční návrh kamerového jeřábu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229495.
Анотація:
This Master’s thesis deals with several variants construction design of camera crane. Two optimal variants are chosen with regard to practical usage. The thesis includes complete design of these variants with 3D models and strenght analyses. This analyses are processed by final element method. The first variant made based on technical documentation and it has worked for company Filmochod s.r.o..
9
Lundström, Josefine, and Juoni Ruotsalainen. "Aktivering av trafiksäkerhetskameror : En studie av kameraaktiveringens effekter på fordonshastigheter i Sverige." Thesis, Linköping University, Department of Computer and Information Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12110.
Анотація:
During 2006 an estimated number of 150 persons are supposed to have been killed in road accidents caused by speed limit violations. Through Automatic traffic security control (ATK) the Swedish road administration (Vägverket) is working towards lowering the number of speed related accidents. By placing the speed cameras on roads they've managed to lower the average speed at those places. The enlargement of the number of speed cameras is based upon knowledge about for example how high the risk is for speed related accidents on the roads. The speed cameras always measure the speed in which every vehicle passes, but aren't constantly activated to register speed violations. Our purpose with this essay is consequently to explore possible relations between the activation of the speed cameras and the speed itself on the roads.We studied the average speed and the number of speed violations during 12 weeks evenly distributed in 2007. To see if the results would differ, we used two different response variables in the analysis. Multiple linear regression was used to analyse the average speed, while Poisson regression was used in the analysis of the number of speed violations. An activated camera proved to cause a lowered average speed and fewer speed violations in three regions (Skåne, Mälardalen, Norr).To study the effect of maximized camera activation, an experiment in the region of Mälardalen was performed in the beginning of 2008. The result showed that maximized camera activation didn't decelerate the average speed, in stead the region's own activation policy seems to be more important for a lowered average speed. When the traffic flow rises the average speed decelerates while the number of speed violations also rises. During the study of commuter traffic we could see that the average speed is lower and there is fewer speed violations on commuter roads compared to normal traffic roads.
Under 2006 beräknas 150 personer ha omkommit i vägtrafikolyckor på grund av överskridna hastighetsgränser. Vägverket arbetar för att sänka dessa siffror bland annat genom att använda sig av Automatisk trafiksäkerhetskontroll (ATK). Genom att placera trafiksäkerhetskameror på sträckor har medelhastigheten på dessa sänkts. Trafiksäkerhetskamerorna mäter alltid hastigheten hos varje passerande fordon, men är inte konstant aktiverade för att registrera hastighetsöverträdelser. Nu vill man optimera kameraaktiveringen för att minska antalet ärenden utan att hanteringskapaciteten överskrids. Vårt syfte med uppsatsen är därför att undersöka möjliga samband mellan aktivering av trafiksäkerhetskameror och själva hastigheten på vägarna.Medelhastigheten och antalet överträdelser studerades under tolv veckor jämnt fördelade över år 2007. Analyserna gjordes med två olika responsvariabler för att se om resultaten skilde sig åt. Vi använde oss av multipel linjär regression för att analysera medelhastigheten, medan Poissonregression användes för antalet överträdelser. Det visade sig att en aktiv kamera gav upphov till sänkta medelhastigheter och färre hastighetsöverträdelser i tre regioner (Skåne, Mälardalen, Norr).För att studera effekten av maximal kameraaktivering utfördes ett experiment i region Mälardalen under början av 2008. Det visade sig att en maximal aktivering inte gav en sänkning av genomsnittshastigheterna, istället verkar regionens egen aktiverings-strategi ha större betydelse för sänkta genomsnittshastigheter.När fordonsflödet på alla sträckor ökar så minskar medelhastigheten medan antalet överträdelser ökar. För pendeltrafiksträckor är medelhastigheten lägre och det sker färre hastighetsöverträdelser än på normaltrafiksträckor.
10
Mužný, Lukáš. "Návrh snímacího portálu pro snímání 3D obrazu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230324.
Анотація:
This thesis deals with the possibilities of 3D vision. The theoretical part describes the principles of machine vision, constitutes the basic elements, description and the methods of measurement and 3D. The practical part is focused on the design of experimental workplace, which is consists of conveyor, experimental stand, industrial robot and PLC control. The system used to recognize and grasp objects undirected. Construction chapter focuses on the treatment needs of the conveyor for sensing applications and design of experimental stand with linear axis, which is equipped with camera and lasers. Furthermore solved by a communication network between the elements of work includes the design of their communications with the description of the control of its individual elements.
11
Duque, Alexis. "Bidirectional visible light communications for the internet of things." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI072/document.
Анотація:
Dans cette thèse, nous concevons et étudions un système de communication bidirectionnel par lumière visible (VLC) entre une diode électroluminescente (DEL) de couleur, intégrée à un objet connecté, et un smartphone. Le dispositif est ainsi capable d'envoyer et de recevoir des informations à travers sa DEL, tandis que le smartphone utilise sa caméra pour recevoir des données et son flash pour envoyer des informations. Nous mettons en œuvre et évaluons expérimentalement ce système VLC DEL-à-camera conçu spécifiquement pour les DELs de couleur à faible puissance. En nous appuyant sur les résultats d'une vaste étude expérimentale, nous modélisons, pour la première fois dans la littérature, le canal de communication DEL-à-caméra. Nous proposons alors un modèle de processus de Bernoulli modulé par une chaîne de Markov, qui nous permet d'étudier facilement l'efficacité de différentes stratégies de retransmission des messages. Nous exploitons ce modèle afin de concevoir un simulateur pour l'évaluation des performances des communications DEL-à-caméra. Afin d'obtenir un système de communication bidirectionnel, nous étudions ensuite les communications de type flash-vers-DEL entre un smartphone non-modifié et une petite DEL de couleur. Les performances, bien que limitées, sont suffisantes pour établir une voie retour qui permet de mettre en œuvre des mécanismes de fiabilisation. Nous proposons alors un mécanisme de codage linéaire pseudo-aléatoire, spécialement adapté aux conditions et contraintes du système DEL-à-caméra en ligne de visée directe. Notre évaluation expérimentale souligne que ce type d'approche augmente le rendement jusqu'à deux fois par rapport aux stratégies de retransmission classiques. Enfin, la plupart des objets que nous adressons ont des contraintes énergétiques importantes. Par conséquent, nous comparons la consommation d'énergie de notre système avec celle d'un module Bluetooth Low Energy avec une activité similaire. Nos résultats montrent que notre système réduit la consommation d'énergie dans le cadre d'un profil d'utilisation classiqueWith the exponential growth of the Internet of Things, people now expect every household appliance to be smart and connected. At the same time, smartphones have become ubiquitous in our daily life. Their continuous performance improvement and their compatibility with a broad range of radio protocols as WiFi, Bluetooth Low Energy (BLE) or NFC make them the most convenient way to interact with these smart objects. However, providing wireless connectivity with BLE or NFC means adding an extra chipset and an antenna, increasing the object size and price. Previous works already have demonstrated the possibility of receiving information through visible light using an unmodified smartphone thanks to its camera. Also, LED-to-LED communication for smart devices like toys has been shown previously. However, past efforts in LED to camera communication for IoT device communication have been limited. In this work, we design LightIoT, a bidirectional visible-light communication (VLC) system between a low-cost, low-power colored LED that is part of an IoT device and an off-the-shelf smartphone. The IoT device is thus able to send and receive information through its LED, while the smartphone uses its camera to receive data and its flashlight to send information. We implement and experimentally evaluate a LED-to-camera VLC system, designed specifically for small LEDs. The proposed solution exploits the rolling shutter effect of unmodified smartphone cameras and an original decoding algorithm, achieving a throughput of nearly 2 kb/s. Based on the insight gained from an extensive experimental study, we model, for the first time in the literature, the LED-to-camera communication channel. We propose a Markov-modulated Bernoulli process model, which allows us to easily study the performance of different message retransmission strategies. We further exploit this model to implement a simulator for LED-to-Camera communications performance evaluation. In order to achieve bi-directional communications, we evaluate flashlight-to-LED communications using non-rooted smartphones and small LEDs. With these constraints, our implementation achieves a throughput of 30 bits/second. While limited, this is enough for a feed-back channel coming to support the required redundancy mechanisms. Some of these redundancy mechanisms are based on random linear coding, never tested previously in VLC. Therefore, we design and implement, for the first time in the literature, a pseudo random linear coding scheme especially fitted for line-of-sight LED-to-camera conditions. Experimental evaluation highlights that this type of approach increases the goodput up to twice compared to classical retransmission strategies. Finally, we compare the energy consumption of LightIoT with the one of a BLE module with similar activity. Our results show that using the LED for communication purposes reduces the energy consumption under a normal usage behavior
12
Draréni, Jamil. "Exploitation de contraintes photométriques et géométriques en vision : application au suivi, au calibrage et à la reconstruction." Grenoble, 2010. http://www.theses.fr/2010GRENM061.
