• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 83
  • 35
  • 15
  • 15
  • 13
  • 10
  • 5
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 201
  • 66
  • 37
  • 34
  • 25
  • 24
  • 21
  • 19
  • 17
  • 16
  • 15
  • 14
  • 13
  • 13
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Utveckling av Value Stream Mapping : En kvalitativ studie av en lagerverksamhets varuflöde

Axelsson, Casper, Eriksén, Viktor January 2022 (has links)
Företag har länge strävat efter att maximera kundnytta och bygga konkurrenskraft. Ett populärt sätt att göra det på är att använda sig av effektivitetsförbättrande filosofier. Lean Production är en sådan filosofi och den syftar till ett systematiskt förbättringsarbete i tillverkande företag där målet är att identifiera och eliminera slöserier för att bygga en snabbare och mer kvalitativ verksamhet. Det senaste decenniet har en utveckling av Lean Production ägt rum och återfinns nu även i en annan kontext, lagerverksamheter. På grund av e-handelns tillväxt har lagerverksamheter sett ett större behov av att ständigt arbeta med förbättringar och effektivisering. Eftersom Lean Production traditionellt varit anpassad till tillverkande företag har en specifik filosofi kallad Lean Warehousing utvecklats. Inom Lean Production har det arbetats fram vissa verktyg som syftar till att identifiera och eliminera slöserier i tillverkande företag. Dessa verktyg har inte anpassats till Lean Warehousing. Ett sådant verktyg är Value Stream Mapping, som syftar till att visualisera och kartlägga ett företags värdeskapande flöde med målet att identifiera slöserier. Tidigare forskning har visat att Value Stream Mapping har använts i en rad andra kontexter, däremot har ingen studie anpassat verktyget för lagerverksamheter. Detta har lett till studiens forskningsfråga: Hur kan Value Stream Mapping utvecklas för att bättre anpassas till en lagerverksamhet? Den teoretiska referensramen bygger på forskning inom området. Studier och litteratur om Lean Warehousing, lagerverksamheter i stort och om huvudaktiviteten orderplock presenteras. Kapitlet beskriver Value Stream Mapping och hur det använts i tillverkande företag. Vidare har det gjorts en genomgång av tidigare utvecklingar av verktyget och kapitlet avslutas sedan med att introducera ett nytt tillvägagångssätt. Avslutningsvis presenteras studiens resultat. De genomförda kvalitativa intervjuerna med hjälp av den teoretiska referensramen har utmynnat i en utvecklad modell – Warehouse Value Stream Mapping – med kontextspecifika anpassningar i form av mål kopplade till verksamheten och Key Performance Indicators som återspeglar orderplocket i lagerverksamheter. Föreliggande studie synliggör hur en anpassad modell av Value Stream Mapping bör se ut för att bättre kunna användas i lagerverksamheter i syfte att identifiera och eliminera slöseri och därmed effektivisera verksamheten.
152

An Assessment of Hypocenter Errors Associated with the Seismic Monitoring of Induced Hydro-fracturing in Hydrocarbon Reservoirs

Gilliland, Ellen 17 November 2009 (has links)
Expanding the standard, single-well recording geometry used to monitor seismicity during hydro-fracture treatments could provide more accurate hypocenter locations and seismic velocities, improving general reservoir characterization. However, for the real, two-well data set obtained for this project, only S-wave picks were available, and testing resulted in anomalous hypocenter location behavior. This study uses a hypocenter location algorithm and both real and synthetic data sets to investigate how the accuracy of the velocity model, starting hypocenter location, recording geometry, and arrival-time picking error affect final hypocenter locations. Hypocenter locations improved using a velocity model that closely matched the observed sonic log rather than a smoothed version of this model. The starting hypocenter location did not affect the final location solution if both starting and final locations were between the wells. Two solutions were possible when the true solution was not directly between the wells. Adding realistic random picking errors to synthetic data closely modeled the dispersed hypocenter error pattern observed in the real data results. Adding data from a third well to synthetic tests dramatically reduced location error and removed horizontal geometric bias observed in the two-well case. Seismic event data recorded during hydro-fracture treatments could potentially be used for three-dimensional joint hypocenter-velocity tomography. This would require observation wells close enough to earthquakes to record P- and S-wave arrivals or wells at orientations sufficient to properly triangulate hypocenter locations. Simulating results with synthetic tests before drilling could optimize survey design to collect data more effectively and make analysis more useful. / Master of Science
153

