System error iterative identification for underwater positioning based on spectral clustering

The observation error model of the underwater acous-tic positioning system is an important factor to influence the positioning accuracy of the underwater target.For the position inconsistency error caused by considering the underwater tar-get as a mass point,as well as the observation system error,the traditional error model best estimation trajectory(EMBET)with little observed data and too many parameters can lead to the ill-condition of the parameter model.In this paper,a multi-station fusion system error model based on the optimal polynomial con-straint is constructed,and the corresponding observation sys-tem error identification based on improved spectral clustering is designed.Firstly,the reduced parameter unified modeling for the underwater target position parameters and the system error is achieved through the polynomial optimization.Then a multi-sta-tion non-oriented graph network is established,which can address the problem of the inaccurate identification for the sys-tem errors.Moreover,the similarity matrix of the spectral cluster-ing is improved,and the iterative identification for the system errors based on the improved spectral clustering is proposed.Finally,the comprehensive measured data of long baseline lake test and sea test show that the proposed method can accu-rately identify the system errors,and moreover can improve the positioning accuracy for the underwater target positioning.

Error Analysis on the Positioning Accuracy of a Pneumatic Vibration Isolator

A method of error analysis on the positioning accuracy of a pneumatic vibration isolator was proposed.First,the necessity of positioning accuracy was studied,in addition to the key factors associated with positioning accuracy.These analyses indicated that the positioning accuracy of the pneumatic vibration isolator was mainly attributed to the position error of the push button and the gap between the spindle and valve stem.Second,the error model of the positioning accuracy of the pneumatic vibration isolator was established through geometric simplification and geometric calculation.There are different methods used to calculate the position error of the push button for the different valves.Finally,an example analysis evaluating the impact of a specific two-position three-way valve on the positioning accuracy was given by means of error distribution.Experimental results validated the accuracy of the error model and the example analysis.This error model can be used to guide the structural parameter optimization design according to the requirements for positioning accuracy.

How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated crystal.In this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ^(99m)Tc pencil-beam toward central crystal element was utilized.Beam incident angle was assumed to vary from 0° to 45° in 5° steps.The effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were studied.The influence of photon energy on the crystal identification(CI) was also investigated.Position detection accuracy(PDA) was defined as a factor indicating performance of the crystal.Furthermore,a set of ^(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each configuration.The results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the events.Beyond a crystal-dependent critical angle,the PDA monotonically reduces.The PDA reaches 0.44 for the CsI(Na) at 45° beam angle.The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations.In addition,the PVRs derived from flood images linearly correlate their corresponding PDAs.In conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.

Positioning accuracy of IGPS

The positioning accuracy of a short-haul target-locating system,the inverse-GPS(IGPS) ,was analyzed in detail. The relationship between IGPS and the positioning error was discussed. The multiplicative error minimal bound of the geometric dilution of precision (GDOP) about the four-base-station IGPS was also investigated. In order to clarify the practical implementation of IGPS,the multiplicative and additive error factors which affect the positioning accuracy and theoretical estimation of positioning accuracy were presented. By analyzing the experiments of locating a target's position in virtual three-dimensional areas,the positioning performance of IGPS was illustrated. The results show that the multiplicative and additive error factors should be eliminated in IGPS to improve the positioning accuracy.

Trajectory Control: Directional MWD Inversely New Wellbore Positioning Accuracy Prediction Method

The deviation control of directional drilling is essentially the controlling of two angles of the wellbore actually drilled, namely, the inclination and azimuth. In directional drilling the bit trajectory never coincides exactly with the planned path, which is usually a plane curve with straight, building, holding, and dropping sections in succession. The drilling direction is of course dependant on the direction of the resultant forces acting on the bit and it is quite a tough job to hit the optimum target at the hole bottom as required. The traditional passive methods for correcting the drilling path have not met the demand to improve the techniques of deviation control. A method for combining wellbore surveys to obtain a composite, more accurate well position relies on accepting the position of the well from the most accurate survey instrument used in a given section of the wellbore. The error in each position measurement is the sum of many independent root sources of error effects. The relationship between surveys and other influential factors is considered, along with an analysis of different points of view. The collaborative work describes, establishes a common starting point of wellbore position uncertainty model, definition of what constitutes an error model, mathematics of position uncertainty calculation and an error model for basic directional service.

