Constructing a Virtual Large Reference Plate with High-precision for Calibrating Cameras with Large FOV

It is well known that the accuracy of camera calibration is constrained by the size of the reference plate,it is difficult to fabricate large reference plates with high precision.Therefore,it is non-trivial to calibrate a camera with large field of view(FOV).In this paper,a method is proposed to construct a virtual large reference plate with high precision.Firstly,a high precision datum plane is constructed with a laser interferometer and one-dimensional air guideway,and then the reference plate is positioned at different locations and orientations in the FOV of the camera.The feature points of reference plate are projected to the datum plane to obtain a virtual large reference plate with high-precision.The camera is moved to several positions to get different virtual reference plates,and the camera is calibrated with the virtual reference plates.The experimental results show that the mean re-projection error of the camera calibrated with the proposed method is 0.062 pixels.The length of a scale bar with standard length of 959.778mm was measured with a vision system composed of two calibrated cameras,and the length measurement error is 0.389mm.

Calibration Scheme Under Spherical Coordinates for Magnetic Tracker Used in VR System

A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, spe cified in spherical coordinates, is generated first, which is then used to calibrate the tracking results by a two dimensional interpolation. The scheme can effectively correct the static errors in the magnetic tracking system. The employment of spherical coordinates significantly reduces the calculation complexity in calibration.

A Robust Estimation Method for Camera Calibration with Known Rotation

Imagine that hundreds of video streams, taken by mobile phones during a rock concert, are uploaded to a server. One attractive application of such prominent dataset is to allow a user to create his own video with a deliberately chosen but virtual camera trajectory. In this paper we present algorithms for the main sub-tasks (spatial calibration, image interpolation) related to this problem. Calibration: Spatial calibration of individual video streams is one of the most basic tasks related to creating such a video. At its core, this requires to estimate the pairwise relative geometry of images taken by different cameras. It is also known as the relative pose problem [1], and is fundamental to many computer vision algorithms. In practice, efficiency and robustness are of highest relevance for big data applications such as the ones addressed in the EU-FET_SME project SceneNet. In this paper, we present an improved algorithm that exploits additional data from inertial sensors, such as accelerometer, magnetometer or gyroscopes, which by now are available in most mobile phones. Experimental results on synthetic and real data demonstrate the accuracy and efficiency of our algorithm. Interpolation: Given the calibrated cameras, we present a second algorithm that generates novel synthetic images along a predefined specific camera trajectory. Each frame is produced from two “neighboring” video streams that are selected from the data base. The interpolation algorithm is then based on the point cloud reconstructed in the spatial calibration phase and iteratively projects triangular patches from the existing images into the new view. We present convincing images synthesized with the proposed algorithm.

基于直驱并联机构的六自由度振动校准系统研究

直驱并联机构六自由度振动校准系统可以实现高精度和多自由度的运动模拟和校准,具有良好的应用前景。为了解决平台驱动关节滑块位置跟踪精度低的问题,对该机构进行动力学力矩前馈补偿分析。利用虚功原理建立该机构动力学模型,提出一种基本伺服算法与动力学前馈补偿相结合的控制策略。在实验样机上进行力矩前馈补偿,实验结果表明,在开放伺服程序增加力矩前馈补偿后,可以降低该机构在运动时的跟随误差,进行不同幅值单自由度正弦运动时,跟随误差分别下降40.32%、39.04%、43.24%、48.19%。并对振动台进行了性能检测,在平台基础上,搭建激光测量系统和数据采集模块,进行传感器校准和性能分析,平台横向振动比较小,谐波失真度均小于2%,平台具有较好的稳定性和性能。

一种基于虚拟仪器技术的视频分析仪校准装置

针对视频分析仪校准中主要标准器停产以及校准过程繁琐的问题,基于虚拟仪器技术,在LabVIEW开发环境下,利用M4i.6622-x8任意波形发生卡作为信号发生模块,开发了一种视频分析仪校准装置。实现了视频分析仪基本参数和失真参数的校准,给出了亮度电平、色度电平、色度相位等视频基本参数和行倾斜、k_(p)系数(2T脉冲k系数)、色度-亮度增益差、色度-亮度时延差、亮度非线性失真等视频失真参数的校准信号产生过程。经过实验,技术指标可达到如下:亮度电平为±0.2%,色度电平为±0.2%,色度相位为±0.1°,行倾斜为±0.1%,k_(p)系数为±0.1%,色度-亮度增益差为±0.2%,色度-亮度时延差为±3 ns,亮度非线性失真为±0.2%;优于TG2000可编程视频信号发生器,满足视频分析仪校准要求。