LEARNING GRASP POLICIES FOR MODULAR END-EFFECTORS OF MOBILE MANIPULATION PLATFORMS IN CLUTTERED ENVIRONMENTS

Juncheng Li (18418974) 22 April 2024 (has links)
<p dir="ltr">This dissertation presents the findings and research conducted during my Ph.D. study, which focuses on developing grasp policies for modular end-effectors on mobile manipulation platforms operating in cluttered environments. The primary objective of this research is to enhance the performance and accuracy of robotic manipulation systems in complex, real-world scenarios. The work has potential implications for various domains, including the rapidly growing Industry 4.0 and the advancement of autonomous systems in space habitats.</p><p dir="ltr">The dissertation offers a comprehensive literature review, emphasizing the challenges faced by mobile manipulation platforms in cluttered environments and the state-of-the-art techniques for grasping and manipulation. It showcases the development and evaluation of a Modular End-Effector System (MEES) for mobile manipulation platforms, which includes the investigation of object 6D pose estimation techniques, the generation of a deep learning-based grasping dataset for MEES, the development of a suction cup gripper grasping policy (Sim-Suction), the development of a two-finger grasping policy (Sim-Grasp), and the integration of Modular End-Effector System grasping policy (Sim-MEES). The proposed methodology integrates hardware designs, control algorithms, data-driven methods, and large language models to facilitate adaptive grasping strategies that consider the unique constraints and requirements of cluttered environments.</p><p dir="ltr">Furthermore, the dissertation discusses future research directions, such as further investigating the Modular End-Effector System grasping policy. This Ph.D. study aims to contribute to the advancement of robotic manipulation technology, ultimately enabling more versatile and robust mobile manipulation platforms capable of effectively interacting with complex environments.</p>
154

Automatiserat plocksystem för dagligvaruhandel / Automated Picking System for Grocery Stores

Wennerbo, Theodor, Bildhjerd, Martin C. January 2024 (has links)
This is a bachelor's thesis in the area of electrical engineering as well as automation. This thesis investigates motor choice, sensor choices, and the methodology of automating a grocery store picking system prototype. The general structure of the system is composed out of two shelfs with a plane, between them, that is movable in the vertical direction. On the movable plane a conveyor belt was installed. We evaluated the motor choice for the application and the safety aspects of the system to gather a general understanding of potential risk factors involved in realizing a system that can work autonomously. It includes both electrical safety factors as well as mechanical safety factors. Additionally, we considered safety precautions to prevent malfunctions that can lead to these risks. To realize the prototype, a prestudy to investigate motor alternatives was conducted to determine the best motor choice for the application. The chosen motor was a DC steppermotor with snail gearbox. This will ensure simple regulation of the motor to sufficiently handle the weights the system needs to manage. The snail gearbox can eliminate some mechanical risk factors due to its self-locking mechanism, ensuring that if there is an electrical malfunction, such as a power failure, the system will not collapse on itself and drop the payload flat on the floor. Also, a model of the large prototype was made in a 3D-drawing software, which was then 3D-printed and set up to mimic the large prototype. The goal of the miniature model is to test the functionality and evaluate if the algorithms described in this thesis can be preserved and re-used for the large system and prototype.
155

Mappningsstrategi på IKEA:s CDC-lager i Torsvik / Mapping strategy at IKEA:s CDC-Warehouse at Torsvik

