Volume 25,2024 Issue 6

Military Aviation
• A Design and Simulation of a Cargo Door Servo Controller
  ZHI Wenjing1; LI Guocai1; WANG Tuanhui1; ZHENG Weijuan1; QU Wangbo1; LI Tong Wenjing1; LI Guocai1; WANG Tuanhui1; ZHENG Weijuan1; QU Wangbo1; LI Tong

  Abstract:In order to reduce the power demands of the electromechanical actuator (EMA) for a cargo door at a certain type of narrow-body aircraft and effectively control the impact of unknown disturbances on the controller, this paper designs a high-performance servo controller, and proposes a method of integrating velocity PI controller and current hysteresis tracking control by strategy. First, on the basis of deeply ana lyzing the complex load conditions during the operation of the EMA, the load characteristics of the cargo door in actual working conditions are obtained. And then, based on the load characteristics of the cargo door, the power demands of the controller’s motion control process are matched and designed, achieving the design of the controller’s architecture and the main functional circuit. Finally, to verify the effective ness of the proposed control strategy, a model of the controller is constructed by MATLAB/Simulink soft ware, and the opening-and-closing motion process of the cargo door is simulated. The simulation results show that the proposed control strategy can control the speed fluctuation range within ±120 rpm, effec tively reducing the system’s power consumption and significantly enhancing the controller's dynamic re sponse capability to external disturbances.

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• An Experimental Study of Dispersion of Residual Fatigue Life of Damage-Containing Structures of 30CrMnSiNi2A Alloy Steel and Its Influencing Factors
  CUI Ronghong; LI Xiaotao; ZENG Yilu

  Abstract:In order to explore the potential of residual fatigue life of damage-containing structures to meet the requirements of high reliability, the residual fatigue life test of damage-containing structures made of alloy steel material 30CrMnSiNi2A is carried out, and the residual fatigue life dispersion and its influencing factors are analyzed.The test procedures are simplified according to the results of fatigue comparison test between test pieces containing pre-cracked damage and pre-set wire-cut damage under equal amplitude spectral loading.The qualitative analysis of remaining fatigue life of damage-containing structures is performed under different heat treatment processes and different load levels. The test data show that the heat treatment process is able to improve the strength limit of alloy steel materials, reduce the load level, and effectively improve the remaining fatigue life of damage-containing structures. Under the conditions of different treatment processes and different load levels, with the increment of damage in size, the difference in the scattering factor of the remaining fatigue life increases. The damage being larger in size, the residual fatigue life of the heat-treated damage-containing structure test pieces under a low load level is lower, and the life dispersion is lower. By doing so, the remaining fatigue safety life can be effectively improved to meet the reliability requirements.

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• A Fault Detection of Electromagnetic Relay Based on Time Parameter Fusion
  LEI Xiaoben1 ; WANG Hao1 ;XIAO Qiaoyuan2 ;WU Fan2 ; HU Xinhua1; WANG Luyao3

  Abstract:It is difficult for a single feature to comprehensively reflect the degradation fault of electromagnetic relay. A fault detection method of electromagnetic relay is proposed based on time parameter fusion by selecting the pick-up time, release time and super-path time as multiple fault characteristic variables according to the fault mechanism of relay. Firstly, In consideration of the fuzzy uncertainty of the degraded fault, the fuzzy membership function is constructed according to the fuzzy threshold of the feature, and the membership degree of the data to the working state of the relay is obtained and expressed as fault evidence, and then the evidence reasoning algorithm is applied to the fusion of the multi-feature fault evidence to get the relay fault information. Finally, the fault detection results are obtained by iteratively fusing the historical, current and predicted fault information, and adaptively adjust the reliability of the fault information, taking into account the reliability and sensitivity of the detection results. The experimental results show that the proposed method is 5.2% in mistake report rate, 2.0% in failure to report rate, has significant advantages in accuracy and anti-interference ability, and can effectively improve the performance of electromagnetic relay degradation fault detection.

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• A Prediction of Fatigue Life for Aviation Hydraulic Pipelines in Combination with High and Low Cycle Loading
  HUA Tengfei; LIU Hao; LI Jing; QIU Yuanying

  Abstract:In order to predict the fatigue life of aviation hydraulic pipelines reliably, on the basis of existing fatigue life prediction methods being insufficiency for hydraulic pipelines and in view of the stress characteristics of aircraft hydraulic pipelines, the types of loads acting on hydraulic pipelines are analyzed and their loads are decomposed, a fatigue life prediction method is proposed for the hydraulic pipeline under combined high and low cycle loading. Subsequently, a simulation analysis is performed on a specific type of aircraft hydraulic pipeline by using the Ansys Workbench to validate the effectiveness of the proposed method. Based on this analysis, fatigue life predictions are made in consideration of both high and low cycle loads, and under no consideration of the effects of high and low cycle loads. The results show that the effect of combined high and low cycle fatigue loads has a significant influence on the fatigue life of hydraulic pipeline. When the fatigue life of hydraulic pipelines is subjected to the prediction, it is necessary to consider the effects of both high cycle fatigue loads and low cycle fatigue loads simultaneously.