物理引擎技术在土木工程中的应用研究综述

随着土木工程仿真需求的不断提升,传统仿真工具在计算效率和实时交互等方面的能力逐渐无法满足工程要求。物理引擎凭借其强大的非线性、大变形、高效计算能力和灵活性,日益受到研究者关注,成为了土木工程新兴应用研究热点。首先,介绍物理引擎技术概念及原理,系统梳理物理引擎技术在土木工程细分专业中的研究前沿和重点问题;其次,基于现有研究的局限性,提出制约物理引擎应用的计算效率和可靠性两大难题;然后,为了推动物理引擎技术的应用研究发展,提出从硬件、算法、策略角度提升计算效率,从模型改进、多场耦合、参数校准角度提升可靠性的物理引擎应用方法;最后,提出了物理引擎技术在未来土木工程中的重点研究方向和发展建议,对工程应用研究具有参考意义。

基于数字孪生的机器人工件感知与虚实映射标定方法研究

机器人采用离线编程的方法,仿真环境与真实环境空间上相互独立、时间上相互隔离,被加工工件逆向重构过程繁琐且存在形状、定位误差。为此,提出了以机器人操作系统(ROS)为基础构建数字孪生机器人的建模方法,实现了工件从真实环境到虚拟环境的感知重构。研究了数字孪生虚实交互映射的特点,提出了基于数字孪生原理的虚实映射标定方法,修正了真实物理环境与虚拟仿真环境间的工件误差。最后,针对抓取机器人数字孪生系统,进行了抓取工件的案例测试,验证了该方法的有效性。

光波导输入的双通道同步定标虚拟成像相位阵列光谱仪

激光频率梳定标的虚拟成像相位阵列光谱仪有潜力同时实现超高光谱分辨率与波长定标精度,对于天文光谱探测有重要意义。然而,现有的研究工作中,虚拟成像相位阵列光谱仪采用常规的双通道光纤输入模式,在受环境干扰时,两个通道的同步性较差,相对漂移严重,从而降低了光谱仪的重复性定标精度。为解决该问题,提出一种以光波导作为输入器件的双通道虚拟成像相位阵列光谱仪,利用波导通道之间相对稳定的特性,实现更高水平的同步定标精度。通过对不同环境下光谱仪的稳定性进行研究得出,在相似的测试条件下,波导输入的虚拟成像相位阵列光谱仪的重复性定标精度明显优于光纤输入时的定标表现。

Kinematic calibration method with high measurement efficiency and robust identification for hybrid machine tools

Geometric error is the main factor affecting the machining accuracy of hybrid machine tools.Kinematic calibration is an effective way to improve the geometric accuracy of hybrid machine tools.The necessity to measure both position and orientation at each pose,as well as the instability of identification in case of incomplete measurements,severely affects the application of traditional calibration methods.In this study,a kinematic calibration method with high measurement efficiency and robust identification is proposed to improve the kinematic accuracy of a five-axis hybrid machine tool.First,the configuration is introduced,and an error model is derived.Further,by investigating the mechanism error characteristics,a measurement scheme that only requires tool centre point position error measurement and one alignment operation is proposed.Subsequently,by analysing the effects of unmeasured degrees of freedom(DOFs)on other DOFs,an improved nonlinear least squares method based on virtual measurement values is proposed to achieve stable parameter identification in case of incomplete measurement,without introducing additional parameters.Finally,the proposed calibration method is verified through simulations and experiments.The proposed method can efficiently accomplish the kinematic calibration of the hybrid machine tool.The accuracy of the hybrid machine tool is significantly improved after calibration,satisfying actual aerospace machining requirements.

