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    30 January 2024, Volume 45 Issue 1
    Electronic edition of this issue
    Electronic edition of this issue
    2024, 45(1):  0. 
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    Contents
    Contents
    2024, 45(1):  0. 
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    Research on the Pressure Relief Structure of JEO Shaped Charge Warhead during Cook-off
    WANG Xinyu, JIANG Chunlan, WANG Zaicheng, FANG Yuande
    2024, 45(1):  1-14.  doi:10.12382/bgxb.2022.0435
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    A pressure relief structure of JEO shaped charge warhead during cook-off is studied to improve the thermal safety of JEO shaped charge warhead. A multiphase flow component transport model of explosive cook-off is established, in which the effect of thermal decomposition pressure on the cook-off process is considered. A multi-point temperature and pressure measurement experiment is designed to study the temperature and pressure change characteristics of JEO explosive during the cook-off process and check the relevant parameters of the model. The thermal decomposition process of JEO explosive in the shaped charge structure is numerically simulated to obtain the change laws of temperature and solid volume fraction of the explosive under different heating rates, and determine the ignition position and pressure of the explosive in the structure. In view of the combustion process of JEO explosive after ignition, the pressure relief delay time is introduced, and an explosive pressure growth model considering the pressure relief structure is established. The critical pressure relief area of JEO explosive in this structure is determined. The influence law of different charge ignition positions on the internal pressure change of the explosive is calculated and obtained by taking the ignition position and ignition pressure obtained in the thermal decomposition numerical simulation as initial conditions. According to the critical pressure relief area, ignition position and pressure growth in the explosive, the area of pressure relief hole on side wall and the pressure screw size of the end liner are determined, and a combined pressure relief structure of pressure relief hole and liner push-out suitable for JEO explosive in this structure is designed. Fast and slow cook-off experiments were carried out on JEO shaped charge warhead with the pressure relief structure, and the effectiveness of the pressure relief structure was verified. The research results indicate that as the heating rate decreases, the ignition time of JEO charge shaped charge warhead is prolonged, and the ignition position moves from the surface of the charge to the center of the charge. As the distance between the ignition position and the pressure relief structure increases, the ignition delay time increases, the peak pressure inside the shaped charge warhead increases, and the reaction intensity of the warhead also increases.

    Preparation of Energetic Burning Rate Inhibitor and Its Negative Catalytic Effect on AP Decomposition
    ZHANG Xuexue, XUE Zhihua, NIE Hongqi, YAN Qilong
    2024, 45(1):  15-25.  doi:10.12382/bgxb.2022.0518
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    As the key functional component of solid propellant, the burning rate inhibitor plays an important role in regulating the burning rate of solid propellant. In this paper, the quaternary ammonium and aldehyde-based structures with combustion suppression effect are precisely designed and evaluated. The high nitrogen triaminoguanidine glyoxal two-dimensional copolymer(TAGP) is used as an energetic ligand. It is complexed with alkaline earth metal ions, such as K+, Ba2+ and Ca2+, to prepare a series of novel energetic burning rate inhibitors(so called TAGP-M). The morphologies, structure and thermal stability of the as-prepared compoundsare characterized by X-ray diffraction,X-ray photoelectron spectroscopy, scanning electron microscope/energy dispersive spectrometer, and differential scanning calorimetry and thermogravimetric analysis techniques. The negative catalytic effect of energetic burning rate inhibitor on ammonium perchlorate (AP) decomposition is analyzed. It shows that TAGP-K has obvious inhibitory effect on the crystal transition of AP. In presence of TAGP-K, the endothermic peak temperature of AP crystal transition is increased by 5.9℃, whereas the first peak decomposition temperature is increased by 28.7℃. More importantly, the use of 10 wt% TAGP-K could reduce the maximum thermal decomposition rate of AP by 58%. The corresponding energy release of AP is focused to high-temperature decomposition(HTD) process. The heat release of AP/TAGP-Ca is more than 50% higher than that of pure AP during HTD process. It shows that TAGP-Ca and TAGP-Ba increase the energy release efficiency of AP while inhibitingits decomposition. The TAGP-M burning rate inhibitors release NH3 during the decomposition process and combine with HClO4(AP decomposition product) to form $\mathrm{M}\left(\mathrm{ClO}_{4}^{-}\right)_{n}$ which is more difficult to decompose.The HTD process of AP is inhibited by the strong electrostatic interaction between alkaline earth metal ions and $\mathrm{ClO}_{4}^{-}$, which inhibits the decomposition of $\mathrm{ClO}_{4}^{-}$ to generate an oxidizing atmosphere and prevent theoxidative exotherm of the adsorbed NH3.

    SHS-assisted Shock Sintering and Characterization of TiB2/B4C Composite Ceramics
    LI Yunfei, GAO Xin, CHEN Pengwan, LIU Kaiyuan
    2024, 45(1):  26-34.  doi:10.12382/bgxb.2023.0078
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    In order to explore the efficient and low-cost preparation method of high hardness composite ceramics, the titanium diboride/boron carbide (TiB2/B4C) composite ceramics with a thickness of about 1 cm and a diameter of about 5cm was fabricated by SHS-assisted shock sintering method. The results of phase and microstructure analysis show that TiB2 phase and B4C phase are evenly distributed in the sintered samples, and dense micron particles are observed in the cross section. The density and hardness of the samples prepared by this method are relatively high. The density ranges from 90% to 93% with the change of shock pressure, and the corresponding average Vickers hardness ranges from 16.64GPa to 17.35GPa. The analysis of the microstructures and densities of the recovered samples under different conditions show that the shock pressure and the pre-detonation temperature have an important effect on the consolidated quality of TiB2/B4C composite ceramics. When the shock pressure is 40GPa and the temperature is 1500℃, the density of sintered sample is 93%. The shock pressure or shock time should be increased to improve the sintering quality. The results show that SHS-assisted shock sintering method is an efficient and low-cost preparation method for high hardness composite ceramics.

