一种压电式六维加速度传感器的校准方法研究

基于多只压电式单轴加速度传感器的压电式六维加速度传感器的传感误差主要由多只压电式单轴加速度传感器的安装误差和输出误差决定.为了对压电式六维加速度传感器的传感误差进行估计和补偿,提出并研究了一种压电式六维加速度传感器的校准方法,建立了压电式六维加速度传感器的校准模型.在此基础上,分析了校准过程中加速度激励误差对校准结果的影响和最佳角加速度激励频率的范围,建立了对校准误差进行估计的方法.研究结果表明,利用所建立的校准方法和校准误差估计方法不仅能够准确地实现压电式六维加速度传感器的校准,而且能够对校准结果的误差进行估计.该研究工作为压电式六维加速度传感器的误差补偿和精度提高奠定了基础.     

一种快速的数字电能表校准方法研究

针对广泛应用于供电系统的数字电能表的特点,分析了现行脉冲法校准电能表的不足.提出一种基于准同步采样算法的功率校准方法,描述了新方法的工作原理和实现过程,介绍了在新方法中如何利用采集的被校表的数据校准该表计量误差的方法,最后验证了所提出算法的正确性.相对于当前普遍采用的脉冲校表法,新方法不仅能够更准确的校准电能误差,而且省去了积分时间提高了校表效率,降低了成本和能耗,有很好的参考价值.     

轮廓扫描式螺纹中径测量的两规校准补偿方法

轮廓扫描式螺纹参数测量的过程中,由于工件和探针的装夹会不同程度地产生定位误差,导致中径测量结果不准确.然而各项定位误差的准确测量十分困难,加上误差模型的不完备,现有的相对测量方式(单规校准)只能测量与校准规尺寸相差不大的螺纹量规.特别是批量检测螺纹规时需要准备一批不同尺寸的校准规,且花费了很多的校准时间.基于齐次坐标变换建立了定位误差对中径结果影响的数学模型.依据该模型,利用两个不同尺寸的螺纹规校准定位误差,再对中径结果进行补偿.此外对最终结果的不确定度进行了分析,并给出了减小测量不确定度的校准规选用方法.实验结果显示,此方法只需要两个校准规,就能确保M15 ～ M50范围内螺纹的定位误差对中径结果的影响小于1μm.相比于单规校准,两规校准补偿方法虽然增大了测量结果的不确定度,但有效减小了校准规数量和对工件、探针定位精度的要求.     

基于椭球拟合的三轴磁强计两步校准法

在传统的基于椭球拟合校准法的基础上,提出了两步校准法.第一步引入中间变量,采用最小二乘法通过求解准线性方程来获得最优解,完成对总磁场和零位偏差的校准.第二步通过求解非线性方程组,完成灵敏度误差和三轴不正交性误差的校准.数值模拟和实际校准实验均表明,该方法能有效校准三轴磁强计由于制造工艺带来的误差,且引入中间变量可以有效...     

化工企业温度测量系统误差分析方法及对策

本文运用分立单元校准和系统校准的方法对温度测量系统进行了校准,并提出后者的优越性。结合工作实践,在校准过程中对系统的误差来源及形成原因进行分析,给出了相应的建议和对策。结呆表明,误差分析的思路和对策能有效解决大部分的误差问题,对化工企业温度测量有一定的应用价值。     

化工企业温度测量系统误差分析方法及对策

本文运用分立单元校准和系统校准的方法对温度测量系统进行了校准,并提出后者的优越性。结合工作实践,在校准过程中对系统的误差来源及形成原因进行分析,给出了相应的建议和对策。结果表明,误差分析的思路和对策能有效解决大部分的误差问题,对化工企业温度测量有一定的应用价值。     

