超高速水下航行器横滚控制研究

超高速水下航行器航行时由于被超空泡包裹着,使得其工况变得更为复杂,控制难度进一步加大;为了抑制或消除横滚,文章通过分析超高速水下航行器的运动特点,建立了航行器横滚运动模型方程,并进行特性分析和控制规律综合设计,最后提出使用配置控制面的方法来实现它的横滚控制;此方法的使用既为系统提供控制力又解决了系统弱阻尼的问题,同时还提高了系统的响应速度;最后运用PD算法,分析它的动态特性和幅频特性,仿真结果表明此方案简单,容易实现,且鲁棒性好,满足系统的要求。     

超高速水下航行器航向控制研究

超高速水下航行器在水下航行时,表面大部分被超空泡所包覆,其运动特性发生显著变化,使得其工况变得更为复杂、控制难度加大;通过分析它的运动特点,建立了系统模型方程,并提出把空化器作为控制面,通过操纵其舵角改变量来控制航行器航向;最后运用PI极限舵控制算法进行仿真分析,结果表明此控制方法简单易实现,产生的偏差小,同时还提高了系统的响应速度,较好地满足了系统要求,分析结论可为超高速水下航行器控制系统设计提供参考。     

超高速水下航行器纵平面姿态控制研究

超高速水下航行器在水下航行时,由于大部分表面被超空泡所包覆,其纵平面的运动特性发生显著变化,使得控制难度加大.提出把空化器用作控制面,通过操纵其舵角改变量来控制航行器在纵平面的运动,从而达到间接控制航深的目的.最后运用PID算法进行仿真分析,结果表明采用此控制方法所产生的深度负偏差较小,简单易实现、且鲁捧性好.还对航行器直接深度控制进行探讨,考虑到超空泡工况下深度测量的难度较大,姿态控制具有更强的适用性.     

水下航行器X字型舵面故障分析与仿真

X字型舵水下航行器与十字型舵水下航行器相比,舵机系统具有功能冗余性.目前国内对舵机系统的故障诊断主要是针对十字型舵,而对于X字型舵的研究还比较少.针对上述情况,论文分析了X字型舵与十字型舵水下航行器舵面布局的差异以及X字型舵水下航行器流体动力特性,建立了X字型舵水下航行器力及力矩模型,研究了X字型舵在舵面故障情况下动力特性的改变,给出了X字型舵舵面损伤时横滚角的动态变化.仿真结果表明,X字型舵水下航行器在舵面损伤时横滚角趋于发散,通过设置合适的观测器,就能检出该故障,对进一步研究X字型舵水下航行器的故障诊断具有重要的作用.     

水下超高速航行器首舵控制系统的设计

水下超高速航行器处于巡航阶段时,由于其大部分表面被超空泡包裹,运动模式不同于常规的全沾湿航行器;为了对超高速水下航行器的定深弹道实施控制,在研究水下超高速航行器运动模型的基础上,对首舵机控制系统的控制率进行了综合,研制了一种新型的深度间接控制的电动首舵机闭环控制系统;详细介绍了功率控制单元的工作原理、硬件设计的关键技术及控制软件设计;地面考核试验证明该控制系统完全满足超高速航行器的姿态控制要求;研究结果可为水下超高速航行器控制系统的设计提供参考。     

多操纵面战斗机动态控制分配策略研究

针对多操纵面战斗机飞行控制系统中操纵面控制分配器设计问题,提出了一种动态控制分配策略方案.策略从频率域角度建立虚拟控制量和实际控制量的动态映射,充分利用操纵面的不同带宽,将期望力矩分配到各个操纵面,使各个操纵面协调工作,达到最大控制效能.数字仿真结果表明相对于其他控制分配策略,采用动态控制分配策略的控制分配器在达到控制要求的同时,可以有效地减小座舱过载并使配平阻力最小.取得了良好的控制效果.     

高空滑翔UUV气动参数估算与气动特性分析

研究水下航行器,针对无人水下航行器无法同时大幅度提高航速和航程的现状,为优化无人水下航行器气动特性,增强系统的稳定性,提出了高空滑翔无人水下航行器(UUV)总体气动布局进行设计.对气动特性进行分析,根据飞机和导弹气动参数的估算方法,通过类比的方式,对升力系数、阻力系数、俯仰力矩系数、航向静导数、动导数和操纵导数等主要气...     

混合驱动水下航行器水平推进模式水动力特性

关于水下航行器结构设计优化问题,混合驱动水下航行器(HUG)是一种新型水下航行器,实现了自治式水下航行器(AUV)与水下滑翔机(AUG)结构和功能的集成,具有航速大、航程长、机动性好等特点.混合驱动水下航行器所受水阻力与机动性是其水平推进模式(AUV模式)下的重要性能指标.针对混合驱动水下航行器的要求与结构特点,采用计算流体力学方法,分析了航行器在AUV模式下的航行水阻力和机动性.研究表明,混合驱动水下航行器在集成AUV与AUG功能优势的同时,在AUV运行模式下,航行阻力将增大约30％,航行机动性降低约15 ～25％.结果为混合驱动水下航行器的外形设计提供了依据.     

基于PC104的超高速水下航行器测控程序设计与实现

超高速水下航行器自主航行试验需要雷载计算机提供时序控制、姿态自动控制等支持,在恶劣水下环境中测控系统的可靠性至关重要,它影响着实航数据的获取和航行控制研究的开展.以PC104嵌入式计算机为硬件平台,标准C语言为开发工具,针对超高速水下航行器航行控制和数据测量需求开发了测控程序.通过电平I/O进行时序及航行姿态控制,串口...     

湍流模型和网格分布对水下航行体回转水动力数值计算的影响

针对水下航行体安全操纵设计的关键环节水动力预报,用FLUENT求解不可压缩RANS方程,采用定常旋转运动坐标系,运用相对运动理论和运动叠加原理,计算RNG k-ε,可实现k-ε和SST k-ε等3种湍流模型以及不同网格分布对水下航行体做单平面回转运动所受垂向力和纵倾力矩,并与试验结果比较.结果表明在Re=11.7×106条件下,垂向力和纵倾力矩预报精度较高.该数值预报方法可行、有效,具有较好的工程实用价值.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.