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Table of Content

    25 August 2023, Volume 41 Issue 4
    Civil Aviation
    Review of anomaly detection models based on deep learning
    ZHOU Maoyuan, WU Xiaoshuang
    2023, 41(4):  1-7. 
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    With the proliferation of data complexity, traditional methods for anomaly detection are no longer applicable, while deep learning can process complex data and perform anomaly detection by multi-layer neural network. Through  extensive research on domestic and international research results, firstly, anomaly detection and the types of detection methods are introduced. And deep learning based anomaly detection models are classified into three categories of generative-based model, reconstruction-based model and single classification-based model. Secondly,the construction principles and development context of deep anomaly detection models under different categories are sorted out, and the applicability, advantages and disadvantages of various models are analyzed. Then, the commonly used datasets and evaluation indicators for anomaly detection are introduced, and the performance of different models are compared and analyzed. Finally, the challenges faced by deep anomaly detection are summarized and the future research directions are prospected.
    Research on 16g longitudinal impact structure test of aviation rear facing seat
    LIN Ce, HUANG Zhiwei, ZHANG Kaining
    2023, 41(4):  8-15. 
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    According to the AC 25.562-1B standard of the Federal Aviation Administration (FAA), the 16 g longitudinal im鄄 pact structure tests of the forward facing and rear facing seats installed in a certain type of business aircraft were carried out to meet the airworthiness requirements of Part 25 of the Chinese civil aviation regulations (CAAR).By comparing with the test force transmission path, test condition, test index, test process and test results of the forward facing seat, the differential characteristics of the rear facing seat in the 16 g longitudinal impact structure test were researched. The results showed that the inertial load of the rear facing seat dummy directly acted on the backrest, compared with the load of the forward facing seat dummy transferred to the backrest by the restraint system. The test load severity of the rear facing seat was less than that of the forward facing seat, the seat leg's maximum resultant interface load was 1.9% - 21.9% smaller than that of the forward facing seat, and the longitu鄄 dinal maximum deformation is 29.1% - 40.7% smaller than that of the forward facing seat. Compared to the for鄄 ward motion of the forward facing seat dummy, the rear facing seat dummy slided upward along the backrest ob鄄 viously under the inertial load due to the poor initial upward restraint effect of the safety belt. Since the distance between the head and the headrest of the rear facing seat dummy was very close and the headrest foam had a cer鄄 tain energy absorption effect, the injury risk of dummy head hitting the headrest was relatively low according to the head injury criterion (HIC).
    Cybersecurity threat intelligence sharing scheme of civil aviation based on blockchain
    WU Yue, YA Junb , SUN Xianling , ZHOU Jingxiana , LYU Zongpinga
    2023, 41(4):  16-22. 
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    In order to effectively respond to new network threats such as supply chain and ransomware virus, as well as build an active defense system for civil aviation network security, this paper proposes a cybersecurity threat intelligence (CTI) sharing scheme of civil aviation based on blockchain and encryption technology. This scheme takes the competent department of civil aviation network security as the intelligence management center, and achieves i鄄 dentity authentication and intelligence transactions of civil aviation enterprises and institutions on the chain through smart contract. And proxy re-encryption is applied to process information to ensure the safe sharing of intelligence. Meanwhile, to ensure the security of threat intelligence storage, the interplanetary file system(IPFS) is used to store the encrypted threat intelligence data off chain, and only the hash value of the file is stored on the chain. Simulation experiments and security analysis results show that the proposed scheme can achieve intelli鄄 gence sharing among various civil aviation units with lower costs, and has higher privacy protection intensity than existing schemes.
    Research on ADS-B trajectory interpolation based on improved KNN detection
    JIN Huibin , FENG Chaohui , ZHANG Zhaoyue , WANG Zhisen
    2023, 41(4):  23-28. 
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    Aiming at the problem of anomalous points such as missing points and outliers in the data of automatic dependent surveillance broadcast (ADS-B) ground receiving station, the missing points of ADS-B trajectory are screened on the basis of establishing a multi-constraint discriminant model, and the trajectory is interpolated. The improved neighbor algorithm with standardized Euclidean metric is used to detect anomalous point data of the whole trajectory. Finally, the multiple interpolation method is applied to repair the anomalous trajectory points. Taking actual operational data as an example, the accuracy of the improved K-nearest neighbor (KNN) for detecting ADS-B anomalous trajectory points is verified and compared. This method can effectively solve the problem of detection omission of trajectory anomalous point and provide support for mining original trajectory data of aircraft ADS-B.
    Parameter estimation for radar non-uniform moving target based on time-frequency analysis
    YANG Lei, LEI Mengyao
    2023, 41(4):  29-36. 
