Characterization and calibration of MEMS inertial sensors for state and parameter estimation applications

Widening applications of inertial sensors have triggered the search for cost effective sensors and those based on MEMS technology have been gaining popularity and widespread use particularly for lower cost applications. However, inertial sensors are subject to various error sources and characteristics of these should be modelled carefully. Corrective calibration is required for successful use for anything but the most trivial applications, body state estimation and navigation being important application areas. In this paper, we review the deterministic error and random noise sources for these sensors, consider a number of inertial sensor calibration tests to provide models for these errors and derive the calibration parameters for MEMS based strapdown IMUs. We carry out these tests and present the results for a low cost and popular IMU. We further provide performance results for an example application of body state and parameter estimation using the derived calibration data and discuss our results.     

温湿度传感器检定装置对比实验与分析

合理选取HMP45D温湿度传感器的检定装置对提高校准质量、节约校准成本具有重要意义。文中基于本单位现有的4台温湿度检定装置,通过大量的对比实验,分析了不同装置对HMP45D温湿度传感器校准质量的差异。结果表明：恒湿盐湿度发生器和DJM10型湿度检定箱具有较高的性价比,适合作为HMP45D温湿度传感器的检定装置。具体来说,恒湿盐湿度发生器适合HMP45D温湿度传感器的现场校准工作,而湿度检定箱更适合完成室内校准任务。     

基于红外测湿传感器的湿度检定箱设计

文章介绍了一种新型湿度检定箱,其温度控制采用高效气液换热,湿度控制采用干湿气混合法反馈控制原理,湿度测量采用红外激光吸收式湿度传感器。通过实验测试,新型湿度检定箱的温度、湿度均匀度和波动度都优于目前计量测试部门使用的所有湿度检定箱,且测试室容积大,可对毛发湿度表(计)、干湿表等大型测试仪表和湿度传感器等进行检定测试,还可同时进行温度校准,具有很好地推广应用价值。     

自动气象站现场校准编证系统的设计与实现

自动气象站的周期性校准是数据质量控制的重要环节,对及时发现可疑数据,提高数据的可用性具有重要作用。在自动气象站不断增多,校准工作量大幅度增加的情况下,原始数据处理及证书出具工作越发繁重,针对这种情况研制了自动气象站现场校准编证系统。系统采用三层结构设计,包括台站信息管理、现场校准和标准器信息管理三大模块,实现了现场校准、原始数据自动处理和校准证书打印及管理等功能,现场测试结果表明系统操作方便、校准结果准确性高。     

Adaptive calibration of a capacitance tomography system for imaging water droplet distribution

A highly sensitive electrical capacitance tomography (ECT) system based on an HP4284 impedance analyser has been developed and used to quantify low concentration multi-phase flows in wet gas separation processes. The system hardware provides high accuracy (0.05%) and high resolution (10⁻¹⁷ F). The sensor was calibrated in an environmental chamber with solid samples of known permittivity over ranges of temperature and humidity. Adaptive calibration and adjacent electrode pair correction techniques were applied to image very low concentration profiles. This paper describes the techniques used and presents the experimental results obtained from a test flow rig called Twister, which has been designed to separate liquid droplets from wet gas streams. The test results over a range of operating conditions (20–95% humidity) demonstrate that the ECT system is capable of reconstructing clear images of the droplet distribution inside Twister. Changes as small as 1 gWater/kgAir in the form of liquid droplets were detectable. It has also been shown that the concentration of the condensable phase can be estimated quantitatively within 20% in comparison with the reference measurements.     

Lensed optical fiber sensors for on-line measurement of flow

This paper describes a system using lensed optical fiber sensors that are arranged in the form of two orthogonal projections. The sensors are placed around a process vessel for upstream and downstream measurements. The purpose of the system is for on-line monitoring of particles and droplets being conveyed by a fluid. The lenses were constructed using a custom heating fixture. The fixture enables the lenses to be constructed with similar radii resulting in identical characteristics with minimum differences in transmitted intensity and emission angle. By collimating radiation from two halogen bulbs, radiation can be obtained by the sensors with radiation intensity related to the nature of the media. Each sensor interrogates a finite section of the measurement section. Each sensor provides a view. Parallel sensors provide a projection. Signal processing is carried out on the measured data in the time and frequency domains to investigate the latent information present in the flow signals.     

Traceable calibration of transfer standards for scanning probe microscopy

A Metrological Atomic Force Microscope (MAFM) has been constructed for the traceable calibration of transfer standards for scanning probe microscopy. It uses optical interferometry to generate image scales with direct traceability to the national standard of length. Three interferometers monitor the relative displacements of the AFM tip and sample in the x, y and z directions and the interferometer data is used directly to construct 3D images of sample surfaces. Traceable dimensional measurement of surface features may then be derived from the image data. This paper describes the MAFM instrument and presents a measurement uncertainty budget. Examples are given of measurements of pitch and step height on calibration transfer standards for scanning probe microscopy.     