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• A Fault Diagnosis for Inter-Shaft Bearing of Aero-Engine Based on Improved SE-ResNet-BiLSTM
  YU Wankang1;3; LENG Ziwen2; GAO Junwei1;3; CHE Luyang 1;3

  Abstract:Aimed at the problems that fault diagnosis is low to accuracy caused by extracting fault features difficultly, and vibration signals of inter-shaft bearing on aero-engine are susceptible to noise interference at present, a fault diagnosis method is proposed for aero-engine inter-shaft bearing based on the improved residual attention network and bidirectional long short-term memory neural network(BiLSTM). Firstly, taking the original vibration signal as a model input, the local spatial features are extracted from the raw data by utilizing one-dimensional wide convolution, and the high-frequency noise is suppressed. And then, a residual network in combination with the improved channel attention is utilized for enhancing model attention to important features and reducing model com putational complexity, and the processed features are input into BiLSTM to further extract temporal correlation features. Finally, the features are input into the Softmax layer for fault classification. The experimental validation is conducted by using the Harbin Institute of Technology Aeroengine intershaft bearing dataset, and the results show that the proposed model can maintain the diagnostic accuracy of 98.64% even in the high noise environment with the signal-to-noise ratio of -4 dB, is prior to the other comparative models, and has the better ability to extract features and resist noise.

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Electronic Information and Communication Navigation
• Research on Composite Scattering Characteristics of Multi-Targetabove Rough Environment
  LI Ning1; TIAN Guilong1; WANG Tong1; MA Jinwen2

  Abstract:In view of the scattering calculation problem of multiple 3D conductor targets located above the rough surface, this paper proposes a hybrid AIM-PO algorithm of adaptive integral method (AIM) combined with physical optic (PO) method. In this algorithm, the scattering from rough surface is calculated by PO, and the scattering from target is calculated by AIM. The scattering from the rough surface is solved as part of the target impedance matrix, and the target the rough surface are solved as a whole. The most important computational bottleneck comes from the complement of the coupling matrix between the target and the rough surface in the process of solution. In order to overcome such a computational bottleneck, a fast multipole algorithm (MLFMA) combined with a fast far field approximation (FaFFA) algorithm is proposed to accelerate the matrix vector multiplication. The method is based on the far field approximation criterion to divide the rough surface area into near and far regions, i.e., the distance between the upper element of the rough surface and the target satisfied with the far field approximation conditions is classified as a far region, otherwise is classified as a near region. The near zone is accelerated by MLFMA, whereas the far zone is accelerated by FaFFA. Compared with the traditional numerical algorithm, the proposed algorithm has high computational accuracy, and can effectively improve the computational efficiency. Finally, the variation law of multi-target and environment composite scattering characteristics under different conditions is analyzed by numerical calculation.

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• Influence of T/R Component Fault on DBF and Maintenance Strategy
  PENG Fang1; ZHANG Bing2; SHANG Baopeng3; XIANG Jianjun1; WU Jun4

  Abstract:In view of maintainability and maintenance timing for T/R components of phased array radar in which the fault number is less than 10%, a rule of channel fault forming the influence on DBF is analyzed, and a maintenance strategy to keep radar performance from degradation is proposed. First, mathematical models of transmitting DBF and receiving DBF based on LMS algorithm are established based on the structure of planar array. And then, the transmitting and receiving beam forming performance of T/R components are verified in both normal condition and partial failure through the simulation, and the influence of fault number and fault region on receiving DBF performance and radar detection performance is analyzed by using five indicators. Finally, its internal law is analyzed, and the maintenance strategy is putted forward, providing theoretical basis and decision support for scientific and precise maintenance and operational effectiveness.

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• An Analysis of Troposcatter Propagation Slant Delay Based on ERA5 Pressure Level Meteorological Data
  SUN Haoran; LIU Qiang; HU Denghua; ZHANG Shuang

  Abstract:Aimed at the problem that the current numerical model of tropospheric scattering turbulence fails to effectively reflect the influence of the meteorological environment on tropospheric scattering propagation, the fifth-generation global climate reanalysis dataset (ERA5) pressure level meteorological data of the European centre for medium-range weather forecasts (ECMWF) is introduced into the high-precision tropospheric scattering delay calculation model, and 12 scattering links in six typical geographical regions of China, i.e. Tibet Plateau, North China Plain, Sichuan hill, Yunnan-Guizhou mountain, Longmeng desert are selected. The ERA5 hourly data on pressure levels (ERA5 MPL) and ERA5 monthly averaged data on pressure levels (ERA5 MPL) are used to calculate and analyze the trend of tropospheric skew delay of each link in different geographical environments respectively, and simultaneously the results of the calculation of the two data sets are compared. The results show that the calculation method of troposcatter propagation slant delay given in this paper is suitable for ERA5 pressure level meteorological data, the maximum standard deviation in the results obtained by the two data sets on different links is 2.9 m, and the timing accuracy difference is less than 10 ns.

