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51.
针对直线电机转子位置检测低成本和较高精度的要求,提出了一种基于马鞍形磁场来获得位置信息的方法及实现过程。分析了永磁体表面的磁场分布特征,指出了利用马鞍形磁场分布曲线来解算位置信息的优点,提出了根据马鞍形磁场推算位置信息的算法流程:先测得错开相位的2条马鞍形曲线数据,划分为4个象限后建立数据库;位置检测时,运用区间搜索算法寻得实际角度所在区间;再根据精度要求,采用合适的插值算法计算得到待解算的角度。仿真结果表明:基于马鞍形磁场的位置解算,能较好地得到直线电机转子的位置信息。 相似文献
52.
53.
A. G. Yahnin I. V. Despirak A. A. Lubchich B. V. Kozelov N. P. Dmitrieva M. A. Shukhtina H. K Biernat 《Space Science Reviews》2006,122(1-4):97-106
Although the auroral substorm has been long regarded as a manifestation of the magnetospheric substorm, a direct relation
of active auroras to certain magnetospheric processes is still debatable. To investigate the relationship, we combine the
data of the UV imager onboard the Polar satellite with plasma and magnetic field measurements by the Geotail spacecraft. The
poleward edge of the auroral bulge, as determined from the images obtained at the LHBL passband, is found to be conjugated
with the region where the oppositely directed fast plasma flows observed in the near-Earth plasma sheet during substorms are
generated. We conclude that the auroras forming the bulge are due to the near-Earth reconnection process. This implies that
the magnetic flux through the auroral bulge is equal to the flux dissipated in the magnetotail during the substorm. Comparison
of the magnetic flux through the auroral bulge with the magnetic flux accumulated in the tail lobe during the growth phase
shows that these parameters have the comparable values. This is a clear evidence of the loading–unloading scheme of substorm
development. It is shown that the area of the auroral bulge developing during substorm is proportional to the total (magnetic
plus plasma) pressure decrease in the magnetotail. These findings stress the importance of auroral bulge observations for
monitoring of substorm intensity in terms of the magnetic flux and energy dissipation. 相似文献
54.
Coronal mass ejections and post-shock streams driven by them are the most efficient drivers of strong magnetospheric activity,
magnetic storms. For this reason there is considerable interest in trying to make reliable forecasts for the effects of CMEs
as much in advance as possible. To succeed this requires understanding of all aspects related to CMEs, starting from their
emergence on the Sun to their propagation to the vicinity of the Earth and to effects within the magnetosphere. In this article
we discuss some recent results on the geoeffectivity of different types of CME/shock structures. A particularly intriguing
observation is that smoothly rotating magnetic fields within CMEs are most efficient in driving storm activity seen in the
inner magnetosphere due to enhanced ring current, whereas the sheath regions between the shock and the ejecta tend to favour
high-latitude activity. 相似文献
55.
文章在介绍某型电压限定器工作原理的基础上,阐述了利用集成电路技术和自动控制技术进行该型电压限定器国产化研制的方法,给出了电压限定器探测及延时电路、均衡控制电路、防止误动作保护电路的详细设计方案,解决了激磁控制、均衡控制、故障鉴别等国产化研制过程中遇到的问题,保证了新研制产品与原有进口产品的可互换使用,提高了设备的工作可靠性。 相似文献
56.
57.
