精密小直径盲孔珩磨

在论述了珩磨、盲孔珩磨现状的基础上,重点介绍了精密小直径盲孔珩磨的原理、珩磨条座、珩磨杆的结构,可达到的加工精度,推广此项工艺应解决的问题及其展望。     

Scheduling algorithms for rapid imaging using agile Cubesat constellations

Distributed Space Missions such as formation flight and constellations, are being recognized as important Earth Observation solutions to increase measurement samples over space and time. Cubesats are increasing in size (27U, ～40?kg in development) with increasing capabilities to host imager payloads. Given the precise attitude control systems emerging in the commercial market, Cubesats now have the ability to slew and capture images within short notice. We propose a modular framework that combines orbital mechanics, attitude control and scheduling optimization to plan the time-varying, full-body orientation of agile Cubesats in a constellation such that they maximize the number of observed images and observation time, within the constraints of Cubesat hardware specifications. The attitude control strategy combines bang-bang and PD control, with constraints such as power consumption, response time, and stability factored into the optimality computations and a possible extension to PID control to account for disturbances. Schedule optimization is performed using dynamic programming with two levels of heuristics, verified and improved upon using mixed integer linear programming. The automated scheduler is expected to run on ground station resources and the resultant schedules uplinked to the satellites for execution, however it can be adapted for onboard scheduling, contingent on Cubesat hardware and software upgrades. The framework is generalizable over small steerable spacecraft, sensor specifications, imaging objectives and regions of interest, and is demonstrated using multiple 20?kg satellites in Low Earth Orbit for two case studies – rapid imaging of Landsat’s land and coastal images and extended imaging of global, warm water coral reefs. The proposed algorithm captures up to 161% more Landsat images than nadir-pointing sensors with the same field of view, on a 2-satellite constellation over a 12-h simulation. Integer programming was able to verify that optimality of the dynamic programming solution for single satellites was within 10%, and find up to 5% more optimal solutions. The optimality gap for constellations was found to be 22% at worst, but the dynamic programming schedules were found at nearly four orders of magnitude better computational speed than integer programming. The algorithm can include cloud cover predictions, ground downlink windows or any other spatial, temporal or angular constraints into the orbital module and be integrated into planning tools for agile constellations.     

一种适用于曲面结构的机器人制孔误差在线补偿技术

针对工业机器人应用于飞机零部件自动钻孔时各项误差累积造成制孔精度差的问题，提出一种利用单应关系计算机器人驱动坐标三维偏差，以在线补偿机器人制孔精度的方法。首先利用外部测量设备建立机器人制孔系统中各坐标系关系；在标定阶段，通过以一定倾斜角度固联于机器人末端的相机拍摄一幅安装于制孔工作平面上与刀轴正对的平面标定板图像，并据此完成基于单应变换的手-眼关系标定；在实际制孔过程中，机器人在测距传感器及相机的辅助下，从基准孔理论坐标对应的姿态，不断调整至基准孔正上方理想位置，通过手-眼关系计算基准孔实际位置对应的机器人驱动坐标，然后根据一组基准孔的机器人三维驱动误差，计算三维驱动误差变换矩阵，据此获得这组基准孔邻域范围内各待钻孔的机器人驱动坐标补偿量，从而实现待钻孔定位误差补偿。以飞机结构实验件为对象进行了模拟制孔验证，实验结果表明，补偿前待钻孔三维综合定位误差和法向误差测量值范围分别为2.28~2.85 mm和2.09°~3.93°，平均为2.55 mm和3.30°，补偿后制孔最大误差分别不超过0.30 mm和0.21°，满足自动制孔位置精度要求。     

壁挂式主频可调变截面小卫星结构设计与验证

针对多星并联布局“一箭多星”发射小卫星的模式，为降低星箭连接界面结构受力、提高卫星结构对不同运载火箭的主频适应性、提高星内设备安装空间利用率，本文设计了一种壁挂式主频可调变截面小卫星结构。对该卫星结构，开展了基于有限元方法的模态和静力分析验证，还开展了地面鉴定级振动试验验证和在轨飞行试验验证。分析和试验结果表明，壁挂式卫星结构相比底部连接式卫星结构，星箭连接界面受力可降低67.7%；在不增加卫星结构质量的前提下，仅通过安装或拆卸主传力路径上的部分连接螺钉，就能实现卫星3个方向一阶频率10 Hz左右的可调范围；采用沿运载火箭轴线方向横截面大小可变的变截面结构设计，可将星内设备安装空间的利用率由等截面卫星结构的49.1%提高到74.2%。     

