Table of Content

29 April 2022, Volume 43 Issue 4

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Contents

2022, 43(4):  0. 

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Paper

Jamming Signal Design of Pseudo-code Phase Modulation Fuze Based on Duffing Oscillator

YAN Xiaopeng, WANG Ke, LIU Qiang, HAO Xinhong, YU Honghai

2022, 43(4):  729-736.  doi:10.12382/bgxb.2021.0173

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A reconstructed spoofing jammping method based on parameter blind estimation is proposed to effectively jam the pseudo-code phase-modulated fuze. On the basis of establishing the multiplication relation among the output signal of Duffing oscillator，the pseudo-random code signal of fuze signal，and the difference frequency signal of fuze signal and the internal driving signal of Duffing oscillator，the blind parameter estimation of fuze carrier frequency and pseudo-random sequence is realized based on the implied periodicity of Duffing oscillator.The fuze's jamming signal is reconstructed based on the high-precision estimated results，andthe jamming effect of the jamming signal on the pseudo-code phase-modulated fuze is analyzed theoretically. The proposed blind parameter estimation method and the jamming effect of the reconstructed signal are simulated and verified by the semi-physical experiment. The simulated and experimental results show that the blind estimation method maintains good parameter estimation performance up to an SNR of -35 dB and further reconstructs the fuze jamming signal.It is superior to other traditional jamming methods.

Soft Measurement Method for Health State of Typical Complex Feeding and Ramming Mechanism Based on Time-frequencyData Drive

ZHANG Gang, LIANG Weige, SHE Bo, TIAN Fuqing

2022, 43(4):  737-747.  doi:10.12382/bgxb.2021.0068

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The operating environment of complex feeding and ramming mechanisms is harsh, and the vibration signals collected by sensors contain violent impact, noise and other components, which are typical non-stationary characteristic signals, and the health state of feeding and ramming mechanisms is difficultly evaluated. To solve these problems, a soft measurement method based on time-frequency data driving is proposed for measuring the health state of feeding and ramming mechanism. The time-frequency graph of vibration acceleration signal, as an input feature, is obtained by Morlet wavelet transform, and a soft measurement model based on deep convolutional network is established. The Dropout regularization term is introduced into the deep convolutional network to relieve overfitting phenomenon, and the uncertainty of soft measurement results is analyzed quantitatively. The bench test of complex feeding and ramming mechanism shows that the proposed soft measurement method can effectively distinguish the health state of feeding and ramming mechanism with the accuracy of 90%. In the stage of performance degradation, the degradation degree of the mechanism performance can be quantitatively analyzed, and the measured error is about 7%. Compared with other data-driven soft measurement methods for health state, the proposed method can effectively improve the identification accuracy of health state and the measuring accuracy of performance degradation of feeding and ramming mechanisms, and reduce the uncertainty of measureed results.

Jet Formation and Penetration of Shaped Charge with Isosceles Trapezoidal Cross-section

WANG Yuting, HUANG Zhengxiang, ZU Xudong, MA Bin, XIAO Qiangqiang, JIA Xin

2022, 43(4):  748-757.  doi:10.12382/bgxb.2021.0225

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The jet formation of shaped charge with isosceles trapezoidal cross-section and its penetration characteristics are studied through pulsed X-ray photography and depth of penetration tests. The jet formation is simulated by using ANSYS/LSDYNA finite element software，and the influence of the inscribed circle size on jet formation is studied when other parameters are fixed. The results show that the shaped charge with isosceles trapezoidal cross-section forms a jet with lateral velocity，and the lateral velocity has a gradient distribution. Except for the jet head，the rest of jet is cohesionless at the late stage of stretching. The non-condensed part of jet consists of two fluids with different lateral velocities and different sizes. The penetration ability of jet is reduced due to its lateral velocity. The non-condensation phenomenon of jet disappears when the inscribed circle diameter of charge cross-section increases to 67.2 mm (being 1.2 times of 56 mm)，and the jet does not have an obvious lateral velocity when the inscribed circle diameter of charge cross-section increases to 84 mm (being 1.5 times of 56 mm).