电容层析成像系统传感器设计新方法

在电容层析成像系统中,为了提高重建图像的精度,常用的方法是提高成像传感器的极板数目,以获得较多的图像重建所需的独立电容测量值数目,但这种方法是以牺牲检测场的灵敏度为代价的。该文提出了一种在有限极板数条件下通过改变极板的组合方式成倍提高成像系统的独立电容测量值数目的方法。仿真结果表明该方法在不降低检测场灵敏度的前提下提高了电容测量值数目,从而提高了图像重建质量。     

A novel approach for the field calibration of line structured-light sensors

A new approach for the field calibration of line structured-light sensors is presented, which is fulfilled using a planar target and a raising block. The camera model is firstly established according to the mapping between the world coordinate frame and the computer image coordinate frame. Based on the rule of cross-ratio invariance the calibration points are extracted from the squares on the target, and the lens distortion coefficients are simultaneously acquired. The unknown parameters in the camera model are solved using these points. On the projection of the laser plane, two intersection lines are formed by the laser plane with the target and the raising block, respectively. The angle between the laser plane and the target is worked out by fitting plane using the two lines. Utilizing this angle, the three coordinates of a point in the laser plane can be represented by two of them. Thus the two coordinates can be directly obtained from the camera model. This method simplifies the calibration procedure of structured-light sensors, and facilitates online use. Experiment studies show that the calibrated sensor possesses good accuracy.     

视觉测量系统的相机校准

提出了一种利用虚拟立体校准模板的有效相机校准技术.通过红外发光二极管按照预定路径在三坐标测量机上移动,构成精确的虚拟立体校准模板.校准过程中考虑了径向畸变和切向畸变.采用二次高斯曲面拟合,精确地提取像点的质心坐标.校准过程包括线性参数估计和基于最大似然估计的非线性校正.首先采用线性方法对部分参数进行初始估计,然后再通过基于最大似然估计的非线性最小化获得所有的参数值.该方法可精确获取图像点坐标和空间点坐标,能够实现快速、有效收敛.实验结果表明,该校准技术能够满足视觉测量系统的要求,也可以满足视觉测量系统对相机参数的特殊要求.     

Automatic calibration system for polygon mirrors

An automatic calibration system of polygon mirrors is described. This system consists of the four subsystems: a precise rotary mechanism, a rotary magnetic scale for angular standard, a special photo-electric autocollimator which enables dynamic measurement, and a mini-computer system which controls the compiling and handling of data. The basic principle of the system depends on the self-checking method, so that both the polygon mirror and the standard rotary scale are calibrated simultaneously. A time-conversion method is adopted to detect slight angular difference with high resolution. By way of an example, the calibration of a 12-sided polygon is described. The results obtained are as follows: (1) The calibration can be done automatically in a short time without skill, except for the manual operation of setting a polygon relatively for the magnetic scale; (2) 95% confidence interval of instrumental error calibrated on the system is within $\text{±0.07}$ seconds of arc.     

民航机场自动气象站传感器的现场校准

文章根据民航机场自动气象站的特点,以江苏省气象探测中心计量站多年来为民航机场自动气象站传感器进行现场校准的实践为基础,介绍了传感器的计量性能和标准器的校准条件,分析和总结了维萨拉公司MAWS301型自动气象站传感器的校准方法,旨在为民航机场提供更好的气象保障。     

Uncertainty evaluation of trigonometric method for vertical angle calibration of the total station instrument

The total station is an instrument, widely used in civil and environmental engineering, for flat and vertical angle as well as distance measurements. Typically, routine calibration of such an instrument is obligatory, and depending on the local regulations, is performed typically annually or bi-annually. Analysis of previous research shows that undertaking flat angle calibration under laboratory conditions is more common than calibration of vertical angle measuring systems. This paper deals with a trigonometric vertical angle calibration method and research into determining the main sources of uncertainty is described in the paper. The principle of the method is explained, as well as the uncertainty evaluation based on GUM and the advantages as well as the weaknesses of the setup are discussed.     

大视场多像机视频测量系统的全局标定

针对大视场多像机视频测量系统的全局标定,提出并实现了一种基于近景摄影测量技术的高精度像机标定方法.首先,设计一种带有标志点的十字架形标定参考物,十字架正反两个表面粘贴有环形的编码标志点和圆形的非编码标志点.然后,在现场用工业摄影测量系统XJTUDP重建出双面标定十字架的精确结构尺寸数据;将标定十字架在公共视场范围内依次摆出多个姿态,并控制多像机同步拍摄各姿态的图像.最后,为大视场像机选择10参数非线性成像模型,对采集的图像组依次进行标定运算,标定出各像机的内参数和畸变参数,并全局定向出各个像机在统一坐标系下的外方位参数.实验结果表明,该标定方法的重投影误差小于0.05 pixel;利用标定结果测量高精度标准尺长度,相对误差小于1/4 000,可满足大视场多像机视频测量对精度和效率的要求.     