Анотація:
Cette thèse s'intéresse à trois problèmes fondamentaux de la vision par ordinateur qui sont le suivi vidéo, le calibrage et la reconstruction 3D. Les approches proposées sont strictement basées sur des contraintes photométriques et géométriques présentent dans des images 2D. Le suivi de mouvement se fait généralement dans un flux vidéo et consiste à suivre un objet d'intérêt identifié par l'usager. Nous reprenons une des méthodes les plus robustes à cet effet et l'améliorons de sorte à prendre en charge, en plus de ses translations, les rotations qu'effectue l'objet d'intérêt. Par la suite nous nous attelons au calibrage de caméras ; un autre problème fondamental en vision. Il s'agit là, d'estimer des paramètres intrinsèques qui décrivent la projection d'entités 3D dans une image plane. Plus précisément, nous proposons des algorithmes de calibrage plan pour les caméras linéaires (pushbroom) et les vidéo projecteurs lesquels étaient, jusque-là, calibrés de façon laborieuse. Le troisième volet de cette thèse sera consacré à la reconstruction 3D par ombres projetée. À moins de connaissance à priori sur le contenu de la scène, cette technique est intrinsèquement ambigüe. Nous proposons une méthode pour réduire cette ambiguïté en exploitant le fait que les spots de lumières sont souvent visibles dans la caméraThe topic of this thesis revolves around three fundamental problems in computer vision; namely, video tracking, camera calibration and shape recovery. The proposed methods are solely based on photometric and geometric constraints found in the images. Video tracking, usually performed on a video sequence, consists in tracking a region of interest, selected manually by an operator. We extend a successful tracking method by adding the ability to estimate the orientation of the tracked object. Furthermore, we consider another fundamental problem in computer vision: calibration. Here we tackle the problem of calibrating linear cameras (a. K. A: pushbroom)and video projectors. For the former one we propose a convenient plane-based calibration algorithm and for the latter, a calibration algorithm that does not require aphysical grid and a planar auto-calibration algorithm. Finally, we pointed our third research direction toward shape reconstruction using coplanar shadows. This technique is known to suffer from a bas-relief ambiguity if no extra information on the scene or light source is provided. We propose a simple method to reduce this ambiguity from four to a single parameter. We achieve this by taking into account the visibility of the light spots in the camera
13
Yu, Jingyi 1978. "General linear cameras : theory and applications." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34656.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaves 145-149).
I present a General Linear Camera (GLC) model that unifies many previous camera models into a single representation. The GLC model describes all perspective (pinhole), orthographic, and many multiperspective (including pushbroom and two-slit) cameras, as well as epipolar plane images. It also includes three new and previously unexplored multiperspective linear cameras. The GLC model is general and linear in the sense that, given any vector space where rays are represented as points, it describes all 2D affine subspaces (planes) formed by the affine combination of 3 rays. I also present theories of projection and collineation for GLCs and use these theories to explain various multiperspective distortions. Given an arbitrary multiperspective imaging system that captures smoothly varying set of rays, I show how to map the rays onto a 2D ray manifold embedded into a 4D linear vector space. The GLC model can then be use to analyze the tangent planes on this manifold. Geometric structures associated with the local GLC model of each tangent plane provide an intuitive physical interpretation of the imaging system, and they are closely related to the caustics of reflected rays. These geometric structures are characteristic of only 4 of the 8 GLC types. I also prove that the local GLC type at each tangent plane is invariant to the choice of parametrization, and, thus, an intrinsic property of the reflecting surface. Using GLCs to analyze the caustics of reflection extends the previous Jacobian-based approaches, which consider only a pinhole model at each infinitesimal region about each surface point. Finally, I demonstrate how to use the GLC model in computer vision, computer graphics, and optical design applications. In particular, I show how to use GLCs for modelling and rendering multiperspective images and characterizing real multiperspective imaging systems such as catadioptric mirrors.
by Jingyi Yu.
Ph.D.
14
Pearson, Christopher Mark. "Linear array cameras for mobile robot guidance." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318875.
15
Rushton, Nan Michelle. "An Exploration of Visual Sensations: The Use of Depth Perception to Create Pre-Architectural Forms." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/35699.
Анотація:
This exploration is one artist's view of visual reasoning through the study of depth perception. The experiment searched for pre-architectural forms through an investigation of geometric rectangular shapes and planar figures in anticipation of finding architectural volumes, that is, three-dimensional objects. I used three parameters to observe: the expected or planned, the anticipated, and the unforeseen.
The pre-architectural sketching style used the disciplines of painting, sculpture, graphic arts, color theory, optics, and photography to formulate an architectural language. First, as artist (painter), I selected the medium of light as the brushstroke, color as the pigment, and photographic film plane as the canvas to capture image abstractions. Second, I used one-point perspective as the viewer's line of sight. Finally, I employed a series of shape abstractions to form a succession of transparent sections that composed the subject matter.
This experiment sought to analyze visual perception by capturing the spatial depth of images, that is, a reproduction of something sculptural in likeness. The challenge was to reintegrate the abstracted Rectangular Shapes and Planar Figures. In order to achieve this physical abstraction, I created a modified camera obscura. This exploration produced clearly defined images-as-products that were interpreted as pre-architectural forms, which allowed me to translate color abstractions into architectural form studies, or models-as-products. Thus, the experiment created architectural volumes using light and color in order to draw points, lines, planes, and spatial depth.Master of Architecture
16
DUCROS, THIERRY. "Camera bi-lineaire pour la spectroscopie." Paris 7, 1990. http://www.theses.fr/1990PA077126.
Анотація:
L'utilisation intensive des capteurs d'images a l'etat solide (charge couple device ou photodiodes) ne cesse de croitre dans tous les domaines lies a l'imagerie. Les recherches de plus en plus pointues en astronomie ne font pas exception a la regle et necessitent l'emploi de la spectroscopie a haute resolution et de capteurs d'images possedant des caracteristiques tres specifiques, comme un faible bruit de lecture, de grandes dimensions, une forte sensibilite et la possibilite de longues poses sur de la lumiere. Ainsi, la camera bilineaire realisee a la demande des astronomes pour suivre les evolutions technologiques, est concue autour d'un capteur specialement developpe pour la spectroscopie a haute resolution. Elle exploite ces caracteristiques principales: 2 lignes de 2048 photodiodes (16 microns par 750 microns) chaque ligne etant lue par deux registres ccd
17
Lee, Young-ran. "Pose estimation of line cameras using linear features /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486457871786059.
18
Lindroth, [formerly Tyrberg] Simon. "Buoy and Generator Interaction with Ocean Waves : Studies of a Wave Energy Conversion System." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160085.
Анотація:
On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed. This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values. The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly. The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong. As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.
19
Loučka, Pavel. "Měření ovality extrudovaného vlákna pomocí tří kamer." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401570.
Анотація:
One of the important parameters observed during extruded fibre fabrication is its diameter. The diameter can be measured with a single scanning camera assuming that the fibre section has a circular shape. As proved in practice, another important parameter is ovality, that is the rate of fibre flattening. This paper assumes that the fibre section shape is elliptical. In such a case, at least three different views on examined fibre are needed. Mathematical part of this paper is concerned with analytical description of fibre ovality measurement using two different approaches based on the knowledge of linear algebra, projective geometry and conic sections theory. Main goal of this paper is thus to use both mathematical theory and image analysis methods for ovality and diameter determination. Precise calcluation of such quantities is, however, conditioned on precise camera system calibration, which is described in the paper as well. Additionally, the work contains a brief mention of technical realization of ovality measurement and its possible difficulties.
