In order to study the low energy impact resistance of re-entrant star-shaped(RES)and re-entrant circular star-shaped(RECS)honeycomb sandwich panels with negative Poisson ratio,a finite element model of honeycomb sandwich panels with composite laminates and ABS honeycomb is established by using commercial software ANSYS/LS-DYNA.Impact response of the composite sandwich panels with RES honeycomb and RECS honeycomb is analyzed numerically at low impact energies of 10 J,15 J,30 J.In this paper,the impactor displacement versus time curves、contact force versus time curves and energy absorption ratio of sandwich panels under different impact conditions are analyzed and compared.The simulation results show that under the same impact conditions,the damage depth of RECS honeycomb sandwich panels is greater than that of RES hon-eycomb sandwich panels,and the difference is more obvious when under in-plane impact.In addition,the impactor has a lower rebound speed after impacting RECS honeycomb sandwich panels,that is,the RECS honeycomb sandwich panel has a higher energy absorption ratio.According to the above results,it is concluded that RES honeycomb sandwich panel has better low en-ergy impact resistance than RECS honeycomb sandwich panel,but the latter has better energy absorption performance.
When air-breathing aircraft is flying over a wide area,the upflow of the combustor central axis will change greatly,and the flow field parameters will fluctuate along the axis. Therefore,it is necessary to carry out a study on the influence of axis flow field parameter fluctuation on combustion chamber performance,so as to provide relevant theoretical support for the com-bustion chamber of air-breathing aircraft in wide-area flight design. Based on the N-S gas-phase control model,combined with combustion model,turbulence model,burning rate model and mass transfer model,a numerical simulation model of flow com-bustion in solid fuel scramjet combustor is established. Through this model,the influence of the upflow field parameter fluctua-tion of the central axis on the combustor performance is carried out. The results show that for a optimized combustor configura-tion,different inlet air flow rates will cause the Mach number of the combustor to oscillate along the flow direction. The greater the oscillation amplitude,the greater the total pressure loss. Too high or too low inlet air flow rate will both result in Mach num-ber oscillation in the combustor. However,selecting a suitable inlet air flow rate can significantly reduce the Mach number os-cillation of combustor flow. Therefore,for different combustor configurations,appropriate inlet air flow should be designed to reduce the Mach number oscillation of the flow field in the combustor,reducing the flow loss and improving the working per-formance of the combustor.
As a measuring element in wind tunnel test, it is important to ensure the measurement accuracy of strain balance.However, in the continuous wind tunnel, due to the long running time of the wind tunnel and the continuous transformation of Mach number, the temperature distribution of the balance body will be uneven, resulting in temperature gradient.This temperature gradient has an obvious influence on the measurement accuracy of the axial force of the balance.In order to explore the influence of temperature gradient on the axial force and strain output of the balance in the continuous wind tunnel, three temperature loading conditions were summarized according to the actual working conditions, and the thermal-solid coupling analysis of the 80A balance was carried out by ANSYS Workbench.The results show that the higher the temperature of the base point of the temperature gradient is, the faster the temperature input is, the more uneven the temperature distribution of the balance is, and the larger the temperature gradient is, the larger the axial force and strain output is. Considering the heat conduction of the back support rod, the temperature distribution of the balance body is relatively uniform, the temperature gradient is small, and the output of axial force and strain is small.
Projectile conical motion causes significant control disturbances in the guidance system. In order to compensate for this error,a new conical error compensation algorithm has been analyzed to improve the accuracy and real-time performance of the bullet attitude control system in a high-dynamic motion environment. Combining the quaternion four-level Runge-Kutta method and the triad equivalent rotation vector method,an improved triad quaternion attitude algorithm based on modified Ro-driguez parameters for angle increment output is utilized. Derive the corresponding differential equation expressions to establish the mathematical model for solving the attitude using the improved triad quaternion algorithm. Simulation results demonstrate that compared to traditional conical error compensation algorithms,improved algorithms can more effectively compensate for conical errors,with an average accuracy improvement of approximately 17. 32％,reduce computational load in high-dynamic environment and improve real-time performance by approximately 22. 54％.
