Table of Content

30 August 2023, Volume 44 Issue 8

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2023, 44(8):  0. 

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Contents

Contents

2023, 44(8):  1. 

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UAV Swarm On-line Mission Planning Method Based on Dynamic Allocation Strategy

WANG Mengyang, ZHANG Dong, TANG Shuo, XU Bin, ZHAO Junmin

2023, 44(8):  2207-2223.  doi:10.12382/bgxb.2022.0247

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A distributed online mission planning method based on a dynamic alliance strategy is proposed to deal withthe complex problems of high dynamics, strong uncertainty, and multiple constraints of UAV swarm mission planning in a complex battlefield environment. Firstly, the typical scenarios of UAV swarm dynamic mission planning are described, and the mathematical model of multi-constraint distributed mission planning ofthe heterogeneous UAV swarm is established. Secondly, a task alliance formation strategy considering the dynamic topological constraints of the UAV swarm is designed, and an improved ant colony algorithm coupled with Dubins path planning is proposed to realize the online solution of dynamic mission planning with multiple constraints and strong uncertainties. Finally, typical task simulation scenarios of theheterogeneous UAV swarm is constructed, and the effectiveness of the proposed strategy and algorithm is verified by digital simulations and virtual-real semi-physical simulations.The results show that the proposed method can achieve better system performance with less loss of mission completion time in the dynamic mission planning process, which is of some significance for further research work towards engineering applications.

Improved Particle Swarm Optimization Algorithm for Cooperative Task Assignment of Multiple vehicles

WANG Lei, XU Chao, LI Miao, ZHAO Huiwu

2023, 44(8):  2224-2232.  doi:10.12382/bgxb.2022.0968

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An improved particle swarm optimization (PSO) algorithm for multi-aircraft cooperative task assignment is proposed. The corresponding mathematical model is developed by considering the constraints of the aircraft’s capability, the threat cost, the range cost, and the benefits obtained by completing the tasks. The position attribute of particles is encoded as a set of task assignment vectors, from which we can decode the task assignment solution such that the PSO solution is discretized. In order to solve the problem that the PSO algorithm can easily fall into local convergence, a strategy of jumping out of the local convergence is proposed. Based on the simulated annealing algorithm, this strategy first generates new particles, and then decides whether to retain the new particles with a certain probability. Finally, this jumping-out strategy is applied to the conventional PSO algorithm so as to establish an improved one that can be used for multi-aircraft cooperative task assignment. The digital simulation results verify the effectiveness of the proposed algorithm.

Weapon-target Assignment and Guidance Sequence Optimization in Air-to-Ground Multi-target Attack

ZHANG An, XU Shuangfei, BI Wenhao, XU Han

2023, 44(8):  2233-2244.  doi:10.12382/bgxb.2022.0326

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Weapon-target assignment (WTA) and relay guidance of air-to-ground missiles are difficult problems to be solved urgently in long-range air-to-ground multi-target attack, and are characterized by complex parameters, multiple constraints, and strong nonlinearity. A multi-target and multi-constraint optimization model of WTA and guidance sequence is established, in which the objective includes the minimum comprehensive survival probability of targets and the minimum number of used missiles, and the constraints involve missile configuration of the attack aircraft, damage capability of the missiles, damage requirements of the targets, performance of the guidance stations, etc. A double sequence coding multi-population non-dominated sorting genetic algorithm Ⅱ (DSMPNSGA-Ⅱ) is proposed by improving NSGA-Ⅱ, which optimizes the scheme of WTA and every missile’s guidance sequence through optimizing the WTA sequence and guidance stations sequence. In DSMPNSGA-Ⅱ, the depth-first search Dijkstra (DFS-DJ) algorithm is used to search for missiles’ guidance sequences and improve crossover and mutation operations so as to reduce the production of infeasible solutions, and the multi-population strategy is introduced to improve the performance of DSMPNSGA-Ⅱ. The simulation results show that the DSMPNSGA-Ⅱ can obtain effective schemes of WTA and air-to-ground missile relay guidance, and that its solution quality is better than that of the single-population NSGA-Ⅱ and the multi-objective discrete particle swarm optimization (MODPSO) algorithm.

