Kinematic Calibration and Forecast Error Compensation of a 2-DOF Planar Parallel Manipulator

Due to large workspace,heavy-duty and over-constrained mechanism,a small deformation is caused and the precision of the 2-DOF planar parallel manipulator is affected.The kinematic calibration cannot compensate the end-effector errors caused by the small deformation.This paper presents a method combined step kinematic calibration and linear forecast real-time error compensation in order to enhance the precision of a two degree-of-freedom(DOF) planar parallel manipulator of a hybrid machine tool.In the step kinematic calibration phase of the method,the end-effector errors caused by the errors of major constant geometrical parameters is compensated.The step kinematic calibration is based on the minimal linear combinations(MLCs) of the error parameters.All simple and feasible measurements in practice are given,and identification analysis of the set of the MLCs for each measurement is carried out.According to identification analysis results,both measurement costs and observability are considered,and a step calibration including step measurement,step identification and step error compensation is determined.The linear forecast real-time error compensation is used to compensate the end-effector errors caused by other parameters after the step kinematic calibration.Taking the advantages of the step kinematic calibration and the linear forecast real-time error compensation,a method for improving the precision of the 2-DOF planar parallel manipulator is developed.Experiment results show that the proposed method is robust and effective,so that the position errors are kept to the same order of the measurement noise.The presented method is attractive for the 2-DOF planar parallel manipulator and can be also applied to other parallel manipulators with fewer than six DOFs.

QFT control based on zero phase error compensation for flight simulator

To improve the robustness of high-precision servo systems, quantitative feedback theory （QFT） which aims to achieve a desired robust design over a specified region of plant uncertainty is proposed. The robust design problem can be solved using QFT but it fails to guarantee a high precision tracking. This problem is solved by a robust digital QFT control scheme based on zero phase error （ZPE） feed forward compensation. This scheme consists of two parts： a QFT controller in the closed-loop system and a ZPE feed-forward compensator. Digital QFT controller is designed to overcome the uncertainties in the system. Digital ZPE feed forward controller is used to improve the tracking precision. Simulation and real-time examples for flight simulator servo system indicate that this control scheme can guarantee both high robust performance and high position tracking precision.

Self-calibration and Compensation of Setting Errors for Surface Profile Measurement of a Microstructured Roll Workpiece

Microstructured roll workpieces have been widely used as functional components in the precision industries. Current researches on quality control have focused on surface profile measurement of microstructured roll workpieces, and types of measurement systems and measurement methods have been developed. However, low measurement efficiency and low measurement accuracy caused by setting errors are the common disadvantages for surface profile measurement of microstructured roll workpieces. In order to shorten the measurement time and enhance the measurement accuracy, a method for self-calibration and compensation of setting errors is proposed for surface profile measurement of microstructured roll workpieces. A measurement system is constructed for the measurement, in which a precision spindle is employed to rotate the roll workpiece and an air-bearing displacement sensor with a micro-stylus probe is employed to scan the microstructured surface of the roll workpiece. The resolution of the displacement sensor is 0.14 nm and that of the rotary encoder of the spindle was 0.15r~. Geometrical and mathematical models are established for analyzing the influences of the setting errors of the roll workpiece and the displacement sensor with respect to the axis of the spindle, including the eccentric error of the roll workpiece, the offset error of the sensor axis and the zero point error of the sensor output. Measurement experiments are carded out on a roll workpiece on which periodic microstructures are a period of 133 i^m along the circumferential direction. Experimental results demonstrate the feasibility of the self-compensation method. The proposed method can be used to detect and compensate the setting errors without using any additional accurate artifact.

Calibration and compensation methods of installation error of electronic compass

Installation error angle is one of the factors that affect the accuracy of electronic compass used for geomagnetic navigation.To solve this problem,the calibration and compensation methods for installation error angle are studied.By analyzing the generation mechanism of installation error angle of electronic compass,an installation error model is established,compensation formulae are derived,and calibration scheme is proposed.To verify the correctness of the calibration and compensation methods,the verification experiment is conducted by computer simulation.The simulation results show that the proposed calibration and compensation methods are effective and practical.