    Blunt Trauma Resistance of Graphene and Polyethylene-modified Aramid Fabrics under Ballistic Impact
    WANG Zhe, LIU Peng, CHEN Jing, HUANG Guangyan, ZHANG Hong
    2024, 45(1):  35-43.  doi:10.12382/bgxb.2022.0578
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    Aramid is widely used in the field of ballistic protection due to its light weight and high strength. In order to improve the trauma resistance of single-layer aramid fabrics, the surface modification methods of thermoplastic resin polyethylene (PE) and graphene nanoparticles (GR) are used innovatively to improve the ballistic performance of aramid fabrics. The trauma resistance and energy absorption of modified aramid fabrics with different mass ratios are studied based on the backface significance (BFS). The results show that both graphene and polyethylene modification methods can improve the blunt trauma resistance. The surface density of the modified fabric is increased slightly by polyethylene modification, but the resistance to blunt injury is significantly improved. Compared with pure aramid fabric, the bullet-proof ability and specific energy absorption value of 10% PE are increased by 18.0% and 30.8%, respectively. The increased rigidity of graphene-modified fabric increases its resistance to blunt injury at low speed, but the excessive inter-yarn friction weakens its resistance to blunt injury at high speed. 2% GR is the best ratio for graphene-modified fabric. In addition, the combined design of body armor with 2 layers of 10% PE and 13 layers of six layers of orthogonal UHMWPE unidrectional fabric is obtained through optimization and verification.

    Anti-penetration Performance and Damage Mechanism of Three-layer Composite Ceramic Armor
    YU Yilei, WANG Xiaodong, REN Wenke, GAO Guangfa
    2024, 45(1):  44-57.  doi:10.12382/bgxb.2022.0319
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    In order to investigate the effects of composite structural parameters of Kevlar/SiC-TC4-UHMWPE composite target plates with the same areal density on their anti-ballistic performances and their failure mechanisms,the samples of four different thickness combinations of target plates were selected,and the ballistic impact tests were conducted using 12.7mm armor-piercing incendiary (API) projectiles at the same impact velocity (488m/s). A scanning electron microscopy(SEM) was used to study the damage mode of composite armor plate under ballistic penetration. The experimental results show that the Kevlar/SiC-TC4-UHMWPE composite target plate with a thickness combination of 8mm+2mm+10mm under the described experimental conditions is the best structure for anti-penetration engineering. The anti-ballistic performance of the composite armor plate is improved by about 29.69% under the same areal density conditions when 1mm thick ceramic is replaced by a TC4 titanium alloy back plate (about 0.5mm thick) with the same areal density. This indicates that the structural parameters of titanium alloy have a greater impact on the anti-ballistic performance of the composite armor plate than those of SiC. In addition, the surface density of titanium alloy backplate is increased not only to enhance its support for ceramics, but also increase the time for projectile-target interaction, thus improving the overall protection performance of composite target plate. The damage mode of the composite armor plate after being penetrated by a 12.7mm API projectile includes SiC fragmentation, the small uplift deformation, “cross” stretching and tearing damage of titanium alloy back plate, and the shear fracture, interlayer separation and fiber stretching of UHMWPE composite fiber back plate. In the design of the overall composite armor, the high-shear resistant materials should be placed in the front layers of the back plate, while the high-tensile resistant materials should be placed in the back layers of the back plate in order to fully utilize each material.

    Experimental Research on the Characteristics of Behind-armor Debris from Explosively Formed Projectile Penetrating Targets of Different Materials
    HUANG Xuanning, LI Weibing, LI Wenbin, YIN Guixiang, GUO Tengfei
    2024, 45(1):  58-68.  doi:10.12382/bgxb.2022.0696
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    In order to study the effect of target material properties on the characteristics of behind-armor debris (BAD) generated by explosively formed projectile(EFP) penetration, the experimental research on the characteristics of BAD from EFP penetrating into the targets made of different materials, including Q235 steel, 45# steel, armor steel and 2A12 aluminum, was carried out. The morphology and expansion size of BAD cloud was observed by X-ray photography, and the fragment dispersion characteristics was obtained by arranging multi-layered witness fiber plates, meanwhile the BAD were recovered. The results show that, when the target material density is constant, the strength of the target mainly affects the axial expansion capacity of the debris cloud, but has little effect on the radial expansion capacity. The dispersion angle of annular damage region of BAD is in the range of 20°-25°, but the back surface of the target is spalled to cause a maximum value of dispersion angle. With the increase of the strength of steel target, the radial dispersion of BAD increases, the total number of fragments decreases, while the number of steel fragments in the large mass segment increases. The average size of steel fragments produced by steel targets with different yield strengths satisfies the fragment size model based on material flow stress proposed in Ref.[19].

