大力矩径向驻波型超声波电机有限元分析与实验研究

提出了一种大力矩径向驻波型超声波电机,在实现电机大力矩输出的同时保持结构紧凑的特点。首先设计并分析了电机的结构和工作原理,采用有限元法分析了电机定子的振动特性。接着制作了超声波电机样机,样机直径为32 mm。采用激光测振仪测量了定子的共振频率及径向振动的振幅,测量结果与理论分析结果相吻合。最后,搭建了电机输出特性测试平台,测量了电机在不同电压下的转矩-转速特性。实验测试结果显示,定子工作模态的共振频率为73.3 kHz,当施加的电压幅值为100 V、频率为74 kHz时,电机的空载转速为45 r/min,堵转力矩达到0.41 N·m。与其他同尺寸的超声波电机相比,所提出的径向驻波型超声波电机具有更大的堵转力矩。     

基于中心差分扩展卡尔曼滤波算法的三相感应电机转速和转矩的估计

针对三相感应电机在转速和转矩测试过程中,存在采集数据易受外界干扰而导致转速和转矩等估计值出现较大偏差的问题,提出采用中心差心扩展卡尔曼滤波算法实现对三相感应电机转速和转矩的估计.首先,以三相感应电机的定子和转子电流作为状态变量,推导出了三相感应电机在α-β坐标系下的状态方程和输出方程.然后,采用中心差分扩展卡尔曼滤波算法实现对三相感应电机转速和转矩的解算.仿真结果表明,与扩展卡尔曼滤波算法相比,中心差分扩展卡尔曼滤波算法对电机运行状态的变化具有更好的跟随性能及更快的收敛速度,能够准确的估计三相感应电机的转速和转矩.     

二自由度行波型超声波电机定子的数学模型与实验研究

二自由度行波型超声波电机是一种新型多自由度超声波电机。本文从二自由度行波型超声波电机的驱动机理和基本结构出发,就电机的结构实现、驱动球转子的最佳定子结构进行了分析,利用所建立的有限元模型进行定子振动的模态分析和共振频率计算,提出了外缘大倾角内缘线接触的行波定子。然后建立定子的接触模型,对其机械性能进行分析。测试结果表明,修正的数学模型更加符合电机的实际运行特性。所研制样机的球转子直径为45mm,定子直径为30mm,实现的堵转力矩为120mNm,空转转速12r/min。本文工作为多自由度行波型超声波电机的优化设计、性能提高奠定了基础。     

永磁同步伺服电机转矩转速性能参数测试系统

介绍了基于运动控制器的数据采集和分析的伺服电机转矩转速测试平台,并在VC平台上开发了该平台的运动控制命令程序。以该测试系统测试了伺服电机的转矩转速参数,并通过转矩、转速分析了电机启动、运行等特性,以此分析了伺服电机的整体特性。通过实验证明该系统能够准确地测量电机参数,并能对数据进行分析以及通过对电机的分析验证试验系统的可靠性。     

电动车驱动用永磁同步电机力矩特性的研究

对影响内置式永磁同步电机转矩特性的三个关键设计参数——永磁体宽度、定子绕组匝数及转子铁心外形进行了研究。以具体样机为例,分析了定子绕组匝数、永磁体充磁方向长度和转子外形对转矩特性的影响。分析结果表明：永磁体宽度接近于整数倍定子齿距可降低负载脉动转矩;采用偏心分段圆弧法优化转子外形有利于提高电机的转矩特性。通过实验验证了理论分析的正确性。     

一种用于光学模组变焦的新型螺纹压电电机

基于课题组早期研究的转速可达10000r/min,响应时间小于1ms的棒板结合式压电电机的启发,设计并制备了一种扩展结构的用于光学模组变焦的螺纹压电驱动器,它同时具备响应时间短的特点.本压电驱动器采用筒板结合式的定子结构,在B11工作模态下通过定子圆筒内螺纹将运动传递给转子,单层压电陶瓷粘贴在定子板上驱动电机运转.本研究利用有限元法分析了电机定子的工作模态和谐响应,利用红外多普勒激光测振仪测量了电机在不同频率下定子的微观振动,实验验证了理论预测并证明了这种结构简单紧密的压电驱动器的可行性.电机运行实验验证了该电机具有响应时间短、电机转速合适、定位精确等优点,适合用于光学调焦领域.     

永磁同步电主轴电机有限元分析和参数优化

根据经典的麦克斯韦瞬态电磁场分析理论,利用Ansoft有限元软件对永磁同步电主轴电机进行实时工况仿真和瞬态磁场分析,定量研究永磁电机定子槽口宽度和永磁体偏心距对齿槽转矩及力能特性的影响规律。根据齿槽转矩产生机理,提出优化电机结构参数抑制齿槽转矩的策略。仿真实验结果表明,根据所提策略优化后的主轴电机参数可明显削弱齿槽转矩,优化后的电机齿槽转矩下降63.4%,电机的动态输出性能得到提升。     

电动车用的无刷直流电机控制系统仿真

介绍一种电动车用的无刷直流电机的双闭环调速系统的仿真,该系统利用PWM调制方法对无刷直流电机的定子各相电压进行控制,从而达到控制电机转速的目的。电流的检测反馈环节,根据转子角度,采用移相的方法得到不同时刻的转矩电流值。将各模块组合在一起构成仿真系统,通过示波器得到性能较好的适合电动车用的电机转速曲线。     

微型斜超声波电机的研究

提出一种新型微超声波电机——斜齿型微超声波电机。它是利用压电材料的逆压电效应，将交流电信号转变成定子表面超声频率的机械纵向振动，借助于定子表面的斜齿与转子的相互压紧，使斜齿端面质点产生椭圆运动，实现转子单方向旋转运动，该电机的驱动力矩较大、反向自锁力矩大、结构简单。文中将定子斜齿与转子接触分为三个阶段——接触黏着阶段、接触滑移阶段和分离阶段，建立定子斜齿与转子耦合的非线性动力学模型，并对其进行仿真研究，分析电机的瞬态响应特性及主要结构参数对电机机械特性的影响；最后，研制了尺寸为乃10的斜齿型微型超声波电机，经过实验表明，电机的堵转力矩可达10mN·m以上，空载转速达到840r／min以上，连续运转性能良好。     

超声电机特性测试平台的设计与实现

为测试和分析超声电机的关键性能,设计并实现了一种高精度、功能强大的超声电机特性测试平台.测试平台硬件部分采用电机加载方式对超声电机实施加载,并利用转矩转速传感器测量转矩转速,高精度功率分析仪分析驱动信号,软件部分采用Visual C++和MATLAB混合编程实现各部分与上位机间的通信以及数据的采集、分析和处理.最后基于设计的测试平台进行了超声电机静态特性测试的实验,验证了测试平台的可应用性.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.