Time-varying feedback laws for decentralized control

Decentralized control schemes are considered for time-invariant, finite dimensional, linear systems with know state equations. It is assumed that the systems are reachable and observable at a fictitious centralized control station, and that there is strong connectivity between the decentralized control stations via the system where necessary. It is shown that whether or not there are decentralized fixed modes in the open-loop system, periodically varying feedback gains at all but one of the control stations permit the remaining control station to observe and control the system given knowledge of the control laws implemented at the other control stations. Certain time-invariant systems which cannot be stabilized by decentralized time-invariant controllers, namely those with unstable decentralized fixed modes, can thus be stabilized by decentralized time-varying controllers.     

Decentralized control of symmetric systems

This paper is concerned with the stabilizability problem of symmetric systems by means of decentralized controllers. It is shown that the set of decentralized fixed modes of a symmetric system is equal to the set of uncontrollable and unobservable modes of the system and implies that the stabilizability of a state-space symmetric system by means of a decentralized controller is equivalent to the stabilizability for the system by means of a centralized controller.     

新型分布式全电子计算机联锁系统

以联锁机为核心的集中控制方式是目前计算机联锁系统的主流,但该方式存在风险集中,工程造价较高,系统维护困难等问题。随着计算机、控制和通信技术的发展,分布式控制结构的优势日益突显。为了进一步提高系统的可靠性、安全性和灵活性,引入区域控制的概念,并将其与分布式控制、智能控制等技术相结合,在符合计算机联锁技术条件的基础上提出了一种新型的分布式全电子计算机联锁结构。给出了该计算机联锁系统中区域控制器的模型,对其联锁功能、网络结构进行了详细介绍。该结构实现了地理上和功能上的分散控制,有效降低了系统风险,符合铁路信号故障-安全的要求。     

基于JXTA的无线网络应用

随着移动计算设备的发展,应用程序的开发者需要解决移动无线网络中诸如移动终端,低带宽,连接的不确定性以及无集中式网络设备等一系列问题,本文从开放式P2P应用程序开发平台JXTA出发,讨论了一种基于JXTA的无线网络的应用。主要介绍了P2P非集中式网络系统结构、JXTA通用平台以及JXTA的基本组件、参考模型等,并通过一个JXME实例说明了JXME无线网络架构的优势。     

基于JXTA的无线网络应用

随着移动计算设备的发展，应用程序的开发者需要解决移动无线网络中诸如移动终端，低带宽，连接的不确定性以及无集中式网络设备等一系列问题，本文从开放式P2P应用程序开发平台JXTA出发，讨论了一种基于JXTA的无线网络的应用。主要介绍了P2P非集中式网络系统结构、JXTA通用平台以及JXTA的基本组件、参考模型等，并通过一个JXME实例说明了JXME无线网络架构的优势。     

Information organization in flexible automation systems

Felxible Automation Systems (FAS) are comprised of three major sybsystems: the workstations, material handling, and computer control. Much effort and research have been devoted to the first two and to system control, the loading and scheduling of the system. Little effort has been expended, however, on the information requirements of FASS, although their control is information intensive. Every move of every axis of every device must be coordinated, monitored, and controlled. Information must be stored and transmitted to the needed device at the appropriate time. The status of the system must be continuously surveyed, updated, and verified.Hierarchical systems have been suggested for the control of FMSS, and this has implications for their structure, which in turn influences computing and communication requirements, system performance, reliability, and failure recovery. This paper discusses storage and data flow requirements as a function of the system's manufacturing mission. Two control architectures, centralized and two-level distributed, are considered, and the computing, storage, and communications requirements calculated for each. Analysis of results indicates that there is a break-even point between centralized and decentralized systems that is a function of the manufacturing mission but independent of FAS size and operating environment.     