20
Chahla, Charbel. "Non-linear feature extraction for object re-identification in cameras networks." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0023.
Анотація:
La réplication du système visuel utilisé par le cerveau pour traiter l'information est un domaine de grand intérêt. Cette thèse se situe dans le cadre d'un système automatisé capable d'analyser les traits du visage lorsqu'une personne est proche des caméras et suivre son identité lorsque ces traits ne sont plus traçables. La première partie est consacrée aux procédures d'estimation de pose de visage pour les utiliser dans les scénarios de reconnaissance faciale. Nous avons proposé une nouvelle méthode basée sur une représentation sparse et on l'a appelé Sparse Label sensible Local Preserving Projections. Dans un environnement incontrôlé, la ré-identification de personne reposant sur des données biométriques n'est pas réalisable. Par contre, les caractéristiques basées sur l'apparence des personnes peuvent être exploitées plus efficacement. Dans ce contexte, nous proposons une nouvelle approche pour la ré-identification dans un réseau de caméras non chevauchantes. Pour fournir une mesure de similarité, chaque image est décrite par un vecteur de similarité avec une collection de prototypes. La robustesse de l'algorithme est améliorée en proposant la procédure Color Categorisation. Dans la dernière partie de cette thèse, nous proposons une architecture Siamese de deux réseaux neuronaux convolutionnels (CNN), chaque CNN étant réduit à seulement onze couches. Cette architecture permet à une machine d'être alimentée directement avec des données brutes pour faire la classificationReplicating the visual system that the brain uses to process the information is an area of substantial interest. This thesis is situated in the context of a fully automated system capable of analyzing facial features when the target is near the cameras, and tracking his identity when his facial features are no more traceable. The first part of this thesis is devoted to face pose estimation procedures to be used in face recognition scenarios. We proposed a new label-sensitive embedding based on a sparse representation called Sparse Label sensitive Locality Preserving Projections. In an uncontrolled environment observed by cameras from an unknown distance, person re-identification relying upon conventional biometrics such as face recognition is not feasible. Instead, visual features based on the appearance of people can be exploited more reliably. In this context, we propose a new embedding scheme for single-shot person re-identification under non overlapping target cameras. Each person is described as a vector of kernel similarities to a collection of prototype person images. The robustness of the algorithm is improved by proposing the Color Categorization procedure. In the last part of this thesis, we propose a Siamese architecture of two Convolutional Neural Networks (CNN), with each CNN reduced to only eleven layers. This architecture allows a machine to be fed directly with raw data and to automatically discover the representations needed for classification
21
Germanos, Ricardo Alberto Coppola. "Simulação numérica da evolução linear e não linear em uma camada de mistura compressível tridimensional." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-19012011-132153/.
Анотація:
As aplicações aeroespaciais estão frequentemente associadas a escoamentos compressíveis com altíssimos números de Reynolds. No entanto, existem no contexto aeroespacial importantes aplicações que envolvem escoamentos compressíveis a Reynolds relativamente baixos. Entre eles se destacam o escoamento em pás de turbina a gás e ao redor de dispositivos de alta sustentação como eslates e flapes em grandes ângulos de ataque. Pode-se destacar também o processo de combustão supersônica que está intimamente ligado e é fortemente beneficiado pelo presente estudo. Nas aplicações aerodinâmicas em baixos números de Reynolds frequentemente uma parcela significativa do escoamento se apresenta no regime de transição para turbulência, ou nos estágios iniciais do escoamento turbulento. O objetivo do presente projeto é a simulação numérica direta de escoamentos compressíveis transicionais com desenvolvimento de um código para simulação em três dimensões de escoamentos alto subsônicos. O escoamento a ser estudado no projeto é a evolução linear e não linear de trens de onda e pacotes de onda em uma camada de mistura compressível. A solução das equações de Navier-Stokes é obtida através do método das diferenças finitas. As derivadas espaciais são resolvidas através de um método compacto de sexta ordem, enquanto que as derivadas temporais são resolvidas através do método de Runge-Kutta de quarta ordem. Os métodos de aproximação foram modificados para trabalhar com malhas não uniformes visando refinar a malha em pontos em que o fenômeno ocorre e, consequentemente, reduzir o custo computacional. A investigação numérica inicia-se com a análise da taxa de amplificação dos trens de ondas fortemente modulados em regime linear. Os resultados obtidos foram comparados favoravelmente com a teoria linear. Os testes foram estendidos para a análise não linear, e consequentemente, foi possível reproduzir os fenômenos clássicos de instabilidade hidrodinâmica através da evolução dos trens de ondas oblíquos.Aerospace applications are frequently associated with compressible flows at relatively high Reynolds number. Nevertheless important applications involve compressible flows at relatively low Reynolds number in the aerospace context. Among them, the flow on gas turbine blades and high lift devices such as slats and flaps at high angle of attack are particulary important. Besides, progress in aeroespace research is dependent on developing more efficient propulsion systems. In aerodynamic applications at low Reynolds number, often a substancial portion of the flow is in the transition regime, or in the initial stages of a turbulent flow. The objective of the present study is the Direct Numerical Simulation of three-dimensional transition of compressible flows in a mixing layer. Inspired on the worked devoted to modulated waves, the current work investigates the linear and nonlinear temporal evolution of wavetrains in this phenomenon. The Navier-Stokes equations were solved with a sixth-order compact finite-difference schemes. The time integration was performed by a fourth-order Runge-Kutta scheme. Moreover, the methods to solve the spatial derivatives were modified to work with non-uniform grids. This technique was implemented with the objective to improve the resolution of the grid where the phenomenon occurs and to reduce the computational cost. The numerical investigation starts with an analysis of the growth rate of the wavetrains in linear regime to verify the numerical code. The results compared favourably with linear theory. Tests were also performed in the nonlinear regime to simulate the oblique wavetrains and it was possible to reproduce the classical hydrodynamic instability phenomena.
22
Salemi, Leonardo da Costa. "Análise de estabilidade linear de camada de mistura compressível binária." Instituto Nacional de Pesquisas Espaciais, 2006. http://urlib.net/sid.inpe.br/mtc-m17@80/2007/02.15.17.50.
