胶接连接件应力分析新模型与新方法

在工程梁理论基础上根据力法变分原理得到薄壁结构胶接接头应力分布的解析闭合解,克服依照传统剪滞理论所得之结果不能满足边界条件的缺点,指出使胶接接头失效的真正原因是接头端部的剥离正应力,从而为胶接接头设计提供正确依据。     

操作参数对组合式吸热器热性能的影晌

针对3种不同相变温度的相变材料组成的组合吸热器,建立了相应的物理模型,给出了数值求解方法,计算了工质入口温度、工质流速及输入功率等操作参数对组合式吸热器热性能的影响,得到了容器壁面最高温度、工质出口温度、换热管总相变蓄热材料(PCM)熔化率等结果.结果表明操作参数对吸热器热性能有较大的影响,合理选取这些参数对吸热器的正常运行是非常必要的,结果可以用于指导吸热器的设计.      

神经外科手术机器人灵活性分析

开发了用于神经外科手术的五自由度机器人BH600.从神经外科立体定向手术的需求出发,分析了该机器人的灵活性.用服务球和服务区概念给出了五自由度机器人工作空间任意点的灵活度定义,提出了工作空间灵活性的分析方法.通过数值计算和图形显示给出了工作空间的灵活度分布,采用机器人物理样机进行实验,对分析结果进行了验证.掌握灵活度的空间分布,可以为手术路径规划提供可靠的依据.      

GALILEO接收机中BOC(1,1)信号的捕获

BOC(1,1)(Binary-Offset-Carrier)信号相关函数中的零值会使接收机判定没有捕获到信号.为了完全捕获到BOC(1,1)信号,从副载波相位和码相位角度出发,提出了一种3路并行捕获方法.通过数字仿真得到了BOC(1,1)和扩频码的相关函数图,比较了二者相关函数的峰值.推导了BOC(1,1)相关函数的解析式,给出了相关函数中的零点位置和峰值位置,比较了BOC(1,1)和扩频码的相关函数数值及捕获.3路本地BOC信号以其中一路相位为基准,另外2路相位分别超前、滞后该路.给出了3路本地信号的生成方法及捕获的结构框图.仿真结果表明,捕获码相位差在半个码片内时,BOC(1,1)信号的捕获率从33.3%提高到100％,码相位捕获范围从1/6码片增大到1/2码片.该方法可为跟踪环路提供相位信息,适用于BOC(n,n)信号的捕获.      

Design of Electrical/Mechanical Hybrid 4-Redundancy Brushless DC Torque Motor

This article presents a novel electrical/mechanical hybrid 4-redundancy brushless DC torque motor (BLDCM), which has found applications in direct drive actuators (DDA) of aerial vehicles. This motor is characteristic of electrical/mechanical hybrid 4-redundancy by securing two stators along with two rotors on the same shaft. Each stator contains two sets of windings embedded in separated slots. Furthermore, compared to the scheme of two electrical dual-redundancy BLDCMs linked by a mechanical transmission, the proposed motor has lower volume and lighter weight, eliminates the nonlinearity caused by the gap of the mechanical transmission, moderates the requirement for the torque balance between redundancies and reduces the cogging torque by shifting the magnets. Both magnetic circuit calculation and the finite element analysis (FEA) of the electromagnetic field are conducted to optimize the design process. A prototype motor has been produced and tested. The results indicate that its performances comply with the requirements presented by designers. Moreover, the position frequency response of the prototype in the DDA's unloaded situation has also demonstrated the fulfillment of desired dynamic characteristics.     

Comprehensive outage compensation of real-time orbit and clock corrections with broadcast ephemeris for ambiguity-fixed precise point positioning

The main challenge in real-time precise point positioning (PPP) is that the data outages or large time lags in receiving precise orbit and clock corrections greatly degrade the continuity and real-time performance of PPP positioning. To solve this problem, instead of directly predicting orbit and clock corrections in previous researches, this paper presents an alternative approach of generating combined corrections including orbit error, satellite clock and receiver-related error with broadcast ephemeris. Using ambiguities and satellite fractional-cycle biases (FCBs) of previous epoch and the short-term predicted tropospheric delay through linear extrapolation model (LEM), combined corrections at current epoch are retrieved and weighted with multiple reference stations, and further broadcast to user for continuous enhanced positioning during outages of orbit and clock corrections. To validate the proposed method, two reference station network with different inter-station distance from National Geodetic Survey (NGS) network are used for experiments with six different time lags (i.e., 5 s, 10 s, 15 s, 30 s, 45 s and 60 s), and one set of data collected by unmanned aerial vehicle (UAV) is also used. The performance of LEM is investigated, and the troposphere prediction accuracy of low elevation (e.g., 10–20degrees) satellites has been improved by 44.1% to 79.0%. The average accuracy of combined corrections before and after LEM is used is improved by 12.5% to 77.3%. Without LEM, an accuracy of 2–3 cm can be maintained only in case of small time lags, while the accuracies with LEM are all better than 2 cm in case of different time lags. The performance of simulated kinematic PPP at user end is assessed in terms of positioning accuracy and epoch fix rate. In case of different time lags, after LEM is used, the average accuracy in horizontal direction is better than 3 cm, and the accuracy in up direction is better than 5 cm. At the same time, the epoch fix rate has also increased to varying degrees. The results of the UAV data show that in real kinematic environment, the proposed method can still maintain a positioning accuracy of several centimeters in case of 20 s time lag.     

结合TEC的泵驱两相温控系统的空间应用

为满足天舟一号货运飞船(T Z1)蒸发冷凝科学实验的控温需求，采用半导体制冷片(TEC)和泵驱两相回路结合的控温系统实现了冷凝台-5~40 ℃(±0.2 ℃)的控温要求。对TEC和平行流换热器进行了研究，结果表明该系统能够满足环境温度等于30 ℃工况下的制冷和散热要求。测试结果表明，平行流换热器在地面和在轨的换热相当，说明重力的影响几乎可以忽略。     

民用飞机地面支援设备/工具清单编制方法研究

民用飞机地面支援设备/工具清单的编制是一项极其重要而又繁杂的工作。研究清单的编制原则、设备/工具的确定方法、清单的主要内容以及清单编制工作流程,可为地面支援设备/工具清单的编制工作提供参考。     

基于气动性能优化的涡轮叶顶新型密封构型研究

针对涡轮叶顶密封性能的提高,对带圆形凹槽迷宫密封进行了构型优化研究。分析了不同压比时圆形凹槽数量、尺寸及分布对密封性能以及对涡轮做功效率的影响,初步探索了圆形凹槽降低损失的机理,给出了最佳的凹槽排列方案。结果表明,圆形凹槽的容积效应使泄漏流发生小角度偏转,降低了泄漏损失;压比增大,凹槽的节流能力减弱;所得凹槽最佳排列方案在压比为1.2时,泄漏系数降低了7.14%,效率提高了0.59%;单个凹槽半径由1mm增大到5mm,泄漏系数相对于光滑密封减小5.8%,效率增加0.35%。