磁悬浮框架飞轮磁轴承技术研究与发展现状

对磁悬浮框架飞轮(MSGFW)和高精度磁轴承研究现状及其未来发展进行了详细阐述。根据转子悬浮力类型，将磁悬浮框架飞轮分为磁阻力构型、洛伦兹力构型和混合力构型，并结合三种构型论述了国内外框架飞轮的发展过程。在此基础上，对球面磁阻力磁轴承和洛伦兹力磁轴承进行了详细介绍，并结合磁路图分析其工作原理，比较了同类磁轴承的优劣。展望了磁悬浮框架飞轮与高精度磁轴承的未来发展方向，指出高动态响应检控共位平动球面磁阻力磁轴承，标准磁悬浮动量球和磁悬浮控制敏感球是磁悬浮框架飞轮的研究重点。     

Specific grinding energy and surface roughness of nanoparticle jet minimum quantity lubrication in grinding

Nanoparticles with the anti-wear and friction reducing features were applied as cooling lubricant in the grinding fluid. Dry grinding, flood grinding, minimal quantity of lubrication（MQL）, and nanoparticle jet MQL were used in the grinding experiments. The specific grinding energy of dry grinding, flood grinding and MQL were 84, 29.8, 45.5 J/mm³, respectively. The specific grinding energy significantly decreased to 32.7 J/mm³ in nanoparticle MQL. Compared with dry grinding, the surface roughness values of flood grinding, MQL, and nanoparticle jet MQL were significantly reduced with the surface topography profile values reduced by 11%, 2.5%, and 10%,respectively, and the ten point height of microcosmic unflatness values reduced by 1.5%, 0.5%,and 1.3%, respectively. These results verified the satisfactory lubrication effects of nanoparticle MQL. MoS₂, carbon nanotube（CNT）, and ZrO₂ nanoparticles were also added in the grinding fluid of nanoparticle jet MQL to analyze their grinding surface lubrication effects. The specific grinding energy of MoS₂ nanoparticle was only 32.7 J/mm³, which was 8.22% and 10.39% lower than those of the other two nanoparticles. Moreover, the surface roughness of workpiece was also smaller with MoS₂ nanoparticle, which indicated its remarkable lubrication effects. Furthermore,the role of MoS₂ particles in the grinding surface lubrication at different nanoparticle volume concentrations was analyzed. MoS₂ volume concentrations of 1%, 2%, and 3% were used.Experimental results revealed that the specific grinding energy and the workpiece surface roughness initially increased and then decreased as MoS₂ nanoparticle volume concentration increased.Satisfactory grinding surface lubrication effects were obtained with 2% MoS₂ nanoparticle volume concentration.     

Numerical analysis and optimization of boundary layer suction on airfoils

Numerical approach of hybrid laminar flow control(HLFC) is investigated for the suction hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry’s transition model applied for simulating the flow with boundary layer suction is validated. The experiment data are compared with the computational results. The solutions show that this transition model can predict the transition position with suction control accurately. A well designed laminar airfoil is selected in the present research. For suction control with a single hole, the physical mechanism of suction control, including the impact of suction coefficient and the width and position of the suction hole on control results, is analyzed. The single hole simulation results indicate that it is favorable for transition delay and drag reduction to increase the suction coefficient and set the hole position closer to the trailing edge properly. The modified radial basis function(RBF) neural network and the modified differential evolution algorithm are used to optimize the design for suction control with three holes. The design variables are suction coefficient, hole width, hole position and hole spacing. The optimization target is to obtain the minimum drag coefficient. After optimization,the transition delay can be up to 17% and the aerodynamic drag coefficient can decrease by 12.1%.     

固体燃料空气涡轮火箭发动机工作模式

根据SP-ATR目前存在的燃气难以兼顾清洁和富燃的问题,文章提出将原本由1股燃气单独承担驱动涡轮和补燃功能的工作模式分解为由2股燃气分别担负驱涡和补燃功能的工作模式。通过对比分析该工作模式的SP-ATR和固冲发动机、涡喷发动机工作特点,提出了适合该形式SP-ATR的性能计算模型,得到其飞行包线,发现该SP-ATR工作包线宽广,可完全包含涡喷和固冲发动机的工作包线。在此基础上,计算得到了SP-ATR在不同空域和速度条件下的飞行性能及变化规律:(1)随飞行高度和速度的增加,其比冲、比推力增加,但性能随外弹道变化幅度较小,整个工作范围性能稳定;(2)在近地面和低空SP-ATR均可实现低空亚音速盘旋和5 km高度以上的超音速飞行,且在比冲高于6 700 N.s/kg,同时保持比推力大于1 100 N.s/kg;(3)高空SP-ATR工作高度速度范围宽,比冲性能与冲压发动机相当,比推力为冲压发动机的2倍,相同飞行速度条件下飞行高度增加比冲增加、比推力增加,具有在更高高度巡航潜力,高空性能优势明显。     

