A Cascade Approach for Global Trajectory Tracking Control of Underactuated AUVs     

毕凤阳  魏英杰  张嘉钟  曹伟 《中国海洋工程》2010,24(2):369-380

A global trajectory tracking controller is presented for underactuated AUVs with only surge force and yaw moment in the horizontal plane. A transformation is introduced to represent the tracking error system into a cascade form. The global and uniform asymptotic stabilization problem of the resulting cascade system is reduced to the stabilization problem of two subsystems by use of the cascade approach. For the stabilization of the subsystem involving the yaw moment, a control law is proposed based on the feedback linearization method. Another subsystem is stabilized by designing a fuzzy sliding mode controller which can offer a systematical means of constructing a set of shrinking-span and dilating-span membership functions. In order to demonstrate the practicability of the proposed controller, control constraints, parameter uncertainties, and external disturbances are considered according to practical situation of AUVs. Simulation results show very good tracking performance and robustness of the proposed control schemes.  相似文献   

多尺度地理空间线状目标形状相似性的度量   总被引：3，自引：1，他引：2  

江浩  褚衍东  闫浩文  郭丽峰 《测绘科学》2010,35(5):35-38

本文研究了多尺度地理空间线状目标相似关系的表达与度量问题.基于Douglas-Peucker算法,通过对线状目标形状的分析,从几何学的角度,给出了衡量基本图形中折线与线段之间形状相似度的两个重要参量.按照图形特征,利用分类讨论的方法,建立了多尺度地理空间线状目标形状相似性的计算模型.最后通过实例的计算验证了该度量方法的可行性.  相似文献   

面向过程的时空数据模型研究   总被引：5，自引：0，他引：5  

薛存金  周成虎  苏奋振  董庆  谢炯 《测绘学报》2010,39(1):0-6

根据近20年来时空数据模型的研究现状、存在问题及其原因剖析,以连续渐变地理实体的表达、组织和存储为研究对象,提出面向过程的时空数据模型。根据连续渐变地理实体的内在特性,将其分级抽象为过程对象系列,进一步探讨过程对象及过程对象间逻辑关系,并设计其UML模型结构及物理存储结构。通过抽象的过程对象隐式地记录地理实体动态变化机制,及自定义的过程对象存储表提供演变机制的函数接口模式,实现连续渐变地理实体的过程化组织、存储与动态分析。最后,以海洋数据的过程化组织与分析为例,构建时空过程模型原型系统(海洋过程对象—关系数据库系统与功能分析平台),验证和评价该模型的实用性。  相似文献   

A new model for the vibration isolation via pile rows consisting of infinite number of piles     

Jian‐Fei Lu  Dong‐Sheng Jeng  Jian‐Wei Wan  Ji‐Sheng Zhang 《国际地质力学数值与分析法杂志》2013,37(15):2394-2426

In this study, on the basis of the Floquet transform method, a numerical model for the simulation of the vibration isolation via multiple periodic pile rows with infinite number of piles is established. By means of the fictitious pile method due to Muki and Sternberg, the second kind of Fredholm integral equations for the pile rows are developed by using the fundamental solutions for the half‐space and the compatibility conditions between the piles and half‐space. Employing the Floquet transform method, integral equations for the pile rows in the wavenumber domain are then derived. Solution of the integral equations yields the wavenumber domain solution for the pile rows. The space domain solution can then be retrieved by inversion of the Floquet transform. Numerical results show that the proposed model with the Floquet transform method is in a good agreement with those of the conventional direct superposition method. On the basis of the new model, influences of the spacing between neighboring piles, the Young's modulus of the piles, and the pile length on the vibration isolation effect of the pile rows are investigated. Numerical simulations conducted in this study show that compared with the direct superposition method, the efficiency of the proposed model for simulation of the vibration isolation via pile rows is very high. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A discrete particle representation of hillslope hydrology: hypothesis testing in reproducing a tracer experiment at Gårdsjön,Sweden     

Jessica Davies  Keith Beven  Lars Nyberg  Allan Rodhe 《水文研究》2011,25(23):3602-3612