Comparison of density and positioning accuracy of PS extracted from super-resolution PSI with those from traditional PSI

In the application of persistent scatterer interferometry(PSI),deformation information is extracted from persistent scatterer(PS)points.Thus,the density and position of PS points are critical for PSI.To increase the PS density,a time-series InSAR chain termed as"super-resolution persistent scatterer interferometry"(SR-PSI)is proposed.In this study,we investigate certain important properties of SR-PSI.First,we review the main workflow and dataflow of SR-PSI.It is shown that in the implementation of the Capon algorithm,the diagonal loading(DL)approach should be only used when the condition number of the covariance matrix is sufficiently high to reduce the discontinuities between the joint images.We then discuss the density and positioning accuracy of PS when compared with traditional PSI.The theory and experimental results indicate that SR-PSI can increase the PS density in urban areas.However,it is ineffective for the rural areas,which should be an important consideration for the engineering application of SR-PSI.Furthermore,we validate that the positioning accuracy of PS can be improved by SRPSI via simulations.

Accuracy Analysis of Position Estimation Based on Measurements of Received Signal Strength Difference

The performance of a cellular location system based on received signal strength difference （RSSD） is investigated. In the cellular location system, each mobile station needs to measure the signal strength transmitted by surrounding base stations, and sends its measurements to the service base station. Using the strength difference between the service base station and neighboring base stations, the position of a mobile station is estimated. The related Cramer-Rao lower bound （CRLB） on the location error of this method was derived, and numerical simulations are made to discuss the influences of the number of base stations, correlation coefficient of shadowing attenuation, and cell radius on CRLB. The results show that the CRLB is positively correlated with the standard deviation of shadowing attenuation and cell radius, but negatively correlated with the number of base stations and the correlation coefficient of shadowing attenuation. In addition, the CRLB results obtained in this paper were compared with those of the cellular location system based on received signal strength （RSS） measurements, which reveals that the former is more tight.

An Analysis on Position Estimation, Drifting and Accumulated Error Accuracy during 3D Tracking in Electronic Handheld Devices

This work focuses on a brief discussion of new concepts of using smartphone sensors for 3D painting in virtual or augmented reality. Motivation of this research comes from the idea of using different types of sensors which exist in our smartphones such as accelerometer, gyroscope, magnetometer etc. to track the position for painting in virtual reality, like Google Tilt Brush, but cost effectively. Research studies till date on estimating position and localization and tracking have been thoroughly reviewed to find the appropriate algorithm which will provide accurate result with minimum drift error. Sensor fusion, Inertial Measurement Unit (IMU), MEMS inertial sensor, Kalman filter based global translational localization systems are studied. It is observed, prevailing approaches consist issues such as stability, random bias drift, noisy acceleration output, position estimation error, robustness or accuracy, cost effectiveness etc. Moreover, issues with motions that do not follow laws of physics, bandwidth, restrictive nature of assumptions, scale optimization for large space are noticed as well. Advantages of such smartphone sensor based position estimation approaches include, less memory demand, very fast operation, making them well suited for real time problems and embedded systems. Being independent of the size of the system, they can work effectively for high dimensional systems as well. Through study of these approaches it is observed, extended Kalman filter gives the highest accuracy with reduced requirement of excess hardware during tracking. It renders better and faster result when used in accelerometer sensor. With the aid of various software, error accuracy can be increased further as well.

A Review of Device-Free Indoor Positioning for Home-Based Care of the Aged:Techniques and Technologies

