Dissertations / Theses on the topic 'Estimation de la distance'
To see the other types of publications on this topic, follow the link: Estimation de la distance.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Estimation de la distance.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lowe, Karsten. "Distance estimation between transceivers over short distances." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202417257/.
Full text
2
Tekaya, Souhaiel Ben. "Distance estimation using handheld devices." Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/34753.
Full textAbstract:
Approved for public release; distribution is unlimitedThe different capabilities mobile devices can offer in the field of distance estimation for military applications are explored in this thesis. Of particular interest is the potential for using computer vision techniques to estimate distance in an operational military environment. The methods used for this investigation include a review of past literature on computer vision techniques in this domain, as well as an exploration of the different capabilities mobile devices offer in terms of sensors and networking. We present two potential solutions. The first is a simulation of a distance estimation algorithm that gives the distance to the target using a pair of hyper stereo images. The second solution is a web-based mobile application prototype developed in HTML5. This prototype is intended for the use of untrained forward observers. It goes through the basic steps of a call for fire mission as required by a forward observer, with a focus on distance estimation.
3
Andrieu, Guillaume. "Estimation par intervalle d'une distance évolutive." Montpellier 2, 1997. http://www.theses.fr/1997MON20233.
Full textAbstract:
L'objet de cette these est l'etude de la variabilite d'une estimation de la distance evolutive entre deux sequences moleculaires. Apres un bref apercu de l'historique des theories de l'evolution, nous presentons les differentes methodes de reconstruction phylogenetiques. Nous detaillons ensuite l'expression et l'estimation d'une distance evolutive entre deux sequences dans le cadre d'un modele stochastique de l'evolution. Deux methodes sont communement utilisees pour mesurer l'incertitude d'une estimation de la distance evolutive : l'estimation de la variance et le bootstrap. Nous proposons l'application de la methode statistique d'estimation par intervalle. Nous presentons les methodes et les algorithmes de construction d'intervalles de confiance que nous avons developpe dans le cadre de deux modeles : celui de jukes et cantor (1969) et celui de kimura (1980). Les resultats obtenus par simulation ou avec des donnees reelles et artificielles montrent la validite de notre demarche et nous permettent d'observer le comportement des autres methodes dans diverses conditions quant a la taille des sequences et la proportion de difference entre les sequences.
4
Lammi, J. (Jouni), P. (Petteri) Moilanen, and A. (Aleksi) Sierilä. "Size and distance estimation in virtual reality." Bachelor's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201906132541.
Full textAbstract:
Abstract. Interest in virtual reality (VR) has been on the rise in the recent few years. However, it is difficult to create virtual environments which provide realistic perception of scale for their users. We wanted to study how humans perceive scale in VR and ways to improve VR scale perception.
We did a pilot test to see how design choices affect distance and height estimation in VR. For pilot tests we had nine test participants.
Based on the experience gathered from the pilot test, we designed the main test. For the main test we had 44 participants. The main test showed similar results for distance estimating as earlier studies. Humans underestimated distances and heights in VR. Having a familiar size object cue, a VR model of a milk carton, next to the object improved height estimations.Koon ja etäisyyden arviointi virtuaalitodellisuudessa. Tiivistelmä. Kiinnostus virtuaalitodellisuuteen (VT) on ollut kasvavaa muutaman viime vuoden aikana. On kuitenkin vaikeaa tehdä virtuaalinen ympäristö, joka luo käyttäjilleen luonnollisen aistimuksen mittakaavasta. Halusimme tutkia, miten ihmiset hahmottavat skaalaa VR:ssä ja kuinka sitä voi parantaa.
Teimme pilottitestejä, jotta näkisimme kuinka erilaiset suunnittelupäätökset vaikuttavat etäisyyden ja korkeuden arviointiin virtuaalitodellisuudessa. Pilottitesteissä oli yhdeksän osallistujaa.
Pilottitestien pohjalta teimme laajemman testin, jossa hyödynsimme pilottitesteistä saatuja kokemuksia. Laajemmassa testissä oli 44 osallistujaa. Tämä testi tuotti samankaltaisia tuloksia etäisyyden arvioinnissa kuin aikaisemmat tutkimukset. Ihmiset aliarvioivat etäisyyksiä ja korkeuksia virtuaalitodellisuudessa. Kun esineen vieressä oli tunnetun kokoinen esine, maitopurkin virtuaalimalli, korkeuden arviointi parani.
5
Warwick, Jane. "Selecting tuning parameters in minimum distance estimators." n.p, 2001. http://ethos.bl.uk/.
Full text
6
Eriksson, Nils. "Estimation of Distance to empty for heavy vehicles." Thesis, Linköping University, Vehicular Systems, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-56905.
Full textAbstract:
The distance to empty (DTE) for a heavy vehicle is valuable information both forthe driver and the hauler company. The DTE is estimated as the ratio between the current fuel level and a representative mean fuel consumption. This means the fuel consumption is a prediction of the most likely future mean fuel consumption based on earlier data. It is calculated by applying a forgetting filter on the signal of the momentary fuel consumption in the engine. The filter parameter control how many values that contributes to the output. This is a balance between desired robustness and adaptability of the estimate.
Initially, a pre-stored value is used as an estimate of the mean fuel consumption. By this, the driver gets a first hint of the DTE value and the estimation of the DTE gets a good starting point. Stored values will adapt continuously with an online algorithm using vehicle data from previous runs. An alternative to showing the DTE is to present the time to empty when the vehicle speed is close to zero.
The accuracy of the proposed algorithm depends on the quality of the input signals. With the current input signals, it is possible to get a DTE estimate that, over a longer time period, decrease in the same pace as the distance meter increase. This is considered as a good validation measurement. If altitude data for the current route would be used, a more accurate DTE estimate could be obtained. The sample distance for this altitude data could however be set to a 1000 meter without affecting the estimate significantly.
Sträckan till tom tank för ett tungt fordon är värdefull information, både för den enskilde föraren och åkeriet. Förkortad som DTE (Distance to empty) kan detta värde estimeras som kvoten av den nuvarande bränslenivån i tanken och en genomsnittlig bränsleförbrukning.
Denna genomsnittliga bränsleförbrukning är en prediktion av den troligaste framtida snittförbrukningen baserad på tidigare värden. Detta görs genom att ett glömskefilter appliceras på signalen för den aktuella bränsleförbrukningen i motorn. Filterparametern avgör hur snabbt gamla värden på insignalen ska klinga av och när den anpassas så måste önskad stabilitet vägas mot önskad känslighet hos skattningen.
Initialt så används förlagrade värden som skattning för den genomsnittliga bränsleförbrukningen. Detta gör att föraren får en första aning om hur långt fordonet kan köras samt ger DTE estimeringen en bra utgångspunkt. Dessa lagrade värden uppdateras under drift med information från det aktuella fordonet. För att hanterade problem som kan uppstå vid låga hastigheter eller tomgång kan istället tiden till tom tank visas.
Resultatet av DTE skattningen beror på kvalitén på insignalerna. Med de nuvarande insignalerna fås en DTE skattning som över en längre tidsperiod minskar sitt värde i samma takt som avståndsmätaren ökar sitt, vilket är ett önskvärt uppförande.
Om höjddata för en den aktuella rutten skulle användas skulle DTE estimeringen kunna göras mer noggrant. Det skulle dock räcka med att använda höjdinformation var 1000:e meter och ändå få en tillräckligt noggrann skattning.
