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Dissertations / Theses on the topic 'Geometric accuracy of the machine'
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1
Cross, P. M. "An analysis of the geometric instability of steady supported grinding." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384445.
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Fletcher, Simon. "Computer aided system for intelligent implementation of machine tool error reduction methodologies." Thesis, University of Huddersfield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368312.
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Suchomel, Kamil. "Vlivy výrobních technologií na geometrickou a rozměrovou přesnost obrobků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319263.
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The aim of the diploma thesis is to describe influences of selected production technologies on geometrical and dimensional accuracy of workpieces. Specific technologies - turning, milling and grinding and the machines on which these technologies will be implemented - a vertical lathe, a portal milling machine and a center grinder are described in this thesis. Additionally a procedure is created for adding geometric errors to a tri-axial machine tool to describe the entire working area of the machine in terms of errors. Subsequently an analysis of each geometric error is created for each machine and their influence on the resulting workpiece is determined.
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Vala, Michal. "Testování technologie on-the-fly přístrojem LaserTRACER." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319262.
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This diploma thesis describes realization and testing on-the-fly measurement using tracking interferometer. This measurement enables to achieve higher amount of measured points and decrease time of machine tool calibration. Calibration and verification values of machine parameters, as well as time of measurement and other details of this method are compared with results of conventional method called trigger. To evaluate the quality of volumetric compensation created from calibration values, we use verification measurement of circular interpolation.
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Velič, Samuel. "Měření obrobků na obráběcích strojích pomocí obrobkové sondy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417728.
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This diploma thesis deals with the influence of electronic compensation on accuracy of the measurement using the touch probe. The theoretical part concerns touch probes, specifically their classification, principles of working and applications. This part also includes devices used later in the experiment, particularly double ballbar, laser interferometer and LaserTRACER. The Practical part describes an experiment, demonstrating the correlation between the accuracy improvement of the touch probe and the electronic compensation’s level. All measurements were executed in accordance with the norm VDA 5 and were evaluated by the Matlab software. The graphs of reliance tolerance of capability of measurement on the length of the benchmark. At the end of this diploma thesis there are partial conclusions deduced. The deduction is based on generated graphs. The partial conclusions synoptically compare the influence of individual machine´s configurations on the accuracy of the touch probe.
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Pokorný, Zdeněk. "Zpracování dat z měření na obráběcích strojích." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382195.
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The Master’s thesis deals with the precision of machine tools, especially with the three-axis vertical milling machine. It is structurally divided into a theoretical and practical part. While the theoretical part focuses on problems of geometric errors and measuring devices, the practical one is devoted to the machine tool being tested. In this case, the data processing and the proposed statistical analysis are essential, and at the end of the thesis another possible way of developing the data processing is outlined.
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Únar, Jan. "Posouzení geometrické přesnosti obráběcího centra pomocí digitálních inklinometrů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-444307.
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This diploma thesis deals with assessment of geometric accuracy of machining center MCV 754 QUICK. BlueSYSTEM digital inclinometers from WYLER AG, XL-80 laser interferometer from RENISHAW, Ballbar QC20-W from RENISHAW and LaserTRACER self-guiding laser interferometer from ETALON AG were used to measure accuracy. Error of the X straightness in the direction of the Z axis was assessed. The first part of the paper describes the geometric accuracy of the machine, currently available instruments for measuring geometric accuracy and an explanation of straightness. The second part consists of the design of measurements, experiment, evaluation and comparison of results and recommendations for teaching.
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Mišún, Filip. "Návrh automatického cyklu pro posuzování způsobilosti měření obrobkovou sondou na obráběcím centru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443252.
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This diploma thesis describes the procedures of individual electronic compensations for CNC machines used to increase the accuracy of machines. This part is followed by the determining tolerance of the measuring and the influence of individual electronic compensations based on measured data using touch probe and calibrated standards according to VDA 5 norm.
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Lintott, Andrew B. "Geometric modelling and accuracy enhancement of parallel manipulators." Thesis, University of Canterbury. Mechanical Engineering, 2000. http://hdl.handle.net/10092/6159.
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The geometric analysis and accuracy enhancement of parallel topology robots is of theoretical interest as well as having potential for application in industrial settings where parallel robots are used for tasks in which positional accuracy is important. This work presents new techniques for modelling of closed loop mechanisms and applies these experimentally in the calibration of a real parallel topology robot: The Delta robot. This work extends the current literature on serial robot calibration into the realm of parallel robots and presents a systematic approach which does not require the model or solution technique to be adjusted for the particular geometry of the robot under investigation.
The geometric modelling technique is quite general although in its current implementation it is only capable of modelling mechanisms that have rotary joints. Theory is presented for modelling of prismatic joints and the model can be adapted to handle joints of any type. The model analyses the structure as if it were a tree of bodies, each connected by a rotary or prismatic joint. A method of calculating the derivatives of the body frame positions with respect to the geometric parameters is also given. A defining characteristic of parallel topology mechanisms is that the kinematic chains form closed loops. Finding the joint configuration that has all loops properly closed is a non-linear minimisation problem referred to as the closure problem. This is solved using the Levenberg-Marquardt technique.
For analysis of errors in a robot that is already assembled, an experimental calibration procedure is necessary. This procedure compares measured endpoint positions with those predicted by the geometric model and attempts to find a set of parameters that minimises these differences. The calibration procedure that was developed was tested on a number of simulated robots and a working Delta robot, which was designed and built specially for the calibration experiment. The mechanical design of the robot, software and hardware design of the robot controller, and the software implementation of the modelling and calibration procedures are described.
It was found that the modelling, identification, and implementation methods worked successfully on the robots examined, but that the implementation process was too slow for use in a practical controller because of the need to perform multiple direct geometric solutions. The computational effort required for the implementation procedure was considerable, but use of a compiled computer language and optimised code would provide significant improvement.
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Dimitriadis, Alexis. "Assessing the dosimetric and geometric accuracy of stereotactic radiosurgery." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/813888/.