Despite the long history of the continuum equation approach in hydrology, it is not a necessary approach to the formulation of a physically based representation of hillslope hydrology. The Multiple Interacting Pathways (MIPs) model is a discrete realization that allows hillslope response and transport to be simultaneously explored in a way that reflects the potential occurrence of preferential flows and lengths of pathways. The MIPs model uses random particle tracking methods to represent the flow of water within the subsurface alongside velocity distributions that acknowledge preferential flows and transition probability matrices, which control flow pathways. An initial realization of this model is presented here in application to a tracer experiment carried out in Gårdsjön, Sweden. The model is used as an exploratory tool, testing several hypotheses in relation to this experiment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Lagrangian modeling of water circulation in the Lofoten Basin     

《Dynamics of Atmospheres and Oceans》2021

Lagrangian particle tracking is implemented for the Lofoten Basin of the Norwegian Sea. The ocean dynamic fields are obtained from the GLORYS 12V1 reanalysis available by the Copernicus Marine Environment Monitoring Service. Spatial distributions of the Lagrangian particles during May-November 2014 are analyzed for two depth layers: the sea-surface (0.5 m) and 266 m. The results show a significant impact of the Norwegian Coastal Current (NCC) on the thermohaline structure of the upper Lofoten Basin, underestimated previously. The NCC penetrates deep into the central Lofoten basin as far as the longitude 0°. In the subsurface layer, the area over which the NCC influences water structure is comparable to the area of the Norwegian Atlantic Slope Current (NASC), as well as to that of the Norwegian Atlantic Frontal Current (NAFC). The NCC maximum influence on the surface water of the Basin is reached in August. The inflow of the NCC is associated with relatively fresh water intrusions (0.5–2‰ fresher than the surrounding waters) moving from the coast to the central part of the Basin. The NASC and NAFC form two main sources of the Atlantic Water in the Lofoten Basin. At 266 m level, the NASC and NAFC waters dominate water structure in the basin. Herewith the NASC influence prevails over that of the NAFC, the latter being limited to the western periphery of the Basin. At this level, the NCC is observed only along a narrow band following the eastern coast. During summer, the core of the Lofoten Vortex (LV) at 266 m is mainly composed of the NAFC water. This fact contradicts the previous point of view of the dominance of the NASC in the LV core at all depth levels. Using two types of Lagrangian maps, we highlighted the summer and the autumn periods in the LV annual lifecycle. The summer LV is characterized by high orbital velocities, which are several times higher than those of the currents along the basin boundaries. The monthly mean orbital velocities in the LV reach 35 сm s⁻¹. To the end of autumn, the LV weakens with the monthly mean orbital velocities below 10 cm s⁻¹.  相似文献   

Annual Frequency of Tropical Cyclones Directly Affecting Guangdong Province:Prediction Based on LSTM-FC     

胡娅敏  陈韵竹  何健  刘圣军  闫文杰  赵亮  汪明圣  李芷卉  王娟怀  董少柔  刘新儒 《热带气象学报(英文版)》2022,28(1):45-56

