柔性多层冲击空间碎片防护结构设计与试验

充气展开密封结构是未来空间站以及大型空间居住舱的理想构建形式,其外蒙皮由气密层、增强层、微流星体和空间碎片防护层、辐射保护层以及热控层组成。为了既满足对空间碎片的防护,又满足折叠、收纳以及展开的要求,空间碎片防护层需要采用多层冲击防护结构设计。基于多层冲击防护结构,采用国产的玄武岩纤维材料和芳纶织物的特性参数,根据弹道极限方程设定了柔性空间碎片防护层的设计参数,并通过高速撞击试验对根据设计参数生产的试验件进行了试验验证,试验结果与柔性多层冲击防护结构的弹道极限方程吻合较好。     

基于压电纤维复合材料的航天器动力学建模与振动抑制

压电纤维复合材料(MFC)在柔性航天器的振动主动抑制中具有很好的应用前景。利用哈密顿原理和压电驱动的载荷比拟方法,建立了带MFC压电驱动的离散形式的刚柔耦合动力学方程,采用线性二次型最优控制(LQR)算法进行主动控制。结果表明：在航天器的柔性体受到脉冲载荷激励条件下,使用MFC驱动器可以实现航天器挠性振动的快速抑制,并且同时保持中心刚体姿态的稳定性,即能够实现挠性振动与姿态运动的协同控制。基于MFC的主动控制方法对于高频响应也具有较好的控制效果。对于柔性占优的航天器,采用MFC的主动控制优于被动控制。本文方法在处理具有复杂柔性体的航天器时更具优势,更适合于工程应用。     

Simulation and analysis of chemical release in the ionosphere

Ionospheric inhomogeneous plasma produced by single point chemical release has simple space-time structure, and cannot impact radio wave frequencies higher than Very High Frequency (VHF) band. In order to produce more complicated ionospheric plasma perturbation structure and trigger instabilities phenomena, multiple-point chemical release scheme is presented in this paper. The effects of chemical release on low latitude ionospheric plasma are estimated by linear instability growth rate theory that high growth rate represents high irregularities, ionospheric scintillation occurrence probability and high scintillation intension in scintillation duration. The amplitude scintillations and the phase scintillations of 150?MHz, 400?MHz, and 1000?MHz are calculated based on the theory of multiple phase screen (MPS), when they propagate through the disturbed area.     

基于变刚度变阻尼的柔性喷管动态模型

针对柔性接头动态迟滞曲线受控制系统控制位置精度和动态响应速度影响较大的问题,基于电液伺服机构和柔性接头变刚度变阻尼模型,构建了柔性喷管的电液伺服机构-变刚度变阻尼模型,将其和电液伺服机构-定刚度定阻尼模型进行了对比。分析了电液伺服机构主要参数、柔性接头工作参数等对电液伺服机构-柔性接头系统动态特性的影响。分析结果表明:电液伺服机构-变刚度变阻尼模型所构造的迟滞曲线可更准确地与实验结果相吻合,并符合迟滞曲线随频率变化的规律,反馈系数、放大器静态放大系数、电液伺服机构增益、滑阀流量增益等参数对系统动态特性的影响更为明显。该模型为固体火箭发动机电液伺服机构-柔性接头系统动态特性的调整提供理论依据。     

Assessment on critical technologies for conceptual design of blended-wing-body civil aircraft

Civil aviation faces great challenges because of its robust projected future growth and potential adverse environmental effects. The classical Tube-And-Wing(TAW) configuration following the Cayley's design principles has been optimized to the architecture's limit, which can hardly satisfy the further requirements on green aviation. By past decades' investigations the BlendedWing-Body(BWB) concept has emerged as a potential solution, which can simultaneously fulfill metrics of noise, emission and fuel burn. The purpose of the present work is to analyze the developments of critical technologies for BWB conceptual design from a historical perspective of technology progress. It was found that the high aerodynamic efficiency of BWB aircraft can be well scaled by the mean aerodynamic chord and wetted aspect ratio, and should be realized with the trade-offs among stability and control and low-speed performance. The structure concepts of non-cylinder pressurized cabin are of high risks on weight prediction and weight penalty. A static stability criterion is recommended and further clear and adequate criteria are required by the evaluations of flying and handling qualities. The difficulties of propulsion and airframe integration are analyzed. The energy to revenue work ratios of well-developed BWB configurations are compared,which are 31.5% and 40% better than that of TAW, using state-of-art engine technology and future engine technology, respectively. Finally, further study aspects are advocated.     