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Stereotactic radiosurgery (SRS) is a non-invasive treatment predominantly used for the management of malignant and benign brain tumours. The treatment can be delivered by various platforms in a single fraction where a high dose of radiation is delivered to the target whilst the surrounding healthy tissue is spared. This requires a high degree of accuracy in terms of the dose level delivered but also in terms of geometric precision. The purpose of this work was to identify the variations of SRS practice in the UK and develop a novel method compatible with all practices, capable of assessing the accuracy of delivery. The motivation behind this e↵ort was to contribute to safety in SRS delivery, provide confidence through a quality assurance audit and form a basis to support standardisation in SRS. A national survey was performed to investigate SRS practices in the UK and to help guide the methodology of this thesis. This resulted to the development of a method for an end-to-end audit of SRS. This was based on an anthropomorphic head phantom with a medium sized target located centrally in the brain, in close proximity to the brainstem. This realistic patient scenario was presented to all 26 radiosurgery centres in the UK who were asked to treat it with SRS. The dose delivered was assessed using two novel commercially available radiation detectors, a plastic scintillator and radiochromic film. These detectors were characterised for measuring the dose delivered in SRS. Another established dosimetry system, alanine, was also used alongside these detectors to assess the accuracy of each delivery. The results allowed the assessment of SRS practices in the UK and the comparison of all centres that participated in the audit. The results were also used to evaluate the performance of the dosimeters used for the purposes of quality assurance measurements and audit.
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Tenn, Stephen Edward. "Characterizing geometric accuracy and precision in image guided gated radiotherapy." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1464128131&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Zhang, Li. "Accuracy enhancement of a hexapod machine tool /." Essen : Vulkan-Verl, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2864795&prov=M&dok_var=1&dok_ext=htm.
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Postlethwaite, Scott R. "Electronic based accuracy enhancement of CNC machine tools." Thesis, University of Huddersfield, 1992. http://eprints.hud.ac.uk/id/eprint/4663/.
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The need for better machine tool accuracy is discussed together with the factors which can affect machine tool accuracy. A study is made of the various techniques adopted for the reduction of errors in machine tools. The concept of error compensation is discussed and the different techniques for error compensation are appraised. A critical appraisal is presented of the work undertaken to date in the field of error compensation. Based on this appraisal a criterion is established for a universally applicable error compensation system. The development of a novel, patented microprocessor based machine tool error compensation system which fulfills this criterion is described. This compensation system, which is based on the precalibrated compensation technique, utilizes a unique geometric compensation algorithm. This algorithm allows the compensation system to compensate for the geometric error components of any machine tool configuration up to three axes. The development of this geometric algorithm is presented. The integration of this compensation system to a large moving column milling machine is described. Measurement tests and cutting tests were performed on this milling machine to establish the effectiveness of the compensation system. The results from these experimental tests are presented, and illustrate the significant improvement in machine tool accuracy achieved through error compensation. This is the first attempt at producing a machine tool error compensation system with universal applicability, both in terms of the machine geometric model, and the method of applying the compensation to the machine tool. The error compensation system developed gives the potential for compensating for thermally induced and load induced position errors, and will enable further work in this area to be commercially exploited.
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Barcenas, Carolina. "Geometric tolerance verification using superquadrics." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/25603.
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Jiang, Yiming. "Automated Generation of CAD Big Data for Geometric Machine Learning." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576329384392725.
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Djordjevic, Milos. "Evaluation of Geometric Accuracy and Image Quality of an On-Board Imager (OBI)." Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6967.
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In this project several tests were performed to evaluate the performance of an On-Board Imager® (OBI) mounted on a clinical linear accelerator. The measurements were divided into three parts; geometric accuracy, image registration and couch shift accuracy, and image quality. A cube phantom containing a radiation opaque marker was used to study the agreement with treatment isocenter for both kV-images and cone-beam CT (CBCT) images. The long term stability was investigated by acquiring frontal and lateral kV images twice a week over a 3 month period. Stability in vertical and longitudinal robotic arm motion as well as the stability of the center-of-rotation was evaluated. Further, the agreement of kV image and CBCT center with MV image center was examined.
A marker seed phantom was used to evaluate and compare the three applications in image registration; 2D/2D, 2D/3D and 3D/3D. Image registration using kV-kV image sets were compared with MV MV and MV-kV image sets. Further, the accuracy in 2D/2D matches with images acquired at non-orthogonal gantry angles was evaluated. The image quality in CBCT images was evaluated using a Catphan® phantom. Hounsfield unit (HU) uniformity and linearity was compared with planning CT. HU accuracy is crucial for dose verification using CBCT data.
The geometric measurements showed good long term stability and accurate position reproducibility after robotic arm motions. A systematic error of about 1 mm in lateral direction of the kV-image center was detected. A small difference between kV and CBCT center was observed and related to a lateral kV detector offset. The vector disagreement between kV- and MV-image centers was 2 mm at some gantry angles. Image registration with the different match applications worked sufficiently. 2D/3D match was seen to correct more accurately than 2D/2D match for large translational and rotational shifts. CBCT images acquired with full-fan mode showed good HU uniformity but half fan images were less uniform. In the soft tissue region the HU agreement with planning CT was reasonable while a larger disagreement was observed at higher densities. This work shows that the OBI is robust and stable in its performance. With regular QC and calibrations the geometric precision of the OBI can be maintained within 1 mm of treatment isocenter.
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Mansouri, Boroujeni Nima. "A High-Order High-Accuracy Geometric Block Interface Treatment for Computational Aeroacoustics Codes." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1463099661.
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Wang, Long Qi. "Translation accuracy comparison between machine translation and context-free machine natural language grammar–based translation." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3950657.
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Ecorchard, Gaël. "Static Accuracy Enhancement of Redundantly Actuated Parallel Kinematic Machine Tools." Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200902064.
