Extended Range(10–30 Days) Heavy Rain Forecasting Study Based on a Nonlinear Cross-Prediction Error Model

Extended range （10-30 d） heavy rain forecasting is difficult but performs an important function in disaster prevention and mitigation. In this paper, a nonlinear cross prediction error （NCPE） algorithm that combines nonlinear dynamics and statistical methods is proposed. The method is based on phase space reconstruction of chaotic single-variable time series of precipitable water and is tested in 100 global cases of heavy rain. First, nonlinear relative dynamic error for local attractor pairs is calculated at different stages of the heavy rain process, after which the local change characteristics of the attractors are analyzed. Second, the eigen-peak is defined as a prediction indicator based on an error threshold of about 1.5, and is then used to analyze the forecasting validity period. The results reveal that the prediction indicator features regarded as eigenpeaks for heavy rain extreme weather are all reflected consistently, without failure, based on the NCPE model; the prediction validity periods for 1-2 d, 3-9 d and 10-30 d are 4, 22 and 74 cases, respectively, without false alarm or omission. The NCPE model developed allows accurate forecasting of heavy rain over an extended range of 10-30 d and has the potential to be used to explore the mechanisms involved in the development of heavy rain according to a segmentation scale. This novel method provides new insights into extended range forecasting and atmospheric predictability, and also allows the creation of multi-variable chaotic extreme weather prediction models based on high spatiotemporal resolution data.

A NEW METHOD FOR PREDICTING TROPOSPHERIC RANGE ERROR

Based on the quasi-measured values of tropospheric refraction,the relation betweenand △R as expressed in Eq.(3)is proved,and according to the stable feature of refractivityat 9 km above sea level,a simplified method for predicting tropospheric range error is analysed.Some new parameters for linear regression analysis of tropospheric range error are given also.

THE SPECIFIC CHARACTER OF LIMIT ERRORS IN CLOSE RANGE PHOTOGRAMMETRY

Close_range photogrammetry is to determine the shape and size of the object,instead of it’s absolute position.Therefore,at first,any translation and rotation of the photogrammetric model of the object caused by whole geodesic,photographic and photogrammetric procedures in close_range photogrammetry could not be considered.However,it is necessary to analyze all the reasons which cause the deformations of the shape and size and to present their corresponding theories and equations.This situation,of course,is very different from the conventional topophotogrammetry.In this paper some specific characters of limit errors in close_range photogrammerty are presented in detail,including limit errors for calibration of interior elements for close_range cameras,the limit errors of relative and absolute orientations in close_range photogrammetric procedures,and the limit errors of control works in close_range photogrammetry.A theoretical equation of calibration accuracy for close_range camerais given.Relating to the three examples in this paper,their theoretical accuracy requirement of interior elements of camera change in the scope of ±(0.005～0.350) mm.This discussion permits us to reduce accuracy requirement in calibration for an object with small relief,but the camera platform is located in violent vibration environment.Another theoretical equation of relative RMS of base lines ( m S/S ) and the equation RMS of start direction are also presented.It is proved that the m S/S could be equal to the relative RMS of m Δ X / Δ X .It is also proved that the permitting RMS of start direction is much bigger than the traditionally used one.Some useful equations of limit errors in close_range photogrammetry are presented as well.Suggestions mentioned above are perhaps beneficial for increasing efficiency,for reducing production cost.

Dynamic range and linearity improvement for zero-field single-beam atomic magnetometer

Zero-field single-beam atomic magnetometers with transverse parametric modulation for ultra-weak magnetic field detection have attracted widespread attention recently.In this study,we present a comprehensive response model and propose a modification method of conventional first harmonic response by introducing the second harmonic correction.The proposed modification method gives improvement in dynamic range and reduction of linearity error.Additionally,our modification method shows suppression of response instability caused by optical intensity and frequency fluctuations.An atomic magnetometer with single-beam configuration is built to compare the performance between our proposed method and the conventional method.The results indicate that our method’s magnetic field response signal achieves a 5-fold expansion of dynamic range from 2 nT to 10 nT,with the linearity error decreased from 5%to 1%.Under the fluctuations of 5%for optical intensity and±15 GHz detuning of frequency,the proposed modification method maintains intensityrelated instability less than 1%and frequency-related instability less than 8%while the conventional method suffers 15%and 38%,respectively.Our method is promising for future high-sensitive and long-term stable optically pumped atomic sensors.