Hansson, Alexander, Petersson, Andreas January 2007 (has links)
<p>This study has been assigned by Bengt Hellman who works at the logistic department at IKEA Torsvik just outside of Jönköping. The task has been to develop a new picking strategy for the Oversize area in the CDC-Warehouse. The reason why IKEA wants a new strategy is because they want to minimize the route length for the forklifts when collecting the orders.</p><p>By evaluating the current strategies on other areas in the CDC-storehouse, study literature within this subject and look at restrictions for the storing of goods, we have analyzed how the Oversize area works today. We compared the gathered information, to how it should be done according to the literature to be able to work out a new functional strategy.</p><p>Today, IKEA does not have a working strategy for the oversize area because of lack of time and because all the power has been put on other areas were sales rates are currently higher. This have led to lack of organisation at the Oversize area and items are just put were there is space without first analysing were it should be placed.</p><p>The strategy that we have worked out and introduced to IKEA builds on easiness of understanding the layout, the employees shall know why an item is placed where it is. We have also analyzed which items that are frequently ordered with each other. We have put weight on trying to keep those items as close as we can to minimize the route length for the forklifts. To help IKEA with reorganizations in the future we have made it as easy as we could to move high- and low frequently items around and also introducing new articles in the storehouse, this by the reason that sales rate can change drastically when a new sales campaign is initiated by IKEA</p> / <p>Detta examensarbete är utfört på önskemål av Bengt Hellman som arbetar på logistikavdelningen på IKEA Torsvik utanför Jönköping. Arbetet har gått ut på att ta fram ett nytt förslag på hur de skall placera sina artiklar på plocknivå (vad IKEA kallar för mappning) inne på Oversize avdelningen på IKEA:s CDC-lager. Anledningen till detta är att IKEA vill minska sina körsträckor för plockarna inne på lagret och därmed öka effektiviteten.</p><p>Genom att studera befintliga mappningsstrategier som redan finns på övriga avdelningar på CDC-lagret, litteraturstudier och titta på vilka begränsningar som finns inne på lagret så har vi analyserat nuläget mot teori för att sedan kunna ta fram en ny strategi för hur en fungerande mappning skulle kunna se ut.</p><p>I dag så finns det inte någon väl utarbetat strategi för mappningen på Oversize avdelningen, detta på grund av att andra avdelningar prioriterats på grund av att de säljer mycket mer i dagsläget. Detta har även medfört att den huvudsakliga uppdelning som fanns tidigare på Oversize avdelningen med affärsområden har fått stå åt sidan på grund av tidsbrist och artiklar har placerats in där det finns plats istället för att analysera var de kan placeras bäst.</p><p>Det nya förslaget som vi presenterar för IKEA bygger på att det skall vara enkelt att förstå layouten, plockarna skall veta varför en artikel finns där den finns. Vi har även tagit stor hänsyn till vad som säljs med vad och försökt placera dessa artiklar i närheten av varandra för att på så sätt minska körsträckorna. Vi har även haft i åtanke att det skall vara enkelt att placera om hög och lågfrekventa artiklar samt nyheter inne på lagret då försäljningsvolym påverkas väldigt mycket utav olika kampanjer som IKEA har.</p>
156

CAD-Based Pose Estimation - Algorithm Investigation

Lef, Annette January 2019 (has links)
One fundamental task in robotics is random bin-picking, where it is important to be able to detect an object in a bin and estimate its pose to plan the motion of a robotic arm. For this purpose, this thesis work aimed to investigate and evaluate algorithms for 6D pose estimation when the object was given by a CAD model. The scene was given by a point cloud illustrating a partial 3D view of the bin with multiple instances of the object. Two algorithms were thus implemented and evaluated. The first algorithm was an approach based on Point Pair Features, and the second was Fast Global Registration. For evaluation, four different CAD models were used to create synthetic data with ground truth annotations. It was concluded that the Point Pair Feature approach provided a robust localization of objects and can be used for bin-picking. The algorithm appears to be able to handle different types of objects, however, with small limitations when the object has flat surfaces and weak texture or many similar details. The disadvantage with the algorithm was the execution time. Fast Global Registration, on the other hand, did not provide a robust localization of objects and is thus not a good solution for bin-picking.
157

Automatic parameter tuning in localization algorithms / Automatisk parameterjustering av lokaliseringsalgoritmer