J. Wicht M. Mandea F. Takahashi U. R. Christensen M. Matsushima B. Langlais 《Space Science Reviews》2007,132(2-4):261-290
Mariner 10 measurements proved the existence of a large-scale internal magnetic field on Mercury. The observed field amplitude,
however, is too weak to be compatible with typical convective planetary dynamos. The Lorentz force based on an extrapolation
of Mariner 10 data to the dynamo region is 10−4 times smaller than the Coriolis force. This is at odds with the idea that planetary dynamos are thought to work in the so-called
magnetostrophic regime, where Coriolis force and Lorentz force should be of comparable magnitude. Recent convective dynamo
simulations reviewed here seem to resolve this caveat. We show that the available convective power indeed suffices to drive
a magnetostrophic dynamo even when the heat flow though Mercury’s core–mantle boundary is subadiabatic, as suggested by thermal
evolution models. Two possible causes are analyzed that could explain why the observations do not reflect a stronger internal
field. First, toroidal magnetic fields can be strong but are confined to the conductive core, and second, the observations
do not resolve potentially strong small-scale contributions. We review different dynamo simulations that promote either or
both effects by (1) strongly driving convection, (2) assuming a particularly small inner core, or (3) assuming a very large
inner core. These models still fall somewhat short of explaining the low amplitude of Mariner 10 observations, but the incorporation
of an additional effect helps to reach this goal: The subadiabatic heat flow through Mercury’s core–mantle boundary may cause
the outer part of the core to be stably stratified, which would largely exclude convective motions in this region. The magnetic
field, which is small scale, strong, and very time dependent in the lower convective part of the core, must diffuse through
the stagnant layer. Here, the electromagnetic skin effect filters out the more rapidly varying high-order contributions and
mainly leaves behind the weaker and slower varying dipole and quadrupole components (Christensen in Nature 444:1056–1058,
2006). Messenger and BepiColombo data will allow us to discriminate between the various models in terms of the magnetic fields
spatial structure, its degree of axisymmetry, and its secular variation. 相似文献
58.
永磁行星齿轮和同轴永磁齿轮是两类具有不同拓扑结构和运行原理的磁力齿轮,采用定量设计比较法设计了具有相同有效体积和永磁体用量的上述两类磁齿轮,并通过有限元分析法对二者的转矩传递性能进行比较研究。研究结果表明,永磁行星齿轮较同轴永磁齿轮有更高的转矩密度和更低的转矩脉动。此外,由于永磁行星齿轮具有更加灵活的运行模式,并且能实现功率分流,使其在混合动力汽车领域有很好的应用前景。加工了一台永磁行星齿轮样机,并搭建试验平台进行了相关的试验,结果表明了该拓扑结构的有效性。 相似文献
59.
在模块化永磁直线游标电机的初始设计及优化设计中,使用有限元方法(FEM)计算漏磁系数时需要耗费大量的建模和计算时间。针对这一问题,建立该种电机的等效磁网络模型,在建模期间,考虑气隙中的边缘效应,并计算永磁体组与定子齿在不同相对位置时的等效磁导,得到该种电机在一个周期内不同相对位置时的漏磁磁导和漏磁系数的数学解析表达式。采用FEM验证了该数学解析表达式的准确性。研究结果为模块化永磁直线游标电机的设计提供了理论依据。 相似文献
60.
高负荷压气机叶栅分离结构及其等离子体流动控制 总被引:8,自引:0,他引:8
为揭示高负荷压气机叶栅内部流动损失的产生机理和分布规律以及等离子体气动激励的作用机制,利用拓扑分析和数值计算方法,从计算模型的建立与验证、基准流场的分离结构和等离子体流动控制3个方面展开研究;对总压损失系数分布、拓扑结构和表面流谱与空间流线分布以及旋涡结构进行分析,并开展了激励方式的优化分析.结果表明:随着攻角的增大,固壁面拓扑结构增加了3对奇点,吸力面流向激励改变了固壁面拓扑结构.当攻角为2°时,在吸力面拓扑结构中产生了一对奇点,打断了角区分离线,并引入了一条回流再附线.叶栅流道内部有5个主要涡系,尾缘径向对涡促进流体的展向流动,并成为吸力面倒流的主要组成部分;角涡是一个独立的涡系,其强度和尺度不受等离子体气动激励的影响.吸力面流向激励可以改善叶中流场,但对角区流动作用很小;端壁横向激励可以降低角区流动损失,对叶中流场作用有限;吸力面流向与端壁横向组合激励在整个叶高范围内均可以显著抑制流动分离;端壁横向流动对角区流动分离结构的影响大于吸力面附面层的分离.吸力面流向激励的优化明显降低,而端壁横向激励和组合激励的优化保持并增强了等离子体流动的控制效果. 相似文献