Validation of virtual sensor-assisted Bayesian inference-based in-situ sensor calibration strategy for building HVAC systems

For building heating,ventilation and air-conditioning systems(HVACs),sensor faults significantly affect the operation and control.Sensors with accurate and reliable measurements are critical for ensuring the precise indoor thermal demand.Owing to its high calibration accuracy and in-situ effectiveness,a virtual sensor(VS)-assisted Bayesian inference(VS-BI)sensor calibration strategy has been applied for HVACs.However,the application feasibility of this strategy for wider ranges of different sensor types(within-control-loop and out-of-control-loop)with various sensor bias fault amplitudes,and influencing factors that affect the practical in-situ calibration performance are still remained to be explored.Hence,to further validate its in-situ calibration performance and analyze the influencing factors,this study applied the VS-BI strategy in a HVAC system including a chiller plant with air handle unit(AHU)terminal.Three target sensors including air supply(SAT),chilled water supply(CHS)and cooling water return(CWR)temperatures are investigated using introduced sensor bias faults with eight different amplitudes of[−2℃,+2℃]with a 0.5℃ interval.Calibration performance is evaluated by considering three influencing factors:(1)performance of different data-driven VSs,(2)the influence of prior standard deviationsσon in-situ sensor calibration and(3)the influence of data quality on in-situ sensor calibration from the perspective of energy conservation and data volumes.After comparison,a long short term memory(LSTM)is adopted for VS construction with determination coefficient R-squared of 0.984.Results indicate thatσhas almost no impact on calibration accuracy of CHS but scanty impact on that of SAT and CWR.The potential of using a prior standard deviationσto improve the calibration accuracy is limited,only 8.61%on average.For system within-control-loop sensors like SAT and CHS,VS-BI obtains relatively high in-situ sensor calibration accuracy if the data quality is relatively high.

基于虚拟标定技术的换挡规律标定方法研究

基于虚拟标定技术进行了自动变速器换挡规律仿真研究,首先建立高精度物理模型(包括发动机、变速器及整车主要零部件等),利用已知的变速器控制单元(TCU)控制策略搭建变速器控制模型或直接在虚拟仿真平台接入TCU控制器,利用硬件在环(HiL)仿真平台进行TCU标定及相关工况仿真测试,并将仿真结果与试验数据进行对比,结果表明,基于模型的虚拟标定技术可满足换挡规律标定精度要求,并有效缩短标定时间、提升标定质量。

一种参考源修正的短波辐射源时差定位方法

为解决短波辐射源到达时间差(time difference of arrival,TDOA)定位(简称时差定位)方法受电离层影响导致的定位精度下降的问题,提出了一种利用参考源修正的短波辐射源目标时差定位方法。针对地球表面短波辐射源,基于电离层球面反射模型的电离层反射虚高近似方法,建立了利用参考修正的短波目标时差定位模型。考虑参考源与目标共用电离层反射区域对电离层虚高的影响,将各电离层反射点的距离相关性引入电离层虚高的协方差矩阵中,实现了目标定位精度的修正。通过推导和仿真所提模型的克拉美·罗下界,分析了参考源修正目标定位精度的可行性。进一步给出基于Armijo直线搜索Newton法的最大似然估计方法,通过仿真数据验证了所提算法的有效性,实现了良好的定位效果。

校准水流量计在线比对测试技术研究

水流量计在测试过程中通常采用一表一侧的单一性现场测试方式,存在检测效率低下、现场校验精确性不高等问题。因此,为实现其在线校验和远程监控,本文提出一种基于虚拟仪器技术的移动式水流量计在线校准系统,并进行实验验证。试验表明:该系统可将校准精度提高至96%,且稳定性提高了23%,可为后续研究奠定技术基础。

基于模态测试的斜交简支梁桥建造质量快速评估

以实际工程中的一座新建公路斜交宽简支梁桥为例,探究模态测试技术和模态刚度测试方法在新建桥梁工程验收评价中的应用。设计虚拟静载试验方案,选取参与计算的最少模态阶数;进行环境激励桥梁模态测试试验,识别桥梁前三阶实测模态参数,基于实测模态参数识别结构柔度矩阵,预测虚拟静载试验的实测模态挠度,对比桥梁的设计理论挠度,结合相关规范评估建造状况。结果表明:虚拟静载试验荷载作用下,仅采用前3阶模态参数即可准确预测简支梁桥的跨中模态挠度,中载和偏载工况下的误差均在5%以下;环境激励模态测试试验可以准确识别斜交宽简支梁前3阶模态参数,无需对桥梁施加额外激励措施;结合规范计算的桥梁跨中挠度校验系数在0.55~0.70之间,表明该简支梁桥建造状况良好;基于模态测试,可以准确评估简支梁桥建造质量,测试过程方便快捷,在实际工程中具有广阔的应用前景。

