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    30 October 2023, Volume 44 Issue 10
    Electronic edition of this issue
    Electronic edition of this issue
    2023, 44(10):  0. 
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    Contents
    Contents
    2023, 44(10):  0. 
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    Protection Performance of Typical Explosion-proof Equipment Against TNT Blast Shock Wave
    YANG Lei, LIU Han, HUANG Guangyan, TIAN Xiangpeng
    2023, 44(10):  2871-2884.  doi:10.12382/bgxb.2023.0281
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    Blast shock wave is a strong intermittent load produced by explosive explosion, which is a main harmful factor causing direct damage to human brain, lung and other gas-bearing organs. For an explosion-proof equipment made of two typical materials, the static explosion tests and numerical calculations of various TNT charges were carried out to study the attenuation law of shock wave propagation under three different protection conditions of free air burst (FAB), steel explosion-proof (SEP) and flexible explosion-proof (FEP). The response process and protection mechanism of two typical explosion-proof equipment are analyzed, and the empirical model of weakening the shock wave overpressure peak for the protection of typical equipment is obtained. The research shows that SEP and FEP can significantly reduce the internal blast shock wave load. Compared with FAB at the same location, SEP reduces the peak overpressure of shock wave by 55.4%~66.3%, and FEP reduces the peak overpressure by 57.2%~77.7%. The shock wave protection ability of FEP is obviously higher than that of SEP during over-equivalent explosion. The main protection mechanism of SEP and FEP is diffraction shielding, but the FEP roof increases the time of interaction between the shock wave and the structure, and weakens the intensity of escaping shock wave through the momentum extraction effect of water and the interface reflection of different wave impedances, while the shock wave in SEP escapes quickly after reflectiing through the rigid materials. The average errors of SEP and FEP shock wave peak overpressure attenuation models are 2.4% and 10.2%, respectively. The shock wave weakening law and protection experience model of typical equipment obtained in this paper are expected to provide reference for the design of explosion-proof tank equipment.

    Calculation of System Combat Capability Using an Interactive Network Approach
    CHEN Wenyu, LI Weimin, ZHANG Tao, SHAO Lei, XU Haiyang, WANG Xi
    2023, 44(10):  2885-2896.  doi:10.12382/bgxb.2022.1039
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    Traditional combat network models struggle to reflect interaction dynamics between combat parties and often neglect practical node deletion strategies. Additionally, system capability quantification often relies excessively on the number of kill chains. To address these issues, this paper proposes a system combat capability analysis method based on an interactive adversarial network model. The paper establishes a red-blue interactive network model that incorporates both combat nodes into the network model, and suggests updating both nodes through a reachable node deletion strategy. It introduces the concepts of kill chain capability and system kill chain capability, and quantifies the system combat capability based on the scale of destruction. To account for the complexity of calculating two-terminal connectivity in unequal probability networks, this paper uses Monte Carlo simulation to solve the system kill chain capability. Simulation experiments analyze key variables affecting the system combat capability and validate the analysis with other methods. The results show that the enhancement of the functional capability of the accusation node is the core key of the combat system, which plays an important role in the non-linear enhancement of the combat destruction capability of the own system and the non-linear suppression of the enemy system, and the simulation comparison experiments verify the superiority of the method in this paper.

    Numerical Investigation of Anti-ballistic Property of ZnO-modified Aramid Fabrics
    XU Yaojie, LIU Han, ZHANG Hong, HUANG Guangyan
    2023, 44(10):  2897-2905.  doi:10.12382/bgxb.2022.1297
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    Aramid fabrics are widely used in the field of body armors due to their low density, high modulus and high strength. In order to improve the ballistic resistance of aramid fabrics, the aramid fabrics are modified by planting and growing the nano-ZnO particles. The electron microscope observation, quasi-static tensile test, yarn pull-out test, ballistic impact test and numerical simulation were made for ZnO-modified fabrics, and their mechanical and ballistic properties were studied. The results show that the planting of ZnO particles increases the structural interlock and surface roughness of yarns. Compared with the neat fabrics, the inter-yarn friction coefficient of ZnO-modified fabrics is increased by 282%, their ballistic limit velocity is increased by 54.5%, and their energy absorption and specific energy absorption performance are significantly better than those of neat fabrics. The ballistic impact process of the modified fabric is simulated by the meso-yarn model. The simulated results are in good agreement with the ballistic test results. This further explains that the improvement of inter-yarn friction coefficient and tensile strength is an effective means to enhance the ballistic impact resistance of fabrics, and provides a theoretical basis for the application of ZnO-modified fabrics in the field of flexible bulletproof.

