Optimal field coverage path planning on 2D and 3D surfaces

With the rapid adoption of automatic guidance systems, automated path planning has great potential to further optimize field operations. Field operations should be done in a manner that minimizes time, travel over field surfaces and is coordinated with specific field operations, machine characteristics and topographical features of arable lands. To reach this goal, intelligent coverage path planning algorithm is key. This dissertation documents our innovative research in optimal field coverage path planning on both 2D and 3D surfaces. To determine the full coverage pattern of a given 2D planar field by using boustrophedon paths, it is necessary to know whether to and how to decompose a field into sub-regions and how to determine the travel direction within each sub-region. A geometric model was developed to represent this coverage path planning problem, and a path planning algorithm was developed based on this geometric model. The search mechanism of the algorithm was guided by a customized cost function resulting from the analysis of different headland turning types and implemented with a divide-and-conquer strategy. The complexity of the algorithm was analyzed, and methods for reducing the computational time were discussed. Field examples with complexity ranging from a simple convex shape to an irregular polygonal shape that has multiple obstacles within its interior were tested with this algorithm. The results were compared with other reported approaches or farmers\u27 actual driving patterns. These results indicated the proposed algorithm was effective in producing optimal field decomposition and coverage path direction in each sub-region. In real world, a great proportion of farms have rolling terrains, which have considerable influences to the design of coverage paths. Coverage path planning in 3D space has a great potential to further optimize field operations. To design optimal coverage paths on 3D terrain surfaces, there were five important steps: terrain modeling and representation, topography impacts analysis, terrain decomposition and classification, coverage cost analysis and the development of optimal path searching algorithm. Each of the topics was investigated in this dissertation research. The developed algorithms and methods were successfully implemented in software and tested with practical 3D terrain farm fields with various topographical features. Each field was decomposed into sub-regions based on terrain features. An optimal seed curve was found for each sub-region and parallel coverage paths were generated by offsetting the seed curve sideways until the whole sub-region was completely covered. Compared with the 2D planning results, the experimental results of 3D coverage path planning showed its superiority in reducing both headland turning cost and soil erosion cost

Sampling-Based Coverage Path Planning for Inspection of Complex Structures

We present several new contributions in sampling-based coverage path planning, the task of finding feasible paths that give 100% sensor coverage of complex structures in obstacle-filled and visually occluded environments. First, we establish a framework for analyzing the probabilistic completeness of a sampling-based coverage algorithm, and derive results on the completeness and convergence of existing algorithms. Second, we introduce a new algorithm for the iterative improvement of a feasible coverage path; this relies on a sampling-based subroutine that makes asymptotically optimal local improvements to a feasible coverage path based on a strong generalization of the RRT algorithm. We then apply the algorithm to the real-world task of autonomous in-water ship hull inspection. We use our improvement algorithm in conjunction with redundant roadmap coverage planning algorithm to produce paths that cover complex 3D environments with unprecedented efficiency.United States. Office of Naval Research (ONR Grant N0014-06-10043

Interactive Video Game Content Authoring using Procedural Methods

This thesis explores avenues for improving the quality and detail of game graphics, in the context of constraints that are common to most game development studios. The research begins by identifying two dominant constraints; limitations in the capacity of target gaming hardware/platforms, and processes that hinder the productivity of game art/content creation. From these constraints, themes were derived which directed the research‟s focus. These include the use of algorithmic or „procedural‟ methods in the creation of graphics content for games, and the use of an „interactive‟ content creation strategy, to better facilitate artist production workflow. Interactive workflow represents an emerging paradigm shift in content creation processes used by the industry, which directly integrates game rendering technology into the content authoring process. The primary motivation for this is to provide „high frequency‟ visual feedback that enables artists to see games content in context, during the authoring process. By merging these themes, this research develops a production strategy that takes advantage of „high frequency feedback‟ in an interactive workflow, to directly expose procedural methods to artists‟, for use in the content creation process. Procedural methods have a characteristically small „memory footprint‟ and are capable of generating massive volumes of data. Their small „size to data volume‟ ratio makes them particularly well suited for use in game rendering situations, where capacity constraints are an issue. In addition, an interactive authoring environment is well suited to the task of setting parameters for procedural methods, reducing a major barrier to their acceptance by artists. An interactive content authoring environment was developed during this research. Two algorithms were designed and implemented. These algorithms provide artists‟ with abstract mechanisms which accelerate common game content development processes; namely object placement in game environments, and the delivery of variation between similar game objects. In keeping with the theme of this research, the core functionality of these algorithms is delivered via procedural methods. Through this, production overhead that is associated with these content development processes is essentially offloaded from artists onto the processing capability of modern gaming hardware. This research shows how procedurally based content authoring algorithms not only harmonize with the issues of hardware capacity constraints, but also make the authoring of larger and more detailed volumes of games content more feasible in the game production process. Algorithms and ideas developed during this research demonstrate the use of procedurally based, interactive content creation, towards improving detail and complexity in the graphics of games