Study on Multibody Dynamics Modeling and Flight Dynamic Characteristics of Combined Aircraft

DU Wanshan, ZHOU Zhou, BAI Yu, ZHANG Zhilin, WANG Keilei

2023, 44(8):  2245-2262.  doi:10.12382/bgxb.2022.0282

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To precisely and completely describe the location and shape of the combined multibody aircraft, a dynamic modeling method of the 8 DOF combined three-body aircraft reflecting relative rolling motion is proposed using Lagrange’s equations with quasi-coordinates. The aerodynamic database of the combined multibody aircraft system considering the aerodynamic coupling effect is established by the CFD method. The accuracy of the model is verified by comparing the model with ADAMS software through a numerical example. Based on this, the trim scheme and flight dynamic characteristics of the aircraft in different trim states are studied. The stability augmentation control is studied based on the cascade PID control method. The results show that the established model effectively reflects the relative motion of the combined aircraft. With the given trim scheme and flight condition, the aircraft of this configuration has two trim states of "symmetrical lower inverse" and "symmetrical upper inverse", and the static stability of relative rolling motion in the two states is quite different. In addition to the traditional flight mechanics mode, there are 4 new motion modes dominated by relative rolling motion, which can be divided into composite symmetric motion and composite antisymmetric motion according to the motion characteristics. To address the problem that the aircraft with this configuration cannot keep stable flight for a long time without control, the stability augmentation control scheme is reasonable and effective, which can quickly stabilize the divergent flight mechanics system. The proposed modeling method and stabilization control scheme can provide guidance and reference for the design and analysis of multibody aircrafts.

Behaviors of Metal-based Reactive Fragments Penetrating Spaced Aluminum Targets

ZHOU Sheng, ZHANG Jiahao, YU Qingbo

2023, 44(8):  2263-2272.  doi:10.12382/bgxb.2022.0232

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Ballistic impact experiments are conducted on metal-based reactive fragments impacting spaced targets to investigate the post-target debris cloud and damage effect behaviors of the reactive fragments, and to reveal the mechanism of their penetration. By observing the perforation mode of spaced target and the action behavior of fragments, we combine the breakage theory of target penetration, energy conservation law, and the reactivation response behaviors of reactive fragments to analyze and discuss the behaviors of reactive fragments penetrating spacer aluminum targets. The results show that the front target is plugging, and the rear target mainly presents the composite mode of center penetration and debris impact due to the kinetic energy-chemical energy coupling damage of post-target debris cloud. With increasing impact velocity, the reactive of reactive fragments increases. The theoretical model of the reactive fragments’ post-target debris cloud is established, and the evolution law of debris cloud is obtained. At different impact velocities, the unit debris kinetic energy is negatively correlated with unit reaction mass at the position of the critical through aperture.

Combined Damage Behavior of Penetration and Blast of Reactive/Metal Tandem EFPs

ZHENG Yuanfeng, WANG Shipeng, LI Peiliang, ZHANG Yong, GE Chao

2023, 44(8):  2273-2282.  doi:10.12382/bgxb.2022.0356

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In order to improve the comprehensive damage effects of the explosively formed projectile (EFP) to the target, a shaped charge structure with reactive/metal composite spherical liners is proposed. The composite liners include an inner copper liner and an outer reactive liner, and the outer reactive liner is prepared by PTFE/Al energetic powder with a mass ratio of 73.5%/26.5% through cold pressing and sintering processes. The combined damage behavior of penetration and blast of the reactive/metal tandem EFPs for the spaced target plates is investigated by static explosion experiments. The results show that the reactive/metal tandem EFPs not only have an effective penetration effect on the spaced target plates, but also generate detonation-like reaction among the plates, improving the damage effects on the target plates. The number of penetrated layers and perforation diameter of the plates damaged by the reactive/metal tandem EFPs are significantly influenced by the plate thickness. As the thickness of the first two layers of the spaced target plates increases from 10mm to 20mm, the total number of penetrated layers decreases from 6 to 3, and the perforation diameter also significantly reduces. By adopting the SPH algorithm, the numerical simulation reveals that the reactive/metal composite liners form a composite penetrator with a copper EFP in front and a reactive EFP partially embedded in the precursor copper EFP. Then, through the introduction of reaction delay time and material model transformation, the numerical simulations further reveal that the detonation-like reaction of the trailing reactive EFP results in the expansion of the precursor metal EFP, leading to the increase of the perforation diameter and the decrease of the penetration capability.