7
Gelman, Geoffrey M. (Geoffrey Michael) 1977. "Distance estimation through wavefront curvature in cellular systems." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80537.
Full textAbstract:
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaves 78-79).
by Geoffrey M. Gelman.
S.B.and M.Eng.
8
Vichare, Nitin Shrikrishna. "Robust Mahalanobis distance in power systems state estimation." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40024.
Full text
9
Huang, Kyman. "DISTANCE ESTIMATION USING OFDM SIGNALS FOR ULTRASONIC POSITIONING." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2147.
Full textAbstract:
This paper describes a method of estimating distance via Time-of-Flight (TOF) measurement using ultrasonic Orthogonal Frequency Division Multiplexing (OFDM) signals. Using OFDM signals allows the signals and their sub-carriers to remain orthogonal to each other while continuously transmitting. This estimation method is based on the change of phase of a traveling wave as it propagates through a medium (air for ultrasonic signals). By using signals containing multiple tones, the phase change between each frequency component is slightly different. This phase difference is dependent on the distance traveled and can thus be used to estimate distance. This paper studies the impact of tone (OFDM sub-carriers) separation on accuracy, maximum distance, and computation for two-tone and three-tone systems. The effects of the transducer channel bandwidth and channel noise are accounted for to build an accurate model for a single-transmitter single-receiver system. This study found that each additional tone provides one extra independent distance measurement which improves accuracy in the presence of noise. The inclusion of an additional tone while maintaining the same overall signal strength shows improved performance with a reduction in standard deviation of estimated distance from 5.64 mm to 3.42 mm in simulation. A four-tone system is also examined to show that this effect holds for additional tones.
10
Campos, Jennifer L. Sun Hong-Jin. "Multisensory integration in the estimation of distance travelled." *McMaster only, 2007.
Find full text
11
Lenox, Joseph Daniel. "Distance Estimation to a Transmitter with Stateful Preprocessing." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/679.
Full textAbstract:
A method for estimating distance, in one dimension, to a transmitter for a receiver in motion relative to that transmitter is given with simulation data. The method relies on a stateful preprocessor filter and does not require envelopment of the transmitter.
12
Richardson, Adam R. "The influence of prior interaction with an immersive virtual environment on user's distance estimates." Oxford, Ohio : Miami University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1161020618.
Full text
13
Chu, Xiaoyuan. "Improving Estimation Accuracy using Better Similarity Distance in Analogy-based Software Cost Estimation." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-246116.
Full textAbstract:
Software cost estimation nowadays plays a more and more important role in practical projects since modern software projects become more and more complex as well as diverse. To help estimate software development cost accurately, this research does a systematic analysis of the similarity distances in analogy-based software cost estimation and based on this, a new non-orthogonal space distance (NoSD) is proposed as a measure of the similarities between real software projects. Different from currently adopted measures like the Euclidean distance and so on, this non-orthogonal space distance not only considers the different features to have different importance for cost estimation, but also assumes project features to have a non-orthogonal dependent relationship which is considered independent to each other in Euclidean distance. Based on such assumptions, NoSD method describes the non-orthogonal angles between feature axes using feature redundancy and it represents the feature weights using feature relevance, where both redundancy and relevance are defined in terms of mutual information. It can better reveal the real dependency relationships between real life software projects based on this non-orthogonal space distance. Also experiments show that it brings a greatest of 13.1% decrease of MMRE and a 12.5% increase of PRED(0.25) on ISBSG R8 dataset, and 7.5% and 20.5% respectively on the Desharnais dataset. Furthermore, to make it better fit the complex data distribution of real life software projects data, this research leverages the particle swarm optimization algorithm for an optimization of the proposed non-orthogonal space distance and proposes a PSO optimized non-orthogonal space distance (PsoNoSD). It brings further improvement in the estimation accuracy. As shown in experiments, compared with the normally used Euclidean distance, PsoNoSD improves the estimation accuracy by 38.73% and 11.59% in terms of MMRE and PRED(0.25) on ISBSG R8 dataset. On the Desharnais dataset, the improvements are 23.38% and 24.94% respectively. In summary, the new methods proposed in this research, which are based on theoretical study as well as systematic experiments, have solved some problems of currently used techniques and they show a great ability of notably improving the software cost estimation accuracy.
14
Xiang, Sijia. "Minimum Hellinger distance estimation in a semiparametric mixture model." Kansas State University, 2012. http://hdl.handle.net/2097/13762.
Full textAbstract:
Master of ScienceDepartment of Statistics
Weixin Yao
In this report, we introduce the minimum Hellinger distance (MHD) estimation method and review its history. We examine the use of Hellinger distance to obtain a new efficient and robust estimator for a class of semiparametric mixture models where one component has known distribution while the other component and the mixing proportion are unknown. Such semiparametric mixture models have been used in biology and the sequential clustering algorithm. Our new estimate is based on the MHD, which has been shown to have good efficiency and robustness properties. We use simulation studies to illustrate the finite sample performance of the proposed estimate and compare it to some other existing approaches. Our empirical studies demonstrate that the proposed minimum Hellinger distance estimator (MHDE) works at least as well as some existing estimators for most of the examples considered and outperforms the existing estimators when the data are under contamination. A real data set application is also provided to illustrate the effectiveness of our proposed methodology.
15
Li, Zetong. "A Vision-Based Distance Estimation System for Flying Copters." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41009.
Full textAbstract:
Currently, as one of the most popular technologies being discussed and experimented, the application of flying copters in different industries is facing an obvious barrier; which is how to avoid obstacles while flying. One of the industries among all is small-sized package delivery business, which is also the master topic of a series of experiments. The most popular designs that have used for the Flying Copter Obstacle Avoidance System such as lidar scanners and infrared rangefinders are significantly accurate. However, with the heavyweight, expensive price and higher power consumption, these systems cannot be put into mass production. To reduce the cost and power consumption of the Obstacle Avoidance System, an innovative vision-based low-cost Obstacle Distance Estimation System for flying copters is demonstrated in this thesis. The Fisheye Lens Camera is used to provide a broader detection range and accurate results.
Compared to other standard vision-based systems, the Fish Lens Camera Distance Estimation System can provide (around 360 degrees) extensive view for obstacle detection. Through the parallax pictures captured by the camera and the trigonometric rules, the system can estimate the distance to the target obstacle with reasonable results.
16
Warwick, Jane. "Selecting tuning parameters in minimum distance estimators." Thesis, Open University, 2002. http://oro.open.ac.uk/19918/.
Full textAbstract:
Many minimum distance estimators have the potential to provide parameter estimates which are both robust and efficient and yet, despite these highly desirable theoretical properties, they are rarely used in practice. This is because the performance of these estimators is rarely guaranteed per se but obtained by placing a suitable value on some tuning parameter. Hence there is a risk involved in implementing these methods because if the value chosen for the tuning parameter is inappropriate for the data to which the method is applied, the resulting estimators may not have the desired theoretical properties and could even perform less well than one of the simpler, more widely used alternatives. There are currently no data-based methods available for deciding what value one should place on these tuning parameters hence the primary aim of this research is to develop an objective way of selecting values for the tuning parameters in minimum distance estimators so that the full potential of these estimators might be realised. This new method was initially developed to optimise the performance of the density power divergence estimator, which was proposed by Basu, Harris, Hjort and Jones [3]. The results were very promising so the method was then applied to two other minimum distance estimators and the results compared.
