推力室钎焊身部X射线数字成像检测技术

针对常规运载火箭发动机推力室钎焊身部钎焊质量检测需求,深入开展了钎焊身部X射线数字成像自动检测系统与检测工艺研究。研制开发了X射线数字成像自动检测系统,介绍了系统组成与特点。利用该系统开展了分区透照试验,确定了分区数量与机器人路径规划,完成了程序示教。开展了检测灵敏度试验,并与常规X射线胶片照相方法进行了试验对比分析。结果表明该检测系统与工艺可以满足检测要求,能有效检测出2 mm×1.5 mm未钎着缺陷与Φ0.5 mm冷却通道堵塞。与射线胶片照相手工拍片相比,其影像变形小、图像宽容度大,提高了缺陷检出率与检测可靠性及一致性,效率提升了3倍。利用该检测工艺检测通过的产品已经完成了试车及飞行任务考核。     

Enhanced multipath mitigation method based on multi-resolution CNR model and adaptive statistical test strategy for real-time kinematic PPP

This study proposes an enhanced multipath mitigation method based on multi-resolution carrier-to-noise-ratio (CNR) model and adaptive statistical test strategy for real-time kinematic precise point positioning (PPP) applications. The multi-resolution CNR model is established with GPS observation data collected from DOY 152 to 181 of 2019 by 230 globally distributed IGS stations, which used to analyze the relevant factors affecting CNR. Statistical results indicate that the CNR is not only related to the satellite elevation, but also closely related to the receiver types and specific satellite. The maximum difference between different receivers can reach 20 dB for the same satellite at the same elevation. In addition, the performance of the CNR is also obviously different between each satellite, and the maximum difference between different satellites is about 10 dB for the same receiver at the same elevation. Hence, in terms of the method which is based on CNR information for multipath detection and mitigation, the independence of receiver types, satellite and frequency must be considered. With the above analysis, this study developed a multi-resolution CNR model based on different receiver types, different satellites and different elevation firstly. Then, combined with the adaptive statistical test strategy which is based on the difference of CNR between inter-frequency and the difference of CNR between adjacent epochs, the multipath can be detected effectively. For the epoch which affected by multipath, the down-weighted strategy based on CNR is adopted to mitigate the influence of multipath on positioning. Real-time kinematic PPP data are collected to assess the proposed method, and the results demonstrate that the proposed method can detect the multipath effectively, and the detection rate can reach 90.28%. Moreover, after adopting the mitigation strategy, the RMS bias of the east, north and up components are improved about 19.95%, 17.89% and 23.07% compared to the original results, respectively. It is worth noting that this proposed method is also suitable for other GNSS, such as GLONASS and BDS, but the corresponding CNR model must be established simultaneously.     

Postcapture stabilization of space robots considering actuator failures with bounded torques

Space robotics is regarded as one of the most impressing approaches for space debris removal missions. Due to the residual momentum of debris, it is essential to stabilize the base rapidly after capture. This paper presents a novel control strategy for stabilization of a space robot in postcapture considering actuator failures and bounded torques. In the control strategy, the motion of the manipulator is not regarded as a disturbance to the base; in contrast, it is utilized to compensate for the limitation of the control torques by means of an inverse dynamical model of the system. Different scenarios where actuators are external mechanisms or momentum exchange devices have been carried out, and for actuator failures, both single- and two-actuator failures have been considered. Regarding to the performance of actuators, control torques are bounded. In cases that either single or two actuators have failed, the base can be stabilized kinematically when actuators are external mechanisms, but can only be stabilized dynamically when only momentum exchange devices are used. Finally, a space robot with a seven-degree-of-freedom manipulator in postcapture is studied to verify the validity and feasibility of the proposed control scheme. Simulation results show that the whole system can be stabilized rapidly.     

聚合物淬火介质CH-202M在钢铁零件淬火上的基础研究

 聚合物淬火介质冷却金属时于金属表面形成一层聚合物隔离膜,45钢和40Cr钢在不同浓度介质中淬火,可得到比水淬、油淬更大的淬透深度和更小的淬火变形,并可防止淬火开裂。淬火后的组织正常,机械性能符合要求。故表明,此种介质用于钢铁零件淬火非常有效。本文还对使用中的一些管理问题进行了阐明。     

Use of the radial velocity measurement in target tracking

A new sequential filtering algorithm that incorporates the radial velocity measurement into a Kalman filter, in the presence of correlated range and radial velocity measurement errors, is presented. An analysis is given concerning its asymptotic behavior on the basis of analysis of its stochastic controllability and observability. The simulation results verify the analysis and show that the new algorithm is superior to the conventional extended Kalman filter (EKF) and close to an ideal filter.     

