The minimal-distance between aero-engine pipelines is a very important parameter that can ensure the normal operation of the aero-engine. The traditional measurement method by using the feeler gauge is inefficient. This paper introduces the calculating method by using optoelectronic measurement system. In this way we can get the point cloud data of all the pipelines. Firstly, the points belonged to the same pipeline is picked up and saved in a group. Secondly, a set of equal-interval grid is built along a coordinate direction in which the pipeline stretched longest. Thirdly, on each trend-line point, a projection plane is built vertically to a straight line connecting the point and its adjacent point. Fourthly, the projected points on each projection plane are fitted into a circle using least square fitting method. Finally, traversing method is used to calculate minimal-distance between two groups of center-line points. And minimal-distance of two pipeline surfaces is calculated by subtracting radii of two pipelines from the minimal-distance of center-line points. Four groups of pipelines are examined to verify the proposed strategy. The results show that the deviations of minimal-distance of two pipeline surfaces are within -0.35mm~0.46mm. And the deviations of pipeline radius are within-0.1mm~0.29mm. The proposed method is more robust than mostly used method for calculating center-line data of pipeline.

The calculating method of minimal-distance between aero-engine pipelines by using optoelectronic measurement system

In order to solve the low precision and poor universality of the existing 6D sensors, a novel sensor is designed based on optical measurement. After the precision influence factor is analyzed, the numbers, layout and material of the target points on 6D sensor are especially considered. And then the structure of six points in the space by using infrared laser is designed. The double theodolites measurement network is used to calibrate the structure parameters of the sensor in order to improve precision. After the mathematic principle is given, both calculation methods for optimization based on Levenberg-Marquardt and the produce of the initial value based on lagrangian multiplier are stated. The experimental data show that the root-mean-square errors of three rotation angles are 0.017°，0.013°and 0.017°. The root-mean-square errors of three translation parameters are 0.077mm，0.095mm，0.079mm. The precision can meet the requirements and the 6D sensor can be successfully used in the manufacturing industry.

A high-precision 6D sensor based on optoelectronic measurement

Digital measurement technology used for aircraft assembly is to meet the requirements of each link in the aircraft assemble process, to integrate digital measurement into the aircraft assemble process, and to improving the accuracy of component assembly. At present, the measurement process involves a large number of departments such as design, manufacturing, product process, inspection, and assembly, which would result in a huge workload and volume of measurement data. In this context, a variety of digital measurement equipment, such as laser trackers, indoor GPS, laser scanners, photogrammetry systems, and laser radar, are used to from a collaborative measurement system, which is built to complete resource fusion and data fusion, so as to form a solution for on-site assembly with high precision, efficiency and flexibility. Firstly, according to the measurement process requirements, digital measurement technology should be integrated into all aspects of aircraft assembly, and a 3D measurement process model construction method is proposed. Then, in the process model, a digital method using multiple measurement devices is proposed. The corresponding algorithm and a method of calculating iterative initial values is proposed to improve the accuracy. Finally, a collaborative measurement platform based on laser tracker and indoor GPS is designed for the assembly process for the large part of an aircraft. The accuracy of the algorithm is verified, which proves the correctness and reliability of the method provided in this paper.

Research on collaborative measurement methods for aircraft digital assembly

With the continuous evolution of 5G technology, the integration of satellite communication network into global 5G network has been put on the agenda. LEO Satellite Constellation with its advantages of low delay and global coverage can form an effective supplement to the ground 5G mobile communication system, and provide infrastructure support for various services based on broadband access and Internet of things. It is an important direction of future communication development, and also a hot spot. However, with the development of study on 5G NTN (Non-Terrestrial Networks) network, due to the characteristics of high-speed mobile satellites and dynamic topology changes of LEO constellation, the problem of network integration between LEO constellation and 5G ground system becomes more and more prominent. According to the network characteristics of LEO constellation, the key technologies of network architecture, inter satellite routing and mobility management of LEO constellation based on 5G are studied in this paper, which can provide guidance for the networking design and engineering practice of LEO constellation networking based on 5G.

Research on key technologies of networking in 5G-based LEO satellite constellation system

The measurement requirements for civil aircraft components when using laser radar are always large-scale, high precision, high efficiency and so on, so several measuring stations are needed to construct a large-scale measuring network. Thus how to set up the layout of the stations is very important as it has direct influence with the precision. In this paper we develop a layout optimization method to solve the question in order to meet the requirements for precision and efficiency. The math model of the optimization is constructed by using the precision as constraints, and the solution is given to get the exact number and division of the laser radar. The initial layout can be obtained by the region growing algorithm to carry on the characteristics of discrete information and extract the discrete point method. And then we use the measurement uncertainty to optimize the results and the division. The experimental results show that compared with the experience-based manual layout, this method is more feasible and effective in obtaining large range and small number of measurement area division results and reasonable stations measurement stations. This experiment has verified the rationality, the correctness, the precision and effectiveness of the relevant methods.

Research on a laser radar measuring station layout optimization method for large civil aircraft components

The dynamic envelope measurement plays very important role in the external dimension design for high-speed train. Recently there is no digital measurement system to solve this problem. This paper develops an optoelectronic measurement system by using monocular digital camera, and presents the research of measurement theory, visual target design, calibration algorithm design, software programming and so on. This system consists of several CMOS digital cameras, several luminous targets for measuring, a scale bar, data processing software and a terminal computer. The system has such advantages as large measurement scale, high degree of automation, strong anti-interference ability, noise rejection and real-time measurement. In this paper, we resolve the key technology such as the transformation, storage and calculation of multiple cameras’ high resolution digital image. The experimental data show that the repeatability of the system is within 0.02mm and the distance error of the system is within 0.12mm in the whole workspace. This experiment has verified the rationality of the system scheme, the correctness, the precision and effectiveness of the relevant methods.

Research on an optoelectronic measurement system of dynamic envelope measurement for China Railway high-speed train

The article proposed a method to quantify corrosion characteristics of high strength alloy steel samples using digital image processing technique in color spaces. The distribution histograms in different channels of different spaces in corrosion images are plotted and analyzed. Select the proper color channel to extract the corrosion characteristics among three different spaces of RGB space, HSV space, YCbCr space. Combined the theory of corrosion generation, the data of color channels is processed and the feature of metal material salt spray corrosion is recognized. Through processing several sample color images of alloy steel, it is proved that the feature extracted by this procedure has better accuracy and the corrosion degree is quantifiable and the precision of discriminating the corrosion is improved.

Liqun Ma

Papers

Research on an optoelectronic measurement system of dynamic envelope measurement for China Railway high-speed train

Feature recognition of metal salt spray corrosion based on color spaces statistics analysis