针对实测爆炸冲击波信号中存在大量噪声信号以及自适应白噪声完整集合经验模态分解(CEEMDAN)方法在降噪过程中容易出现信号失真的问题,提出了一种基于CEEMDAN方法和高斯混合模型(GMM)的爆炸冲击波降噪算法.该算法首先将原始爆炸冲击波数据通过CEEMDAN方法分解得到若干个本征模态分量IMF,并利用GMM聚类算法将IMF分量分为多个类别.通过计算不同IMF分量的方差贡献率校核聚类结果,剔除高频噪声类别的IMF分量.对受噪声干扰的IMF分量,采用小波阈值方法进行滤波去除噪声.最后,将滤波后的IMF分量与未受噪声干扰的IMF分量一起重构,并获得降噪后的爆炸冲击波信号.实验结果表明:CEEMDAN-GMM与小波阈值算法信噪比值RSNR和均方根误差值MRMSE分别比CEEMDAN方法和CEEMDAN-小波阈值算法提高了 10.19 dB和 2.99 dB,降低了 0.42×10-4和0.14×10-4.
针对巡飞弹药巡飞航迹规划算法设计以及作战任务想定,结合一种基于二维和三维数字地形的空间模型,提出基于自然界蚂蚁觅食的最短路径理论的航迹规划算法,实现巡飞弹药执行对既定作战区域定点威胁目标避障巡飞的航迹规划方案,对巡飞弹药已建立的环境中进行飞行模拟仿真和结果分析,验证了蚁群算法的正确性和有效性.
针对铰链力矩风洞试验中的动态载荷问题,研制了动态载荷监视预警系统,用于试验中动态载荷的实时监视预警.给出了动态载荷监视预警系统的软硬件组成和设计方案,动态载荷数据处理方法,以及系统预警的临界限值设定方法,并进行了系统的应用验证.研究结果表明:动态载荷监视预警系统能够有效预警铰链力矩试验中存在的动态载荷,通过调整操纵面/天平系统的固有频率,避开流动分离产生的气动激励频率,能够避免相同操纵面偏度下大幅值动态载荷的产生,从而保证试验安全和试验数据可靠.
图像匹配在无人机视觉导航中起着至关重要的作用,在该领域已经出现了较多优秀的图像匹配算法,但对于不同季节下异源图像匹配尚鲜有报道.为进一步扩展该领域的研究工作,针对不同季节下异源图像匹配困难的问题,提出了一种基于模糊信息粒的图像匹配算法.首先,根据卫星图像和无人机航拍图像的地面分辨率确定无人机航拍图像的尺度缩放系数,进而对无人机航拍图像进行尺度预处理;其次,基于模糊信息粒建立图像匹配方法,对提取到的图像边缘进行相似性匹配,得到无人机航拍图像与卫星图像的匹配位置;最后,在冬季与夏季的无人机航拍图像和卫星图像数据集上进行验证.实验结果表明,该算法具有较强的鲁棒性,提高了图像匹配精度,为无人机视觉定位提供了一种新的思路.
为发挥助推-滑翔式导弹最大作战效能,需在一定的飞行条件约束下,对其总体参数进行优化设计.首先分析直接起滑式滑翔弹道下各类参数对飞行弹道的影响,并将整个优化过程划分为独立的两个阶段;而后采用自适应遗传算法对各阶段进行优化,得到了满足文中约束条件下的最佳导弹总体方案;最后采用蒙特卡洛模拟对该方法进行验证.结果表明,文中设计方法能够在5.5s内完成总体参数优化,并在±0.7%的精度范围内使得导弹进行直接起滑式飞行.