Research on dynamic error compensation for an armored K type thermocouple

A new method was proposed, in which a high-power CO2 laser modulated by high frequency was used as the driv- ing source to heat up a surface-temperature sensor. The continual beam and the pulsed beam sent out by the same laser could be used in the same system to carry on the static calibration of the radiation thermometer and the dynamic calibration of the temperature sensor to be checked. The frequency-response characteristics of high-speed radiation thermometer surpassed that of the temperature sensor, therefore it could be used as the reference value to calibrate the latter and let system error be cor- rected. Differences in the environment of the sensor installing and the error caused by the change of thermo-physical proper- ty could be avoided. Thus, the difficult problem of traceable dynamic calibration of temperature was solved. In experiment, to obtain the frequency characteristics of the thermocouple and the dynamic performance of the K type thermocouple, which could compensate the dynamic characteristics of the sensor, the sensor was dynamically corrected by using the method, and then the mathematical model was established.

Novel camera calibration method based on invariance of collinear points and pole-polar constraint

To address the eccentric error of circular marks in camera calibration,a circle location method based on the invariance of collinear points and pole–polar constraint is proposed in this paper.Firstly,the centers of the ellipses are extracted,and the real concentric circle center projection equation is established by exploiting the cross ratio invariance of the collinear points.Subsequently,since the infinite lines passing through the centers of the marks are parallel,the other center projection coordinates are expressed as the solution problem of linear equations.The problem of projection deviation caused by using the center of the ellipse as the real circle center projection is addressed,and the results are utilized as the true image points to achieve the high precision camera calibration.As demonstrated by the simulations and practical experiments,the proposed method performs a better location and calibration performance by achieving the actual center projection of circular marks.The relevant results confirm the precision and robustness of the proposed approach.

System for Measuring Elevator Guide Rail Quality and Its Calibration

A system for measuring the quality parameters of elevator guide rails is developed. The quality parameters the system can measure include straightness, flatness, squareness, width and height of the rail. The system consists of six parts：main guideway, auxiliary guideway, reference rail, saddle, control casing and measured rail. The guide rail to be measured is mounted on a bed. The straightness errors of surfaces are checked by five linear displacement sensors mounted on the saddle. The deviation of readings from the sensor, which is in contact with top guiding surface, gives the straightness error of the surface and height of the rail. The other four sensors are used to measure side guiding surfaces respectively and give other parameters including flatness on the surfaces, squareness, width and height of the rail. A novel calibration method is also developed to calibrate the straightness motion error of the system in horizontal and vertical directions. The deflection deformation of the measured rail is fitted by using a fourth-order polynomial. Experimental results show that the uncertainty of the system on the side surfaces after compensating the straightness motion error is less than 0. 01 mm, and the uncertainty of the system on the top surface after compensating the straightness motion error and the deflection deformation of the rail is less than 0. 03 mm.

Robot Calibration Using Active Vision-based Measurement

This paper presents an efficient robot calibration method with non-contact vision metrology. Using the coplanar pattern to calibrate camera made the active-vision-based end-effector pose measurement be a feasible and costeffective way. Kinematic parameter errors were linearized and identified through two-step procedure, thus the singular and non-linear condition was overcome. These errors were then compensated using inverse model method. The whole calibration process is flexible, easy to implement and prevents the error propagation from the earlier stages to the later ones. Calibration was performed on MOTOMAN SV3industrial robot. Experiment results show that the proposed method is easy to setup and with satisfactory accuracy.

光学陀螺旋转调制惯导系统及关键技术发展

面向长航时、高精度的自主导航技术需求,系统梳理光学陀螺旋转调制惯导系统的发展历程及关键技术现状具有重要的现实意义。首先,基于惯导系统误差特性,阐述了旋转调制技术的基本原理。其次,系统回顾和梳理欧美等西方国家旋转惯导系统发展历程,分析了系统发展演变后的技术逻辑,总结了我国旋转惯导系统的研制现状。最后,立足于提高系统自主导航精度,从旋转策略优化、误差标校、初始对准3个方面分析了旋转惯导系统需解决的关键技术及研究现状。在总结光学陀螺旋转调制惯导系统及关键技术发展基础上,针对后续旋转惯导系统研究提出了几点思考,为高精度自主导航技术研究提供参考。

陀螺加速度计交叉耦合误差参数标定及补偿方法

针对陀螺加速度计非线性输出值表达式中横向加速度耦合误差未解耦的问题,综合考虑了陀螺加速度计在时变输入加速度和横向加速度同时作用时对输出的影响,利用基座3个正交方向的加速度,将外框架轴与转子轴不垂直度角作为已知量,计算得到陀螺加速度计的理论输出值。在此基础上,采用递推迭代方法对模型进行参数标定,同时,给出了陀螺加速度计输出值补偿模型。通过对比参数补偿前后的误差结果,输入加速度误差由0.05g减小到0.002g,验证了输出模型中交叉耦合误差的补偿对提高测量精度的有效性。