Experimental and Simulation Study on Vehicle Manned Airdrop

LIU Tao, ZHANG Hongwei, SUN Xiaowang, WANG Xianhui, ZHANG Jincheng, HU Yang

2023, 44(8):  2283-2298.  doi:10.12382/bgxb.2022.0331

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With the development of modern war mode, manned airdrop technology has attracted more and more attention. The safety protection of passengers under airdrop load is one of the core problems of manned airdrop. To this end, the vehicle manned airdrop test is carried out to test vehicle structural response and occupant injury response. The finite element models of the whole vehicle and the occupant restraint system are established, and the simulation method of the vehicle acceleration boundary applied to the occupant restraint system is used to conduct the vehicle manned airborne simulation. By combining the test and simulation results, the dynamic response characteristics of vehicle structure and the rule of occupant injury under airdrop impact are studied. To investigate the four structural parameters of touchdown speed, suspension spring stiffness, damping parameters and cushion parameters, taking the occupant’s lower tibial force, pelvic acceleration and dynamic response index (DRI) as indexes, the single factor simulation analysis and orthogonal experimental simulation analysis are carried out, and the influence laws of four structural parameters on occupant injury under airdrop impact are studied. The results show that the proposed simulation method can better reflect the vehicle’s structural response and occupant damage response under airdrop impact. Under airdrop impact, the vulnerable parts of occupants are mainly lower limbs, pelvis and lumbar spine. The lower limb damage is mainly caused by the direct impact of the floor, and the pelvis and lumbar spine damage is caused by the impact transmitted to the upper body of occupants through the body-column-seat. The effect of touchdown speed on occupant injury is the most significant. The stiffness, damping and cushion hardness of the suspension spring also affect the degree of occupant injury to some extent.

Data-Driven-Based Impact Time Control Guidance Law Independent of Time-to-Go

HUANG Jia, CHANG Sijiang, CHEN Qi, ZHANG Haiyang

2023, 44(8):  2299-2309.  doi:10.12382/bgxb.2022.0324

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To solve the problem of missile impact time control, a two-stage impact time control guidance law is designed based on proportional navigation guidance and the data-driven method, which is independent of time-to-go information. The first stage is the impact time control stage. The relationship data set between the flight path angle and the flight state of the missile is constructed by simulation under the framework of proportional navigation guidance method, and then the corresponding mapping network model is trained offline by using the neural network method. According to the mapping network, the ideal flight path angle corresponding to the impact time can be calculated in real time during missile flight, and the guidance command will control the actual flight path angle converging to the ideal one. In the second stage, the proportional navigation guidance law is directly applied, and the missile impact time control is finally realized. The simulation results under different conditions verify the feasibility and effectiveness of the proposed guidance law. Compared with the existing similar guidance laws, the proposed one can control the impact time with higher precision and less control energy. In addition, the theoretical analysis shows that the guidance law can be extended to impact angle control by changing the mapping network.

Radar Signal Modulation Type Recognition Based on Attention Mechanism Enhanced Residual Networks

WU Liyang, GUO Pengcheng, LIU Chao, LI Wenqiang

2023, 44(8):  2310-2318.  doi:10.12382/bgxb.2022.0302

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To solve the problem of low recognition rate of radar signal modulation type under the condition of low SNR in intelligence analysis, an radar signal modulation type recognition method based on attention mechanism enhanced residual networks is proposed. Firstly, drawing on the strong energy aggregation characteristics of the smooth pseudo Wigner-Ville distribution time-frequency transform, the signal modulation type is transformed into a two-dimensional time-frequency image. Then, residual networks composed of a two-layer convolution network and a six-layer residual block are built, and the convolutional block attention module is inserted between the networks to enhance the attention to features and improve the effectiveness of feature extraction. Finally, two-dimensional time-frequency images are input into the network model to realize modulation type recognition. The simulation results show that this method can effectively extract the feature of time-frequency images for six typical radar signal modulation types, and can achieve 100% accuracy above 0dB Signal-Noise Ratio, and still maintain 94.2% accuracy under -10dB Signal-Noise Ratio.

Newly Equipped Armored Vehicle Classification Based on Integrated Transfer Learning

LIU Yi, REN Jihuan, WU Xiang, BO Yuming

2023, 44(8):  2319-2328.  doi:10.12382/bgxb.2022.0412

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In complicated land warfare environments, image classification techniques is an important tool to quickly distinguish armored vehicle targets. To address the problem that the existing mainstream classification algorithms based on Convolutional Neural Network (CNN) have high requirements for the number and quality of training samples and perform with insufficient accuracy in the image classification task of newly equipped armored vehicles, a transfer learning method that integrates two CNNs based on different learning strategies is proposed. Specifically, one CNN is pre-trained on an old-fashioned armored vehicle image dataset whose samples can be easily obtained and have sufficient quantity to learn local detail features. The other CNN is pre-trained on the dataset of virtual images of the newly equipped armored vehicles with a low image quality to learn the global features. The pre-trained CNNs are all fine-tuned according to different strategies using a limited number of real samples of newly equipped armored vehicles to improve the characterization capability. A self-learning model integration mechanism based on the Optuna hyperparametric optimization framework is designed, which can autonomously weight the outputs of the two CNNs for optimization and further improve the classification accuracy of the algorithm. The experimental results show that the accuracy of the proposed algorithm is improved by 7% in the image classification task of newly equipped armored vehicles compared with the same model trained from scratch, which effectively alleviates the problem of insufficient training samples.