17
Vann, Bugmann Davi. "Retrieval, action and the representation of distance in cognitive maps." Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/2301.
Full textAbstract:
This thesis examines the context effects on retrieval, and the influence of action on the representation of distance in cognitive maps. It is proposed that bias in distance estimation is a function of the contexts of retrieval that trigger the representation of action in memory during evaluation tasks. The proposal is consistent with embodied cognition evidence that suggests that actions are implicitly a part of the representation, and will be naturally extracted as part of the retrieval process. The experimental work presented examines two different contextual cues; the frequency of visitation to landmarks, and the importance of activity performed at landmarks. Each cue primes differently the conceptualisation of landmarks prior to making distance estimation. This priming facilitates memory access, which fleshes out relevant spatial information from cognitive maps that are used in distance estimation and route description. This proposal was examined in a series of four experiments that employed structured interviews. Participants had to rate landmarks based on frequency of visitation criteria or importance of activity criteria, or both. They then made verbal distance estimations and route descriptions. The results found implicate the involvement of action representation. The involvement of action in cognitive process was empirically investigated in three further experiments. A new methodology was developed featuring the use of a blindfold, linguistic descriptions, and control of actual movements. Blindfolded participants learned new environments through verbal descriptions by imagining themselves walking in time with the metronome beats. During turns, they were carefully moved. Following instructions, they performed an action at mid-route. Their memories for the newly learned environments were tested through recalls and measured again with the metronome beats. The results found were consistent with explanations based on network-map theory. They implicate attentional processes as an intrinsic part of the cognitive mechanism, and the strings of the network-map as the actual motor program that executes the movement. These results are discussed in relation to the nature of cognitive maps.
18
Richardson, Adam R. "The Effect Of Feedback Training On Distance Estimation In Virtual Environments." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1074183671.
Full text
19
Rowland, James H. "The effects of texture on distance estimation in synthetic environments." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA362882.
Full textAbstract:
Thesis (M.S. in Operations Research) Naval Postgraduate School, March 1999."March 1999". Thesis advisor(s): William K. Krebs, Rudolph P. Darken. Includes bibliographical references (p. 49-53). Also available online.
20
Larsson, Johan. "Distance Estimation and Positioning Based on Bluetooth Low Energy Technology." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174857.
Full textAbstract:
This thesis deals with location determining, also known as positioning, using Bluetooth Low energy radio. The goal is to implement a low power low cost indoor positioning system which utilize existing hardware. Two main methods are investigated and their viability assessed. Previous efforts with indoor positioning systems concentrate on statistical fingerprinting methods, mainly using 802.11 (WLAN) as the platform. Some efforts have been made with purely signal strength based positioning, but indoor environments have shown to work unfavorably for these kinds of methods.
21
Philippot, Luc. "Parameter estimation and error estimation for line fault location and distance protection in power transmission systems." Doctoral thesis, Universite Libre de Bruxelles, 1995. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212533.
Full text
22
Bigel, Marla G. "The estimation of distance, direction and self-position through nonvisual locomotion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0018/NQ38223.pdf.
Full text
23
McGuire, Grainne. "Statistical methods for DNA sequences : detection of recombination and distance estimation." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/11128.
Full textAbstract:
Two problems in phylogenetics are considered here: the detection of evidence of recombination in DNA sequence multiple alignments and the improved estimation of confidence intervals for genetic distance estimators. Recombination between distinct species can result in mosaic sequences which often invalidate a simple tree-like model for between-species relationships. A graphical method based on pairwise distances and least squares is proposed as an initial scan of data sets for evidence of recombination prior to a phylogenetic analysis. A Bayesian model of recombination for data sets with a small number of species is described, which allows Hidden Markov model theory to be used to carry out computations (e.g., the calculation of the maximum a posteriori estimate). Accurate estimation of confidence intervals for genetic distance estimators is important for comparing the relative rates of nucleotide substitution in different regions of DNA or for estimating the time since the most recent common ancestor. Two approximations to the sampling distributions of distance estimators are proposed. The first is a transformation of a normal density and may be applied to one-parameter models of nucleotide substitution only; this yields very accurate approximations to confidence intervals for a large range of distances. The second is the saddlepoint approximation which has a wider range of applicability (applicable to some two and three parameter models) and also performs well for a range of distances.
24
Azevedo, Glauco Gomes de. "Distance estimation for mixed continuous and categorical data with missing values." reponame:Repositório Institucional do FGV, 2018. http://hdl.handle.net/10438/24742.
Full textAbstract:
Submitted by Glauco Gomes de Azevedo (glaucogazevedo@gmail.com) on 2018-08-28T20:54:50Z
No. of bitstreams: 1
dissertacao_glauco_azevedo.pdf: 1909706 bytes, checksum: 6636e75aa9da1db2615932f064fd1138 (MD5)Approved for entry into archive by Janete de Oliveira Feitosa (janete.feitosa@fgv.br) on 2018-09-10T19:38:08Z (GMT) No. of bitstreams: 1 dissertacao_glauco_azevedo.pdf: 1909706 bytes, checksum: 6636e75aa9da1db2615932f064fd1138 (MD5)
Made available in DSpace on 2018-09-12T17:39:51Z (GMT). No. of bitstreams: 1 dissertacao_glauco_azevedo.pdf: 1909706 bytes, checksum: 6636e75aa9da1db2615932f064fd1138 (MD5) Previous issue date: 2018-06-04
Neste trabalho é proposta uma metodologia para estimar distâncias entre pontos de dados mistos, contínuos e categóricos, contendo dados faltantes. Estimação de distâncias é a base para muitos métodos de regressão/classificação, tais como vizinhos mais próximos e análise de discriminantes, e para técnicas de clusterização como k-means e k-medoids. Métodos clássicos para manipulação de dados faltantes se baseiam em imputação pela média, o que pode subestimar a variância, ou em métodos baseados em regressão. Infelizmente, quando a meta é a estimar a distância entre observações, a imputação de dados pode performar de modo ineficiente e enviesar os resultados na direção do modelo. Na proposta desse trabalho, estima-se a distância dos pares diretamente, tratando os dados faltantes como aleatórios. A distribuição conjunta dos dados é aproximada utilizando um modelo de mistura multivariado para dados mistos, contínuos e categóricos. Apresentamentos um algoritmo do tipo EM para estimar a mistura e uma metodologia geral para estimar a distância entre observações. Simulações mostram que um método proposto performa tanto dados simulados, como reais.
In this work we propose a methodology to estimate the pairwise distance between mixed continuous and categorical data with missing values. Distance estimation is the base for many regression/classification methods, such as nearest neighbors and discriminant analysis, and for clustering techniques such as k-means and k-medoids. Classical methods for handling missing data rely on mean imputation, that could underestimate the variance, or regression-based imputation methods. Unfortunately, when the goal is to estimate the distance between observations, data imputation may perform badly and bias the results toward the data imputation model. In this work we estimate the pairwise distances directly, treating the missing data as random. The joint distribution of the data is approximated using a multivariate mixture model for mixed continuous and categorical data. We present an EM-type algorithm for estimating the mixture and a general methodology for estimating the distance between observations. Simulation shows that the proposed method performs well in both simulated and real data.
25
Kim, Tae-Min. "New estimation of caisson sliding distance for improvement of breakwater reliability design." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145347.