基于PE-ANGO的MIMU现场标定方法

针对当前微惯性测量单元(MIMU)的现场标定方法存在标定步骤复杂、不利于非专业人员操作等问题,提出了一种基于先验知识增强的自适应北苍鹰优化(PE-ANGO)算法的MIMU现场标定方法。首先分析了MIMU涉及的误差并建立了加速度计和陀螺仪的目标函数,然后使用PE-ANGO算法求解目标函数并得到最优参数。为了使得标定工作易于现场操作,引入了一种用于传感器数据采集的手持MIMU来验证所提算法。仿真结果表明:PE-ANGO算法的标定精度相较于北苍鹰优化算法提高了一个数量级。实测实验表明:标定前后对俯仰角和横滚角累积误差的抑制效果分别提高了约89%和87%;与传统标定方法相比,对俯仰角和横滚角累积误差的抑制效果分别提高了71%和68%,验证了所提方法的有效性。

复杂曲面机器人磨抛技术研究现状与趋势展望综述

在航空、能源、交通、军工等国家战略领域中,针对复杂曲面零件的自动化、高质量和高效率磨抛需求,对近年来国内外工业机器人磨抛加工关键技术及集成系统的研究和应用进展进行了综述。首先,从复杂曲面机器人磨抛机理及工艺优化、磨抛运动轨迹规划、磨削力控制等方面总结了复杂曲面机器人磨抛技术的研究成果;然后,介绍了国内外机器人磨抛集成系统应用现状;最后,分析了复杂曲面机器人磨抛技术的主要问题以及发展趋势,为该技术的发展提供了重要的指导和方向。研究结果表明:当前该技术存在的主要问题包括磨抛机理不够清晰,数学模型不够准确,复杂曲面机器人磨抛轨迹规划效率不高,磨抛力的控制仍不够精准等;另外,磨抛工艺参数优化、机器人力位混合控制、机器人高精度标定与误差补偿、基于数字孪生的机器人磨抛在线监控、机器人磨抛细分应用场景等方面的研究和实践将极大地推动机器人磨抛技术的发展和应用。

井下工具倾斜姿态误差的非线性融合补偿

准确的井下钻探姿态测量精度取决于惯性测量单元(IMU)误差的校正,基于简化误差模型的椭球+平面拟合后,井斜角和工具面角的系统性误差仍需补偿,重力场翻转测试和Monto-Carlo模拟还说明姿态误差存在非线性变化。基于倾斜翻转辨识校正残差和参数寻优,并进一步提出等角距均衡校正技术;进行典型姿态下的数据测量,分别采用椭球+平面拟合、多点翻转优化和等角距均衡技术进行误差补偿。实验结果表明,提出的翻转优化和均衡技术可有效降低非线性姿态误差,标定后近垂直姿态井斜角误差从±0.1°降低至±0.000 8°(1σ),工具面角误差从±1°降低至±0.016 8°(1σ)。

机器人三维视觉实验平台坐标系标定实验设计

为了探究机器人工作站的高精度坐标系标定方法,搭建了一个由工业机器人、双目结构光相机以及单轴转台组成的机器人三维视觉实验平台。研究了定位误差补偿方法、工业机器人工具中心点标定方法、工业机器人与双目结构光相机的手眼标定方法以及双目结构光相机与单轴转台的坐标系标定方法,并形成了实验平台的坐标系综合标定方法,最后测试了标定后的综合精度。实验结果表明,工业机器人与双目结构光相机之间的平均标定误差为0.442~0.689 mm,机器人三维视觉实验平台的综合标定误差为0.399~0.696 mm,能完全满足焊接、涂胶、切割等机器人离线编程应用的精度要求。

基于位形相似性聚类的机器人参数标定研究

利用非几何参数误差引起的定位误差与机器人位形之间的相似性映射关系,通过聚类算法将机器人参数标定位形空间划分为多个子空间,并在各个子空间中完成参数标定;利用相似性关系将待补偿位形归类到对应的子空间,根据子空间的参数标定结果控制机器人运动,实现非几何参数误差引起的定位误差的有效补偿。以UR5机器人为标定对象进行试验,与普通标定补偿方法相比,采用所提方法标定补偿后的位置误差模的最大值和平均值分别减小了60.24%和66.62%。