Nonlinear Region of Attraction Estimation for Projectile’s Angular Motion

LI Dongyang, CHANG Sijiang, WANG Zhongyuan

2023, 44(8):  2329-2341.  doi:10.12382/bgxb.2022.0417

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This paper explores the application of the Sum of Squares Programming (SOSP) in the nonlinear region of attraction estimation for projectiles. Considering quantic static moment, the nonlinear planar angular motion for an unguided fin-stabilized projectile is expressed in polynomials and its region of attraction is estimated using Lyapunov functions and V-s iterative algorithm, leading to an accurate estimation. Considering the nonlinear items of normal force coefficient, pitching moment coefficient, equatorial damping moment coefficient, and Magnus moment coefficient, the nonlinear region of attraction of the spacial angular motion of a terminal trajectory corrected mortar projectile with impulses is also studied. Thus, the effective combination of impulse parameters (impulse magnitude and axial acting position) is obtained and then a method for designing impulse parameters is proposed. The findings show that the estimation of the nonlinear region of attraction for projectile’s angular motion obtained by SOSP is of relatively high accuracy. It is feasible and effective to apply the estimation to projectile design.

Adaptive 3-Dimensional Differential Game Guidance for Hypersonic Attack and Defense

WANG Ziyao, TANG Shengjing, GUO Jie, YAN Honglei, GE Jianhao

2023, 44(8):  2342-2353.  doi:10.12382/bgxb.2022.0425

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A 3-dimensional (3D) differential game guidance law based on adaptive dynamic programming (ADP) is proposed to solve the attack and defense problem in hypersonic interceptors attacking hypersonic maneuvering targets. Firstly, the 3D guidance problem in hypersonic attack and defense game is decomposed into the longitudinal plane and lateral plane. Then, the problem model of a hypersonic two-person zero-sum differential game is established in the longitudinal plane. A non-quadratic cost function is designed to satisfy the control constraints. The optimal differential game strategy of the hypersonic interceptor and the target is obtained by the Hamilton-Jacobi-Isaacs (HJI) equation. Since the HJI equation can not be solved analytically, the ADP method is used and a critic neural network is introduced to approximate the optimal cost function to obtain the bank angle amplitudes of both sides. Finally, the lateral guidance is realized by establishing the bank angle reversal logic in the lateral plane by the parallel approach. The simulation results show that the guidance law can achieve precision strike by a hypersonic interceptor under the condition of a maneuvering hypersonic target avoiding interception within the control constraints of both sides of the attack and defense game.

Design of Access Scheme for Detection Swarm for Satellites in HEO

TONG Xin, LI Xu, LIU Yin

2023, 44(8):  2354-2367.  doi:10.12382/bgxb.2022.0354

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Using satellites in high earth orbit (HEO) to return swarm detection data to gain decision-making advantages is indispensable in modern warfare. The access delay needs to be shortened to realize the real-time transmission of detection data. To deal with the scenario of large swarm size and long and intermittent communication links of satellites in HEO, we propose a formation maintenance information based non-orthogonal multiple access (FMI-NOMA) mechanism to solve the problem that the existing mechanism needs retransmission in the case of large single access delay. FMI-NOMA mechanism utilizes the interaction between nodes and uses an election algorithm to aggregate information so that only part of the nodes are allowed to attempt access at a time. Moreover, this mechanism combines the power domain non-orthogonal method to improve the probability of successful node access and avoid repeated attempted access, so that the access performance and system resource efficiency can be further increased. We model the service delay and resource efficiency and establish the optimization model of resource efficiency to analyze the key factors affecting the performance of the proposed mechanism considering the number of swarm nodes, the outage probability between the formation nodes, and the outage probability of satellite-ground links and other factors. The simulation results show that the mechanism improves the resource efficiency by about 45% and reduces the access delay by about 12% compared with the CRDSA mechanism and the improved CRDSA3 mechanism in the literature which has advantages in the HEO satellite communication systems with expanding formation scale and intermittent satellite-ground links.