    Protection Performance Analysis and Optimization Design of Vehicle Roof Sandwich Plateunder Air Explosion Condition of Fragment Warhead
    FU Yaoyu, GUI Xincheng, ZHOU Yunbo, LIU Jiazhi, SHI Hao, WANG Zheng
    2024, 45(1):  69-84.  doi:10.12382/bgxb.2023.0487
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    In modern warfare, many fragmentation warheads choose the top of vehicle as the preferred attack position to achieve long-range precision strike, but there is little research on the top protection of vehicle under the combined action of shock wave and fragmentation at home and abroad. In order to improve the protection performance of the top of special vehicle and realize the lightweight structural design, The effectiveness and accuracy of numerical simulation are verified by the NATO first-stage alternative charge explosion test and the theoretical calculation of fragment dispersion. A solution processing program for analyzing the fragment point distribution at different initiation heights is written by using Python according to the LS-DYNA analysis result data and the fragment ballistic equation. Then, an I-Y type sandwich plate is designed and compared with another five types of sandwich plates with different structures to prove its superiority. Further, The effects of explosive initiation mode, relative position of explosive, thicknesses of panel and backplane, and structural parameters of sandwich layer on the protection performance of I-Y plate are studied by taking the mass loss, energy absorption, peak displacement and fragment velocity distribution as evaluation criteria. Finally, the thickness of panel, the thickness of backplane, the height of sandwich layer and the width of cell are selected as the design variables, and the peak displacement of backplane and the quality of sandwich plate are taken as the optimization objectives. The optimal Latin Hypercube test method is used for sampling, Kriging method is used to construct the proxy model.and NSGA-Ⅱ genetic algorithm is used for multi-objective optimization. the optimal solution is simulated and verified, which provides support for the optimization design of roof protection structure under the combined action of shock waves and fragments.

    Study on Three-dimensional Rotating Detonation Flow Field Structures Based on Large Eddy Simulation
    LEI Te, WU Yuwen, XU Gao, QIU Yanming, KANG Chaohui, WENG Chunsheng
    2024, 45(1):  85-96.  doi:10.12382/bgxb.2022.0470
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    In order to study the characteristics of rotating detonation flow field in annular combustor and the effects of boundary layer, viscosity and turbulence simulation methods on the flow field structure, the open source computational fluid dynamics software OpenFOAM is used to simulate the three-dimensional model of rotating detonation engine (RDE) with hydrogen as fuel and air as oxidant. The characteristics of rotating detonation flow field obtained by Euler equation, large eddy simulation (LES) method and Reynolds-averaged Navier-Stokes (RANS) method are compared and analyzed. The flow field structure from LES simulation is emphatically discussed. The results show that the temperatures of flow fields in the inner, middle and outer sections exhibit no appreciable difference when the slip boundary is applied. However, when the no-slip boundary is utilized, the temperatures of the inner and outer walls are higher than that of the middle section, and the boundary layer will affect the flow velocity of gas in a region close to the wall. As a result, the height of detonation wave on the inner and outer walls is lower than that in the middle section. The boundary layer also affects the flow state of the combustion products, leading to the deformation of wave front on the axial section. The rotating detonation flow field structures obtained by different turbulence simulation methods are similar, indicating that the viscosity is the main factor affecting the rotating detonation flow field structure. The findings are highly significant in terms of elucidating the mechanism by which the viscosity and the boundary layer affect the rotating detonation process.

    A High Resolution DOA Method Based on Synthetic Virtual Array for Pulse Doppler Fuze
    WANG Xinwei, YAN Xiaopeng, HAO Xinhong, CHEN Qile, HUANG Dingkun
    2024, 45(1):  97-104.  doi:10.12382/bgxb.2022.0433
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    A DOA method based on synthetic virtual array is proposed to achieve a high direction-of-arrival(DOA) resolution forpulse Doppler(PD) fuze. Taking advantage of the motion characteristics of PD fuze, a largervirtual aperture array can be formed by combining the target echoes data at different moments. In order to solve the problem of high computational complexity caused by the non-uniformity of synthetic virtual array, the synthetic virtual array is decomposed into original subarray and moving subarray. After DBF processing, the wave beams of two subarrays is used to replace the wave beam the synthetic virtual array, which not only obtains the high angle resolution, but also reduces the complexity of direct DBF operation of synthetic virtual array. The simulated and experimental results show that the proposed method can be used to improvethe DOA resolution of PD fuze under the condition of fewer array elements.

    Numerical Investigation of the Jet Interference Characteristics of a Lateral-jet-controlled Spinning Missile
    LEI Juanmian, GAO Yi, YONG Zheng
    2024, 45(1):  105-121.  doi:10.12382/bgxb.2022.0379
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    In this study, a supersonic jet issued from a spinning missile into a supersonic freestream is numerically simulated. The 3D compressible unsteady Navier-Stokes equations and the sliding mesh method are utilized to simulate the flow field numerically. The effect of spinning motion on missile lateral jet control efficiency is studied, and the variation rules of aerodynamic characteristics of spinning missile under different conditions are given. The influence of lateral jet on the aerodynamic characteristics of spinning missile was analyzed. The results show that the spinning leads to the deflection of jet interference force and control force, and the deflection angle increases with the increase of spin rate. At small angle of attack, the additional lateral force and yaw moment coefficient caused by jet interference effect are one order of magnitude larger than those caused by Magnus effect. With the increase of angle of attack, the proportion of lateral force and yaw moment coefficient caused by Magnus effect in the whole missile increases, and the additional lateral force and yaw moment coefficient caused by jet decreases. The aerodynamic coefficients in the lateral jet control sector of the spinning missile vary with the rolling angle with strong unsteady characteristics. When the angle of the jet control sector is small, the time-averaged lateral aerodynamic characteristics are close to the transient lateral aerodynamic characteristics at the rolling angle of the symmetric surface. The time-averaged lateral force coefficient and time-averaged yaw moment coefficient with jet at different sector angles are much larger than those without jet.

