微型超声波电机定子振动特性有限元分析

利用有限元法对齿状环形行波型微超声波电机定子的振动特性进行了计算分析.建立了定子弹性体和压电体耦合的有限元模型,利用SOLID45单元将定子编制成ANSYS有限元软件的宏文件,以便于改变定子尺寸并自动生成相应的有限元模型;探讨了不同结构参数对压电定子动态性能的影响,得到了各结构参数对压电定子模态频率的影响曲线.研究结果表明,定子弹性体与压电体之间的胶粘层对定子模态频率的影响很小,在分析过程中可以忽略;定子的振动主要以弯曲模态为主,其振动频率随压电陶瓷和定子环厚度的增加而增大,随定子齿高、齿数和内径的增加而减小.     

浅析三相异步电动机“定子振动”产生原因及处理方法

主要讲述了引起电动机所谓＂定子振动＂的主要原因,并运用有限元软件进行计算分析,最终找出解决＂定子振动＂的处理方法.     

具有直流母线特征的电动机系统能量回收统一方法研究

详细分析了具有直流母线特征的电动机系统再生电能的回收原理,通过对直流电动机和交流电动机能量回收过程的综合比较分析,形成了对具有直流母线特征的电动机系统行之有效的能量回收统一方法,并对该方法进行了仿真和实验研究,验证了该方法的合理性和可行性.     

基于能量回收的土木工程结构振动控制

为了解决土木工程结构振动的主动和半主动控制技术对外界电源过分依赖的问题,系统回顾了基于能量回收与利用的各种结构振动控制系统。在此基础上,提出了一种自供电磁流变阻尼器减振系统,实现了振动控制的自供电与传感;指出了该系统的应用前景、亟待解决的问题和进一步的研究方向。研究结果表明：该系统既可以作为具有自适应特征的被动控制装置,也可以设计为半主动控制系统,同时该系统还可以和其他结构控制系统组合使用。     

发电机定子铁芯模态振动特性试验研究

对发电机定子铁芯进行模态振动试验是为了防止汽轮发电机组在运行过程中定子铁芯椭圆形模态振动频率与双倍的发电机的径向电磁力频率产生共振。目前只有各个发电机制造厂进行数值模拟和出厂前进行模态振动测试,几乎没有在电厂生产现场进行该项测试。文章通过几个典型汽轮发电机测试实例详细介绍了对于电厂停机检修机组进行发电机定子铁芯模态试验的方法及特性,提出了现场试验过程中的要点。指出发电机铁芯模态振动测试是目前发电机安全监测工作中很好的补充技术手段。     

振动偏心时定子绕组短路对振动特性影响分析

考虑了实际运行的发电机普遍存在的振动偏心状态,对定子匝间短路引起的发电机振动特性进行了机电耦联交叉特性分析。首先分析定子绕组匝间短路后气隙磁场变化特征,计算得到气隙磁导、气隙磁密和气隙磁场能的表达式,然后得到作用于转子的不平衡电磁力特性和作用于定子的脉振电磁力特性,最终得到定转子径向振动特征。并实际测试了SDF-9型和MJF-30-6型故障模拟发电机定子绕组匝间短路时定转子径向振动信号,与理论分析结果基本吻合。     

直流无刷电机定子总成振动特性分析

以世博电动小车驱动电机为研究对象,在有限元分析软件ANSYS中建立了电机定子总成的有限元模型,通过试验进行了模型验证.并使用ANSYS对定子进行了模态分析,获得定子的模态振型和模态频率.进一步研究了定子总成中各组件对定子振动特性的影响,详细对比分析了加入不同组件后定子模态振型和频率的变化情况.此项工作有助于电机的进一步...     