针对非同轴喉栓发动机喷管绝热层长度增加后,喉栓内部温度不降反升的现象,建立不同绝热层长度的系列三维喷管模型进行数值仿真计算,得到喉栓的温度分布和周围燃气的压强、速度、温度分布.通过对绝热层与喉栓之间狭缝内的流场进行分析,发现狭缝中存在燃气环绕喉栓流动的现象,这种环绕流动受狭缝上下方入口的压强差影响,又分为单侧绕流和双侧绕流两种.过长的绝热层会使狭缝上下方入口压差上升,燃气绕流形式由双侧绕流变为单侧绕流,流动传热效果增强,喉栓结构温度升高.通过比较两种燃气绕流形式下的喉栓温度,得到了喉栓绝热层长度与结构温度分布的响应关系,提高了对喉栓结构温度分布的预测精度.
针对采用固相装药的纯燃气式弹射装置研究高压室内弹道设计过程中装药增面比参数对导弹出筒运动特性的影响,分析了5 种不同装药结构的增面比表达式,通过方程组和软件数值仿真求解了高压室、低压室压强及导弹出筒速度、加速度,根据计算结果进行对比并得出结论:增面燃烧装药可以显著降低导弹出筒的峰值加速度;半球形装药可在三维方向上实现更大的增面比;在装药质量相同、出筒行程(筒长)相同的情况下,与管状增面燃烧装药结构相比,半球形装药结构可使导弹出筒运动性能得到明显提升.
针对制导航空炸弹在高空稀薄大气环境下气动模型不准的问题,首先通过设计激励输入和飞行数据采集方案,获取可辨识性的飞行源数据,随后基于动力学方程将飞行源数据转换为气动系数的方程输出,最后通过最小化方程输出误差平方和,提出了一种基于线性回归的气动参数辨识方法.该方法具备结构简单,工程可行性强等特点.通过制导航空炸弹六自由度非线性模型的飞行仿真数据对该方法进行了验证,结果表明,该方法能够较为准确地辨识出相应的气动数据.
针对遥感图像(RSI)中的目标相对较小、形变多样,且包含分布不均匀的非目标和背景等问题,提出一种基于空洞空间金字塔池化U-Net的遥感图像多目标检测方法.该方法利用空洞多尺度卷积提取多尺度目标的分类特征,运用空洞空间池化金字塔模块扩大卷积特征图的感受野,提取更充分的目标特征,并采用注意力机制、残差连接和长跳跃连接充分保留卷积层提取的 RSI的敏感特征.在公开遥感图像数据库EORSSD上的实验结果表明,所提出的方法能够从复杂多样的RSI中检测多尺度目标,检测精度为96.56%.
为提高空天地一体化网络的吞吐量,提出基于强化学习的链路优化算法(reinforcement learning-based link opti-mization,RLLO).RLLO算法以近地轨道卫星为基站提供回程链路.同时,RLLO算法通过管理无人机和微基站的资源以及优化无人机(unmanned aerial vehicles,UAV)的轨迹,提升吞吐量.先建立优化回程链路和接入链路的目标问题,再利用多臂老虎机的强化学习工具求解目标问题.仿真结果表明,相比于同类的基准算法,RLLO算法提高了吞吐量和用户端的可达速率.
通过直径9.5 mm钨锆合金球形破片在760～1 300 m/s速度下侵彻10 cm厚C35 钢筋混凝土靶的试验,获取了不同冲击速度下钢筋混凝土的成坑及损伤特性.基于数值模拟的方法扩展研究了直径为 8～13 mm系列球形破片在着角0°～75°时对钢筋混凝土的侵彻效应.试验和仿真结果表明:随着冲击速度的增加,钨锆破片剩余质量逐渐减少,对钢筋混凝土的侵彻深度逐渐增加,混凝土靶损伤形态由崩落成坑向径向裂纹扩展趋势变化,且靶板背面出现崩落现象;随着钨锆破片质量的增加,混凝土靶崩落成坑和径向裂纹扩展及靶板背面崩落现象逐渐明显;随着破片着角的增大,侵彻深度逐渐减小,有发生跳飞的趋势.研究结果可为战斗部毁伤元结构威力设计提供参考依据.
