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Fully coupled time-domain simulation of dynamic positioning semi-submersible platform using dynamic surface control

A fully coupled 6-degree-of-freedom nonlinear dynamic model is presented to analyze the dynamic response of a semi-submersible platform which is equipped with the dynamic positioning （DP） system. In the control force design, a dynamic model of reference linear drift frequency in the horizontal plane is introduced. The dynamic surface control （DSC） is used to design a control strategy for the DP. Compared with the traditional back-stepping methods, the dynamic surface control combined with radial basis function （RBF） neural networks （NNs） can avoid differentiating intermediate variables repeatedly in every design step due to the introduction of a first order filter. Low frequency motions obtained from total motions by a low pass filter are chosen to be the inputs for the RBF NNs which are used to approximate the low frequency wave force. Considering the propellers’ wear and tear, the effect of filtering frequencies for the control force is discussed. Based on power consumptions and positioning requirements, the NN cen-ters are determined. Moreover, the RBF NNs used to approximate the total wave force are built to monitor the disturbances. With the DP assistance, the results of fully coupled dynamic response simulations are given to illustrate the effectiveness of the proposed con-trol strategy.     

引入强跟踪滤波器的 IMM 算法在导航定位解算中的应用

针对单一模型对城市机动载体运动状态估计不足的问题,本文在标准交互式多模型算法的基础上引入强跟踪滤波器,并以“当前”模型和“CV”模型作为基础模型进行交互式模型滤波。利用信号源仿真动态数据分析对比了利用单一模型算法、标准交互式多模型算法和引入强跟踪滤波器的交互式多模型算法的定位解算性能。实验结果表明：本文提出的基于强跟踪滤波器的交互式多模型算法相比于“当前”模型滤波和标准IM M 算法径向误差方差分别从19.11和16.78降低到13.24．     

基于 TEQC 的 GPS 观测数据质量分析

介绍了TEQC在GPS测量数据预处理中的基本功能,包括：格式转换、数据编辑和质量检核,结合实例对T EQC在GPS数据质量检核中的应用进行了分析,并将其结果可视化,最后,利用TEQC计算了伪距单点定位的结果,并与已公布的ITRF2005值进行了比较。     

Improvement of the semi-Lagrangian advection scheme in the GRAPES model: Theoretical analysis and idealized tests

ABSTRACT The Global/Regional Assimilation and PrEdiction System （GRAPES） is the newgeneration numerical weather predic- tion （NWP） system developed by the China Meteorological Administration. It is a fully compressible non-hydrostatical global/regional unified model that uses a traditional semi-Lagrangian advection scheme with cubic Lagrangian interpola tion （referred to as the SL_CL scheme）. The SL_CL scheme has been used in many operational NWP models, but there are still some deficiencies, such as the damping effects due to the interpolation and the relatively low accuracy. Based on Reich＇s semi-Lagrangian advection scheme （referred to as the R2007 scheme）, the Re_R2007 scheme that uses the low- and high-order B-spline function for interpolation at the departure point, is developed in this paper. One- and two-dimensional idealized tests in the rectangular coordinate system with uniform grid cells were conducted to compare the Re..R2007 scheme and the SL_CL scheme. The numerical results showed that： （1） the damping effects were remarkably reduced with the Re_R2007 scheme; and （2） the normalized errors of the Re_R2007 scheme were about 7.5 and 3 times smaller than those of the SL_CL scheme in one- and two-dimensional tests, respectively, indicating the higher accuracy of the Re..R2007 scheme. Furthermore, two solid-body rotation tests were conducted in the latitude-longitude spherical coordinate system with non uniform grid cells, which also verified the Re_R2007 scheme＇s advantages. Finally, in comparison with other global advection schemes, the Re_R2007 scheme was competitive in terms of accuracy and flow independence. An encouraging possibility for the application of the Re_R2007 scheme to the GRAPES model is provided.     

高精度时空信息崩滑坡灾害监测技术

我国部分地区地质灾害爆发频率高,多年来崩滑坡、泥石流等高危险性地质灾害严重威胁我国人民财产与生命安全。因此,地质灾害及时预警一直是我国在应急方面亟待解决的难题。随着北斗、GPS等全球卫星导航系统的建设组网,GNSS技术逐渐成为当前提供时空位置信息的重要手段,具有数据实时性、设备低功耗、搭建便捷化等特性,成为解决地质灾害监测与预警的理想技术手段。本文利用BDS+GPS+GLONASS时空信息数据,构建了面向地质灾害监测的中长基线毫米级精度的崩滑坡监测解算方法,确定了双差观测的载波相位解算模型。最后在重庆新浦区域展开试验应用,实现了基于高精度时空信息的毫米级滑坡灾害的监测与预警。为预计该区域的地质灾害提供了数据支持,为人民的生产生活提供了技术保障。     

基于ICESat-2 ATLAS数据的DEM高程精度评价

为探究ASTER GDEMV3、SRTM1 DEM和AW3D30 DEM 3种开源DEM数据的高程精度,本文以高精度ICESat-2 ATLAS测高数据为参考数据,利用GIS统计分析、误差相关分析及数理统计对DEM的高程精度进行对比评价。结果表明：①AW3D30的质量最稳定;SRTM1 DEM在平原精度最高;在高原山地精度由高到低依次为AW3D30 DEM、ASTER GDEMV3、SRTM1 DEM。②DEM数据高程精度受地表覆盖影响较大,且与地形因素密切相关,在相同地表覆盖的两个研究区中DEM数据高程精度表现情况不一致,SRTM在平原地表覆盖下精度表现最好,平均误差为3.15 m,AW3D30 DEM在山地地表覆盖下精度表现最好,平均误差为7.61 m。③坡度对DEM数据的高程精度影响较大,在两个研究区3种DEM数据的高程误差均随坡度的增加而增加;坡向对DEM数据的高程精度影响较小,未发现明显的规律。     

高精度CORS站像控点自动提取方法

CORS站持续稳定运行产生了海量高精度定位点数据,如何挖掘提取高精度可用像控点,以替代部分像控点人工选择或外业测绘工作,具有重要推广价值。本文提出了一种基于高精度CORS定位数据的像控点自动提取方法,并研发了像控点自动提取工具。首先采用Douglas-Peucker算法实现轨迹简化;然后利用ST-DBSCAN提取聚类中心;最后进一步栅格化,优化提取得到高可用像控点集。试验结果表明,像控点提取结果的准确率在94%以上,大大减少了像控点采集的工作量,重复利用高精度像控点信息具有广阔应用前景。