Lundberg, Martin January 2019 (has links)
Many algorithms today require a number of parameters to be set in order to perform well in a given application. The tuning of these parameters is often difficult and tedious to do manually, especially when the number of parameters is large. It is also unlikely that a human can find the best possible solution for difficult problems. To be able to automatically find good sets of parameters could both provide better results and save a lot of time. The prominent methods Bayesian optimization and Covariance Matrix Adaptation Evolution Strategy (CMA-ES) are evaluated for automatic parameter tuning in localization algorithms in this work. Both methods are evaluated using a localization algorithm on different datasets and compared in terms of computational time and the precision and recall of the final solutions. This study shows that it is feasible to automatically tune the parameters of localization algorithms using the evaluated methods. In all experiments performed in this work, Bayesian optimization was shown to make the biggest improvements early in the optimization but CMA-ES always passed it and proceeded to reach the best final solutions after some time. This study also shows that automatic parameter tuning is feasible even when using noisy real-world data collected from 3D cameras.
158

La réalité augmentée au service de l'optimisation des opérations de picking et putting dans les entrepôts / Augmented reality in the service of optimization of the putting and picking operations in warehouses

Gharbi, Safa 18 December 2015 (has links)
Ces travaux de recherche présentés dans cette thèse s’intègrent dans le cadre d’un partenariat entre Generix Group, éditeur de logiciels collaboratifs pour l’écosystème du commerce, et l’École Centrale de Lille portant sur la réalisation d’un système d’aide au déplacement des opérateurs intégrant la Réalité Augmentée (RA) dans le domaine de la supply chain. Dans la gestion des entrepôts, la préparation des commandes représente un processus important. Avoir une gestion optimisée des entrepôts en aidant les opérateurs à travailler dans des meilleures conditions est un enjeu majeur. Le but de cette thèse est de proposer un Système d’Aide à la Décision (SAD) dans les entrepôts pour l’optimisation des processus de picking et putting. L’aspect dynamique et ouvert du problème nous a conduits à adopter une modélisation multi-agent. Le système multi-agent proposé s’appuie sur les méta heuristiques pour gérer l’affectation aux opérateurs des chemins optimisés de préparation de commandes. Le système d’Alliance entre l’Optimisation et les Systèmes Multi-agent (AOSMA) proposé est basé sur une approche de modélisation, optimisation et simulation orientée agent intégrant la technologie des lunettes à RA. En effet, les lunettes connectées permettent d’afficher d’une manière confortable dans le champ de vision de l’opérateur les informations nécessaires afin d’améliorer l’efficacité et le rendement et de réduire les erreurs de picking et putting. Les résultats expérimentaux présentés dans cette thèse justifient l’alliance entre les Systèmes Multi-Agent et l’optimisation tout en intégrant la nouvelle technologie de RA pour assurer le pilotage des parcours de picking et putting / The research presented in this thesis belongs to a partnership between Generix Group, collaborative software vendor for Retail ecosystem, and the Ecole Centrale of Lille which aims to implement a Support System for Travel (SST) distance of pickers integrating Augmented Reality (AR) in the area of the supply chain. In warehouse management, order picking is an important process. Having an optimized warehouse management by helping order pickers to work in better conditions is a major issues. The aim of this thesis is to propose a Decision Support System (DSS) in warehouses to optimize picking and putting processes. The dynamic and open aspect of the problem has led us to adopt a multi-agent modelling approach. The proposed multi-agent system is based on metaheuristics to manage the optimized paths allocation to order pickers. The Alliance between the Optimization and Multi-Agent System (AOMAS) proposed is based on a modeling approach, optimization and agent-oriented simulation integrating Augmented Reality (AR) Smart Glasses. Indeed, the connected glasses can display in the operator's field of vision the necessary information to improve efficiency and effectiveness and reduce errors in picking and putting. The experimental results presented in this thesis, justify the alliance between the multi-agent systems and optimization integrating the new AR technology to ensure the piloting of picking and putting path.
159

ASSESSMENT OF THE INTENSITY OF THE EFFORT OF COFFE PICKERS IN DIFFERENT STAGES OF THE MANUAL PICKING 2006. / ESTUDO DA INTENSIDADE DO ESFORÇO DOS COLHEITADORES NA ATIVIDADE DA COLHEITA MANUAL DO CAFÉ

