An architecture for real-time distributed artificial intelligent systems

This paper introduces a new architecture for a real-time distributed artificial intelligence system: DENIS—a Dynamic Embedded Noticeboard Information System. The fundamental idea underlying the architecture draws heavily upon a distributed human system analogy, as seen, for example, in the workplace. The aim of DENIS is to provide a simple, meaningful means by which autonomous intelligent agents can cooperate and coordinate their actions in order to enhance the reliability and effectiveness of a real-time distributed control system. Based on a human paradigm, the architecture inherently allows for the control of an intelligent agent to be taken over by a human operator, yet still to maintain consistency in the distributed system. The key to the thinking in this new approach is to try to model how humans work together, and to implement this in a distributed architecture. One of the main issues raised is that humans owe much of their flexibility to their ability to reason, not only logically, but also in terms of time.     

A Real-Time Interprocessor Synchronization Algorithm for Communication in Distributed Computer Systems

A real-time synchronization algorithm for interprncessor communication ispresented, which is based on the techniques of Reference 2, except that bufferedcommunication is used. The upper and lower bounds of the mean response time of thisalgorithm is derived.     

MININET: A local area network for real-time instrumentation applications

MININET is a local network designed primarily for support of high-speed instrumentation. This highly transparent multi-media network, now operational in an initial prototype form, employs packet-switching techniques and has many features which make it an attractive data transport mechanism for connecting digital instrumentation and control equipment to minicomputer and microcomputer hosts.The overall philosophy and organization of the network are described and details of the protocols and procedures adopted are given. Discussion of hardware and software developments is included and plans for solution of routing and flow control problems in this environment with its inherently sequential subnet delivery demands are outlined.     

A computer network based control architecture for autonomous distributed multirobot systems

This paper presents the specification and implementation procedure using a microcomputer network based autonomous distributed control architecture for industrial multirobot systems. The procedure is based on the concept of data flow network controlled by communicating sequential processes to perform coordinated tasks. Robots and other computerized industrial devices such as conveyors and manufacturing machines are defined as object-oriented Petri nets. A modular and hierarchical approach is adopted to define a set of Petri net type diagrams which represent concurrent activities of control processes for such devices. Asynchronous and synchronous interactions are modelled by places and transitions, respectively, in global process interaction nets. The control software is implemented on a computer network using Inmos transputers with true parallel processing and message passing primitives efficiently handled in hardware. Petri net based models are directly and efficiently transformed to corresponding codes in occam, the high level parallel programming language defined for the transputer.     

A Graphics System Distributed across a Local Area Network

Design of a general purpose graphics system in a computer network environment requiresthat the architectural design of the graphics system be suited to such an environment and theadvantages of the network environment be taken for distributed graphics processing and thesharing of resources. An architectural model is designed to meet these requirements. The modelis characterised by the distribution on the machines in the network of graphics facilitiesprovided by several graphics subsystems with various capabilities but compatible functionality,and the distributed processing of graphics across the network. This design structure has beenshown to be viable by using it as the basis for the implementation of the graphics system for theMU6G network at University of Manchester. The design methodology and the structure of thegraphics system are described in the paper.     

DIPCS: An interprocess communication architecture for distributed multimedia systems

This paper presents the Distributed InterProcess Communication System (DIPCS) as a framework for managing communication in a distributed multimedia system. Within DIPCS, connection level management is provided through a novel distributed process group model called ADP-Group communication. The ADP-Group paradigm defines a new type of group message passing, calledqos-reliable. Qos-reliable semantics are appropriate to controlling real-time multimedia communication, by allowing a spectrum of performance and reliability specifications to co-exist within one group. DIPCS also provides an abstract programming model of multimedia devices, easing control of a heterogeneous multimedia system. Distributed multimedia applications can be rapidly developed using simple group operation primitives. We show how ADP-Group message delivery semantics can be directly mapped into an efficient Integrated Services Network support policy.Supported by Computational Diagnostics, Inc., and the Benjamin Franklin Fund for the Commonwealth of Pennsylvania.Supported by the Rome Laboratory (RL) of the Air Force Material Command and the Defense Advanced Research Projects Agency (Contract F30602-93-C-0038).     

网络实时通讯的一种解决方案

本文介绍了利用以太网进行通讯的一种解决方案。该方案充分利用了嵌入式实时操作系统强实时性和稳定性及Windows操作系统强大的功能，提供了利用两种互补和协同工作的操作系统完成实时网络通讯新的思路。     

RealNet: a neural network architecture for real-time systems scheduling

Real-time embedded systems are spreading to more and more new fields and their scope and complexity have grown dramatically in the last few years. Nowadays, real-time embedded computers or controllers can be found everywhere, both in very simple devices used in everyday life and in professional environments. Real-time embedded systems have to take into account robustness, safety and timeliness. The most-used schedulability analysis is the worst-case response time proposed by Joseph and Pandya (Comput J 29:390–395,1986). This test provides a bivaluated response (yes/no) indicating whether the processes will meet their corresponding deadlines or not. Nevertheless, sometimes the real-time designer might want to know, more exactly, the probability of the processes meeting their deadlines, in order to assess the risk of a failed scheduling depending on critical requirements of the processes. This paper presents RealNet, a neural network architecture that will generate schedules from timing requirements of a real-time system. The RealNet simulator will provide the designer, after iterating and averaging over some trials, an estimation of the probability that the system will not meet the deadlines. Moreover, the knowledge of the critical processes in these schedules will allow the designer to decide whether changes in the implementation are required.This revised version was published online in November 2004 with a correction to the accepted date.     