Bullet-proof Performance of Ceramic Composite Armors against 14.5mm Armor-piercing Projectiles

ZHANG Lin, CHEN Bin, TAN Qinghua, ZHANG Wei, GAO Song

2022, 43(4):  758-767.  doi:10.12382/bgxb.2021.0244

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Large-caliber anti-armor weapons are playing an increasingly important role in the battlefield，and higher requirements are put forward for the armor materials and structure design. In order to explore the bulllet-proof mechanisms and performance of ceramic composite armor penetrated by 14.5 mm armor-piercing projectile，an armor structure with ceramic/fiber/metal/flexible material/metal layup configuration was designed，and the influences of thickness matching，bottom plate material and flexible material on the ballistic performance were discussed through experiments.The results show that the thickness of ceramic plate has an influence on the bullet-proof performance significantly，and when the thickness of ceramic plate is 1.38 times of the core diameter，the targets have excellent bullet-proof performance. For the similar surface density and the constant ceramic thickness，the dimension matching of the composite rear plates has little influence on the bullet-proof performance when changing in a certain range.For the similar surface density，the thickness of the bottom plate should be larger when the armored aluminum is selected，and the anti-penetration performance is better. The flexible material can not only decrease the damage area，but also make the projectile yawed and change the incidence angle of projectile，thus improving the protective performance of the composite armor.

Ballistic Limit Calculation Model of Tungsten Alloy Spherical Fragments Penetrating into Low Carbon Steel Plate

LIU Tielei, XU Yuxin, WANG Xiaofen, ZHANG Peng, ZHANG Jian

2022, 43(4):  768-779.  doi:10.12382/bgxb.2021.0448

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The penetration failure characteristics of tungsten alloy spherical fragments penetrating into low-carbon steel plate at different target speeds are analyzed to obtain a ballistic limit calculation model of tungsten alloy spherical fragments penetrating into low-carbon steel plate in a wider speed range. A ballistic limit calculation model including the main mechanical parameters of projectile and target is proposed. The fragment rigidity，plasticity, erosion and fragmentation penetration iare considered in the proposed model. A calculation method of velocity threshold for different failure characteristics of tungsten alloy is established for the need of solving the model. Based on the existing experimental data, the model coefficients are obtained by using trust region method. In addition, the ballistic limit of fragments penetrating into Q235 and Q345E steel plates is test，and the calculation accuracy of the model is analyzed according to the test results. The results show that the calculated average error and maximum error of the model are 10% lower than those of the test results，and the average error of the model is reduced by 60% compared with the existing ballistic limit calculation model.

Modification of Hydroxyl-terminated Polyether Binder by Liquid Fluororubber and Its Effect on Thermal Oxidation Behavior ofAluminum Powder

SHEN Chen, YAN Shi, YAO Jie, JIAO Qingjie, LIAO Mingyi, CHANG Yunfei

2022, 43(4):  780-787.  doi:10.12382/bgxb.2021.0184

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The combustion of aluminum powder promoted by fluoride is a hot spot in the field of energetic materials in recent years. Hydroxyl terminated liquid fluororubber with high fluorine content is selected as fluorine source，which is introduced into hydroxyl-terminated polyether (HTPE) adhesive system to prepare modified HTPE films with different fluorine rubber contents.The morphology，mechanical properties，thermal stability and oxidizability of the modified HTPE films were tested and analyzed. The results show that the mechanical properties of the film decrease first and then increase with the increase in fluororubber content. The tensile strength and elongation at break of the film with fluororubber content of 50 wt% are 2.51 MPa and 217%，respectively. Compared with the unmodified HTPE film，its tensile strength is increased by 83%，and its elongation at break is decreased by 17%. Liquid fluororubber promotes the decomposition of HTPE polyurethane adhesive，and the initial decomposition temperature shifts from 263 ℃ to 209 ℃. The fluorine-containing oxidizing gas decomposed by the modified adhesive reacts with the alumina shell of aluminum powder to form AlF₃，which promotes the release of internal active aluminum core.