Effect of Cavitation Micro-jet in Interelectrode Gap on Material Erosion in Ultrasonic Assisted Electrochemical Micromachining

WANG Minghuan, LÜ Ming, HE Kailei, ZHENG Jinsong, XU Xuefeng

2023, 44(8):  2368-2380.  doi:10.12382/bgxb.2022.0318

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A fluid-structure coupling model of themicro-jet impactingthe workpiece surface is established to investigate the effect of cavitation micro-jet generated in the interelectrode gap in ultrasonic assisted electrochemical micromachining (UAEMM) on material erosion. The micro-plastic deformation of theworkpiece surface impacted by the high-speed micro-jet and the influence of micro-deformation on electric field distribution are studied through numerical simulations, and verified by ultrasonic cavitation experiments. The results show that several corrosion pits with adepth of about 0.12μm and a bulge of about 0.04μm are generated on the workpiece surface after the micro-jetimpact. Under the influence of an external electric field, the current density and erosion depth of the bulge of the corrosion pit are 1.2 times higher than that of the original workpiece surface. Furthermore,compared with electrochemical micromachining (EMM), the experimental results of pit forming processing in UAEMM reveal that the removal depth of the pit is increased from 20μm to 100μm and that the surface roughness of the pit bottom is reduced from R_a 290nm to R_a 40nm at the conditions of 10μm ultrasonic amplitude, 5s processing time and 50μm interelectrode gap. A large number of cavitation micro-jets inthe gap under ultrasonic energy can improve the machining efficiency and surface quality in EMM.

Theoretical Model of Oblique Penetration of Rigid Projectiles into Concrete Targets at Attack Angles

LIU Hongfu, HUANG Fenglei, BAI Zhiling, DUAN Zhuoping

2023, 44(8):  2381-2390.  doi:10.12382/bgxb.2022.0423

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To facilitate the pre-estimation of the trajectory and attitude of rigid projectiles obliquely penetrating into concrete targets at attack angles, an theoretical model of rigid projectiles obliquely penetrating into concrete targets at attack angles is proposed to predicate the influence of attack angle on the motion state of projectiles. This paper offers a new method for calculating the projectile load at the cratering stage by its surface stress distribution, and subdivides the cratering stage into the entering stage of the projectile nose and the remaining stage after the full entry as it is considered that the attack angle has most obvious effects at the cratering stage. Moreover, the influence of free surface effect and contact area change on the stress of the projectile body is considered in the cratering model. Then the tunnel and shear plugging model in the theoretical model of attitude deflection is used to predict the whole process of a rigid projectile obliquely penetrating into a concrete target at an attack angle. The computational results of the motion state of the projectile under different penetration situations are proved to be in good agreement with the experimental data. Moreover, the results show that at an oblique angle, the positive attack angle will aggravate the deflection and reduce the penetration ability, while the negative attack angle will inhibit the deflection and the penetration ability can be improved when the negative attack angle is in the right range.

Recognition Method of Target and Sweep Jamming Signal for FM Radio Fuze Based on BAS-BPNN

LIU Bing, HAO Xinhong, ZHOU Wen, YANG Jin

2023, 44(8):  2391-2403.  doi:10.12382/bgxb.2022.0248

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In order to solve the problem that the FM radio fuze is unable to counter AM frequency sweep jamming signals on battlefield in a complex electromagnetic environment, a target recognition method based on frequency domain information entropy, norm entropy and cepstrum entropy is proposed. Based on the output signal of the FM radio fuze under the action of the target and AM frequency sweep jamming signal, the frequency information entropy,norm entropy and cepstrum entropy are extracted to construct the feature matrix. The BAS algorithm is used to optimize the initial weight values and threshold of the back propagation neural network (BPNN). Then the optimized BPNN is used to classify and recognize the target and AM frequency sweep jamming signal. The experimental results with the measured data show that the feature matrix formed by feature extraction has separability between the target and the jamming signal. When the BPNN with optimal parameters is obtained by the optimization of the BAS algorithm, the recognition accuracy of the classifier can reach 99.96%, which significantly improves the ability of the FM radio fuze to counter AM frequency sweep jamming signals.

Control Mechanism of Vortex Generator to the Flow Noise of Wing-plate Junction

LI Dingyuan, FANG Bin, LI Yiming, LIU Wenxi

2023, 44(8):  2404-2413.  doi:10.12382/bgxb.2022.0389

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To solve the problem of flow noise control in wing-plate junction, seven kinds of vortex generators with different heights and spacings were designed, and the noise reduction effect was studied by combining numerical simulation and experiment. Since it is very difficult to directly carry out the vortex generator noise reduction test and verification in water, numerical simulation and experimental verification in the air were firstly selected to analyze and confirm the feasibility of the vortex generator scheme. Taking SUBOFF model as the research object, the numerical method of large eddy simulation was used to solve the acoustic analogy equation with the result of unsteady flow as the sound source term, and the flow noise result was obtained. Through the comparison of different vortex generator schemes, the control effect of two main parameters, the height and spacing of vortex generators, on the main source of the wing-plate junction flow noise, namely, horseshoe vortex, was analyzed. Then the vortex generator scheme with the best noise reduction effect for SUBOFF model was identified. This was verified by the anechoic wind tunnel model test. It is proved that the proposed vortex generator scheme is feasible to reduce the flow noise in wing-plate junction, which lays a foundation for further investigation in the water.

