Adaptive Controller Design for Unknown Systems Using Measured Data

This paper presents a measurement‐based adaptive control design approach for unknown systems working over a wide range of operating conditions. Traditional control design approaches usually require the availability of a mathematical model. However, it has been shown in many practical situations that, due to complex dynamics of physical systems, some simplifying assumptions are made for the derivation of mathematical models. Hence, controller design based on simplified models may result in degradation of the desired closed‐loop performance. Data‐based control design approaches can be viewed as an alternative approach to model‐based methods. Most data‐based control methods available in the literature aim to design controllers for unknown systems that operate only at a given operating point. However, the dynamical behavior of plants may change for different operating conditions, which makes the task of designing a controller that works over the entire range of operating conditions more challenging. In this paper, we address such a problem and propose to design adaptive controllers based on measured data. Such a proposed method is based on designing a set of measurement‐based controllers validated at a finite set of pre‐specified operating points. Then, the parameters of the adaptive controller are obtained by interpolating between the set of pre‐designed controller parameters to derive a gain‐scheduling controller. Moreover, low‐order adaptive controllers can be designed by simply selecting the desired controller structure. The efficacy of the proposed approach is experimentally validated through a practical application to control a heating system operated over a large range of flow rate.     

目标成本值最优的物联网WSS蠕虫抑制算法

物联网无线服务系统(wireless service system, WSS)是以通用的协议标准实现人与物、物与物相连的实时网络交互系统.该系统在设备中嵌入无线传感器节点以实现数据上传和决策下发,但传感器节点的同构性特点使得蠕虫传播问题日益严重.为此,在对现有蠕虫传播的流行病模型进行分类并总结各类模型特点的基础上,首先提出了具有睡眠状态和隔离状态的流行病模型,定义了系统中节点的状态转换关系;其次,依据节点的射频通信距离,确定了具有实际传染能力的感染节点数量及范围;再次,引入蠕虫与无线服务系统的目标成本函数,给出了基于目标成本值的完全信息动态微分博弈模型;然后,证明了该博弈存在鞍点策略,利用状态变量、协状态变量和汉密尔顿函数求解鞍点策略并设计了保证目标成本值最优的防御策略算法;最后,仿真实现本算法与2种蠕虫防御策略算法,通过各状态节点的变化特点及目标成本值的对比实验进行性能评估.实验结果表明：基于改进流行病模型的最优防御算法在抑制无线服务系统蠕虫传播方面有明显优势.     

Enabling service adaptability with versatile anycast

We present versatile anycast, which allows a service running on a varying collection of nodes scattered over a wide‐area network to present itself to the clients as one running on a single node. Providing a single logical address enables the client‐side software to preserve the traditional service access model based on single access points. At the same time, the dynamic composition of anycast groups implemented by versatile anycast enables the server‐side service infrastructure to evolve and adapt to changing network conditions. We implement versatile anycast using Mobile IPv6, which decouples the logical addresses of mobile nodes from their physical location. We exploit that decoupling to implement logical service addresses that are not bound to any physical nodes, and employ standard MIPv6 mechanisms to dynamically map each such address onto individual service nodes. Our solution enables a service to transparently hand off clients among the service nodes at the network level while preserving optimal routing between the clients and the service nodes. We demonstrate that the overhead of versatile anycasting is very low. In particular, the client‐perceived handoff time is shown to be a linear function of the latencies among the client and the service nodes participating in the handoff. Copyright © 2007 John Wiley & Sons, Ltd.     

MANET下环境感知的服务可用性量化评估模型

移动Ad hoc网络(MANET)环境下,移动节点通过向其他节点提供服务是进行资源共享与能力协同的有效方式.但是由于 MANET环境的复杂性、链路的动态性和节点的异构性等特点,使得服务可用性时刻都在发生变化,且难以量化.通过对 MANET环境下服务运行环境和对影响服务可用性的节点、网络环境可用性的分析,提出了一个具有环境感知能力的服务可用性量化评估模型EQAM-SA,该模型由服务请求触发,实时获取服务运行参数、量化评估指标,并采用层次分析法和多属性综合评估法对服务的可用性进行量化评估.最后通过仿真实验验证了EQAM-SA的可行性和有效性.     