基于牛顿迭代和椭球拟合的磁力和惯性传感器校准方法

传统的磁力和惯性传感器校准方法主要面向惯性导航系统,通常都需要借助高精度转台或更高精度的传感器以获取参考输出,校准设备昂贵,过程复杂耗时,不适用于运动捕获系统中的消费级传感器。提出一种基于牛顿迭代和椭球拟合的低成本、方便、快速的磁力和惯性传感器校准方法。首先分析了传感器的误差模型,然后提出牛顿迭代法校准加速度计和陀螺仪、椭球拟合法校准磁力计的方法,使用自主设计和制作的校准设备,经过两步实验同时校准3种传感器。实验表明,校准后的加速度计输出均方根误差由2.536 m/s~2降至0.096 m/s~2,陀螺仪旋转10 min角度积分误差由1 318°降至25°,磁力计输出均方根误差由46.16 nT/m降至2.13 nT/m。此方法不仅降低了传感器的校准成本,而且简化了校准流程,为磁力和惯性传感器的校准提供了一种可靠解决方案。     

基于星座图设计的矢量调制误差计量方法研究

提出了一种基于星座图设计来实现对矢量信号发生器输出数字调制信号的调制误差进行准确设置的新方法,给出了方法的理论推导过程、方法的实现,以及实验验证.该方法可以用于实现对矢量信号分析仪在非零调制误差处测量准确度的校准,也可以用于数字调制误差参数量值比对传递标准的研制中.     

基于电能表的单点校正检测算法研究

针对电能表在生产过程中计量误差校准效率不高的问题,提出了单点校正的校表方法。通过在校表台上输入额定电流Ib,额定电压Un,选择单相有功计量模式,功率因数设置为0.5L时,同时校正角差,功率比差,电压比差和电流比差。实验研究结果表明,本文提出的误差检测方法能快速且准确校准电能表的计量误差,较大的提高生产效率。     

基于回波替代的毫米波矢量网络测试校准方法

毫米波频段矢量网络测试是射频半导体器件建模和电路设计中不可缺少的环节。提出了一种新型的旨在提高毫米波频段测试精度的校准方法。该方法通过反向注入回波的方式来降低毫米波频段矢量校准中传输线原始测量数据的不确定性,进而降低了校准过程中对校准件精度的要求,获得了更具鲁棒性的校准误差模型参数。基于国产AV3672矢量网络分析仪在1～50 GHz内对该校准方法相较于传统校准方法的有效性进行了验证。采用这种方法校准后,直通校准件的S_(21)测试误差下降至0.02 dB,短路校准件S_(11)误差下降至-50 dB。实验结果证明,该方法在不依赖于昂贵的附加仪器仪表设备的同时,明显提升了毫米波矢量测试精度,而且算法复杂度并没有急剧增加,具备极强的实用性和通用性。     

Reproducibility and accuracy of spatial measurements from digitally captured images in the environmental scanning electron microscope

Accurate spatial measurements in a scanning electron microscope (SEM) require calibration of the magnification as a function of working distance and microscope operating conditions. This work presents the results of the calibration of an environmental SEM for the accurate spatial measurement of dimensions and areas in experiments, both for the measurement of strain in steel specimens under applied loads and the measurement of dimensional changes in timber with changes in relative humidity.     

A technique for obtaining scanning electron micrographs in colour.

A digital electronic unit is described which, by modifying the video signal of the scanning electron microscope (SEM), permits the selection of images in separate tonal or grey-scale levels. By the sequential exposure of these grey levels onto colour film with the intervention of colour filters, coloured scanning electron micrographs have been obtained. Full details of the procedure are given. The process is applicable to any normal image capable of being displayed at the scanning electron microscope.     

Design and fabrication of a scanning electron microscope using a finite element analysis for electron optical system

In this paper, we describe the design and fabrication of a thermionic scanning electron microscope (SEM) and examine its characteristics analytically. In the design process, the dimensions and capacity of the SEM components, such as the electron column, lenses, and apertures, were determined using finite element analysis. All components were integrated systematically during fabrication in order to achieve the maximum performance by adjusting the lens parameters, high voltage source, and image calibration methods. As a result, a thermionic SEM image with high resolution was achieved. We discuss the primary considerations required to achieve a high-performance image.     

Imaging biological macromolecules by STM: quantitative interpretation of topographs

Methods are discussed which permit the calibration of x-, y-, z-sensitivities, non-linearities and frequency responses of the scanning device of a scanning tunneling microscope (STM) either by interferometry or directly from STM topographs. A technique is presented to measure the frequency response of the complete STM feedback unit and to derive a maximum speed in z direction which allows one to estimate the maximum scanning speed still permitting one to track surface corrugations. The signal transfer characteristics of a STM are evaluated in a direct comparison with high resolution transmission electron microscopy on an identical specimen area. The various effects of contaminants between tip and specimen and the finite tip radius receive special attention.     