Method for Evaluating Tank Gunner’s Sight System

XIE Baoqi, LI Yingshun, WANG Debiao, SUI Huanhuan

2023, 44(8):  2414-2423.  doi:10.12382/bgxb.2022.0291

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Aiming at the limitations of single signal threshold determination, the determination of the weights of indicators at all levels and the determination of the evaluation results in the health status assessment of the tank gunner’s scope system, a tank gunner’s scope system based on an improved evaluation cloud is proposed. First, the weights of the signal indicators of each layer of the system are calculated by the combination of subjective and objective weights combining the improved fuzzy analytic hierarchy process and the improved entropy weighting method. Then, self-organizing mapping neural network (SOM) is used to determine the index threshold and the cloud interval. Finally, according to the comprehensive weights and the improved cloud model, a state evaluation model is established. Through an example, we demonstrate that the evaluation model is reasonable and effective, yielding results consistent with the actual system state. This approach contributes to the innovation of the health management of the gunner’s sight system.

Analysis of Acoustic Scattering Characteristics of Underwater Targets Based on Kirchhoff Approximation and Curved Triangular Mesh

XUE Yaqiang, PENG Zilong, YU Qiang, ZHANG Chunyu, ZHOU Fulin, LIU Jinwei

2023, 44(8):  2424-2431.  doi:10.12382/bgxb.2022.0374

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For the fast prediction of echo characteristics of unerwater complex targets, the Kirchhoff approximation and curved triangular mesh are employed to build the acoustic scattering model of underwater targets. The target surface is discretized into the curved triangular mesh, and the Gauss-Legendre quadrature method is used to directly calculate the scattering acoustic fields over curved elements in the bright areas. The sum of these scattering fields is the total scattering acoustic field of the target. Four typical targets, namely, rigid sphere, finite elliptical cylinder, cylinder with a hemispherical cap and scaled Benchmark model are considered, and the reliability of the curved element method for calculating target strength is verified by comparing with the planar element method using flat triangular element and experimental measurement. The numerical examples indicate that this method has good accuracy and high computational efficiency.

Correction Method of Mechanical Backlash Error in Ultrasonic Testing of Curved Components

ZHANG Rongfan, NI Peijun, GUO Zhimin, YANG Zhuolin, FU Kang

2023, 44(8):  2432-2440.  doi:10.12382/bgxb.2022.0239

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In the process of automatic ultrasonic detection of complex surface components, the backlash error of each axis of the mechanical system has an badly impact on the probe pose accuracy, image quality and detection sensitivity. In order to solve this problem, the method of identifying and correcting the backlash error is studied in this paper, and a method of measuring the backlash error based on the analysis of the misalignment of C-scan images is proposed. When C-scan imaging of the boundary lines of planar and bar specimens using single axis motion as the main motion, the relationship between the backlash error values of each axis and the amount of misalignment sawtooth in the C-scan image is established. The method of correcting the scanning point joint variables and probe posture using inverse kinematics solutions is studied. The effectiveness of this method is verified through comparative scanning experiments before and after path correction on a certain type of complex surface component test block in terms of imaging quality, element misalignment, and detection sensitivity.

Influence of Stiffened Structure of Steel Plate on the Hypervelocity Penetration Ability of Cylindrical Projectile