Robust detector for range-spread targets in non-Gaussian background

Based on the target scatterer density, the range-spread target detection of high-resolution radar is addressed in additive non-Gaussian clutter, which is modeled as a spherically invariant random vector. Firstly, for sparse scatterer density, the detection of target scatterer in each range cell is derived, and then an M/K detector is proposed to detect the whole range-spread target. Se- condly, an integrating detector is devised to detect a range-spread target with dense scatterer density. Finally, to make the best of the advantages of M/K detector and integrating detector, a robust detector based on scatterer density （DBSD） is designed, which can reduce the probable collapsing loss or quantization error ef- fectively. Moreover, the density decision factor of DBSD is also determined. The formula of the false alarm probability is derived for DBSD. It is proved that the DBSD ensures a constant false alarm rate property. Furthermore, the computational results indi- cate that the DBSD is robust to different clutter one-lag correlations and target scatterer densities. It is also shown that the DBSD out- performs the existing scatterer-density-dependent detector.

Novel reference range selection method in InISAR imaging

Aiming at the reference range selection for different antennas in interferometric inverse synthetic aperture radar （InlSAR） systems, this paper proposes a respective focusing （RF） method. The reference ranges for echoes of different antennas are selected respectively for RF, which is different from the traditional uniform focusing （UF） with the same reference range applied to all the antennas. First, a comparison between UF and RF for InlSAR signal model considering the ranging error is given. Compared with RF, UF has an advantage in overcoming the ranging error differences between different antennas. Then the influence of ranging error upon the interferometric imaging with RF is investigated particularly, and it is found that the ranging error differences between different antennas are far smaller than the wavelength, which is advantageous to imaging. By comparing the capabilities of inter- ferometric imaging between RF and UF, it is concluded that RF is a better choice in conquering problems such as image mismatching and phase ambiguity even with ranging errors. Simulations demonstrate the validity of the proposed method.

Ranging Error Correction Based on a Prior Error Model

Wireless technology provides accurate positioning in indoor environments using time of arrival(TOA) based ranging techniques. However, the positioning accuracy is degraded due to the ranging errors caused by multipath and non-line-of-sight(NLOS) propagation. In this paper, a ranging error correction method is proposed to improve positioning performance. A TOA ranging error model(TREM) is built to provide the prior information for ranging error correction first. The mean value of TREM within a certain interval is used as the ranging error correction value(RECV). As the RECV may be unreasonable sometimes, we adjust it according to the actual positioning situation and then exploit the final RECV to correct ranging data. The experimental results show that the proposed method could well reduce ranging errors and the positioning performance is obviously improved when using corrected ranging data.

A novel wide-range precision instrument for measuring three-dimensional surface topography

We developed a measuring instrument that had wide range, high precision, small measuring touch force. The instrument for three-dimensional (3D) surface topography measurement was composed of a high precision displacement sensor based on the Michelson interference principle, a 3D platform based on vertical scanning, a measuring and control circuit, and an industrial control computer. It was a closed loop control system, which changed the traditional moving stylus scanning style into a moving platform scanning style. When the workpiece was measured, the lever of the displacement sensor returned to the balanced position in every sample interval according to the zero offset of the displacement sensor. The non-linear error caused by the rotation of the lever was, therefore, very small even if the measuring range was wide. The instrument can measure the roughness and the profile size of a curved surface.