TT-BIP: using correct-by-design BIP approach for modelling real-time system with time-triggered paradigm

In order to combine advantages of real-time operating systems implementing the time-triggered (TT) execution model and model-based design frameworks, we aim at proposing a correct-by-design methodology that derives correct TT implementations from high-level models. This methodology consists of two main steps: (1) transforming the high-level model into an intermediate model which respects the TT communication principles and where all communications between components are simple send/receive interactions, and (2) transforming the obtained intermediate model into the programming language of the target platform. In this paper, we focus on the presentation of the transformational methodology of the first step of this design flow. This methodology produces a correct-by-construction TT model by starting from a high-level model of the application software in behaviour, interaction, priority (BIP). BIP is a component-based framework with formal semantics that rely on multiparty interactions for synchronizing components. Commonly in TT implementations, tasks interact with each other through a communication medium. Our methodology transforms, depending on a user-defined task mapping, high-level BIP models where communication between components is strongly synchronized, into TT model that integrates a communication medium. Thus, only inter-task communications and components participating in such interactions are concerned by the transformation process. We also provide correctness proofs of the transformation and apply it on an industrial case study.     

基于CPN模型的REST服务架构标准特征验证方法研究

当前REST服务架构广泛应用于大规模、可扩展的分布式Web系统中,若应用REST服务架构时不遵循其标准特征,则可能导致基于REST服务架构的Web系统出现性能下降、可扩展性低等问题。因此,实现基于REST服务架构的Web系统前,需要对该系统设计是否满足REST服务架构标准特征进行验证,以提升基于REST服务架构的Web系统的研发质量。提出一种基于CPN模型的REST服务架构标准特征验证方法,即对REST服务架构的五个标准特征约束进行CPN建模,并使用模型状态空间执行路径同步匹配的验证方法,以应用系统的CPN模型和标准特征约束的CPN模型为基础,对模型状态空间中的各自执行路径进行同步匹配,若路径可同步执行完毕,则说明该应用系统满足该REST标准特征约束。以基于REST服务架构的课程管理Web系统为例,验证上述方法的可用性和有效性。实验结果表明,本文所提验证方法可以有效确认基于REST服务架构的Web应用系统设计是否符合REST服务架构的标准特征约束,并在不符合标准特征约束时提供直观、可行的执行数据,便于后续完成应用系统设计缺陷定位及修正。     

基于REST服务的虚拟DCS平台

为解决虚拟DCS平台可重构能力差的问题,提出基于REST服务的虚拟DCS平台.首先给出基于REST的数据存取服务模型,其中包括模型的总体描述、数据对象元数据及客户端使用的方法.然后介绍DPU的建模方法,分析虚拟控制站和虚拟操作员站的实时数据流向,并在此基础上对虚拟DCS应用系统各站点之间的通信进行了优化.最后,通过一个...     

The evaluation of software systems' structure using quantitative software metrics

The design and analysis of the structure of software systems has typically been based on purely qualitative grounds. In this paper we report on our positive experience with a set of quantitative measures of software structure. These metrics, based on the number of possible paths of information flow through a given component, were used to evaluate the design and implementation of a software system (the UNIX operating system kernel) which exhibits the interconnectivity of components typical of large-scale software systems. Several examples are presented which show the power of this technique in locating a variety of both design and implementation defects. Suggested repairs, which agree with the commonly accepted principles of structured design and programming, are presented. The effect of these alterations on the structure of the system and the quantitative measurements of that structure lead to a convincing validation of the utility of information flow metrics.     

Enabling high‐speed asynchronous data extraction and transfer using DART

As the complexity and scale of applications grow, managing and transporting the large amounts of data they generate are quickly becoming a significant challenge. Moreover, the interactive and real‐time nature of emerging applications, as well as their increasing runtime, make online data extraction and analysis a key requirement in addition to traditional data I/O and archiving. To be effective, online data extraction and transfer should impose minimal additional synchronization requirements, should have minimal impact on the computational performance and communication latencies, maintain overall quality of service, and ensure that no data is lost. In this paper we present Decoupled and Asynchronous Remote Transfers (DART), an efficient data transfer substrate that effectively addresses these requirements. DART is a thin software layer built on RDMA technology to enable fast, low‐overhead, and asynchronous access to data from a running simulation, and supports high‐throughput, low‐latency data transfers. DART has been integrated with applications simulating fusion plasma in a Tokamak, being developed at the Center for Plasma Edge Simulation (CPES), a DoE Office of Fusion Energy Science (OFES) Fusion Simulation Project (FSP). A performance evaluation using the Gyrokinetic Toroidal Code and XGC‐1 particle‐in‐cell‐based FSP simulations running on the Cray XT3/XT4 system at Oak Ridge National Laboratory demonstrates how DART can effectively and efficiently offload simulation data to local service and remote analysis nodes, with minimal overheads on the simulation itself. Copyright © 2010 John Wiley & Sons, Ltd.     

