基于二级杠杆机构的二自由度微定位平台设计与分析

针对由压电陶瓷驱动的微定位平台工作行程不足的问题，设计了一种基于二级杠杆机构的二自由度微定位平台。考虑到不同柔性铰链的物理特性，通过差异化的铰链组合方式来优化新型二自由度微定位平台的性能，使其具有较快响应速度和大范围输出位移。基于拉格朗日定理，构建了新型二自由度微定位平台的刚度模型，并推导了其固有频率的解析表达式。有限元仿真结果表明，该二自由度微定位平台刚度模型的误差较小，验证了刚度建模方法的准确性和可靠性。研究结果可为柔性精密微定位平台的构型设计和建模分析提供一定的理论指导。     

微小型平面机器人

微小型平面机器人可在显微镜下等狭小的空间内实现精密定位.压电元件与柔性铰链机构结合能实现精密定位,并使定位系统小型化,它可用于设计微小型平面机器人.为使平面机器人的结构更加紧凑,提出了单驱动三自由度运动机构.柔性铰链机构采用对称设计,以实现导向功能.应用蠕动式的运动原理可合成机构上的三自由度运动,并实现大行程运动.装配后的微小型平面机器人尺寸仅为20mm×20mm×12mm.研制了图像处理位移检测系统以检测微小型平面机器人的三自由度位移.     

基于压电陶瓷驱动的精密定位平台研究

设计了一种基于压电陶瓷驱动的整体式柔顺精密定位平台. 建立了柔性铰链的刚度矩阵,给出了平台的理论分析模型;利用模糊自整定 PID 控制算法对压电陶瓷驱动器进行了闭环控制,提高了驱动器的输出位移精度;提出了一种实验修正方法,提高了平台的定位精度. 实验结果表明,平台具有亚微米级的定位精度以及良好的动态特性.     

新颖微型压电旋转关节的建模与仿真

提出一种基于惯性冲击驱动原理的新颖微型压电旋转关节,用于关节臂式多自由度定位操作系统的旋转关节驱动.该旋转关节采用对称的整体结构设计,利用压电堆产生驱动力矩,通过碟形弹簧调整预紧力,具有运行稳定、驱动力矩大、易于微型化等优点.建立了该机构驱动模块的结构模型,运用ANSYS软件分析了定子结构的静态变形和固有振动特性;建立了该机构的动力学模型,应用MATLAB/Simulink软件获得了旋转轴的粘滑运动和步进位移特性.仿真结果表明,该压电旋转关节具有较好的步进位移输出能力和较宽工作频率范围,在1 000 V/mm激励电场下,步进位移达到0.07°,稳定的粘滑工作频率达到1 000 Hz以上.     

多自由度压电纳米定位平台控制技术研究现状

介绍了压电驱动的工作原理、压电材料的非线性特性以及压电定位平台的直接驱动方式,分别阐述了串联、并联和串并联三种驱动方案的多自由度压电定位平台的结构设计以及解耦优化方式。重点分析了多自由度纳米压电定位平台控制系统需要解决的压电驱动器的非线性特性、交叉耦合等问题,提出应根据多自由度压电定位平台不同的结构和运动形式选定合适的控制策略。最后总结了适用于多自由度压电定位平台的控制算法,有助于研究者了解压电纳米定位平台领域的最新进展,为压电纳米定位平台控制技术研究提供借鉴。     

新型纳米分辨率位移定位平移台的研制

为克服已有压电驱动器存在的结构及控制系统复杂、定位行程小等缺陷,利用压电陶瓷的逆压电效应设计并制作了一种新型的压电纳米步进驱动器,建立光栅测试系统对这种压电驱动器的动态性能进行了测试.将压电纳米步进驱动器与电磁伺服马达耦合,设计新颖驱动结构,利用微机通过步进运动控制卡统一控制,实现大范围一维纳米分辨率位移定位.系统样机解决了所研制压电纳米步进驱动器双向运动、实用定位等问题.位移定位分辨率为50 nm,定位行程为100mm,纳米分辨率定位最大速度为0.6 mm/s.     

六维宏微位移可控精密工作台的研制

研制了一种六维宏微位移可控精密工作台。设计中采用粗精分离的原则,有利于提高工作台的精度,并减小了研制难度。宏位移使用精密燕尾导轨结构。微定位系统使用了压电陶瓷驱动器、柔性铰链和计算机控制,使系统具有极高精度的补偿定位能力。该工作台可在 100mm 范围内运动,平移分辨力为 0.05μm,转动分辨力为 0.3″。     

带柔性铰链的Stewart平台特征值的求解

Stewart六自由度平台在许多方面均有重要的应用，它的连接部件一般为球铰或万向铰，不可避免会产生间隙，这在微小位移的应用中是不允许的。因此，本文采用了无间隙的柔性铰链作为Stewart六自由度平台的连接部件，并推导了带柔性铰链的弹性支杆构成的Stewart平台的动力学方程并编程序求解了特征值问题，经ANSYS软件和实验验证，计算结果正确，表明理论能描述此平台的特性。     

基于超磁致伸缩和压电陶瓷的XY超精密定位工作台

基于蠕动运动原理,利用超磁致伸缩材料作为驱动元件研制了直线式蠕动进给机构,同时还研制了压电陶瓷-柔性框架式蠕动进给机构．后者放置于前者之上,构成了具有毫米级行程、纳米级定位精度的XY二维精密定位工作台．在计算机控制下,对XY向位移分别进行了闭环反馈控制并测试了它们的步进性能．试验结果表明,工作台在X和Y方向上可以稳定地蠕动步进或后退,X向蠕动机构定位精度为±15 nm,Y向蠕动机构定位精度为±50 nm．     

一种新的大行程垂直纳米运动工作台设计与控制研究

在大行程高精度垂直运动中,工作台的设计及稳定控制是关键因素。因此设计一种新型的具有平衡机构的工作台,以实现垂直方向上大行程纳米稳定运动。所研究工作台采用N331压电直线电机独立驱动,通过空气静态导轨悬浮,设计Z轴平衡系统降低垂直向电机驱动负载。利用步进控制方式完成大行程驱动,模拟方式实现微位移精密驱动控制。所提出的驱动与控制策略,可实现100 mm垂直方向上高精度快速精密驱动。另Z向也可实现纳米步进模式与模拟模式的复合控制。在全行程100 mm的范围内定位波动可限制在±9 nm内。通过验证实验,本运动工作台可适用于微纳米三坐标测量机、微光刻和微加工应用的驱动与控制任务。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...