基于Romax的新能源汽车减速器齿轮修形研究

以某增程式新能源汽车减速器系统为研究对象,Romax为研究平台。结合齿轮的微观修形理论,以传递误差、面载、齿根应力和接触应力作为优化目标,结合第二代遗传算法提出了一种以齿向鼓形量、齿向斜度、渐开线鼓形量、渐开线斜度综合修形的全新修形方法。通过对优化前后各目标参数的分析对比,得出修形后减小了传递误差、齿根应力等、改善了面载、应力偏载等问题,同时齿轮的传动性能得到了明显提升,其研究方法可更好地指导企业生产实践。

北斗系统GEO卫星伪距多路径误差改正

北斗系统地球静止轨道(GEO)卫星因相对于地面近似静止,其多路径误差相对于其他类型较为严重,且表现出系统波动现象。为提升定位精度,本文在GEO卫星伪距多路径误差特征研究的基础上,采用奇异谱分析方法对其进行修正,并通过伪距单点定位(SPP)验证伪距多路径误差修正效果。选取测站CUT0连续10d的静态观测数据进行修正试验。研究发现,GEO卫星伪距多路径误差序列表现出较强的天重复性,且多路径误差中的系统误差项越大,重复性也越强;在运用奇异谱分析方法修正GEO卫星伪距多路径误差各系统误差项后,多路径组合(MP)观测值和SPP的定位精度均有一定程度提升。

大动态范围磁通门磁力仪及其在定向误差校正中的应用

仪器定向误差会影响地磁矢量观测数据的准确性,现有的校正方法需要已知地磁场模量或参考标准仪器,且难以应用在井下和海洋等无法手动安装调整仪器的情况。本文提出了大动态磁通门磁力仪和在此基础上的欧拉旋转变换的矢量校正方法。该方法可在无需参考标准仪器的情况下,获得磁通门的定向角度误差并进行自校正测量。在地磁观测台站进行了实验,结果表明,当实验仪器定向误差分别设置为4个不同象限区间的大角度时,校正后与台站比测仪器对应分量的相关系数仍达到0.99以上,B-A图中置信区间长度减小了86%以上,RMS误差降低至15%以下,论证了该校正方法的有效性,能够提高地磁台站的观测数据质量,并为井下和海洋地磁观测的定向提供参考解决方案。

基于5G信号异步时钟误差补偿的多无人机协同定位方法

5G信号可为多无人机(UAV)提供精确的相对测距/测角信息,进而提升其在卫星接收机故障时的协同定位精度。然而,协同网络中各节点的5G通讯时钟往往是异步的,这会对测距/测角信息的精度产生较大影响,进而降低融合性能。针对上述问题,提出了一种基于5G信号异步时钟误差补偿的多无人机协同定位方法。首先,构建了基于5G信号异步时钟误差的相对测距模型,并利用相对测距/测角信息以及高度计信息建立了从机的位置观测方程。在此基础上,通过设计迭代扩展卡尔曼滤波器(IEKF)实现了对从机惯导系统(INS)误差以及异步时钟误差的联合最优估计,提高了从机定位精度。仿真结果表明,相比于传统方法,所提方法将从机的水平定位精度提高了25.3%。

基于拼接技术的大量程绝对式直线时栅位移传感器自校准方法研究

针对大量程直线位移传感器扩展测量范围和实现绝对定位互相矛盾的问题,在其应用场合缺乏高效安装高精度参考器件的条件,导致难以频繁在线校准以保持其测量精度,基于拼接技术提出一种适用于直线时栅位移传感器的误差延拓自校准新方法。,将复杂的大量程绝对式测量拆分为单段栅尺上的绝对位移测量和栅尺拼接后的绝对位置判断;将绝对位置数据作为位置判断依据并构建双测头结构,实现接缝处感应信号的平滑过渡;利用原生的双测头结构获得定距测量序列,结合误差延拓法构建周期误差函数,再使用快速傅里叶变换获得测量序列幅度谱重构误差函数。为了验证上述方法的可行性和有效性,制作了单段栅尺长度为600 mm的传感器样机进行实验。结果表明,2段栅尺拼接后在量程903 mm内能够实现绝对位置测量;采用自校准方法后传感器单周期内平均误差峰值从2.00μm降至0.59μm,误差补偿效果为70.50%;大量程误差峰值从18.93μm降至0.75μm,误差补偿效果为96.04%;此外,通过校准效果对比实验证明了误差延拓自校准方法优于基于傅里叶谐波补偿的比较校准法,误差校准效果提升约76.20%。