Анотація:
Os sistemas aeroespaciais em sua maioria, se utilizam da liberação de energia química para funcionar. Dentre as aplicações mais comuns estão os motores de aeronaves (i.e. turbinas a gás) e motores foguete. Ambos precisam que o combustível seja misturado com um oxidante em uma camara de combustão para que reajam e formem gases, que serão expandidos posteriormente em uma tubeira. Entender como o fenomeno da mistura ocorre dentro da camara é muito importante no projeto e na previsão do desempenho de tais sistemas. Na combustão supersônica esse conhecimento é crucial já que os tempos de residência na câmara são muito reduzidos, requerendo que a mistura seja rápida e eficiente. A análise de estabilidade nos auxilia a prever se um padrão de escoamento é estável, neutro ou instável, e como este padrão evolui para a transição e mais tarde para a turbulência. Muitos autores compararam os resultados da análise de estabilidade linear com simulações numéricas diretas (SND) e com resultados experimentais, e concluíram que tais análises fornecem um panorama significativo e preciso da física do escoamento a um custo computacional desprezível. A análise de estabilidade já foi aplicada a muitos problemas da mecânica dos fluidos como camadas limite, jatos, esteiras e camadas de mistura, sendo estas o objeto deste trabalho. Camadas de mistura aparecem quando duas correntes de fluido confluem a velocidades diferentes (U1 6= U2). O principal mecanismo através do qual a mistura acontece é conhecido como instabilidade de Kelvin-Helmholtz. Quando os dois fluidos estão a baixas velocidades e não há reação química (i.e. liberação de calor), um padrão de instabilidade central, que é chamado de modo central, domina o processo de mistura. Quando lidamos com gases a altas velocidades, onde há o efeito de compressibilidade, outros modos de instabilidade conhecidos como modos externos começam a ter maior influência sobre o processo de mistura. Pode-se mostrar que a taxa de amplificação do modo central diminui com o aumento do número de Mach convectivo (PAPAMOSCHOU; ROSHKO, 1988). A análise de estabilidade começa com o cálculo viscoso compressível binário bidimensional dos perfis laminares das variáveis do escoamento utilizando-se a equação de estado de gás perfeito e as equações de conservação transformadas para obtenção de uma solução similar para o caso de uma camada de mistura. De posse das soluções laminares, as equações de conservação para um escoamento invíscido compressível binário tridimensional sujeito a perturbações infinitesimais são derivadas. Uma solução por modos normais, que consiste em inserir uma perturbação senoidal a um estado base, é proposta. Dessa forma, todas as variáveis do escoamento são representadas pela soma de um valor laminar e uma pequena perturbação. Essas soluções ondulatórias são substituídas nas equações de conservação adimensionalizadas obtendo-se um problema de autovalor representado por uma equação diferencial ordinária (EDO) para as perturbações. Essa EDO é então integrada numericamente, resultando nos autovalores e autofunções para o campo de escoamento.Many aerospace systems rely on the release of chemical energy to work properly. Among the most usual applications are aircraft engines (i.e. gas turbines) and rocket engines. Both kinds of engines need the fuel to be mixed with an oxidizer on a combustion chamber in order for them to react and form gases, which are later expanded on a nozzle. Understanding how the mixing phenomenon occurs inside the chamber is very important on the design and prediction of performance of such propulsion systems. On supersonic combustion this knowledge is crucial as the short residence times require ecient mixing. Through stability analysis, one can predict if some flow pattern is stable, neutral or unstable and how it evolves onto transition and later to turbulence. Many authors have compared linear stability analysis results with direct numerical simulations(DNS) and experimental results, and concluded that such analysis provide significant and accurate insight into the flow physics at negligible computational cost. Linear stability analysis has been applied on many problems in fluid mechanics like boundary layers, jets, plumes and mixing layers, which are the object of this work. Mixing layers occur when two streams of fluids coflow at dierent velocities (U1 6= U2). The main mechanism through which mixing occurs is known as the Kelvin-Helmholtz instability . When the fluids are at low speeds and there is no chemical reaction (i.e. heat release), a central pattern of instability, which is called central mode dominates the mixing process. When we deal with gases at high velocities , other modes of instability known as outer modes start to have a greater influence on the mixing process. It is shown that the growth rate of the center mode decreases with an increase of convective Mach number (PAPAMOSCHOU; ROSHKO, 1988). The stability analysis begins with the two-dimensional viscous compressible binary flow variables laminar profile calculation via the perfect gas state and conservation equations transformed to obtain a similar solution for the mixing layer case. With the laminar solutions, the conservation equations for a three-dimensional inviscid compressible binary laminar flow subjected to infinitesimal disturbances are derived. A normal mode form solution, which consists of introducing a sinusoidal disturbance on a base state, is proposed. In this manner, all the flow variables are represented by the sum of a laminar value and a small disturbance. These wave-like solutions are substituted on the nondimensional conservation equations leading to an eigenvalue problem represented by an ordinary dierential equation (ODE)for the disturbances. This ODE is integrated numerically, resulting in eigenvalues and eigenfunctions for the flow field.
23
Přibyl, Bronislav. "Odhad pózy kamery z přímek pomocí přímé lineární transformace." Doctoral thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2018. http://www.nusl.cz/ntk/nusl-412595.
Анотація:
Tato disertační práce se zabývá odhadem pózy kamery z korespondencí 3D a 2D přímek, tedy tzv. perspektivním problémem n přímek (angl. Perspective- n -Line, PnL). Pozornost je soustředěna na případy s velkým počtem čar, které mohou být efektivně řešeny metodami využívajícími lineární formulaci PnL. Dosud byly známy pouze metody pracující s korespondencemi 3D bodů a 2D přímek. Na základě tohoto pozorování byly navrženy dvě nové metody založené na algoritmu přímé lineární transformace (angl. Direct Linear Transformation, DLT): Metoda DLT-Plücker-Lines pracující s korespondencemi 3D a 2D přímek a metoda DLT-Combined-Lines pracující jak s korespondencemi 3D bodů a 2D přímek, tak s korespondencemi 3D přímek a 2D přímek. Ve druhém případě je redundantní 3D informace využita k redukci minimálního počtu požadovaných korespondencí přímek na 5 a ke zlepšení přesnosti metody. Navržené metody byly důkladně testovány za různých podmínek včetně simulovaných a reálných dat a porovnány s nejlepšími existujícími PnL metodami. Metoda DLT-Combined-Lines dosahuje výsledků lepších nebo srovnatelných s nejlepšími existujícími metodami a zároveň je značně rychlá. Tato disertační práce také zavádí jednotný rámec pro popis metod pro odhad pózy kamery založených na algoritmu DLT. Obě navržené metody jsou definovány v tomto rámci.
24
Maillot, Sacha. "Fluorescence picoseconde de complexes bio-moléculaires hors équilibre dans un écoulement microfluidique." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00957957.
Анотація:
Ce travail de thèse a démontré la possibilité de mesurer la relaxation d'un complexe biomoléculaire ainsi que son hétérogénéité structurale, en associant la microfluidique et la fluorescence résolue en temps (FRT). Je présente de quelle façon la FRT permet d'obtenir une information sur la structure d'une molécule et comment on la mesure, notamment grâce à une caméra à balayage de fente. J'introduis ensuite la microfluidique de gouttes, permettant de mélanger deux réactifs en quelques millisecondes et de suivre la relaxation du complexe au cours de la propagation des micro-réacteurs. Puis, la mesure d'une cinétique avec un couple de molécules modèle démontre la preuve de principe, faisant l'objet d'un article soumis. Enfin la mesure de FRT par comptage de photons uniques dans des gouttes uniques est décrite. Elle ouvre une perspective d'application pour le criblage à haut débit : un brevet a été déposé.
25
Hasegawa, Julio Kiyoshi. "Shape from shading com projeção perspectiva e calibração de camara." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260694.
Анотація:
Orientador: Clesio Luis TozziTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: : A maioria dos algoritmos encontrados na literatura, para a reconstrução de uma superfície 3D a partir de imagens de intensidade, usando a técnica de shape from shading (SFS), utiliza o sistema de projeção ortográfico. Este fato, no caso de imagens reais, causa deformações na superfície reconstruída. Neste trabalho desenvolve-se um procedimento simultâneo de reconstrução da superfície e calibração da câmara, que utiliza as técnicas de SFS e técnicas fotogramétricas, considerando a projeção perspectiva. São utilizados modelos matemáticos explícitos (equação de shading e colinearidade) e é aplicado um processo iterativo para recuperação da informação 3D da superfície e dos parâmetros de orientação da câmara. Devido ao uso de equações não lineares no modelo a linearização por série de Taylor foi utilizada. O Método dos Mínimos Quadrados (MMQ) foi aplicado, para obter um valor único a partir de observações superabundantes. Estes procedimentos se diferenciam em relação aos citados na literatura pelo fato de se calcular simultaneamente as coordenadas tridimensionais dos pontos da superfície e os parâmetros de orientação da câmara (calibração), não sendo necessárias restrições sobre a superfície. Imagens de profundidade e de intensidade foram geradas (simuladas), onde o processo de reconstrução foi aplicado na imagem de intensidade, cujo resultado foi verificado, comparando-a com a imagem de profundidade com a finalidade de analisar a exatidão do método
Abstract: The majority of algorithms making use of the Shape from Shading technique to reconstruct a 3 D surface from its image employs the orthographic projection system which, in the case of real images, always causes deformation on the reconstructed surface. To remove this constraint a simultaneous procedure (Hybrid Model) is proposed which uses the Shape from Shading technique (SFS) combined with the photogrammetric technique and the perspective projection to reconstruct the surface and determine the camera calibration parameters. The procedure is based on an explicit mathematical model and an iterative process is adopted to solve the resulting system of equations. The Least Square Method (LSM) is adopted and the Taylor's Series Linearization technique is applied due to the nonlinearity of the model. The proposed procedure differs from those found in the literature in that it carries out the simultaneous computation of the tridimensional coordinates of both the surface points and the camera calibration parameters while employing perspective projection. In addition to that, solving the resulting system of equations does not demand any restriction on the surface, as it appens in other related procedures. The intensity image and its respective depth image were generated and the proposed model is applied on the intensity image. The results obtained are compared with the depth image to analyse the accuracy of the proposed method
Doutorado
Doutor em Engenharia Elétrica
26
Selli, Nicola. "Static and seismic analysis of a historic masonry building in San Pio delle Camere." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Анотація:
In February 2021, in San Pio delle Camere, on the Navelli plateau south-east of L'Aquila, a masonry building collapsed suddenly, after repair work had just begun on the damage caused by the 2009 earthquake. The current study, after a detailed examination of all the design documentation and the comparison of the post-earthquake damage with the results of the analysis on the model, finding an excellent correspondence, went to research the possible causes of the structural collapse, which occurred in static conditions. The masonry texture was then analysed, consisting of unworked natural stones of medium-small size bound by poor quality mortar, parameterising the mechanical characteristics with in situ tests, the Masonry Quality Index and the values proposed in NTC 2018. Then, the analysis of the global model lead to the verification of the complexity of the aggregate induced greater pressures, and consequent deformations, precisely in the walls from which the collapse originated. With these assumptions, and from the evidence of the presence of a modest void in an internal facing, the study of the local mechanism was deepened, arriving at the presumption of the possible minimum dimensions of such a cavity and how this, even if minimal, could have been the cause if concomitant with the degradation of the bonding mortar induced by the absence of maintenance and the loss of even minimal resistance capacities.
