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Simulation Analysis of Strain Concentration Effect in Rigid-Flexible Coupling System of Tethered Balloon
WU Jun;LUO Haibo;YANG Yanchu;MA Zifei;LIU Xiaoyong;To address the strain concentration caused by a rigid-flexible coupling connection between a tethered balloon and compartment, a mechanical analysis was conducted by combining ABAQUS with theoretical models. A strategy for strengthening the transition layer was proposed to effectively reduce the strain concentration at the structural connection, thereby enhancing the safety and practicality of the tethered balloon system. First, based on the classical mechanical theory, a theoretical solution for stress distribution of the bladder structure of the tethered balloon was obtained, and a design criterion for the orthogonal modulus of fabric materials was proposed in combination with constitutive equations. Subsequently, the calculation results of the mechanical simulation model of the rigid-flexible coupling system were analyzed, and an equivalent strain concentration factor was introduced. The influence mechanisms of additional heavy-load mass, internal-external pressure difference of the bladder, and material on the strain concentration effect were investigated. Finally, to alleviate the strain concentration effect, a locally thick-ened bladder transition layer design strategy was proposed. Simulation results show that for tethered balloons without compartment, the circumferential stress is approximately twice the axial stress, making anisotropic fabric materials with an orthogonal modulus ratio of two more suitable. Using Vectran fiber composites as the bladder base material and carbon fiber as the compartment structural components yields the best overall load-bearing capacity. Under a 1-ton heavy load, the strain concentration factor of the rigid-flexible coupling system of the tethered balloon with the reinforced transition layer design decreases by 11.3%, effectively improving the load-bearing capacity and structural reliability of the tethered balloon. The proposed optimization strategy can provide theoretical guidance for the design of new types of aerostat systems in future, and promote the safe application of tethered balloons.
Design and Application Prospects of a Novel Low-Cost Polyethylene Airship
ZHANG Hangyue;ZHAO Rong;CAO Shenghong;ZHU Rongchen;YANG Yanchu;CAI Rong;To effectively address the contradiction between the volume versus weight divergence and temperature versus strength divergence of stratospheric fabric airships, a streamlined airship architecture with linear low-density polyethylene membrane was proposed. Based on the advantages of polyethylene airships in terms of lightweight, pressure tolerance, and low cost, researches focused on the design of super-pressure resistant structures, tail fins and launching methods. First, an orthogonal tendons-membrane coupled model was established to consider the twodimensional generatrix deformation under lateral constraints as input, to obtain the optimal circumferential tendons spacing. The global deformation and local bulge of a single gore after applying symmetrical constraints were analyzed to obtain the bulge shape and stress after the local curvature radius reduction. Subsequently, a multi-airbag stacked tail fin was designed to achieve a super-pressure-resistant polyethylene structure through transverse, longitudinal, and vertical tendons. Finally, an internal interlayer and external rope cage scheme were adopted to address the difficulties of achieving non-forming launching of polyethylene airships, and its feasibility was verified through field flight experiments. Future research can focus on the realization of mid-to-upper stratosphere flight, combination balloons, high-altitude tethered balloons, and low-altitude economy, providing low-cost and scalable technological paths for related applications.
Prediction Method of the Coefficients of Thermal Expansion of Short-Fiber-Reinforced Composites
GUAN Tao;LIU Quanxiu;GUO Fangliang;LI Yuanqing;FU Shaoyun;To accurately evaluate the thermal-expansion property of short-fiber-reinforced composites, a predictive model for the coefficient of thermal expansion(CTE)was developed.The model was based on an analytical solution for unidirectional laminates derived from thermodynamic theory and incorporated orientation and length probability density functions. First, the effects of fiber distribution characteristics, such as mean orientation angle, mean length, and volume fraction, on the CTE were systematically investigated using this model. Subsequently, shortfiber-reinforced composites were fabricated using extrusion injection, solution injection, and suspension injection moldings. The fiber orientation distribution was quantified using image analysis,and the fiber length distribution was determined via pyrolysis. Finally, the resulting data were input into the model, and the predicted CTE values were validated using experimental data. The results show that the longitudinal CTE decreases with increasing mean aspect ratio and volume fraction but increases with increasing mean orientation angle, whereas the transverse CTE decreases with increasing mean orientation angle and volume fraction yet increases with increasing mean aspect ratio. The mean orientation angle and volume fraction exert significantly stronger influences on the composite CTE than the mean aspect ratio. Both the mean orientation angle and mean fiber length decrease as the fiber volume fraction increases. The mean fiber length of the extrusion injection-molded specimen is 107.9 μm, while those of the solution injection and suspension injection molded specimens are 139.0 μm and 206.6 μm, respectively. The excellent agreement between the theoretical predictions of the proposed model and the experimental results demonstrates the reliability of the model and provides effective guidance for the optimal design of short-fiber-reinforced composites.
Two-Layer Formation Tracking Control of Quadrotor Unmanned Aerial Vehicle Swarms under Intermittent Communication
GAO Jiuan;LI Bing;XI Jianxiang;WANG Le;WANG Cheng;First Military Representative Office of the Rocket Force Equipment Department in Mianyang;A dual-layer time-varying formation tracking control method for quadrotor unmanned aerial vehicle(UAV)swarms under intermittent communication was proposed to address the challenges posed by complex communication constraints among UAVs. First, the intermittent communication condition was mathematically described, and a quadrotor UAV model was established. The conditions for achieving dual-layer time-varying formation-tracking control in quadrotor UAV swarms were then derived. Subsequently, an intermittent dual-layer time-varying formation-tracking controller was designed, and a design and analysis criterion under intermittent communication was introduced based on linear matrix inequalities. Finally, simulation experiments were conducted using a multi-leader quadrotor UAV swarm system comprising three leaders and six followers. The results demonstrate that the swarm system can achieve a dual-layer time-varying formation-tracking control under intermittent communication. When communication is connected, both leaders and followers can form their desired time-varying formations, with followers tracking the formation center determined by the leaders. When the communication is interrupted,the self-feedback term of the controller ensures that the UAVs remain controllable. The simulation results verify strong formation and tracking performance of the proposed method.