一种复杂环境下UWB测距误差预测方法

针对复杂室内环境中,多径干扰和视距遮挡影响室内定位精度的问题,提出一种复杂环境下UWB测距误差的预测方法:根据超宽带(UWB)室内定位方法抗干扰能力强、定位精度高的特点,从理论上分析影响超宽带信号测距精度的因素;然后通过模型量化分析每种影响因素对测距误差的影响程度,改进以往通过信道脉冲响应特征分析单一的视距遮挡参数来提高定位精度的补偿算法;最后从数据挖掘和机器学习的角度出发,将多径效应、视距遮挡、标签与基站的距离、标签移动速度、标签与基站天线俯仰角以及气象因素(温度、湿度、压强)等对测距精度造成影响的重要因素作为特征进行分类和归类,并使用梯度提升决策树模型对数据集进行训练和预测。实验结果表明,该模型可以根据当前状态下的组合特征值估计出测距误差值,将当前预测的误差值补偿到测量值上,可以有效提高超宽带室内定位的精度。

基于雷达测距的飞行器交会对接误差补偿控制技术

为解决由视线倾角、视线偏角过大造成的飞行器对接存在误差的问题,实现飞行器交会轨迹的精准对接,提出基于雷达测距的飞行器交会对接误差补偿控制技术;建立空间参考坐标系,根据轨道根数计算结果,推导动力学状态方程,实现对飞行器交会对接过程中的动力学作用分析;按照雷达测距原理,计算飞行器的理论飞行时长及雷达装置作用距离,再联合相关参数指标,确定精度极限的取值范围,实现基于雷达测距的对接误差控制;在三坐标测量机结构模型中,定义飞行位姿拟合条件,再根据位姿误差求解结果,实现对误差参数的补偿修正处理,完成基于雷达测距的飞行器交会对接误差补偿控制方法的设计;对比实验结果表明,应用所提方法可以同时将视线倾角、视线偏角的取值控制在0~45.0°的范围之内,能够较好地解决飞行器错误对接的问题,符合精准对接飞行器交会轨迹的实际应用需求。

基于无人机数字近景摄影测量的服役边坡监测方法

针对现有边坡变形监测技术自动化与智能化程度低及安设复杂且对边坡有损坏等问题,提出一种基于无人机数字近景摄影测量的服役边坡坡表变形监测方法。根据数字近景摄影测量的相关理论,确定了数码相机内参数标定和监测点坐标解算方法,研制出一种可布设在服役边坡坡表的数字近景摄影测量和全站仪测量通用的变形监测目标物,实现对边坡的联合监测。研究结果表明,数字近景摄影测量技术配合专门设计的变形监测目标物对边坡坡表变形较为敏感,第一期和第二期的监测点位中误差分别为3.3 mm和1.7 mm,水平位移监测的点位和垂直位移监测的高程中误差分别为3.5 mm和1.6 mm,达到毫米级的监测精度,满足滑坡监测标准的精度要求;同时变形监测目标物制作可靠、成本低廉,具有较高的应用价值。