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Hamid, Muhammed Hamed. "Hyperspectral Image Generation, Processing and Analysis." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5905.
28
Cyriac, Praveen. "Tone mapping based on natural image statistics and visual perception models." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/402574.
Анотація:
Les tècniques d'imatge d'alt rang dinàmic (HDR) potencialment permeten la captura i l'emmagatzematge de tota la informació de llum en una escena. No obstant això, els dispositius comuns de visualització són limitats en termes de les seves capacitats de contrast i brillantor, per tant, les imatges HDR han de ser mapejades tonalment abans de presentar-les en un dispositiu de visualització per assegurar que es reprodueix l'aspecte original de l'escena. En aquesta tesi, es prenen dos enfocaments del problema de mapeig tonal. En primer lloc, es desenvolupa un marc general per a la millora de qualsevol imatge mapejada tonalment mitjançant la reducció de la distància a la corresponent imatge HDR en termes d'una mètrica perceptiva no local. La distància es redueix al mínim per mitjà d'un algoritme de descens de gradient. En segon lloc, es desenvolupa un operador de mapeig tonal (TMO) en temps real que s'adapta bé a les estadístiques d'escenes naturals, i concorda amb els nous descobriments psicofísics i dades neurofísiques. Determinem les correctes adaptacions no lineals necessàries per als nostres resultats de mapeig tonal per tal d'obtenir l'aparença òptima en diferents condicions de visualització, a través d'experiments psicofísics i desenvolupar un mètode automàtic per poder predir dades experimentals. El nostre TMO produeix resultats d'aspecte natural, sense cap tipus d'artefactes espacials o temporals. Els tests de preferència dels usuaris mostren que el nostre mètode obté millors resultats en comparació amb les tècniques més recents. El TMO és ràpid i podria ser implementat en el hardware de la càmera. Pot ser utilitzat per al monitoratge de càmeres HDR en pantalles regulars, com a substitut de la correcció gamma, i com una manera de proporcionar al colorista amb contingut que té alhora un aspecte natural i una aparença nítida i clara.High Dynamic Range (HDR) imaging techniques potentially allow for the capture and storage of the full information of light in a scene. However, common display devices are limited in terms of their contrast and brightness capabilities, thus HDR images must be tone mapped before presentation on a display device to ensure that the original appearance of the scene is reproduced. In this thesis, we take two approaches to the tone mapping problem. First, we develop a general framework for improving any tone mapped image by reducing the distance with the corresponding HDR image in terms of a non-local perceptual metric. The distance is minimized by means of a gradient descent algorithm. Second, we develop a real-time Tone Mapping Operator (TMO) that is well suited to the statistics of natural scenes, and is in keeping with new psychophysical findings and neurophysical data. We determine the adequate non-linear adjustments needed for our tone mapping results to look best in different viewing conditions through a psychophysical experiment and develop an automatic method that can predict the experimental data. Our TMO produces results that look natural, without any spatio-temporal artifacts. User preference tests show that our method outperforms state of the art approaches. The TMO is fast and could be implemented on camera hardware. It can be used for on-set monitoring of HDR cameras on regular displays, as a substitute for gamma correction, and as a way of providing the colorist with content that is both natural looking and has a crisp and clear appearance.
29
Rodriguez, Miranda Juan Carlos 1984. "Estudio y análisis de sistemas lineales generados en problemas de contorno con frontera discontínua a partir de métodos espectrales/hp = Estudo e análise de sistemas lineares gerados nos problemas de contorno com fronteira descontinua a partir de métodos espectrais/hp." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306347.
Анотація:
Orientador: Petronio PulinoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Resumo: O Método dos Elementos Finitos representou nos últimos anos uma ferramenta fundamental no estudo de problemas de contorno. A evolução desde sua formulação fundamental a partir do Método de Galerkin clássico até sua versão com refinamento hp, se tornou na base dos métodos numéricos mais avançados como é o Método de Galerkin Descontinuo. O Método dos Elementos Finitos de Alta Ordem juntamente com os Métodos Espectrais usados na obtenção de soluções numéricas para problemas de contorno com fronteira descontinua, serão nosso objeto de estudo nesta Dissertação. Desde sua formulação matemática fundamental, por intermédio da escolha apropriada das funções hierárquicas que compõem os espaços de aproximação, assim como a montagem dos sistemas lineares locais e sua respectiva utilização no sistema linear global esparso, cuja solução é obtida pelo método iterativo de Gradiente Conjugado usando diversos Precondicionadores, será o caminho a seguir
Abstract: The Finite Element Method developed in the last decades has been the most important tool in the study of Boundary Value Problems. Your evolution from its fundamental formulation using the Galerkin Method to the hp-adaptive finite element methods (hp-FEM), provided the necessary foundation for more advanced Numerical Methods like the Galerkin Discontinuous Method. The Finite Element Method of Higher Order, together with the Spectral formulation as a numerical method to solve Boundary Problems with Discontinuous Boundary, is the objective of study to this dissertation. The fundamental mathematical formulation of the finite element methods, passing through of to choose of hierarchical basis functions, also the assembly of local linear systems and it posteriorly use to construct a Sparse Linear System, whose solution is obtained for an iterative Preconditioner Gradient Method
Mestrado
Matematica Aplicada
Mestre em Matemática Aplicada
30
Gisch, Debora Lidia. "Uma equação constituinte para a dispersão não-linear de poluentes na camada limite atmosférica turbulenta : fechamento fickiano modificado e a presença de fase." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/131016.
