Two-maneuver indirect contingency return from a low lunar orbit

The problem of contingency return from the low lunar orbit is studied. A novel two-maneuver indirect return strategy is proposed. By effectively using the Earth’s gravity to change the orbital plane of the transfer orbit, the second maneuver in the well-known three-maneuver return strategy can be removed, so the total delta-v is reduced. Compared with the single-maneuver direct return, our strategy has the advantage in that the re-entry epoch for the minimum delta-v cost can be advanced in time, with a minimum delta-v value similar to that of the direct return. The most obvious difference between our strategy and the traditional single- or multiple- maneuver strategies is that the complete transfer orbit is a patch between a two-body conic orbit and a three-body orbit instead of two conic orbits. Our strategy can serve as a useful option for contingency return from a low lunar orbit, especially when the delta-v constraint is stringent for a direct return and the contingency epoch is far away from the return window.     

高重合度齿轮传动系统的振动参数稳定性

研究了高重合度齿轮转子-滚动轴承传动系统的振动强度稳定性以及振动轨道稳定性随系统参数的变化规律。通过振动强度参数稳定域的计算,量化了高重合度齿轮副对齿轮转子 滚动轴承传动系统稳定性提升的贡献大小。结果发现在转子质量偏心较小的条件下,高重合度齿轮系统的振动强度稳定性要比普通重合度齿轮系统提升很多;但在转子质量偏心较大时,高重合度齿轮副的采用对传动系统参数稳定域的扩张并没有显著贡献。通过振动轨道稳定性全局分岔图的计算,明确了滚动轴承游隙、转子质量偏心等参数对高重合度齿轮转子-滚动轴承系统振动轨道稳定性的影响规律,获得了系统各种稳定周期轨道及非周期轨道与对应参数区间的映射关系。      

Autonomous navigation to quasi-periodic orbits near translunar libration points

Libration-point missions have been very useful and successful. Due to the unstable nat-ures of most of these orbits, the long-time stationkeeping demands frequent maneuvers and precise orbit determinat...     

智能手机广域精密定位研究

智能手机作为位置服务的重要载体，由于其天线结构等因素，导致利用手机原始观测值进行定位不能满足高精度定位的需求。针对这一问题，提出了利用广域增强技术，提高手机单频原始观测值实时定位精度的方法。首先，针对手机观测值周跳较为严重的问题，对单频载波相位观测值进行了周跳探测。然后，利用手机观测值获取的伪距、载波相位以及IGS站播发的轨道和钟差改正实现增强定位。实验结果表明，定位精度收敛到1m约需要20min，收敛后水平方向和垂直方向精度分别提高了66.7%和28.9%，平面精度达到1.5m。     

New trade tree for manned mars missions

Recent studies on human missions to Mars suggest revisiting the parameters that have the most important impact on the complexity, the initial mass in low Earth orbit, the risks and the development costs for the first journey to the red planet. In the last NASA reference mission, a trade tree is proposed.     

A residual based adaptive unscented Kalman filter for fault recovery in attitude determination system of microsatellites

This paper presents an adaptive unscented Kalman filter (AUKF) to recover the satellite attitude in a fault detection and diagnosis (FDD) subsystem of microsatellites. The FDD subsystem includes a filter and an estimator with residual generators, hypothesis tests for fault detections and a reference logic table for fault isolations and fault recovery. The recovery process is based on the monitoring of mean and variance values of each attitude sensor behaviors from residual vectors. In the case of normal work, the residual vectors should be in the form of Gaussian white noise with zero mean and fixed variance. When the hypothesis tests for the residual vectors detect something unusual by comparing the mean and variance values with dynamic thresholds, the AUKF with real-time updated measurement noise covariance matrix will be used to recover the sensor faults. The scheme developed in this paper resolves the problem of the heavy and complex calculations during residual generations and therefore the delay in the isolation process is reduced. The numerical simulations for TSUBAME, a demonstration microsatellite of Tokyo Institute of Technology, are conducted and analyzed to demonstrate the working of the AUKF and FDD subsystem.     

一种新型充气式重力梯度杆的研制和在轨展开试验

文章对中国“新技术验证一号”卫星搭载的一种新型充气式重力梯度杆的研制和在轨试验情况进行了介绍。重力梯度杆在小卫星控制领域中具有较好的应用前景,而充气结构具有轻质、占用空间小、发射成本低的特点,采用充气式重力梯度杆可避免传统机械式重力梯度杆质量重、尺寸大和机构复杂的缺点,它以充气伸展臂为主要结构形式,通过充气展开伸直成为重力梯度杆,既作为卫星重力梯度杆又通过在轨试验验证空间充气展开结构的性能。在轨试验结果表明充气式重力梯度杆展开稳定、有序、性能可靠,可以满足小卫星的性能和功能要求。该试验也是中国首个成功的充气展开结构在轨技术验证试验,标志着中国的充气展开结构技术初步具备了工程化能力。     

太阳帆日心定点悬浮转移轨道设计

研究了太阳帆航天器日心定点悬浮轨道(HFDO)的转移轨道设计问题,以球坐标形式建立了太阳帆的动力学模型,基于该模型给出在日心悬浮轨道基础上实现定点悬浮的条件,提出了一种实现日心定点悬浮的转移轨道设计方法。首先,确定定点悬浮的位置;然后,设计经过该位置的绕日极轨轨道;最后,实施轨道减速实现定点悬浮,并给出了解析形式的轨道控制律。结合太阳极地观测任务,设计了定点悬浮在太阳北极1AU处的太阳帆转移轨道。仿真结果表明:该轨道转移方案总耗时3.5年,太阳帆定点到黄北极距日心1AU处,此后只要保持太阳光垂直照射帆面,即可维持稳定的悬浮状态。     

空间在轨服务物理仿真系统有效性研究

研究典型在轨服务机器人气浮式物理仿真系统的有效性问题。针对在轨逼近和操作（抓取、移动和释放）这两种关键工作模式,从动力学原理和干扰下响应的一致性两个方面,系统分析了仿真数据的有效性。基于对误差模型的分析,研究仿真系统中干扰因素对仿真数据有效性的影响,给出物理仿真系统的可应用条件。将该结果应用到具体物理仿真系统中,可以对物理仿真试验起指导作用。     

Attitude determination of planetary exploration rovers using solar panels characteristics and accelerometer

In this study, we propose a new attitude determination system, which we call Irradiance-based Attitude Determination (IRAD). IRAD employs the characteristics and geometry of solar panels. First, the sun vector is estimated using data from solar panels including current, voltage, temperature, and the normal vectors of each solar panel. Because these values are obtained using internal sensors, it is easy for rovers to provide redundancy for IRAD. The normal vectors are used to apply to various shapes of rovers. Second, using the gravity vector obtained from an accelerometer, the attitude of a rover is estimated using a three-axis attitude determination method. The effectiveness of IRAD is verified through numerical simulations and experiments that show IRAD can estimate all the attitude angles (roll, pitch, and yaw) within a few degrees of accuracy, which is adequate for planetary explorations.