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Redundant parallel kinematic machines are parallel mechanisms to which one or more kinematic branch is added in order to improve their mechanical properties, in particular, their stiffness. Redundant parallel kinematic machines have then more actuators than their degree of freedom. New calibration methods are developed in this thesis in order to deal with the particularities related to the actuation redundancy. First, calibration methods using geometrical models are tested. Several measurement systems and control models are compared. A self-calibration is also carried out, where the redundant branches are switched to a passive mode. Thus, they play the role of the measurement system and the mechanism can be calibrated without the help of extra sensors. Geometrical calibration methods, however, do not take into account the internal constraints due to the redundancy. Elastic deformations are neglected although they are shown to have an influence on the positioning accuracy after the calibration. Modeling methods are then developed that take into account the geometry of the mechanism as well as the stiffness of its elements to improve the accuracy of the calibration. With such modeling methods, it is possible to determine the tool-center-point position for redundantly actuated parallel mechanisms from geometrical and stiffness parameters and given positions for all actuators. The modeling methods are first demonstrated on a simple mechanism. They are then tested on a real machine and used in calibration processesMechanismen mit redundanter Parallelkinematik sind Parallelmechanismen, denen eine oder mehrere kinematische Ketten zugefügt werden, um die mechanischen Eigenschaften, insbesondere die Steifigkeit, zu verbessern. Maschinen mit redundanter Parallelkinematik besitzen dann mehr Antriebe als ihr Freiheitsgrad erfordern würde. In dieser Dissertation werden neue Kalibrierungsmethoden entwickelt, um die mit der Antriebsredundanz gebundenen Besonderheiten zu betrachten. Zuerst werden Kalibrierungsmethoden basierend auf geometrischen Modellen getestet. Verschiedene Messmethoden und Messsysteme werden verglichen. Eine Selbstkalibrierung wird durchgeführt. Bei dieser Kalibrierungsmethode werden die redundanten Antriebe freigeschaltet und als Messsystem genutzt. Die Maschine kann dadurch ohne externes Messsystem kalibriert werden. Dennoch betrachten geometrische Kalibrierungsmethode keine internen Verspannungen, die mit der Redundanz verbunden sind. Die elastischen Verformungen werden vernachlässigt, obwohl gezeigt wird, dass sie einen Einfluss auf die Positioniergenauigkeit nach der Kalibrierung haben. Es werden deshalb Modellierungsmethoden entwickelt, die sowohl die Geometrie des Mechanismus als auch die Elementsteifigkeit betrachten, um die Genauigkeit der Kalibrierung zu verbessern. Mit solchen Methoden ist es möglich, die Werkzeugposition redundanter Parallelkinematiken aus den Geometrie- und Steifigkeitsparametern und allen Antriebspositionen zu bestimmen. Die Modellierungsmethoden werden zuerst an einem einfachen Mechanismus angewandt. Sie werden danach an einer realen Maschine getestet und in einem Kalibrierungsprozess genutzt
Les mécanismes à cinématique parallèle redondante sont des mécanismes parallèles auxquels a été ajoutée une branche cinématique, ou plus, dans le but d'améliorer leurs propriétés mécaniques, en particulier, leur rigidité. Les mécanismes à cinématique parallèle redondante possèdent donc plus d'actionneurs que leur degré de liberté. De nouvelles méthodes d'étalonnage sont développées dans cette thèse afin de prendre en compte les spécificités liées à la redondance d'actionnement. Les méthodes d'étalonnage utilisant des modèles géométriques sont d'abord testées. Plusieurs systèmes de mesure et plusieurs modèles de contrôle sont comparés. Un auto-étalonnage est aussi réalisé. Pour cette méthode d'étalonnage, les actionneurs redondants sont mis en mode passif et jouent le rôle de système de mesure. Le mécanisme peut être étalonné sans ajout de codeurs. Cependant, les méthodes d'étalonnage géométriques ne prennent pas en compte les contraintes internes liées à la redondance. Les déformations élastiques sont négligées bien qu'il soit montré qu'elles ont une influence sur la précision de positionnement après étalonnage. Des méthodes de modélisation qui prennent en compte la géométrie du mécanisme ainsi que la rigidité des éléments sont donc développées pour améliorer la précision de l'étalonnage. Avec de telles méthodes, il est possible de déterminer la position de l'outil des mécanismes à redondance d'actionnement à partir de paramètres géométriques et élastiques et de la position de tous les actionneurs. Les méthodes de modélisation sont d'abord appliquées sur un mécanisme simple. Elles sont ensuite testées sur une machine réelle et utilisées dans des processus d'étalonnage
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Dillon, Joshua V. "Stochastic m-estimators: controlling accuracy-cost tradeoffs in machine learning." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42913.
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m-Estimation represents a broad class of estimators, including least-squares and maximum likelihood, and is a widely used tool for statistical inference. Its successful application however, often requires negotiating physical resources for desired levels of accuracy. These limiting factors, which we abstractly refer as costs, may be computational, such as time-limited cluster access for parameter learning, or they may be financial, such as purchasing human-labeled training data under a fixed budget. This thesis explores these accuracy- cost tradeoffs by proposing a family of estimators that maximizes a stochastic variation of the traditional m-estimator.
Such "stochastic m-estimators" (SMEs) are constructed by stitching together different m-estimators, at random. Each such instantiation resolves the accuracy-cost tradeoff differently, and taken together they span a continuous spectrum of accuracy-cost tradeoff resolutions. We prove the consistency of the estimators and provide formulas for their asymptotic variance and statistical robustness. We also assess their cost for two concerns typical to machine learning: computational complexity and labeling expense.
For the sake of concreteness, we discuss experimental results in the context of a variety of discriminative and generative Markov random fields, including Boltzmann machines, conditional random fields, model mixtures, etc. The theoretical and experimental studies demonstrate the effectiveness of the estimators when computational resources are insufficient or when obtaining additional labeled samples is necessary. We also demonstrate that in some cases the stochastic m-estimator is associated with robustness thereby increasing its statistical accuracy and representing a win-win.
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Ecorchard, Gaël. "Static accuracy enhancement of redundantly actuated parallel kinematic machine tools." [Auerbach/Vogtl.] Verl. Wiss. Scripten, 2010. http://d-nb.info/1000285359/04.
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Ecorchard, Gaël. "Static Accuracy Enhancement of Redundantly Actuated Parallel Kinematic Machine Tools." Doctoral thesis, Verlag Wissenschaftliche Scripten, Zwickau, 2008. https://monarch.qucosa.de/id/qucosa%3A19252.
Full textAbstract:
Redundant parallel kinematic machines are parallel mechanisms to which one or more kinematic branch is added in order to improve their mechanical properties, in particular, their stiffness. Redundant parallel kinematic machines have then more actuators than their degree of freedom.
New calibration methods are developed in this thesis in order to deal with the particularities related to the actuation redundancy. First, calibration methods using geometrical models are tested. Several measurement systems and control models are compared. A self-calibration is also carried out, where the redundant branches are switched to a passive mode. Thus, they play the role of the measurement system and the mechanism can be calibrated without the help of extra sensors.
Geometrical calibration methods, however, do not take into account the internal constraints due to the redundancy. Elastic deformations are neglected although they are shown to have an influence on the positioning accuracy after the calibration.