Appearance Modelling and Reconstruction for Navigation in Minimally Invasive Surgery

Minimally invasive surgery is playing an increasingly important role for patient care. Whilst its direct patient benefit in terms of reduced trauma, improved recovery and shortened hospitalisation has been well established, there is a sustained need for improved training of the existing procedures and the development of new smart instruments to tackle the issue of visualisation, ergonomic control, haptic and tactile feedback. For endoscopic intervention, the small field of view in the presence of a complex anatomy can easily introduce disorientation to the operator as the tortuous access pathway is not always easy to predict and control with standard endoscopes. Effective training through simulation devices, based on either virtual reality or mixed-reality simulators, can help to improve the spatial awareness, consistency and safety of these procedures. This thesis examines the use of endoscopic videos for both simulation and navigation purposes. More specifically, it addresses the challenging problem of how to build high-fidelity subject-specific simulation environments for improved training and skills assessment. Issues related to mesh parameterisation and texture blending are investigated. With the maturity of computer vision in terms of both 3D shape reconstruction and localisation and mapping, vision-based techniques have enjoyed significant interest in recent years for surgical navigation. The thesis also tackles the problem of how to use vision-based techniques for providing a detailed 3D map and dynamically expanded field of view to improve spatial awareness and avoid operator disorientation. The key advantage of this approach is that it does not require additional hardware, and thus introduces minimal interference to the existing surgical workflow. The derived 3D map can be effectively integrated with pre-operative data, allowing both global and local 3D navigation by taking into account tissue structural and appearance changes. Both simulation and laboratory-based experiments are conducted throughout this research to assess the practical value of the method proposed

(MIS)REPRESENTED MASCULINITIES: DISCOURSE AND DISRUPTION IN CANADIAN FIGURE SKATING

Canadian media outlets have paid significant attention to figure skating, increasingly in reference to the competitive careers of male, Canadian skaters. This analysis investigates the particular representations of masculinity that are textually produced and reproduced in journalism from the Globe and Mail and autobiographical writings from select figure skaters. Drawing from the methodology of critical discourse analysis as developed by Norman Fairclough and the theory of hegemonic masculinity from R.W. Connell, these three case studies examine the careers of Toller Cranston, Kurt Browning, and Elvis Stojko. Through an analysis of the careers of these figure skaters which spans four decades, various notions and representations of hegemonic masculinity are documented. Additionally, this study analyzes how these shifts reflect broader socio-historical knowledge in an attempt to construct a unified image of Canada and national discourse

Exploring human-object interaction through force vector measurement

Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 101-107).I introduce SCALE, a project aiming to further understand Human-Object Interaction through the real-time analysis of force vector signals, which I have defined as "Force-based Interaction" in this thesis. Force conveys fundamental information in Force-based Interaction, including force intensity, its direction, and object weight - information otherwise difficult to be accessed or inferred from other sensing modalities. To explore the design space of force-based interaction, I have developed the SCALE toolkit, which is composed of modularized 3d-axis force sensors and application APIs. In collaboration with big industry companies, this system has been applied to a variety of application domains and settings, including a retail store, a smart home and a farmers market. In this thesis, I have proposed a base system SCALE, and two additional advanced projects titled KI/OSK and DepthTouch, which build upon the SCALE project.by Takatoshi Yoshida.S.M.S.M. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Science

Coverage Path Planning with Real‐time Replanning and Surface Reconstruction for Inspection of Three‐dimensional Underwater Structures using Autonomous Underwater Vehicles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113717/1/rob21554.pd

Ultraviolet-induced fluorescence and photo-degradation in zinc oxide watercolour paints