    Effects of Intake Flow Rate on Powder Fluidization and Conveying in a Piston-Type Powder Feeding Device
    REN Guanlong, SUN Haijun, XU Yihua
    2023, 44(10):  2906-2919.  doi:10.12382/bgxb.2022.0582
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    A built-in intake channel powder feeding device is designed for the piston-driven powder fuel supply system, and the action of the multi-physical coupling of the gas-powder-moving wall is established. Numerical simulations are carried out to investigate the variation of intake flow rate on powder fluidization and conveying characteristics using the Eulerian-Eulerian two-fluid model. The results show that gas-solid interface fluctuations mainly occur in the upper part of the intake channel. With an increasing intake flow rate, both the gas phase distribution range and the area covered by the powder layer (Powder volume fraction εp=0.1) increase. The peak granular temperature at different intake flow rates is mainly located near the two-phase throat. The gas-solid two-phase velocity at the head position of the conical convergence section and the two-phase throat increases with increasing intake flow rate, while the area-averaged powder volume fraction decreases. When the mass flow rate ratio is 0.10%, a sudden spurt phenomenon occurs in the outlet powder flow during the late conveying stage, while the pressure in the powder storage tank drops abruptly. When the mass flow rate ratio is 0.33%, the outlet powder flow rate and pressure fluctuations in the powder storage tank are relatively stable. For mass flow rate ratios ranging from 0.56% to 1.25%, both outlet powder flow rate and pressure in the powder storage tank exhibit similar fluctuation patterns, albeit with larger amplitudes. The findings of the study provide a theoretical reference for the development of an efficient powder conveying device.

    Prognosticating Remaining Useful Life of Electro-Mechanical Actuators Using a Multi-mode Transformer Model
    CHEN Zihan
    2023, 44(10):  2920-2931.  doi:10.12382/bgxb.2022.0581
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    Electro-mechanical actuators play an important role in next-generation spacecraft. To address the challenge of predicting the remaining useful life of electro-mechanical actuators, a failure prognostic algorithm based on a multi-mode Transformer model is proposed. Multi-channel sensor data are directly used as inputs to the Transformer model without feature extraction as a pre-processing step. The multi-mode Transformer uses multi-head attention to adaptively learn global features from various representation subspaces. The Encoder of the Transformer is utilized to extract features from different sensors across the time series in parallel and predict the remaining useful life directly. Simultaneously, the full Transformer, composed of an Encoder and a Decoder, is used to prognosticate key performance parameters of electro-mechanical actuators. A benchmark dataset is used to validate the effectiveness of the proposed model for electro-mechanical actuator failure prognostication. Experimental results reveal its advantage in accurate prediction and failure prognosis.

    Constitutive Model and Blast Resistance Test of Concrete under Low/Room Temperature Curing
    NING Jianguo, YANG Shuai, LI Yuhui, XU Xiangzhao
    2023, 44(10):  2932-2943.  doi:10.12382/bgxb.2022.1019
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    The mechanical properties of concrete materials are closely related to the curing environment. Limited by the construction environment, some concrete structures are poured and formed at high altitudes or in cold, low-temperature conditions. In this work, several uniaxial compressive tests are conducted on concrete specimens cured at both low and room temperatures to study their mechanical properties and blast resistance. Based on the results of these tests, the damage evolution function related to the length of curing is introduced, the plastic flow factor is modified and the constitutive model of concrete under low/room temperature curing is established to predict the mechanical properties of concrete. Blast impact tests of concrete are conducted to compare the blast resistance of concrete blocks under low/room temperature curing. The research results show that: the compressive strength of concrete materials under low-temperature curing is about 34.6%~56.8% of that under room temperature curing. Compressive strength is positively correlated with the length of curing and negatively correlated with the internal moisture of the specimens. The mechanical properties of concrete under low/room temperature curing can be effectively predicted by the established concrete constitutive model. The blast resistance of concrete formed by low-temperature curing is reduced, but it still exhibits notable blast resistance capabilities.

    Performance Prediction and Optimization of Ramjet for Projectiles Using Support Vector Regression Model
    ZHANG Ning, SHI Jinguang, WANG Zhongyuan, ZHAO Xinxin
    2023, 44(10):  2944-2953.  doi:10.12382/bgxb.2022.0493
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    To improve the working performance of solid fuel ramjet for projectiles and shorten the optimization period, the transitionshear stress transfer and vortex concept dissipation equations are used to establish an internal ballistic calculation model, and the flow field and performance parameters are obtained. Then, based on the support vector regression method,a prediction model of the performance parameters is built, and the ramjet structure is optimized using the NSGA-Ⅱ algorithm. The results show that the internal ballistic calculation model can simulate the combustion and flow process in the ramjet well. At the same time, the constructed prediction model has high reliability, and the maximum relative error is less than 3% compared with that of the high-confidence model. After the ramjet is optimized, the combustion chamber is shortened by 13.88%, the aft mixing chamber is increased by 13.50%, and the combustion efficiency, thrust and specific impulse are increased by 12.02%,24.22% and 20.28%, respectively.

    Modulation Recognition Algorithm Based on Transfer Meta-Learning
    PANG Yiqiong, XU Hua, ZHANG Yue, ZHU Huali, PENG Xiang
    2023, 44(10):  2954-2963.  doi:10.12382/bgxb.2022.0583
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    For the problem that the modulation recognition algorithm based on deep learning can not be trained when there are only a few labeled signal samples, the model-agnostic meta-learning algorithm is used to improve the generalization performance of the network so that the network can accurately recognize the signals to be recognized with only a few training samples. At the same time, the deep neural network is pre-trained to reduce the training difficulty of the network at the meta learning stage. According to the idea of transfer learning, the amount of network parameters required for learning new class signals is reduced by introducing the learnable scaling offset parameters to migrate the network parameters obtained from the pre training. When facing the recognition task of new class signals, the accurate recognition can be achieved by finely tuning the network through a small number of signal samples. The experimental results show that the algorithm can achieve a recognition accuracy of 93.5% when there are only 5 training samples.