基于RESTFUL的学术资源发布平台

利用具有表述性状态转移（REsT）的Web服务，设计一种面向资源的学术讲座信息服务。将学术讲座标准信息作为服务接口，采用REST技术，以资源形式对外公开，从而实现信息共享和功能互操作。     

可能性测度下的LTL模型检测并行化研究

分布式模型检测是一种缓解状态空间爆炸的有效途径,已有文献提出了定性的分布式模型验证算法,然而定量LTL验证算法并行化问题还未得到有效解决。对此,展开两个方面的工作:提出一种新的动态系统状态空间划分方法;在定性LTL分布式验证算法的基础上给出了定量模型检测并行化验证算法。首先,将系统模型转化为可能的Kripke结构并选取一个并发分量,依据状态之间的关系完成系统状态的分割,使得关系紧密的状态尽可能分布在同一个计算节点上;其次,调整划分结果以使得计算负载平衡;然后,将划分结果与其他并发分量的状态进行叉乘,以完成系统状态空间的划分;最后,将待检测性质用自动机表示,在两者的乘积上,利用扩展的基于嵌套DFS的分布式验证算法完成系统的定量验证。     

A sliding mode controller for a model of flow separation in boundary layers

In this paper, we propose a sliding mode controller for a MIMO model of flow separation in boundary layers. The model consists in a bilinear system with constant delays in both the state and the input. The main motivation to consider such a class of systems is that it has shown to be suitable for input‐output modeling and control design of some turbulent flow control systems. Stability and robustness properties of the control scheme are studied by means of Volterra equations theory, which provides easily verifiable stability conditions.     

Replacement and standby redundancy policies in a deteriorating system with aging and random shocks

This study investigates the state-dependent maintenance policy in a multistate deteriorating production system with standby redundancy, assuming that the production system consists of one production unit and one single-server service center, and the key component of the production unit deteriorates over time. The key component deteriorates either from the current operating state to the next inferior operating state, due to aging, or from the current operating state to the failure state, due to a random shock. The deteriorating key component is replaced with a standby, according to a certain replacement policy, and sent to the service center for perfect repair; once completing the service, it joins the standbys for later production use. Both the sojourn time of a key component in each operating state, except the failure state, and the service time of a key component at the service center are assumed to be exponentially distributed. Taking into account the annual operating profit, measured in terms of production utilization and yield percentage of perfect items, and the annual operating costs, including the costs of key components and maintenance, this study jointly selects the operating state for replacing deteriorating key components and the level of standby redundancy in the system under the profit maximization objective. Numerical examples are given to illustrate the maintenance policies for systems with different transition probabilities in the deteriorating process, and the influence of transition probabilities on the maintenance policies are discussed.     

基于云模型的可信性评估模型*

软件应用领域极度扩展,促使软件可信问题被高度重视,但量化的软件可信性评估却是可信问题研究的难点。针对软件可信性量化问题,提出了基于云模型的可信性评估模型。以REST表述性状态转移超媒体分布式架构为背景,根据云模型理论定义了其组成构件的信任云以及系统综合信任云,用于评估构件的可信性和系统的可信性。从四个层面,探讨软件可信问题,以可信基础参数获取作为最底层输入,进而生成云模型,合并云模型,最终进入可信评估应用层面。实验结果表明,基于云模型的可信性评估模型是有效实用的,在可信度的不确定性方面增加了评估的灵活性。     

网络流场：理论和方法

随着互联网的迅猛发展,网络运营部门和网络管理部门迫切需要分析网络的运行状况,以保证网络的可用性、稳定性和安全性。然而,目前对网络运行状况的分析难度正逐渐增大,用户数量的快速增长,网络带宽的不断增加,网络流量的频繁变化以及新应用日趋复杂等,均给网络流量分析带来了巨大的挑战。因此,为了解决目前网络分析技术面临的难题和挑战,提出了一种网络流量分析的新型方法——网络流场理论和方法。网络流场不仅关注如数据包及网络流等“硬性”指标,而且更关注网络中的流量分布和发展趋势,因此能反映出网络流的分布以及节点之间的关系,从而反映网络的社会属性。网络流场以全新的视角对网络进行剖析,并进行定性和定量的分析,不仅能分析网络流量的基本信息,而且可以挖掘网络中的隐含信息,如时序关系、状态转换关系、私有网络拓扑、关键节点和关键路径等。实验结果表明,网络流场可以取得很好的分析效果,网络流场理论既可以有效地为现有的网络管理及网络分析提供更高层次的研究架构和研究模型,指导网络管理、分析、测量及安全保障等领域的研究和实践,又有利于网络的发展和技术的进步。     

