KMS of Xinjiang Astronomical Observatory, CAS
| 大口径天线俯仰轴形变快速高精度测量与重构方法研究 | |
| Alternative Title | Research on Rapid and High-precisionMeasurement and Reconstruction Method of Large Aperture Antenna Pitch Axis Deformation |
于琳琳
| |
| Subtype | 硕士 |
| Thesis Advisor | 王娜 ; 许谦 |
| 2021-06-01 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学硕士 |
| Degree Discipline | 天文技术与方法 |
| Keyword | 虚拟相机 大射电望远镜 天线俯仰轴 小变形量 |
| Abstract | 大口径、高观测频段的射电望远镜，对于天线指向精度有着严苛的要求。影响天线指向精度的因素有天线结构、控制和环境等因素，对天线结构要求不仅在制造、安装，还有后期测量。研究长期运行过程中的磨损扭转造成的俯仰轴小尺度形变，为大口径射电望远镜天线指向精度修正、俯仰轴系统主动维护、以及制定和动态调整合理的望远镜观测计划提供重要支撑。天文领域内，当前天线关键结构测量研究工作主要在副面、副面六杆并联机构、轨道和座架等中、大尺度结构上，而俯仰轴小尺度结构研究很少，这是射电天文学发展中对大口径天线高性能要求上不可忽略的问题。视觉测量领域内，三维视觉定位技术具有非接触、高精度、快速性等特点，按设备可分为单目、双目和RGB-D相机，按靶标和信息类型可分为合作目标和非合作目标，或者人工靶标和图像特征。基于以上两方面的具体研究，本文设计了单相机形变测量方案，推导了测量方案的数学模型，提出了基于虚拟相机的俯仰轴形变测量方法。首先，确定俯仰轴形变测量方案设计和数学模型推导。具体来说，研究俯仰轴结构特点结合实际形变测量需求，设计了单相机形变测量方案，提出“虚拟相机”概念，对平移变换和旋转变换做了等价的数学解释，并给出了目标变换与虚拟相机变换的数学关系式。其次，介绍了本文采用的相机模型和标定方法。在线性模型基础上考虑了镜头畸变，采用了兼具方便性和高精度的张正友标定，得到相机内参和径向畸变系数。然后，提出了与相结合的虚拟相机空间变换的俯仰轴形变测量算法，主要步骤包括点特征提取和匹配、第一帧对应空间变换、其余帧对应的空间变换和非线性优化等。最后，通过光学测试平台实验和后期图像算法，验证了该方法在平移分量综合精度可达0.2825mm，旋转分量精度最低可达0.2918°，能够实现俯仰轴1mm尺度变形的快速测量。本文所提出的测量方案和算法在内的整套系统具有降低高精度靶标制作要求、结构简单、快速、精度高、便于维护等优点。 关键词：虚拟相机，大射电望远镜，天线俯仰轴，小变形量 |
| Other Abstract | The radio telescope with large aperture and high observation frequency has strict requirements for antenna pointing accuracy. Factors affecting antenna pointing accuracy include antenna structures, the control system and environment. The requirements for antenna structure are not only in manufacturing and installation, but also in post measurement. The study of the small-scale deformation of the pitch axis caused by wear and twisting during long-term operation provides important support for the correction of the pointing accuracy of large-aperture radio telescope antennas, the active maintenance of the pitch axis system, and the development and dynamic adjustment of a reasonable telescope observation plan.In the field of astronomy, the current research work on the measurement of key antenna structures is mainly on the medium and large scale structures such as the secondary surface, the secondary surface 6-DOF parallel mechanism, the orbit and the pedestal, while there is little research on the small scale structure of the pitch axis, which is a problem that cannot be ignored in the development of radio astronomy on the high performance requirements of large-aperture antennas. Within the field of vision measurement, 3D vision localisation techniques are characterised by non-contact, high accuracy and speed. They can be classified by equipment as monocular, binocular and RGB-D cameras. They can also be divided by target or information type into cooperative and non-cooperative targets, or artificial targets and image features. Based on the above two specific studies, this paper designs a single-camera deformation measurement scheme and proposes a virtual camera-based pitch-axis deformation measurement method.First, the design of the pitch axis deformation measurement scheme and the derivation of the mathematical model are determined. Specifically, a single camera deformation measurement scheme is designed by studying the structural characteristics of the pitch axis combined with the actual deformation measurement requirements. Next, the camera model and calibration method used in this paper are introduced. The lens distortion is considered on the basis of the linear model, and the Zhang Zhengyou calibration, which combines convenience and high accuracy, is used to obtain the camera internal parameters and radial distortion coefficients. The main steps include point feature extraction and matching, spatial transformation for the first frame, spatial transformation for the remaining frames and non-linear optimisation. Finally, through optical test platform experiments and post-image algorithms, it is verified that the method can achieve a comprehensive accuracy of 0.2825mm for the translation component and a minimum accuracy of 0.2918° for the rotation components, and can achieve rapid measurement of 1 mm scale deformation of the pitch axis. The complete system including the measurement scheme and algorithms proposed in this paper has the advantages of reduced requirements for high precision target production, simple structure, speed, high accuracy and ease of maintenance.Key Words: Virtual camera, Large radio telescope, The pitch axis, Small-scale deformation |
| Pages | 49 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/4731 |
| Collection | 研究生学位论文 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 于琳琳. 大口径天线俯仰轴形变快速高精度测量与重构方法研究[D]. 北京. 中国科学院大学,2021. |
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| 大口径天线俯仰轴形变快速高精度测量与重构（3062KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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