    Fault Diagnosis Method of Modular Charge Feeding Mechanism Based on Transfer Learning
    HUANG Wenkuan, QIAN Linfang, YIN Qiang, LIU Taisu
    2023, 44(10):  2964-2974.  doi:10.12382/bgxb.2022.0767
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    To solve the problem of fault diagnosis of the modular charge feeding mechanism under multiple working conditions, a fault diagnosis method based on transfer learning and singular value decomposition (SVD) was proposed. SVD was used for dimensionality reduction and noise reduction as means of preprocessing of the modular charge velocity data and for feature extraction. The transfer learning method based on the TrAdaBoost algorithm framework was adopted to synthesize limited test data and a large amount of simulation data to extract effective fault information. In the information, multiple base fault classifiers were built and integrated into a high-quality fault classifier. The experimental results showed that the proposed method has good adaptability to the fault data under multiple working conditions, which can obtain better diagnosis accuracy compared to the traditional machine learning strategy in the case of limited test data.

    Projectile Trajectory Prediction Based on CNN-LSTM Model
    ZHENG Zhiwei, GUAN Xueyuan, FU Jian, MA Xunqiong, YIN Shang
    2023, 44(10):  2975-2983.  doi:10.12382/bgxb.2022.0511
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    To solve the problem of nonlinear trajectory prediction of projectile, a novel hybrid trajectory prediction model based on convolutional neural network (CNN) and long and short-term memory (LSTM) neural network is proposed. A 6DOF projectile movement model is established, and a substantial dataset of trajectory samples is obtained through exterior ballistics simulations employing the four-order Runge-Kutta method. Secondly, the hybrid CNN-LSTM trajectory prediction model is proposed, and the input and output trajectory data pairs are constructed by using the sliding window method and first-order difference method, which transforms the prediction problem into a supervised learning problem. Then, the proposed model is compared with LSTM neural network model, gated recurrent unit (GRU) neural network model and back propagation (BP) neural network model using the same dataset. The results show that the average cumulative prediction error of CNN-LSTM model after 3s is about 14.83m in the x-axis direction, 20.77m in the y-axis direction and 0.75m in the z-axis direction. The trajectory prediction accuracy of CNN-LSTM neural network model is better than that of a single model, which provides valuable insights for advancing projectile trajectory prediction research.

    Numerical Investigation of Tail Shape Effects on the Tail-slap of Supercavitating Projectiles
    LIU Rushi, GUO Zeqing, ZHANG Hui
    2023, 44(10):  2984-2994.  doi:10.12382/bgxb.2022.0689
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    Tail-slap motion is vital for maintaining stable navigation of supercavitating projectiles. To study the influence of the tail shape on the motion characteristics of a supercavitating projectile during tail-slap navigation, a three-dimensional free tail-slap motion simulation model is constructed using the finite volume method and Mixture multiphase flow model, as well as dynamic mesh technology. The tail-slap motion characteristics of the four projectiles with different tail shapes(i.e., cylindrical tail projectile, cone tail projectile, fin-stabilized projectile and flare-stabilized projectile) are compared, and the intrinsic motion state characteristics of the projectiles are analyzed with different initial angular velocities. The results show that the tail shape affects the wetting area and the shape of the cavitation it produces. Larger wet surface areas or larger angles between wet surface and projectile velocity direction lead to increased torque and tail beat frequency, along with slower velocity attenuation.Steady navigation velocity attenuation ranking is fin-stabilized > cone tail > cylindrical tail > flare-stabilized projectile. All the four projectiles exhibit an“inherent tail motion state” related to their geometry, independent of initial disturbance angular velocity. In this state, the peak value of angular velocity oscillation decreases with the velocity proportionally.

    Effect of Galvanometer Scanning Speed on Surface Quality and Friction Characteristics of 7075 Aluminum Alloy During Laser Cleaning
    WANG Wei, SHEN Jie, LIU Weijun, XING Fei, ZHANG Kai, LI Qiang, YU Xingfu
    2023, 44(10):  2995-3005.  doi:10.12382/bgxb.2022.0437
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    The laser cleaning experiment of the original oxide film on the surface of 7075 aluminum alloy was carried out by pulsed laser. The effects of galvanometer scanning speed on the surface morphology, oxygen content and phase composition of 7075 aluminum alloy were investigated. The surface roughness and wear resistance of 7075 aluminum alloy were studied by laser confocal microscope and friction and wear tester. The results show that, as the scanning speed of galvanometer increases from 2500mm/s to 4500mm/s, the oxygen content and roughness of the cleaned surface first decrease and then increase. When the scanning speed is 3500mm/s, the surface oxygen content and roughness reach the lowest, which are 1.45% and 0.344μm, respectively. When the scanning speed is 2500mm/s, a serious melting phenomenon appears on the cleaned surface, and the spot pits and corrugated bulges make the cleaned surface roughness increase. When the scanning speed is less than or equal to 3000mm/s, a thermal oxidation occurs on the cleaned surface, and a new oxide film mainly composed of Al2O3 is formed. After laser cleaning, the molten layer with small roughness can improve the antifriction and wear resistance of the cleaned surface. Under the friction load of 10N, a fatigue spalling occurs on the heavily molten cleaned surface during the friction process. The wear mechanism of cleaning surface is mainly abrasive and delamination wears.