面向空间机械臂遥操作的虚拟相机成像技术

对于采用虚拟图形预测仿真克服天地不确定大时延的地面遥操作,为使任务专家准确监视、预测并遥控空间机械臂的运动,本文研究了Open Inventor软件开发包中虚拟相机的成像技术。分析了真实相机与虚拟相机的成像原理,推导了虚拟相机的透视投影和视口变换矩阵。依据二者的成像原理,对真实相机和虚拟相机的成像进行了一致性分析,并展开定量及定性验证。研究表明:基于Open Inventor开发包搭建的中国空间站及空间机械臂的仿真系统,可对空间机械臂的末端及肘部相机进行虚拟成像并准确模拟真实成像,为空间机械臂通过地面遥操作安全精准地完成在轨任务奠定了基础。

基于LabVIEW的电表改装与校准虚拟仿真实验的开发

虚拟仿真实验是现代实验教学的一个重要手段,它与真实实验可以紧密结合、相互补充.基于LabVIEW开发的电表改装与校准虚拟仿真实验由替代法测电流表的内阻、改装为大量程电流表、改装电压表、改装欧姆表4个实验组成,通过人机交互界面的设计、数值仿真程序设计,使学生获得与真实实验操作一致的学习体验,依据合理评价指标形成的算法规则还对学生的实验过程进行智能化的评价.该虚拟仿真实验突破了传统实验室的时空限制,极大地提高了学生物理实验的学习兴趣,促进学生动手实践.

柴油机尿素选择性催化还原系统虚拟标定及NO_(x)转化率优化方法研究

基于尿素选择性催化还原系统物理模型与尿素喷射量控制模型联合仿真的虚拟标定方法,获得了目标NO_(x)转化率脉谱;采用多目标遗传算法对尿素选择性催化还原系统进行优化,得到最优尿素喷射量目标值,同时优化了NO_(x)转化率和NH3泄漏值。分析了原排参数及优化结果对NO_(x)转化率的影响。仿真结果表明,采用优化后的尿素喷射量可实现较高的NO_(x)转化率,在排温200~300℃的条件下NO_(x)转化率平均提高35%左右,同时满足国六排放法规对NH3泄漏限值的要求。

中央肋对接平尾结构非对称载荷测量技术

针对中央肋对接平尾结构,使用直接测量法和提出的唯象拟合法对其非对称弯矩载荷进行测量。通过先后开展虚拟试验和地面载荷校准试验,分别建立了两种测量方法的非对称载荷模型,并对其适用性和准确性进行研究。地面试验和飞行试验结果显示,唯象拟合法能够有效地完成平尾结构的非对称载荷测量,地面试验验模误差最大值为1.57%;直接测量法由于中央对称面附近连接有对接肋和平尾接头等导致局部传力比较复杂,测量精度较差,地面试验验模误差达到8.11%。

基于LabVIEW的数字式密度继电器智能校验系统设计

数字式密度继电器的灭弧性能和绝缘性能优异,是供电安全保障的关键部分。为了解决当前数字式密度继电器校验误差的问题,设计了基于LabVIEW的数字式密度继电器智能校验系统。系统硬件包括工控机、温控装置、传感器、气压调节模块。其中,工控机由过程输入/输出(I/O)通道、I/O设备构成。温控装置实现温度偏差与波动数值的调控。传感器包括压力和温度传感器。气体压力调控机构由驱动机构、特制气缸等构成。采用LabVIEW设计系统校验软件。校验时采用相位差算法进行信号相位差计算。测试了系统的功能与性能。测试结果表明,该系统能够实现数字式密度继电器闭锁功能与报警功能的校验,压力示值和温度补偿误差均较低,具有重要的实际应用价值。

混合动力专用变速器虚拟标定技术研究

为缩短混合动力专用变速器(DHT)的标定周期,搭建硬件在环(HIL)仿真平台完成了DHT的电控参数虚拟标定。将获得的标定数据与实车常规标定数据进行比较,结果表明,虚拟标定方法获得的标定数据与常规标定方法获得的数据接近,可有效缩短整车开发周期。