振动条件下陀螺加速度计误差抑制技术

为了减小振动条件下惯性平台陀螺加速度计的振动误差,提出一种基于陀螺加速度计进动时间数据的整周小波去噪测试方法。该方法在静态和线振动状态下分别测量平台系统中陀螺加速度计进动整周期的相关时间数据,基于改进小波方法进行去噪后,得到静态和线振动状态下的时间序列,经计算得到陀螺加速度计的振动误差。该方法能抑制陀螺加速度计输出平均角速率误差,提高陀螺加速度计随平台系统在线振动台上的测量精度。最后采用实测数据验证算法的有效性,辨识精度达到10~(-7),该方法提高陀螺加速度计随平台系统在线振动台上的振动精度。     

振动条件下陀螺加速度计误差抑制技术

为了减小振动条件下惯性平台陀螺加速度计的振动误差,本文提出了一种基于陀螺加速度计进动时间数据的整周小波去噪测试方法。该方法在静态和线振动状态下分别测量平台系统中陀螺加速度计进动整周期的相关时间数据,基于改进小波方法进行去噪后,得到静态和线振动状态下的时间序列,经计算得到陀螺加速度计的振动误差。该方法抑制了陀螺加速度计输出平均角速率误差,能够提高陀螺加速度计随平台系统在线振动台上的测量精度。最后采用实测数据验证了算法的有效性,辨识精度达到 ,提高了陀螺加速度计随平台系统在线振动台上的振动精度。     

振动信号测试与分析

正电测法是最为广泛使用的振动测量方法,也是目前的主要测振手段。本文设计了基于AVR单片机的振动信号测试系统,有效解决了振动信号检测不准确的问题。该方案设计灵活,可很简单地移植到各种振动信号检测系统中。一、系统总体设计1.压电传感器振动测试当压电传感器的压电元件受到外界的作用力时,在压电元件的两个电极表面就会出现与外界作用力成正比的电荷,且两个电极表面聚集的电荷量相等,极性相反。因此,可以把压电传感器看作一个电荷发生器,     

Study and verification of an online secondary path identification algorithm for adaptive filtering based control of structural vibration

针对基于自适应滤波的振动控制算法的误差通道辨识问题,提出一种在实施该控制算法中进行误差通道模型实时在线辨识的方法.其基本思想是在振动主动控制器输出端引入一个白噪声信号,采用有限脉冲响应滤波器作为误差通道模型进行实时在线辨识,利用性能判别器实时控制辨识环节的停止与否,同时振动主动控制采用滤波-X算法.给出了具有在线辨识功能的控制器结构与算法过程,并结合实验模型结构和测控平台进行了实验分析与验证.基于MATLAB进行相关算法仿真,分析引入白噪声信号对辨识模型误差的影响,提出了一种辨识模型误差判定准则,并分析对振动控制系统性能的影响;基于实验平台进行了压电机敏柔性结构振动主动控制的验证.实验结果表明,控制通道模型实时在线辨识策略是成功的,由此验证了所设计的控制器及其控制算法的可行性和有效性.     

基于信号时频分解的模态参数识别

给出了基于响应信号Gabor展开与重构的模态参数辨识的时频分析方法。通过响应信号的展开与重构，单频特征振动可从复杂的响应信号中分离出来，由它些特征振动信号可进一步提取系统物模态振动参数。论述了频率、阻尼和特征振型的估计方法以及估计方法对系统响应信号的特殊要求。此方法可适用于平衡、非平衡的响应信号，且无需输入信号，属于环境激励下的一种参数辨识方法。仿真结果说明明频展开与重构方法是模态参数辩识的有效手段之一。     

电极配置对悬臂梁压电振子发电能力的影响

研究了带末端质量块的悬臂梁压电振子多模态振动时的应变分布特点,针对压电陶瓷表面电极配置对压电振子输出电压的影响关系进行压电-电路耦合有限元分析,并建立悬臂梁压电振子发电测试系统,对工作在一阶和二阶谐振频率附近处的压电振子分段电极和连续电极输出功率进行对比分析。研究结果表明,一阶谐振时分段电极的峰值输出功率与连续电极相接近,二阶谐振时分段电极的峰值输出功率增加了900%。相比于连续电极配置法,分段电极配置法可有效提高压电振子在高频振动时的发电能力。     

磁力非线性耦合的I-L组合压电梁俘能器发电性能试验研究EI北大核心CSCD

针对线性的压电振动俘能器俘能频带过窄,输出较低等问题,提出了一种磁力非线性耦合的I-L组合压电梁俘能器。俘能器由带永磁铁的I型压电梁和L型压电梁组成,可通过调节两永磁铁间的水平距离,得到不同的非线性磁力耦合效应。试验结果表明:存在最优电阻使压电俘能系统的输出功率最大;对比无磁力系统,磁力耦合的I-L组合压电梁俘能器共振频率发生了明显的偏移:I型压电梁向左偏移,L型压电梁向右偏移,拓宽了系统的俘能频带;当激励加速度为0.2 g水平距离为20 mm、激振频率为18.4 Hz时,俘能器最大可得到1.2 mW的输出功率。     

一种带谐振腔的压电风能收集器

为了提高风能收集器的能量转化效率,提出了一种带谐振腔的压电风能收集器。建立了该压电风能收集器的数学模型,该模型考虑了风流体、结构振动以及输出电能之间的关系。基于该模型进行了仿真分析,获得了收集器结构参数、风速对发电能力的影响规律。制作了风能收集器样机,并进行了实验,结果表明,在2~12 m/s的低风速范围内,带有谐振腔的压电风能收集器的输出电能要大于不带谐振腔的收集器。     

基于LabVIEW的陀螺仪振动信号采集与分析

针对陀螺马达振动信号的微弱性,通过数据采集卡检测到的信号要进行大量复杂的线形系统分析,要求数据准确,根据虚拟仪器设计思想在PC下利用图形化编辑语言LabVIEW对陀螺马达的振动信号进行过采样数据采集、波形显示、时域分析、数字滤波、数据存储、频域分析,从而实现对振动信号的多通道信号采集和实时分析.系统逻辑图形清晰,可以有效的防止波形失真,误差小,起到了很好的故障诊断分析作用,在工程应用中实用性强.     

基于包络同步平均的齿轮故障诊断

齿轮振动信号由于存在非平稳、调制、传递路径复杂等特点,其分析相对较为困难,传统的共振解调法还存在共振带参数无法准确确定的不足。为解决上述问题,本文提出了一种基于包络信号角域同步平均的齿轮故障诊断方法。该方法首先利用谱峭度提取出齿轮振动信号的复包络信号,再分别选取齿轮箱中不同转轴作为参考轴对复包络信号进行等角度采样,在角域进行同步平均并用阶比跟踪提取齿轮故障信息。该方法可有效消除源包络信号中的宽带噪声干扰,分离出与故障齿轮所在轴有关的阶比分量,同时可克服转速波动对信号分析产生的频率模糊现象。利用该方法分别对齿轮故障仿真信号和齿轮故障振动信号进行了分析,结果表明,所提出的包络角域同步平均方法能够有效地提取出齿轮故障的特征信息。     

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.……     

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.     

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...     

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 ...