低成本捷联惯导不对称动态误差的神经网络补偿

 针对低成本捷联惯导系统(SINS)中陀螺动态误差的不对称性在角振动条件下造成姿态漂移的问题,设计了多层前向神经网络的补偿模型。在标定模型参数时,为降低对外部参考信号测量精度的要求,提出用姿态解算的最终误差作为网络优化目标的训练方法。由于最终的姿态误差不是网络的期望输出,无法采用有导师的训练方法,为此采用了微粒群优化算法。仿真实验结果表明:补偿后的陀螺动态误差的不对称度减小了一个数量级。     

一种高效的基于可靠性的多学科设计优化方法(英文)

Design for modem engineering system is becoming multidisciplinary and incorporates practical uncertainties; therefore, it is necessary to synthesize reliability analysis and the multidisciplinary design optimization （MDO） techniques for the design of complex engineering system. An advanced first order second moment method-based concurrent subspace optimization approach is proposed based on the comparison and analysis of the existing multidisciplinary optimization techniques and the reliability analysis methods. It is seen through a canard configuration optimization for a three-surface transport that the proposed method is computationally efficient and practical with the least modification to the current deterministic optimization process.     

跳跃式跨大气层飞行弹道仿真分析

针对跳跃式跨大气层飞行弹道的特殊性,建立了其飞行动力学模型,在此基础上,对其弹道进行了仿真分析,得知乘波构型是跳跃式跨大气层飞行器理想气动布局,研究对比了跳跃弹道和惯性弹道的不同性能,结果表明跳跃飞行具有惯性飞行所无法比拟的突防能力。所得结论对跳跃式跨大气层飞行和未来新型武器装备的发展方向的研究具有一定的参考价值。     

一种基于模拟退火的支持向量机超参数优化算法

基于统计学习理论的支持向量机技术以探求小样本情况下如何获得更好的机器学习规律而见长,与基于经验风险最小化原则的机器学习方法相比能够获得更佳的泛化能力,相关超参数的选择对其分类或回归性能有较大影响.针对径向基核支持向量机超参数优化问题,提出了一种改进的基于模拟退火算法的高效多目标优化算法,并详细讨论了优化寻优过程中搜索空间、初始可行解、初温和最优目标函数的设计方法.通过在多个标准数据集上的测试验证,证实了本文所提算法的可行性和有效性.     

温度对磁屏蔽霍尔推力器磁场构型的影响研究

霍尔推力器磁路设计主要通过常温静态磁场仿真得到，并实测推力器非工作状态常温磁场进行复核。大功率霍尔推力器将面临更为严峻的热问题，推力器工作时磁路系统受高温影响，因此在常温下仿真得到的磁场位形会因温度升高而产生偏移，不能反映推力器真实工作时的磁场情况。为研究霍尔推力器工作时热量对磁路系统的影响，通过热磁耦合仿真对10kW磁屏蔽霍尔推力器的热态磁场分布进行研究，并对热态、常温仿真结果进行了对比，发现在阳极附近的径向磁感应强度Br的差异比放电室出口更大。常温设计的磁屏蔽构型在热态时偏离磁屏蔽，磁场和壁面最大不符合度达到13%，通过陶瓷出口型面修正后重新获得磁屏蔽效果，使最大不符合度降低到4.8%以下。合理热设计有助于降低热载荷，热仿真得到磁路系统最高温度低于500℃，低于0.78倍的居里温度Tc磁性急剧转变点，不会出现磁性能急剧下降，但热量对磁屏蔽霍尔推力器磁场构型的影响是应该考虑的。     

采用MSCMG群的卫星平台敏捷机动控制地面闭环试验验证

针对新型惯性执行机构磁悬浮控制力矩陀螺(Magnetically suspended control moment gyro, MSCMG),基于金字塔构型开展卫星平台敏捷机动控制地面闭环试验研究,以验证MSCMG的姿态控制性能。首先基于MSCMG搭建卫星平台控制地面试验系统,建立数学模型;接着针对气浮台外界扰动抑制及大角度敏捷机动控制问题,基于变参数滑模控制设计姿态控制算法,采用鲁棒伪逆方法进行MSCMG群框架角速度分配;并针对MSCMG的特性对框架角速度和角加速度进行了限幅,开展闭环控制试验研究。试验结果表明,采用MSCMG进行气浮台姿态稳定控制实验,可以实现姿态稳定度优于5×10~(-4)(°)/s,且在实现30°/15 s的机动指标时,MSCMG框架角速度具有良好的跟踪性能,且磁悬浮转子在输出大力矩时仍然保持稳定悬浮,具有较强的鲁棒性。通过地面闭环试验验证了MSCMG作为姿控执行机构的优异性能,为其未来进一步应用研究奠定基础。     