    Hierarchical Information Dissemination Method for Unmanned Cluster Targets Allocation
    SHEN Yuting, MENG Xin, GAO Yueqing
    2023, 44(10):  3006-3025.  doi:10.12382/bgxb.2022.0515
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    For the construction of a practical constructing cluster intelligence, the basic associations of individual/group cooperations should be clarified to develop the extensible models and methods. At present,the differentiation models are difficultly coalesced or integrated, leading to the intense demand of taking hold of a common basis for uniting behavior consistency and interaction. Based on the theory of complex network information transmission and community structure, a hierarchical information dissemination method for cluster targets allocation is proposed for the decoupling of decision making and communication. Therefore, from a mesoscale perspective of information interaction control in and among dynamic communities, the UAU-FO* model-based hierarchical information transmission method is proposed on the basis of the double-layer coupling system model. The proposed method can be used to construct the extensible association foundation between the individual targets selection and the emergence of group cooperation, which provides a supportability for realizing the autonomous aggregation and deaggregation oriented to targets attending bythe propagation effect of decision making.The simulated results shows that the groups can achieve self-directed organization through independent information perception fusion, inter-layer control and group control strategies after the decoupling of decision and communication. Simultaneously, it is verified that the method has good robustness and continuous stability under weak interconnection conditions.

    Research and Experiment on the Motion Mechanism of a 3-PRPS/RRR Ankle Rehabilitation Mechanism
    LI Hui, NING Fengping, GUO Hui, LI Ruiqin
    2023, 44(10):  3026-3037.  doi:10.12382/bgxb.2022.0430
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    To design a rational and patient-suited ankle joint rehabilitation mechanism, a novel 3-PRPS/RRR parallel robot is proposed, tailored to the specific characteristics of ankle joint movement. The mathematical model of the mechanism is described using the screw theory, demonstrating its three degrees of freedom. The closed-loop vector method is used to obtain the inverse kinematics of the mechanism, and the particle swarm optimization is used to calculate the forward kinematics. Design parameters are meticulously set, and the workspace of the mechanism is determined by the iterative numerical algorithm based on the initial value. The biomechanical software is used to establish the human musculoskeletal system, and the activation of muscles is simulated when the mechanism is used for ankle rehabilitation training. Finally, an experimental prototype is built to verify the forward and inverse kinematics, workspace and singular configuration of the mechanism. The results show that the CAD model is consistent with the theoretical calculations, thereby validating the accuracy of the forward and inverse kinematics of the mechanism through experiments. The working space of experimental prototype can meet the range of motion required by ankle rehabilitation training, and there is no singular configuration in the working space of the mechanism. This mechanism can effectively activate muscles and achieve the purpose of rehabilitation training.

    Fluid-Structure Interaction Mechanism of Hypersonic Aircraft in Plasma Environment
    WANG Chen, TIAN Zhenguo, SHEN Zhenxing
    2023, 44(10):  3038-3046.  doi:10.12382/bgxb.2022.0477
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    Hypersonic vehicles are in a plasma environment when passing through high-temperature air, different from thermal perfect gas conditions. Accounting for the real gas effect of plasma is crucial for accurately calculate the fluid structure interaction between aircraft and surrounding fluid. In this paper, based on the plasma chemical non-equilibrium hydrodynamic equations, combined with the fluid solid coupling equations, a fluid solid coupling model is established. Taking the RAM-C aircraft as an example, the model is calculated and verified, and the fluid structure interaction mechanism of the aircraft is discussed. The results show that the aerodynamic pressure and aerodynamic viscosity of plasma increase, and the position of the maximum aerodynamic viscosity shifts compared with that of thermal perfect gas. The position of plasma aerodynamic load is favorable for the bluff body to bear, and the maximum fluid solid coupling stress is less than that of thermal perfect gas. The front end of high-speed aircraft mainly bears the fluid solid coupling of atomic gas, while the fluid solid coupling of electrons and ions on the aircraft is very low. The effect of molecular gas on the aircraft is more obvious in the middle and rear parts.

    Automatic Planning of the Shortest Searching Route in Irregular Convex Region for Surface Ship
    ZHOU Yinfei, ZHANG Lihua, JIA Shuaidong, DAI Zeyuan, LIU Xiang
    2023, 44(10):  3047-3055.  doi:10.12382/bgxb.2022.0443
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    Automatic planning of the shortest submarine searching route in the irregular convex area is proposed to solve the issue that the existing surface ship regional submarine searching route planning only focuses on regular rectangular areas neglecting the complexity of irregular areas. For irregular convex polygons, the linear relationship formula between the total length of the searching route and the number of turns is derived. On this basis, the calculation model of the shortest submarine searching route is constructed. Based on the internal correlation law between the optimal submarine searching route course and the boundary of irregular convex region, the algorithm for solving the optimal submarine searching route course is designed. The experimental results show that the method could effectively determine the optimal search direction within the irregular convex areas and subsequently generate, the shortest search path automatically.

