Development Of Moiré Fringe Recognition System Using Artificial Neural Network For 2-D Displacement Measurement

Pelbagai kaedah telah dicadangkan untuk mendapatkan maklumat anjakan dalam analisis corak moiré. Kaedah-kaedah ini boleh dikategorikan kepada analisis manual oleh inspektor manusia, kaedah komputasi dan kaadah analisis berasaskan imej. Analisa manual terdedah kepada ralat manusia kerana ia bergantung kepada keputusan manusia dalam analisa corak moiré. Penggunaan kaedah pengiraan dalam analisa corak moiré adalah terhad kepada corak moiré yang dihasil daripada parutan berfrekuensi tinggi yang sinusoid. Dalam kaedah berasaskan analisis imej, Algoritma yang kompleks menyebabkan butir-butir halus dalam corak moiré terhilang dalam operasi pra-proses imej. Situasi ini menyebabkan ketidakpastian dalam analisa corak moiré. Untuk mengatasi kelemahan yang disebut di atas, kaedah rangkaian saraf buatan (ANN) dicadangkan untuk sistem pengenalan corak moiré dalam pengukuran anjakan 2-D. Sistem pengenalan corak moiré terdiri daripada dua ANN dengan dua tugas yang berbeza iaitu (i) penentuan pusat pinggiran moiré dan (ii) penentuan kesipian berdasarkan corak moiré. Kaedah ANN dibandingkan dengan kaedah analisa grafik (GAM), sejenis kaedah analisa berasaskan imej, dari segi ketepatan dan masa pengiraan untuk pengukuran anjakan 2-D pola moiré. The experiments prove that ANN approach has a higher accuracy to GAM with mean errors with 95% confidence of 0.068 ± 0.013 mm for eccentric magnitudes and 1.85 ± 0.465º. An improvement of 66.18% in the computation time is also reported in the comparison. A straightforward solution for the moire fringe recognition system of circular grating moire pattern is achieved using ANN approach. _______________________________________________________________________________________________________ Various methods have been proposed in the analysis of moiré pattern. These methods can be categorized into manual inspection by human inspector, computational methods and image analysis based methods. Manual interpretation of moiré patterns is prone to human errors as it is highly dependent on the decision of the human inspector. The computational methods are lack of flexibility as they are limited to high frequency gratings which are sinusoidal in the transmittance of grating. As for the image analysis based methods, complex algorithms can unintentionally remove the fine details in the moiré patterns and cause uncertainty in the analysis. To overcome the above mentioned drawbacks, an artificial neural network (ANN) approach is proposed for a moiré fringe recognition system in 2-D displacement measurement. The moiré fringe recognition system consists of two ANNs with two different tasks : (i) the determination of moiré fringe centers of the circular grating moiré patterns and (ii) the determination of eccentricity magnitudes and eccentricity directions of the circular grating moiré patterns. The ANN approach is compared to graphical analysis method (GAM), an image analysis based method, in terms of accuracy and computational time for 2-D displacement measurement of circular grating moiré patterns. The experiments prove that ANN approach has a higher accuracy to GAM with mean errors with 95% confidence of 0.068 ± 0.013 mm for eccentric magnitudes and 1.85 ± 0.465º. An improvement of 66.18% in the computation time is also reported in the comparison. A straightforward solution for the moire fringe recognition system of circular grating moire pattern is achieved using ANN approach

Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry

Quick mass production of homogeneous thin film material is required in paper, plastic, fabric, and thin film industries. Due to the high feed rates and small thicknesses, machine vision and other nondestructive evaluation techniques are used to ensure consistent, defect-free material by continuously assessing post-production quality. One of the fastest growing inspection areas is for 0.5-500 micrometer thick thin films, which are used for semiconductor wafers, amorphous photovoltaics, optical films, plastics, and organic and inorganic membranes. As a demonstration application, a prototype roll-feed imaging system has been designed to inspect high-temperature polymer electrolyte membrane (PEM), used for fuel cells, after being die cast onto a moving transparent substrate. The inspection system continuously detects thin film defects and classifies them with a neural network into categories of holes, bubbles, thinning, and gels, with a 1.2% false alarm rate, 7.1% escape rate, and classification accuracy of 96.1%. In slot die casting processes, defect types are indicative of a misbalance in the mass flow rate and web speed; so, based on the classified defects, the inspection system informs the operator of corrective adjustments to these manufacturing parameters. Thickness uniformity is also critical to membrane functionality, so a real-time, full-field transmission densitometer has been created to measure the bi-directional thickness profile of the semi-transparent PEM between 25-400 micrometers. The local thickness of the 75 mm x 100 mm imaged area is determined by converting the optical density of the sample to thickness with the Beer-Lambert law. The PEM extinction coefficient is determined to be 1.4 D/mm and the average thickness error is found to be 4.7%. Finally, the defect inspection and thickness profilometry systems are compiled into a specially-designed graphical user interface for intuitive real-time operation and visualization.M.S.Committee Chair: Tequila Harris; Committee Member: Levent Degertekin; Committee Member: Wayne Dale

Using geometric algebra to create differentiable models for optimizing camera-based optical metrology systems

In the design process of camera-based optical metrology systems numerous intricate and seemingly distinct optimization tasks emerge.A frequently occurring but crucial task in design or calibration is to optimize the spatial degrees of freedom of system components. Of course, modelling the poses of rigid bodies is long solved using rotation matrices and translation vectors, but when it comes to optimizing, this choice of model gets quite tedious to handle. Useful concepts such as homogeneous coordinates or (dual) quaternions have been introduced to overcome this, which however – lacking a unified framework – can quickly become difficult to maintain. As an alternative, in this contribution it is shown how the unifying methods of geometric algebra can be used as an advantage for gradient-based optimization of camera-based optical metrology and imaging systems – and how this can be done in a generalized way for seemingly different objectives with respect to system design and calibration