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• A Study of Topology Repair of Ground-Based Air Defense Communication Based on Multivariate Weight Functions
  REN Fenglin; WANG Gang; LI Tengda

  Abstract:Conducted research on the topology repair problem of ground air defense communication networks. Firstly, the topology is preprocessed based on the multivariate weight function and connectivity dominating set, and the fault handling links are planned for the key nodes affecting the connectivity of the topology. Secondly, when a fault occurs, the network topology restores connectivity by cascading node movement. A weight function is constructed according to the characteristics of the ground defense communication network, and the generated fault handling links are more suitable to the needs of the ground defense. The topology cut-points are solved on the basis of the dominating set of the connectivity, so as to optimize the logic and efficiency of the topology operation after node failures, and to shorten the fault handling time effectively. The algorithm is used for topology repair of the randomly generated 20-node ground defense communication network, and the generation of the nodes in the connectivity dominating set with the shortest fault processing links. Failure to arbitrary node is selected in the network, there is no isolated node in the network with the fault being processed, proving that the algorithm can effectively deal with single node failure of ground defense communication topology repair problem.

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Unmanned Combat
• Research on Autonomous Maneuver Decision Method for Unmanned Aerial Combat Based on an Improved PPO Algorithm
  ZHANG Xin1; DONG Wenhan1; YIN Hui2; HE Lei1; ZHANG Pin1; LI Dunwang1

  Abstract:An application of deep reinforcement learning makes it possible for unmanned aerial vehicles to complete an autonomous maneuver decision-making.This paper proposes an unmanned combat aerial vehicle (UCAV) autonomous air combat maneuver decision-making method based on the reconstruction of situational assessment models in combination with the proximal policy optimization (PPO) algorithm, providing effective strategy choices for 1 vs 1 within visual range (WVR) air combat.In response to the problem of low model fidelity, this paper, firstly, establishes a dynamic model of a six degree of freedom UCAV and defines the attack mode of WVR air combat. And then, in order to improve the adequacy of the situational assessment model in describing air combat, this paper reconstructs the angle, speed, distance, and altitude situational functions based on the division of air combat states, and proposes a new situational function that describes the potential for maneuver. In terms of reward function design, in addition to rule-based sparse rewards, sub target rewards are established based on the transforma tion of air combat states, and shaping reward functions are designed based on situational functions to enhance guidance capabilities. Finally, an expert system is designed to be a competitor to evaluate the work presented in this paper on the high fidelity air combat simulation platform (JSBSim). The simulation verification shows that being confronted with the fixed maneuvering opponents and expert system opponents, the intelligent agent enables to effectively improve the convergence speed and winning rate of the algorithm by using the method proposed in this paper.

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• A Complex Obstacle Escape Path Planning Method Based on Random Tree Potential Field Function
  LI Jinpeng1 ; WEI Ruixuan1 ; SHI Ruqiang1; XIONG Peng2

  Abstract:A drone needs to plan flight paths to the satisfaction of constraints according to the external environment in the process of mission execution. Aimed at the problems that local minimum is in existence in the traditional artificial potential field (APF) planning paths, and the failure of path planning is unable to get out of the trap, narrow path oscillation and other defects, a complex obstacle escape path planning method is proposed based on random tree potential field (RTPF). First, a discrete drone environment map model is established to generate a random tree path in each environment map by using rapidly exploring random trees (RRT), and a random tree potential field function is designed to construct the potential field for the path nodes. And then, by reasonably designing the parameters and introduction timing of random tree potential field, the drone is guided to escape from the potential field environment in the defective situation, solving the defective problem of the traditional artificial potential field method. Finally, the algorithm in the paper is simulated and analyzed with the comparison algorithms. The results show that com pared with the fast search random tree algorithm and the traditional artificial potential field method, the algorithm in the paper completes the path planning in all obstacle cases and shortens the length of planned path, further improving the safety and effectiveness of path planning.

