基于混合优化算法的关节臂式测量机参数标定

为进一步提高关节臂式坐标测量机等高机动性精密测量设备的测量精度,使用D-H矩阵法建立其关节坐标转换数学模型并据此推导出参数误差模型.针对非线性多参数标定问题,通过变换分析消除了最小二乘法求解时矩阵中的冗余参数,降低了计算的复杂性.设定判定准则并实现最小二乘法和模拟退火算法的混合,提出了一种基于混合优化算法的参数标定方法,解决了LM算法的初值设定和SA算法的搜索效率逐步降低的问题.实验结果表明:关节臂式测量机参数经混合优化算法标定后,参数的误差范围有了显著的缩小,单点重复性误差的平均值减小了1.746 mm,长度误差的平均值减小了0.941 mm,测量误差得到了进一步的抑制.     

Forecasting in long horizons using smoothed direct forecast

This paper constructs a forecast method that obtains long‐horizon forecasts with improved performance through modification of the direct forecast approach. Direct forecasts are more robust to model misspecification compared to iterated forecasts, which makes them preferable in long horizons. However, direct forecast estimates tend to have jagged shapes across horizons. Our forecast method aims to “smooth out” erratic estimates across horizons while maintaining the robust aspect of direct forecasts through ridge regression, which is a restricted regression on the first differences of regression coefficients. The forecasts are compared to the conventional iterated and direct forecasts in two empirical applications: real oil prices and US macroeconomic series. In both applications, our method shows improvement over direct forecasts.     

Coincidence and reproducibility in the EHT black hole experiment

This paper discusses some philosophical aspects related to the recent publication of the experimental results of the 2017 black hole experiment, namely the first image of the supermassive black hole at the center of galaxy M87. In this paper I present a philosophical analysis of the 2017 Event Horizon Telescope (EHT) black hole experiment. I first present Hacking's philosophy of experimentation. Hacking gives his taxonomy of elements of laboratory science and distinguishes a list of elements. I show that the EHT experiment conforms to major elements from Hacking's list. I then describe with the help of Galison's Philosophy of the Shadow how the EHT Collaboration created the famous black hole image. Galison outlines three stages for the reconstruction of the black hole image: Socio-Epistemology, Mechanical Objectivity, after which there is an additional Socio-Epistemology stage. I subsequently present my own interpretation of the reconstruction of the black hole image and I discuss model fitting to data. I suggest that the main method used by the EHT Collaboration to assure trust in the results of the EHT experiment is what philosophers call the Argument from Coincidence. I show that using this method for the above purpose is problematic. I present two versions of the Argument from Coincidence: Hacking's Coincidence and Cartwright's Reproducibility by which I analyse the EHT experiment. The same estimation of the mass of the black hole is reproduced in four different procedures. The EHT Collaboration concludes: the value we have converged upon is robust. I analyse the mass measurements of the black hole with the help of Cartwright's notion of robustness. I show that the EHT Collaboration construe Coincidence/Reproducibility as Technological Agnosticism and I contrast this interpretation with van Fraassen's scientific agnosticism.     

基于三正交消影点的摄像机标定方法及实验

利用2个非平行的长方体作为标定模版,采用Hough变换检测出图像中长方体的棱,然后计算出2组三正交方向上的消影点,再根据消影点与摄像机内参数的约束方程求出摄像机内参数.该方法原理简单,只需要一幅图像就可实现摄像机内参数的求解.实验结果表明,该方法有较高的精度和稳定性.     

FAST工程馈源舱Stewart平台的机构精度标定

FAST工程采用柔索悬吊方案,利用六根支撑索拖动30t重的馈源舱在百米尺度空间内运动,并将馈源瞬时定位于毫米级精度位置。因此,馈源舱的主要执行机构-Stewart平台必须克服制造误差、刚度变形、测量误差以及外界扰动耦合的影响,实现馈源的定位精度要求。本文分析了Stewart平台的结构、机构、工作原理及误差来源,针对前期的精度标定提出了测量及误差补偿方案,研究内容对于FAST工程大科学目标的顺利实现具有重要的指导意义。     

基于模型预测的无人机组合陀螺在线标定

为解决无人机长时间航行时,由于环境等因素的变化,导致陀螺漂移、标度因数误差和陀螺安装轴不正交误差的问题,借助天文导航系统(CNS:Celestial Navigation System)提供的高精度姿态信息,基于四元数误差建立陀螺在线标定误差模型,提出一种基于模型预测的捷联惯性导航系统(SINS:Strap Down Inertial Navigation System)/CNS组合陀螺在线标定混合滤波方法.仿真结果表明,该方法能够很好地适用于在线标定,不仅满足标定精度要求,而且降低了滤波的计算量,提高了滤波的数值稳定性.     

A New Algorithm for the Establishing Data Association Between a Camera and a 2-D LIDAR

In this paper,we propose a new algorithm to establish the data association between a camera and a 2-D Light Detection And Ranging sensor （LIDAR）.In contrast to the previous works,where data association is established by calibrating the intrinsic parameters of the camera and the extrinsic parameters of the camera and the LIDAR,we formulate the map between laser points and pixels as a 2-D homography.The line-point correspondence is employed to construct geometric constraint on the homography matrix.This enables checkerboard to be not essential and any object with straight boundary can be an effective target.The calculation of the 2-D homography matrix consists of a linear least-squares solution of a homogeneous system followed by a nonlinear minimization of the geometric error in the image plane.Since the measurement quality impacts on the accuracy of the result,we investigate the equivalent constraint and show that placing the calibration target nearby the 2-D LIDAR will provide sufficient constraints to calculate the 2-D homography matrix.Simulation and experimental results validate that the proposed algorithm is robust and accurate.Compared with the previous works,which require two calibration processes and special calibration targets such as checkerboard,our method is more flexible and easier to perform.     

倾斜储油罐的变位识别与罐容表标定

本文使用分析的方法研究了倾斜储油罐的变位识别与罐容表标定问题,精确地给出了油位高度与储油量之间的关系式.     

Receding horizon H∞ control for discrete-time Markovian jump linear systems

Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality (LMI) form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.     

水银体温计基准刻度自动标定方法研究

为了克服体温计生产中由毛细管直径及水银玻璃包的容积存在一定误差所造成的各体温计刻度的不一致性,及基准刻度标定困难的问题,研究和开发了基准刻度动态标定方法和装置,设计了自动标定生产线。该生产线由控制系统、恒温加热装置、图像识别系统、随行夹具、输送装置、自动标定刻线装置等组成。该装置可自动刻画出每个体温计上各不相同的两条基准线,为后续分号工序提供了可靠依据。生产实践表明,该方法和装置能有效减少生产误差,提高产品质量。