光学传感器星上定标漫射板的特性测量

为了考察星上定标漫射板的光学特性及其在航天环境下的稳定性,对其进行了方向半球反射比(DHR)、双向反射比因子(BRF)、双向反射分布函数(BRDF)等反射特性的测量;同时,进行了系列环境模拟试验.结果显示:星上定标漫射板反射率在可见近红外波段可达0.99,光谱差异＜0.01,在短波红外波段达0.95以上;10～60°BRF变化低于0.1, 0～60°BRDF变化＜0.045,其方向特性与光谱、紫外辐照关系不大;漫射板350 nm反射率在120 h等效紫外辐照下的衰变＜3%,其光学特性受原子氧、质子轰击影响甚微,并通过了航天级力学环境试验.试验研究表明:漫射板具备高反射率、光谱平坦性、朗伯性及其在航天环境下的稳定性,能够满足航天应用要求.     

田口校准系统损失函数的改进及其应用

测量系统的校准周期是计量领域长期研究的问题.实践中测量仪器的校准周期由各生产厂家和研究机构根据具体情况自行规定.田口博士通过建立校准系统损失函数确定了最佳校准周期和最佳调整界限.讨论了田口博士的质量损失函数和校准系统损失函数,在分析了田口校准系统损失函数不足的基础上,给出了相应的改进后的校准系统损失函数,推导出基于改进后的校准系统损失函数的最佳校准周期和最佳调整界限,最后通过实例验证了改进后的校准系统损失函数良好的经济性.     

激光投线仪的多维校准系统

分析了激光投线仪的工作原理及其基准误差的产生原因。基于此,提出了一种新型的激光投线仪校准系统,用于弥补传统校准方式占地面积大、精度值难以量化、人为因素影响较大等缺点。研究了一套采用平行光管角度测量与机器视觉测量结合的检测方法,通过检测激光线的直线度和垂直度来实现仪器的校准。该系统由8个采样管构成数据采集平台,从而达到多维校准的要求。采用VC++与Matlab混合编程的方式编写系统软件,通过调用动态链接库的方式使两种语言相结合。实验测试表明,该系统操作简单,效率高;与传统校准方式相比,其节约了场地长度,整个系统的占用空间控制在8 m³以内;另外,系统提高了校准精度,其水平线和铅垂线平均精度可以达到±0.2 mm/5 m,正交线精度可以达到±23"。     

Development of remote calibration system for pressure standard

A remote calibration technology for disseminating pressure standard has been developed. In the remote calibration, a transfer standard is transported from a calibration laboratory to a client’s site where a calibration item is used. Using the transfer standard and the internet, the calibration item is calibrated on site. For the remote calibration, integrated transfer standards were newly developed in different pressure ranges. Each transfer standard includes a pressure controller, two or three precise pressure transducers, environmental measurement devices and an inclinometer in one box. Also the calibration protocol was examined to perform the remote calibration efficiently using the transfer standard. In order to prove the effectiveness of the remote calibration, the demonstration experiments were performed domestically and internationally. Here, the calibration protocol for the remote calibration and the functional overview of the newly developed transfer standards are described. The experimental results are also shown.     

湿度专家控制系统的设计与实现

针对湿度控制,设计了一套基于新型单片机AVR为主控制芯片,液晶屏为监控显示单元的自动控制系统,通过对湿度受控对象非线性、时滞性等的特性分析,研制基于专家控制的湿度控制算法,取得了良好的效果.实际应用结果表明:系统运行平稳,人机界面友好,算法通用性强,控制精度高,具有一定的推广价值.     

野外大视场双目视觉物体定位监测系统的单参数快速标定

提出了一种只对相机水平偏角进行现场校准的标定方法用于野外远距离、大视场、双目视觉物体定位监测系统的快速标定.该方法通过合理考虑视觉传感器的调平装置,结合现场使用过程中相机焦距值固定的特点,简化了测量模型,减少了待标定参数;只需要测得监测中心和相机在大地坐标系中的经纬度坐标及监测中心的图像坐标即可完成系统标定.由于不需要高精度靶标,从而克服了靶标移动及摆放对标定过程的影响.在实际使用中,对2 km以外400 m×800 m的区域进行监测时,相对定位误差小于0.25％,其中由焦距值误差引起的相对定位误差不超过0.07％.该摄像机标定方法在保证测量精度的同时,具有易实现、用时少等优点,适用于野外大视场环境下物体的快速定位监测.