    Temperature Field Analysis of Limited Slip Clutch Based on Equivalent Heat Transfer and Dynamic Heat Flux Partition
    JIN Jiaxi, YANG Shujun, PENG Zengxiong, CHEN Qiao’er, LI Xueliang, PAN Hui, LIAN Zhuang
    2023, 44(10):  3056-3066.  doi:10.12382/bgxb.2022.0531
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    This work focuses on the influence of the convective heat transfer and input of heat flux on the nonlinear temperature field of the limited slip clutch in various continuous sliding conditions. Considering that the steady heat flux partition model cannot meet the limitation of the continuous temperature of the contact interface, a new calculation method for equivalent convective heat transfer coefficient is proposed based on the assumption of equivalent oil film of friction gap, and the temperature field prediction model for full lubrication conditions of the limited slip clutch is established during the dynamic distribution of heat flux. The clutch sliding bench is constructed and six experiments of different lubricating oil temperature and relative speed difference is designed. The results show that the established model effectively eliminates the temperature prediction deviation, and the maximum error of temperature prediction is 7.6%, which provides a theoretical basis for the research of clutch temperature field under the dynamic continuous sliding conditions. The variation of clutch temperature rise is divided into rapid growth stage A and stable growth stage B. At stage A, the decrement of heat flux input and the increment of equivalent power of convective heat transfer of the steel are positively correlated with the increase of relative speed difference, and the average temperature rise rate increases along with the heat flux density. The stable equilibrium state of input of heat flux and output of heat transfer is reached during stage B.

    Nonlinear Angular Motionand Bifurcation Characteristics of Canard Dual-Spin Projectiles
    ZHAO Xinxin, SHI Jinguang, WANG Zhongyuan, ZHANG Ning
    2023, 44(10):  3067-3078.  doi:10.12382/bgxb.2022.0426
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    Canard dual-spin projectiles may exhibit a significant angle of attack during flight, challenging the original stability criteria derived under the assumption of small attack angles. Thus, it is difficult to accurately judge the flight stability of projectiles under such conditions. In this paper, the nonlinear angular motion and bifurcation characteristics of such projectiles are studied. An improved six-degree-of-freedom ballistic equation of canard dual-spin projectiles is established with the geometric nonlinearity and aerodynamic nonlinearity considered, and the accurate generalized motion equation of complex attack angle and its corresponding state space model are deduced. Accordingly, numerical methods are used to analyze the influence of different factors on the bifurcation characteristics and limit cycle radius of the system. The results show that the nonlinear of lift and Magnus moment and the flight velocity are the main factors affecting the bifurcation characteristics of the system. The increase of the control force and moment of canards and air density tend to reduce the limit cycle radius. The radius of the limit cycle may be reduced in controlled flight compared with that in uncontrolled flight, but it is approximately independent of the control orientation of the front body roll angle, that is, the change of front body roll angle has little impact on flight stability.

    Design and Verification of Polymorphic Safety Logic Control Method for Cruise Ammunition Fuze Based on Electronic Safety System
    ZHANG Chuanhao, LI Haojie, GONG Xuefeng, CHEN Zhipeng, YU Hang
    2023, 44(10):  3079-3090.  doi:10.12382/bgxb.2022.0522
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    To adapt to the transition of the safety state of the cruising missile ammunition in swarm combat and ensure reliable safety recovery and rearming, a polymorphic safety logic control method is proposed for cruise ammunition fuzes based on an electronic safety system. The decision result is selected as the target-based arming environment, and the input-output relationship between the two FPGAs of the electronic safety system and the polymorphic safety logic control process are determined according to the structure of the electronic safety system. Based on the established deprotection logic, the accidental failure rate of the fuze safety system before launch is analyzed and calculated, meeting the safety criteria. By designing two state machines running inside the FPGA to control the transition of the safety state of the cruise ammunition fuze and achieve polymorphic safety logic control, the feasibility is validated through simulation. Experiment results demonstrate successful realization of the designed safety state transition.

    Model Comparison of Fuel Cavitation Phenomena in Microchannels of Marine Diesel Engines
    LI Ziming, LIU Zhenming, LIU Jingbin, CHEN Ping
    2023, 44(10):  3091-3100.  doi:10.12382/bgxb.2022.0498
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    The fuel injector is the key component of the marine diesel engine, and the diameters of the injector nozzle and the control chamber oil inlet and outlet, which are typical microchannel structures, are generally between 0.2 and 0.5mm. During high pressure injection, the cavitation phenomenon in the channel seriously affects the reliability of diesel engine. The choice of turbulence and cavitation models is the key to study the above cavitation problems using the numerical calculation methods. Based on the Winklhofer microchannel fuel test, three representative turbulence models and two cavitation models were used to construct the microchannel model, and the simulated results were compared and analyzed with the test results. The results show that the pressure gradient values obtained from the two combinations of RNG k-ε+ZGB models and RNG k-ε+SS models are similar to the experimental data with an error of less than 7%; the cavitation distributions calculated by the different model combinations are different; the outlet mass flow rates obtained from Realizable k-ε+ZGB models and RNG k-ε+ZGB models are consistent with the experimental; in the range of pressure difference from 19 bar to 85 bar, and the outlet mass flow rate obtained from the Realizable k-ε+ZGB model and the RNG k-ε+ZGB model matches the trends of the experimental data, and the error is less than 4%. In the caculation of cross-sectional flow rate, the calculated error of RNG k-ε+SS model is minimum with the error of less than 10%.

