低温环境下材料膨胀系数和润滑对望远镜负载扭矩的影响

为了深入研究望远镜的负载扭矩随着温度降低而增大的机理,提高低温下伺服系统的跟踪精度。首先分析了轴承摩擦扭矩的各种影响因素和低温对负载扭矩的影响,研究了润滑剂黏度随温度的变化规律,试验对比了有无添加润滑脂情况下负载扭矩的变化,结果表明在低温下无润滑脂时负载扭矩的波动减少并且线性度提高。其次分析了轴承摩擦扭矩和间隙的关系,采用电阻应变片法测量不同材料在不同温度下的热膨胀系数,建立起材料膨胀系数和扭矩的相关特性,结果表明低温下负载扭矩是常温下的6.67倍,而材料尺寸的最大缩短量达到960με。通过对低温负载扭矩机理的研究,可为低温环境下望远镜的精确控制提供理论和试验数据。     

Influence of magnetic reluctances of magnetic elements on servo valve torque motors

The current research of electro-hydraulic servo valves mainly focuses on the vibration, pressure oscillating and source of noise. Unfortunately, literatures relating to the study of the influence of the magnetic reluctances of the magnetic elements are rarely available. This paper aims to analyze the influence of the magnetic reluctances of the magnetic elements on torque motor. Considering these magnetic reluctances ignored in previous literatures, a new mathematical model of servo valve torque motor is developed and proposed based on the fundamental laws of electromagnetism. By using this new mathematical model and the previous models, electromagnetic torque constant and magnetic spring stiffness are evaluated for a given set of torque motor parameters. A computer simulation by using AMESim software is also performed for the same set of torque motor parameters to verify the proposed model. The theoretical results of electromagnetic torque constant and magnetic spring stiffness evaluated by the proposed model render closer agreement with the simulation results than those evaluated by the previous models. In addition, an experimental measurement of the magnetic flux densities in the air-gaps is carried out by using SFL218 servo valve torque motor. Compared with the theoretical results of the magnetic flux densities in the air-gaps evaluated by the previous models, the theoretical results evaluated by the proposed model also show better agreement with the experimental data. The proposed model shows the influence of the magnetic reluctances of the magnetic elements on the servo valve torque motor, and offers modified and analytical expressions to electromagnetic torque constant and magnetic spring stiffness. These modified and analytical expressions could provide guidance more accurately for a linear control design approach and sensitivity analysis on electro-hydraulic servo valves than the previous expressions.     

永磁齿轮转矩特性研究

计算了新型传动机构永磁齿轮传动机构的磁场,根据从动轮处于不同位置时的转矩曲线和传动机构负载线,分析了转速变化。对主动轮和从动轮同步旋转进行计算,得出从动轮力矩变化曲线,分析了力矩波动与两齿轮相对磁极轴线夫角关系。最后对传动机构进行了实验验证。研究表明,该传动机构转矩波动很小,具有优异的传动性能。     

新型耐高温磁力联轴器传递转矩的数值计算

磁力联轴器的出现,彻底解决了某些机械装置中动密封存在的泄漏问题。为了进一步拓宽采用高性能钕铁硼稀土永磁体的磁力联轴器的使用范围,借鉴感应式异步电机的工作原理,研制了一种不同于以往利用永磁体同性相斥、异性相吸原理工作的同步式磁力联轴器的异步感应式耐高温磁力联轴器。为了计算其传递的转矩,将其外转子变换为等效的异步电机的定子绕组,运用数值方法,初步分析了联轴器内部涡流场的分布,并最终得出了其所传递转矩的计算方法。     

低温状态下的材料法向发射率测量

研究了在-60~50℃条件下准确测量材料法向发射率的方法。基于发射率定义建立了材料法向发射率测量模型。为屏蔽环境杂散辐射与大气吸收的影响,利用真空液氮背景通道搭建了低温状态下材料发射率测量装置。测量了氧化铜与高发射率陶瓷两种样品的法向发射率随温度、波长的变化情况。结果表明:两种样品的法向光谱发射率均随波长增加而降低;随温度的升高,氧化铜样品法向积分发射率稳定为0.850±0.012,陶瓷样品的法向积分发射率降低了0.124。最后,实现了低温状态下红外光谱辐射的高精度采集,对低温状态下材料法向光谱发射率测量结果的不确定度进行了评定,得到的结果显示其相对扩展不确定度小于6.0%。     