Full text
26
Canelhas, Daniel Ricão. "Truncated Signed Distance Fields Applied To Robotics." Doctoral thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-59369.
Full textAbstract:
This thesis is concerned with topics related to dense mapping of large scale three-dimensional spaces. In particular, the motivating scenario of this work is one in which a mobile robot with limited computational resources explores an unknown environment using a depth-camera. To this end, low-level topics such as sensor noise, map representation, interpolation, bit-rates, compression are investigated, and their impacts on more complex tasks, such as feature detection and description, camera-tracking, and mapping are evaluated thoroughly. A central idea of this thesis is the use of truncated signed distance fields (TSDF) as a map representation and a comprehensive yet accessible treatise on this subject is the first major contribution of this dissertation. The TSDF is a voxel-based representation of 3D space that enables dense mapping with high surface quality and robustness to sensor noise, making it a good candidate for use in grasping, manipulation and collision avoidance scenarios. The second main contribution of this thesis deals with the way in which information can be efficiently encoded in TSDF maps. The redundant way in which voxels represent continuous surfaces and empty space is one of the main impediments to applying TSDF representations to large-scale mapping. This thesis proposes two algorithms for enabling large-scale 3D tracking and mapping: a fast on-the-fly compression method based on unsupervised learning, and a parallel algorithm for lifting a sparse scene-graph representation from the dense 3D map. The third major contribution of this work consists of thorough evaluations of the impacts of low-level choices on higher-level tasks. Examples of these are the relationships between gradient estimation methods and feature detector repeatability, voxel bit-rate, interpolation strategy and compression ratio on camera tracking performance. Each evaluation thus leads to a better understanding of the trade-offs involved, which translate to direct recommendations for future applications, depending on their particular resource constraints.
27
Oravetz, Christopher. "Human estimation of slope, distance, and height of terrain in simulated lunar conditions." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/47809.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 161-166).
As NASA's Vision for Space Exploration seeks to explore mountainous regions near the southern pole through frequent, long excursions, astronauts will require accurate navigational assistance. Current and future technology, including LIDAR data, laser rangefinders, and path planning programs will likely be available; however, the human's own perception of the terrain may affect their confidence in these instruments and be necessary during emergency situations. These unique lunar conditions are expected to affect human perception: the lack of an atmosphere (inhibiting the use of aerial perspective as a distance cue and causing the formation of deep cast shadows), the non-Lambertian regolith reflectance properties, the lack of familiar objects, and the physiological effects of reduced gravity. This project examines the inherent errors humans make when judging the slope, distance, and height of terrain, both on the Earth in a lunar-like environment and on the Moon using photographs from the Apollo missions. Five experiments were conducted in field and Virtual Reality (VR) environments. The effects of true slope, true distance, and sun elevation on slope estimates were determined using visual and motor responses in a lunar-like Utah environment and reproduced in a VR environment using synoptically viewed images in two body positions, under normal and lunar Gz loading conditions. The effects of true slope, distance, and body position on slope, distance, and height estimates of synoptically viewed Apollo panoramic images were measured and compared to measurements obtained from topographical maps. Systematic and random errors were determined for all estimates. Slope estimate comparisons were made between lunar-like and lunar terrain and also between lunar hills and craters. Slope was significantly overestimated in the field study by 130 - 230 with large between-subject errors.
(cont.) Lunar-like field and VR slope estimates were not significantly different from each other. Slope estimates were significantly greater at lower sun elevations and closer distances in the Lunar-like VR Study. Both slope and distance estimates were significantly greater from a lunar Gz supine position. Lunar distance estimates varied largely and slope estimation errors were significantly greater for craters than for hills. A new relationsihp between hill shape and perceived steepness was also discovered. The recommendations of this study include the development of a VR training tool to calibrate an astronaut's slope, distance, and height perception prior to lunar missions and future field studies at Devon Island to determine the effect of hill shape on estimates and to determine the regression coefficients of sun elevation and distance variables to be used in a model integrated with rangefinding devices in a Heads-Up-Display (HUD).
by Christopher Oravetz.
S.M.
28
Ahmad, Husain Abdulrahman. "Dynamic Braking Control for Accurate Train Braking Distance Estimation under Different Operating Conditions." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19322.
Full textAbstract:
The application of Model Reference Adaptive Control (MRAC) for train dynamic braking is investigated in order to control dynamic braking forces while remaining within the allowable adhesion and coupler forces. This control method can accurately determine the train braking distance. One of the critical factors in Positive Train Control (PTC) is accurately estimating train braking distance under different operating conditions. Accurate estimation of the braking distance will allow trains to be spaced closer together, with reasonable confidence that they will stop without causing a collision. This study develops a dynamic model of a train consist based on a multibody formulation of railcars, trucks (bogies), and suspensions. The study includes the derivation of the mathematical model and the results of a numerical study in Matlab. A three-railcar model is used for performing a parametric study to evaluate how various elements will affect the train stopping distance from an initial speed. Parameters that can be varied in the model include initial train speed, railcar weight, wheel-rail interface condition, and dynamic braking force. Other parameters included in the model are aerodynamic drag forces and air brake forces. An MRAC system is developed to control the amount of current through traction motors under various wheel/rail adhesion conditions while braking. Minimizing the braking distance of a train requires the dynamic braking forces to be maximized within the available wheel/rail adhesion. Excessively large dynamic braking can cause wheel lockup that can damage the wheels and rail. Excessive braking forces can also cause large buff loads at the couplers. For DC traction motors, an MRAC system is used to control the current supplied to the traction motors. This motor current is directly proportional to the dynamic braking force. In addition, the MRAC system is also used to control the train speed by controlling the synchronous speed of the AC traction motors. The goal of both control systems for DC and AC traction motors is to apply maximum available dynamic braking while avoiding wheel lockup and high coupler forces. The results of the study indicate that the MRAC system significantly improves braking distance while maintaining better wheel/rail adhesion and coupler dynamics during braking. Furthermore, according to this study, the braking distance can be accurately estimated when MRAC is used. The robustness of the MRAC system with respect to different parameters is investigated, and the results show an acceptable robust response behavior.
Ph. D.
29
Lescornel, Hélène. "Covariance estimation and study of models of deformations between distributions with the Wasserstein distance." Toulouse 3, 2014. http://www.theses.fr/2014TOU30045.