MA Kun, LI Mingrui, CHEN Chunlin, YIN Lixin, FENG Na, SHEN Zikai

2023, 44(8):  2441-2452.  doi:10.12382/bgxb.2022.0420

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In order to further study the influence of stiffened structure on the penetration ability of the projectile based on the problem of cylindrical projectile impacting the target plate at hypervelocity. In numerical simulations, the GRAY solid-liquid phase equation of state model, the JC strength model and the JC failure model are collectively taken as the metal constitutive model. The typical problems are calculated by the smooth particle hydrodynamics method. In the experiment, the single-layer stiffened steel plate and the three-layer stiffened steel plate are impacted by the cylindrical projectile at hypervelocity. Combined with the simulation and experimental results, the physical mechanism of the cylindrical projectile impacting the stiffened structure at hypervelocity is analyzed. The influence of the oblique angle, the attack angle, the type of stiffener, the radio of the projectile diameter and the stiffener thickness on the penetration ability of the cylindrical projectile is investigated. The lateral displacement of the trajectory of the cylindrical projectile as it impacts the stiffened steel plates at hypervelocity is analyzed. The results show that: in the case of symmetric impact, adding a main stiffener or auxiliary stiffener in the vertical direction on the basis of the single main stiffener has little effect on the erosion length of the projectile, and the radio of projectile erosion length to stiffener width decreases exponentially with the increase of the ratio of projectile diameter to stiffener thickness; in the case of asymmetric impact, the large angle between the axis of the projectile and the middle plane of the main stiffener is the main reason for the obvious attitude change of the projectile and even the fracture of the projectile, and the lateral motion velocity of the remaining projectile is small relative to the residual velocity in the impact direction; in the case of the projectile impacting the three-layer stiffened steel plate at hypervelocity, when the ratio of the main stiffener boundary far from the projectile axis to the projectile boundary relative to the projectile axis is within 0.6, the projectile can still maintain a good penetration ability. The penetration trajectory will not deviate greatly even if the projectile has an initial lateral displacement relative to the main stiffener.

A Fuze Burst Point Detection Method for Outfield Test Images

ZHOU Yu, CAO Ronggang, LI Ping, MA Xiao

2023, 44(8):  2453-2464.  doi:10.12382/bgxb.2022.0300

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In the anti-jamming performance test of radio proximity fuzes, the observation and recognition of the burst point state is essential for working state evaluation and performance improvement of the fuzes. Therefore, an image target detection algorithm based on the deep neural network is proposed for fuze burst point recognition. The algorithm achieves the following novel designs in the structure and training strategy of the model: The model realizes the target feature extraction based on the high-performance backbone ConvNeXt, and uses the cross stage partial structure based on dense connection and the multi-branch structure with channel attention to improve the feature extraction capability; it also applies a task-decoupled multi-detector structure to improve detection accuracy; focus loss functions are used as the loss functions of classification and confidence, and the complete intersection over union loss function is used as the loss function of prediction box regression in the model training. The proposed algorithm achieves an average precision of 92.7% and F1-score of 87.4% on the real fuze burst point image dataset. The results show the superiority of the proposed algorithm over the existing typical models in the fuze burst point detection task.

Design of Trailing Edge of a Rigid-flexible Chord-Wise Variable Camber Wing

XIN Tao, LI Bin

2023, 44(8):  2465-2476.  doi:10.12382/bgxb.2022.0301

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In order to realize the continuously chord-wise camber change of a wing under driving control, with material deformation ability considered,, an airfoil with hybrid (rigid-flexible) variable trailing edge is proposed. Through the geometric analysis of the mean camber line of the trailing edge, the parametric model of variable camber configuration is established. Taking lift-drag ratio as the optimization objective, the optimal bending angle of the rigid section and the optimal curve of the flexible section are calculated. The lift coefficient, lift-drag ratio and other aerodynamic characteristics of the rigid-flexible airfoil and traditional rigid airfoil are compared at different angles of attack by CFD calculation. When the lift required by the unit span during cruise is taken as the optimization objective, the bending angles and deformation modes of two different trailing edge airfoils are solved respectively in low-speed cruise condition and landing condition. The pressure distribution, velocity distribution and separation position of the two bending forms are compared. A wing model with rigid-flexible variable trailing edge based on the optimized configuration is fabricated and the deformation capability testing is conducted. The results show that: the rigid-flexible trailing edge airfoil has higher lift coefficient, lift-drag ratio and better aerodynamic characteristics in same deflection angle; in the same flight condition, the rigid-flexible trailing edge airfoil has a smaller deflection angle and a more backward separation point, so it has a higher aerodynamic efficiency. The rationality of the flexible wing rib structure and skin design has been verified through deformation capability testing.

Research on a High-Precision Pointing System with Single-Stage Control

DU Yonggang, WANG Xuesong, WANG Yuling

2023, 44(8):  2477-2485.  doi:10.12382/bgxb.2022.0292

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Achieving high-pointing accuracy is a primary technical challenge for a single-stage control pointing system. Eliminating the position-floating link of the pointing mechanism can significantly enhance pointing accuracy. A pointing system is proposed in the paper, which uses an RPS-SPS parallel mechanism without the floating position. The transmission theory and error elimination algorithm of this pointing mechanism validate its efficacy. A prototype is built and tested, and the test results show that the uniaxial error of the prototype is not greater than 0.004 °, the synthetic pointing error is not greater than 0.006 °, and the stability time is not greater than 100 ms both under loaded and no-loaded conditions. The prototype has the pointing function in two axes, with a working space of ±9 ° in both axes. The theoretical model and test results confirm the feasibility and effectiveness of the system. The research lays a foundation for the engineering application of a high-precision pointing system with single-stage control.