Анотація:
O fenômeno da dispersão de poluentes precisa ser compreendido e analisado pro- fundamente para que estudos de impactos ambientais possam ser realizados para projetar e prever situações. Então, obter um modelo analítico de dispersão de poluente realista torna- se interessante, pois permite avaliar com maior precisão o impacto ambiental da liberação de poluentes na atmosfera, além de abrir novos horizontes para a pesquisa. A Camada Limite Planetária (CLP) é o domínio de interesse da grande maioria dos modelos, já que nela os fenômenos turbulentos estão presentes. Uma característica destes fenômenos são os vórtices e turbilhões chamados de Estruturas Coerentes (ECs) e que são dominados por uma fase. O modelo analítico mais estudado é o que tem por base a equação advecção-difusão onde diversas simplificações como médias de Reynolds e o fechamento Fickiano são aplicados. Essas simplificações tornam o modelo determinístico e linear, mesmo o fenômeno sendo estocástico e não linear. Para resgatar algumas características do fenômeno turbulento neste trabalho sugeriu-se a inclusão de uma fase na equação advecção-difusão, através de um coeficiente difusivo complexo. Isso porque estruturas coerentes são características turbulentas dominadas pela fase. Comparou-se aqui os modelos com coeficiente difusivo real e complexo para as mesmas condições podendo assim observar qualitativamente a inclusão da fase no modelo que reproduz uma característica do escoamento turbulento, apresentando um comportamento mais realista. Apesar de não podemos garantir que esta é a maneira mais acertada de incluir a fase na equação advecção-difusão, com certeza ela nos trás um grande benefício que é a garantia de sempre ter soluções semi-positivas definidas, compatíveis com distribuições, para a representação da concentração.The phenomenon of dispersion of pollutants needs to be analyzed and deeply un- derstood so that environmental impact studies can be performed to design and predict situations. Then, to obtain an analytical model of realistic pollutant dispersion becomes interesting because it allows to accurately assess the environmental impact of the release of pollutants into the atmosphere and to open new horizons for research. The planetary bound- ary layer (PBL) is the domain of interest of the majority of models, since this is domain where turbulent phenomena are present. A feature of these phenomena are the vortexes and eddies that are Coherent Structures (CSs) and are dominated by a phase. The most studied analytical model is based on the advection-diffusion equation where several simpli cations such as Reynolds averages and Fickian closure are applied. These simpli cations render the model deterministic and linear, although the phenomenon is stochastic and nonlinear. To recover some characteristics of turbulent phenomena in this work a phase was included in the advection-diffusion equation by a complex diffusion coefficient. This is because coherents structures are turbulent characteristics and dominated by phase. We compared the models with real and complex diffusion coefficient for the same conditions, thus being able to observe qualitatively the inclusion of phase in the model that reproduces a characteristic of turbulent ow, presenting a more realistic behavior. Although we can not guarantee that this is the adequate way to include the phase in the advection-diffusion equation, it certainly brings us bene t that is the guarantee to always have at least semi-positive solutions, compatible with distributions that represent the concentration.
31
Msiska, Thomson. "An in vitro investigation of the effects of camellia sinensis and aspalathus linearis on benign (RPWE 1) and malignant (LNCaP) prostate cell lines." University of the Western Cape, 2015. http://hdl.handle.net/11394/5335.
Анотація:
Magister Scientiae (Medical Bioscience) - MSc(MBS)The prostate is prone to three pathological processes that include inflammation, benign prostate hyperplasia (BPH) and tumors. According to the center for Disease and Control 1999-2012 report, prostate cancer is the second leading cause of death in the United States. Scientific evidence suggests that up to 30% of men in the general population aged from 50 years and above, irrespective of geographic origin, have foci of prostate neoplastic growth. Unbalanced ROS production and a dysregulated antioxidant defence system have been implicated in prostate cancer development. The transformation of a normal cell into cancer takes a very long period. This observation provides the advantage of using nutraceuticals to prevent, arrest or reverse the cellular and molecular processes of carcinogenesis. Based on scientifically observed positive health roles of green tea (Cameli sinensis) and rooibos (Aspalathus linearis) on major diseases like atherosclerosis, hepatitis and certain types of cancer, this thesis evaluated the effects of these two teas on benign (RPWE 1) and malignant (LNCaP) prostate cells. This was done through the quantification of reactive oxygen species (ROS) using a fluorescence dye 5,6 CM-H2DCFDA, total prostate specific antigen (PSA) levels using a PSA ELISA kit, cell viability using the MTT assay, apoptosis using Tali annexin V stain and cell imaging studies using a Zeiss axiovert 200M inverted fluorescence microscope. Statistical analysis was done using graphpad prism. The findings of this study show that aqueous extracts of green and black tea, fermented and unfermented rooibos and their active compounds epigallocatechin gallate (EGCG) and aspalatin, respectively, are cytotoxic in malignant (LNCaP) prostate cells but exert protective effects in benign (RPWE 1) prostate cells. This thesis implicates the pro-oxidant and anti-oxidant properties of the plant extracts, respectively, for the above mentioned effects. In this regard, tea and rooibos promoted ROS production in malignant (LNCaP) prostate cells, which subsequently promoted cell death of the malignant cells through apoptosis and necrosis. Further to this, tea and rooibos used in this thesis, protected normal prostate cells from the adverse effects of ROS. In this regard, fluorescence microscope photographs showed RPWE 1 cells with low DCF fluorescence compared to the malignant prostate cells. Low magnification light microscope photographs showed RPWE 1 cells with flat polygonal shapes and increased adherence both at low and high concentrations of tea and rooibos. On the contrary, high concentrations of tea and rooibos on malignant (LNCaP) prostate cells induced stress, which made the cells attain irregular shapes and as the stress levels increased, cells became detached and appeared dead. Flow cytometry confirmed the presence of apoptotic and necrotic cell in malignant (LNCaP) prostate cells. In this thesis, EGCG and aspalathin were responsible for the high rates of apoptosis observed whereas green tea and unfermented rooibos induced the highest rate of necrosis. Further to this, tea and rooibos and the main active compounds EGCG and aspalathin, respectively, significantly promoted the reduction of total serum prostate specific antigen (PSA) in malignant prostate cells. In normal prostate cells, these plant extracts maintained the total serum PSA at its basal physiological level. In this thesis, to the best of our knowledge, we report for the first time the cell-specific effects of fermented rooibos, unfermented rooibos and their main active component aspalathin, on prostate cancer cells. We showed that rooibos and aspalathin exert pro-oxidant effects on malignant LNCaP cells and anti-oxidant effects on benign RPWE 1 cells. In conclusion, tea (C. sinensis) and rooibos (A. linearis) and their respective main active compounds, epigallocatechin gallate and aspalathin, are cytotoxic to malignant prostate cells whereas in normal prostate cells, they have protective effects against ROS induced stress. The pro-oxidant and anti-oxidant effects are responsible for the aforementioned effects respectively. The decrease in total serum PSA demonstrate the strong therapeutic effects that tea and rooibos have on malignant (LNCaP) prostate cells.
Malawi Government: Department of Human Resources Development and Management
32
Ragab, Ghanem Mohamed Mohamed. "Genetic Analyses of Reproductive Traits in Maternal Lines of Rabbits and in their Diallel Cross / Análisis Genético de Caracteres Reproductivos en Líneas Maternales de Conejo y en su Cruzamiento Dialélico." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/16187.
Анотація:
La producción ganadera es una de las actividades económicas más importantes de los países integrantes del Mercosur (Argentina, Brasil, Paraguay y Uruguay). Para Uruguay en particular, representa una de las fuentes de ingresos de divisas más importantes con exportaciones a múltiples mercados en todo el mundo. En los últimos años han crecido a nivel internacional las exigencias en materia de las condiciones de producción de los productos derivados de la ganadería, con especial énfasis en los temas medioambientales y de bienestar animal. En este sentido, el trabajo realizado en la presente tesis pretende realizar aportes en la caracterización de diferentes sistemas de producción desde el punto de vista productivo, de comportamiento y bienestar animal, así como de aspectos medioambientales. Para ello se realizaron trabajos en dos diferentes especies, bovinos y porcinos, y en diferentes sistemas de producción. Los dos primeros capítulos corresponden a tres sistemas de producción de bovinos con diferentes grados de intensificación: uno con animales en confinamiento permanente, un sistema exclusivamente pastoril y un sistema intermedio que combina confinamiento y pastoreo por seis horas. En ellos se caracterizan aspectos productivos, se establece los patrones de uso del tiempo, las tendencias diarias en cada comportamiento y la asociación de los mismos con las condiciones ambientales. Paralelamente se cuantifican las interacciones sociales en los diferentes sistemas, y varios indicadores fisiológicos y sus posibles implicaciones en el bienestar animal. En los restantes dos capítulos se analizan dos sistemas opuestos de producción de cerdos: uno tradicional con cerdos en confinamiento y un sistema alternativo con cerdos al aire libre con acceso a pasturas. Estos sistemas se caracterizan en los aspectos medioambientales, productivos y características de la carne resultante. Además se realiza una caracterización de los aspectos de comportamiento general y comportamiento sociRagab Ghanem, MM. (2012). Genetic Analyses of Reproductive Traits in Maternal Lines of Rabbits and in their Diallel Cross / Análisis Genético de Caracteres Reproductivos en Líneas Maternales de Conejo y en su Cruzamiento Dialélico [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16187
Palancia
33
Li, Qi. "Acoustic noise emitted from overhead line conductors." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/acoustic-noise-emitted-from-overhead-line-conductors(90a5c23c-a7fc-4230-bbab-16b8737b2af2).html.
