室内照明统一眩光值(UGR)校准装置的研制

统一眩光值UGR是表征室内照明眩光程度高低和视觉舒适度的重要参数,在室内照明检测和照明设计中有着广泛应用。目前国内对于眩光测试仪的溯源方法一般只采用光亮度标准装置校准亮度值,而对于照明光源的亮度分布和几何位置信息都没有进行相关校准,造成眩光测量结果的失准和不统一。针对此问题,本文研制了一套统一眩光值UGR校准装置,介绍了装置原理和结构,并对其不确定度进行分析。该装置的研制对于保障眩光测量结果的准确统一,有效提升照明设计质量,保护视觉健康有着重要作用。     

Improved error performance for generalised spatial modulation with enhanced spectral efficiency

The existing analytical average bit error rate (ABER) expression of conventional generalised spatial modulation (CGSM) does not agree well with the Monte Carlo simulation results in the low signal‐to‐noise ratio (SNR) region. Hence, the first contribution of this paper is to derive a new and easy way to evaluate analytical ABER expression that improves the validation of the simulation results at low SNRs. Secondly, a novel system termed CGSM with enhanced spectral efficiency (CGSM‐ESE) is presented. This system is realised by applying a rotation angle to one of the two active transmit antennas. As a result, the overall spectral efficiency is increased by 1 bit/s/Hz when compared with the equivalent CGSM system. In order to validate the simulation results of CGSM‐ESE, the third contribution is to derive an analytical ABER expression. Finally, to improve the ABER performance of CGSM‐ESE, three link adaptation algorithms are developed. By assuming full knowledge of the channel at the receiver, the proposed algorithms select a subset of channel gain vector (CGV) pairs based on the Euclidean distance between all CGV pairs, CGV splitting, CGV amplitudes, or a combination of these.     

基于离心机的低气压精密控制研究

针对惯性器件全量程气压灵敏度校准难题,发明了一种可抗高离心加速度的气压箱结构,并研制了离心-气压复合校准装置,实现了大g值条件下惯性器件气压特性的校准。本装置设计了两种工作模式:离心机静止时,利用真空泵、高精度压力传感器等气压精密测控系统实现离心-气压复合校准装置的精密控压;离心机工作时,通过密封技术等实现离心-气压复合校准装置保压。本装置通过对安装在离心机上的试验箱内气压进行精密控制,将高线加速度与气压环境有机结合在一起,为加速度计提供可靠的加速度、气压复合计量校准环境。实验结果验证了所设计的气压箱结构可以实现气压范围1~100 kPa,气压偏差优于10 Pa的精密控制。     

Study of equivalent efficiency calibration method for radioactive gas source measured on HPGe detectors

ABSTRACT

In view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance of 25 cm, was fitted by measuring solid planar sources with known activity. To verify the accuracy of the efficiency curve, ⁴¹Ar, ¹³³Xe and ⁸⁷Kr gases were produced and determined by length-compensated method. Then, their full-energy-peak efficiencies at 25 cm position away from the detector were directly calibrated. The percentage efficiency deviations between interpolation from the efficiency curve and direct calibration are all less than 2.5%, which proves the accuracy of the equivalent method. This calibration method is a general one and can be also used for some other radioactive sample measurements, such as non-destructive analysis of gaseous fission product samples with a suitable source-to-detector distance.     

基于普吕克直线的多线结构光视觉传感器标定方法

针对多线结构光系统的快速标定,提出了一种基于普吕克直线的标定方法。传统的线结构光标定方法大多以单点的形式进行提取和坐标系转换,从而获得平面方程。然而单点数量较多会导致操作复杂,不适用于多线结构光的标定。为了解决这个问题,提出了一种新的标定方法,该方法在标定过程中全部采用普吕克矩阵的形式,而不是直接使用点特征。该方法有利于在摄像机坐标系下快速准确地获得光平面方程。同时设计了一种与该方法相对应的用于标定多线结构光的平面标定靶标。为了将一般直线转换为普吕克直线,将图像平面维度延展,定义了一个新的图像空间。为了对普吕克直线的坐标系进行转换,重新表达了基于普吕克直线的透视投影模型。基于普吕克空间中直线与平面的性质,对多条结构光线的普吕克矩阵进行合并即可高效地构造出线性的矩阵方程,从而进一步拟合出结构光平面方程。实验验证了所提方法并证明了校准精度的显著提高,当测试距离为1.8 m时,测量得到的三维点的RMS误差在0.08 mm之内。     

