Numerical investigation on jet interaction with a compression ramp

A numerical investigation on jet interaction in supersonic laminar flow with a compres- sion ramp is performed utilizing the AUSMDV scheme and a parallel solver. Several parameters dominating the interference flowfield are studied after defining the relative increment of normal force and the jet amplification factor as the evaluation criterion of jet control performance. The computational results show that most features of the interaction flowfield between the transverse jet and the ramp are similar to those between a jet and a flat plate, except that the flow structures are more complicated and the low-pressure region behind the jet is less extensive. The relative force increment and the jet amplification factor both increase with the distance between the jet and the ramp shortening till quintuple jet diameters. Inconspicuous difference is observed between the jet-before-ramp and jet-on-ramp cases. The variation of the injection angle changes the extent of the separation region, the plateau pressure, and the peak pressure near the jet. In the present computational conditions, 120 is indicated relatively optimal among all the injection angles studied. For cold gas simulations, although little influence of the jet temperature on the pressure distribution near the jet is observed under the computation model and the flow parameters studied, reducing jet temperature somehow benefits the improvement of the normal force and the jet efficiency. When the pressure ratio of jet to freestream is fixed, the relative force increment varies little when increasing the freestream Mach number, while the jet amplification factor increases.     

Use of land＇s cooperative object to estimate UAV＇s pose for autonomous landing

The research of unmanned aerial vehicles＇（UAVs＇）autonomy navigation and landing guidance with computer vision has important signifcance.However,because of the image blurring,the position of the cooperative points cannot be obtained accurately,and the pose estimation algorithms based on the feature points have low precision.In this research,the pose estimation algorithm of UAV is proposed based on feature lines of the cooperative object for autonomous landing.This method uses the actual shape of the cooperative-target on ground and the principle of vanishing line.Roll angle is calculated from the vanishing line.Yaw angle is calculated from the location of the target in the image.Finally,the remaining extrinsic parameters are calculated by the coordinates transformation.Experimental results show that the pose estimation algorithm based on line feature has a higher precision and is more reliable than the pose estimation algorithm based on points feature.Moreover,the error of the algorithm we proposed is small enough when the UAV is near to the landing strip,and it can meet the basic requirements of UAV＇s autonomous landing.     

民用飞机有限元模型质量检查探讨

介绍了民用飞机有限元模型质量检查内容,提出了网格质量检查项目及方法,给出了有限元单元几何检查建议值,介绍了刚度检查、静平衡检查、自由振动检查、热膨胀检查、"接地"检查等模型质量检查方法。     

基于LabWindows/CVI的ARINC429总线数据采集系统设计

首先设计了一套基于LabWindows/CVI的ARINC429总线数据采集系统,该系统采用服务器端和客户端结合的方式,利用线程池的次线程采集数据,并利用异步时钟把数据打包发送给客户端。其次,讨论了两种采集方式对数采系统的影响,并且对ARINC429总线某个Label号的数据失效进行了处理,为以后的ARINC429的数采操作提供了借鉴。     

铸铝薄壁件数控加工变形控制

为了解决铸铝薄壁件在加工过程中切削力及初始进刀带来的影响,针对此类零件的加工工艺进行研究,从零件材料性能,工艺方法、进退刀方式、切削参数等方面进行深入分析与应用,采取减小切削量增大进给值的方法及圆插补和斜坡进刀方式控制切削变形,利用压顶交叉的方式控制装夹变形,提高了零件加工的可靠性,保证了零件精确尺寸。     

分布式测控系统在发动机试验中的应用

介绍一种基于网络的分布式测控系统设计方案,并以NI-cRIO产品为载体,详细描述了系统的体系结构、硬件和软件架构,具体给出了系统的设计目标和硬件选型。系统在发动机试验中的成功应用,验证了该方案的可行性。     

空间站柔性太阳电池翼对日跟踪控制

空间站柔性太阳电池翼高稳定对日跟踪驱动控制,对于保障空间站长期在轨能源安全和平稳运行具有重要意义。在推导柔性太阳电池翼动力学模型、柔性体模态分析和截断、Alpha对日定向装置机电系统模型、非线性传动系统模型的基础上,对空间站柔性太阳电池翼对日跟踪控制系统进行设计。采用Heaviside五次样条变速规划、位置和速度两级闭环、速度环陷阱滤波器柔性振动抑制的组合方案,实现空间站柔性太阳电池翼高稳定驱动控制。通过对典型工况的仿真校核,验证所设计的控制方案可实现跟踪精度优于0.3°、速度偏差±0.005(°)/s、稳定度优于7%@0.065(°)/s的性能指标。同时,Alpha对日定向装置的启动和变速过程中驱动力矩不大于30 N·m,稳速运行期间驱动力矩不大于5 N·m。各项性能指标要好于国际空间站Alpha对日定向装置,满足使用要求。     

航天器姿态容错控制技术研究现状与发展

更远、更复杂的人类空间探测任务要求航天器具有更高的可靠性,因此航天器的容错控制技术受到了广泛关注。对航天器姿态系统的容错控制技术发展现状进行了分析,总结了国内外近年来航天器姿态容错控制的成果,重点分析了利用自适应控制、滑模控制、模糊控制、神经网络控制等理论开展容错控制的进展,并分别阐述了采用不同技术途径发展容错控制的优缺点。最后,展望了航天器姿态容错控制技术未来的发展。     

基于旋转双光楔的像方扫描大视场成像光学系统设计

针对无人机传统外挂式光电载荷吊舱窗口尺寸大、无法实现大视场扫描需求的现状，提出了一种基于旋转双光楔的像方扫描红外大视场成像光学系统设计。该系统在传统像方扫描光学镜组基础上引入了双光楔扫描器，以增大系统的扫描视场角，解决了高速无人机目前面临的红外窗口有限且成像视场角小的问题。采用光学设计软件进行了仿真，设计后的光学系统物方视场范围为±21.665°，满足了大视场范围的工作要求。设计结果表明，在工作波段（3.7μm ~4.8μm）范围内，该系统的成像质量高，中心视场调制传递函数在33(lp/mm)空间频率下可达0.45，全视场范围内的调制传递函数>0.42@33(lp/mm)，像点能量集中度较好，接近衍射极限。与传统扫描光学系统相比，采用基于旋转双光楔的新型像方扫描成像光学系统设计，在保证各项设计指标不变的前提下，能够将光学系统的径向尺寸减少20%以上，可满足未来无人机实现轻量化和小型化的应用需求，拥有良好的应用前景。