Communication Constraints for Decentralized Stabilizability With Time-Invariant Policies

In this note, we study communication requirements for decentralized control schemes when sensors and controllers are connected via noiseless digital channels and system noises are bounded. Under various information structures, and within the class of time-invariant encoding and control policies, we quantify achievable rates, and obtain fixed-rate and delayless encoders and decoders that achieve boundedness in the state estimation errors at the controllers. We use distributed coding theoretic approaches to show that when the sensors do not collaborate, it is sufficient for the controllers to share information amongst themselves but not with the sensors. Sensor collaboration, however, leads to improvement in rate performance.     

SocialVPN: Enabling wide-area collaboration with integrated social and overlay networks

Trusted collaborative systems require peers to be able to communicate over private, authenticated end-to-end channels. Network-layer approaches such as Virtual Private Networks (VPNs) exist, but require considerable setup and management which hinder the establishment of ad-hoc collaborative environments: trust needs to be established, cryptographic keys need to be exchanged, and private network tunnels need to be created and maintained among end users. In this paper, we propose a novel system architecture which leverages existing social infrastructures to enable ad-hoc VPNs which are self-configuring, self-managing, yet maintain security amongst trusted and untrusted third parties. The key principles of our approach are: (1) self-configuring virtual network overlays enable seamless bi-directional IP-layer connectivity to socially connected parties; (2) online social networking relationships facilitate the establishment of trust relationships among peers; and (3) both centralized and decentralized databases of social network relationships can be securely integrated into existing public-key cryptography (PKI) implementations to authenticate and encrypt end-to-end traffic flows. The main contribution of this paper is a new peer-to-peer overlay architecture that securely and autonomously creates VPN tunnels connecting social peers, where online identities and social networking relationships may be obtained from centralized infrastructures, or managed in a decentralized fashion by the peers themselves.This paper also reports on the design and performance of a prototype implementation that embodies the SocialVPN architecture. The SocialVPN router builds upon IP-over-P2P (IPOP) virtual networks and a PKI-based tunneling infrastructure, which integrates with both centralized and decentralized social networking systems including Facebook, the Drupal open-source content management system, and emailing systems with PGP support. We demonstrate our prototype’s ability to support existing, unmodified TCP/IP applications while transparently dealing with user connectivity behind Network Address Translators (NATs). We also present qualitative and quantitative analyses of functionality and performance based on wide-area network experiments using PlanetLab and Amazon EC2.     

High-performance decentralized control design for general interconnected systems with applications in cooperative control

This paper deals with the decentralized control of an interconnected system, where each subsystem has models of all other subsystems (subject to uncertainty). A decentralized controller is constructed based on a reference centralized controller. It is shown that when a priori knowledge of each subsystem about the other subsystems’ models is exact, then the decentralized closed-loop system can perform exactly the same as its centralized counterpart. An easy-to-check necessary and sufficient condition for the internal stability of the decentralized closed-loop system is obtained. Moreover, the stability of the closed-loop system in the presence of the perturbation in the parameters of the system is investigated, and it is shown that the decentralized control system is probably more robust than its centralized counterpart. A proper cost function is then defined to evaluate the closeness of the decentralized closed-loop system to the corresponding centralized control system. This enables the designer to obtain the maximum allowable standard deviation for the modelling errors of the subsystems to achieve a satisfactorily small relative performance deviation with a sufficiently high probability. Finally, the proposed method is exploited to design a near-optimal decentralized control law with respect to a quadratic cost function, whose performance can, under certain conditions, be equal to the minimum achievable performance index corresponding to the centralized LQR control law. The effectiveness of the proposed method is demonstrated in three numerical examples.     

Towards decentralized system-level security for MPSoC-based embedded applications

With the increasing connectivity and complexity of embedded systems, security issues have become a key consideration in design. In this paper, we propose a decentralized system-level approach for isolating application tasks without the need to rely on a centralized privileged authority at run-time. We discuss the need for isolation to reduce the potential impact of a task compromise or untrustworthy IP block, and present mechanisms to allow for safe sharing of memory regions and IP blocks between tasks in the system. After exploring the architectural requirements for enforcing our security model we present a hardware Isolation Unit, which can be customized for different types of dynamic permission changes depending on task-resource relationships and added to heterogeneous MPSoCs to enforce our security approach.     

