新型交替极永磁游标电机的优化设计与分析

为解决适用于低速场合的永磁游标电机永磁体极数多的问题,通过提高电机的输出性能,提出一种新型交替极永磁游标电机拓扑。通过有限元法对比4种不同的励磁永磁体配置,研究Halbach阵列增强交替极电机输出性能的方式;针对齿槽转矩与输出转矩,对电机的结构参数进行优化设计;最后,分析该电机的电磁性能、气隙磁密和谐波分布。仿真结果表明:与传统交替极电机相比,该新型交替极永磁游标电机在反电势、气隙磁密、齿槽转矩、输出转矩和电机效率上有较好的性能,适用于低速大转矩的应用场合。     

Halbach永磁阵列型轴向调制永磁齿轮

本文提出了一种可输出高转矩的轴向调制永磁齿轮。在不改变轴向调制永磁齿轮整体尺寸的情况下,将主、从动磁极按照Halbach永磁阵列进行排列,利用Halbach永磁阵列的聚磁作用,增大主、从动侧气隙内耦合磁场的磁场强度,并使用有限元法对这种永磁齿轮进行了仿真分析。结果表明Halbach永磁齿轮比传统阵列永磁齿轮的输出转矩更大;对气隙磁通量密度的谐波分析表明,Halbach永磁齿轮和传统阵列永磁齿轮的气隙磁密谐波变化趋势一致,因此传动机理不变;对Halbach永磁齿轮的磁极的扇形角度进行优化处理后,可以进一步增大输出转矩。     

轮毂式永磁无刷直流电机空载气隙磁密波形的模拟分析

针对轮毂式永磁无刷直流电机空载气隙谐波含有大量的谐波问题,采用有限元法设计轮毂式永磁无刷直流电机,对影响其性能的空载气隙磁密波形进行了数值模拟,降低了谐波损耗,提高了轮毂电机的性能.通过正交试验法改变定子齿槽宽度、气隙大小和磁极厚度,减少了气隙磁密谐波的含量,并通过绘制因素水平影响趋势图,分析了各个因素对于电机空载气隙...     

磁场调制式永磁齿轮Halbach充磁与平行充磁分析比较

为了提高磁场调制式永磁齿轮(Field Modulated Permanent Magnetic Gears,FMPMG)的气隙磁密及传动转矩,基于某一具体结构的FMPMG,应用Ansoft14对其Halbach及平行充磁方式进行了分析比较,研究了永磁体厚度、转角差、轭铁厚度对气隙磁密及传动转矩的影响,结果表明:Halbach所形成的气隙磁密较平行充磁更具有正弦性;与平行充磁相比,Halbach气隙磁密的厚度极值点明显高于平行充磁;另外,Halbach特有的单边效应,使其对轭铁厚度的要求不高,可减小或取消轭铁结构以降低FMPMG的转动惯量,为大功率高性能的FMPMG实用化奠定基础。     

磁钢充磁方式对高速永磁电机性能的影响研究

针对高速永磁电机的充磁方式问题,对一台250 k W,67 000 r/min高速永磁电机的径向充磁、平行充磁和Halbach充磁3种永磁体充磁方式进行了研究,对不同充磁方式给高速永磁电机气隙磁场、齿槽转矩、损耗的影响进行了分析。利用有限元分析的方法,根据实际的充磁方式,在有限元软件中建立了高速永磁电机模型,对高速永磁电机不同充磁方式下的性能进行了研究,对比分析了平行充磁、径向充磁及Halbach充磁这3种充磁方式对高速永磁电机气隙磁场、齿槽转矩、定子空载铁耗、转子涡流损耗、额定运行时总损耗等的影响,并且总结了高速永磁电机理想的充磁方式。研究结果表明:采用平行充磁方式时高速永磁电机的气隙磁密波形更趋于正弦、齿槽转矩更小,电机的总损耗最小,运行性能更优。     

一种提高磁齿轮转矩新方法

相比机械齿轮接触式传动,磁齿轮是一种结构新颖、具有广阔发展前景的新型传动装置,它利用磁场调制原理实现大转矩传递。在传统磁齿轮结构基础上对内、外转子永磁体进行改进,内永磁体为三角形-扇形相间,内外永磁体均为Halbach阵列。运用二维有限元法对改进型磁齿轮模型进行仿真,并计算磁齿轮电磁场和电磁转矩,同时与传统磁齿轮磁场和转矩进行比较。仿真结果表明,改进型磁齿轮能有效增强气隙磁密幅值,减小气隙谐波含量,同时输出转矩较传统磁齿轮提高。这对同心式磁力齿轮转矩密度的提高研究及应用具有重要意义。     

磁场调制式永磁齿轮气隙磁密数理模型建立及其运行机理分析

针对磁场调制式永磁齿轮(FMPMG)的气隙磁密理论推导不完善,无法深刻揭示出FMPMG内在运行机理等问题,基于永磁电机气隙磁密及其单边有槽气隙磁导的计算方法,对FMPMG气隙磁场进行了理论分析与系统建模;认为调磁环对内、外转子所产生的调制作用是FMPMG正确运行的基础,其对一个永磁体转子所产生的调制谐波必须与另一个永磁转子的基波相匹配,才能使FMPMG按一定的传动比输出转速与转矩,且调磁环的调制作用取决于永磁体的磁极对数:磁极对数越多,其调制作用越明显;反之,则并不明显。     

无刷直流电机的设计及优化

首先,详细研究了提高电机性能的关键性因素,针对无刷直流电机高功率密度设计要求,结合电机学设计理论,通过分析计算,确定电机的极槽配合、永磁体材料及尺寸、定子绕组、定子槽型、定子铁芯结构,完成无刷直流电机的本体电磁设计;然后,通过Ansoft Maxwell仿真软件,构建二维场—路耦合模型,通过有限元方法分析计算电机的稳态场和瞬态场,重点分析了电机的磁力线分布、磁通密度分布和齿槽转矩;最后,针对裂比、长径比、极弧系数、槽口宽度、气隙长度进行优化设计,合理设置参数变量,以齿槽转矩及气隙磁密谐波为优化目标,通过优化尽可能减小齿槽转矩,抑制谐波,最终得到优化设计方案。     

表贴式与内置式无轴承永磁同步电动机电磁特性对比

为探究不同转子结构对无轴承永磁同步电动机电磁特性的影响,对2台表贴式与内置式无轴承永磁同步电动机进行对比分析。2台无轴承永磁同步电动机的定子结构、绕组通入的电流、相位、永磁体产生的气隙磁密完全相同。建立了2台电动机的有限元模型,对比分析了永磁磁链、反电动势、电感、转矩以及悬浮力等静态电磁特性。有限元仿真结果表明:表贴式永磁同步电动机永磁体的用量较小,磁链谐波分量较少;内置式无轴承永磁电动机能够产生较大的电感、转矩与悬浮力。     

内置式永磁同步电机气隙磁密与漏磁解析计算

为了分析转子具有隔磁桥的内置式永磁同步电机的空载气隙磁场,基于改进等效磁网络法进行了气隙磁密与漏磁解析计算。考虑到隔磁桥造成的磁路变化,分别计算了相邻两永磁体磁路等效磁阻、永磁体端部磁路等效磁阻、永磁体自身磁阻与主磁通和漏磁通。针对原有气隙磁阻引入了卡特系数,计算了定子开槽影响的等效气隙长度,进而计算出一个定子齿下的相对气隙磁导函数。用改进等效磁网络法分析了电机空载作用下的气隙磁场,并与有限元法计算结果进行了对比,验证了改进等效磁网络算法的准确性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.