Full textAbstract:
La première partie de cette thèse est consacrée à l'estimation de covariance de processus stochastiques non stationnaires. Le modèle étudié amène à estimer la covariance du processus dans différents espaces vectoriels de matrices. Nous étudions dans le chapitre 3 une méthode de sélection de modèle par minimisation d'un critère pénalisé en utilisant des inégalités de concentration, et le chapitre 4 présente une méthode basée sur l'estimation sans biais du risque. Dans les deux cas des inégalités oracles sont obtenues. La seconde partie de cette thèse concerne l'étude de modèles de déformations entre distributions. On suppose observer une quantité aléatoire epsilon à travers une fonction de déformation. C'est l'importance de la déformation, représentée par un paramètre theta, que l'on cherche à retrouver. Nous présentons plusieurs méthodes d'estimation basées sur la distance de Wasserstein en alignant les lois des observations pour retrouver le paramètre de déformation. Dans le cas où les variables aléatoires sont à valeurs réelles, le chapitre 7 donne des propriétés de consistance pour un M-estimateur et sa distribution asymptotique. On y utilise des techniques de Hadamard différentiabilité pour appliquer une Delta-Méthode fonctionnelle. Le chapitre 8 concerne l'étude d'un estimateur de type Robbins-Monro et présente des propriétés de convergence pour un estimateur à noyau de la densité de la variable epsilon obtenu à l'aide des observations. Le modèle est généralisé à des variables dans des espaces métriques complets dans le chapitre 9, puis, dans l'optique de créer un test d'adéquation, le chapitre 10 donne des résultats sur la distribution asymptotique d'une statistique de testThe first part of this thesis concerns the covariance estimation of non stationary processes. We are estimating the covariance in different vectorial spaces of matrices. In Chapter 3, we give a model selection procedure by minimizing a penalized criterion and using concentration inequalities, and Chapter 4 presents an Unbiased Risk Estimation method. In both cases we give oracle inequalities. The second part deals with the study of models of deformation between distributions. We assume that we observe a random quantity epsilon through a deformation function. The importance of the deformation is represented by a parameter theta that we aim to estimate. We present several methods of estimation based on the Wasserstein distance by aligning the distributions of the observations to recover the deformation parameter. In the case of real random variables, Chapter 7 presents properties of consistency for a M-estimator and its asymptotic distribution. We use Hadamard differentiability techniques to apply a functional Delta method. Chapter 8 concerns a Robbins-Monro estimator for the deformation parameter and presents properties of convergence for a kernel estimator of the density of the variable epsilon obtained with the observations. The model is generalized to random variables in complete metric spaces in Chapter 9. Then, in the aim to build a goodness of fit test, Chapter 10 gives results on the asymptotic distribution of a test statistic
30
Richardson, Adam. "THE INFLUENCE OF PRIOR INTERACTION WITH AN IMMERSIVE VIRTUAL ENVIRONMENT ON USER’S DISTANCE ESTIMATES." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1161020618.
Full text
31
Braasch, Michael S. "Current developments in signal modeling of the precision distance measuring equipment." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182283477.
Full text
32
Anver, Haneef Mohamed. "Mean Hellinger Distance as an Error Criterion in Univariate and Multivariate Kernel Density Estimation." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/dissertations/161.
Full textAbstract:
Ever since the pioneering work of Parzen the mean square error( MSE) and its integrated form (MISE) have been used as the error criteria in choosing the bandwidth matrix for multivariate kernel density estimation. More recently other criteria have been advocated as competitors to the MISE, such as the mean absolute error. In this study we define a weighted version of the Hellinger distance for multivariate densities and show that it has an asymptotic form, which is one-fourth the asymptotic MISE under weak smoothness conditions on the multivariate density f. In addition the proposed criteria give rise to a new data-dependent bandwidth matrix selector. The performance of the new data-dependent bandwidth matrix selector is compared with other well known bandwidth matrix selectors such as the least squared cross validation (LSCV) and the plug-in (HPI) through simulation. We derived a closed form formula for the mean Hellinger distance (MHD) in the univariate case. We also compared via simulation mean weighted Hellinger distance (MWHD) and the asymptotic MWHD, and the MISE and the asymptotic MISE for both univariate and bivariate cases for various densities and sample sizes.
33
Wallebäck, Peter. "Fuel Level Estimation for Heavy Vehicles using a Kalman Filter." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15702.
Full textAbstract:
The object with this project is to develop a more accurate way to measure the level in the fuel tank in Scaniavehicles. The level should be displayed for the driver and a warning system be implemented to make the driveraware if the fuel level is too low. Furthermore a main goal is to develop an estimation of the distance that thevehicle could travel before refueling is needed.The fuel level estimation system is modeled using Matlab Simulink and simulated with measurement datacollected from real driving scenarios. After evaluating the system it is implemented in one of the electricalcontrol units located on a test vehicle which communicates with other systems. After implementation more testsare performed with the test vehicle to verify that the same functionality achieved during simulations is achievedusing the system implemented in a vehicle.The fuel level estimated with a KF (Kalman filter) that uses fuel consumption and level measurement results ingood performance. A more stable level estimate is achieved and a negative elevation of the estimate most of thetime, as a result of fuel use. Compared to the method Scania vehicles estimate their fuel level with today thenew level estimate is more steady and not that easily affected by fuel movements. The KF is more demanding interms of memory allocation, processor speed and inputs needed, which has to be considered when comparingboth methods. Another disadvantage with the KF is that it is dependent on the samples from the fuel levelsensor to get an initial estimate during startup.Furthermore the KF is easily expanded with more inputs that use information from other sensors on other parts of the vehicle.
34
Gottleben, Emil. "Vision Based Control of Autonomous UAV." Thesis, Linköpings universitet, Reglerteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128870.
Full textAbstract:
This master thesis investigates the problem of making an unmanned aerial vehicle(uav) follow a person or a group of persons while keeping a fixed distance tothe chosen target. The purpose of this thesis is to give a proof of concept prototypeof how such a system would work to achieve that task. The main problemconsists of controlling the uav based on visual input from a camera. With thehelp of a visual object detection and tracking system, the image coordinates ofthe targets can be found. An algorithm was developed to calculate the target’sworld position based on its image coordinates and the world position and orientationof the uav. A control system was implemented that uses that uses thepositional information to set the velocity of the uav, if its position needs to bechanged. Several strategies for handling groups of targets were investigated. Inaddition a simulator was developed that can be used to simulate the image coordinatesof a target when the world position of the target is known. The systemwas tested during live flights, using a high precision motion capture system forreference. The results were mainly positive in showing proof of concept and evenshowing a relatively high level of precision.
35
D'Ambrosio, Philip. "A Differential Geometry-Based Algorithm for Solving the Minimum Hellinger Distance Estimator." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32228.
Full textAbstract:
Robust estimation of statistical parameters is traditionally believed to exist in a trade space between robustness and efficiency. This thesis examines the Minimum Hellinger Distance Estimator (MHDE), which is known to have desirable robustness properties as well as desirable efficiency properties. This thesis confirms that the MHDE is simultaneously robust against outliers and asymptotically efficient in the univariate location case. Robustness results are then extended to the case of simple linear regression, where the MHDE is shown empirically to have a breakdown point of 50%. A geometric algorithm for solution of the MHDE is developed and implemented. The algorithm utilizes the Riemannian manifold properties of the statistical model to achieve an algorithmic speedup. The MHDE is then applied to an illustrative problem in power system state estimation. The power system is modeled as a structured linear regression problem via a linearized direct current model; robustness results in this context have been investigated and future research areas have been identified from both a statistical perspective as well as an algorithm design standpoint.Master of Science
36
Shafi, Muhammad. "Face pose estimation in monocular images." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/5894.