Tropical cyclone (TC) annual frequency forecasting is significant for disaster prevention and mitigation in Guangdong Province. Based on the NCEP-NCAR reanalysis and NOAA Extended Reconstructed global sea surface temperature (SST) V5 data in winter, the TC frequency climatic features and prediction models have been studied. During 1951-2019, 353 TCs directly affected Guangdong with an annual average of about 5.1. TCs have experienced an abrupt change from abundance to deficiency in the mid to late 1980 with a slightly decreasing trend and a normal distribution. 338 primary precursors are obtained from statistically significant correlation regions of SST, sea level pressure, 1000hPa air temperature, 850hPa specific humidity, 500hPa geopotential height and zonal wind shear in winter. Then those 338 primary factors are reduced into 19 independent predictors by principal component analysis (PCA). Furthermore, the Multiple Linear Regression (MLR), the Gaussian Process Regression (GPR) and the Long Short-term Memory Networks and Fully Connected Layers (LSTM-FC) models are constructed relying on the above 19 factors. For three different kinds of test sets from 2010 to 2019, 2011 to 2019 and 2010 to 2019, the root mean square errors (RMSEs) of MLR, GPR and LSTM-FC between prediction and observations fluctuate within the range of 1.05-2.45, 1.00-1.93 and 0.71-0.95 as well as the average absolute errors (AAEs) 0.88-1.0, 0.75-1.36 and 0.50-0.70, respectively. As for the 2010-2019 experiment, the mean deviations of the three model outputs from the observation are 0.89, 0.78 and 0.56, together with the average evaluation scores 82.22, 84.44 and 88.89, separately. The prediction skill comparisons unveil that LSTM-FC model has a better performance than MLR and GPR. In conclusion, the deep learning model of LSTM-FC may shed light on improving the accuracy of short-term climate prediction about TC frequency. The current research can provide experience on the development of deep learning in this field and help to achieve further progress of TC disaster prevention and mitigation in Guangdong Province.  相似文献   

利用面向对象的分类方法从IKONOS全色影像中提取河流和道路   总被引：24，自引：0，他引：24  

孙晓霞  张继贤  刘正军 《测绘科学》2006,31(1):62-63

传统的基于像素的统计特征的分类方法在处理高分辨率影像的分类问题上遇到了很大的困难。本研究利用面向对象的影像分析方法对IKONOS全色影像进行了河流与道路的分类,包括利用影像对象的光谱特征的初次分类和利用子目标对象的线特征的二次分类两个过程;其中初次分类由于仅依据光谱信息,不能很好地将河流或道路与其他光谱特征相似的地物区分开,而通过引入子目标的形状特征进行二次分类,就可以准确地将河流与道路提取出来。试验结果表明,面向对象的分类方法能够满足高分辨率或纹理影像的分类需要,具有很大的应用潜力。  相似文献   

在空间抽象中线状目标间拓扑关系的等价转换   总被引：2，自引：0，他引：2  

郭庆胜  蔡永香  杜晓初 《测绘科学》2006,31(5):42-44

拓扑关系在抽象过程中的等价转换是维护多尺度空间关系一致性的基础。本文以空间拓扑关系组合推理所描述的线状目标之间的拓扑关系为例,采用成分抽象的等价转换方法,研究了线之间拓扑关系等价转换的原则,并绘出了相应的等价转换图。  相似文献   

基于对象流的地缘环境时空分析模型     

赵文双  江南  陈云海  曹一冰 《地球信息科学学报》2022,24(8):1432-1444

地缘环境时空分析是对地缘体、地缘关系及地缘结构进行的解析、评价和预测,是把握地缘环境空间特征、关联关系演化规律的重要途径。本文采用文献研究、类比归纳、建模研究等方法,提出地缘环境对象是地理信息世界中对现实地缘环境实体抽象后的数字化表达,地缘环境对象流是对象间物质、信息和能量数据交互过程的总称,与地缘关系间存在映射关系,对地缘环境态势和演化过程具有关键作用。在对地缘环境对象流相关概念和内涵解析的基础上,探讨了地缘环境对象流的数据表达与组织方法,构建了地缘环境分析模型,模型从地缘环境系统构成出发,将地缘环境对象流的分析逻辑和数据模型结合,分别建立地缘环境对象流分析原理的逻辑表达及地缘环境对象化数据组织体系,在数据支持下利用数据分析算法来确定地缘环境对象与地缘关系间的映射函数,实现面向应用场景和具体问题的地缘环境分析。本文对地缘环境分析模型进行了验证,以“印太地区”地缘经济环境分析为例,基于2009—2018年该区域经济水平排位前10的国家经济数据,进行了地缘经济实体特征的抽象、贸易对象流的数据表达与组织、数据分析及地缘关系测度,分析了贸易流的时空变化过程、地缘影响力以及地缘关系群组等,验证了模型在面向具体场景的地缘环境分析中的有效性。  相似文献