Real-time image quality assessment with mixed Lagrange time delay estimation autoregressive (MLTDEAR) model

A proposal to assess the quality of scanning electron microscope images using mixed Lagrange time delay estimation technique is presented. With optimal scanning electron microscope scan rate information, online images can be quantified and improved. The online quality assessment technique is embedded onto a scanning electron microscope frame grabber card for real‐time image processing. Different images are captured using scanning electron microscope and a database is built to optimally choose filter parameters. An optimum choice of filter parameters is obtained. With the optimum choice of scan rate, noise can be removed from real‐time scanning electron microscope images without causing any sample contamination or increasing scanning time.     

Scanning probe microscopy installed with nanotube probes and nanotube tweezers

We have developed well-controlled processes for the growth and manipulation of carbon nanotubes. The relatively thin multiwalled nanotubes were prepared with high purity by arc discharge with a high gas temperature. In the manipulation of nanotubes, the first crucial process is to prepare a nanotube array, so-called nanotube cartridge. We have found the alternated current electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge of a disposal razor. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope. Using this method, we have developed nanotube probes and nanotube tweezers that operate in a scanning probe microscope (SPM). The nanotube probes have been applied for observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have been demonstrated for their motion in scanning electron microscope and operated to carry a nanomaterial in a SPM.     

Quantitative secondary ion mass spectrometry imaging of self-assembled monolayer films for electron beam dose mapping in the environmental scanning electron microscope

Fluorinated alkanethiol self-assembled monolayers (SAM) films immobilized on gold substrates have been used as electron-sensitive resists to map quantitatively the spatial distribution of the primary electronbeam scattering in an environmental scanning electron microscope (ESEM). In this procedure, a series of electron dose standards are prepared by exposing a SAM film to electron bombardment in well-defined regions at different levels of electron dose. Microbeam secondary ion mass spectrometry (SIMS) using Cs⁺ bombardment is then used to image the F^- secondary ion signal from these areas. From the reduction in F^- intensity as a function of increasing electron dose, a calibration curve is generated that allows conversion of secondary ion signal to electron dose on a pixel-by-pixel basis. Using this calibration, electron dose images can be prepared that quantitatively map the electron scattering distribution in the ESEM with micrometer spatial resolution. The SIMS imaging technique may also be used to explore other aspects of electron-surface interactions in the ESEM.     

Analytical scanning electron microscopy for solid surface

A scanning electron microscope of ultra-high-vacuum (UHV-SEM) with a field emission gun (FEG) is operated at the primary electron energies of from 100 eV to 3 keV. The instrument can form the images that contain information on surface chemical composition, chemical bonding state (electronic structure), and surface crystal structure in a microscopic resolution of several hundred angstroms (Å) using the techniques of scanning Auger electron microscope, scanning electron energy loss microscope, and scanning low-energy electron diffraction (LEED) microscope. A scanning tunneling microscope (STM) also has been combined with the SEM in order to obtain the atomic resolution for the solid surface. The instrumentation and examples of their applications are presented both for scanning LEED microscopy and STM.     

Beam transfer characteristics of a commercial environmental SEM and a low vacuum SEM

Two commercial instruments that permit a gaseous environment in their specimen chamber have been investigated, namely, a 'FEI Quanta 600 FEG' environmental scanning electron microscope and a 'LEO SUPRA 35VP FESEM' low vacuum scanning electron microscope. The gas flow field is first computed by the direct simulation Monte Carlo method and the gas density gradient, speed, Mach number and temperature are found in the transition region from high pressure to vacuum. The electron beam transfer characteristics are then derived for different accelerating voltages and pressures and a comparison is made among different situations and with some published works. Certain physical parameters are analysed and discussed to establish a figure of merit that can be used as a standard performance specification for commercial environmental scanning electron microscope and low vacuum scanning electron microscope.