工程系统的实时可靠性评估与预测技术

 作为预测维护策略的重要技术基础,寿命预测近年来得到越来越广泛的关注,实时可靠性评估与预测是一种有效的寿命预测技术。综述工程系统的实时可靠性评估与预测方法,调研实时可靠性评估与预测方法的应用实例,并探讨该研究领域中存在的问题及未来的研究方向。     

超高强度300M钢起落架主支柱激光增材修理应用研究

某型民用飞机起落架开展疲劳试验,进行到105857起落时其主支柱组件主传力部位出现长度34mm裂纹,该支柱材料为300M钢(模锻件)。手工打磨裂纹部位,清除裂纹后在零件上形成长约40mm、宽约8mm、深度30～44mm的长条形直通孔,应用A100材料,利用机器人手臂激光熔化沉积增材制造技术开展激光增材修复工艺研究,完成了裂纹的修补,最终成功完成后续135000起落疲劳试验。验证了超高强度钢起落架主承力部件增材修补工艺的技术可行性,表明激光增材修复技术应用于超高强度钢飞机构件的修理具有较广阔的前景。     

航天器在轨寿命预测与可靠性评价

文章重点分析了航天器在轨寿命和可靠性的影响因素,提出了航天器在轨寿命预测和可靠性评价的基本研究思路并分析了研究的内容,提出了航天器基础在轨寿命的概念。     

RadioAstron orbit determination and evaluation of its results using correlation of space-VLBI observations

A crucial part of a space mission for very-long baseline interferometery (VLBI), which is the technique capable of providing the highest resolution images in astronomy, is orbit determination of the mission’s space radio telescope(s). In order to successfully detect interference fringes that result from correlation of the signals recorded by a ground-based and a space-borne radio telescope, the propagation delays experienced in the near-Earth space by radio waves emitted by the source and the relativity effects on each telescope’s clock need to be evaluated, which requires accurate knowledge of position and velocity of the space radio telescope. In this paper we describe our approach to orbit determination (OD) of the RadioAstron spacecraft of the RadioAstron space-VLBI mission. Determining RadioAstron’s orbit is complicated due to several factors: strong solar radiation pressure, a highly eccentric orbit, and frequent orbit perturbations caused by the attitude control system. We show that in order to maintain the OD accuracy required for processing space-VLBI observations at cm-wavelengths it is required to take into account the additional data on thruster firings, reaction wheel rotation rates, and attitude of the spacecraft. We also investigate into using the unique orbit data available only for a space-VLBI spacecraft, i.e. the residual delays and delay rates that result from VLBI data processing, as a means to evaluate the achieved OD accuracy. We present the results of the first experience of OD accuracy evaluation of this kind, using more than 5000 residual values obtained as a result of space-VLBI observations performed over 7 years of the RadioAstron mission operations.     

Guidepost-based autonomous orbit determination method for GEO satellite

Guidepost-based navigation system is a novel autonomous orbit determination method for the GEO satellite. The system is achieved by using the camera imaging function to obtain the guidepost images and the GNSS signal receiver to obtain the pseudoranges between the GEO and the navigation satellites. Due to the high altitude of GEO satellite and the time-varying sunlight condition in the space environment, it may be difficult to obtain object image points and the distance measurements of GNSS because of the weak visibility of the guideposts. To deal with the problem, a novel integrated orbit determination system is presented. The Earth landmarks, the in-orbit spacecraft and GNSS navigation satellites whose line-of-sights and the distance can be easily obtained are used at the same time as information for the GEO satellite navigation based on the observability conditions analysis. The observability of the GEO satellite navigation system is analyzed through the physical observability, the mathematical observability and the engineering observability through the observing geometry, the rank of observability matrix and the Cramer-Rao lower bound (CRLB) respectively. Besides, the maximum correntropy unscented Kalman filter (MCUKF) algorithm is applied to improve the estimation stability of the system in the presence of non-Gaussian noises. The simulation indicates the feasibility of the proposed scheme.     

卫星地球-射频敏感器组合定姿滤波算法研究

基于卡尔曼滤波理论以及卫星定姿技术的发现状况，对卡尔曼滤波在静止轨道三轴稳定卫星红外地球敏感器和射频敏感器组合定姿中的应用作了一定的研究。建立了静止轨道三稳定卫星姿态动力学模型和红外－射频敏感器组合定姿的姿态量测模型，针对这一模型，应用推广的卡尔曼滤波进行姿态估计，并进行了计算机仿真，验证了滤波方法应用于静止轨道三轴稳定卫星红外地球敏感哭和射频敏感器组合定姿的有效性和优越性。     

交会相对运动确定的新方法

本文叙述空间交会过程中相对运动参数测定的新算法。在测量目标的相对距离和方向的基础上,借助于追踪航天器上的地球敏感器和太阳敏感器,就能直接确定在目标轨道坐标系中相对运动的参数。为此,测量系统可以不含陀螺惯性平台。     

压强冲量系数法确定标准发动机燃烧终点

对不同型号的Φ127mm发动机燃烧终点的确定方法进行研究，采用平均压强系数法对上千发不同型号BSF－Φ127mm发动机试验数据进行数理统计，并与以往的数据进行比较，燃烧时间测试误差在0.5%以内，平均压强冲量系数法的准确性可达80％以上。换算到标准压强条件下，平均压强冲量系数法的计算精度优于切线法的计算精度，并作出了计算验证。此方法能应用于各种类型BSF－Φ127mm发动机试验，具有一定的推广价值。     

目标天体极轨道卫星的轨道寿命

星际探测器轨道的特征与探测目的密切相关，对目标天体两级地区进行探测显然采用的是极轨道（或接近极轨道）。对于这类卫星（或称轨道器），如果轨道半长径较大，则会因第三体报骚动国导致轨道偏心率增大，使其近星距减小到等于目标天体的赤道半径而落到该天体上，结束其运动寿命，即使目标天体不存在大气（如月球等）亦会如此。     

Galileo real-time orbit determination with multi-frequency raw observations

Real-time GNSS-based applications require corresponding real-time orbit products. While traditional GNSS orbits are generated with the dual-frequency IF (Ionosphere-Free) model, the increase of multi-frequency signal satellites brings new challenges for the data processing. Therefore, real-time orbit determination with the multi-frequency UC (Uncombined) model is introduced in this study considering its flexibility. With the derived mathematical model conforming to IGS (International GNSS Service) dual-frequency clock definition and one-week triple-frequency Galileo observation data from 90 IGS network stations, the convergence and accuracy of real-time orbits is assessed and the characteristics of satellite IFCB (Inter-Frequency Clock Bias) are analyzed. Results indicate that the model differences, including dual-frequency IF model, dual-frequency UC model and triple-frequency UC model, contribute to only cm-level differences with CODE (Center for Orbit Determination in Europe) final orbits after a convergence time of around 12 h. The constellation-mean RMS (Root Mean Square) differences of the converged real-time orbits with the CODE final orbits reaches about 5.0 cm, 7.0 cm and 5.0 cm for the radial, tangential and normal directions. The convergence of satellite IFCB is much faster than that of satellite orbit, which reflects a loose correlation between these two parameters. While the Galileo satellite IFCB are temporally stable, the modeling of satellite IFCB may be unreliable when over constrained and becomes even more unstable with commonly encountered datum changes. In summary, real-time GNSS orbit determination with multi-frequency raw observations is feasible and extendable with proper treatment of IFCB.