第二代舰载直流电力系统的不断推广应用,为高能武器发射、大功耗高频次武器发射提供了有效保障.对舰载直流电力系统进行电压监测以确保其正常运行显得尤为重要.针对复杂电磁环境作用下引起的电阻老化导致基于分压法的电压传感器的精确度等级随时间而降低的问题,文中提出了一种基于电阻分压与电子开关的中压直流自校准电压传感器方案.该方案针对分压器结构进行改进,在分压器中间位置电阻处并联一受控电子开关,通过微处理器控制电子开关状态,按电阻分压与分时采样原理,求解出分压器高压臂电阻阻值,从而更新分压器分压比以达到自校准的目的,同时针对传统分压式电压传感器难以兼顾测量范围与等级的缺点,提出了多档调理方案.按上述方案进行样机开发,并针对其性能指标设计了基本准确度试验与自校准试验.试验结果表明:基于该方案设计的电压传感器样机量程满足0～20 kV,测量精确度等级满足0.2 级,自校准试验验证了自校准方案的有效性.
针对可见光和红外复合制导导引头在不同的工作模式下,因探测器分辨率、视场角及光学设计指标的不同导致两种模式输出的跟踪偏差信息存在较大差别的问题,提出了一种变参数复合导引头PID控制方案.首先,通过分析导引头的伺服控制系统工作原理;然后,建立位置环、速度环、电流环控制回路模型;最后,对常规控制方法和复合导引头变参数PID控制方案进行仿真分析比较.结果表明,采用变参数复合导引头PID控制方案能提有效升复合导引头动态性能,上升时间缩短了50 ms,超调量下降了5%;稳态时间缩短了90 ms.
针对视觉目标跟踪在平衡算法跟踪性能和实时性方面存在的难点,提出了一种基于轻量化设计的孪生网络目标跟踪算法SiamLD.对主干网络进行轻量化设计,降低参数量和运算量,提高算法实时性.通过高低层特征融合模块,增强对低层语义信息的利用,并利用多分支交叉相关和完全交并比方法,提升了跟踪算法的跟踪性能.在UAV123和DTB70 跟踪基准上的实验结果表明,SiamLD算法跟踪性能优于其他主流算法,且在无人机平台中运行速度达到41FPS,有效地平衡了算法跟踪性能和实时性.
通过数值模拟和试验验证的方法对非金属壳体战斗部陶瓷破片上靶率开展研究,主要分析了尼龙材料、ABS、聚乙烯战斗部壳体和陶瓷破片直径为2～6mm对破片上靶率的影响规律.结果表明:战斗部壳体材料为尼龙时,战斗部陶瓷破片在1～3m处靶板的上靶率最高;陶瓷球直径在一定范围内时,上靶率随陶瓷球直径的增大而增大,随布靶距离的增大而减小,陶瓷球直径为5mm时上靶率最高.研究成果可根据技术指标要求,通过匹配陶瓷球尺寸,实现战斗部可控范围内的有效毁伤.
为实现跨介质环境下智能弹药与发射平台的电气互联,并满足电气接口可靠连接及分离、电气防短路、密封、耐海洋环境等条件,对跨介质智能弹药无线电能传输技术应用进行分析,设计了一种单发射组件跨多介质能与上下两个方向上的两台接收组件同时传输接收能量的装置,对该装置的控制电源与脉冲电源耦合机构进行仿真建模,对收、发线圈磁场分布、功效特性等进行仿真计算.结果表明,该装置设计能够满足无线能量传输的功率与效率要求,可对无线电能传输技术在跨介质智能弹药上的工程化应用提供理论依据.