带肋和出流孔通道换热研究

采用热色液晶瞬态测试技术测量了带肋和出流孔通道各壁面的换热系数分布,分析了雷诺数和出流比对换热系数的影响,其中雷诺数的变化范围是20000~80000,出流比的变化范围是0.3~0.6。结果表明:出流比的变化对各壁面均有较大影响,无出流孔带肋壁面的换热沿通道减弱,带肋和出流孔壁面的换热在通道入口处先增大之后沿通道减小;各壁面平均换热增强系数随雷诺数增大而减小。无出流孔的带肋壁面和侧壁的平均换热增强系数随出流比增大而减小,带肋和出流孔壁面的平均换热增强系数不随出流比变化而变化。     

小天体自主附着技术研究进展

基于国际上已实施的小天体探测任务和未来小天体附着探测技术的发展趋势,阐述了小天体自主附着的必要性及关键技术。首先回顾了已成功实施的小天体探测任务的特点,进而总结了小天体自主附着的难点问题,概括分析了小天体自主附着所涉及的关键技术及其研究进展,最后对未来小天体自主附着技术的研究热点和发展趋势进行了展望。     

A six-degree-of-freedom hardware-in-the-loop simulator for small spacecraft

This paper presents a novel six degree of freedom, ground-based experimental testbed, designed for testing new guidance, navigation, and control algorithms for the relative motion of nano-satellites. The development of innovative guidance, navigation and control methodologies is a necessary step in the advance of autonomous spacecraft. The testbed allows for testing these algorithms in a one-g laboratory environment. The system stands out among the existing experimental platforms because all degrees of freedom of motion are controlled via real thrusters, as it would occur on orbit, with no use of simulated dynamics and servo actuators. The hardware and software components of the testbed are detailed in the paper, as is the motion tracking system used to perform its navigation. A Lyapunov-based strategy for closed loop control is used in hardware-in-the loop experiments to successfully demonstrate the full six-degree-of-freedom system׳s capabilities. In particular, the test case shows a two-phase regulation experiment, commanding both position and attitude to reach specified final state vectors.     

基于STK的小卫星轨道交会设计研究

利用球面三角形的几何关系进行了基于STK(卫星工具包)的小卫星轨道交会的规划和设计。采用一种较为方便的轨道交会设计方法,并使用功能强大的专业STK软件来仿真和演示,取得了良好的仿真效果,能够较好地满足航天器轨道交会设计的要求,对于其它类型的轨道规划有一定的借鉴作用,为各种航天器的仿真研究提供了一种新的方法。     

一种多卫星编队飞行的准确定位方法

为实现多卫星编队飞行的准确定位，用微型扫描激光距离探测器(MS-LRF)确定卫星间的相对位置．并给出了不同的算法。该方法的精度高、速度快，无需坐标变换，其可靠性和可行性较高。     

A balloon-borne very long baseline interferometry experiment in the stratosphere: Systems design and developments

The balloon-borne very long baseline interferometry (VLBI) experiment is a technical feasibility study for performing radio interferometry in the stratosphere. The flight model has been developed. A balloon-borne VLBI station will be launched to establish interferometric fringes with ground-based VLBI stations distributed over the Japanese islands at an observing frequency of approximately 20?GHz as the first step. This paper describes the system design and development of a series of observing instruments and bus systems. In addition to the advantages of avoiding the atmospheric effects of absorption and fluctuation in high frequency radio observation, the mobility of a station can improve the sampling coverage (“uv-coverage”) by increasing the number of baselines by the number of ground-based counterparts for each observation day. This benefit cannot be obtained with conventional arrays that solely comprise ground-based stations. The balloon-borne VLBI can contribute to a future progress of research fields such as black holes by direct imaging.