With the development of urbanization,the problem of neurological diseases brought about by population aging has gradually become a social problem of worldwide concern.Aging leads to gradual degeneration of the central nervous system,shrinkage of brain tissue,and decline in physical function in many elderlies,making them susceptible to neurological diseases such as Alzheimer’s disease(AD),stroke,Parkinson’s and major depressive disorder(MDD).Due to the influence of these neurological diseases,the elderly have troubles such as memory loss,inability to move,falling,and getting lost,which seriously affect their quality of life.Tracking and positioning of elderly with neurological diseases and keeping track of their location in real-time are necessary and crucial in order to detect and treat dangerous and unexpected situations in time.Considering that the elderly with neurological diseases forget to wear a positioning device or have mobility problems due to carrying a positioning device,device-free positioning as a passive positioning technology that detects device-free individuals is more suitable than traditional active positioning for the home-based care of the elderly with neurological diseases.This paper provides an extensive and in-depth survey of device-free indoor positioning technology for home-based care and an in-depth analysis of the main features of current positioning systems,as well as the techniques,technologies andmethods they employ,fromthe perspective of the needs of the elderly with neurological conditions.Moreover,evaluation criteria and possible solutions of positioning techniques for the home-based care of the elderly with neurological conditions are proposed.Finally,the opportunities and challenges for the development of indoor positioning technology in 6G mobile networks for home-based care of the elderly with neurological diseases are discussed.This review has provided comprehensive and effective tracking and positioning techniques,technologies and methods for the elderly,by which we can obtain the location information of the elderly in real-time and make home-based care more comfortable and safer for the elderly with neurological diseases.

空间目标天基光学定位方法综述

近年来空间目标定位领域不断结合网络协同、多模融合等探测技术,发展迅速。其中,基于天基光学探测的定位方法以隐蔽性好、测量精度高的独特优势在民用和国防领域应用广泛。为了分析不同情景下适用于不同类型目标的定位方法,针对基于天基光学探测的空间小目标定位进行综述。首先介绍天基光学探测技术的发展、空间目标的分类和特点以及空间目标定位的概念。然后着重分析适用于空间“小、弱”目标的单星和多星定位方法,并对近年提出的异质传感器联合定位展开说明。最后,依据成像过程建立空间目标定位误差分析模型,分析定位精度的影响因素占比并根据现存问题做出总结和展望。

GNSS基准站信噪比联合卫星系统综合定权的手机RTK定位

随着智能手机芯片和天线性能的不断提升,基于手机的高精度定位逐渐引起学术界和工业界的广泛关注.相较于单点定位,实时动态(real-time kinematic,RTK)定位通常表现出更高的定位性能.然而,目前对于手机RTK定位的随机模型的研究仍相对较少.因此,文中以小米8为例,重点探讨了智能手机在多系统RTK定位情境下的随机模型.研究结果表明:不同系统的卫星伪距噪声存在显著差异,而相位噪声的差异则较小.基于此,本文提出了一种基站信噪比联合卫星系统间综合定权的随机模型.相对于传统的信噪比模型更准确地考虑了不同系统之间的权重分配.并在开阔和遮挡条件下进行了静态和动态实验.结果表明:相比于传统的信噪比模型,新模型在静态开阔、静态遮挡、动态开阔和动态遮挡下三维方向的RTK定位精度分别提升了18.7%、18.3%、3.3%和4.6%.

智能手机GNSS数据质量分析与随机模型建立

为提高移动智能终端定位精度,利用小米8和华为Mate20手机采集多个卫星系统的观测数据并进行质量分析,通过不同卫星系统的伪距残差分别对信噪比模型参数进行估计,最后进行静态伪距单点定位实验。结果表明,手机端观测的BDS和GPS伪距精度接近,且高于GLONASS;相较于高度角,伪距残差与信噪比的相关性更强;在信噪比模型参数估计中,小米8拟合效果优于华为Mate20,BDS拟合效果差于其他卫星系统;参数拟合后的信噪比模型在水平和高程方向的定位精度分别为2.37 m和8.38 m,相较于高度角模型,定位精度提升约10%。

应用激光跟踪仪和单目视觉检测三维水模体定位精度方法研究

针对三维水模体检测方法较少、检测过程复杂等问题,提出基于激光跟踪仪和单目视觉的三维水模体定位精度检测方法。激光跟踪仪三维水模体定位精度检测对比实验验证三维水模体在有水和无水的情况下定位精度一致。单目视觉三维水模体定位精度检测实验结果表明:X轴、Y轴、Z轴和空间对角线的定位误差均在0.050 mm以内,重复性分别为0.030 mm,0.064 mm,0.056 mm,0.140 mm,X轴和Y轴的垂直度为0.800 mm,Y轴和Z轴的垂直度为0.761 mm,X轴和Z轴的垂直度为0.503 mm,与激光跟踪仪的测量精度在一个量级。最后,经不确定度分析得到相邻点距离测量误差的标准差为0.0187 mm,满足检测要求。两种方法都能实现非接触测量,简化冗杂的检测过程,可满足医院对医用直线加速器的日常检测需求。