Models for circular data from time series spectra

Circular data are those for which the natural support is the unit circle and its toroidal extensions. Numerous constructions have been proposed which can be used to generate models for such data. We propose a new, very general, one based on the normalization of the spectra of complex-valued stationary processes. As illustrations of the new construction's application, we study models for univariate circular data obtained from the spectra of autoregressive moving average models and relate them to existing models in the literature. We also propose and investigate multivariate circular models obtained from the high-order spectra of stationary stochastic processes generated using linear filtering with an autoregressive moving average response function. A new family of distributions for a Markov process on the circle is also introduced. Results for asymptotically optimal inference for dependent observations on the circle are presented which provide a new paradigm for inference with circular models. The application of one of the new families of spectra-generated models is illustrated in an analysis of wind direction data.     

Non-kinematic calibration of a six-axis serial robot using planar constraints

This paper describes a non-kinematic calibration method developed to improve the accuracy of a six-axis serial robot, in a specific target workspace, using planar constraints. Simulation confirms that the stiffness of the robot, as well as its kinematic parameters, can be identified. An experimental validation shows that the robot's accuracy inside the target workspace is significantly enhanced by reducing the maximum distance errors from 1.321 mm to 0.274 mm. The experimental data are collected using a precision touch probe, which is mounted on the flange of a FANUC LR Mate 200iC industrial robot, and a high precision 9-in. granite cube. The calibration method makes use of a linear optimization model based on the closed-loop calibration approach using multi-planar constraints. A practical validation approach designed to reliably evaluate the robot's accuracy after calibration is also proposed.     

A case-deletion diagnostic for penalized calibration estimators and BLUP under linear mixed models in survey sampling

The penalized calibration technique in survey sampling combines usual calibration and soft calibration by introducing a penalty term. Certain relevant estimates in survey sampling can be considered as penalized calibration estimates obtained as particular cases from an optimization problem with a common basic structure. In this framework, a case deletion diagnostic is proposed for a class of penalized calibration estimators including both design-based and model-based estimators. The diagnostic compares finite population parameter estimates and can be calculated from quantities related to the full data set. The resulting diagnostic is a function of the residual and leverage, as other diagnostics in regression models, and of the calibration weight, a singular feature in survey sampling. Moreover, a particular case, which includes the basic unit level model for small area estimation, is considered. Both a real and an artificial example are included to illustrate the diagnostic proposed. The results obtained clearly show that the proposed diagnostic depends on the calibration and soft-calibration variables, on the penalization term, as well as on the parameter to estimate.     

Pseudospectral method for assessing stability robustness for linear time-periodic delayed dynamical systems

The article presents a pseudospectral approach to assess the stability robustness of linear time-periodic delay systems, where periodic functions potentially present discontinuities and the delays may also periodically vary in time. The considered systems are subject to linear real-valued time-periodic uncertainties affecting the coefficient matrices, and the presented method is able to fully exploit structure and potential interdependencies among the uncertainties. The assessment of robustness relies on the computation of the pseudospectral radius of the monodromy operator, namely, the largest Floquet multiplier that the system can attain within a given range of perturbations. Instrumental to the adopted novel approach, a solver for the computation of Floquet multipliers is introduced, which results into the solution of a generalized eigenvalue problem which is linear w.r.t. (samples of) the original system matrices. We provide numerical simulations for popular applications modeled by time-periodic delay systems, such as the inverted pendulum subject to an act-and-wait controller, a single-degree-of-freedom milling model and a turning operation with spindle speed variation.     

多分量力组合加载校准装置主机结构的技术实现

主要介绍了可实现六个分量力和力矩独立或组合加载的校准装置主机结构的设计思路和具体组成。针对该装置量程宽、空间大、准确度高等特点,文章分析了装置研制过程中涉及的技术难点;围绕多分量力组合加载的实现问题,说明了多分量力组合加载的方法原理设计及加载装置主机的机械结构设计等技术问题;最后说明了校准装置实现的技术性能和试验验证情况。