基于阶跃激励的外差激光测振仪传递函数评价

提出了激光测振仪传递函数的一种测量方法,借助于外调制状态下的FM信号源激励,以数字存储示波器进行同步波形测量,直接获得激光测振仪阶跃响应波形,用数字化解调方法解调出FM信号中的阶跃调制波形,利用该组阶跃激励--响应序列进行系统辨识,获得激光测振仪的传递函数评价结果;一组实验结果验证了该方法的正确性和可行性.所述方法可用于激光测振仪传递函数和频率特性的测量评价,同时,也可用于FM信号源传递函数和频率特性的测量评价.     

消除噪声干扰的动态测量方法研究

由于测量噪声和补偿器的频率特性,使得传感器的动态补偿器存在严重的噪声干扰,影响到补偿器的参数辨识和补偿后的测量精度。研究了一种消除噪声干扰的动态测量方法,先通过小波变换估计噪声的方差,再由估计得到的方差,通过偏差消除的递推最小二乘法,对补偿器的参数进行无偏辨识;同时,采用多项式实时滤波器,消除高频噪声对测量精度的影响。最后,通过实验验证了该方法的有效性。     

单屏蔽式温度传感器动态建模及补偿技术研究

单屏蔽式温度传感器一般用来测量发动机高速气流总温,本文依据其动态校准试验数据,采用系统辨识方法建立了它的动态试验数学模型.根据辨识的数学模型,采用一种快速的动态补偿算法,得出了传感器动态补偿器的传递函数,为下一步在硬件上设计实用的温度传感器动态补偿器打下了坚实的基础.     

直流电机复合定位控制系统性能分析及系统优化

在直流电机复合定位控制系统(CPCS)设计过程中,发现电机速度等动态响应曲线发生振荡,表现出一定程度的不稳定性.为探究这一振荡与控制系统内在结构之间的关联性,使用MATLAB对PID及CPCS系统动态响应、根轨迹及频率特性等进行分析、比较.结果显示：高阶控制系统的传递函数总可以通过降阶等方式简化为具有1个实数零点、1个实数极点和2对复共轭极点的基本形式.其中离原点位置较近处的一对复共轭极点的移除是造成CPCS系统稳定性下降,产生振荡的根本原因.该振荡可通过增大另一对复共轭极点实部或减小虚部的方法予以降低或消除.这一结论对提高控制系统的定位精度和稳定性具有重要的参考意义.     

基于有限元分析的复杂结构弹性振动传递函数建模

为了解决复杂结构的弹性振动建模问题,提出了一种基于有限元分析的弹性振动传递函数建模方法。首先建立能够准确反映结构动力学特性的有限元模型;然后根据输入参数和辨识算法类型的不同,分别从时域和频域两方面进行传递函数建模,其中时域辨识建模以PRBS信号的瞬态响应结果为辨识数据进行时域参数辨识,频域辨识建模以结构的频率响应函数为辨识数据进行频域参数辨识;最后以“时域建模频域验证,频域建模时域验证”的方法检验传递函数的精度。通过建立悬臂梁、某运载火箭和某弹体局部结构的传递函数模型,证明了该方法的可行性和有效性,为该方法在工程实践中的应用提供参考。     

重复控制逆变器并网电流控制技术研究

针对在逆变电源系统中因模型的不精确及系统负载的非线性、以及常规方法中基于完美对消思想设计的重复控制器无法满足逆变电源的控制需求且设计复杂等问题,提出一种新的重复控制器设计方法,利用数字滤波器代替重复控制补偿器,并将内模系数和补偿器等效为同一个低通滤波器。将改进后的重复控制器与PI控制相结合,形成复合式控制系统,进一步提高电流跟踪速度,减小电流谐波含量。并通过运行Matlab仿真模型和具体实验平台测试,验证该方法的可行性和良好性能。     

数字前馈跟踪控制器的频域迭代设计方法

 数字前馈控制器用于提高伺服系统跟踪性能,在工程应用中通常包含如下设计环节：闭环对象参数辨识、闭环离散化和设计前馈控制器,上述各环节都会引入设计误差,最终导致所设计的前馈控制器跟踪性能变差.针对上述问题,利用闭环对象的实测频率特性数据,提出一种新型的频域迭代设计方法,能有效消除各环节误差.通过对设计过程的频率特性差值的变化分析,给出了迭代算法的步骤.该方法将反馈控制思想引入前馈控制器设计过程,根据频率特性差值,不断修正对象频率特性数据,通过设计过程的迭代,使跟踪误差显著减小.以某飞行转台伺服系统为例,进行数值仿真和应用研究,结果表明了该方法的有效性,能显著拓宽伺服系统的跟踪频带,减小对低频信号的跟踪误差．     

传统控制器实现有摩擦系统的大行程纳米定位

对于“伺服电机＋滚珠丝杠”驱动机构,摩擦、饱和和高频振动等非线性因素是实现大行程无超调高精度点位（PTP）控制的主要障碍．针对这种驱动系统,在根据刚体动力学计算得到的线性传递函数的基础上,设计了高增益PID闭环控制系统和输入滤波器来实现大行程的纳米定位．配置闭环控制系统的极点为负实轴上的多重极点．避免了摩擦力补偿和双模控制策略的使用．为了避免驱动器饱和所导致的闭环系统响应超调现象,基于数字低通滤波器设计了闭环输入信号．实验结果表明,该定位系统可以实现大行程无超调纳米精度点位控制,10nm-100mm定位响应的稳态误差不超过±5nm．     

高阶声学相对传递函数的参数化辨识

针对声学相对传递函数的模型阶次高以及辨识数据信噪比低的问题,文章运用频域系统辨识方法,建立了一种相对传递函数的高精度参数化辨识方法。首先建立变量带误差辨识框架,采用周期扫频信号作为声源激励,给出声学相对传递函数的极大似然算法。然后使用正交福赛斯(Forsythe)多项式解决高阶系统带来的雅克比矩阵条件数过高的数值问题,并建立了极大似然方法所需初始值的生成策略。最后通过仿真算例和实验测试,验证文中方法在混响声场下辨识声学相对传递函数的有效性。     

电阻应变数据采集系统传递函数的评价

提出了电阻应变数据采集系统传递函数的一种辨识方法,给出了详细技术过程,包括:电阻应变阶跃激励源的构建与赋值,电阻应变阶跃信号波形的获取,应变放大器恒定时间延迟的测量估计,用等效采样方式获取电阻应变数据采集系统的阶跃响应序列,激励序列和响应序列的时序统一与合成,用一种特殊白化滤波器的最小二乘法进行电阻应变数据采集系统传递函数辨识等。在一组实验中的传递函数辨识应用,证明了该方法的有效性及可行性。该方法可用于电阻应变数据采集系统动态特性的计量校准,及其传递函数辨识。     

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.……     

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.     

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.     

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.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from