一种适用于高速OFDM的符号定时同步算法

OFDM系统以其优秀的频带利用率受到了广泛的应用。本文就OFDM系统在高速数据传输环境下出现的符号定时同步问题与经典同步算法中的问题的不同点做了分析,并对针对小子载波数情况出现的不同对已有的经典符号定时同步算法做出了相应的改进。最后使用Matlab对其进行了仿真,可以得出在小子载波数的情况下捕获性能良好,是一种可以用于高速OFDM系统的符号定时同步算法。     

基于无人机平台的机动式标校系统设计与应用

随着我国航天事业的不断发展,地面卫星测控网也日益完善,呈现出数量多、分布广、频段宽、工作体制多等特点。为提高航天测控装备标校的精度和效率,克服传统标校方式所具有的造价高、操作繁杂等缺点,研制了一套车载机动式、基于无人机(UAVs)平台的航天测控装备标校系统。该系统采用实时载波相位差分定位(RTK)技术,配备多类高度集成小型化目标载荷,可对地面统一测控、雷达和光电装备进行精度鉴定以及日常进行大动态范围标校和训练等工作。首先,介绍了系统的工作原理、系统组成及精度鉴定数据处理流程;其次,基于外场实验,给出了该系统的鉴定效果;最后,相较于目前测试性能单一的标校系统,该系统具有集成度高、机动性强、覆盖频段广、可完成性能实验多等优点,有更好的使用和推广价值。     

地球同步卫星BSR硅太阳电池阵输出功率衰减规律分析

长期受粒子辐照、紫外辐照等因素的影响,地球同步卫星的太阳电池阵输出功率会出现较为明显的衰减。这里选取某地球同步卫星使用的背表面反射(BSR)硅太阳电池阵为研究对象,采用光强因子和温度因子修正太阳电池阵的输出功率,使用局部加权回归散点平滑法(LOWESS)分析了其在设计寿命期间的输出功率衰减规律;同时基于LOWESS建立了预测模型,用于硅太阳电池阵超寿运行期间的功率预测。实测数据表明:本文构建的预测模型可以满足超寿地球同步卫星在轨管理使用需求。     

基于SURE准则的参数自适应InSAR相位非局部滤波

干涉相位滤波是干涉合成孔径雷达(InSAR)处理中的关键步骤,然而传统滤波方法难以兼顾噪声抑制和细节保持的效果,故提出了一种改进的非局部滤波器。滤波参数由Stein无偏风险估计(SURE)准则自适应地选择,在有效降低InSAR相位噪声的同时,保留干涉条纹细节和城市建筑的边缘。通过在仿真数据和TanDEM-X实测数据上分别进行实验,并与传统滤波方法对比分析,验证所提出方法的有效性。     

基于EFFD方法的自然层流短舱优化设计

采用extended free-form deformation(EFFD)方法研究了自然层流(natural laminar flow,NLF)短舱的气动外形优化设计方法.使用基于Bernstein基函数的EFFD方法完成了NLF短舱剖面的参数化,利用基于k-εSST(shear stress transport)两方程湍流模型的γ-θ转捩模型进行自然转捩预测,结合EFFD、一种混合动网格方法、Kriging代理模型和改进的粒子群算法(particle swarm optimization,PSO)建立了针对NLF短舱气动外形的优化设计框架.采用该框架分别对通气NLF短舱和带动力NLF短舱进行优化设计.单独通气NLF短舱优化结果的外表面实现48%的层流,阻力系数比初始通气NLF短舱减小了0.0003.带动力NLF短舱的优化结果外表面保持了41%的层流.这些结果表明采用相关技术建立的优化设计框架在NLF短舱设计中具有一定应用价值.     

INS/GNSS组合导航系统校准方法

惯性导航系统(INS)和全球导航卫星系统(GNSS)组合的导航系统应用越来越广泛,它的校准问题亟待解决。本文简要介绍了目前广泛使用的各种导航系统,论述了INS/GNSS组合导航系统的工作原理及组合算法;详细分析了INS/GNSS组合导航系统各种测试及校准方法,比较了各种校准方法的优缺点;提出了INS/GNSS组合导航系统校准装置应具备的条件:可产生标准的空间位置和速度、可产生标准的姿态角度变化、可有效地接收GNSS卫星信号、统一的时间基准与同步信号。