Internet of intelligent things and robot as a service

The development of computing and communication systems has gone through a spiral cycle of centralization and decentralization paradigms. The earliest computer systems are centralized mainframe computers. The paradigm moved to decentralized as networked stations became more dependable, extensible and cost-effective. The decentralized systems have their limitations and inconveniences. The virtualization and cloud computing paradigm creates a centralized system that appears to users to be a centralized system, where computing and communication resources are not in the client computers but in an integrated infrastructure that is accessible anywhere and anytime. Nevertheless, the implementation of the centralized infrastructure is equipped with decentralized and redundant resources, which makes the system more dependable as any component failures can be tolerated internally. The Internet of Things extends the cloud computing concept beyond computing and communication to include everything, particularly, the physical devices. This paper discusses the architectures, interfaces, and behaviors of intelligent devices connected to the cloud computing environment. Robot as a Service is the case study, which has all the key features of Internet of Intelligent Things: autonomous, mobile, sensing, and action taking. The goal is to further extend the centralized cloud computing environment into a decentralized system to complete another cycle of the spiral development. The idea of achieving the goal is through autonomous and intelligent mobile physical services or robots as services to form local pool of intelligent devices and that can make local decisions without communicate with the cloud.     

A decentralized approach for mining event correlations in distributed system monitoring

Nowadays, there is an increasing demand to monitor, analyze, and control large scale distributed systems. Events detected during monitoring are temporally correlated, which is helpful to resource allocation, job scheduling, and failure prediction. To discover the correlations among detected events, many existing approaches concentrate detected events into an event database and perform data mining on it. We argue that these approaches are not scalable to large scale distributed systems as monitored events grow so fast that event correlation discovering can hardly be done with the power of a single computer. In this paper, we present a decentralized approach to efficiently detect events, filter irrelative events, and discover their temporal correlations. We propose a MapReduce-based algorithm, MapReduce-Apriori, to data mining event association rules, which utilizes the computational resource of multiple dedicated nodes of the system. Experimental results show that our decentralized event correlation mining algorithm achieves nearly ideal speedup compared to centralized mining approaches.     

An Approach to Distributed Computing System Software Design

Distributed computing systems represent a wide variety of computer systems, ranging from a centralized star network to a completely decentralized computer system. The design of software for distributed computing systems is more complicated due to many design constraints and interactions of software components of the system.     

Output feedback decentralized stabilization: ILMI approach

In this paper, the static output feedback decentralized stabilization problem is addressed using a linear matrix inequality approach. A necessary and sufficient condition for static output feedback decentralized stabilizability is derived for linear time-invariant large-scale systems. It is proven that the existence of a stabilizing decentralized gain is equivalent to that of the solution of a quadratic matrix inequality. The extension of the result to control is studied. An iterative LMI algorithm based on the linear matrix inequality technique is proposed to obtain the decentralized feedback gain. Examples show the effectiveness of the algorithm.     

Graph-theoretic approach to controllability and localizability of decentralized control systems

The controllability and the localizability problems are considered under the decentralized information structure using some concepts from graph theory. First of all, the information structure graph is introduced for a decentralized control system based upon local output controllability, matrices between stations when a local output feedback law is applied, and some invariant properties of the graph with respect to local output feedback laws are driven. Then by using these results, necessary and sufficient conditions of controllability under decentralized information structure are obtained. Also obtained are several conditions for localizability, of decentralized control systems, which is newly introduced in the present paper as an extended concept of a class of disturbance localization and decoupling for centralized systems.     