两自由度压电式轨道振动能量采集器

提出一种轨道板垂向振动能量采集方法,设计3种不同方案的两自由度压电式轨道振动能量采集器,并建立其运动方程和机电耦合方程.通过运用谐波平衡法,在简谐激励下分析得到压电式轨道振动能量采集器的输出电压和输出功率的幅频响应,通过直接的数值模拟验证了分析结果的正确性,得到两自由度轨道压电式振动能量采集器的最优方案.该方案采集器的能量采集效果远高于其他两种方案.通过调节刚度参数,可以有目的地增强两个共振峰中的任意一个,从而达到与轨道振动激励谐振的目的.     

笼型感应电动机定子故障诊断分析

介绍了笼型感应电动机定子故障的类型,分析了产生故障的可能原因,阐述了热应力、电应力、机械应力、环境应力等对电机绝缘系统的影响及故障的表现状态,提出了相应的解决措施和办法,有助于电动机的维护和剩余寿命的推算.     

不同截面形状柱体流激振动能量转换特性分析

为了比较不同截面形状柱体的流激振动特性,探讨适用于流激振动能量转换的柱体截面形式,本文基于雷诺平均N-S方程,结合SST k-ω湍流模型和任意拉格朗日欧拉流固耦合动网格控制方法,对高雷诺数、高阻尼比条件下,圆柱、方柱、类梯形柱、梯形柱及T字形柱等5种不同截面形状的柱体流激振动进行数值模拟,模拟中保持各柱体的特征长度相同,质量比、阻尼比、同一流速下的雷诺数和约化速度等重要无量纲参数也均保持一致。计算结果表明:圆柱的振动表现为典型的涡激振动,其他4种柱体的振动均为驰振,在较低约化流速下T字形柱获得的功率均较其他柱体获得的为大。各柱体能量转换效率均随约化速度的增加先增大后减小,中间存在一个峰值,5种柱体中T字形柱的最大能量转换效率为最大,达到了42. 5%,其次为圆柱,为27%。为了达到最大能量转换效率,圆柱和方柱所需要的流速最小,其次为T字形柱。从分析结果来看,T字形柱和圆柱对于低流速下的能量转换较为有利。     

A new visco-elastic contact model of traveling wave ultrasonic motor with stator frictional layer

A new contact model of traveling wave ultrasonic motor (TWUSM) with a visco-elastic stator frictional layer was presented. In this model, the initial boundaries were revised, and the rotor revolution speed could be calculated iteratively. This model was compared with compliant slider and rigid stator model. The results of motor characteristics simulations showed that the motors based on this model would gain bigger stall torque. Then the friction and wear characteristics of two models were analyzed. The motors based on this model had lower coefficient of friction and better wear resistance.     

一种新型超声马达--复合型超声马达

从复合型超声马达的结构形式入手，分析了复合型超声马达的工作原理，研究了压电振子的微观振动与超声马达宏观运动之间的关系，阐述了扭转振子的速度波形特性，提出了理想的驱动波形。     

Ferroelectric materials for vibrational energy harvesting

Energy harvesting is an appealing technology that makes use of the ambient energy which is otherwise wasted. Piezoelectric materials directly convert the elastic energy to the electric energy, and thus have a great advantage in scavenging vibrational energy for simplicity in device structure with relatively high power density. This paper provides an overview on the research of piezoelectric materials in energy harvesting in recent decades, from basics of piezoelectricity and working principle of energy harvesting with piezoelectric materials, to the progress of development of high-performance piezoelectrics including ceramics, single crystals and polymers, then to experimental attempts on the device fabrication and optimization, finally to perspective applications of piezoelectric energy harvesting (PEH). The criteria for selection of materials for PEH applications are introduced. Not only the figure of merit but also maximum allowable stress of materials are taken into account in the evaluation of their potential in achieving high energy density and output power density. The influence of the device configuration on the performance is also acknowledged and discussed. The magnitude and distribution of induced stress in the piezoelectric unit upon excitation by the vibration source play an important role in determining the output power density and can be tuned via proper design of device configuration without changing its resonant frequency. Approaches to address the issue of frequency match accompanying with the resonant mode are illustrated with literature examples. Usage of PEH devices can be extended to a variety of vibration sources in everyday life as well as in nature. Some appealing applications of PEH, such as in implantable and wearable devices, are reviewed.     