土压平衡式盾构机刀盘转矩的理论建模与分析

在对盾构原理及土力学分析的基础上,建立了盾构机刀盘转矩各构成部分的模型和计算公式并进行分析求解,同时对盾构转矩与系统其他因素的相互关系进行了分析,通过实例进行模型对比分析和验证。结果表明,所建模型及计算公式有较高的精准度,对盾构设计与施工有重要参考价值。     

钢水连续测温传感器动态测温的仿真研究

在分析钢水连续测温传感器传热过程的基础上,建立了传感器的二维轴对称非线性非稳态传热模型。采用有限元方法对钢水连续测温传感器的动态测温过程进行了仿真研究,并分析了传感器插入深度、热物性参数、预热温度、边界条件等因素对测温准确性和动态特性的影响。实验结果表明,仿真值与测量值相比最大误差小于5℃,所建模型是正确的。传感器的插入深度及其变化率对动态测温误差、测量响应速度,测温的准确性均有较大的影响,其最小插入深度应为250 mm。传感器动态测温误差随着热容或密度的增大而增大,随着导热系数的增大而减小。传感器初始预热温度每提高10℃,最大动态测温误差减小约5℃,响应时间缩短约2s。这些结果可为传感器的优化设计和实际使用提供理论依据。     

低温球阀阀杆密封填料的试验与研究

通过试验测试了阀杆柔性石墨与聚四氟乙烯复合填料的低温性能,介绍了复合填料的装填方式及防止填料挤入阀杆孔弧形挡圈的使用。     

镍系低温用钢缺口韧性的研究

通过对材料的试验检测及金相与电子断口分析,总结出调质工艺、正火 调质及不同的加热与回火温度对LF3锻钢和LC3铸钢低温韧性的影响。为改善这2种钢低温韧性的稳定性提供了良好的方法。     

Theoretical analysis and experiments of axial flux pm motors with minimized cogging torque

This paper deals with analysis and experiments of an axial flux PM (AFPM) brushless dc motor with minimized cogging torque. Recently, many optimal designs for the AFPM motor have been done by finite element (FE) analysis, but such analysis is time-consuming. In this study, the equation of magnetic flux lines existing between PMs and core is assumed mathematically and the minimum cogging torque is calculated theoretically and geometrically without FE analysis. The form of equation is assumed to be a 2^nd order polynomial. The skew angle that makes the cogging torque minimized is calculated theoretically, and the value of minimum cogging torque is compared with the results obtained by FE analysis and experiments. The maximum cogging torque of a proposed AFPM motor has the smallest value approximately at a skew angle of 4° in both the theoretical and FE analysis. Compared with the non-skewed motor, the cogging torque of the skewed motor can be decreased to over 90%, which has a value of 5% of the rated torque. Two types of stator cores, with the skew angle of 0° and 4°, are analyzed, manufactured, and tested experimentally. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Dong Ho Kim received B.S. and M.S. degrees in Mechanical Engineering from Pusan National University in 1982 and 1984, respectively. He then received his Ph.D. degree from Yonsei University in 2007. Dr. Kim is currently a Professor at the Department of Automation and Robots at Kyonggi Institute of Technology in Gyeonggi, Korea. His research interests are in the area of production automation. Jong Hyun Choi received B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Yonsei University, Seoul, Korea, in 1996, 1998, and 2006, respectively. Dr. Choi is currently a post-doctor at the School of Mechanical Engineering at Yonsei University. His research interests are in the area of electromagnetic actuators and magnetic levitation system. Chang Woo Son received a B.S. from Kyungwon University, Seoul, Korea, in 2006, and his M.S. degree from Yonsei University in 2008, all in mechanical engi-neering. He is currently a research engineer at DA Laboratory of LG Electronics in Seoul, Korea. His research interests are in the area of electromagnetic actuators. Yoon Su Baek received B.S. and M.S. degrees from Yonsei University, Seoul, Korea, in 1979 and 1981, respectively, and M.S. and Ph.D. degrees from Oregon State University in 1986 and 1990, respectively, all in mechanical engineering. He worked for Samsung Heavy Industry Ltd. as head research engineer at Mechatronics Research Center from 1990 to 1993. Dr. Baek is currently a Professor at the School of Mechanical Engineering at Yonsei University. His research interests are motion devices and robotics, especially relating to multi-D.O.F. actuators. He is also interested in magnetic brake and levitation system.     