Cláudio Silva Porto 04 August 2006 (has links)
lt;p align="justify"gt; The present work aimed to assess the intensity of effort of the coffee pickers in different stages of the manual coffee picking, by means of the Heartbeat Frequency, Systolic Arterial Pressure and rate pressure-product, during the three stages of the coffee harvest, in the city of Caratinga-MG. 154 workers were selected and assessed, 77 men and 77 women. The sampling consisted of coffee pickers, with ages ranging between 18 to 57. The design of this work took place in four distinguished moments. Firstly, all the farm workers selected were submitted to a top benchmark test, to assess the maximum *VO2 , maximum rate-pressure product of the workers, through the Balke Protocol (MARINS amp; GIANNICHI, 1998). In a second moment, with the maximum *VO2 results available, the farm workers were compared and classified according to the Aerobic Conditioning Classification Chart for men and women. In a third stage, the heartbeat rate, arterial pressure and rate pressure-product were measured during the stages of: cropping, gathering and fanning. In stage four, the values of heartbeat rate, arterial pressure and rate pressure-product obtained in the three stages of the coffee picking were compared by means of statistical analysis, to determine the statistically significant difference of the values of work load. In the VO2max, classification, there can be noticed that 18 men and 26 women, representing 23.37% and 33.77% , respectively, were qualified as GOOD, for the Balke benchmark test; 41 men and 47 women, 53.25% and 61.03%, classified as REGULAR; 16 men (20.78%) and 3 women (3.90%) classified as BAD; and 2 men (2.60%) and 1 woman (1.30%) classified as VERY BAD. There was a significant increase of the heartbeat rate in all three stages of the harvest as related to heartbeat rate when at rest. It was also assessed that the highest mean values, for both genders, was during the Gathering stage (115.2bpm for the men and 105.3bpm for the women), followed by the Fanning (105.6bpm for the men and 108bpm for the women) and Dropping 91.8bpm for the men and 105.3 for the women), respectively. The mean values found for the heartbeat rates characterize the stages of dropping and fanning of the coffee as reasonably mild, for both the genders, with relative values from 50.28% to 60.81% for the Max. heartbeat rate or 28% to 40% of the VO2max. The values found in the gathering stage, of 63.09% of the max. heartbeat rate for the men, classifies this stage as Reasonably Mild; for the women, the percentage of 69.36 max Heartbeat rate classifies this stage as Rather Hard. The gathering stage recorded the highest mean values of arterial pressure for both the genders (137.40mm Hg for the men and 137.79mm Hg for the women), followed by Fanning (132.68mm Hg foe the men and 134.63mm Hg for the women) and Dropping (129.87 mm Hg for the men and 128.87mm Hg for the women), respectively. In the stages of Dropping and Gathering there was no Significant Difference in the results, regarding genders. The highest mean vales of rate pressure-product found in the three stages of the coffee harvesting were, respectively: 15836.58 for the men, and 16995.06 for the women in the Gathering stage; 14000.43 for the men and 14563.8 for the women in the Fanning; and 11944.3 for the men and 13574.3 for the women in the Dropping stage.lt;/pgt; / lt;p align="justify"gt; O presente trabalho teve como objetivo avaliar a intensidade de esforço dos colheitadores de café, através da Freqüência Cardíaca, Pressão Arterial Sistólica e Duplo Produto, durante as três etapas da colheita do café, no município de Caratinga – MG. Foram selecionados e avaliados 154 trabalhadores, sendo 77 do sexo masculino e 77 do sexo feminino. A amostra foi de colheitadores de café, na faixa etária entre 18 e 57 anos de idade. O processo de construção deste trabalho ocorreu em quatro (04) momentos distintos. No primeiro momento, todos os trabalhadores rurais selecionados foram submetidos a um teste máximo de banco, para estimar o de VO2max. e o duplo produto máx., através do Protocolo de Balke (MARINS amp; GIANNICHI, 1998). No segundo momento, com resultados do teste VO2max., os trabalhadores rurais foram comparados e classificados de acordo com a Tabela de Classificação do Condicionamento Aeróbio de Homens e Mulheres. No terceiro momento, foi avaliada a freqüência cardíaca, a pressão arterial e o duplo produto dos trabalhadores rurais durante as etapas de: derriça, recolhimento e abanação. No quarto momento, os valores de freqüência cardíaca, pressão arterial e duplo produto, obtidos nas etapas da colheita, foram comparados através da análise estatística, para determinar as diferenças significativas dos valores da carga de trabalho. Na classificação do VO2max, pode-se observar que 18 homens e 26 mulheres, que representam 23,37% e 33,77%, respectivamente, foram classificados como BOM, no teste de banco de Balke; 41 homens e 47 mulheres, 53,25% e 61,03%, classificados como REGULAR; 16 homens (20,78%) e 03 mulheres (3,90%), classificados como RUIM; e 02 homens (2,60%) e 01 mulher (1,30%) classificados como MUITO RUIM. Observaram-se maiores valores médios, em ambos os sexos, na etapa de Recolhimento (115,2 bpm para os homens e, 123,2 bpm para as mulheres), seguido pela Abanação (105,6 bpm para os homens e, 108 bpm para as mulheres) e Derriça (91,8 bpm para os homens e, 105,3 bpm para as mulheres), respectivamente. Os valores médios de freqüência cardíaca encontrados caracterizam as etapas de derriça e abanação de café como Razoavelmente Leve, para ambos os sexos, com valores relativos entre 50,28% a 60,81% da FCmáx ou 28% a 40% do VO2 máx. Os valores encontrados na etapa de recolhimento, de 63,09% da FCmáx para os homens, classifica a etapa como Razoavelmente Leve; para as mulheres, o percentual de 69,36% da Fcmáx, classifica a etapa como Bastante Dura. Foram observados maiores valores médios de Pressão Arterial, em ambos os sexos, na etapa de Recolhimento (137,40 mm Hg para os homens e, 137,79 mm Hg para as mulheres), seguido pela Abanação (132,68 mm Hg para os homens e, 134,63 mm Hg para as mulheres) e Derriça (129,87 mm Hg para os homens e, 128,87 mm Hg para as mulheres), respectivamente. Nas etapas de Derriça e Recolhimento não houve diferença significativa nos resultados, em relação ao sexo. Os maiores valores médios de DP encontrados nas três etapas da colheita de café foram, respectivamente: na etapa Recolhimento, 15836,58 para os homens e 16995,06 para as mulheres; na etapa Abanação, 14000,43 para os homens e 14563,8 para as mulheres; na etapa Derriça, 11944,3 para os homens e 13574,3 para as mulheres.lt;/pgt;
160