小卫星结构的发展与展望

从结构构型、结构材料、结构连接方式和结构评价指标四个方面论述了小卫星结构的发展现状,分析了小卫星球形或准球形壳体结构、箱板式卫星平台结构、框架式立方星结构、基于特殊需求的专用化结构及多功能一体化结构的特点及其适用范围,指出了未来小卫星结构通用化、小型化、专用化、多功能一体化的多元发展趋势,提出了小卫星结构材料、连接方式和评价指标方面的发展建议,旨在为小卫星结构的创新发展提供参考。     

A wall-thickness compensation strategy for wax pattern of hollow turbine blade

As an important index affecting the aerodynamic performance and the structural strength of hollow turbine blades, the wall-thickness precision of the blade is mainly inherited from the positional relationship between the corresponding wax pattern and the internal ceramic core. However, due to locating errors, the actual position of ceramic core is always deviated from the ideal position, which makes it difficult to guarantee the wall-thickness precision of the wax pattern. To solve this problem, a wall-thickness compensation strategy is proposed in this paper. Firstly, based on the industrial computed tomography (ICT) technique and curve matching algorithms, a model reconstruction method is developed, with which the 3D model of a trial wax pattern can be easily constructed. After that, focusing on eliminating the wall-thickness errors of the trial wax pattern, an optimization method for the pose of the ceramic core in the wax pattern is proposed. Then, by mapping the optimal pose of the ceramic core to length adjustments of the locating rods, the wall-thickness errors of the wax pattern can be greatly reduced. A case study is also given to illustrate the effectiveness of the proposed compensation strategy.     

Effects of stability margin and thrust specific fuel consumption constrains on multi-disciplinary optimization for blended-wing-body design

Blended-Wing-Body(BWB) configuration, as an innovative transport concept, has become a worldwide research focus in the field of civil transports development. Relative to the conventional Tube-And-Wing(TAW) configuration, the BWB shows integrated benefits and serves as a most promising candidate for future ‘‘green aviation". The objective of the present work is to figure out the effects of the stability margin and Thrust Specific Fuel Consumption(TSFC) on the BWB design in the framework of Multi-Disciplinary Optimization(MDO). A physically-based platform was promoted to study the effect static stability margin and engine technology level. Low-order physically based models are applied to the evaluation of the weight and the aerodynamic performance. The modules and methods are illustrated in detail, and the validation of the methods shows feasibility and confidence for the conceptual design of BWB aircrafts. In order to find out the relation between planform changes and the selection of stability and engine technology level, two sets of optimizations are conducted separately. The study proves that these two factors have dominant effects towards the optimized BWB designs in both aerodynamic shapes, weight distribution, which needs to be considered during the MDO design process. A balance diagram analysis is applied to find out a reasonable static stability margin range. It can be concluded that a recommended stability margin of a practical BWB commercial aircraft can be half of that of a conventional TAW design.     

Hypersonic vehicle aerodynamic design using modified sequential approximate optimization

Hypersonic vehicles are receiving increased attention within the aerospace community due to their high cruise speed and long-range capabilities. In this paper, a modified Sequential Approximate Optimization method is proposed for an optimized aerodynamic design of a hypersonic vehicle. As part of this approach, a constrained experimental design method is developed to handle the constraints more efficiently. A radial basis function is used to surrogate time-consuming CFD analysis. An efficient and more robust numerical mesh morphing scheme for the hypersonic vehicle is developed for the generation of high-quality meshes. Within this paper, a novel adaptive infilling strategy is proposed which uses an inaccurate search technique coupled with an elite archive. This allows the location of a more promising sample region and hence improves the surrogate accuracy, thereby further enhancing the optimization efficiency. A hypersonic vehicle aerodynamic design problem is solved using the proposed approach and satisfactory results are obtained at much lower computational costs. The lift-to-drag ratio is increased by 23.8% when compared with the base configuration while also satisfying the volume and lift constraints. The pressure and Mach contours have been compared with those of the base configuration and the results demonstrate the strength of the optimized configuration. The modified sequential approximate optimization for designing an improved hypersonic vehicle is worth referencing in future work.