Анотація:
The developments of new types of conductors and increase of voltage level have driven the need to carry out research on evaluating overhead line acoustic noise. The surface potential gradient of a conductor is a critical design parameter for planning overhead lines, as it determines the level of corona loss (CL), radio interference (RI), and audible noise (AN). The majority of existing models for surface gradient calculation are based on analytical methods which restrict their application in simulating complex surface geometries. This thesis proposes a novel method which utilizes both analytical and numerical procedures to predict the surface gradient. Stranding shape, proximity of tower, protrusions and bundle arrangements are considered within this model. One of UK National Grid's transmission line configurations has been selected as an example to compare the results for different methods. The different stranding shapes are a key variable in determining dry surface fields. The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift between these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is ‘pointed’.Research work on audible noise emitted from overhead line conductors is reviewed, and a unique experimental set up employing a semi-anechoic chamber and corona cage is described. Acoustically, this facility isolates undesirable background noise and provides a free-field test space inside the anechoic chamber. Electrically, the corona cage simulates a 3 m section of 400 kV overhead line conductors by achieving the equivalent surface gradient. UV imaging, acoustic measurements and a partial discharge detection system are employed as instrumentation. The acoustic and electrical performance is demonstrated through a series of experiments. Results are discussed, and the mechanisms for acoustic noise are considered. A strategy for evaluating the noise emission level for overhead line conductors is developed. Comments are made on predicting acoustic noise from overhead lines. The technical achievements of this thesis are summarized in three aspects. First of all, an FEA model is developed to calculate the surface electric field for overhead line conductors and this has been demonstrated as an efficient tool for power utilities in computing surface electric field especially for dry condition. The second achievement is the droplet vibration study which describes the droplets' behaviour under rain conditions, such as the phase shift between the voltage and the vibration magnitude, the ejection phenomena and the electric field enhancement due to the shape change of droplets. The third contribution is the development of a standardized procedure in assessing noise emission level and the characteristics of noise emissions for various types of existing conductors in National Grid.
34
Vestin, Albin, and Gustav Strandberg. "Evaluation of Target Tracking Using Multiple Sensors and Non-Causal Algorithms." Thesis, Linköpings universitet, Reglerteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-160020.
Анотація:
Today, the main research field for the automotive industry is to find solutions for active safety. In order to perceive the surrounding environment, tracking nearby traffic objects plays an important role. Validation of the tracking performance is often done in staged traffic scenarios, where additional sensors, mounted on the vehicles, are used to obtain their true positions and velocities. The difficulty of evaluating the tracking performance complicates its development. An alternative approach studied in this thesis, is to record sequences and use non-causal algorithms, such as smoothing, instead of filtering to estimate the true target states. With this method, validation data for online, causal, target tracking algorithms can be obtained for all traffic scenarios without the need of extra sensors. We investigate how non-causal algorithms affects the target tracking performance using multiple sensors and dynamic models of different complexity. This is done to evaluate real-time methods against estimates obtained from non-causal filtering. Two different measurement units, a monocular camera and a LIDAR sensor, and two dynamic models are evaluated and compared using both causal and non-causal methods. The system is tested in two single object scenarios where ground truth is available and in three multi object scenarios without ground truth. Results from the two single object scenarios shows that tracking using only a monocular camera performs poorly since it is unable to measure the distance to objects. Here, a complementary LIDAR sensor improves the tracking performance significantly. The dynamic models are shown to have a small impact on the tracking performance, while the non-causal application gives a distinct improvement when tracking objects at large distances. Since the sequence can be reversed, the non-causal estimates are propagated from more certain states when the target is closer to the ego vehicle. For multiple object tracking, we find that correct associations between measurements and tracks are crucial for improving the tracking performance with non-causal algorithms.
35
Pecorella, Daniele. "Methodology for the design and optimization of a morphing wing droop-nose structure for greener aircraft." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Анотація:
Droop-Nose Leading Edge (DNLE) morphing wings are one of the most promising devices in order to achieve aerodynamic drag and noise reduction during take-off and landing phases. An accurate design of these structures could lead to the decrease of aircraft fuel consumption in the perspective of reaching a greener aviation, following the objectives indicated by Flightpath 2050 issued by the E.U. However, due to the challenges related to the realization of this technology and TRL reached, DNLE are more likely implemented in Unmanned Aerial Systems (UAS) for testing and evaluation purposes. In the present study, an optimization methodology for the DNLE composite laminate skin and morphing mechanism structure is proposed and applied to a study case represented by the UAS-S45 aircraft. The work starts from the morphing leading edge structure developed by the LARCASE laboratory at ETS Montreal. The results showed that by means of the optimization strategy adopted, the force required on the actuator mechanism is 88% lower than the original design. A significant improvement on the profile smoothness along its section and in the spanwise direction in morphing conditions has been obtained too. However, further investigations are still needed in order to achieve a more appropriate morphing shape. Despite this, it appears from the results obtained that the proposed methodology can be useful to tackle the DNLE design problem in an effective and efficient way. What developed in this work has been conceived to support the investigation of DNLE in the small leading edge profiles typical of the UAS. In this way, an easier procedure for the set up of the design flow, and a decrease in the computational effort for the optimization process can be obtained. An experimental validation of the results obtained is currently being performed at ETS, and future development regards the assessment of the errors of the numeric procedure herein presented respect to real data.
36
WENG, MIN-DONG, and 翁敏東. "A linear approach to nonlinear camera calibration." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/50335757780985419501.
37
Chia-Hsin, Lien, and 連家欣. "Non-linear Color Reproduction Method in Digital Camera." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/02065530794523793652.
Анотація:
碩士國立臺灣大學
資訊工程學研究所
99
In this thesis, we illustrate a nonlinear regression method “Gauss-Newton” and an adaptive weighted matrix for color reproduction in digital camera. We aim to reduce the chrominance error in nonlinear domain and thus require computing on the tendency to approach minimum. The 24 color patches in GretagMacbeth ColorChecker are the reference for color fitting. Having precise color representation is crucial in many applications such as medical imaging, press, textile industry and so on. With proper calibration, the color can be subjectively or objectively corrected depends on the target application.
38
Jhou, Bo-Shen, and 周柏伸. "A Study of RGB-Depth Camera Calibration with Direct Linear Transformation." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/13012851137255349773.
Анотація:
碩士國立臺灣科技大學
資訊工程系
103
In recent years, cameras equipped with depth sensors is a trend. The depth information makes the development of interactive applications further excellent. To make this kind of RGB-Depth cameras consisting of RGB sensors and depth sensors more concise, calibration is a must. This paper presents a novel calibration method based on the Direct Linear Transformation (DLT). The advantage of the DLT method is to get rid of the complicated calibrating procedures in the traditional calibration methods. The DLT method employs the linear relationship between objects and images to get camera parameters and measure the relationship between the RGB camera and the depth camera. The relationship contains the rotation matrix and the translation vector. Finally, we employ the acquired parameters to conduct the alignment of the RGB frames and the depth frames. The results of our experiments show that the proposed calibration method is practical. In the future, we will further consider the lens distortion and try to make the calibration more precise.
39
Lai, Lung-Kuan, and 賴隆寬. "Creative Design and Analysis of Linear Actuator for Auto-focusing in Phone Camera." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/07114243163878297149.