Modeling methods are then developed that take into account the geometry of the mechanism as well as the stiffness of its elements to improve the accuracy of the calibration. With such modeling methods, it is possible to determine the tool-center-point position for redundantly actuated parallel mechanisms from geometrical and stiffness parameters and given positions for all actuators. The modeling methods are first demonstrated on a simple mechanism. They are then tested on a real machine and used in calibration processes.Mechanismen mit redundanter Parallelkinematik sind Parallelmechanismen, denen eine oder mehrere kinematische Ketten zugefügt werden, um die mechanischen Eigenschaften, insbesondere die Steifigkeit, zu verbessern. Maschinen mit redundanter Parallelkinematik besitzen dann mehr Antriebe als ihr Freiheitsgrad erfordern würde. In dieser Dissertation werden neue Kalibrierungsmethoden entwickelt, um die mit der Antriebsredundanz gebundenen Besonderheiten zu betrachten. Zuerst werden Kalibrierungsmethoden basierend auf geometrischen Modellen getestet. Verschiedene Messmethoden und Messsysteme werden verglichen. Eine Selbstkalibrierung wird durchgeführt. Bei dieser Kalibrierungsmethode werden die redundanten Antriebe freigeschaltet und als Messsystem genutzt. Die Maschine kann dadurch ohne externes Messsystem kalibriert werden. Dennoch betrachten geometrische Kalibrierungsmethode keine internen Verspannungen, die mit der Redundanz verbunden sind. Die elastischen Verformungen werden vernachlässigt, obwohl gezeigt wird, dass sie einen Einfluss auf die Positioniergenauigkeit nach der Kalibrierung haben. Es werden deshalb Modellierungsmethoden entwickelt, die sowohl die Geometrie des Mechanismus als auch die Elementsteifigkeit betrachten, um die Genauigkeit der Kalibrierung zu verbessern. Mit solchen Methoden ist es möglich, die Werkzeugposition redundanter Parallelkinematiken aus den Geometrie- und Steifigkeitsparametern und allen Antriebspositionen zu bestimmen. Die Modellierungsmethoden werden zuerst an einem einfachen Mechanismus angewandt. Sie werden danach an einer realen Maschine getestet und in einem Kalibrierungsprozess genutzt
Les mécanismes à cinématique parallèle redondante sont des mécanismes parallèles auxquels a été ajoutée une branche cinématique, ou plus, dans le but d'améliorer leurs propriétés mécaniques, en particulier, leur rigidité. Les mécanismes à cinématique parallèle redondante possèdent donc plus d'actionneurs que leur degré de liberté. De nouvelles méthodes d'étalonnage sont développées dans cette thèse afin de prendre en compte les spécificités liées à la redondance d'actionnement. Les méthodes d'étalonnage utilisant des modèles géométriques sont d'abord testées. Plusieurs systèmes de mesure et plusieurs modèles de contrôle sont comparés. Un auto-étalonnage est aussi réalisé. Pour cette méthode d'étalonnage, les actionneurs redondants sont mis en mode passif et jouent le rôle de système de mesure. Le mécanisme peut être étalonné sans ajout de codeurs. Cependant, les méthodes d'étalonnage géométriques ne prennent pas en compte les contraintes internes liées à la redondance. Les déformations élastiques sont négligées bien qu'il soit montré qu'elles ont une influence sur la précision de positionnement après étalonnage. Des méthodes de modélisation qui prennent en compte la géométrie du mécanisme ainsi que la rigidité des éléments sont donc développées pour améliorer la précision de l'étalonnage. Avec de telles méthodes, il est possible de déterminer la position de l'outil des mécanismes à redondance d'actionnement à partir de paramètres géométriques et élastiques et de la position de tous les actionneurs. Les méthodes de modélisation sont d'abord appliquées sur un mécanisme simple. Elles sont ensuite testées sur une machine réelle et utilisées dans des processus d'étalonnage.
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Vinther, Sven. "Active 3D object recognition using geometric invariants." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362974.
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Lau, Pak Fai. "CNC machining accuracy enhancement by tool path compensation method /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?IEEM%202005%20LAU.
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Jiang, Xiaogeng. "Characterising geometric errors in rotary axes of 5-axis machine tools." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5871/.
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It is critical to ensure that a 5-axis machine tool is operating within its geometric tolerance. However, there are various sources of errors influencing its accuracy; testing them with current methods requires expensive equipment and long machine down time. This motivates the development of a simple and fast way to identify and characterise geometric errors of 5-axis machine tools. A method using a Double Ball Bar (DBB) is proposed to characterise rotary axes Position Independent Geometric Errors (PIGEs), which are caused by imperfections during assembly of machine components. An established method is used to test the same PIGEs, and the results are used to validate the developed method. The Homogeneous Transformation Matrices (HTMs) are used to build up a machine tool model and generate DBB error plots due to different PIGEs based on the given testing scheme. The simulated DBB trace patterns can be used to evaluate individual error impacts for known faults and diagnose machine tool conditions. The main contribution is the development of the fast and simple characterisation of the PIGEs of rotary axes. The results show the effectiveness and improved efficiency of the new methods, which can be considered for 5-axis machine tool maintenance and checking.
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Duong, Nam duong. "Hybrid Machine Learning and Geometric Approaches for Single RGB Camera Relocalization." Thesis, CentraleSupélec, 2019. http://www.theses.fr/2019CSUP0008.