Radio Direction Finding System Based on Polynomial Manifold Interpolation

LI Si, LIU Yinsheng, LI Xu, YANG Mingqiang

2023, 44(8):  2486-2494.  doi:10.12382/bgxb.2022.0320

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An anti-mutual coupling radio direction finding system based on the polynomial manifold interpolation algorithm is proposed, which aims to solve the deterioration of DOA estimation performance caused by mutual coupling. Based on the polynomial manifold interpolation DOA estimation algorithm, the system can effectively resist the mutual coupling effect and realize high-precision DF processing under small manifold samples. In the DOA estimation solution of the algorithm, the analytical formula can be obtained by the processing method of multiple precision interval successive approximation search, which avoids exhaustive search in the direction angle domain. On the basis of algorithm theory analysis and simulation, the prototype of the radio direction finding system based on the embedded processor is designed and tested. The test results show that the proposed system can effectively perform DOA estimation in mutual coupling and realize the real-time and reliable direction finding of LTE downlink signals.

Compensation Method for Range-Gated 3D Imaging Inhomogeneity Based on ICCD Detector

SUN Lei, JIN Dongdong, JI Chunheng, PEI Chonglei, AN Hongbo, DUAN Enyue

2023, 44(8):  2495-2502.  doi:10.12382/bgxb.2022.0219

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Range-gated 3D imaging is a non-scanning technology that utilizes nanosecond shutter time characteristics of Intensified CCD (ICCD) detectors to achieve photon time-of-flight gated imaging. It finds valuable applications in long-distance surveying, underwater measurement, and target recognition in complex environments. Due to device technology limitations, there is often a phenomenon of asynchronous switching time in the actual ICCD detector shutter, resulting in serious inaccuracies in range-gated 3D imaging measurements. Based on the inherent gate opening time characteristics of ICCD detectors, a distance error matrix of different devices is obtained through testing, and a range-gated 3D imaging non-uniformity compensation method is proposed. The research results indicate that the proposed method can effectively reduce range-gated 3D imaging errors, improve the actual measurement accuracy, and have good engineering application value.

GA-PS Based Three-dimensional Space Source Inversion Algorithm

CHEN Song, ZHU Dongsheng, ZUO Qinwen, HAN Chaoshuai

2023, 44(8):  2503-2520.  doi:10.12382/bgxb.2022.0272

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In response to the current dominance of hazard source location and source intensity inverse calculation in chemical hazards being confined to the two-dimensional plane, this study focuses on high-dimensional source inversion optimization characteristics. To address this limitation, we propose the Modified Genetic Algorithm and Pattern Search algorithm based on Genetic Algorithm-Pattern Search Algorithm, utilizing genetic algorithms for global optimization and leveraging the pattern search algorithm’s local optimization performance. The simulation results show that the algorithm can realize the three-dimensional spatial location of the hazard source and the inverse calculation of the source intensity using the concentration data of hazardous substances from a group of ground or air detectors in the three-dimensional space. Through inverse calculation of the measured data of the SF6 field experiment, it is verified that the algorithm can realize effective inverse calculation of the spatial location and source intensity of the hazard source under stable atmospheric conditions, achieving an inverse calculation accuracy within 30%.

Secure Communication Method Based on Dynamic DNA Coding and VMP-WFRFT

WANG Xikang, MENG Qingwei, XU Hua, QI Zisen, ZHANG Yue

2023, 44(8):  2521-2532.  doi:10.12382/bgxb.2022.0275

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To improve the information transmission security of the physical layer, a secure communication method based on dynamic DNA coding and variable multi-parameter weighted fractional fourier transform (VMP-WFRFT) is proposed. DNA coding is introduced into bit scrambling. To address the hidden security problem of few existing DNA coding rules, a low complexity four-dimensional chaotic sequence is constructed, and the chaotic sequence is used to randomly select the DNA coding and operation rules of the bit matrix. In order to further mask the signal modulation pattern, the multi-parameter weighted-type fractional fourier transform (MP-WFRFT) parameters are dynamically adjusted by chaotic sequence, so that the modulated signal is transformed by VMP-WFRFT to realize the confusion and diffusion of the constellation, which also enhances the anti-scanning capability of the MP-WFRFT parameters. The simulation results show that the method has good key sensitivity and large key space, and can effectively resist exhaustive attacks. Even if the initial value of chaos as the encryption key has only 10^-15 deviations, the bit error rate of the eavesdropper is always maintained at about 0.5.