    Heat Transfer and Flow Characteristics of Open-cell Metal Foams
    LI Jing, SUN Xiaoxia, MA Xinglong, ZHU Wenxiang
    2024, 45(1):  122-130.  doi:10.12382/bgxb.2022.0482
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    In recent years, the application of open-cell metal foams in heat dissipation equipment has gradually become a research hotspot. Its structure is generally simplified in numerical simulation due to its complex and disordered structure. At present, there are a variety of simplified models, but the simplified models suitable for the simulation of heat transfer and flow characteristics are not clear. In addition, the structural parameters of metal foam suitable for heat dissipation need to be studied in detail. Therefore, five simplified 3-D models of open-cell metal foams are established, and the heat transfer and flow characteristics are compared to conclude that Gibson-Ashby model can describe the heat transfer and flow characteristics of open-cell metal foams more accurately. On this basis, Gibson-Ashby model is used to analyze the heat transfer and flow performance of open-cell metal foams. The results show that the comprehensive performance j/f1/3 of open-cell metal foam fins with 90% porosity and 30PPI pore density is the best. Comparing the open-cell metal foam fins with porosity of 90% and pore density of 30PPI with the flat fin, the results show that the heat transfer effect of open-cell metal foam fins is more than two times that of the flat fin, and its comprehensive performance is better than that of the flat fin. The research results can provide reference for the application and design of open-cell metal foams in heat transfer field.

    Peak Elimination Effect of Radial Uncoupled Charge on Explosion Pressure and Its Influence on Rock Fracture Range
    FAN Yong, WU Fan, LENG Zhengdong, YANG Guangdong, ZHAO Xiaohua
    2024, 45(1):  131-143.  doi:10.12382/bgxb.2022.0431
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    Understanding the law of rock fracture induced by single hole blasting is the basis to reveal the mechanism of rock fracture induced by multi-hole blasting. The mechanism of rock fracture induced by single hole blasting is clarified theoretically, and then the change process of stress, the propagation process of crack and the sizes of rock crushed zone and cracked zone with the decoupling coefficient of 1-3.5 are simulated by using a high explosive model and a rock RHT model. The laws of variation of the peak value of blasting pressure on the blast hole wall and the ranges of crushed zone and cracked zone with the increase in decoupling coefficient are analyzed. Calculated results show that the air-decoupling charge structure has about 2 times the peak shaving effect on the blasting pressure than the water-uncoupled charge structure due to the influences of different decoupling media. With the increase of decoupling coefficient from 1 to 3.5 (unchanged charge diameter), the diameters of crushed zone and cracked zone for the air-decoupling charge structure ranges from 4.44 to 1.59 and 22.5 to 7.62 times hole diameter, respectively. While for the water-decoupling charge structure, the diameters of crushed zone and the cracked zone are 4.44 to 2.74 times and 22.5 to 10.67 times more than hole diameter, respectively.

    Experimental and Numerical Investigation on the Damage Effects of Concrete Pier under Contact Explosion
    KANG Gengxin, YAN Haichun, ZHANG Yadong, LIU Mingjun, HAO Likai
    2024, 45(1):  144-155.  doi:10.12382/bgxb.2022.0397
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    The damage effects of concrete pier under the action of contact explosion are studied. Firstly, the K&C, HJC, RHT and Kong-Fang models are respectively used to numerically calculate the failure effects of concrete pier. The failure modes, the number of cracks, the number of broken blocks and the change in residual heights of core and side are discussed and compared with the test results. The results show that the four models can effectively predict the failure modes of concrete pier: the upper half and lower half of concrete pier show different failure modes under the explosion of the top group charge. The upper half is broken and damaged to form a large number of fragments ranging from 1cm to 10cm in diameter, and the lower half is ruptured to be cracked into a limited number of blocks. Kong-Fang model can more reliably predict the number and residual heights of broken blocks. On this basis, the variation of damage characteristic parameters of residual blocks with the charge volume was studied. It is found that, with the increase in the charge from 1.0kg to 4.5kg, the number of broken blocks increases to 25 pieces, and the size of the bottom surface of a block decreases from 40cm to 15cm, which is about 1/5-1/25 of the size of concrete pier in the broken part. The core residual height and side residual height decrease rapidly when the charge volume increases from 1.0kg to 3.5kg, and are stabilized at 40cm and 28cm, respectively, after the charge of 4kg, and no longer changed significantly. Based on the above research results, the formulas for the changes in the number of blocks, the residual height of the core and the residual height of the side are fitted. The research in this paper provides a basis for the effective implementation of concrete pier blasting operations.

    A SLAM in Dynamic Environment Based on Instance Segmentation and Optical Flow
    YUE Shengzhe, WANG Zhengjie
    2024, 45(1):  156-165.  doi:10.12382/bgxb.2023.0568
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    A visual semantic SLAM algorithm based on instance segmentation and optical flow is proposed to address the issue of excessive removal of features by traditional semantic SLAM algorithms in dynamic environments.The proposed algorithm utilizes a Mask R-CNN network to perform the instance-level segmentation of potential dynamic objects in an image, and also identifies and eliminates dynamic objects in the optical flow thread. The remaining static optical flow points and static feature points are then used to optimize the location estimation process, ensuring the optimal utilization of both semantic and optical flow information. The proposed algorithm is validated through testing on open datasets and an unmanned ground platform experiment. The experimental results indicate that the average error of the proposed algorithm is 75% and 8.5% lower than those of ORB-SLAM2 and Dyna-SLAM, respectively, on TUM dataset.

