Approximate Fitting of a Circular Arc When Two Points Are Known

The task of approximating points with circular arcs is performed in many applications, such as polyline compression, noise filtering, and feature recognition. However, the development of algorithms that perform a significant amount of circular arcs fitting requires an efficient way of fitting circular arcs with complexity O(1). The elegant solution to this task based on an eigenvector problem for a square nonsymmetrical matrix is described in [1]. For the compression algorithm described in [2], it is necessary to solve this task when two points on the arc are known. This paper describes a different approach to efficiently fitting the arcs and solves the task when one or two points are known.Comment: 15 pages, 4 figures, extended abstract published at the conferenc

Geometric fitting by two coaxial cylinders

Fitting two coaxial cylinders to data is a standard problem incomputational metrology and reverse engineering processes, which also arisesin medical imaging. There are many fitting criteria that can beused. One that is widely used in metrology, for example, isthat of the sum of squared minimal distance. A similarnumerical method is developed to fit two coaxial cylinders inthe general position to 3D data, and numerical examples are given

Research on the Precise Shape-controlling Method of the Turbine Blade Film-cooling Hole Based on Ultrafast Laser

气膜冷却是一种通过在涡轮叶片表面设计大量线性排列的气膜孔，以形成薄层冷气膜隔离高温燃气的技术，可有效提高航空发动机热端部件的抗高温蠕变能力，其冷却效率与气膜孔的精度与质量息息相关。本文针对当前超快激光加工气膜孔存在的精度不高、质量不稳问题，修正了气膜孔的设计形位参数，建立了超快激光螺旋加工微小孔的工艺模型，分析了微小孔的时空演化过程。本论文的研究成果对提高气膜孔成形精度具有重要的理论意义与工程价值。 本文主要研究内容包括： 1.基于涡轮叶片定向凝固工艺，对叶片精铸过程进行了数值模拟，获得了叶片的铸件模型，结合叶片铸件的实测，建立了叶片精铸位移场模型。 2.采用变形特征补偿法，建立了叶片的...Film cooling can effectively improve the high-temperature creep ability of the aerial engine hot end parts by designing a large number of linearly arranged gas film holes on the turbine blade surface to form a thin layer of cold air to isolate high-temperature gas, whose cooling efficiency related closely to the accuracy and quality of the film holes. In this paper, the problems of low precision a...学位：工程硕士院系专业：航空航天学院_工程硕士(机械工程)学号：3202014115285

Extraction of tori from minimal point sets

International audienceA new algebraic method for extracting tori from a minimal point set, made of two oriented points and a simple point, is proposed. We prove a degree bound on the number of such tori; this bound is reached on examples, even when we restrict to smooth tori. Our method is based on pre-computed closed formulae well suited for numerical computations with approximate input data

Automatic 3D Mapping for Tree Diameter Measurements in Inventory Operations

Forestry is a major industry in many parts of the world. It relies on forest inventory, which consists of measuring tree attributes. We propose to use 3D mapping, based on the iterative closest point algorithm, to automatically measure tree diameters in forests from mobile robot observations. While previous studies showed the potential for such technology, they lacked a rigorous analysis of diameter estimation methods in challenging forest environments. Here, we validated multiple diameter estimation methods, including two novel ones, in a new varied dataset of four different forest sites, 11 trajectories, totaling 1458 tree observations and 1.4 hectares. We provide recommendations for the deployment of mobile robots in a forestry context. We conclude that our mapping method is usable in the context of automated forest inventory, with our best method yielding a root mean square error of 3.45 cm for our whole dataset, and 2.04 cm in ideal conditions consisting of mature forest with well spaced trees

Registration And Feature Extraction From Terrestrial Laser Scanner Point Clouds For Aerospace Manufacturing

Aircraft wing manufacture is becoming increasingly digitalised. For example, it is becoming possible to produce on-line digital representations of individual structural elements, components and tools as they are deployed during assembly processes. When it comes to monitoring a manufacturing environment, imaging systems can be used to track objects as they move about the workspace, comparing actual positions, alignments, and spatial relationships with the digital representation of the manufacturing process. Active imaging systems such as laser scanners and laser trackers can capture measurements within the manufacturing environment, which can be used to deduce information about both the overall stage of manufacture and progress of individual tasks. This paper is concerned with the in-line extraction of spatial information such as the location and orientation of drilling templates which are used with hand drilling tools to ensure drilled holes are accurately located. In this work, a construction grade terrestrial laser scanner, the Leica RTC360, is used to capture an example aircraft wing section in mid-assembly from several scan locations. Point cloud registration uses 1.5"white matte spherical targets that are interchangeable with the SMR targets used by the Leica AT960 MR laser tracker, ensuring that scans are connected to an established metrology control network used to define the coordinate space. Point cloud registration was achieved to sub-millimetre accuracy when compared to the laser tracker network. The location of drilling templates on the surface of the wing skin are automatically extracted from the captured and registered point clouds. When compared to laser tracker referenced hole centres, laser scanner drilling template holes agree to within 0.2mm