    Fault Diagnosis for Gun’s Anti-recoil Device Based on Gaussian Model and RMSD-DS
    WEI Jianfeng, ZHANG Faping, LU Jiping, YANG Xiangfei, YANG Pengkai
    2023, 44(10):  3101-3114.  doi:10.12382/bgxb.2022.0635
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    To deal with the problem of low reliability of fault diagnosis caused by the ambiguity and high conflict of the state signal of the anti-recoil device of the gun under variable operating conditions, a fault diagnosis method based on the Gaussian model and RMSD (Root Mean Square Deviation)-DS (Dempster-Shafer) is proposed to realize the quantitative characterization of signal fuzziness and the high reliability diagnosis of high-conflict evidence fusion. This method uses the Gaussian model to solve the basic probability assignment of the evidence corresponding to multiple fault feature signals of the anti-recoil device, thus realizing the quantitative characterization of the signal ambiguity. By constructing the RMSD-DS conflict coefficient to solve the similarity between evidences, the importance of each evidence is defined according to the similarity, and the quantitative description of the importance of each evidence in the fusion process is realized. The weight solution and evidence fusion method based on the importance of evidence are put forward to realize the reliable fusion of highly conflicting evidence. The application of simulation test data shows that the proposed method has higher accuracy and robustness than other representative methods.

    Sand-dust Image Restoration Using Gray Compensation and Feature Fusion
    DING Bosheng, ZHANG Ruiheng, XU Lixin, CHEN Huiming
    2023, 44(10):  3115-3126.  doi:10.12382/bgxb.2022.0510
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    Scattering and absorption of light by dust particles often result in sand-dust images with low contrast and significant color deviations, which can hinder the tracking performance of unmanned aerial vehicles and precision-guided ammunition for target recognition and tracking. Due to the complexity of scene structures, difficult parameter estimation and other factors, the existing sand-dust image restoration methods cannot effectively extract semantic components from images, resulting in unreal colors and blurred details of restored images. To address these issues, a two-stage sand dust image restoration framework consisting of gray compensation-based image pre-processing and feature fusion networks is proposed. The image pre-processing module compensates the gray distribution of the input sand images to recover latent scene information, producing two images with balanced color and clear contours. The fusion network then extracts and fuses high-dimensional features from different derived input images and restores high-quality images. The results show that high index statistics and good visual effects are obtained in the restored images, effectively improving detection and segmentation accuracy of sand-dust images.

    Parameter Estimation of Binary Phase-coded Modulation Radar Waveform Using Non-convex Total Variation Regularization
    PENG Bo, CHEN Qile, LI Rui
    2023, 44(10):  3127-3136.  doi:10.12382/bgxb.2022.0572
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    By estimating and reconstructing the parameters of the captured signal, the DRFM mitigates the effect of noise on jamming performance. This approach, termed reconstruction jamming, relies on accurate parameter estimation of the captured signal. However, traditional time-frequency analysis methods face challenges when dealing with Binary Phase-coded Modulation (BPCM) signals due to their abrupt changes and jump discontinuities. To address this, a novel parameter estimation method for BPCM radar fuses based on non-convex total variation regularization is proposed. First, the center frequency of the captured signal is estimated by interpolation on Fourier coefficients. Then, the captured signal is transformed to zero intermediate frequency, and pseudo codes are estimated using total variation regularization. The jamming signal is a reconstruction of the captured signal. Experimental results verify the effectiveness of the proposed method, showing that its jamming capability against BPCM fuses is significantly lower than the traditional sweep jamming and DRFM-based repeat jamming under SNR=-10dB.

    Pedestrian GNSS/PDR Integrated Navigation System with Graph Optimization
    ZHU Jianliang, WANG Liya, BO Yuming
    2023, 44(10):  3137-3145.  doi:10.12382/bgxb.2022.0557
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    The integration of a navigation system based on the Global Navigation Satellite System (GNSS) and the Pedestrian Dead Reckoning (PDR) with inertial measurement data is a widely used and reliable navigation solution. To further improve the positioning accuracy of the GNSS/PDR integrated navigation system, we propose a GNSS/PDR integrated navigation method based on graph optimization. By constructing a factor graph to represent the probabilistic dependence between states and measurement information, all past states are iteratively estimated at each step as the unknowns, and the optimal estimation of the states is obtained by minimizing the global cost function. Compared with the KF algorithm, this new system can further reduce average positioning error and improve positioning accuracy. Results from two different real scene results show that, compared with KF, the average values of the horizontal positioning errors are reduced by more than 40%, verifying the algorithm’s effectiveness in improving the positioning accuracy.

    Acoustic Scattering Regulation Mechanism of Underwater Metasurface Corner Reflector
    LIU Yan, PENG Zilong, DU Jiaman, KONG Huimin, FAN Jun
    2023, 44(10):  3146-3155.  doi:10.12382/bgxb.2022.0566
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    Corner reflector is a common deception method for radar and sonar targets. To enhance the regulation effect of the scattering sound field of conventional concave angles, the regulation method and calculation method of inlaid acoustic metasurfaces in the underwater corner reflector are proposed. Based on the plate element method and the ray tracing algorithm, the acoustic scattering prediction model of the corner reflector with acoustic metasurface configuration is established. Ray tracing is used to determine the position of the sound ray, and the corresponding phase jump is corrected, which is verified by finite element simulation. Based on the established acoustic scattering prediction model, the regulation effect of the gradient and periodic structure of the groove array on the scattering sound field is studied. It is found that: the acoustic metasurface structure with gradient change can significantly change the acoustic scattering characteristics of underwater targets;the combined positive and negative gradient groove array structure has obvious effect on the main direction of acoustic scattering;the gradient structure of multi-period combined groove array is more effective than the single-period structure in scattering sound field regulation.