Paper conservators tasked with the care and treatment of collections containing watercolours often encounter paper which has undergone severe discolouration and deterioration around Chinese white pigments, an effect caused by the photocatalytic reaction between surface electrons on the pigment particles and atmospheric moisture, leading to peroxide formation and oxidation of surrounding paper. This discolouration is difficult to treat and best avoided if possible. While conservators use ultraviolet-induced fluorescence to identify zinc oxide pigments by their intense visible fluorescence, they cannot presently relate zinc oxide’s variety of fluorescent colours and intensities to its rate of photocatalysis. This thesis aims to link types of ultraviolet-induced fluorescence with zinc oxide’s photocatalytic behaviour by examining the physical, chemical and optical properties of mock-up zinc oxide pigments in gum medium and historic watercolour painting case studies and determine whether this fluorescence could be quantified using commercially available DSLR cameras for predicting and diagnosing degradation in watercolours. The investigation first collected and summarising art manuals and literature detailing zinc oxide’s history and use as a watercolour pigment. This uncovered a near-consensus in the nineteenth century about the inert nature of zinc oxide, along with evidence that Winsor and Newton, the only supplier for nearly a century, annealed their pigments to improve their working properties and reduce their photoconductivity. No other suppliers could produce a good pigment and there were lone voices warning that zinc oxide may be damaging to surrounding materials. Physical properties of pigments produced by the direct and indirect method as well as commercial and historic case study pigments were examined via x-ray diffraction (XRD), x-ray fluorescence (XRF), energy-dispersive x-ray spectroscopy (EDX) and digital image analysis of micrographs and scanning electron microscopy (SEM) images. XRD and EDX verified the purity of all samples, while XRF revealed a much higher impurity content among direct method pigments than all others. Particle and crystallite sizes and morphologies derived from image analysis of micrographs and SEM images found that commercial and case study pigments were produced by the indirect method, that these had much smaller and shorter crystallites than direct method pigments and that these crystallites were more likely to be photoactive than the long crystallites of the direct method pigments. The photocatalytic properties of mock-ups were studied via light exposure for 50 hours and subsequent measurements of peroxide formation via Russell-grams which imaged peroxides on indirect and commercial pigments. Colour changes were measured via a colorimeter and indicated that bleaching was the dominant effect, with most pigments causing browning on Whatman filter paper. Analysis of absorption spectra indicated that band gaps were narrowest for direct method pigments and wider for all others, a quality which lengthens the time that excited electrons are available for reactions. Visible deterioration was localised to materials in direct contact with pigments, evidenced by the embrittlement of binding media when paint sat on highly-sized paper and the browning of paper fibres when size was not present and paint was more embedded in the paper substrate. Fluorescent characteristics were studied with fluorimetry and digital image processing with the goal of determining what qualities relate to photocatalysis. Indirect method pigments including commercial and case study pigments had a strong blue contribution, quantified via a green/blue ratio derived from the fluorescent peak areas and sRGB colour channel intensity values. This ratio was consistently low for photocatalytic pigments as evidenced by peroxide formation and visual deterioration. Historic case studies which were photographed using different cameras and lighting scenarios still were grouped according to this ratio, which was low if visible deterioration was present. Green/blue sRGB colour channel ratios increased after 50 hours of light exposure, indicating that the surface defects responsible for green fluorescence increased over time. These defects are also responsible for reducing photoactivity; however, given the age of case studies and the similarity in fluorescence between historic pigments and modern photoactive pigments, an endpoint for reactions could not be determined and may not exist. The green/blue ratio appears to be a reliable indicator of photoactivity even after periods of a century or more. More work is needed to standardise image processing procedures to make the method more quantitative, though comparisons within data sets in this study are a reliable indicator of peroxide formation on pigment particle surfaces. Given the difficulty in treating watercolours damaged by zinc oxide and the evidence presented here of its lengthy photoactivity, paper conservators should avoid using the pigment for retouching and focus on stabilisation and prevention. Localised reduction of staining using alkalis below pH8 may be carried out with caution as strong alkalis dissolve zinc oxide pigments. Consolidation of cracked paint, when carried out after the removal of sulphate salts in a wash, both reintroduces the binder and provides a temporary barrier between surface electrons on pigment particles and surrounding paper, slowing the oxidation of paper cellulose by peroxides

A Technical Study of the Mural Paintings of the Interior Dome of the Capilla de la Virgen del Rosario, Iglesia San José, San Juan, Puerto Rico

This is a technical study of the extant murals of the 17th Capilla de la Virgen del Rosario located within Iglesia San José, San Juan, Puerto Rico. The primary objectives of this investigation were to: document existing mural campaigns, establish a chronology of mural painting through analysis of materials and techniques, evaluate the conditions of the paintings and to determine possible deterioration mechanisms, and propose recommendations for their conservation and interpretation. In-situ documentation including color digital photography, extensive field notes, and mapping of visible painting campaigns were conducted. This was followed by a materials analysis of select campaigns’ substrate, binders, and pigments. Test methods included gravimetric analysis and XRD of substrate plasters, examination of cross-sections and pigment dispersions, EDS analysis of pigments, and FTIR analysis of binders. The results of this study found six distinct mural campaigns and established a chronology which attributed painting phases to the Dominican, Jesuit, and Vincention orders of the Catholic Church. Notable iconography include the 17th century mer creatures (la serena), and the mid-19th century depiction of the Battle of Lepanto. Substrate analysis revealed a lean plaster mix in the enfoscado as an intrinsic cause of failure, further aggravated by continued water infiltration. Water ingress has created an environment supporting threatening deterioration mechanisms including abundant chloride salts, and biological growth contributing to failing paint layers and plasters. The Rosario Chapel murals are highly significant and warrant a comprehensive strategy for their conservation and interpretation through a collaborative process involving all stakeholders