Full textAbstract:
People use orientation of their faces to convey rich, inter-personal information. For example, a person will direct his face to indicate who the intended target of the conversation is. Similarly in a conversation, face orientation is a non-verbal cue to listener when to switch role and start speaking, and a nod indicates that a person has understands, or agrees with, what is being said. Further more, face pose estimation plays an important role in human-computer interaction, virtual reality applications, human behaviour analysis, pose-independent face recognition, driver s vigilance assessment, gaze estimation, etc. Robust face recognition has been a focus of research in computer vision community for more than two decades. Although substantial research has been done and numerous methods have been proposed for face recognition, there remain challenges in this field. One of these is face recognition under varying poses and that is why face pose estimation is still an important research area. In computer vision, face pose estimation is the process of inferring the face orientation from digital imagery. It requires a serious of image processing steps to transform a pixel-based representation of a human face into a high-level concept of direction. An ideal face pose estimator should be invariant to a variety of image-changing factors such as camera distortion, lighting condition, skin colour, projective geometry, facial hairs, facial expressions, presence of accessories like glasses and hats, etc. Face pose estimation has been a focus of research for about two decades and numerous research contributions have been presented in this field. Face pose estimation techniques in literature have still some shortcomings and limitations in terms of accuracy, applicability to monocular images, being autonomous, identity and lighting variations, image resolution variations, range of face motion, computational expense, presence of facial hairs, presence of accessories like glasses and hats, etc. These shortcomings of existing face pose estimation techniques motivated the research work presented in this thesis. The main focus of this research is to design and develop novel face pose estimation algorithms that improve automatic face pose estimation in terms of processing time, computational expense, and invariance to different conditions.
37
Hautiere, Nicolas. "Détection des conditions de visibilité et estimation de la distance de visibilité par vision embarquée." Phd thesis, Université Jean Monnet - Saint-Etienne, 2005. http://tel.archives-ouvertes.fr/tel-00068743.
Full textAbstract:
Les conditions météorologiques dégradées, en particulier le brouillard, posent un problème à la fois aux automobilistes qui ont tendance à surestimer les distances intervéhiculaires, mais aussi aux capteurs extéroceptifs qui fonctionnent de manière dégradée. La détection et la quantification des conditions de visibilité constituent donc un enjeu fort en termes de sécurité routière. Nous proposons deux techniques complémentaires permettant d'effectuer une mesure embarquée de la distance de visibilité par des techniques d'analyse d'images effectuées en temps réel. Elles reposent sur une définition de la distance de visibilité météorologique, distance au delà de laquelle un objet noir de dimensions suffisantes ne peut être reconnu de jour sur le ciel à l'horizon. La première technique, fondée sur un modèle de diffusion atmosphérique, détecte et estime la densité du brouillard diurne en utilisant une seule caméra. La deuxième technique, mettant à profit une propriété générale de l'atmosphère, est capable d'estimer la distance de visibilité par toutes conditions météorologiques, de jour et de nuit, en utilisant, pour sa part, un capteur stéréoscopique. Nous évaluons, d'une part, les méthodes à l'aide d'images réelles acquises sur véhicule sous différentes conditions météorologiques, ce qui constitue une évaluation qualitative du travail réalisé. Nous évaluons d'autre part les méthodes à l'aide d'images acquises sur un site spécifique équipé de mires de référence, conçu et réalisé sur les pistes d'essai de Satory, ce qui constitue une évaluation quantitative.
38
Graham, Gerhard. "An estimation of seismic anisotropy in the crust from three different time and distance scales." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12056.
Full textAbstract:
In this thesis shear-wave splitting is analyzed in shear-wave arrivals from three different time and distance scales to identify the occurrence and extent of anisotropy in the crust. The refracted shear waves recorded by the closely spaced seismic network of the third Turkish Dilatancy Project from regional earthquakes in western Turkey have similar polarizations to those previously observed above local earthquakes, but with less scatter and substantially greater time delays (up to 1.0 s) between the split shear waves. This is interpreted as indicative of the presence of anisotropy in the lower crust with similar anisotropic symmetry to the crack-induced anisotropy of the upper half of the crust. Mine tremors in the deep gold mine of South Africa have seismic magnitudes ranging from ML -4 to ML more than 5. An examination of three-component acceleration and velocity seismograms recorded on the surface above an active gold mine indicates that the shear-wave polarizations have a nearly uniform alignment. This combined with the measured time delays are consistent with shear waves propagating through the effective anisotropy of parallel, vertical microcracks throughout the rockmass. It is concluded that the dry fractures caused by the high stresses during normal mining processes have negligible effect on the shear-wave polarizations at the wavelengths at which shear waves are recorded at the surface. The anisotropy observed at the surface appears to be due to microcracks aligned by the regional stress regime rather than disturbances in the local stress regime due to mining operations. High frequency subsurface recordings of mine tremors that occur in confined volumes surrounding the work face of the mining excavations show shear-wave splitting over distances of a few hundred metres. Plate Carée cylindrical projections of the observed shear-wave polarizations and time delays were compared with theoretical patterns of polarizations and time delays from different synthetic models. From this comparison it became clear that a model containing fluid-filled, non-vertical cracks striking approximately north-south could be used to produce the observed polarizations and time delays to some extent.
39
Hautière, Nicolas. "Détection des conditions de visibilité et estimation de la distance de visibilité par vision embarquée." Saint-Etienne, 2005. http://www.theses.fr/2005STET4006.
Full textAbstract:
Les conditions météorologiques dégradées, en particulier le brouillard, posent un problème à la fois aux automobilistes qui ont tendance à surestimer les distances intervéhiculaires, mais aussi aux capteurs extéroceptifs qui fonctionnent de manière dégradée. La détection et la quantification des conditions de visibilité constituent donc un enjeu fort en termes de sécurité routière. Nous proposons deux techniques complémentaires permettant d'effectuer une mesure embarquée de la distance de visibilité par des techniques d'analyse d'images effectuées en temps réel. Elles reposent sur une définition de la distance de visibilité météorologique, distance au delà de laquelle un objet noir de dimensions suffisantes ne peut être reconnu de jour sur le ciel à l'horizon. La première technique, fondée sur un modèle de diffusion atmosphérique, détecte et estime la densité du brouillard diurne en utilisant une seule caméra. La deuxième technique, mettant à profit une propriété générale de l'atmosphère, est capable d'estimer la distance de visibilité par toutes conditions météorologiques, de jour et de nuit, en utilisant, pour sa part, un capteur stéréoscopique. Nous évaluons, d'une part, les méthodes à l'aide d'images réelles acquises sur véhicule sous différentes conditions météorologiques, ce qui constitue une évaluation qualitative du travail réalisé. Nous évaluons d'autre part les méthodes à l'aide d'images acquises sur un site spécifique équipé de mires de référence, conçu et réalisé sur les pistes d'essai de Satory, ce qui constitue une évaluation quantitativeThe adverse weather conditions, in particular the fog, pose a problem for the drivers, who tend to overestimate distances, but also to the exteroceptive sensors which work less well. The detection and the quantification of the visibility conditions thus constitute a strong stake in terms of road safety. We propose two complementary methods onboard a vehicle aiming to estimate the visibility distance by using real time image analyses techniques. Both are based on the definition of the meteorological visibility distance, which is the greatest distance at which a black object of suitable dimensions can be recognized by day against the horizon sky. The first technique, using a model of atmospheric diffusion, detects and estimates the density of daytime fog by using a single camera. The second technique, using a generic property of the atmosphere, is able to estimate day and night the visibility distance under all meteorological conditions by using a stereoscopic sensor. On one hand, we evaluate our methods, thanks to several video sequences grabbed under different meteorological conditions, what constitutes a qualitative evaluation of the work done. On the other hand, we evaluate the methods, thanks to actual images of a specific site equipped with reference targets, which has been conceived and realized on the test facilities of Satory, what constitutes a quantitative evaluation
40
Pérez, J. M., M. Sarasa, G. Moço, J. E. Granados, J. P. Crampe, E. Serrano, L. Maurino, P. G. Meneguz, A. Afonso, and R. Alpizar-Jara. "The effect of data analysis strategies in density estimation of mountain ungulates using distance sampling." Bachelor's thesis, Italian Journal of Zoology, 2014. http://hdl.handle.net/10174/16907.