Improved mass accuracy in MALDI-TOF-MS analysis

Kempka, Martin January 2005 (has links)
<p>Mass spectrometry (MS) is an important tool in analytical chemistry today, particularly in the field of proteomics where identification of proteins is the central activity. The focus in this thesis has been to improve the mass accuracy of MS-analyses in order to improve the possibility for unambiguous identification of proteins.</p><p>In paper I a new peak picking algorithm has been developed for Matrix Assisted Laser Desorption/Ionization - Time of Flight - Mass Spectrometry (MALDI-TOF-MS). The new algorithm is based on the assumption that two sets of ions are formed during the ionisation, and that these two sets have different Gaussian-distributed velocity profiles. The algorithm then deconvolutes the spectral peak into two Gaussian distributions, were the narrower of the two distributions is utilized for peak picking. The two-Gaussian peak picking algorithm proved to be especially useful when dealing with weak, distorted peaks.</p><p>In paper II a novel chip-based target for MALDI analysis is described. The target features pairs of 50x50 μm anchors in close proximity. Each anchor within a pair could be individually addressed with different sample solutions. Each pair could then be irradiated with the MALDI laser, which allowed ionization to take place on separated anchors simultaneously. This made it possible for us to calibrate analytes with calibration standards that where physically separated from the analyte, but ionized simultaneously. The use of new chip-based MALDI target resulted in a 2-fold reduction of relative mass errors. We could also report a significant reduction of ion suppression. The small size of the anchors provided a good platform for efficient utilization of sample. This resulted in a detection limit of ca. 1.5 attomole of angiotensin I at a S/N of 22:1.</p>

Page generated in 0.0641 seconds