低温超导全张量磁梯度测量系统研制与应用

首先介绍了低温超导全张量磁梯度测量系统的组成、仪器布局和硬件连接;然后分析了系统研制过程中各模块测试结果,包括测控系统噪声测试和SQUID灵敏度测试,指出组成系统的SQUID传感器的一致性至关重要;其次,详细阐述了系统地面静、动态实验,测试了系统动态范围、测量精度和稳定性,系统静态实验磁梯度测量精度均优于±30 pT/m;最后,在江苏丹阳进行了野外飞行试验,根据DZ/T 0142—2010航空磁测技术规范,测量结果表明各张量分量重复线内符合精度优于±25 pT/m,每条测线动态测量灵敏度均值均优于±30 pT/m。此套系统以达到工程样机水平,大大提高了低温超导全张量测量系统的实用化程度,为我国在低温超导航磁测量领域接下来的研究工作打下了坚实的基础。     

锅炉设备低温腐蚀原因及对策措施

锅炉尾部受热面的硫酸腐蚀被称为低温腐蚀,尾部受热面区段的烟气和管壁温度比较低.从低温腐蚀的形成以及使用燃料和水温方面阐述了锅炉设备低温腐蚀的原因及有效处理锅炉腐蚀现象的措施,有效的防止了锅炉设备低温腐蚀.     

磁悬浮式纳米级微动工作台的理论分析与建模研究

磁悬浮式微动工作台由于运动平台和驱动机构采用非接触式的磁悬浮驱动技术而易于实现大范围纳米级精度的微运动。本文构建了一种新型的磁悬浮微动工作台，从理论上对磁悬浮式微动工作台的运动机理进行了详尽分析，建立了磁悬浮式微运动的电磁驱动模型，用Matlab对磁悬浮式微动工作台的运动控制进行了仿真研究，结果表明，设计的磁悬浮式微动工作台能达到纳米级的微运动。本文的研究成果为磁悬浮式微动工作台的设计及其控制提供了理论基础。     

光纤宏弯损耗与温度传感的理论分析

为了从理论上分析和推导光纤宏弯曲损耗与温度的关系,采用了一个平板波导近似的弯曲损耗模型,对单模光纤的宏弯曲损耗和弯曲半径、波长以及温度的关系进行了分析和仿真,得到了弯曲损耗随弯曲半径的减小而增大,波长的增大而增大,温度的升高而减小的结论。该结论对光纤弯曲损耗在温度传感器方面的应用研究起着重要的参考作用。     

基于sEMG和肌肉骨骼模型的手指多关节力矩耦合分析

手指内部力矩受表面肌电信号、肌力、手部姿态等因素影响而无法直接获取,为了实时且准确地获取手指各关节力矩以及耦合力矩并应用于手部康复机器人的交互控制中,提出了一种基于表面肌电信号和肌肉骨骼模型的手指多关节力矩和耦合力矩分析与实时获取方法。首先设计了自适应手指关节角度采集系统,通过实验同步采集指浅屈肌与指伸肌的肌电信号以及手指各关节的角度数据,建立手指多关节力矩模型,从而获取手指各关节力矩。然后建立手指D-H模型,结合虚功原理获取手指的耦合力矩。最后,辨识了手指多关节力矩模型的参数,并通过OpenSim软件获取了仿真力矩。计算力矩与仿真力矩的对比结果显示：4名被试3个关节力矩的均方根误差分别为0.156 7、0.097 425、0.084 95,证明了该方法能够实时并准确的获取手指各关节力矩和耦合力矩,能够满足手部康复机器人交互控制准确性和实时性的需求。     