一类多模块网格存储系统分散式控制方法

针对多模块网格存储系统中的多分拣点货物排列问题,提出一种解耦的分散式控制方法,将问题解耦为各存储模块的独立调度和模块之间的协调调度.模块内采用循环移动方式进行独立调度,模块间通过交换需求和模块状态控制协调过程.在不同参数条件下进行仿真实验,并与集中式控制方法进行对比仿真,结果表明分散式控制方法能够在各种工况下稳定有效地...     

A multi-agent approach for integrated emergency vehicle dispatching and covering problem

The most important decisions that should be made by emergency vehicle managers are related to the allocation and the covering problems. The allocation (or dispatching) problem consists of deciding which vehicle must be assigned to assist an emergency in the best times. The covering problem aims at keeping the region under surveillance well-covered by relocating available vehicles. As components are geographically distributed, decentralized solution approaches may present several advantages. This paper develops a decentralized distributed solution approach based on multi-agent systems (MAS) to manage the emergency vehicles. The proposed system integrates the dispatching of vehicles to calls with zone coverage issues. This integration means that allocation and covering decisions are considered jointly. The idea of MAS has been applied in many others real-world contexts, and has been proven to provide more flexibility, reliability, adaptability and reconfigurability. To our knowledge, there is no existing work that uses MAS for real-time emergency vehicle allocation problem while accounting for the coverage requirements for future demands. We propose a multi-agent architecture that fit the real emergency systems, and that aims at keeping good performance compared to the centralized solution. The objective is to coordinate agents to reach good quality solutions in a distributed way. For this purpose two approaches are examined. The first one is used to show the impact of distributing data and control on the solution quality, since the dispatching decisions are based only on local evaluations of the fitness. The second approach is based on implicit agents' coordination using a more refined and efficient auction mechanism. The performance of each approach is compared to the centralized solution obtained by solving the proposed model with ILOG CPLEX solver. The obtained results show the importance of the coordination method to keep a good quality of service while distributing data and decision making, and prove the performance of the second approach.     

Decentralized blocking zeros and the decentralized strongstabilization problem

This paper is concerned with a new system theoretic concept, decentralized blocking zeros, and its applications in the design of decentralized controllers for linear time-invariant finite-dimensional systems. The concept of decentralized blocking zeros is a generalization of its centralized counterpart to multichannel systems under decentralized control. Decentralized blocking zeros are defined as the common blocking zeros of the main diagonal transfer matrices and various complementary transfer matrices of a given plant. As an application of this concept, we consider the decentralized strong stabilization problem (DSSP) where the objective is to stabilize a plant using a stable decentralized controller. It is shown that a parity interlacing property should be satisfied among the real unstable poles and real unstable decentralized blocking zeros of the plant for the DSSP to be solvable. That parity interlacing property is also sufficient for the solution of the DSSP for a large class of plants satisfying a certain connectivity condition. The DSSP is exploited in the solution of a special decentralized simultaneous stabilization problem, called the decentralized concurrent stabilization problem (DCSP). Various applications of the DCSP in the design of controllers for large-scale systems are also discussed     

Centralized and decentralized asynchronous optimization ofstochastic discrete-event systems

We propose and analyze centralized and decentralized asynchronous control structures for the parametric optimization of stochastic discrete-event systems (DES) consisting of K distributed components. We use a stochastic approximation type of optimization scheme driven by gradient estimates of a global performance measure with respect to local control parameters. The estimates are obtained in distributed and asynchronous fashion at the K components based on local state information only. We identify two verifiable conditions for the estimators and show that if they, and some additional technical conditions, are satisfied, our centralized optimization schemes, as well as the fully decentralized asynchronous one we propose, all converge to a global optimum in a weak sense. All schemes have the additional property of using the entire state history, not just the part included in the interval since the last control update; thus, no system data are wasted. We include an application of our approach to a well-known stochastic scheduling problem and show explicit numerical results using some recently developed gradient estimators