Table of Content

15 October 2022, Volume 40 Issue 5

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Civil Aviation

Analysis of integrity monitoring performance of airborne SBAS receiver

LIU Ruihua, LIU Jie, XI Zepu

2022, 40(5):  1-7. 

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The emergence of satellite based augmentation system(SBAS) can effectively improve the performance of the core constellation of global satellite navigation system. Especially in the field of civil aviation, SBAS has been widely used because it can generate higher-precision positioning and provide safer navigation services. With the measured data of navigation and augmented messages from different monitoring stations in the SBAS service area, the positioning accuracy and integrity message processing process, as well as the integrity parameter indexes such as visible star quality, positioning error, protection level and alarm threshold are studied. Targeting at the fault detection capability of integrity monitoring, the paper analyzes the integrity service performance of the satellite under different fault functions, and finally detects and eliminates the errors of SBAS. The results show that according to the decoding of the message and the algorithm of parameter extraction, better accuracy and integrity results can be obtained. The precision of each monitoring station can meet the requirements of LPV-200. The local ground station meets the integrity requirements of the LPV-200 approach by 100%, and remote stations all meet the integrity requirements of the LPV approach except for a few moments. After error elimination, the service performance is basically similar to that without failure.

Clutter suppression of wind farms for ATC surveillance radar based on BPDN

HE Weikun , BI Fenghua , ZHANG Ying , LI Shuang

2022, 40(5):  8-14. 

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Aiming at the problem of poor performance of wind farm clutter suppression with the morphological component analysis(MCA) method in low signal to clutter ratio(SCR), the paper proposes clutter suppression algorithm based on BPDN(the basis pursuit de-noising) with regard to different sparse characteristic for the clutter and airplane target in different transform domains. Firstly, based on BPDN method, the wind farm clutter is reconstructed in the time-frequency domain and eliminated from the observed echoes. Secondly, BPDN is utilized to extract the aircraft target signal in the frequency domain and to achieve wind farm clutter suppression in low SCR. The experiment results of simulation and measured data verify the effectiveness of the proposed method.

Object tracking algorithm based on dynamic weight in dual branch siamese network

HAN Ping , WANG Haowei , FANG Cheng

2022, 40(5):  15-22. 

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Some of siamese tracking algorithms represented by SiamFC are designed for target appearance information.However, appearance information is easily affected by factors such as high-speed movement, motion blur, and illumination changes, resulting in tracking drift or target loss. In order to improve the ability of the algorithm to adapt target appearance changes, this paper adopts a dual -branch siamese network tracking algorithm based on dynamic weights. Based on improved SiamFC algorithm as the appearance branch, a semantic branch using dual attention mechanism to enhance information extraction is added as an effective supplement. In the tracking stage, a dynamic weight is used to fuse the tracking results of the two branches, which effectively suppresses the influence of target appearance changes, also improves the tracking accuracy and robustness of the algorithm. Our algorithm has been validated on four standard object tracking data sets (OTB2015, UAV123, UAV20L, GOT-10k). The average tracking frame rate is 47 frames/s, which meets the real-time tracking requirements.


Joint performance of precast composite pavement and reflection crack suppression

ZHAO Hongduo , XIA Chang , FU Xiyuan , ZHAO Jufei , MA Lukuan

2022, 40(5):  23-30. 

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To prolong the service life of precast composite pavement, fatigue damage analysis and beam on elastic foundation theory are used for analyzing load-type reflection crack. Then, the relationship between adjacent plate deflection difference, joint width and the propagation life of load-type reflection crack is established by deriving the shear stress and bottom layer tensile stress of the asphalt overlay at the joints of precast composite pavement. The results show that the asphalt layer life can be effectively controlled through two factors: adjacent plate deflection difference and joint width. The crack extension life is shortened by increasing joint width and adjacent plate deflection difference and is extended by increasing asphalt pavement thickness. Finally, the initial value of plate deflection difference and joint width in different traffic load levels are delineated, the thickness of the asphalt layer should be greater than 0.1 m. In conclusion, this study establishes the grounds for the further application of precast composite pavement.

Experimental study on bonding property of sealing layer under pavement of airport asphalt concrete

HAO Xiuwen

2022, 40(5):  31-38. 

