带扰动观测器的永磁同步电机非线性预测跟踪控制

针对永磁同步电机系统转速跟踪控制问题,基于非线性预测控制方法设计控制系统,使该系统满足高性能控制要求。并将负载转矩作为未知扰动来考虑,利用扰动观测器得到其估计值,从而提高系统鲁棒性。仿真实验结果表明,本文方法能够快速准确地实现转速跟踪,并提高系统对负载转矩扰动的鲁棒性。     

超高强度钢滚道的精密成形磨削工艺

介绍一种超高强度齿圈的滚道精密成形磨削的工艺。该工艺通过改进测量方法,减小零件滚道的测量误差,通过细化工艺流程、制定关键作业说明书,控制加工过程的误差,提升滚道的质量,实现了批量生产时内外滚道的互换性。     

ELID沟道成形磨削氧化膜特性及影响作用实验

针对ELID沟道成形磨削特点,研究了磨削过程中氧化膜的特性及其影响作用。探讨分析了氧化膜的电流表征、氧化膜在沟道成形磨削中的状态变化以及氧化膜状态对磨削力和表面粗糙度的影响。实验过程中,电解电流从1 A增长到4 A,氧化膜厚度从35.33!m减小到11.07!m,法向磨削力从7.06 N增长到36.12 N,切向磨削力从1.62 N增长到4.47 N;垂直于磨削方向的表面粗糙度由0.256!m增长到0.355!m,平行于磨削方向的表面粗糙度由8 nm增长到13 nm。结果表明,氧化膜越厚,磨削力和表面粗糙度越小;氧化膜越薄,磨削力和表面粗糙度越大。     

螺旋波等离子体推进器磁场仿真

推进工质电离、加速、喷出过程以及电羽流的污染控制等都与磁场密切相关。磁场位形的仿真设计对于提高螺旋波等离子体推进器的性能至关重要。基于等效磁荷方法建立了专门针对螺旋波等离子体推进器的三维磁场仿真模型, 计算出圆柱形与圆环形铷铁硼(Nd-Fe-B)永磁体组合产生的磁场位形及磁场强度分布特征。该模型为改进电推进器实验方案提供必要的参考和指导;通过大量仿真计算与分析, 从大量的磁铁构型方案中优选出合适的磁铁构型, 可以缩短螺旋波等离子体推进器的实验周期, 降低成本, 加快电推进器的研发进度。     

一维钡铁氧体纳米线的制备及操控

采用Sol-gel法,以自制的AAO模板制备了直径40～60nm,长度为150～200nm的一维BaFe12O19纳米线.利用X射线衍射(XRD),场发射扫描电镜(FESEM),振动样品磁强计(VSM)对BaFe12O19纳米线的组成、形貌与磁性能进行了研究.在外磁场的驱动下,对一维BaFe12O19纳米线进行操控.研究发现:BaFe12O19纳米线的易磁化方向平行其轴线方向,且操控后,BaFe12O19纳米线定向连接成“链”,当磁场与BaFe12O19纳米链阵列平行(∥)时,纳米链的剩余磁化强度(Mr)、饱和磁化强度(Ms)和最大磁能积(BH)m都得到增强.矫顽力(He)由3.98×105A/m增大至5.01×105 A/m,矩形比为0.9,可成为优异的高密度垂直磁记录材料.     

基于AVR32的小型磁航向系统设计

现有的磁航向测量系统体积、重量、功耗偏大,并且调试、误差补偿算法复杂、整体费用偏高,针对这些问题,设计了一个在小角度俯仰、滚转情况下的小型磁航向测量系统.该系统采用带DSP指令的32位高速处理芯片AVR32 UC3B0256、新型倾角传感器SCA100T以及磁阻传感器HMC 1022构成数字化解算平台,实现了误差补偿.实验数据显示,在水平状态下,磁航向测量值最大误差为±1.4;当俯仰角低于30°或滚转角低于35°时,随着角度的增加,磁航向输出误差变化不大,最大误差分别为3.7°和2.8°;当俯仰角超过30°或滚转角超过35°时,磁航向输出误差会急速增大.结果表明,该系统在小角度俯仰、滚转情况下具有较准确的磁航向角解算能力.     

Multi-scale reconnections in a complex CME

A series of three flares of GOES class M, M and C, and a CME were observed on 20 January 2004 occurring in close succession in NOAA 10540. Types II, III, and N radio bursts were associated. We use the combined observations from TRACE, EIT, Hα images from Kwasan Observatory, MDI magnetograms, GOES, and radio observations from Culgoora and Wind/ WAVES to understand the complex development of this event. We reach three main conclusions. First, we link the first two impulsive flares to tether-cutting reconnections and the launch of the CME. This complex observation shows that impulsive quadrupolar flares can be eruptive. Second, we relate the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. Finally, we show that reconnection with the magnetic structure of a previous CME launched about 8 h earlier injects electrons into open field lines having a local dip and apex (located at about six solar radii height). This is observed as an N-burst at decametre radio wavelengths. The dipped shape of these field lines is due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains why this is the first N-burst ever observed at long radio wavelengths.     

ULF wave index as magnetospheric and space-weather parameters

Waves in the Ultra Low Frequency (ULF) band owe their existence to solar wind turbulence and transport momentum and energy from the solar wind to the magnetosphere and farther down. Therefore an index based on ULF wave power could better characterize solar wind–magnetosphere interaction than K_P, Dst, AE, etc. indices which described mainly quasi-study state condition of the system. We have shown that the ULF wave index accurately characterize relativistic electron dynamics in the magnetosphere as these waves are closely associated with circulation, diffusion and energization of relativistic electrons in the magnetosphere. High speed solar wind streams also act as a significant driver of activity in the Earth’s magnetosphere co-rotating interaction region and are responsible for geomagnetic activities. In the present paper, we have analyzed various cases related with very weak (quiet) days, weak days, storm days and eclipse events and discussed the utility of the ULF wave index to explain the magnetospheric dynamics and associated properties. We have tried to explain that the ULF wave index can equally be useful as a space weather parameter like the other indices.     

基于磁路法与等效热网络法的航天 永磁同步电机设计与仿真

针对航天永磁同步电机方案初步设计耗时长、过度依赖商业软件的问题，基于磁路法和热网络法，提出了一套方案设计阶段航天永磁同步电机磁热性能快速预估与仿真方法。给出了定子内径、定子外径、铁芯长度、匝数等关键参数的取值准则，建立了包含36个节点集总参数热网络模型，并以端部绕组为例给出了热平衡方程的详细推导过程。通过与成熟商业软件对比，其电磁计算最大误差出现在电流有效值上，偏差值为607%；与样机实测值对比，绕组温升最大误差为73%，满足方案设计阶段预示精度要求，为方案设计阶段航天永磁同步电机快速性能预估提供有力支撑。     

多个空间高斯源信号情况下成组三维图像特征提取方法

针对功能磁共振成像数据中含有多个高斯信号源的盲源分离问题,介绍了一种成组典型相关分析方法(Group BSS-CCA)。这个方法的组分析框架参照了GIFT工具箱中的Group ICA算法,具体的典型相关分析方法应用的是Friman等人提出的BSS-CCA算法。以验证该方法的有效性为目的,设计了仿真实验;结果表明,该方法能较好识别出混合在人脑功能磁共振成像数据的2个空间高斯信号。Group BSS-CCA算法对研究人脑的功能磁共振成像数据具有较高的实用价值。