大型汽轮发电机定子绕组端部的振动分析

为了研究大型汽轮发电机定子绕组端部振动可靠性,需要有效地分析和识别大型汽轮发电机定子绕组端部的椭圆模态,并根据此模态调整相应结构,提高结构稳定性.利用定子绕组的循环对称特性,推导出多重循环结构的摄动法.根据实际中影响循环对称特性的非循环部件或者约束,选取适当的步长,加入非循环对称部分,对原循环结构逐步摄动求解,最后将摄动法求解的结果与试验结果进行比较.结果表明,将非循环部分加入到循环结构后,使用摄动法分步求解,不仅能判断摄动过程中的椭圆模态变化,还能识别并确定感兴趣的椭圆模态.定子端部其他模态亦可用此法确定.     

Driving characteristics of octagon-type ultrasonic motor

Structure of the octagon-type ultrasonic motor was proposed and designed so as to allow the motor to drive small actuator. The stator of the motor consisted of the octagon shape elastic body and four rectangular plate ceramics. The four ceramics were attached to outer surfaces of the octagon elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90° phase difference voltages were applied to the ceramics on vertical surfaces. When the AC voltage with 90° phase difference was applied in ceramics, the elliptical displacement of unimorph bars was generated by generating bending vibration. To find the maximum displacement model that generates elliptical displacement at the centers of the inner surfaces, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As a result, the speed and torque are increased linearly by increasing the input voltage and the speed of motors can be controlled by changing the applied voltages.     

Optimal design of V-type ultrasonic motor

V-type ultrasonic linear motor fabricated using a simple punching technique was proposed to utilize as an actuator of small precision machine. The stator of the motor is composed of a thin elastic body and four ceramics attached to the upper and bottom areas of the body. The ceramics have each direction of polarization. When two harmonic voltages with a 90° phase difference are applied to the ceramics, symmetric and anti-symmetric displacements will generate at the tip to produce an elliptical motion. A finite element analysis (ATILA) was conducted to simulate the motion pattern for the contact tip of the stator. To develop a model that generates the maximum displacement at contact tip, the FEM program was used for various lengths. In addition, an optimal model was chosen by considering the magnitude and shape of the displacement according to changes in frequency. The maximum elliptical displacement is shown by W2L11 model, which has a ratio of ceramic width to length of 1:5.5. However, the displacement of the contact tip is reduced by the bucking phenomenon if the ratio is larger than 1:6.     

异步电动机定子绕组匝间短路故障特征分析

基于多回路数学模型,对异步电动机定子绕组匝间短路故障瞬变过程做了数字仿真,并完成了相关物理实验。在此基础上,对定子绕组匝间短路故障的典型特征进行灵敏度与可靠性评定,遴选出定子负序视在阻抗低通滤波值这一可靠兼具良好灵敏度的定子绕组匝间短路故障特征,从而为定子绕组匝间短路故障的灵敏、可靠检测奠定了基础。     

Energy harvesting via nonlinear energy sink for whole-spacecraft

This paper presents nonlinear energy sink with giant magnetostrictive-piezoelectric material for energy harvesting of the wholespacecraft vibration reduction system. The whole-spacecraft vibration attenuation system can effectively reduce vibration and achieve self-tuning enhanced energy harvesting range. The open-circuit voltage generated at low frequency is affected by the magnetic field force, alternating magnetic field and relative displacement. In order to acquire a steady periodic solution of the energy harvesting system, a combination of the harmonic balance method and pseudo arc length continuation technique is used.The numerical outcomes are consistent with the analytical outcomes in a certain range, which also proves the accuracy and reliability of the results. The amplitude and voltage of the energy harvesting system are analyzed by parameters such as cubic stiffness, viscous damping, and external excitation acceleration. In addition, this paper provides a new idea for broadband energy harvesting.