磨粒分析技术及其在发动机故障诊断中的应用

基于显微形态学方法的磨损微粒显微分析技术是近年来出现的解决发动机磨损故障诊断问题的新方法之一。应用形态学分析方法建立一套磨粒显微特征描述体系提取磨粒特征信息,作为磨粒识别的信息基础,可以准确地完成磨粒自动识别。基于发动机润滑系统磨粒分析的结果和颗粒摩擦学理论,比较准确地评估出发动机接触磨损部件的磨损状态,进而诊断或预测此类磨损故障;另外,此项分析诊断技术在发动机气路磨损故障诊断中也具有潜在的应用前景。      

ESA开展GEO上小碎片的调查

文章主要介绍了欧空局开展地球同步轨道(GEO)小碎片的调查情况及相应技术.     

Area-oriented coordinated trajectory planning of dual-arm space robot for capturing a tumbling target

The growing amount of space debris poses a threat to operational spacecraft and the long-term sustainability of activities in outer space. According to the orbital mechanics, an uncontrolled space object will be tumbling, bringing great challenge to capture and remove it. In this paper, a dual-arm coordinated ‘‘Area-Oriented Capture"(AOC) method is proposed to capture a non-cooperative tumbling target. Firstly, the motion equation of the tumbling target is established, based on which, the dynamic properties are analyzed. Then, the ‘‘Area-Oriented Capture"concept is presented to deal with the problem of large pose(position and attitude) deviation and tumbling motion. An area rather than fixed points/devices is taken as the object to be tracked and captured. As long as the manipulators' end-effectors move to a specified range of the objective areas(not fixed points on the target, but areas), the target satellite will be hugged by the two arms.At last, the proposed method and the traditional method(i.e. fixed-point oriented capture method)are compared and analyzed through simulation. The results show that the proposed method has larger pose tolerance and takes shorter time for capturing a tumbling target.     

Detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target

The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target. Therefore, it is necessary to reduce the target’s rotation to a rate at which capture can be accomplished by the space robot. In this paper, a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed. This strategy can reduce the target’s rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller. The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely. The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude. The main contributions of this paper are as follows: (1) The compliant control method is adopted to achieve a precise friction control, which can reduce the target angular velocity steadily; (2) The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task; (3) The detumbling strategy of dual-arm space robot is designed considering base attitude stabilization, realizing coordinated planning of the base attitude and the arms. The strategy is verified by a dual-arm space robot with two 7-DOF (degrees of freedom) arms. Simulation results show that, target with a rotation velocity of 20 (°)/s can be effectively controlled to stop within 30 s, and the final deflection of the base attitude is less than 0.15° without affecting the target capture task, verifying the correctness and effectiveness of the strategy. Except to the tumbling target capture task, the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.     

Investigation of Hypervelocity Impacts on Retrieved Surfaces by Direct Simulation Monte Carlo

Hypervelocity impacts on the retrieved Hubble Space Telescope (HST) solar array was investigated by our extended Direct Simulation Monte Carlo (DSMC) model and the result matches well with the measured data in most of the particle mass range. The revelation of the altitude dependence of particles flux onto the retrieved surfaces provides some insight in understanding the observed higher flux onto Mir space station relative to that onto Long Duration Exposure Facility (LDEF). Our analysis suggests that a slightly higher primary flux onto Mir space station would be possible even without taking into account the secondary impacts, as a result of the existence of the highly eccentric orbits of small-sized debris. It is, furthermore, predicted that 43% of the measured impact flux onto Mir station in PIE experiment may be from secondary impacts, and a corresponding 7% for the detectors in Echantillions experiment.     

空间碎片的形成,危害及防护

对空间碎片的形成，危害及航天防护等问题进行了讨论，简述了领域内的研究成果，包括基本概念、理论模型和设计方案，并对今后空间碎片研究的重要性和研究的内容进行了分析。     

磨粒监测与分析系统在航空发动机状态监控中的应用(英文)

磨损颗粒是研究机器磨损状态时最直接、最重要的信息元 ,通过对滑油中的磨粒进行监测与分析以判断机械设备的磨损状况 ,可以监测并预防机械设备的磨损故障。本文介绍的磨粒监测与分析系统 ( DMAS)具有制谱简单、自动化程度高、能及时准确预报及诊断机器的各种磨损类故障等特点 ,可以有效地保障机器安全可靠地运行。本文详细地阐述了这套系统的基本原理、软硬件组成 ,以及在航空发动机磨损状态监测中的应用     

复杂背景下磨粒显微图像分割

针对DMAS系统中复杂背景下磨粒图像的自动分割问题，根据磨粒图像的相关特征，充分利用领域知识，基于图像分割和边界跟踪的思想，选取了适合磨粒图像分割的最大类间方差阈值法，并结合腐蚀、膨胀等图像处理技术，实现了复杂背景下磨粒图像的有效分割和目标提取。最后算例表明了本方法的简洁有效性。本文研究将对进一步展开磨粒识别和机械设备故障诊断研究工作提供前提和依据。     

Will space run out of space? The orbital debris problem and its mitigation

An appraisal of current and future risks from space debris is presented with the aid of calculations carried out by the MASTER model. The efficacy of various technical options -- such as fuel venting, de-orbiting and use of a graveyard orbit -- for counteracting the problem is discussed. The article then focuses on governmental and international cooperative measures and looks at the recent work done by subcommittees of the UN COPUOS.     

空间碎片减缓策略效果仿真

根据机构间空间碎片协调委员会(IADC)和欧空局(ESA)的空间碎片减缓要求,在建立航天发射、爆炸和碰撞模型,以及碎片演化机制的基础上,对常规发射(BAU)、禁止在轨爆炸(NO-EX)和全面减缓(MIT)三种空间碎片减缓策略条件下,对2000~2100年空间碎片环境进行了仿真计算。结果表明,禁止航天器在轨爆炸、对失效的卫星和火箭上面级实施离轨操作,以及在航天器的发射和运行中不产生或抛弃分离物等减缓措施是限制空间碎片数量增长的有效方法。