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Cyberspace Countermeasures
• Nonlinear Frequency Offset Self-Interference and Channel Joint Estimation Method in UWB Millimeter Wave MIMO-OFDM Systems
  SUN Qilu; ZHANG Bo; LI Taoyong

  Abstract:In performance, carrier frequency offset generated by the system synchronization can cause not only nonlinear frequency offset self-interference in the ultra-wideband millimeter-wave multi-input multioutput (MIMO) orthogonal frequency division multiplexing (OFDM) system, but also influence of subsequent channel estimation performance. For this reason, this paper proposes a method for joint estimation of nonlinear frequency offset self-interference and channel, by exploiting the hyper-dimensional hidden space of data, reducing the complex multi-objective optimization problem into multiple parallel solvable sub-optimization problems, and using the sparse characteristics of ultra-wideband millimeter wave channels to realize iterative estimation of carrier frequency offset and channel based on compressive sensing. Compared with the existing methods, the simulation results show that the proposed method can effectively reduce the computational complexity by nearly one order of magnitude, improve the accuracy of channel estimation, and reduce the system bit error rate.

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• A Network Security Situation Prediction Based on Empirical Mode Decomposition and Improved Temporal Transformer
  SUN Junfeng1;2 ; LI Chenghai1 ; SONG Yafei1 ; NI Peng3

  Abstract:Aimed at the problems that the network security situation prediction task is complex, and high in noise of data in real environments, a network security situation prediction method is proposed based on empirical mode decomposition (EMD) and improved temporal Transformer (ITTransformer). The complete EEMD with adaptive noise (CEEMDAN) method is utilized for de-noising and pre-processing network security situation data in real environments through “decomposition-reconstruction”. The paper proposes ITTransformer. The Temporal Transformer module is used to extract the time-depth global features from the network security situation data sequences. An Attention Fusion mechanism is proposed to realize the adaptive fusion of temporal features to complete the prediction task in a more robust feature fusion way. The experimental results show that the method proposed in this paper is superior in prediction accuracy to the other methods, and its coefficient of determination reaches 0.997 860, and the fitting efficiency is good.

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Airport Protection
• Research on Performance at Early Stage for Epoxy Resin Based Mortar under Curing Conditions at High Temperature
  XIA Wei1; BAI Erlei1; LYU Yan2; XU Jinyu1;3; QIN Lijun1

  Abstract:Epoxy resin is sensitive to temperature, so it is necessary to explore the influence of curing temperature on the performance of epoxy resin based mortar. In order to further clarify the evolution law of early physical and mechanical properties of epoxy resin based mortar under curing conditions of different high temperature (30~60 ℃), its setting time, flexural strength, and compressive strength are tested. And the microstructure characteristics of epoxy resin based mortar are analyzed in combination with scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The experimental results show that with the increment of curing temperature, the setting time of epoxy resin based mortar shortensgradually, and there is a roughly linear decreasing relationship between the setting time and the curing temperature. Under curing conditions of high temperature, with the increment of temperature, the flexural strength and compressive strength of epoxy resin mortar at an early age (4 h~3 d) first slowly increase, and then sharply decrease. When the curing temperature is at 40 ℃, the strength characteristics of epoxy resin based mortar are relatively optimal, and the flexural strength and compressive strength of the specimens cured for 4 h reach 21.4 MPa and 56.8 MPa respectively. Under the curing conditions of 40 ℃, the curing reaction of epoxy resin based mortar is complete relatively, and the internal structure of the matrix is uniform and dense, without obvious micro defects such as pores and cracks. However, under the curing conditions of 60 ℃, the curing reaction of epoxy resin based mortar is not sufficient, and the internal structure of the matrix is loose relatively and disordered with a significant increment of micro defects.

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• Research on Influence of Fiber Orientation and Concrete Interlayer on Mechanical Properties of Layered Steel Fiber-Reinforced Concrete
  CHEN Xuan1; JI Yongan2; OU Yabin2; LI Mengshen1; KUANG Dongliang1

  Abstract:For the convenience of analyzing influence of fiber orientation and concrete interlayer on mechanical properties of layered steel fiber-reinforced concrete (LSFRC), firstly, layered steel fiber-reinforced concrete samples with three kinds of fiber content of 0.5%~1.5% are tested for compressive strength, shear strength and flexural tensile strength experiment respectively. And then, fine models of cubic and prismatic LSFRC samples are established by using finite element to analyze effects of fiber content, fiber orientation and the interlayer between concrete layers. The experimental results show that LSFRC exhibit a maximum increment of 58% in flexural strength range. The numerical analysis indicates that the interlayer maximum shear stress is reduced by 10.8% in LSFRC prismatic samples, and the deflection at the bottom of prismatic samples is decreased by 17.3%. The study demonstrates that the bonding states between inter-layers have a significant effect on the loading of specimens. The incorporation of steel fibers is the result of a local stress concentration and an integral stress dispersion in the part of samples, whereas the steel fibers restrain the deformation of zone, improving the bending resistance of concrete.

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