Characteristics of 5-aminotrazole/sodium Periodate Low-temperature Gas-generating Agents

YUAN Jianwen， QI Xuan， DONG Cheng， YI Zhenxin， ZHANG Lin， ZHU Shunguan

2022, 43(4):  788-795.  doi:10.12382/bgxb.2021.0198

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5-AT/NaIO₄/CuO composite particles are prepared to obtain low-temperature gas-generating agents by spray drying method. The size and morphology of 5-AT/NaIO₄/CuO particles are characterized by scanning electron microscope. The combustion performances of gas-generating agents were tested using TG-DSC，automatic oxygen bomb calorimeter，thermocouple and target line method. The results show that 5-AT/NaIO₄/CuO composite particles are characterized as 2~4 μm microspheres and well-distributed. The addition of nano CuO reduces average combustion heat by 300 J/g and combustion temperature by 100 ℃.The minimum combustion temperature is 1 013 ℃,and the maximum and minimum burning rates are 3.94 mm/s and 0.76 mm/s respectively. The supplement of nano CuO effectively reduces the burning residuals with the residue rate of about 6.7%. The formula is characterized as low combustion temperature and little residuals.

Infrared Radiation Feature of Near Space Hypersonic Cruise Vehicle

SHI Anhua, LI Haiyan, SHI Weibo, LIANG Shichang

2022, 43(4):  796-803.  doi:10.12382/bgxb.2021.0105

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To meet the demand for optical characteristic data of near-space hypersonic cruise vehicles for the detectability analysis of space-based infrared early warning satellites and the design of future space-based infrared early warning satellitesthe flow-field parameters, body temperature, infrared radiation spectrum, infrared radiation luminance, and infrared radiation intensity of the hypersonic cruise vehicle like X-51A under the typical flight condition are studied based on the combined computation and analysis methods of hypersonic aerodynamics, combustion theory, heat transfer theory, gas radiation theory, and so on. The calculated results show that the radiation features of the hypersonic cruise vehicle like X-51A are influenced by the flight time and ballistic. The infrared radiation of the body is influenced obviously by the aerodynamic heating. The jet flame radiation of the vehicle using aviation kerosene as fuel has strong radiation band of CO₂, H₂O and CO with wavelength of 1.52 μm, 2.68 μm and 4.39 μm. The jet flame radiation contributes most to the total narrow-band radiation, including the strong characteristic radiation spectra of CO₂, H₂O and CO molecule. The body radiation of the vehicle dominates the total radiation at the wavelength band which doesn’t include the characteristic radiation spectra of CO₂, H₂O and CO molecule.

Influence of Twice Air-entering on the Combustion and Ablation Environment of Solid Rocket Ramjet

WEN Yihao, WANG Jinjin, ZHA Bailin, XU Zhigao

2022, 43(4):  804-813.  doi:10.12382/bgxb.2021.0200

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The effect of twice air-entering on the combustion efficiency of afterburner and the ablation environment of inner wall was studied for the design of air-inlet of solid rocket ramjet afterburner. The standard k-ε model, the eddy dissipation model and the King boron particle ignition model were adopted to simulate the multiphase combustion in the single and twice air-entering afterburners. Through comparative analysis，the following conclusions were drawn as follow. The twice air-entering can coat the mixed gas and squeeze it inward to compress the high temperature area and changeg the oxygen distribution，which reduces the area of the high temperature inner wall，decrease the temperature of the low temperature wall，and cut down the number of condensed phase particles close to the wall，thereby weakening the thermal ablation，oxidation and erosion of condensed particles in the inner wall.Because of the greater kinetic energy loss which reduces the airflow velocity close to the inner wall，it also weakens the airflow scouring effect.Thus the ablation environment in the inner wall of afterburner is improved. However，twice air-entering has little effect on the combustion efficiency，and the total combustion efficiencies of afterburners with single air-entering and twice air-entering reach 80.68% and 80.18%, respectively. Considering the two aspects of combustion efficiency and ablation environment of the inner wall, it can be considered that twice air-entering is better than once air-entering.