Full textAbstract:
Distance sampling is being extensively used to estimate the abundance of animal populations. Nevertheless, the great variety of ways in which data can be analyzed may limit comparisons due to the lack of standardization of such protocols. In this study, the influence of analytical procedures for distance sampling data on density estimates and their precision was assessed. We have used data from 21 surveys of mountain ungulates in the Iberian Peninsula, France and the Italian Alps. Data from such surveys were analyzed with the program Distance 6.0. Our analyses show that estimated density can be higher for higher levels of data truncation. We also confirm that the estimates tend to be more precise when data are analyzed without binning and without truncating. We found no evidence of size biased sampling as group size and distances were uncorrelated in most of our surveys. Despite distance sampling being a fairly robust methodology, it can be sensitive to some data analysis strategies.
41
Kakarlapudi, Geetha. "Analysis of beacon triangulation in random graphs." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1447.
Full textAbstract:
Our research focusses on the problem of finding nearby peers in the Internet.
We focus on one particular approach, Beacon Triangulation that is widely used to
solve the peer-finding problem. Beacon Triangulation is based on relative distances
of nodes to some special nodes called beacons. The scheme gives an error when a
new node that wishes to join the network has the same relative distance to two or
more nodes. One of the reasons for the error is that two or more nodes have the
same distance vectors. As a part of our research work, we derive the conditions to
ensure the uniqueness of distance vectors in any network given the shortest path
distribution of nodes in that network. We verify our analytical results for G(n, p)
graphs and the Internet. We also derive other conditions under which the error in the
Beacon Triangulation scheme reduces to zero. We compare the Beacon Triangulation
scheme to another well-known distance estimation scheme known as Global Network
Positioning (GNP).
42
Stolle, Martin Tobias. "Vers le vol à voile longue distance pour drones autonomes." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0006.
Full textAbstract:
Les petit drones à voilure fixe rendent services aux secteurs de la recherche, de l'armée et de l'industrie, mais souffrent toujours de portée et de charge utile limitées. Le vol thermique permet de réduire la consommation d'énergie. Cependant,sans télédétection d'ascendances, un drone ne peut bénéficier d'une ascendance qu'en la rencontrant par hasard. Dans cette thèse, un nouveau cadre pour le vol à voile longue distance autonome est élaboré, permettant à un drone planeur de localiser visuellement des ascendances sous-cumulus et d’en récolter l'énergie de manière efficace. S'appuyant sur le filtre de Kalman non parfumé, une méthode de vision monoculaire est établie pour l'estimation des paramètres d’ascendances. Sa capacité de fournir des estimations convergentes et cohérentes est évaluée par des simulations Monte Carlo. Les incertitudes de modèle, le bruit de traitement de l'image et les trajectoires de l'observateur peuvent dégrader ces estimés. Par conséquent, un deuxième axe de cette thèse est la conception d'un planificateur de trajectoire robuste basé sur des cartes d'ascendances. Le planificateur fait le compromis entre le temps de vol et le risque d’un atterrissage forcé dans les champs tout en tenant compte des incertitudes d'estimation dans le processus de prise de décision. Il est illustré que la charge de calcul du planificateur de trajectoire proposé est réalisable sur une plate-forme informatique peu coûteuse. Les algorithmes proposés d’estimation ainsi que de planification sont évalués conjointement dans un simulateur de vol à 6 axes, mettant en évidence des améliorations significatives par rapport aux vols à voile longue distance autonomes actuelsSmall fixed-wing Unmanned Aerial Vehicles (UAVs) provide utility to research, military, and industrial sectors at comparablyreasonable cost, but still suffer from both limited operational ranges and payload capacities. Thermal soaring flight for UAVsoffers a significant potential to reduce the energy consumption. However, without remote sensing of updrafts, a glider UAVcan only benefit from an updraft when encountering it by chance. In this thesis, a new framework for autonomous cross-country soaring is elaborated, enabling a glider UAV to visually localize sub-cumulus thermal updrafts and to efficiently gain energy from them.Relying on the Unscented Kalman Filter, a monocular vision-based method is established, for remotely estimatingsub-cumulus updraft parameters. Its capability of providing convergent and consistent state estimates is assessed relyingon Monte Carlo Simulations. Model uncertainties, image processing noise, and poor observer trajectories can degrade theestimated updraft parameters. Therefore, a second focus of this thesis is the design of a robust probabilistic path plannerfor map-based autonomous cross-country soaring. The proposed path planner balances between the flight time and theoutlanding risk by taking into account the estimation uncertainties in the decision making process. The suggested updraftestimation and path planning algorithms are jointly assessed in a 6 Degrees Of Freedom simulator, highlighting significantperformance improvements with respect to state of the art approaches in autonomous cross-country soaring while it is alsoshown that the path planner is implementable on a low-cost computer platform
43
Sorwar, Golam 1969. "A novel distance-dependent thresholding strategy for block-based performance scalability and true object motion estimation." Monash University, Gippsland School of Computing and Information Technology, 2003. http://arrow.monash.edu.au/hdl/1959.1/5510.
Full text
44
Chen, Chien-Chih, and 陳建智. "An Architecture for Network Distance Estimation Service." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/64714617905966489604.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
89
With the prevailing of the Internet and the coming of the wideband era, there are increasing different types of services provided on the Internet. In order to provide better qualities, some service providers provide services in more than one place, i.e., clients can receive the same services in several different places. For example, some corporations own several mirror web sites around the world, and they all provide the same services. To receive better services and to decrease the wasted bandwidth, clients have to choose the nearest sites. Unfortunately, clients have to do the measurement tasks themselves in order to get the distance between any two nodes in the Internet. There is no easy way to know the distance between any two nodes in the Internet. This paper presents an approach to estimate the distance between any two nodes in the Internet, a so-called Network Distance Estimation Service (NDES). The main idea of this paper is to rely on a set of probing machines, to measure the distances between these probing machines and to estimate the distance between any two nodes in the Internet by the distances measured by these machines. To get more accurate distance information, we have to allocate more probing machines in the Internet. To decrease the number of distance measurements, we have to cluster the probing machines in a hierarchical manner. This paper presents the clustering methods, both the network topology is known and unknown. Our main concern is to decrease the number of distance measurements and to get an appropriate clustering result.
45
Tzeng, Jau_rong, and 曾昭絨. "Distance Estimation in Range-free Localization Schemes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/13140429179638895535.
Full textAbstract:
碩士國立中央大學
資訊工程研究所
99
In recent years, a number of location - based services have been proposed, such as search, target tracking and rescue. An accurate and efficient localization algorithm is crucial in supporting all these services in wireless networks. There are many different localization algorithms proposed in the literature. Due to the cost and limitation of hardware on sensing nodes, range-free localization schemes have received great deal of attention. Such schemes include two phases: distance estimation and triangulation. A better distance estimation helps improve the accuracy of localization. In this thesis, we propose a novel scheme for single hop and range estimation. Additionally, we propose the first correction scheme to estimate multi-hop range by mean of single hop range estimations. Compared to other range-free distance estimation, our scheme reduces the error significantly, especially when the number of anchors is low.