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Au cours des dernières années, la relocalisation de la caméra à base d'images est devenue un enjeu important de la vision par ordinateur appliquée à la réalité augmentée, à la robotique ainsi qu'aux véhicules autonomes. La relocalisation de la caméra fait référence à la problématique de l'estimation de la pose de la caméra incluant à la fois la translation 3D et la rotation 3D. Dans les systèmes de localisation, le composant de relocalisation de la caméra est nécessaire pour récupérer la pose de la caméra après le suivi perdu, plutôt que de redémarrer la localisation à partir de zéro.Cette thèse vise à améliorer les performances de la relocalisation de la caméra en termes de temps d'exécution et de précision ainsi qu'à relever les défis de la relocalisation des caméras dans des environnements dynamiques.Nous présentons l'estimation de la pose de la caméra basée sur la combinaison de la régression de pose multi-patch pour surmonter l'incertitude des méthodes d'apprentissage profond de bout en bout. Afin d'équilibrer la précision et le temps de calcul de la relocalisation de la caméra à partir d'une seule image RVB, nous proposons une méthode hybride à caractéristiques éparses. Une meilleure prédiction dans la partie d’apprentissage automatique de nos méthodes conduit à une inférence rapide de la pose de la caméra dans la partie géométrique. Pour relever le défi des environnements dynamiques, nous proposons une forêt de régression adaptative qui s'adapte en temps réel au modèle prédictif. Il évolue en partie au fil du temps sans qu'il soit nécessaire de ré-entrainer le modèle entier à partir de zéro. En appliquant cet algorithme à notre relocalisation de la caméra en temps réel et précise, nous pouvons faire face à des environnements dynamiques, en particulier des objets en mouvement. Les expériences prouvent l'efficacité des méthodes que nous proposons. Notre méthode permet d'obtenir des résultats aussi précis que les meilleures méthodes d’état de l’art. De plus, nous obtenons également une grande précision même sur des scènes dynamiquesIn the last few years, image-based camera relocalization becomes an important issue of computer vision applied to augmented reality, robotics as well as autonomous vehicles. Camera relocalization refers to the problematic of the camera pose estimation including both 3D translation and 3D rotation. In localization systems, camera relocalization component is necessary to retrieve camera pose after tracking lost, rather than restarting the localization from scratch.This thesis aims at improving the performance of camera relocalization in terms of both runtime and accuracy as well as handling challenges of camera relocalization in dynamic environments. We present camera pose estimation based on combining multi-patch pose regression to overcome the uncertainty of end-to-end deep learning methods. To balance between accuracy and computational time of camera relocalization from a single RGB image, we propose a sparse feature hybrid methods. A better prediction in the machine learning part of our methods leads to a rapid inference of camera pose in the geometric part. To tackle the challenge of dynamic environments, we propose an adaptive regression forest algorithm that adapts itself in real time to predictive model. It evolves by part over time without requirement of re-training the whole model from scratch. When applying this algorithm to our real-time and accurate camera relocalization, we can cope with dynamic environments, especially moving objects. The experiments proves the efficiency of our proposed methods. Our method achieves results as accurate as the best state-of-the-art methods on the rigid scenes dataset. Moreover, we also obtain high accuracy even on the dynamic scenes dataset
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Bhatia, Shaleen. "Effect of Machine Positional Errors on Geometric Tolerances in Additive Manufacturing." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820498.
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Ramanaiah, Harikishan Veluru. "Relation between Process Capability Indices and Geometric Errors of Machine Tool." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215977.
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Myers, Alan. "The effect of concrete foundations and machine thermal conditions on the accuracy of large machine tools." Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34454/.
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This thesis comprises of eighteen publications which describe research work which has been carried out into two aspects regarding the accuracy of large machine tools. The first six papers discuss the concrete foundations on which the machines are supported and the remaining twelve papers describe the consequences of thermal effects on machines. The publications are all ones of joint authorship, with the candidate being one of the named authors. Manufacturing industry and the precision requirements of large machine tools: The thesis reviews the range of errors and their causes that effect large machine tools and then specifically addresses what are considered to be two of the most significant contributors to these inaccuracies, namely those caused by the concrete foundations which support the machines and those caused by thermal effects. Both can cause problems that can be very difficult and extremely expensive to resolve. After a concrete foundation has been cast, if it is found to be inadequate it cannot, of course, be easily modified and thermal effects such as environmental temperature changes for instance can require the use of factory air conditioning systems which are expensive to install, operate and maintain. The publications included in the thesis show a systematic contribution to significantly improving the accuracy of large machine tools with respect to the two mentioned subjects. Modern components: Components used in modern equipment such as cars, trains, aircraft, robots, household appliances etc. require good functionality, reliability, long life, light weight etc. A significant contributor to these requirements is the high degree of precision [1] that these components are manufactured to in terms of their dimensions, form and surface finish. Production of virtually all of these components is achieved either directly or indirectly by use of machine tools. Therefore the machine tools need to perform extremely accurately, even more so than the components they produce since other factors such as fixtures, tooling etc. cause additional inaccuracies. Machine tool Accuracy: To achieve high accuracy performance, the machines need to move in a precise manner in terms of their straightness of movement, positional accuracy, rotational orientation and the relationship of one axis to another etc. It is also important that the accuracy is repeatable in order to guarantee the level of performance at all times. Large machine tools: Large machine tools can weigh hundreds of tonnes, have traverses of eighty metres length or more and are used for machining a vast variety of components such as nuclear reactor vessels, marine diesel engines, valve bodies, rolls for steel mills, aircraft wing components such as skins, ribs, stringers and spars and large undercarriage components. Foundations: Because the machines being considered are large and heavy their influence on the concrete foundations that support them is considerable and as a machine moves through its traverses the position of the center of gravity changes. The consequence is the foundation changes both shape (bends) and vertical position (sinks and rises). The six foundation papers describe the research and developement of techniques that can be used to ensure the distortions and deflections values are acceptable such that a machine will be capable of performing to its intended functionality. Also described is the research, development and performance testing of a taut wire and optical senors instrumentation for efficiently measuring the change of shape of the foundation. Thermal Effects: The machines and the workpieces they produce, can be constructed from a variety of materials such as steel, aluminium, carbon fibre, concrete etc all of which have coefficients of linear expansion that when subjected to modest temperature changes can result in contractions and expansions that can cause workpiece to cutting tool relative positions to vary more than the workpiece dimensional tolerances. The twelve thermal publications describe the research and developement that has been carried out into machine tool thermal characteristics and the positional compensation techniques that have been developed to minimise the resulting positional errors. Using artifical intelligence methods this has been achieved so successfully that the errors can be reduced by 95%.
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Tan, Ning. "Calibration of micro and nanorobotic systems : Contribution of influential parameters to the geometric accuracy." Phd thesis, Université de Franche-Comté, 2013. http://tel.archives-ouvertes.fr/tel-01025313.
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Une des conditions fondamentales de la performance des système repose sur leur capacité à généré des déplacement avec précision de positionnement élevée. Cependant, à l'échelle micrométrique, de nombreux paramètres agissent et réduisent cette précision. A cette échelle, il est également particulièrement complexe de mesurer la précision de positionnement d'un système micro ou nanorobotique et donc d'identifier les différentes sources d'imprécision. L'étalonnage géométrique des systèmes micro et nanorobotiques prenant en compte ces différents sources est rarement étudié. Pour ces raisons, l'originalité et les contribution de cette thèse portent sur deux aspects principaux (i) la caractérisation des perperformances des systèmes micro et nanorobotiques et l'analyse des paramètres affectant leur précision de positionnement (ii) l'amélioration des performances de ces robots fondés sur différents types de modèles robotiques.