Application in Damage Effect Evaluation of Early Warning Radar of Cloudy Bayesian Network Based on Dempster Shafer/AnalyticHierarchy Process Method

DENG Liyuan, YANG Ping, LIU Weidong, WANG Jiangpeng

2022, 43(4):  814-825.  doi:10.12382/bgxb.2021.0036

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Target damage evaluation can provide a credible basis for combat decision-making and is an indispensable key link in joint operations. A cloudy Bayesian network-based early warning radar damage evaluation model is established combining Bayesian network and cloud model to form a cloudy Bayesian network, and the cloud model is converted for various indicator system variables. For the defects of the traditional expert experience method in deriving the conditional probability, the dempster-shafer/analytic hierarchy process (DS/AHP） is used to determine the conditional probability value of each node. The variables are input into the cloudy Bayesian network, and the probability that the early warning radar belongs to each damage level is inferred. The proposed method is applied to the simulation calculation of the attack on the early warning radar system in the enemy's anti-missile system, and the effectiveness of cloudy Bayesian, network is compared with those of Bayesian netwok, fuzzy comprehensive evaluation method and cloud barysenter evaluation method. The simulated results show that cloudy bayesian network based on dempster-shafer/analytic hierarchy process method has a certain degree of improvement in terms of calculation rationality and calculation accuracy. It is an analysis method that can reasonably and effectively evaluate the damage effect of target.

Design and Simulation of Vector Nozzle on Amphibious Vehicle

WANG Tailin, WANG Ye, ZHANG Fuyi, CHEN Huiyan, WANG Guoyu

2022, 43(4):  826-850.  doi:10.12382/bgxb.2020.0739

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A new type vector nozzle is proposed to improve the maneuverability and stability of amphibious vehicle. The nozzle which has two degrees of freedom in pitch and rotation can change the direction of the water jet and output a three-dimensional vector thrust. According to the waterjet propulsion theory of amphibious vehicle，the basic parameters of pump which can satisfy the power demand and the platform restriction are calculated. The structure and control strategy of vector nozzle integrated with the pump are designed according to the calculated diameter. The output vector thrusts at different vehicle speeds，pump rotation speeds，pitch and rotation angles are calculated using the computation fluid dynamics simulation software Fluent. The maneuvering mechanisms of non-vector waterjet propulsion amphibious vehicle，single vector waterjet propulsion amphibious vehicle and dual vector waterjet propulsion amphibious vehicle are analyzed and compared. The influence of vector waterjet on the seakeeping performance of amphibious vehicle is analyzed. The seakeeping dynamics equation and the pitch-roll moment equation are established. On this basis，the pitch-roll stability control strategy of vector propulsion amphibious vehicle is proposed. The simulated results show that the axial thrust decreases with the increase in pitch angle，the pitch thrust or the yaw thrust increases with the increasing pitch angle. The comparison results demonstrate that, compared with non-vector waterjet propulsion amphibious vehicle，the vector waterjet propulsion amphibious vehicle has obvious advantages in lateral translation，oblique translation，in-situ steering and propulison efficiency. The vector waterjet designed produces the vector thrust which can not only provide longitudinal driving force for the amphibious vehicle，but also lateral force，yaw and pitch torque，providing a new scheme for improving the maneuverability and stability of the future amphibious unmanned platform.

Impact Performance of Cushion Nose Cap of Underwater Vehicle Based on CEL Method

QUAN Xiaobo, BAO Jian, SUN Longquan, WANG Duliang

2022, 43(4):  851-860.  doi:10.12382/bgxb.2021.0168

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The underwater vehicle will be subjected to strong impact load in the process of water entry，and the excessive impact load can easily cause structural damage and internal equipment failure. The technology of load reduction during high-speed water entry is studied. A cushion nose cap with prefabricated cracked carbon fiber material as outer cover and foamed aluminum as inner cushion material is designed.The numerical simulation is based on the finite element method，and the coupled Euler-Lagrange solver is used to study the load reduction effect of cushion nose cap.The effectiveness of the numerical method is verified by comparing the numerical results with the experimental images of a sphere entering into the water.The impact resistance，damage mode of cushion nose cap and the evolution process of cavitation bubble at different water entry speeds and angles are analyzed. The results show that the cushion nose cap shatters along the prefabricated cracks after hitting the water surface. The foamed aluminum is compressed and absorbs energy.As the cavitation bubble below the free surface expands outward，the broken nose cap spreads around the inner wall of cavitation bubble. The cushion nose cap has a good load-reduction effect on underwater vehicle at different water entry speeds，and water entry angles. Under the worst condition of vertical water entry，the load reduction rate is more than 75%.