Brake torque analysis of fully mechanical parking brake system: Theoretical and experimental approach

The effect of the drum brake temperature reduction on the clamping force of the parking brake system has not been well addressed despite the fact that it may result in vehicle roll away. In view to this, a parking brake model that takes into account the temperature reduction of the drum brake has to be developed and more importantly, it must comply with the applicable standards or regulations such as Federal Motor Vehicle Safety Standard (FMVSS) 135. This paper develops a one dimensional (1D) model of leading-trailing drum-type parking brake model. This brake model is then verified with experiments carried out on a test bench that has been verified with the hand brake system in the vehicle. The results from the experiments show a good correlation with the predicted results from the brake model. It is also found that the existing parking brake design meets the standard requirements. Another finding is that the brake torque slightly increases as the drum temperature increases. With the verified brake model, parametric studies can be carried out as one of the tools during the design process. From the studies, it is found that rollaway will not happen even with the maximum vehicle weight and friction coefficient at drum/lining interface above 0.2.     

航空低温温度对自准直检焦系统的影响

为了研究航空低温温度对自准直检焦系统的影响,从而指导实际检焦系统的设计及修正,本文根据自准直检焦及几何光学原理,分析了单点成像、条纹成像及有无像散条件下,成像位置、成像宽度与接收的光强度差之间的相互关系,并给出了相关理论公式。结合实际的相机工况,对光学系统进行了相应的仿真,仿真结果显示,仿真双波峰电压值为1.4 V和0.47 V,与实际的检焦双波峰电压值1.38 V和0.56 V基本一致。根据结果进行了温控和柔性支撑,从而使检焦正常,提高了自准直检焦系统的温度适应性。本研究对系统的温度适应性具有指导作用。     

双头管封装光纤Bragg光栅低温传感试验研究

提出并设计了一种用于低温环境下测量温度的光纤布拉格光栅(FBG)双头管式封装结构,探究了涂覆层材料和封装形式对光纤Bragg光栅传感器低温传感稳定性和精度的影响。同时,试验研究了封装长度对双头管式传感器中心波长与温度的关系,通过多次重复试验测定了传感器低温灵敏度和重复性误差。研究结果表明：由于高折丙烯酸酯涂覆层具有较高的热膨胀系数,因此在77～273 K液氮环境中其增敏效果相对于聚酰亚胺和裸光纤更为显著;采用双头管封装后,FBG中心波长与温度具有高度线性关系,且能有效解决无封装裸FBG易受荷载扰动特性;适当提高封装长度有利于提高封装体系灵敏度系数。重复试验结果表明,所设计的双头管式封装FBG低温传感器灵敏度可达14～20 pm/K,测试误差和灵敏度优于传统FBG低温传感器。     

低温压力容器用钢及其焊接与检测

主要介绍低温压力容器制造用钢及其焊接特点和检测要求,其中对低温钢的焊接特点以及低温钢压力容器制造的特殊检验要求进行了重点介绍。     

磁流变减振器磁场特性分析及试验研究

设计了磁流变减振器磁芯磁路,建立了磁路的仿真模型,仿真研究了磁路的磁场特性,用实验的方法对仿真模型进行了验证和修正;在此基础上,建立了整个磁流变减振器的仿真模型,仿真研究了其磁场分布规律及不同参数下阻尼孔附近的磁通密度.研究结果表明,磁芯直径、工作缸壁厚、阻尼通道长度和线圈电流是影响磁场特性的主要因素,合理选择磁路结构参数可使其性能得到最大发挥.设计并制造出一种车辆单筒充气式磁流变减振器,对其进行了台架试验,得到不同电流下的减振器示功特性图,研究发现,通过调节减振器励磁线圈中的电流获得不同强度的磁场,在磁场作用下,磁流变液粘度发生变化,从而改变减振器的阻尼特性,减振器的饱和工作电流约为2A.试验验证了磁路设计的正确性,并为实现车辆磁流变半主动空气悬架控制研究奠定了基础.