    Estimation of Ammunition Hit Probability in Multiple-Batch Tests Using Multinomial Distribution
    LIU Haobang, SHI Xianming, HAO Bing, JIANG Yongchao
    2023, 44(10):  3156-3164.  doi:10.12382/bgxb.2022.0490
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    Ammunition hit probability tests are usually carried out in multiple batches. With each test batch, the physical properties of ammunition evolve, influencing hit probabilities dynamically. Before each batch, simulated ammunition hit probability information is obtained. Effectively utilizing the shooting tests information and simulation data of each batch is key to hit probability estimation. In addition, considering the different degrees of damage caused by ammunition hitting different areas of the target, the original binomial distribution hit probability test is improved and described by multinomial distribution. System contribution is introduced to measure the impact of each batch of tests on the estimation of the ammunition hit probability, and the Bayesian method is used to fuse the test data of each batch. The ammunition hit property improvement is identified by constructing sequence constraint relation. Finally, the estimation of ammunition hit probability in multiple batch tests based on multinomial distribution is proposed. The example shows that the method can describe the hit properties of ammunition in detail compared with the binomial distribution method. It can also scientifically integrate the information of each batch shooting tests and simulation tests, providing reference for the estimation of the hit probability.

    An Infrared Small Target Detection Method via Dual Network Collaboration
    WANG Qiang, WU Letian, LI Hong, WANG Yong, WANG Huan, YANG Wankou
    2023, 44(10):  3165-3176.  doi:10.12382/bgxb.2022.0605
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    Infrared small target detection (ISTD) is a heated topic in infrared image processing, and it is intensively applied in early warning systems and missile guidance. ISTD faces significant challenges such as low signal-to-noise ratio (SNR), small size, lack of distinct shape or structure, and weak texture, making it a demanding task. The performance of conventional object detection networks and semantic segmentation networks considerably deteriorates when applied directly to ISTD tasks. To address this issue, this paper proposes a new dual network collaboration-based image semantic segmentation network for ISTD, termed as DualNet. DualNet divides the task into two sub-tasks, namely reducing missed detections and reducing false alarms, with two sub-networks focusing on their respective targets (with cost reduced) by employing a weighted loss function to integrate sub-network information. DualNet effectively balances the miss detection rate and false alarm rate. Experimental results show that DualNet outperforms general neural network models (e.g. FCN, DeepLabv3, cGAN and U-net) on the ISTD task, with an improved F1-measure by 0.08. Furthermore, our model outperforms ACM and MDvsFA-cGAN, two most representative ISTD models based on deep learning, and several non-deep-learning-based ISTD methods.

    Multi-state System Reliability Analysis for Ship Power Generation System Based on Markov Reward Model
    CHEN Tong, HU Bin, DI Peng
    2023, 44(10):  3177-3186.  doi:10.12382/bgxb.2022.0558
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    A multi-state cold standby power generation system of naval ship is investigated. Considering the influences of scheduled maintenance interval on the system reliability parameters, the state-transitions matrix, reward matrix, reward function and acceptability function of power generation system are designed to analyze the system reliability based on Markov reward model (MRM). When the reasonable values are assigned to the elements of reward matrix, several performance measures of interest, such as the system interval availability, mean operational time, mean down time, mean number of system failures and system reliability in the scheduled maintenance interval, are obtained. Then the validity and applicability of the model are implemented through a numerical application. The influences of scheduled maintenance interval and mean time to repair of single generator unit on system reliability measures are demonstrated. In brief, this research provides a modeling tool for the reliability design of ship power generation systemreliability and the technical support for reasonable arrangement of ship maintenance structure. The whole modeling process shows that MRM can be used to analyze and calculate the reliability of complex multi-state system conveniently.

    Thermal-Mechanical Analysis of the Biaxial Stretch of Aviation Glass
    ZHAO Wenhui, BAI Shihuan, GAO Dayong, LI Xiaowei, DUAN Zhenyun
    2023, 44(10):  3187-3194.  doi:10.12382/bgxb.2022.0459
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    This study focuses on enhancing the quality and success rate of biaxial stretching for aviation glass to meet the stringent requirements of military fighter applications. Based on the thermal mechanical coupling theory of viscoelastic materials, the viscoelastic properties of plexiglass are simulated in the form of Prony series by using the principle of WLF time temperature equivalence. The finite element model of biaxial stretching is established, and the temperature field of heating and cooling process in biaxial stretching of plexiglass is analyzed. The calculated temperature field results are introduced into the biaxial stretch dynamic analysis. The displacement and stretch force curves are obtained for 9 fixtures, and the displacement stretch force relationship expression is fitted. The cooling shaping simulation of the stretched plexiglass is carried out. The force generated by the cooling of aviation glass is about twice the stretch force. The retraction of the pull rod is adopted to reduce the shrinkage force of 10000N to prevent glass breakage or equipment damage. The biaxial stretch test results of 35mm thick aviation glass are consistent with the simulation results. The stretch process is optimized according to the simulation results, and the tensile quality and success rate are improved.