基于Lamb波和改进贝叶斯融合算法的CFRP边缘分层损伤分析

贝叶斯融合法在CFRP上的损伤定位分析结果比较好,但在传感器网络边缘区域会出现比较明显的定位误差。为解决原有算法对传感器网络边缘的分层损伤定位不精确的问题,分析了两种不同损伤因子构成的贝叶斯融合算法在CFRP上的损伤定位效果,验证了以ToF损伤因子形成的贝叶斯融合算法对CFRP损伤定位的可行性,以及贝叶斯融合算法对边缘分层损伤的定位精度;在以损伤因子DI所形成概率成像算法的基础上,以衰减更快的指数权重代替线性权重,将改进的概率成像算法重新代入以贝叶斯为框架的算法中形成一种新的贝叶斯融合算法。结果表明,与现有的融合重构算法相比,改进的融合重构算法至少将损伤定位精度误差减少了58%,定位误差不大于5 mm。

伪目标迭代生成的机器人误差补偿算法

针对机器人误差模型建立后的误差补偿问题,提出一种改进的伪目标迭代算法。该算法用每次迭代中生成新的伪目标来修正关节角,从而不断减小机器人实际误差。完善了伪目标迭代算法流程,提出了5种新的不同的伪目标生成方法,分析了各种方法的特点和适用场景。结合多种伪目标生成方法提出了一种集成算法,进一步提高误差补偿精度。使用HSR-JR612机器人进行仿真实验,仿真结果表明,算法耗时在毫秒级别,补偿效果好,集成算法能进一步提高位姿补偿效果。最后使用UR10机器人与激光跟踪仪进行实验,实验结果表明,补偿后机器人末端位置误差可以减小到0.06 mm以内,姿态误差可以减小到0.025°以内。

基于平面匹配与目标检测的视觉SLAM算法

针对移动机器人同时定位与建图(SLAM)算法在动态复杂、低纹理场景中存在算法精度下降甚至无法正常工作等问题,提出一种基于快速运动目标检测与平面匹配的算法。将视觉特征提取与运动目标检测方法相结合,降低动态目标对定位的干扰;采用平面匹配技术,克服低纹理环境特征缺少问题;同时生成一个稠密的三维点云地图,用于机器人环境解析等应用。该算法在数据集KITTI和TUM上的绝对轨迹误差RMSE指数相对于ORB-SLAM2算法分别降低了66.67%、98.77%,算法运行速率为22.20 fps。结果表明该算法具有良好定位精度、运行效率和鲁棒性。

基于DBO-BP的工业机器人定位误差补偿方法

为提高工业机器人绝对定位精度,提出一种基于DBO-BP与离线前馈校正相结合的方法。该方法适用于工业机器人定位误差补偿研究。通过使用拉丁超立方抽样法获取工业机器人的位姿样本,并利用BP神经网络建立误差预测模型,应用DBO优化算法改善了局部最优现象,从而提高了模型的收敛性和鲁棒性。经过离线前馈补偿处理后,降低了工业机器人定位误差,大幅提高了机器人绝对定位精度。这种方法能够有效提高机器人的精度和稳定性,并为工业机器人的精准定位问题提供了可行的解决方案。

基于射频技术的典型无人机定位算法研究

为提高机场运行的安全性,解决各类“黑飞”现象,以射频定位技术得到的信息数据作为基础,通过相关算法进行计算,得出目标位置,并分析多地面射频侦测站布局对无人机定位精度的影响,确定协同算法的定位精度大于单一定位的精度,基站数量越多定位越精确。

基于UWB偏差平均法和迭代算法吊物跟踪系统研究

吊运货物精准定位是智能仓储和安全管理的根本保障。本文采用UWB(超宽带)定位技术,按照车间构造合理布置信号基站,首先采用偏差平均平面定位算法,初步计算吊物坐标位置;然后用牛顿迭代法,将计算结构进行处理,提高货物定位精度;再利用MATLAB强大的运算能力,实现吊物路径跟踪,并采用数维图数据可视化工具(SovitChart)进行仓库管理平台的开发;最后,对综合算法进行试验验证,定位精度分析结果显示该方法合理有效。