基于BIP框架的DPU系统建模与验证

DPU(data process unit,数据处理单元)是嵌入式系统中的一个典型组件,被广泛应用于太空领域,它在层次化的嵌入式系统架构中起到承上启下的作用。保证这类安全攸关系统可靠性的主要方法包括冗余容错、测试和仿真。近年来,形式化方法作为确保可靠性的一种重要补充,得到了广泛的关注。BIP(behavior interaction priority)是一个通用的系统级形式化建模框架,支持层次化和模块化,包含一套支持建模、模拟和验证的工具集。给出了一种基于BIP框架对DPU进行系统级建模与验证的一般方法,总结了一套使用BIP框架对DPU建模应遵循的原则及技巧。以航天领域一个真实DPU系统为例,系统地对方法、原则和技巧进行了介绍。通过该方法,找出了使用传统方法难以发现的错误。实践表明,该方法具有很好的可复用性和可扩展性,是确保系统可靠性的有益补充。     

Optimizing operating system performance for CC‐NUMA architectures

The CC‐NUMA (cache‐coherent non‐uniform memory access) architecture is an attractive solution to scalable servers. The performance of a CC‐NUMA system heavily depends on the number of accesses to remote memory through an interconnection network. To reduce the number of remote accesses, an operating system needs to exploit the potential locality of the architecture. This paper describes the design and implementation of a UNIX‐based operating system supporting the CC‐NUMA architecture. The operating system implements various enhancements by revising kernel algorithms and data structures. This paper also analyzes the performance of the enhanced operating system by running commercial benchmarks on a real CC‐NUMA system. The performance analysis shows that the operating system can achieve improved performance and scalability for CC‐NUMA by implementing kernel data striping, localization and load balancing. Copyright © 2003 John Wiley & Sons, Ltd.     

Converting command‐line applications into binary components

A binary component is a separately compiled program that can be used as a part of a larger program. Binary components generally conform to an accepted technology such as JavaBeans or ActiveX, and generally support a rich program interface containing properties, methods and events. Binary components are generally used in a graphical user interface (GUI) environment. There are a number of benefits to be realized by converting command‐line software into binary components. The most important of these is that GUI environments are more popular and more familiar to most people than command‐line environments. Using binary components can greatly simplify a GUI implementation, to the point where it is only slightly more complicated than a typical command‐line implementation. However there are benefits that go beyond mere convenience. Binary components have much richer interfaces than command‐line programs. Binary components are service‐oriented rather than task‐oriented. A task‐oriented program has a main routine that is devoted to accomplishing a single task. A service‐oriented component has no main routine or main function, but instead provides a variety of services to its clients. Binary components can be easily integrated with one another, which permits a design where each major feature of an application is implemented in a different component. Such a design encourages software reuse at the component level and facilitates low‐impact feature upgrades. We first delineate a design‐pattern‐based methodology for converting command‐line programs into components. We then illustrate these principles using two projects, a simulation system for digital circuits, and a data generation system for software and hardware testing. Copyright © 2005 John Wiley & Sons, Ltd.     

用信息流控制保证软件可信运行

提出一种基于信息流控制来保证软件可信运行的方法。首先设计一种信息流控制模型,该模型的访问规则、传播规则和感染规则基本涵盖了软件在操作系统运行过程中产生信息流的主要类型。其次,设计一种策略描述语言,该语言使软件管理者可以以一种较为直观的方式描述所期望的软件信息流。在Linux内核部分实现原型系统,实验证明该方法可以控制软件所产生的信息流,从信息流角度保证软件的可信运行。     

A compact multi‐band multi‐input multi‐output antenna for 4G/5G and IoT devices using theory of characteristic modes

A compact four element multi‐band multi‐input multi‐output (MIMO) antenna system for 4G/5G and IoT applications is presented in this paper. The proposed antenna is developed using the theory of characteristic modes helping in systematic design of MIMO antenna system. It consists of four L‐shaped planar inverted‐F antenna (PIFA) elements each operating at 3.5, 12.5, and 17 GHz bands with the bandwidth of 359 MHz, 1 GHz, and more than 3.7 GHz, respectively. The proposed antenna system is suitable for both 4G/5G and internet of things devices as it shows the satisfactory MIMO system performance. Good isolation characteristics are observed by implementing complimentary Metamaterial structure on the ground plane resulting in isolation level lower than ?21 dB between the antenna elements. The proposed antenna is fabricated and experimental results are also presented and discussed.