Fault Identification of Machine Tool Spindle System Based on Attention Mechanism and Deep Learning Algorithm

WANG Weiping, WANG Qi, YU Yang

2022, 43(4):  861-875.  doi:10.12382/bgxb.2021.0202

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The overall dynamic degradation fault of the numerically-controlled machine tool spindle system with complex nonlinear characteristics is difficultly identified and investigated.An intelligent fault identification method based on attention mechanism and depth learning algorithm is proposed to stud the overall fault identification of spindle system by starting with data analysis.The proposed method is used to design the research framework of attention mechanism，and divide the research problems into global vertical large classification interval dimension and local horizontal fine-grained interval dimension.The gated recurrent unit model with reasoning average absolute error of 0.028 7 after training and tuning is used to identify the global degradation faults in large classification interval.The residual network model with strong robustness and identification accuracy of 99.7% is used to accurately identify the local fine-grained interval faults， based on sym8 wavelet basis adaptive soft threshold noise reduction.The results show that the proposed method is used to quantitatively identify the overall fault of spindle system. The proposed attention mechanism is used to effectively distinguish the faults that cannot be accurately identified in the large classification interval in the fine-grained interval，and the data growth gradient in the category increases from 6.6% to 43.8%. The effectiveness and accuracy of the proposed method are verified by studying the typical faults，such as misalignment and local resonance encountered in the actual use of the machine tool spindle system under no-load，and the fault identification under loading.

Flow Field Distribution and Morphology Variation of Particles in Planetary Ball Milling

LI Xu, LIU Yan, AN Fengjiang, WANG Hongfu, XU Yingliang

2022, 43(4):  876-891.  doi:10.12382/bgxb.2021.0252

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The flow field distribution of particles in the planetary ball milling is explored based on the discrete element simulation. The relative velocity distribution of ball-particle group collision during the ball milling is calculated. Then the collision scene of a single ball is extracted，and the impact field of multi-layer particles is simulated to study the interlaminar compressive stress distribution. The planetary ball milling experiments of Al/PTFE mixed particles and Al particles were carried out，and the average diameter of particles at different time is recorded to characterize the change of particles morphology. The theory of the average diameter change of particles based on the broken probability and the fractal number of particle group is proposed.The results of discrete element simulation show that the low velocity collision is the main part of the ball-particle group collision. Only 1% of collision is the relative high velocity collision with normalized velocity ξ>0.33, and the Weibull distribution can well characterize the distribution of relative collision velocity. As for the impact field of multi-layer particles， the distribution of the multi-layer particles’ interlayer compressive stress tends to be dumbbell-shaped or gourd-shaped with the increase in ball collision velocity. The experimental results show that the average diameter of particles shows the exponential decaywith the increase in milling time.

Influence of Yield Stress on the Starting Torque of Magnetic Fluid Seal

HE Xinzhi, WANG Zhibin, LI Decai

2022, 43(4):  892-898.  doi:10.12382/bgxb.2021.0250

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Magnetic fluid seal is the most mature application of magnetic fluid. The sealing performance of magnetic fluid seal changes with the extension of standing time, especially the phenomenon that the starting torque of the magnetic fluid seal increases with the extension of standing time may cause difficulty in starting the seal or even damage. In order to explore the mechanism of this phenomenon, the relations among the starting torque of magnetic fluid seal with temperature, standing time, the amount of magnetic fluid injected and the pressure exerted on the magnetic fluid are experimentally studied, and the changing reasons of the starting torque of magnetic fluid seal are theoretically analyzed. The results show that the lower the temperature is, the longer the standing timeis , the greater the amount of magnetic fluid injected is, and/or the lower the pressure is, the greater the starting torque is. The essence of this phenomenon is thatthe particles in magnetic fluid form chain-like structures under the action of magnetic field. Yield stress needed to break chain-like structures is the cause of changing starting torque.