46
"Minimum Distance Estimation in Categorical Conditional Independence Models." Thesis, 2012. http://hdl.handle.net/1911/70285.
Full textAbstract:
One of the oldest and most fundamental problems in statistics is the analysis of cross-classified data called contingency tables. Analyzing contingency tables is typically a question of association - do the variables represented in the table exhibit special dependencies or lack thereof? The statistical models which best capture these experimental notions of dependence are the categorical conditional independence models; however, until recent discoveries concerning the strongly algebraic nature of the conditional independence models surfaced, the models were widely overlooked due to their unwieldy implicit description. Apart from the inferential question above, this thesis asks the more basic question - suppose such an experimental model of association is known, how can one incorporate this information into the estimation of the joint distribution of the table? In the traditional parametric setting several estimation paradigms have been developed over the past century; however, traditional results are not applicable to arbitrary categorical conditional independence models due to their implicit nature. After laying out the framework for conditional independence and algebraic statistical models, we consider three aspects of estimation in the models using the minimum Euclidean (L2E), minimum Pearson chi-squared, and minimum Neyman modified chi-squared distance paradigms as well as the more ubiquitous maximum likelihood approach (MLE). First, we consider the theoretical properties of the estimators and demonstrate that under general conditions the estimators exist and are asymptotically normal. For small samples, we present the results of large scale simulations to address the estimators' bias and mean squared error (in the Euclidean and Frobenius norms, respectively). Second, we identify the computation of such estimators as an optimization problem and, for the case of the L2E, propose two different methods by which the problem can be solved, one algebraic and one numerical. Finally, we present an R implementation via two novel packages, mpoly for symbolic computing with multivariate polynomials and catcim for fitting categorical conditional independence models. It is found that in general minimum distance estimators in categorical conditional independence models behave as they do in the more traditional parametric setting and can be computed in many practical situations with the implementation provided.
47
Chen, Yu-Chun, and 陳昱均. "Integrated Vehicle and Lane Detection with Distance Estimation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/95350381871632941942.
Full textAbstract:
碩士國立清華大學
資訊工程學系
102
This thesis proposes an Advanced Driver Assistance System (ADAS) that combines vehicle detection, lane detection, and distance estimation in a collaborative manner. Vehicle detection is an important research problem for Advanced Driver Assistance Systems. Most existing methods are based on the sliding window search framework. However, such methods are computationally intensive and easily produce large numbers of false positives because they need to search local windows of different scales at all positions in the image. Our efficient vehicle detection approach dramatically reduces the search space based on the perspective geometry of the road. In the training phase, we locate all possible vehicle regions from several online images by using the standard HOG-based vehicle detector and treat them as vehicle candidates. Then, pairs of vehicle candidates that satisfy the projective geometry constraints are used to estimate a linear vehicle width model. Then an adaptive scan strategy based on the estimated vehicle width model is developed for efficient vehicle detection from an image. The learned vehicle width model provides constraints on the horizon and the lane width at different locations in the image. By exploiting the above geometric constraints, the search space for lane detection can be significantly reduced. We employ local patch constraints along hypothesized lanes extracted from the image to improve the reliability of lane detection. Moreover, we propose a novel algorithm to estimate the vehicle distance from a single image captured form a monocular camera in real time. In our algorithm, we utilize lane prior information of dash lane geometry to estimate the camera pose and the distances to the detected vehicles. Experimental results on real videos show that the proposed system is robust and accurate in terms of vehicle and lane detection as well as vehicle distance estimation from an image. We also show superior accuracies of vehicle and lane detection compared to the previous methods.
48
Chen, Tai-An, and 陳泰安. "Distance Estimation with Mobile Phone Using G-sensors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04408598141984259731.
Full textAbstract:
碩士中原大學
電機工程研究所
101
In this thesis, we propose a study on distance estimation with mobile phone using G-sensors. We get the acceleration data to calculate distance with target through mobile phone equipped with G-sensors. In the thesis, we will present system architecture and two designs focuses. The design focuses are distance estimation and error correction mechanism. At first, we build the system under Android development environment, and use Android development resources to combine with G-sensors. Thus, we use the abundant resources to develop the system. Second, we use G-sensor to get the acceleration and horizontal angle data to calculate distance with target. Based on trigonometric measurements method, we can calculate the distance from acceleration and horizontal angle data. Third, in order to avoid getting the error data, we use error correction mechanisms to reduce the error. In the user interface, it will lead to get the exact data and calculate distance with target. Through the method, we can reduce data error and increase the accuracy of distance estimation. At last, we will prove the feasibility of this system by simulation experiments. We use physical G-sensor device to get acceleration data and calculate object distance by using MATLAB. We will prove the accuracy of distance estimation and show the system interface under Android simulation environment. In this thesis, we propose following contributions: - Expansibility: Under Android development environment, the system has open, abundant resources and hardware assisted. It will provide the development space to the system. - Portability: If you want to measure distance with target, you just complete the action by mobile phone. It does not need many tools in the process of measurement. - Convenience: It just requires a few simple steps to complete distance measurement. It can reduce trouble process of measurement. - Adaptability: Based on distance measurement function, it can apply for any distance measurement cases (e.g., car device, obstacles avoidance robot, indoor location, etc.). - Lower cost: We use popular and cheap mobile phone to develop the system. It is cheaper than professional measuring equipment.
49
Sung, Ming-Chan, and 宋明展. "All Day Front Vehicle Distance Estimation in Highway." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/utz888.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
106
In recent years, people have not only pursues automobile performance but also increases their awareness of safety. Major car manufacturers have also been eager to develop Advanced Driver Assistance Systems (ADAS) to enhance the safety of automobiles. The most important function of an ADAS is to issue warnings and assist driving before a dangerous situation occurs in order to avoid traffic accidents. In this thesis, the image processing methods are used to estimate the distance of the preceding vehicle and a method is proposed to decide whether the front has sufficient light. The lane line is used to find the sky block and then determine if there is enough light in the sky block. In vehicle detection, when lighting is sufficient, the shadow of a vehicle and the rear horizontal bumper are used for detection. The vehicle's two red rear lights are used as a base in low light conditions Finally, in distance estimation, this thesis proposes a novel method different from previous methods based on the ratio of lane width. The proposed method is based on the proportion of height position of the vehicle in a image in order to improve system accuracy and processing speed. The experiment conducted in this thesis is based on 19 driving images taken in highways under various circumstances. In the experiment, the light recognition error took place only when highway sign board and windshield wiper are both located in the light detection area when it is raining.. Fog causes unclear images and therefore results in vehicle recognition errors either.
50
Chang, Yu-Cheng, and 張鈺承. "Distance estimation in low SNR for LiDAR systems." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/p7k73u.
Full textAbstract:
碩士國立交通大學
電子研究所
107
In this thesis, we propose the method that we can obtain the accurate distance between the object and the photon detector by using the photon detection measurement after computational estimation. Obviously, our computational estimation method has better performance compared to Center of Mass(CM) estimation in low SNR with our simulation results. In case that the laser pulse width is larger than the resolution of Time to Digital Converter(TDC), we can get the distance between the object and the photon detector by using weighted computation on the timeline with the laser pulse shape. And then, we can denoise the image with the time correlation of each pixel and its neighbors. Further, we emit the laser with the pseudo random pattern and use computational estimation to get more accurate distance measurement.