A drilling tool design and in situ identification of planetary regolith mechanical parameters

The physical and mechanical properties as well as the heat flux of regolith are critical evidence in the study of planetary origin and evolution. Moreover, the mechanical properties of planetary regolith have great value for guiding future human planetary activities. For planetary subsurface exploration, an inchworm boring robot (IBR) has been proposed to penetrate the regolith, and the mechanical properties of the regolith are expected to be simultaneously investigated during the penetration process using the drilling tool on the IBR. This paper provides a preliminary study of an in situ method for measuring planetary regolith mechanical parameters using a drilling tool on a test bed. A conical-screw drilling tool was designed, and its drilling load characteristics were experimentally analyzed. Based on the drilling tool-regolith interaction model, two identification methods for determining the planetary regolith bearing and shearing parameters are proposed. The bearing and shearing parameters of lunar regolith simulant were successfully determined according to the pressure-sinkage tests and shear tests conducted on the test bed. The effects of the operating parameters on the identification results were also analyzed. The results indicate a feasible scheme for future planetary subsurface exploration.     

三轴承矢量喷管红外辐射特性

针对涡扇发动机用三轴承矢量喷管（3BSN）,通过数值模拟的方法研究了在巡航和垂直起降（VTOL）状态即非矢量和90°矢量状态下三轴承矢量喷管的红外辐射空间分布特征,并分析了其影响机理。结果表明,在非矢量状态下由于特殊的几何型面使得喷管下壁面出现了局部高温区,喷流形状也变成椭圆锥形,造成垂直探测面上正探测角壁面红外辐射较负探测角最大增加44.6%,水平探测面上的燃气红外辐射大于垂直探测面;90°矢量状态下,由于偏转的喷管结构对前端高温部件的遮挡,总辐射峰值仅为非矢量状态的43.3%;喷管90°矢量偏转使得远离曲率中心一侧的气流速度降低温度升高,喷管外侧出现了大范围的局部高温区,导致垂直探测面负探测角范围的壁面辐射大于正探测角范围,最大相对差值达到71.9%。喷管偏转也遮挡了部分喷管内部的高温燃气,垂直探测面负探测角的仅能覆盖喷管出口处的高温燃气区域,明显小于正探测角,造成燃气辐射出现了20%的最大相对差值。     

发动机故障诊断的变记忆约束滤波算法

为提高故障诊断可靠性,给出了3种利用多次测量信息减少测量误差影响的方法,即变记忆约束滤波算法、分段算术平均预平滑算法以及指数顶平滑算法。其中,变记忆约束滤波算法能够有效地避免由于故障方程多重共线性所引起的病态解。证明了多故障诊断问题中滤波算法与分段算术平均算法的等价性,证明了在衰减滤波的条件下（第一变记忆因子小于1）,随测量点数的增加,变记忆滤波算法的第一变记忆因子与指数平滑的平滑系数之和趋近于1。利用计算机仿真方法对于所得结论进行了检验。     

激光辅助车削工艺参数对单晶硅表面质量的影响

为了提高单晶硅激光辅助车削加工表面质量,通过开展激光辅助和常规车削加工试验,结合表面粗糙度、表面形貌及拉曼光谱检测,研究激光辅助车削技术对加工质量的影响。基于正交试验方法,研究单晶硅激光辅助车削工艺参数对表面粗糙度的影响;通过方差分析和极差分析评估各因素对表面粗糙度的影响。研究结果表明：与常规车削相比,激光辅助车削可有效提高加工表面质量,降低材料表面的残余应力。主轴转速、进给速度、切削深度和脉冲占空比对表面粗糙度的贡献率分别为17.51%、44.48%、6.69%和14.70%。确定最佳加工参数组合如下：主轴速度为4 000 r/min,进给速度为2 mm/min,切削深度为5μm,脉冲占空比为30%,最终获得表面粗糙度Rq为2.4 nm的高质量表面。