基于UWB的加权同心圆聚类室内定位方法

为了降低基于超宽带(UWB)测距中的非视距(NLoS)误差的影响,引入了一种基于遗传算法-反向传播神经网络(GA-BP)的UWB测距误差识别与优化方法,能够识别NLoS传播链路下的数据,对NLoS传播链路下测距误差和系统偏差进行校正,最后对测距结果使用卡尔曼滤波(KF)优化。在此基础上,针对测距误差导致的多边定位无交点或多交点问题,提出了一种加权同心圆聚类定位(WCCGT)方法,通过加权同心圆生成(WCCG)解决无交点问题,再采用均值漂移聚类定位方法实现定位解算,以提高定位精度。实验结果表明,改进的测距优化方法有效减小了NLoS传播链路下的测距误差,基于UWB的测距精度提升了60%以上;通过静态定位实验和动态实验分析,将WCCGT方法定位结果与最小二乘(LS)方法进行了比较,本文方法能够在NLoS环境下达到10.78 cm的定位精度,定位性能提升了17.32%。

宽温区热敏电阻温度传感器调理电路

目前热敏电阻温度传感器电路一般采用电阻分压电路,非线性补偿温度范围一般在正温区10~100℃,非线性误差为0.5%;一些特殊应用场合要求热敏电阻测量范围在-45~+125℃。针对热敏电阻温度传感器使用温度范围越宽线性误差越大的问题,提出了一种宽温区热敏电阻温度传感器调理电路,采用精密恒流源激励,减小了热敏电阻温度传感器的自热问题,采用集成对数放大器与集成模拟乘法器进行线性化处理,调理电路具有非线性调节、零位调整、满量程调整3个功能,能够给出精确的标准电压0.1~4.9V信号,对每只热敏电阻温度传感器进行温度标定,根据标定数据进行最小二乘拟合,取得了良好的非线性和精度指标。实验结果表明:测温范围为-45~+125℃,非线性达到0.3%以下,测量误差达到±0.3℃。

改进多尺度结构化融合的红外与可见光图像融合

为解决弱光环境下的红外与可见光图像的融合结果存在对比度低、细节纹理不足、融合耗时长的问题,提出了一种改进多尺度结构化融合的方法。在图像融合前,采用动态范围压缩算法对弱光下的可见光图像进行增强,再通过多尺度结构化分解将增强后的可见光图像和红外图像分解成低频和高频信息;在融合过程中,提出一种基于均方根误差系数的方法对低频信息进行融合,提出一种基于信息熵自适应调整权重的策略对初步融合的高频信息进行二次优化融合,再通过多尺度结构化分解的逆变换重构出融合图像;最后,提出一种基于灰度分类的区域像素增强算法来提高融合后图像的对比度。将提出方法与9种常用的融合方法进行了定性和定量的分析比较,在TNO和CVC-14数据集上的实验结果表明,该方法在平均梯度、交叉熵、边缘强度、标准差和空间频率指标上取得了更好的客观评价结果,整体视觉效果也要优于对比方法。本方法的融合结果具有丰富的细节纹理、较高的清晰度和对比度,且融合耗时短。

顾及周期性变化的大气加权平均温度模型构建

针对大气加权平均温度(T_(m))是地基全球卫星导航系统(GNSS)水汽反演过程中的一个中间变量,其精度会影响地基GNSS水汽反演精度,同时T_(m)表现出较强的地域性差异的现状,研究建立地区的T_(m)模型:利用兰州市榆中探空站气象数据和欧洲中期天气预报中心第五代大气再分析数据集(ERA5)分别建立单因子、顾及年周期变化、顾及年和半年周期变化的T_(m)模型;并对2种气象数据所建的3类模型进行显著性检验和精度验证。结果表明:模型均能通过显著性水平为0.05的显著性检验,同时顾及周期性变化模型的预测值的均方根误差和平均绝对误差均小于贝维斯(Bevis)模型和单因子模型;利用顾及周期变化的模型预测的T_(m)偏差中大于5 K和大于10 K的值占比明显减小且预测残差的周期趋势明显减弱,具有零均值的正态分布特性,仅表现出误差的随机性。总体而言,ERA5气象数据所建模型预测精度高于探空站气象数据所建模型;用ERA5气象数据建立的顾及周期性变化的T_(m)模型可用于兰州市GNSS大气水汽反演。