Topics in Adaptive Optics

Advances in adaptive optics technology and applications move forward at a rapid pace. The basic idea of wavefront compensation in real-time has been around since the mid 1970s. The first widely used application of adaptive optics was for compensating atmospheric turbulence effects in astronomical imaging and laser beam propagation. While some topics have been researched and reported for years, even decades, new applications and advances in the supporting technologies occur almost daily. This book brings together 11 original chapters related to adaptive optics, written by an international group of invited authors. Topics include atmospheric turbulence characterization, astronomy with large telescopes, image post-processing, high power laser distortion compensation, adaptive optics and the human eye, wavefront sensors, and deformable mirrors

In-situ Grain Scale Strain Measurements using Digital Image Correlation

Materials used in engineering structures fatigue and ultimately fail due to the various applied loads they are subject to, a process which compromises structural performance and potentially poses threats to society. Commonly employed theoretical models capable of describing and predicting deformation and failure are typically validated by relevant experimental results obtained from laboratory testing. However, such models are also often based on simplifying assumptions including for example homogeneous composition and isotropic behavior, since available experimental information relates primarily to bulk behavior.Metals are crystalline in nature and their failure depends on several parameters that span a wide range of time and length scales. Therefore, significant efforts have been made over the past decades to investigate the mechanical behavior of polycrystalline metals by formulating important microstructure-properties relations. In this context, this thesis presents a framework to obtain reliable, non-destructive, non-contact, full field measurements of deformation and strain at the grain-scale of polycrystalline materials to assist the understanding of materials phenomena and contribute in the development of realistic mechanics models. To this aim, the method of Digital Image Correlation is used, adapted and expanded.Digital Image Correlation relies on images of the surface of tested specimens, components or structures and the identification of surface contrast patterns which are tracked as a function of deformation and are subsequently used to define displacements and strains. To quantify stains at the grain-scale, three different approaches based on Digital Image Correlation are described. The first involves the use of a commercial system adapted to make grain-scale measurements at the meso-scale (~4mm). A magnesium AZ31alloy was observed for this purpose and full field strain maps are reported. The second employs the same commercial system augmented with a long distance optical microscope to in-situ quantify strains at the tip of a propagating crack in a Compact Tension specimen of an Al2024 aluminum alloy subjected to Mode I loading and using a field of view of ~870 x 730 μm. Finally, the third approach uses an image series acquired from loading a stainless steel sample inside a scanning electron microscope equipped with a micro-tensile stage. Such information was post processed ex-situ and strains were obtained. The advantages and limitations of the proposed approaches are critically evaluated and future work is described to further enhance the reliability and repeatability of grain scale strain measurements using Digital Image Correlation.M.S., Mechanical Engineering -- Drexel University, 201

Three-dimensional geometry characterization using structured light fields

Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 200

New advances in vehicular technology and automotive engineering

An automobile was seen as a simple accessory of luxury in the early years of the past century. Therefore, it was an expensive asset which none of the common citizen could afford. It was necessary to pass a long period and waiting for Henry Ford to establish the first plants with the series fabrication. This new industrial paradigm makes easy to the common American to acquire an automobile, either for running away or for working purposes. Since that date, the automotive research grown exponentially to the levels observed in the actuality. Now, the automobiles are indispensable goods; saying with other words, the automobile is a first necessity article in a wide number of aspects of living: for workers to allow them to move from their homes into their workplaces, for transportation of students, for allowing the domestic women in their home tasks, for ambulances to carry people with decease to the hospitals, for transportation of materials, and so on, the list don’t ends. The new goal pursued by the automotive industry is to provide electric vehicles at low cost and with high reliability. This commitment is justified by the oil’s peak extraction on 50s of this century and also by the necessity to reduce the emissions of CO2 to the atmosphere, as well as to reduce the needs of this even more valuable natural resource. In order to achieve this task and to improve the regular cars based on oil, the automotive industry is even more concerned on doing applied research on technology and on fundamental research of new materials. The most important idea to retain from the previous introduction is to clarify the minds of the potential readers for the direct and indirect penetration of the vehicles and the vehicular industry in the today’s life. In this sequence of ideas, this book tries not only to fill a gap by presenting fresh subjects related to the vehicular technology and to the automotive engineering but to provide guidelines for future research. This book account with valuable contributions from worldwide experts of automotive’s field. The amount and type of contributions were judiciously selected to cover a broad range of research. The reader can found the most recent and cutting-edge sources of information divided in four major groups: electronics (power, communications, optics, batteries, alternators and sensors), mechanics (suspension control, torque converters, deformation analysis, structural monitoring), materials (nanotechnology, nanocomposites, lubrificants, biodegradable, composites, structural monitoring) and manufacturing (supply chains). We are sure that you will enjoy this book and will profit with the technical and scientific contents. To finish, we are thankful to all of those who contributed to this book and who made it possible.info:eu-repo/semantics/publishedVersio

Fourier Transforms

The 21st century ushered in a new era of technology that has been reshaping everyday life, simplifying outdated processes, and even giving rise to entirely new business sectors. Today, contemporary users of products and services expect more and more personalized products and services that can meet their unique needs. In that sense, it is necessary to further develop existing methods, adapt them to new applications, or even discover new methods. This book provides a thorough review of some methods that have an increasing impact on humanity today and that can solve different types of problems even in specific industries. Upgrading with Fourier Transformation gives a different meaning to these methods that support the development of new technologies and have a good projected acceleration in the future