    Trajectory Tracking and Obstacle Avoidance Control of Six-wheel Independent Drive and Steering Robot in Complex Terrain
    LIU Jiangtao, ZHOU Lelai, LI Yibin
    2024, 45(1):  166-183.  doi:10.12382/bgxb.2023.0533
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    In order to study the motion control method of six-wheel mobile robot in complex terrain environment, a predictive control and dynamic compensation control method is proposed for the trajectory tracking problem of six-wheel independent drive and steering robot in complex terrain. This method is based on the nonholonomically constrained linear six-wheeled mobile robot kinematics model and the model predictive control algorithm, and introduces a proportional-integral-derivative compensation controller to suppress the tracking error caused by dynamic hysteresis. Coping with the effect of terrain disturbance on trajectory tracking. the collision avoidance problem of obstacles in the process of robot movement is analyzed, an obstacle avoidance planner that can solve the obstacle avoidance trajectory is designed to track and control the local obstacle avoidance trajectory through the trajectory tracking system, thus realizing the trajectory tracking and automatic collision avoidance of robot, and the trajectory tracking algorithm and obstacle avoidance algorithm were simulated experiments. The experimental results show that the robot can complete the sinusoidal trajectory tracking control and the static and dynamic obstacle collision avoidances in concave slope, convex slope and uneven terrain under typical working conditions, which verifies the effectiveness of the method.

    Tracking Control of Underactuated Autonomous Underwater Vehicle Formation under Current Disturbance and Communication Delay
    DING Wengjun, ZHANG Guozong, LIU Haimin, CHAI Yajun, WANG Chiyu, MAO Zhaoyong
    2024, 45(1):  184-196.  doi:10.12382/bgxb.2023.0417
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    The underwater detection array composed of underactuated autonomous underwater vehicle (AUV) formation has the fast response, good maneuverability, and high intelligence. For the formation control problem of multi-autonomous underwater vehicles without speed information transmission under the combined disturbance of current and time delay, a formation control method which combines the virtual trajectory, trajectory prediction, and adaptive inversion sliding mode control technique is proposed. The position information of navigator and the expected formation are used to obtain the reference trajectory of follower, and introduce a virtual trajectory to make it coincide with the reference trajectory for a finite time, thereby obtaining the expected position and velocity of the follower. On this basis, the least squares method is used to fit the trajectory curve to compensate for the delay, and to complete the formation trajectory tracking under the interference of current through the adaptive backstepping sliding mode control technology. The theoretical analysis and simulated results indicate that the designed method is feasible and effective.

    Interference Characteristics and Launch Sequence Optimization of Projectiles Launched Successively Underwater
    LIU Fang, XIAO Jinshi, WEI Jianming, ZHANG Zhiyang, WANG Cong
    2024, 45(1):  197-205.  doi:10.12382/bgxb.2022.0576
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    With the increasing demand for saturation attacks, the research on the optimization of launch sequence of projectiles launched successively underwater has become important and urgent. Considering that the hydrodynamic interferences between two underwater projectiles are the main factor affecting launch safety, this paper studies the interference characteristics of projectiles launched successively underwater based on the overlapping mesh methods. By analyzing the flow field, it is found that the hairpin vortices formed by the projectile with an angle of attack are the main reason leading to the attitude difference between two projectiles. An interference evaluation model is established according to the interference between the projectiles under the conditions of different transport speeds, time intervals and space intervals. To ensure that the former projectile interferes little with subsequent projectiles, the launch sequence of projectiles fixed at a launch tube is optimized based on the improved greedy algorithm, in which the shortest launch duration is taken as the goal and the comprehensive evaluation function as the constraint. The uniform sampling method is used to verify the accuracy of the optimized results. The results show that the improved greedy algorithm has comparable accuracy and higher efficiency compared with the uniform sampling method.

    Simulation of Falling-floating Process of Vehicle with Ellipsoidal Airbags
    BAO Jian, MA Guihui, SUN Longquan, CHEN Weichu, LI Ming
    2024, 45(1):  206-218.  doi:10.12382/bgxb.2022.0503
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    A recovery scheme of vehicle with ellipsoidal airbags is proposed for the problem of model falling into the water at low speed in the underwater launch model test. The numerical simulation is based on Abaqus coupled Eulerian-Lagrangian method, and the effectiveness of the numerical method is verified by comparing the numerical and experimental results of the AUV head section entering into the water. The motion process of the vehicle with airbags entering the water at low speed, the change of airbag pressure and the force of the connecting belt under the conditions of different attitude angles and different initial airbag pressures are analyzed. The results show that the attitude angle of vehicle is the most important factor affecting the falling-floating process, followed by the initial airbag pressure. For the maximum depth of falling into the water, the peak value of airbag pressure and the peak value of pulling force, the condition that tends to fall vertically is more dangerous, the maximum depth of falling into the water is 1.33 times the length of vehicle, the maximum airbag pressure is 3.7 times the baseline airbag pressure, and the maximum pulling force of connecting belt is 2.2 times the gravity of vehicle. These conclusions can provide a reference for the design of recovery scheme and structural parameters for the vehicles falling into the water.