Calibration Method for Sensitivity Coefficient of High-temperature Strain Gauges at High Strain Rate

WANG Fan, GUO Weiguo, WU Qian, GAO Meng

2022, 43(4):  899-909.  doi:10.12382/bgxb.2021.0189

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A new method is used to calibrate the sensitivity coefficient of the high-temperature strain gauge at high strain rate.The high-temperature strain gauge under calibration is pasted on the surface of a standard specimen by using the split Hopkinson bar with synchronous assembly device，and they are placed in the same temperature and stress environment. The specimen is subjected to impact loading at constant temperature. The sensitivity coefficient of the high-temperature strain gauge is obtained by collecting，calculating and comparing the output signals of the standard strain gauge on the split Hopkinson bar and the high-temperature strain gauge on the specimen. The calibration method applies to calibrate the sensitivity coefficient of guage at the strain rate of 10³ s^-1 in the temperature range from 293 to 1 473 K. The error of the calibrated sensitivity coefficient caused by the dispersion and attenuation of stress wave have a linear relation with the integral of the amplitude of the incident wave，and the experimental relative error is only 2.39%. The error caused by the inhomogeneous plastic deformation of sample is less than 1.5%，and the uncertainty of calibrated results is 1.517%.The experimental results show that the proposed method can be used to calibrate the sensitivity coefficient of the high-temperature strain gauge at high temperature and high strain rate.

Optimal Design of High-precision Temperature Control System for FOG Detection

SUN Ning， XIA Yan， CHENG Xingqing

2022, 43(4):  910-918.  doi:10.12382/bgxb.2021.0187

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The high-precision fiber optic gyroscope (FOG) products need to be tested in batches in a large-scale space without obvious air flow. For this purpose, the optimization design of precision temperature control device with radiation cold plate as the core element is studied，and the reliability of the device is verified by theoretical，simulation and experimental methods. The effect of optimization design is remarkable. The results show that the temperature uniformity is no more than 2 ℃，the temperature fluctuation is no more than ±0.05 ℃ within 24 hours，and the recovery time of temperature field is no more than 30 minutes under the effect of temperature fluctuation. The optimization research solves the technical problem of no wind and low fluctuation in the detection of ambient temperature control，breaks through the limitation of detection space in the traditional technical route，and realizes the batch detection of high-precision fiber optic gyroscopes in large scale space.

Maximum Entropy Test Method for Evaluating the Output Reliability of Space Actuators

JI Ming， BU Junjun， MA Cong

2022, 43(4):  919-923.  doi:10.12382/bgxb.2021.0196

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A maximum entropy test method is proposed to evaluate the output reliability of space actuator with small sample size. According to the margin design characteristics of space actuator，the output force of the actuator is selected as the characteristic quantity to represent its output reliability. The output reliability is evaluated by experiment and calculation at critical operating points，and the evaluation process is introduced in detail. The results show that the proposed method can be used to evaluate high reliability (0.999 9 reliability with confidence of 0.95) with only a small number of test samples，and can significantly reduce the cost of production and test. The evaluated results are consistent and credible after recalculation by variables evaluation method.

Detection of Overlapped Bullet Holes Based on Improved Otsu's Thresholding Method

SONG Yu, WANG Yalin, DU Bojun, WANG Jun, DONG Xingfa

2022, 43(4):  924-930.  doi:10.12382/bgxb.2021.0201

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The traditional automatic target-scoring system has a low detection rate for the overlapped bullet holes on the target plate hit by successive projectiles. Generally, the automatic target-scoringing system based on image processing recognizes the overlapped target holes as one bullet hole, which leads to a high missed detection rate. To solve this problem, a new method based on Otsu is presented. The bullet holes recognition method based on improved Otsu method is employed to segment the overlapped bullet hole image and its background, and then the overlapped bullet hole region is obtained from the segmented image by the two-pass algorithm. The minimum bounding rectangle method is used to position the center of the two bullet holes in the overlapped bullet hole region. The results show that, compared with the traditional Hough transform, the proposed method can be used to effectively position the center of the two bullet holes and calculate the center coordinates. The measured error of bullet holes is not more than 3 pixel for the overlapped holes of which the degree of overlap is less than 88.73%. The improved method is capable of reducing the computational time and improving the positioning accuracy of bullet hole center with a low computational complexity, which plays a significant role in improving the detection accuracy of target hole.

Health Evaluation of Missile Control System based on RBF and SOM

LIU Yue, LIU Tielin, JIANG Xiangzheng, HAN Yueming

2022, 43(4):  931-939.  doi:10.12382/bgxb.2021.0219

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Traditional health evaluation methods of missile weapon rely heavily on the experience and ability of designers and product experts，which is inefficient and inaccurate.For missile control system，a health state evaluation method based on Radial Basis Function（RBF） network observer and Self-organizing map（SOM）network is proposed. The adaptive fault observer based on RBF network is used to calculate the residuals of output signals and the adaptive discriminant thresholds under different working conditions. Through the comparison between the residual and threshold values，the fault detection is realized.The health evaluation model based on SOM network is used to realize the cluster analysis of residuals. Through the distance measurement，the health evaluation is realized.A missile control system case is used to verify that the proposed method can detect 10 different fault modes and evaluate 10 different health states accurately, and provides technical support for maintenance support and logistics management.