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Su, Qinliang, and 蘇勤亮. "On convergence and accuracy of Gaussian belief propagation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208046.
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Gkaliamoutsas, Pantelis. "Modeling fused filament fabrication machine height accuracy through layer thickness variation." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113766.
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Thesis: M. Eng. in Advanced Manufacturing and Design, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 85-88).
This thesis addresses the modeling and prediction of total height error of a 3D printed part using a layer-by-layer approach. Layer to layer thickness error is modeled across the build height of Polyactic acid (PLA) and Acrylonitrile butadiene styrene (ABS) parts. A height error compensation model is then formulated and applied at a G-code level to drive the machine to print accurate parts. Preliminary experimentation was done on New Valance Robotics' two fused deposition modeling machine versions, the NVPro and the NVPro High-temp. Results suggested that the layer thickness approach was a viable technique for predicting total part height error. The compensation model for PLA parts was also tested and the compensated parts were significantly closer to the expected part height than the uncompensated prints. However, further experimentation will need to be carried out to solidify a model for ABS parts. Recommendations for future work, measurement method improvement, and model applications are also discussed.
by Pantelis Gkaliamoutsas.
M. Eng. in Advanced Manufacturing and Design
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Yu, Alexander. "Geometric method for the accuracy analysis of a class of 3-DOF planar parallel robots." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66719.
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Planar parallel robot accuracy indices are evaluated because such robots are widely used in industrial applications where quick, precise positioning and alignment are essential. With their increasing use comes a need to develop a methodology to compare different parallel robot designs. However no simple method exists to adequately compare the accuracy of parallel robots. Certain indices have been used in the past such as dexterity, manipulability and global conditioning index, but they have inherent problems when applied to both translational and rotational motion of a parallel robot. In direct response to the need for more methods in evaluating the accuracy of parallel robots, this thesis presents a simple geometric method for computing the exact local maximum position error and maximum orientation error, given the actuator displacement inaccuracies. This new method gives a clear, quantitative way to evaluate planar parallel robots. This method is shown to work well when applied to a class of three-degree-of-freedom planar fully-parallel robots, whose legs each have each one passive revolute joint and two prismatic joints.Les indices de précision d'un robot planaire parallèle sont analysés dans la présente thèse en raison de leur large utilisation dans des applications industrielles où la précision du positionnement et de l'alignement est essentielle. Leur utilisation croissante s'accompagne du besoin de développer une méthode pour évaluer différentes conceptions de robots parallèles. Cependant, il n'existe pas de méthode simple d'évaluation comparative de la précision des robots parallèles. Par le passé, on utilisait certains indices tels que la dextérité, la capacité de manipulation et l'évaluation globale, mais ces derniers présentaient des problèmes inhérents lorsque appliqués à la fois au mouvement de translation et de rotation d'un robot parallèle. En réponse directe au besoin de disposer de plus d'outils d'évaluation de la précision des robots parallèles, cette thèse présente une méthode géométrique simple pour calculer les inexactitudes maximales de positionnement et d'orientation, en tenant compte des inexactitudes de déplacement de l'actuateur.Il est prouvé que l'utilisation de cette nouvelle méthode est claire et quantitative pour l'évaluation de robots planaires parallèles. Elle donne de bons résultats quand on l'applique à une catégorie de robots planaires à trois degrés de liberté, dont les pattes ont chacune une a rticulation rotoïde passive et deux articulations prismatiques.
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Laspas, Theodoros. "Modeling and measurement of geometric error of machine tools : Methodology and implementation." Thesis, KTH, Industriell produktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157641.
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One of the main performance criteria for a machine tool is its ability to manufacture dimensionally and geometrically accurate parts. In this context evaluation of the geometric and kinematic accuracy of machine tools is important for achieving a high accuracy of machine parts. Moreover, the potential of predicting the accuracy of the machine tool outcome would benefit by reducing the non-value adding operations of machined parts measurement. The aim of this thesis is to develop a methodology for modeling geometric errors of machine tools in order to evaluate the geometric and kinematic accuracy and estimate the machined part accuracy by predicting the error motion of the machine tool for a given toolpath. The thesis consists of the description of the methodology that includes and explains aspects necessary for the development of the machine geometric error model. Additionally, a laser interferometer measurement process of the geometric errors and the various parameters necessary for the model development is presented. A three axis machine tool is utilized in order to investigate and analyze the model and to measure the geometric errors. An analysis is made for evaluating the accuracy of the machine tool. Finally, a computational implementation of the model is made and two simple toolpaths are generated in order to demonstrate the potential of the model in predicting the geometric errors of the machine.En av de viktigaste prestationskriterierna för en verktygsmaskin är dess förmåga att tillverka dimensionellt och geometriskt korrekta delarna. I detta sammanhang är utvärderingen av den geometriska och kinematiska noggrannhet av maskinverktyg är viktigt för att uppnå en hög noggrannhet av maskindelar. Dessutom skulle möjligheten att förutsäga noggrannheten av verktygsmaskiner resultatet gynnas genom att minska icke värdeskapande verksamhet bearbetade delar mätning. Syftet med denna avhandling är att utveckla en metod för att modellera geometriska fel av verktygsmaskiner för att utvärdera den geometriska och kinematiska noggrannhet och uppskatta den bearbetade komponentens noggrannheten genom att förutsäga felet verktygmaskinens rörelse för en given verktygsbana. Avhandlingen beskriver en metod som omfattar och förklarar de aspekter som är nödvändiga för utveckling av en geometrisk felmodell för verktygsmaskiner. Dessutom presenteras en mätprocess som, använder laserinterferometer, för identifiering av de geometriska fel och parametrar som är nödvändiga för att utveckla modellen. En tre-axlig verktygsmaskin används för att undersöka och analysera modellen samt för att mäta dess geometriska fel. En analys görs för att utvärdera verktygsmaskinens noggranhet. Slutligen är denna felmodell beräknad och två enkla verktygsbanor används i syfte att visa modellens potential att förutsäga geometriska fel i maskinen.
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Bhatnagar, Kovid. "Liver Segmentation by Geometric and Texture features using Support Vector Machine (LiGTS)." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452224451.