    Research on Safe Separation Mechanism of UAV Rocket Booster
    ZHOU Yue, LI Zhuangzhuang, ZHENG Ranshun, LI Jun
    2024, 45(1):  219-230.  doi:10.12382/bgxb.2023.0362
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    A UAV rocket booster which can be separated automatically and safely is proposed to improve the separation safety of booster mechanism of rocket-propelled UAV during take-off. Taking a UAV as an example, a theoretical model of UAV booster with the goal of optimal separation safety is established by using theoretical mechanics and rigid body kinematics knowledge. The design basis of the key parameters in the booster is obtained, and a three-dimensional model of booster is established. The separation trajectory of the improved separation mechanism is obtained by using the rigid body dynamics analysis method. An experiment system including the booster and the simulated UAV part is established to verify that the separation trajectory and attitude of the booster have the same changing trend with the simulation structure. The results show that the booster can effectively avoid the hidden danger in the process of separation, and improves the safety of the booster mechanism separation.

    Robust Adaptive Fault-tolerant Attitude Control of Flying-wing UAVs with Flight Envelope Constraints
    YU Zhilong, LI Yinghui, PEI Binbin, XU Wenfeng, DUAN Xiaocong, SONG Kexin
    2024, 45(1):  231-240.  doi:10.12382/bgxb.2023.0351
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    To realize the accurate attitude tracking control of flying-wing UAVs in complex circumstances, a robust adaptive fault-tolerant control method based on Nussbaum gain is proposed considering the effects of parameter uncertainties, external disturbances, actuator failures and flight envelope constraints. Based on the disturbed kinematic and dynamic models of a flying wing UAV, a control-oriented attitude control model is developed considering the effects of actuator faults and system uncertainties. The flight envelope constraints and the transient and steady-state performances of attitude tracking errors are ensured by introducing a time-varying barrier Lyapunov function. Then, the effect of lumped uncertainty term and the actuator faults are compensated by adaptive bounded estimation and Nussbaum gain. Finally, the feasibility of the proposed control method is critically demonstrated though stability analysis. The simulated results show that the proposed control method is able to achieve the high-precision attitude tracking control of the flying-wing UAV.

    Electric Landing Assist Device of Shipborne Helicopters and Its Key Characteristics Analysis
    LIU Qian, ZHANG Zhuxin, ZHAO Dingxuan, WANG Hui, QIN Zhanyong
    2024, 45(1):  241-252.  doi:10.12382/bgxb.2022.0523
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    An electric landing assist device for shipborne helicopter is designed to address the problems of significant capture impact and high energy consumption of aircraft ship integrated secure and traverse(ASIST) system. The performance requirements of landing assist device during the capture and transshipment tasks are presented by analyzing the working conditions. According to this, a transmission scheme of electric landing assist device is proposed. A dynamics model of the transmission system is established based on the theory of power bond graph; The proposed dynamics model is compared with the hydraulic landing assist device through the simulation test. The results show that the capture speed is reduced by about 92%, and the maximum impact force is reduced by about 94%. The electric landing assist device can execute the helicopter transshipment tasks with an external load of 21kN and reduce energy consumption by about 29%. These research achievements are of great significance for broadening the application scope and reducing the energy consumption of ASIST. In addition, the introduced modeling method, which considers both the dynamic and energy consumption characteristics, also provides a reference for the dynamic modeling of other complex mechanical systems.

    A Gas Path Fault Diagnosis Method for Aero-engine Based on TCN-LGBM Model
    LÜ Weimin, SUN Chenfeng, REN Likun, ZHAO Jie, LI Yongqiang
    2024, 45(1):  253-263.  doi:10.12382/bgxb.2022.0615
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    With the obvious characteristics of poor temporal logic in fault diagnosis and the strongly coupled feature parameters, the aero-engines working in the hostile gas path conditions of high temperature, pressure and strong vibration face with the degradation performance and structure defect problems such as fatigue and corrosion. And an aero-engine gas path fault diagnosis method based on temporal convolutional networks(TCN) and light gradient boosting machine(LGBM) is proposed to provide a feasible solution to the problems above. The diagnosis process can be divided into feature extraction and classification: TCN is introduced to guarantee the fault diagnosis training temporal logic and achieve the features fusion of distant layers and current layers, which is also strengthened by channel attention mechanism; the features are quickly classified based on LGBM model, and the Bayesian method is used to quickly optimize the model hyperparameters. Based on the aero-engine performance modelled by PROOSIS software, six types of fault mode are diagnosed and identified by taking a military low-bypass ratio turbofan engine as an example. The results indicate that the proposed model is effective for fault diagnosis and shows the superiority by comparing with other models.

    Coordinated Control Strategy for Improving the Starting Performance of Heavy Vehicle
    SHANG Xianhe, ZHANG Fujun, LÜ Hang, LIU Tao, HAN Xuefeng, WANG Miqi
    2024, 45(1):  264-275.  doi:10.12382/bgxb.2023.0340
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    For the problem of poor starting response of heavy vehicles, a simulation model of the exhaust turbocharged diesel engine and control system is established using GT-SUITE software based on the structure of the vehicle powertrain system. The simulation model is verified through bench test, ensuring that the powertrain system model has high simulation accuracy. Through simulation, the influences of smoke limit and coupling working point of hydraulic torque converter on starting acceleration performance are explored, and the mechanism of the coupling characteristics of engine and hydraulic torque converter on the improvement of vehicle starting performance is clarified. A vehicle starting coordinated control strategy is developed to improve 0-32km/h acceleration performance of vehicle. The proposed coordinated control strategy is simulated and verified based on the established power transmission system simulation model. The results show that the starting time of vehicle to accelerate from 0km/h to 32km/h is 9.8s when the proposed coordinated control strategy is used, while the time for conventional starting vehicle to accelerate from 0km/h to 32km/h is 14s. The proposed coordinated control strategy has a significant effect on improving the starting acceleration performance of heavy vehicle.

