Approximate optimal tracking control for near-surface AUVs with wave disturbances

This paper considers the optimal trajectory tracking control problem for near-surface autonomous underwater vehicles (AUVs) in the presence of wave disturbances. An approximate optimal tracking control (AOTC) approach is proposed. Firstly, a six-degrees-of-freedom (six-DOF) AUV model with its body-fixed coordinate system is decoupled and simplified and then a nonlinear control model of AUVs in the vertical plane is given. Also, an exosystem model of wave disturbances is constructed based on Hirom approximation formula. Secondly, the time-parameterized desired trajectory which is tracked by the AUV’s system is represented by the exosystem. Then, the coupled two-point boundary value (TPBV) problem of optimal tracking control for AUVs is derived from the theory of quadratic optimal control. By using a recently developed successive approximation approach to construct sequences, the coupled TPBV problem is transformed into a problem of solving two decoupled linear differential sequences of state vectors and adjoint vectors. By iteratively solving the two equation sequences, the AOTC law is obtained, which consists of a nonlinear optimal feedback item, an expected output tracking item, a feedforward disturbances rejection item, and a nonlinear compensatory term. Furthermore, a wave disturbances observer model is designed in order to solve the physically realizable problem. Simulation is carried out by using the Remote Environmental Unit (REMUS) AUV model to demonstrate the effectiveness of the proposed algorithm.     

927一期工程测图成果质量检验软件的设计与实现

简要阐述了927一期测图成果质量检验软件的总体设计思想和技术构架等情况,给出了软件研发的技术路线,对比了软件功能需求与研发实现间的关系,总体上对该软件进行了介绍。该软件已在927项目任务承担单位中得到广泛应用,并为做好国家重大测绘工程项目的质量控制提供了借鉴。     

基于图分割的可变比例尺地图分幅回溯算法

总结了地图分幅需遵循的原则,并针对地图集中可变比例尺的分幅,将其定义为基于约束条件的图分割问题,用最小生成树(minimum spanning tree,MST)将制图区域关联起来,基于回溯算法对MST裁剪实现地图集的分幅。实验结果表明,所提出的方法能较好顾及地图集分幅的相关原则,满足地图集制作的要求。同时,利用该方法设计的地图集分幅工具已成功应用于《武汉市汉阳地区地名图集》等的制作,有效提高了地图设计人员的工作效率。     

国外脆弱性理论模型与评估框架研究评述

目前,脆弱性研究作为一种新的研究范式已经在多学科领域中得到了广泛应用,并取得了丰硕成果.但随着研究的深入,学者们发现,由于学科背景及研究视角的差异性,不同研究领域之间存在着结论不兼容和工作重复等问题,迫切需要一个可行的理论模型与评估框架来整合其理论和实践的研究.在对脆弱性概念内涵的发展演变过程分析的基础上,对国外多学科领域中的脆弱性理论模型及评估框架进行了对比研究和评述.研究发现:脆弱性概念的泛化是制约通用脆弱性理论模型与评估框架的关键因素,结合未来脆弱性研究的发展方向,对整合的脆弱性理论模型与评估框架提出了4个方面的要求,即多时空尺度特征、多重扰动特征、耦合系统特征和人文特征.     

Visualization and damage assessment for flooded area

A practical method for visualizing flood area and evaluating damage is presented, which consists of two technical approaches: self-programming and adapting commercial GIS platforms. The low-cost and easy-to-use GIS-Based model developed by self-programming can meet current requirements of most local authorities, especially in developing countries. In this model, two cases, non-source flood and source flood, are distinguished and the Seed-spread algorithm suitable for source-flood is discussed; The flood damage is assessed by overlaying the flood area range with thematic maps and other related social and economic data. and all the-matic maps are converted to raster format before overlay analysis. Two measures are taken to improve the operation efficiency of speed seed-spread algorithm. The accuracy of the model mainly depends on the resolution and precision of the DEM data, and the accuracy of registering all raster layers and the quality of attribute data.     

激光照排机输出控制系统设计

简析了激光照排机工作原理,提出了激光照排机输出控制接口的设计方法,重点论述了计算机与激光照排机之间数据缓冲、数据传送、数据分离、信号转换的基本设计思想和实现方法。     

细纱机数据采集与处理系统

论述了细纱机数据采集与处理系统的设计思想与实现方法。     

Robust估计的算法优化

本文分析了Ｒｏｂｕｓｔ估计收敛慢的原因，提出以最小二乘平差的残差（Ｖ）为初始信息，用Ｌ１估计的权函数所计算的权力初始权，根据迭代计算的残差的大小，及残差的变化所提供的信息，构造出加速收敛的算法，计算结果表明，较之一般的方法，迭代次数显著减少，辨识杠杆点含粗差的能力有较大提高，即搜索粗差的效率有很大提高。     

Satellite image analysis using crowdsourcing data for collaborative mapping: current and opportunities

ABSTRACT

Researchers are continually finding new applications of satellite images because of the growing number of high-resolution images with wide spatial coverage. However, the cost of these images is sometimes high, and their temporal resolution is relatively coarse. Crowdsourcing is an increasingly common source of data that takes advantage of local stakeholder knowledge and that provides a higher frequency of data. The complementarity of these two data sources suggests there is great potential for mutually beneficial integration. Unfortunately, there are still important gaps in crowdsourced satellite image analysis by means of crowdsourcing in areas such as land cover classification and emergency management. In this paper, we summarize recent efforts, and discuss the challenges and prospects of satellite image analysis for geospatial applications using crowdsourcing. Crowdsourcing can be used to improve satellite image analysis and satellite images can be used to organize crowdsourced efforts for collaborative mapping.     

遥感图像在土地利用更新中的应用研究——以里下河地区防汛信息系统(LXFPGIS)为例

以里下河地区防汛信息系统为例 ,阐述了利用 TM遥感图像进行 GIS土地利用更新的试验研究。采用了最大似然分类法和模糊分类法两种监督分类方法进行分类试验。提出了两种提高训练区采样效率的基于 GIS本底数据的采样方法 ,即半人工采样方法和全自动分类区直方图提取法。对上述方法分别做了土地利用分类试验 ,对分类结果进行了分析比较 ,并作出了相应的结论。