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Kovacs, Tim. "Strength or accuracy : credit assignment in learning classifier systems /." London [u.a.] : Springer, 2004. http://www.loc.gov/catdir/enhancements/fy0813/2003061884-d.html.
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Theissen, Nikolas Alexander. "Physics-based modelling and measurement of advanced manufacturing machinery’s positioning accuracy : Machine tools, industrial manipulators and their positioning accuracy." Licentiate thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263700.
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Advanced manufacturing machinery is a corner stone of essential industries of technologicallydeveloped societies. Their accuracy permits the production of complexproducts according to tight geometric dimensions and tolerances for high efficiency,interchangeability and sustainability. The accuracy of advanced manufacturingmachinery can be quantified by the performance measure of positioning accuracy.Positioning accuracy measures the closeness between a commanded and an attainedposition on a machine tool or industrial manipulator, and it is ruled by lawsof physics in classical mechanics and thermodynamics. These laws can be applied tomodel how much the machinery deflects due to gravity, expands due to a change intemperature and how much and how long it vibrates due to process forces; hence,one can quantify how much the accuracy decreases. Thus, to produce machinerywith ever higher accuracy and precision one can design machines which deflect,expand and vibrate less or one can understand and model the actual behaviour ofthe machinery to compensate for it.This licentiate thesis uses physics-based modelling to quantify the positioningaccuracy of machine tools and industrial robots. The work investigates the potentialincrease in positioning accuracy because of the simultaneous modelling of the kinematics,static deflections, vibrations and thermo-elasticity as a lumped-parametermodel of the machinery. Consequently the models can be used to quantify thechange of the accuracy throughout the workspace.The lumped parameter models presented in this work require empirical modelcalibration and validation. The success of both, calibration and validation, dependson the availability of the right measurement instruments, as these need to be ableto capture the actual positioning accuracy of machinery. This thesis focuses on theimportance of measurement instruments in industry and metrology and creates acatalogue of requirements and trends to identify the features of the measurementinstruments required for the factories of the future. These novel measurement instrumentsshall be able to improve model calibration and validation for an improvedoverall equipment effectiveness, improved product quality, reduced costs, improvedsafety and sustainability as a result of physics-based modelling and measurementof advanced manufacturing machinery.
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Nadella, Sunita. "Effect of machine vision based traffic data collection accuracy on traffic noise." Ohio : Ohio University, 2002. http://www.ohiolink.edu/etd/view.cgi?ohiou1174681979.
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Berry, Jethro. "Machine design to improve accuracy and repeatability in on-site circular milling." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/10122.
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Includes bibliographical references (leaves 86-87).This project's objective focuses on machine design to primarily improve accuracy and repeatability in on-site circular machining. On-site circular machining is used in the finishing and repairing of flanges most commonly used for mating with slewing bearings. The expected outcomes of the manufacturing processes are always increasing, therefore requiring higher levels of accuracy. The milling must be performed under a wide range of environmental conditions. The environmental conditions may prohibit the use of high accuracy measurement systems. The factors that effect the achievable accuracy and repeatability of the circular milling process are assessed in this project. From these findings new systems are designed in order to achieve higher degrees of performance in the circular milling process over a larger range of operating conditions.
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Ong, T. S. "Development of process planning methodology for end milled features specified with geometric toler." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396216.
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Uddin, Mohammad Sharif. "Tool Path Modification Approaches to Enhance Machining Geometric Accuracy in 3-Axis and 5-Axis Machining." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/49142.
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学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2861号 ; 請求記号: 新制/工/1420 ; 整理番号: 25546Introduction Precision manufacture of components has become a necessity in the present day manufacturing sectors. The ever-increasing demands of humankind have forced researchers to come up with more improved innovations in technology; achieving higher levels of integration in microprocessors, and creating more versatile and precision multitasking systems being just a few of the major drivers in this area. All these, however, have one rudimentary requirement, namely, the need to use very high precision components. Hence, it can be very safely concluded that the success of each of these industries hinges on the ability to produce such components. Recently, as the tremendous demands for mechanical parts with high geometric and dimensional accuracy increase, an exigency to produce those parts with such accuracy is greatly comprehended by today’s manufacturing industries. To this end, CNC machine tools are the most important means of production for the manufacturing industries. CNC machine tools have been widely applied to a range of applications, for example, in the aerospace industries. With the recent advancement of the machine tools manufacturing technologies including high speed feed drives and high speed spindles, high speed end milling on the CNC machine tools has become constantly popular, and is being performed to manufacture the components with the required contour geometry and dimensional accuracy. However, the geometric accuracy of the machined surface is greatly affected by the numerous errors sources ranging from errors existing in the machine tool system itself to the errors due to the cutting process. Figure 1-1 shows the general error sources that influence the machining geometric accuracy [Kakino et al., 1993]. Broadly, machining geometric errors are caused by two major error sources: motion errors of the machine tool system and errors due to the machining process. The key factors among error sources in the machine tool system that cause deviation of tool tip position relative to workpiece, and hence machining geometric errors are positioning errors and volumetric errors. Here, positioning errors are defined as the linear errors of the positioning mechanism, whose directions are in parallel with the direction of axis movement required for desired positioning. On the other hand, volumetric errors are here defined as error components whose directions are perpendicular to the direction of axis movement.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13390号
工博第2861号
新制||工||1420(附属図書館)
25546
UT51-2007-Q791
京都大学大学院工学研究科精密工学専攻
(主査)教授 松原 厚, 教授 吉村 允孝, 教授 松久 寛
学位規則第4条第1項該当
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Henrico, Ivan. "Geometric accuracy improvement of VHR satellite imagery during orthorectification with the use of ground control points." Thesis, University of Pretoria, 2016. http://hdl.handle.net/2263/60812.