Анотація:
博士國立交通大學
機械工程學系
100
Recently, photographers demand higher pixel resolution of image sensors and smaller size in digital or mobile phone cameras, whose auto–focusing (AF) and precision positioning control become topics worthy to research. These techniques can effectively prevent taking camera images from blurring through compensating camera shakes when photographers are taking pictures. Voice coil motors (VCMs) consist of permanent magnets, yokes, and gaps, which are components of the magnetic circuit. For high efficiency, optimal magnetic design is very important. In this study, based on characteristics of VCMs, the graph theory is adopted to enumerate all magnetic circuit designs. Furthermore, rules representing design criteria and a flow value method are used to compare enumerated designs for achieving magnetic circuits. In the magnetic field analysis, this study uses the finite element method to analyze voice coil motors in achieving better optimal actuator force. This study considers the effect of different shapes in magnetic components and chooses the best design. This study presents a complete design process for applications of VCM. The above process is used to design two novel linear electromagnetic actuators (LEAs). In the first LEA, when coils are powered, induced magnetic field generates N and S poles around iron cores. Thus, unlike voice coil motors that employ Lorentz force, the motion of the moving part in this study is arisen from a magnetic field property － same poles repel each other while opposite poles attract each other. The second proposed VCM actuator does not contain springs that are usually used in conventional VCM actuators. Moreover, the maximum current required to displace the moving part of the novel VCM is 40 mA. This represents a current reduced by 50% compared to the conventional actuator, and leads to a significant improvement in the power efficiency of the device. Using a coupled three-dimensional finite element method, we calculate electromagnetic and mechanical characteristics of two actuators current variation of coils, displacement of the moving part, velocity, and motive force of actuators. The results show that the proposed two actuators have merits of rapid response and low power consumption.
40
Pal, Madhumita. "Accurate and Efficient Algorithms for Star Sensor Based Micro-Satellite Attitude and Attitude Rate Estimation." Thesis, 2013. http://etd.iisc.ernet.in/2005/3428.
Анотація:
This dissertation addresses novel techniques in determining gyroless micro-satellite attitude and attitude rate. The main objective of this thesis is to explore the possibility of using commercially available low cost micro-light star sensor as a stand-alone sensor for micro-satellite attitude as well as attitude rate determination. The objective is achieved by developing accurate and computationally efficient algorithms for the realization of onboard operation of a low fidelity star sensor. All the algorithms developed here are tested with the measurement noise presented in the catalog of the sensor array STAR-1000.
A novel accurate second order sliding mode observer (SOSMO) is designed for discrete time uncertain linear multi-output system. Our design procedure is effective for both matched and unmatched bounded uncertain ties and/or disturbances. The bound on uncertainties and/or disturbances is assumed to be unknown. This problem is addressed in this work using the second order multiple sliding modes approach. Second order sliding manifold and corresponding sliding condition for discrete time system is defined similar on the lines of continuous counterpart. Our design is not restricted to a particular class of uncertain (matched) discrete time system. Moreover, it can handle multiple outputs unlike single out-put systems. The observer design is achieved by driving the state observation error and its first order finite difference to the vicinity of the equilibrium point (0,0) in a finite steps and maintaining them in the neighborhood thereafter. The estimation synthesis is based on Quasi Sliding Mode (QSM) design.
The problem of designing sliding mode observer for a linear system subjected to unknown inputs requires observer matching condition. This condition is needed to ensure that the state estimation error is a asymptotically stable and is independent of the unknown input during the sliding motion. In the absence of a matching condition, asymptotic stability of the reduced order error dynamics on the sliding surface is not guaranteed. However, unknown bounded inputs guarantee bounded error on state estimation. The QSM design guarantees an ultimate error bound by incorporating Boundary Layer (BL) in its design procedure.
The observer achieves one order of magnitude improvement in estimation accuracy than the conventional sliding mode observer (SMO) design for an unknown input. The observer estimation errors, satisfying the given stability conditions, converge to an ultimate finite bound (with in the specified BL) of O(T2), where T Is the sampling period. A relation between sliding mode gain and boundary layer is established for the existence of second order discrete sliding motion. The robustness of the proposed observer with respect to measurement noise is also analyzed. The design algorithm is very simple to apply and is implemented for two examples with different classes of disturbances (matched and unmatched) to show the effectiveness of the design. Simulation results show the robustness with respect to the measurement noise for SOSMO.
Second order sliding mode observer gain can be calculated off-line and the same gain can work for large band of disturbance as long as the disturbance acting on the continuous time system is bounded and smooth. The SOSMO is simpler to implement on board compared to the other traditional nonlinear filters like Pseudo-Linear-Kalman-filter(PLKF); Extended Kalman Filter(EKF). Moreover, SMO possesses an automatic adaptation property same as optimal state estimator(like Kalman filter) with respect to the intensity of the measurement noise. The SMO rejects the noisy measurements automatically, in response to the increased noise intensity. The dynamic performance of the observer on the sliding surface can be altered and no knowledge of noise statistics is required. It is shown that the SOSMO performs more accurately than the PLKF in application to micro-satellite angular rate estimation since PLKF is not an optimal filter.
A new method for estimation of satellite angular rates through derivative approach is proposed. The method is based on optic flow of star image patterns formed on a star sensor. The satellite angular rates are derived directly from the 2D-coordinates of star images. Our algorithm is computationally efficient and requires less memory allocation compared to the existing vector derivative approaches, where there is also no need for star identification. The angular rates are computed using least square solution method, based on the measurement equation obtained by optic flow of star images. These estimates are then fed into discrete time second order sliding mode observer (SOSMO). The performance of angular rate estimation by SOSMO is compared with the discrete time First order SMO and PLKF. The SOSMO gives the best estimates as compared to the other two schemes in estimating micro-satellite angular rates in all three axes. The improvement in accuracy is one order of magnitude (around1.7984 x 10−5 rad/ sec,8.9987 x 10−6 rad/ sec and1.4222 x 10−5 rad/ sec in three body axes respectively) in terms of standard deviation in steady state estimation error.
A new method and algorithm is presented to determine star camera parameters along with satellite attitude with high precision even if these parameters change during long on-orbit operation. Star camera parameters and attitude need to be determined independent of each other as they both can change. An efficient, closed form solution method is developed to estimate star camera parameters (like focal length, principal point offset), lens distortions (like radial distortion) and attitude. The method is based on a two step procedure. In the first step, all parameters (except lens distortion) are estimated using a distortion free camera model. In the second step, lens distortion coefficient is estimated by linear least squares (LS) method. Here the derived camera parameters in first step are used in the camera model that incorporates distortion. However, this method requires identification of observed stars with the catalogue stars. But, on-orbit star identification is difficult as it utilizes the values of camera calibrating parameters that can change in orbit(detector and optical element alignment get change in orbit due to solar pressure or sudden temperature change) from the ground calibrated value. This difficulty is overcome by employing a camera self-calibration technique which only requires four observed stars in three consecutive image frames. Star camera parameters along with lens (radial and decentering) distortion coefficients are determined by camera self calibration technique. Finally Kalman filter is used to refine the estimated data obtained from the LS based method to improve the level of accuracy.
We consider the true values of camera parameters as (u0,v0) = (512.75,511.25) pixel, f = 50.5mm; The ground calibrated values of those parameters are (u0,v0) =( 512,512) pixel, f = 50mm; Worst case radial distortion coefficient affecting the star camera lens is considered to be k1 =5 x 10−3 .Our proposed method of attitude determination achieves accuracy of the order of magnitude around 6.2288 x 10−5 rad,3.3712 x 10−5 radand5.8205 x
10−5 rad in attitude angles φ,θ and ψ. Attitude estimation by existing methods in the literature diverges from the true value since they utilize the ground calibrated values of camera parameters instead of true values.
To summarize, we developed a formal theory of discrete time Second Order Sliding Mode Observer for uncertain multi-output system. Our methods achieve the desired accuracy while estimating satellite attitude and attitude rate using low fidelity star sensor data. Our methods require lower on-board processing requirement and less memory allocation; thus are suitable for micro-satellite applications. Thus, the objective of using low fidelity star sensor as stand-alone sensor in micro-satellite application is achieved.