Short and Medium-Term Prediction of Satellite Clock Bias Combining Grey Model and First-Order Weighted Local Method
YU Ye;YANG Chaopan;JIN Guodong;ZHAO Jianwei;A method for satellite clock bias(SCB)prediction combining the grey model and first-order weighted local method was proposed to improve the accuracy and stability of SCB prediction based on a single model. First, a db1 wavelet was used to perform a three-layer multiscale decomposition and single-branch reconstruction of the SCB, obtaining an approximate component and three detailed components. Subsequently, the grey model was adopted to predict the approximate components, and the first-order weighted local method was used to predict the detailed components, respectively. Finally, the predicted values of all components were added to obtain the final predicted value of the SCB. The clock bias data of ten Galileo satellites were randomly selected for prediction experiments using precision SCB products released by the GNSS Analysis Center of Wuhan University. The results show that in the 2 h, 4 h and 6 h predictions,the prediction accuracy of this combined model increases by 50.00%, 64.66% and 60.48%, respectively, while the stability increases by 18.07%, 23.19% and 32.51%, respectively, compared with those of the grey model. When the amount of modeling data and prediction length were changed, the prediction accuracy and stability of the combined model are significantly improved compared with those of other single models. Its prediction accuracy and stability can be increased by up to 83.12% and 86.28%, respectively. Thus, the effectiveness and feasibility of the combined model for SCB prediction are verified.
Damage Identification of Cylindrical Shell Structures Based on Fractal Characterization of Vibration Modes
SHI Binkai;WANG Xinfeng;GUO Jianfeng;YANG Zhengwei;SHI Shihao;YANG Dexin;A damage identification algorithm based on fractal characterization of vibration mode shapes was proposed to address the weak positioning capability and poor damage resistance in the original parameter arrays of vibration modes. First, a contour map was constructed using the fractal dimension of the longitudinal line vibration modes of a cylindrical shell to intuitively characterize the location and degree of damage and approximate its shape. Subsequently, the effectiveness and feasibility of the algorithm were verified using a numerical model of the cylindrical shell under free boundaries. Comparisons with commonly used curvature detection algorithms demonstrated that the proposed high-dimensional fractal algorithm exhibits significantly better noise resistance and robustness in different noise environments. Finally, the algorithm was applied to the experimental modal testings of metal cylindrical shells with artificially notched damage, using force hammer excitation and accelerometer measurements. The results show that the proposed algorithm can effectively identify the damage in the experimental mode, achieving a positioning accuracy within ±1 measuring-point spacing range. The applicability and effectiveness of this algorithm in practical engineering are verified.
Intelligent Decision-Making Methods Based on a Multidimensional Evaluation Model
XIONG Jingyi;QIN Weiwei;FENG Qian;HU Weijun;MA Xianlong;Rocket Force University of Engineering;To solve the optimization problems in evaluating cooperative combat effectiveness of hypersonic missiles, a multi-wave intelligent decision-making method based on a multidimensional evaluation model was proposed. First, a composite evaluation system that incorporated four dimensions, namely missile damage probability, defense and interception probability, offensive and defensive efficiency advantages, and space situation advantages, was constructed. Second, in response to the requirements of anti-ship operations, a mission decision-making model was established with the target damage probability and threat degree as optimization goals. The genetic algorithm-based particle swarm optimization(GAPSO), which was suitable for single-wave and multi-wave coordinated strikes, was used to optimize firepower allocation. The performance of traditional algorithms was improved through dynamic threat assessment, adaptive weight adjustment, and a global optimal solution protection strategy. Finally, the algorithm was validated using a typical naval battlefield scenario as an example. The results show that GAPSO significantly reduces the target threat degree, with a maximum reduction of 56.92% for single waves—40.63%higher than that of traditional methods, demonstrating the applicability of the composite evaluation system in complex battlefield situations. In multi-wave attacks, the threat degree reduction multiple gradually increases, and the unit iterative efficiency increases by 3.9 times. The solution quality increases by 15.12% in dispersed situations, indicating good adaptability and resilience mechanism to environmental degradation. Across three waves, the total threat reduction rate reaches 87.47%, unit missile efficiency increases by 41.08%, and the decision-making time of a single wave is not more than 1.55 s, meeting real-time requirements. The effectiveness of the intelligent decision-making method for hypersonic missile collaborative operations is validated.
Polarization Imaging Detection for Military Applications and Key Technique Analysis
WANG Kainan;ZHANG Zhiwei;WANG Xiaowei;The unique advantages and key techniques of polarization imaging detection technology were summarized in response to the various challenges faced by target detection technology in modern military fields, such as identification, penetrability and anti-interference capability.First, the basic principles, advantages and disadvantages of six polarization imaging methods were comparatively analyzed, including time division, amplitude division, aperture division, focal plane division, emerging channel modulation, and metasurface polarization imaging. Subsequently, the applications and prospects of polarization imaging detection technologies in three military scenarios were summarized, namely military target detection, smoke and water penetration detection, and polarization imaging navigation. Four key techniques were analyzed, namely target polarization characteristics, polarization transmission characteristics, polarization imaging detection methods and equipment, and image processing algorithms. Finally, future development trends of polarization imaging detection technologies were discussed based on the application requirements,aiming to provide valuable insights and references for related researches in this field.