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    For the parameter estimation of ground non-uniform moving targets of synthetic aperture radar (SAR), an adaptive notch filter (ANF) method based on Lv′s distribution (LVD) is proposed. Firstly, the mathematical model of radar echo is established according to the movement of ground non-uniform vehicle target, and the theoretical formulae of Doppler parameters and motion parameters of the echo signal are analyzed and deduced. Secondly, the pseudo Wigner-Ville distribution (PWVD) algorithm is used to extract the higher-order phase caused by higher-order motion in the echo signal, and the polynomial fitting method is applied to compensate. The motion compensated moving target signal is then aperture segmented along the azimuth direction, and each data block of sub aperture is time-frequency represented based on LVD algorithm, to estimate the variation curve of Doppler modulation frequency value. By utilizing the ANF, the high-frequency components caused by the radial acceleration of the moving target and the low-frequency components caused by the heading velocity in the modulation frequency signal are accurately separated. Finally, inversion calculation of the extracted high-frequency and low-frequency components of the modulation frequency rate are performed to obtain the estimated radial acceleration and heading velocity of non-uniform moving targets. Comparative experiments are conducted between the method proposed in this paper and the low-pass filter method based on LVD to verify that the proposed method can achieve higher accuracy in motion parameter estimation
    Research of critical deployment separation of cross-route of convergence aircraft
    DU Shi, CHU Xinyu
    2023, 41(4):  37-43. 
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    In order to reduce the deployment of the flight status of aircraft, this paper calculates the critical deployment sep aration based on the improved probability equilibrium method, taking the data of Shanghai Intelligence Center of the East China Air Traffic Control Bureau and the route structure of the navigation station in Pi County as an ex ample. The principle is that no deployment is required when the critical separation is less than actual separation, while deployment is required when the critical separation is bigger than actual separation, and the calculated result of the critical separation is 80.473 5 km. Then, the trichotomy is applied to determine the optimal decision-mak ing position, of which the actual separation of the critical separation at the decision-making point is 93.347 4 km (A470) and 91.362 9 km (A593). The results show that the controller can reduce the number of control deploy ments by adopting the corresponding strategies via the comparison of the critical separation value and actual sep aration at the decision-making point, and the deployment method of the controller can be unified.
    Measurement method of airline checked baggage based on#br# RGB-D image#br#
    ZHANG Wei , CHEN Yuhao , ZHANG Pan , CUI Ming
    2023, 41(4):  44-50. 
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    Aiming at the problem of low accuracy in baggage shape and position measurement in the automated process of airline checked baggage palletizing, a method for measuring the size and position of airline checked baggage based on RGB-D images is proposed. Firstly, the image and point cloud data of the baggage are resolved from the RGB-D image based on the internal parameters of camera, the 3D point cloud and 2D image data of the main part of the baggage subject are extracted through clustering and perspective transformation. Then, the baggage rotation angle is measured based on the extracted baggage image and point cloud data. Finally, the optimal rotation angle is selected for baggage size measurement based on the surrounding quality of the bounding box. The experimental results show that comprehensive utilization of baggage image and point cloud information in RGB-D can effectively improve the accuracy of measuring the shape and position of baggage. Compared to that of the measurement simply using point cloud, the average error of baggage size measurement is decreased by 21.11%, the average error of position measurement is decreased by 11.80% and the average error of rotation angle measurement is de creased by 6.09%. It has achieved high-precision measurement of airline checked baggage and met the require ments of automated baggage palletizing process for baggage measurement
    Dynamics of a grounded bistable nonlinear energy sink under periodic excitations
    LI Shuangbao , ZHOU Xinxing
    2023, 41(4):  51-57. 
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    As a lightweight and efficient passive vibration absorber, nonlinear energy sink (NES) can effectively suppress the harmful vibration of engineering structures, thus the study of the dynamics is significant for the design and opti鄄 mization of the vibration absorber. Under the periodic excitations, the response process of a coupled system of grounded bistable NES and main linear structure is studied to analyze the advantages of this kind of vibration ab鄄 sorber and propose design criteria. The complex averaging and multi-scale expansion methods are applied to an鄄 alyze the dynamics of the coupled system and the slow invariant manifold (SIM) and external excitation threshold of the coupled system are calculated. The chaotic threshold and the parameter optimization scheme of the coupled system are obtained based on the Melnikov method. Furthermore, the comparisons with the vibration absorbers of linear and cubic stiffness demonstrate the advantages of this grounded bistable NES
    Autonomous interference decision-making method based on genetic algorithm
    ZHU Zhuo , LIU Qiyan , ZHANG Ce
    2023, 41(4):  58-64. 
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    Aiming at the problem of low success rate of large high-value unmanned aerial vehicle (UAV) against infrared sur鄄 face-to-air missile, an autonomous interference decision-making model of infrared decoy delivery for typical confrontation situation is proposed combining with the use of infrared decoy. Firstly, to provide data support for the selection of delivery strategy of decoy, the sample library of infrared countermeasures is established based on the delivery strategy set of decoy and typical countermeasure situation. Secondly, the delivery strategy of decoy for typical confrontation situation is obtained based on genetic algorithm and decision matching. Finally, the nearoptimal autonomous countermeasure strategy model under any situation is obtained through tri-linear interpola鄄 tion idea and infrared countermeasure strategy migration model. The results of confrontation simulation experi鄄 ments in different infrared scenes show that the autonomous decision-making model proposed in this paper is ef鄄 fective and feasible.