    Disturbance Compensation Strategy for Fifth-order Joint Servomechanism Based on Characteristic Model
    ZHANG Tianyi, ZHENG Ying, QIU Xinguo, JI Xingjian, JIN Xiaohang
    2024, 45(1):  276-287.  doi:10.12382/bgxb.2022.0941
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    A control strategy combining the linear extended state observer and full coefficient adaptive control based on characteristic model is proposed for the time-varying load and model uncertainties of industrial robot joint servomechanism. A two-inertia flexible joint dynamics model is established, and the equation of the fifth-order extended state of joint servomechanism was obtained. A fifth-order linear extended state observer is designed based on the model, through which the total disturbance of the system is estimated and compensated, and the convergence of the observer is proved. Based on the method of characteristic modeling, the characteristic parameters are identified by experimental data and gradient descent method, and the full coefficient adaptive control law is designed based on the parameter values. A control strategy is designed to accurately control the system by combining the control law with the linear extended state observer. The experimental results show that the proposed control strategy is used to make the positioning accuracy of the system reach 0.003° under the condition of variable load disturbance and the sinusoidal signal tracking error keep within 0.92°. The system has strong robustness and control accuracy.

    Analysis of the Influence of Soil on the Maneuverability of Military Off-road Vehicles
    XIAO Wangang, ZHOU Yunbo, FU Yaoyu, ZHANG Ming, ZHOU Jun, GE Jitao
    2024, 45(1):  288-298.  doi:10.12382/bgxb.2022.0528
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    Maneuverability on soft ground is one of the main performances of military high-mobility off-road vehicle, and has important strategic significance for its field operations. In order to explore the influence of different soft soil surface conditions on the maneuverability of off-road vehicles, the soil is modeled based on the discrete element method, and the soil stiffness calibration test is carried out through the soil accumulation angle test and soil conical index test. Through the DEM-MBD co-simulation method, the accurate soil model is used to simulate and analyze four different types of soil: incompressible dry soil, incompressible wet soil, compressible dry soil, and compressible wet soil. The influence of soil type on the maneuverability of off-road vehicles is analyzed by comparing the average speed, traction force, driving torque and tire subsidenceof off-road vehicles.The traction ofoff-road vehicle on wet soils is 6.98% less than on dry soils, and its stable travel speed on incompressible soils is 34.2% higher than that on compressible soils, and its speed is more stable on wet soil roads. The research makes up for the gap in the influence of soil on the mobility of the whole vehicle in the field of ground mechanics of domestic vehicles, and can choose the optimal driving road surface for military vehicles in the field of complex terrain,such as sand, snow, mud, etc.,to improve combat efficiency.

    Dynamic Deflection Response of Typical Pavement Structure under Different Impact Loads
    JI Xinbo, LU Weijian, LÜ Chen, WANG Xi, LIAN Zheng, HE Li
    2024, 45(1):  299-311.  doi:10.12382/bgxb.2022.0413
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    In order to study the numerical law of dynamic deflection response of typical pavement structure under different impact loads, the grade highway information is experimentally surveyed, the measured data is analyzed, the correlation between grade highway bearing capacity and pavement structure is summarized, and the typical pavement structure under the dimension of bearing capacity is constructed based on the statistical law. And then a multi-layer continuous road structure model including plastic damage is established. The effectiveness of the model is verified by comparing the simulation results with the experimental data, and the influence of the size of the model on the simulation results of pavement deflection under different impact loads is studied. Finally, the deflection response law of typical pavement structure under different impact loads is studied, the peak settlement and residual settlement of pavement under impact load are calculated, and the internal law of deflection response of typical pavement structure under different impact loads is revealed. The result shows that the multi-layer continuous road structure model including plastic damage can accurately reflect the real dynamic deflection response of pavement under impact load; under different impact loads, the proportion of plastic settlement in pavement settlement and the amplitude of impact load meet the double exponential equation; in the range of 100 tons, the elastic rebound part of pavement settlement increases with the increase of impact load amplitude, and the plastic settlement part has an exponential positive correlation with load amplitude; the elastic rebound in pavement settlement reaches the upper limit of 1.2-1.3mm above 100 tons, the plastic settlement of pavement has a linear relationship with the load amplitude. In addition, the research on the influence of model size on simulation results under different impact loads can provide a reference for determining the appropriate size of simulation model in finite element simulation.

    Design and FPGA Implementation of VDES Demodulation System Based on Decision Feedback Algorithm
    SUN Dingzhu, FENG Man, DI Fang, CHEN Peng
    2024, 45(1):  312-318.  doi:10.12382/bgxb.2022.0471
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    VHF data exchange system (VDES) has broad application prospect as a new generation of ship communication system. Due to the high-speed motion of satellite, a large Doppler frequency shift is superimposed on the ASM uplink in VDES, and the channel parameters estimated only by training sequence in receiving end cannot meet the requirements of demodulation. Therefore, a VDES demodulation system based on decision feedback algorithm is proposed. The received data is split into small segments, which reduces the influence of frequency offset. The demodulated result of each segment is used as pilot to estimate the channel parameters in current data segment. Simulated results show that the performance of the proposed algorithm is superior to that of the coherent demodulation algorithm without feedback. On the basis of the above research, the correct demodulation of ASM uplink without pilots is implemented on the filed programmable gate array(FPGA).