    A Study on the Wake Vortex Encounter and Movement Interference Characteristics of Projectiles Successively Launched Underwater
    SHI Yao, REN Jinyi, GAO Shan, PAN Guang, QUAN Xiaobo
    2023, 44(10):  3195-3203.  doi:10.12382/bgxb.2022.0616
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    In order to study the wake vortex interference and trajectory characteristics of projectiles launched successively underwater at different launching time intervals, based on the Realizable k-ε turbulence model and energy equation, volume of fluid (VOF) and overlapping grid technology were adopted. Firstly, verification of numerical method and validation of grid independence were presented. The numerical simulation results were in good agreement with the experimental results. Then the numerical simulation method of projectiles launched successively underwater was established. Based on these, the pressure distribution on the side facing the inflow as well as on the backside, trajectory and pitch attitude, particularly the evolution mechanism of vortex in wake flow were studied. The results showed that hairpin vortex-like flow structure was found, multiple hairpin vortex-like flow structures usually exist in a combined form in the flow field region at the tail of the vehicle. The jet event occurred along the inner side of the vortex leg, and the sweep event occurred outside the vortex leg. Meantime, along the inside of the vortex, a low-speed band with a certain streamwise scale was formed. Under the transverse-flow effect, when the surface of the secondary projectile passed through the low-speed strip region of the vortex in the wake, the pressure distribution characteristics of the flow facing side and its opposite side were greatly improved, the stability of trajectory and pitch attitude was increased.

    Recognition of Dense False Target Jamming with Large Fluctuations Using Frequency Response Characteristics
    WEI Wenbin, PENG Ruihui, SUN Dianxing, ZHANG Jialin, WANG Xiangwei
    2023, 44(10):  3204-3217.  doi:10.12382/bgxb.2022.0610
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    Forwarding dense false target jamming is suppressive and deceptive jamming, with jamming signals quite similar to those of the target echo, thus posing challenges for recognition. Based on the generation mechanism of dense false target jamming and the physical characteristics of the Ratio Frequency link, the frequency response characteristics of radar and jammer and the mechanism model of their influence on the amplitude-frequency mapping characteristics of true and false target echoes are systematically studied and proposed. On this basis, leveraging the large dynamic range of jamming signal power, a method of dense false target jamming recognition based on frequency response characteristics and large dynamic SNR/JNR is proposed. Through the construction of basis classifier with a dual-channel feature fusion network comprising convolutional neural network and long short-memory network (ODCNN-LSTM), the M/N logical criteria is used to integrate the basis classifiers. Then, feature extraction and recognition of true and false echo signal frequency response fluctuations are realized. The recognition accuracy is over 94.5% for the measured data, demonstrating the effectiveness and innovation of the proposed method. This work holds significance for recognizing dense false target jamming with significant fluctuations.

    Target Bearing Estimation Using Vortex Electromagnetic Waves with Mutual Coupling
    ZHANG Hongyun, LI Ping, LI Guolin, JIA Ruili
    2023, 44(10):  3218-3226.  doi:10.12382/bgxb.2022.0480
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    The use of a uniform circular array to generate vortex electromagnetic waves can lead to changes in the radiation pattern of antenna elements due to mutual coupling between adjacent array elements, causing variations in amplitude and phase that affect target azimuth detection performance. To address this problem, the mutual coupling matrix is expanded into the mode domain by Fourier transform using the symmetric circulant of the uniform circular array mutual coupling matrix. This allows for describing the relationship between array element excitation and the number of orbital angular momentum modes. Based on the above analysis, an improved propagation operator decoupling azimuth estimation algorithm based on orbital angular momentum is proposed, which avoids spectral peak search and large eigenvalue decomposition. Simulation results show that the mutual coupling matrix in the mode domain effectively compensates for the influence of the mutual coupling effect. Compared with traditional algorithms, the proposed algorithm boasts lower computational complexity and avoids errors stemming from Bessel function approximations.

    Near-field Source Location Estimation Method Based on Coprime Arrays
    WANG Xuhu, TIAN Yu, ZHANG Qunfei, LI Enyu, JIN Xu, HOU Yujun
    2023, 44(10):  3227-3236.  doi:10.12382/bgxb.2022.0733
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    For the problems that the number of detection signals is limited by the number of array elements and the estimation accuracy is affected by the array aperture for uniform linear array, a near-field source location estimation method based on coprime arrays is proposed. In the proposed method, the received data of the coprime array is preprocessed, and a model that contains only angle parameter is established. The angle offset vector and power vector are modified gradually by iterative method to obtain the final DOA of incident signal. An off-grid model about the distance parameter is established by fixing the estimated angle. The distance estimation value is obtained by iteratively modifying the distance offset vector gradually. The proposed method was verified by simulation test. Theoretically analyzed and simulated results show that the proposed method is used to expand the array aperture effectively improve the estimation accuracies of angle and distance, and still has good estimation performance in the case of low signal-to-noise ratio and small snapshots. At the same time, the estimated angle and distance are automatically matched to determine the location of near-field source.