基于极限学习机的并联机器人无模型误差补偿算法研究

针对工业并联机器人精度性能限制其在精密装配等高端制造领域应用的问题,文中以六自由度Stewart并联机器人为研究对象,提出了一种基于极限学习机的无模型误差补偿算法,旨在有效提升六自由度Stewart并联机器人的位姿精度。首先,建立六自由度Stewart并联机器人坐标系框架。其次,提出基于极限学习机的无模型误差补偿算法,并通过实验分析确定了极限学习机的网络框架以及隐藏层神经元个数。实验结果表明,基于极限学习机的无模型误差补偿算法将六自由度Stewart并联机器人的最大位置和姿态误差分别有效降低了90.96%和97.01%,精度提升效果优于传统的BP神经网络和CSBP神经网络。

基于仿生优化神经网络的6DOF工业机械手标定

针对六自由度工业机械手标定中的定位精度问题,提出一种基于仿生优化神经网络的机械手标定方法。研究六自由度工业机械手的运动学模型,并给出其D-H参数。通过将关节挠度模型和传统的运动学模型标定技术相结合,来同步识别机械手的运动学参数和柔度参数,以提高定位精度。然后,构造人工神经网络对未建模误差进行进一步补偿,如摩擦、机械传动误差和热膨胀。此外,采用入侵杂草优化算法对神经网络的权值和偏置进行优化。最后,采用六自由度机械手HX300对所提方法进行了实际测试,验证其可行性。研究结果表明:标定后机械手的定位精度得到了显著提高,平均误差、最大误差和标准差分别为0.345、0.6374、0.1624 mm,均小于其他标定方法;与GA-BP神经网络标定方法相比,所提方法具有更好的收敛能力,平均误差降低了15.92%,适用于高精度的各种工业应用。

输入参数优化的机器人手眼标定改进方法

由于相机位姿误差以及机器人运动解算误差导致标定结果具有较大误差,为了提升机器人定位与抓取的精度,提出了一种具有误差补偿和图像校正的手眼标定方法.基于对偶四元数理论来描述螺旋运动,用奇异值分解法求解手眼变换矩阵.再通过对非线性相机成像模型进行研究后最小化相机的重投影误差,得到优化后的相机外参,同时根据机器人运动学模型对机器人运动误差做补偿.最后搭建机器人单目视觉实验平台,将该方法与对偶四元数法和Tasi两步法进行对比分析,实验结果表明,该方法在XYZ三个方向上的坐标误差均值为0.46,标准差为0.25.在标定精度和稳定性上均优于其他两种方法,具有一定的理论实践意义.

晶圆校准器误差补偿与拟合算法的研究

晶圆校准器作为半导体生产、检测中的重要设备,其圆心定位的精度容易受检测误差的影响,因此针对误差的补偿算法是提高晶圆校准精度的关键技术。针对检测误差中晶圆承载面倾斜影响采样精度问题,建立了晶圆倾斜后在水平面椭圆投影的物理模型,推导椭圆与晶圆圆心的解析关系,并采用相应的椭圆方程进行拟合。为了进一步提高补偿及拟合精度,提出了一种引入遗忘因子的扩展卡尔曼滤波的椭圆拟合算法,该算法采用密度聚类法及改进样本点分布的渐进一致采样进行数据预处理,并利用迭代重加权最小二乘法进行椭圆拟合,最终实现圆心的精确拟合。实验证明,在使用提出的方法进行误差补偿后,拟合精度达到99.95%,验证了其有效性。

基于自适应滤波的TIADC校准技术研究

针对失调失配、增益失配和采样时间失配这三种失配,对TIADC的校准方法进行探究.依据已有的两通道TIADC低通滤波校准方法,将其扩展到了4通道,依据提出的拓展思路,可以将此方法拓展到更高的通道.另外,为了实现对频率的判别,提出了一种新的频率判别方法,可有效实现频率范围的判别.校准方法经仿真证明,在采样率为2 GHz的4通道TIADC中,使用不同的输入频率进行验证,经校准后,无杂散动态范围提升均在40 dB以上,校准效果明显.相对于目前的校准算法,该算法复杂度低,结构简单.