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Conducting single frame orthorectification on satellite images to create an ortho-image requires four basic components, namely an image, a geometric sensor model, elevation data (for example a digital elevation model (DEM)) and ground control points (GCPs). For this study, orthorectification was executed numerous times (in three stages) and each time components were altered to test the geometric accuracy of the resulting ortho-image. Most notably, the distribution and number of ground control points, the quality of the elevation source and the geometric sensor model or lack thereof were altered. Results were analysed through triangulating and comparing the geolocation accuracy of the ortho-images. The application of these different methods to perform orthorectification encompass the aim of this paper, which was to investigate and compare the positional accuracies of ortho-images under various orthorectification scenarios and provide improved geometric accuracies of VHR satellite imagery when diverse ground control and elevation data sources are available. By investigating the influence that the distribution and number of GCPs and the quality of DEMs have on the positional accuracy of an ortho-image, it became clear that a reasonable increase in the number of uniformly distributed GCPs combined with progressively accurate DEMs will ultimately improve the quality of the orthorectified product. The results also showed that when more GCPs were applied, the smaller the difference in accuracy was between the different DEMs utilised. It was interesting to note that when it is suitable to manually collect well-distributed GCPs using a GPS handheld device over the study area then a very accurate result can be expected. Nonetheless, it is also important to note that if it is not possible/practical to achieve the latter, satellite based GCP collection do provide a very good alternative. It was also determined that utilising GCPs which were extracted from vector road layers to only cover specific areas in the image scene produced less favourable results. Several contributions towards improved orthorectification procedures were made in this study. These include the development of an automatic GCP extraction script (A-GCP-ES), written in the Python scripting language with the purpose to ease the process of manually placing GCPs on an input image when repeatedly performing orthorectification.Thesis (PhD)--University of Pretoria, 2016.
Geography, Geoinformatics and Meteorology
PhD
Unrestricted
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Allen, James. "A general approach to CNC machine tool thermal error reduction." Thesis, University of Huddersfield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285842.
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Kozáček, Peter. "Softwarové rozhraní pro uživatelské aplikace laser trackeru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231747.
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For assembly of product machine is necessary to evaluate a geometric accuracy of individual functional parts of the machine. This process is very demanding and time consuming. One of the reasons of mentioned problems is the lack of software (adaptation) for measuring of the accuracy of geometrical precision. This theses (diploma work) focuses at facilitating the development and creation of own application based on customer requirements and for measuring geometric accuracy with the Laser Tracker AT901 from Leica company. The aim is to create a basic application suitable for measurement of geometric accuracy, which would speed up this process, would be user-friendly, simple and open for further expansion.
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Lee, Jinho. "Design of controllers for improving contour accuracy in a high-speed milling machine." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010702.
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Mohan, Sumod K. "Accuracy and multi-core performance of machine learning algorithms for handwritten character recognition." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1252424826/.
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Tawha, Tafadzwa Primrose Rudo. "Assessing the accuracy of the zygoma for estimating ancestry using geometric morphometrics in a South African sample." Master's thesis, Faculty of Health Sciences, 2019. http://hdl.handle.net/11427/31282.
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The large number of unidentified, decomposed and skeletonised remains found in South Africa (SA) necessitates relevant and reliable methods to assist in victim identification. Ancestry estimation from unknown skeletal remains is essential when reconstructing a demographic profile of a missing person. In the SA population, estimating ancestry is problematic as standards developed internationally rarely apply to the local, biologically heterogenous population. Craniofacial morphology is known to be ancestrally distinct and studies are yet to explore shape and size variation in the zygomatic bone of the SA population. The aim of this study was to assess ancestral variation in zygomatic shape and size in a SA population using three-dimensional geometric morphometric analyses. A sample of 158 individuals were analysed from Bantu-speaking (BA), European (EA) and Mixed Ancestral (MA) South African groups. Males were larger in size than females, but no size differences were observed between ancestral groups. Significant shape differences were observed between ancestral groups, while none were observed between males and females. BA and MA individuals had narrower, shorter and more anteriorly projecting zygomas than EA individuals. The zygoma was shown to accurately distinguish EA (84%) from BA (81%), and MA (80%) from EA (68%) individuals, but unreliably distinguished BA (60%) from MA (66%) individuals. This is likely correlated to the historical peopling of SA and historical forced racial classification. Age-related changes and antemortem tooth loss did not confound the ancestral variation in size, despite minor changes in zygomatic shape being associated with these two factors. These confounders did not impact ancestry estimation accuracies, further suggesting a minor impact on overall zygomatic shape. Furthermore, the patterning of ancestral variation in the zygoma revealed the need for further research to distinguish between the biologically heterogenous ancestral groups in SA.
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Farley, Mark Harrison. "Predicting machining accuracy and duration of an NC mill by computer simulation." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/16499.
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Vogel, Elisa, and Shannon Bowen. "An evaluation of the accuracy of community-based automated blood pressure machines." The University of Arizona, 2010. http://hdl.handle.net/10150/623756.
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Class of 2010 AbstractOBJECTIVES: The purpose of this study was to evaluate the accuracy of automated blood pressure machines located within community-based pharmacies. METHODS: A descriptive, prospective study was performed comparing blood pressure readings obtained from community-based automated blood pressure machines to readings from a mercury manometer for 2 different arm sizes. Mercury manometer readings were obtained using the standardized technique and a standard cuff recommended by the American Heart Association RESULTS: For the subject with the small arm size, the automated blood pressure machines reported systolic pressure readings that were, on average, 16.1 mmHg higher than those obtained manually by the researcher. The mean systolic and pressure readings for the subject with the medium arm size were not significantly different between the automated machine and manual manometer readings, and the diastolic pressure readings were modestly different. CONCLUSIONS: We found that automated blood pressure machines located within a sample of representative community pharmacies were neither accurate nor reliable. The accuracy of the readings are especially inaccurate for subjects with a smaller than average arm size.
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Huang, Kuang Peng, and 黃光鵬. "Geometric Parameter Identification and Accuracy Analysis of a New Machine Tool." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83280424565732728354.
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碩士國立臺灣科技大學
機械工程系
88
This work investigates the geometric parameter identification and the accuracy analysis of a new parallel-type machine tool. The research first establishes a mathematical model and a calibration method for this machine. The model includes forward kinematics, inverse kinematics and parameter identification. For calibration, it is recommended that the positions of the machine tool be measured through three separate steps. Since the prototype machine has not been ready for operation, parameter identification procedure is examined by computer simulation. Error analysis is the next topic to be addressed in this work. By means of statistic methods, the orientation errors and position errors of the tool in the workspace are estimated from the geometric variations of the machine frame and position errors of the linear motors. Finally, Taguchi method is applied to evaluate possible modifications of the prototype machine. The length of links, the width between parallel sliders and the size of the tool frame are defined as three control factors while the uncertainties associated with geometric parameters are treated as noise factors. The results are obtained from the analysis of variances based on sampling data.