Fatigue Crack Length Measurement Method Based on Edge Detection and DIC

HUANG Xinwei， SHAN Xiaofeng， GAO Hongli， WANG Chen

2022, 43(4):  940-951.  doi:10.12382/bgxb.2021.0268

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For the difficult detection of crack closure section due to the obvious crack closure phenomenon in advanced high-strength steel plates，a high-precision dynamic measurement method of fatigue crack length based on the combination of edge detection and digital image correlation (DIC) technology is proposed. Two cameras are used to acquire the crack images and speckle images of two sides of the crack specimen during the fatigue crack growth test for processing，which can detect the closed section of the crack which can not be detected by the gray-scale edge detection method，thereby improving measurement accuracy. The fatigue crack growth path is obtained from the crack image by the gray edge detection method, and the crack tip is initially located. Then，the template matching technology is used to map the detected crack path coordinates to the speckle image，and the virtual extensometers are arranged on both sides of the crack tip extension. The opening displacement of virtual extensometer is obtained by DIC. Then the displacement-position curve of extensometer is fitted， the characteristics of the curve are analyzed to obtain the sub-pixel precision abscissa of the fatigue crack tip，and the crack length is accurately calculated. Finally，the results obtained by the edge detection method， the proposed method，and the measuring microscope are compared. The results show that the proposed method has a significant advantage in measurement accuracy compared with the edge detection method. It can be used to effectively detect the closed section of the crack with the measurement accuracy of 8 μm.

A Weapon-target Assignment in Air-defense Operations Based on Shooting Probability Constraint

ZHI Hongxin, ZHAO Peng, LI Zhong, PENG Xiangxin, LU Xuyang, WANG Chen

2022, 43(4):  952-959.  doi:10.12382/bgxb.2021.0177

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A novel weapon-target assignment model based on shooting probability constraint is proposed in which the impact of shooting probability on the effectiveness of air-defense operations is considered. The proposed model takes many factors into account，such as shooting probability，air strikes intensity，and fire transfer time of firepower unit. The proposed can give priority to using firepower units with quick response to intercept the targets with short flying time on the premise of meeting the thresholds of shooting probability and joint damage probability. At the same time，it minimizes the consumption of fire resources to provide continuous combat capability for the air-defense system.On this basis，an improved equilibrium optimizer algorithm based on nonlinear adaptive inertia weight is presented to solve the weapon-target assignment problem. The Tent chaotic map is used to generate the initial population to enhance the diversity of the population. And the inertia weight is introduced to balance local search and global search ability，which effectively improves the optimization ability of the algorithm. Simulated results verify the advantages of the proposed model and the effectiveness of the optimization algorithm.

Application of Path Planning Based on Improved A^* Algorithm in War Gaming of Naval Warfare

ZHANG Tao, XIANG Qi, ZHENG Wanwen, SUN Yuxiang, ZHOU Xianzhong

2022, 43(4):  960-968.  doi:10.12382/bgxb.2021.0209

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A path planning method based on improved A^* algorithm is proposed, which can be used as a reference for similar war gaming environment. The proposed method is to meet the needs of multi-objective path planning in war gaming of naval warfare and solve the problem that traditional A^* algorithm cannot be directly used in war gaming. A mapping mechanism is constructed to realize the preliminary application of A^* algorithm in war gaming environment，and an evaluation function is constructed to improve the A^* algorithm, which can not only meet the multi-objective needs, but also ensure the generation of the optimal path. In order to verify the effectiveness of the improved A^* algorithm, the experiment was carried out on a war gaming platform of naval warfare. The result shows that the proposed method can be used to coordinate the relationship between multiple decision indicators well, effectively improve the quality of path scheme, and solve the practical problem of using A^* algorithm to carry out the optimal path planning in war gaming of naval warfare.