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In order to study the bonding performance of the sealing layer of asphalt concrete pavement in the airport, firstly, the regularities of interlayer shear strength of synchronous gravel sealing layer and asphalt sand sealing layer under different conditions are analyzed by oblique shear test. The results show that, at the same temperature and type of asphalt, the adhesion of asphalt sand sealing layer is better than synchronous gravel sealing layer; secondly, A380 -800 aircraft is taken as the evaluation model, ABAQUS finite element software is used for numerical simulation analysis, it turns out that asphalt sand sealing layer and synchronous gravel sealing layer can meet the requirements of shear strength, but the shear strength of asphalt sand sealing layer is much higher.

Indoor four-cable traction positioning and cable length solution

HE Yongbo, ZHAO Baoxi

2022, 40(5):  39-44. 

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Due to the working nature, the four -cable traction camera system in indoor aircraft maintenance is in static equilibrium when positioning, and the influence of internal disturbance on the cable length is mainly considered regardless of the dynamic characteristics in motion. In order to reduce the positioning error caused by the length of the suspension cable, improve the positioning accuracy of the four-cable traction system and maximize the reach range of the suspension cable, the relationship between the horizontal component of the suspension cable and the cable length is derived in the spatial O-XYZ coordinate system and a four-cable catenary model created based on the catenary principle and through the inverse solution analysis of the position. The SQP (sequential quadratic programming) algorithm is used to optimize the horizontal component of the suspension cable, so that the suspension cable tension is evenly distributed, the nonlinear equations are iteratively established to obtain the optimized suspension cable length. The simulation calculation shows that the algorithm has high accuracy, fast convergence and clear and simple calculation process. The cable force of the four cables is evenly distributed, which avoids the phenomenon of over-limit cable force and virtual traction.

Research on coupling evaluation of Chinese aviation logistics and foreign investment level

LI Guodong, ZHANG Jinjin

2022, 40(5):  45-50. 

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Promoting the coordinated development of aviation logistics and foreign investment is the basic path for aviation logistics to serve the country’s opening-up policy. Based on the panel data from 2009 to 2018, the gray correlation evaluation model and the coupling coordination degree model are constructed, and the coupling coordination between Chinese aviation logistics and foreign investment level is empirically analyzed from countries, regions and provinces. The results show that Chinese aviation logistics and foreign investment level are in a "good correlation stage" as a whole, but the coupling coordination among the seven regions is obviously polarized. In addition, there are totally different changes and distribution patterns in time and space of the coupling coordination degree between the two in 31 provinces. Therefore, China should formulate the development policy of aviation logistics industry according to the needs of foreign investment environment construction, so as to effectively promote the coupling coordination of the two.

Airworthiness Column

Numerical study on the effect of suction on the flow field quality improvement in a plane cascade

BAI Jie, YANG Zhao, FU Wenguang, SUN Peng

2022, 40(5):  51-58. 

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Improving the quality of the cascade flow field is particularly important for the plane cascade wind tunnel experiment, clarifying the relevant parameters of the upper and lower side plate suction, and understanding the influence of the side plate suction on the flow field, numerical simulation methods were used to study the effect of the suction slit width and the suction back pressure for the improvement effect of flow field quality. The results show that by reasonably changing the suction variable, the inlet uniformity and outlet periodicity of the cascade three channels in the middle and lower part can be effectively improved, so that the deviation of the inlet and outlet Mach number is less than 0.01, the airflow angle deviation is less than 0.5°, and the outlet channel uses T5 passage to refer to a better periodicity within the same error range, it is clear that the selection of the position of the monitoring point in front of the grid should be between T4 - T6 passage, and that the suction gap is 20 mm and the suction back pressure is 80 kPa. Thus better flow field quality is achieved and engineering needs are met.

Basic Science

Constructions of asymptotically optimal codebooks over Galois rings

XU Dengming , MENG Chen

2022, 40(5):  59-64. 

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Codebooks with low value of maximum cross-correlation amplitude are widely used in many fields. Four classes of codebooks are constructed by using Gauss sums and Jacobi sums over Galois rings. It is shown that these codebooks are asymptotically optimal with respect to Welch bound, and the codebook parameters are new and flexible. Based on the properties of Galois rings, it can be seen that these results can cover some results on finite fields when special values are taken, which makes new progress in the study of codebooks.