    Influence of Distributed Capacitance on Information Transmission Characteristics of Collinear Setting System of Fuze and Its Optimization
    LI Hao, LI Haojie, YUAN Hongwei, YUE Zhonghao, MA Haitao
    2024, 45(1):  319-327.  doi:10.12382/bgxb.2022.0406
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    An equivalent circuit model based on the setter module, the energy and information transmission module and the fuze circuit module is established for the effect of distributed capacitance on the setting reliability in the process of fuze collinear setting. The influences of distributed capacitance on the information transmission characteristics of collinear setting systemwhen the setting output signal is at high level and low level are studied, respectively. The conclusion is drawn that the distributed capacitance has little influence on the collinear installation system at high level, and the relationship between the low-level pulse width of the received signal recognized by the fuze and the distributed capacitance at low level is deduced. Finally, two optimization methods are proposed, one uses a diode to shield the external factors, such as the capacitance introduced by the incorporated cable, and the other uses a parallel-connected resistor with a smaller resistance to reduce the time constant of the system, thereby improving the recognition rate of the fuze. The low-level pulse width improves the reliability of fuze setting. The simulation and experimental verification show that both methods improve the reliability of the fuze to identify the received signal.

    Capability Evaluation of Air Defense and Anti-missile Early Warning System-of-systems Based on Node Importance and Improved Effectiveness Loop
    YU Jintao, XIAO Bing, CUI Yuzhu
    2024, 45(1):  328-338.  doi:10.12382/bgxb.2022.0488
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    A capability evaluation method of air defense and anti-missile early warning system-of-systems (SOS) based on the node importance and improved effectiveness loop (EL) is proposed to address the problems in the capability evaluation of air defense and anti-missile SOS, such as weak realism, less consideration of heterogeneous characteristics and incomplete calculation of capabilities. The structure of the SOS is abstractly modeled based on the super-network model, and a more realistic EL model is proposed. The importance of nodes is calculated from the global and local aspects of the network. Then the effectiveness edges are analyzed according to the mutual influence relations among nodes. In addition, the capability expectation of the SOS is presented to improve the evaluation method by combining the node importance and reliability with the capability of the edge. Finally, the feasibility and rationality of the method are verified through the simulation analysis of anti-missile early warning combat example. The proposed method fully takes the realistic characteristics of the air defense and anti-missile early warning SOS and the heterogeneous features of the equipment into account, and can assess the capability of SOS in a more comprehensive manner, which provides theoretical support for the capability evaluation and structural optimization of SOS.

    Bayesian Estimation of Surface-to-Air Missile Hit Probability Based on Normal-inverse Wishart Distribution
    LIU Haobang, SHI Xianming, ZHAO Mei, ZHANG Jianjun
    2024, 45(1):  339-348.  doi:10.12382/bgxb.2022.0547
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    The two-dimensional normal projectile dispersion is mainly used in the existing Bayesian estimation of missile hit probability, but the accuracy of estimation is not high enough due to the failure of considering the two-direction correlation of X and Y axes. The normal-inverse Wishart distribution is used as the prior distribution of projectile dispersion parameters, and the hit probability estimation method of surface-to-air missile is studied.Firstly, on the basis of describing the definition of miss distance of surface-to-air missile, the correlation coefficient ρ is determined by two related characteristics.Secondly, in view of the problems of high cost, little dataof the surface-to-air missile field test, and the difficulty of estimating hit probability by classical statistical methods, the Bayesian method is used to integrate the prior informationfor research. Then, based on the normal-inverse Wishart distribution, the prior information is used to solve the hyperparameters of the prior distribution, and the posterior distribution of projectile dispersion parameters are obtained by integrating the field test data with the Bayesian formula, and finally the hit probability of surface-to-air missile is estimated. The results show that, compared with the existing normal-inverse gamma distribution method, the proposed method take into account the actual situation of the projectile dispersion two-direction correlation of surface-to-air missile, and makes full use of the hit probability information, which is conducive to improving the accuracy of estimation,and provide a theoretical method for the estimation of surface-to-air missile hit probability.

    Evaluation Method for Dynamic Effect of Camouflage Based on Battlefield Environment Twinning
    YANG Di, ZHOU Ying, XIE Zhenping
    2024, 45(1):  349-362.  doi:10.12382/bgxb.2022.0378
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    The existing evaluation methods for camouflage effectare mainly based on static single target images, which cannot truly respond to the dynamic multi-view characteristics in military reconnaissance, and the corresponding evaluated results are lack of comprehensiveness. A new evaluationmethod fordynamic effect of camouflage based on battlefield environment twinning is proposed. In the new method,a digital twin model of 3D battlefield environment is established, the dynamic multi-view effect map of camouflage targets in the battlefield environment is acquired with the help of 3D simulation and computing technology, the camouflage motion targets in the scene are identified and analyzedby using semantic segmentation and target tracking model, and a new camouflage evaluation index system and a multi-attribute comprehensive evaluation model with multiple reconnaissance views are constructed, finally realizing the dynamic multi-view effect evaluation of different camouflage schemes. The experiments were conducted with simulated military truck model as the experimental object, Unity 3D was used to model the real battlefield environment, and two contrasting camouflage design schemes were evaluated and analyzed. The experimental results show the reasonableness and practicality of the new method.