重访机制驱动的多无人机协同动目标搜索方法

为实现多无人机高效捕获灰色任务区域内的移动目标,考虑传感器探测概率与虚警概率,提出了重访机制驱动的协同搜索规划（RMD-CSP）方法,以降低目标遗漏与误判概率。考虑无人机飞行性能约束,以最大化任务执行效能为目标建立多无人机协同搜索模型。根据目标先验信息初始化环境搜索信息图（包括目标概率分布图、环境不确定度图与环境搜索状态图）,利用无人机实时探测信息,基于贝叶斯准则持续更新搜索信息图。定制基于环境不确定度更新的重访机制,通过增加长时间未被重访区域的环境不确定度,引导无人机搜索该区域,降低移动目标的遗漏概率;定制基于目标函数权重更新的重访机制,引导无人机快速重访发现新的疑似目标的区域,对疑似目标进行再次确认,减少由于传感器虚警概率造成的目标误判概率。采用滚动时域规划架构,将搜索规划问题分解为一系列短时域规划问题,提升了求解效率。在典型任务想定下,通过数值仿真试验验证了所提方法的有效性。仿真结果表明,RMD-CSP能够在秒级时间内生成每个时域的搜索航迹,相比于光栅式搜索方法与标准的概率启发式搜索方法,能够引导无人机捕获更多的移动目标,同时减少误判次数,有效提升了多无人机协同搜索的任务效能。     

X射线天文卫星观测需求分析与控制总体设计

对X射线天文卫星观测需求进行了分析,提炼了观测任务对观测模式、源的高精度定位与对准、轨道、热控、测控数传等多项需求与约束;针对X射线观测的多需求、多约束难点,设计了集巡天观测、定点观测与小天区扫描观测于一体的观测模式,解决了一颗卫星同时实现全天扫描、银道面深度扫描、重要惯性区域扫描、重要及机遇目标深度观测以及伽马暴全天监测的多种观测需求的难题,该技术已在我国硬X射线调制望远镜卫星上得到应用.     

航天器平台-载荷-控制一体化协同研制

航天器任务能力的指标提升,对卫星系统设计的深入、精细以及集约要求更高。以系统性能最优为终极目标,围绕任务能力开展多学科一体化设计,进而引起的产品集成、验证模式的显著改变。本文对国内外航天器多学科一体化研制模式的发展和应用情况进行介绍,分析了一体化设计的需求和内涵,并对多学科一体化协同平台的实现及探索性应用进行了研究。     

有向拓扑下无径向速度测量的多导弹协同制导

针对多枚导弹在平面内从各自期望的方向同时击中移动目标问题,提出一种有向通信拓扑下无需导弹-目标径向速度测量且带视线角约束的分布式有限时间协同制导律。基于平面内导弹-目标相对运动方程建立带视线角约束的多导弹协同制导模型。基于二阶多智能体协同控制理论设计了视线方向上的制导律,可保证有向拓扑下多导弹的打击时刻在有限时间内达到一致。基于齐次系统稳定性理论和积分滑模控制理论设计了视线法向方向上的制导律,可保证多导弹击中移动目标且视线角在有限时间内收敛到期望值。仿真校验所设计的协同制导律在理想条件下可使有向拓扑下的多导弹从各自的期望方向同时击中移动目标。     

HCKF性能评估及其在传递对准中的应用

针对高阶容积卡尔曼滤波(HCKF)算法在传递对准中的应用问题,提出综合运用多变量函数泰勒级数展开和计算复杂度分析的性能评估方法。基于高阶球面-径向容积准则建立HCKF算法模型,并对其估计精度和计算量进行量化和对比分析：HCKF具有5阶泰勒级数展开精度且计算复杂度为O(n 4),综合性能优于高斯厄米特积分滤波(GHQF)和无迹卡尔曼滤波(UKF)。将三种非线性滤波算法应用到舰机大失准角传递对准系统中,摇摆台试验结果表明：HCKF的估计精度比UKF高17%,计算量比GHQF小2个数量级,与HCKF性能评估结果一致。