A middleware architecture for distributed systems management

This paper presents a middleware solution for global management of any kind of distributed system, such as networks of PCs/workstations, clusters or server farms. Our approach lies in an object-oriented software architecture that models all kind of management information using the common information model (CIM) developed by the Distributed Management Task Force (DMTF). The classes and attributes obtained after the modeling process are mapped to a Lightweight Directory Access Protocol (LDAP) repository. This paper discusses the key features of our middleware that allows that any element (physical, logical, device, user or system) can be managed using a network-oriented and topology-independent approach. A representative example of management domain illustrates the procedures followed to build management applications using our middleware architecture.     

Banet — a local area network for distributed data processing

A broadcast architecture network (Banet) suitable for distributed data processing is proposed. One feature of Banet is that the broadcast-within-a-group function is supported not only by the datalink level but by the transport or session-level network structure. The commitment control scheme is included in the network protocol. Design goals, physical structure and protocols are discussed.     

An architecture for Java-based real-time distributed visualization

In this paper, we present a Java-based software architecture for real-time visualization that utilizes a cluster of conventional PCs to generate high-quality interactive graphics. Normally, a large multiprocessor computer would be needed for interactive visualization tasks requiring more processing power than a single PC can provide. By using clusters of PCs, enormous cost savings can be realized, and proprietary "high-end" hardware is no longer necessary for these tasks. Our architecture minimizes the amount of synchronization needed between PCs, resulting in excellent scalability. It provides a modular framework that can accommodate a wide variety of rendering algorithms and data formats, provided that the rendering algorithms can generate pixels individually and the data is duplicated on each PC. Demonstration modules that implement ray tracing, fractal rendering, and volume rendering algorithms were developed to evaluate the architecture. Results are encouraging-using 15 PCs connected to a standard 100 Megabit/s Ethernet network, the system can interactively render simple to moderately complex data sets at modest resolution. Excellent scalability is achieved; however, our tests were limited to a cluster of 15 PCs. Results also demonstrate that Java is a viable platform for real-time distributed visualization.     

面向网络通信的高实时压缩引擎设计

随着集成电路工艺的发展,高性能计算系统中互连网络性能提升速度远低于处理器性能的提升,互连网络带宽已成为制约高性能计算性能提高的瓶颈之一。从减少网络注入数据量的角度出发,对网络通信实时压缩技术进行了研究,给出了一种面向网络通信的硬件实时压缩引擎RTCE的设计,在网络通信过程中,硬件自动实现对网络包的压缩传输。采用SPEC2006、Graph500、CFD算法测试数据进行测试,压缩后的网络包数据量平均减少32.8%~48.7%。     

A priori error estimates for wireless local area network positioning systems

Location determination based on wireless local area networks has received considerable attention as an accurate and inexpensive means of indoor positioning. Research on this topic has mainly focused on experimental systems while little has been done to model and analyse the problem. Yet, analytical models are essential for understanding the influence of system parameters and a system’s overall behaviour. This article introduces two analytical models that can provide pessimistic and optimistic estimates for the location error in a given environment. The findings are compared to measurements and simulations of a probabilistic Wireless LAN positioning system.     

A parallel distributed control architecture for multiple robot systems using a network of microcomputers

This paper presents the design and implementation of a parallel distributed control architecture for industrial multiple robot systems. The design methodology is based on a concept of discrete states and actions, and a robotic task is represented as a sequence of primitive actions. For cooperative or exclusive tasks at the synchronous level of multiple robot systems, Petri net representation is applied, and discrete event-driven control is implemented as a data flow network of concurrent processes communicating with each other. Implementation of multiprocessing control on a microcomputer and a network of microcomputers is discussed.     

A software architecture for distributed computer control systems

Distributed computer control systems have a number of potential advantages over centralized systems, especially where the application is itself physically distributed. A computer station can be placed close to the plant being controlled, and a communications network used to enable the stations to communicate to coordinate their actions. However, the software must be carefully designed to exploit the potential advantages of distribution. This paper describes the software architecture of CONIC, a system to support distributed computer control applications. This architecture emphasizes the distinction between the writing of individual software components and the construction and configuration of a system from a set of components. A modular structure is used to separate programming from configuration. Typed entry and exit ports are used to clearly define module interfaces. Ports, analagous to the plugs and sockets of hardware components, permit modules to be interconnected in different ways. On-line modification and extension of the system is supported by permitting the dynamic creation and interconnection of modules. Message passing primitives are provided to permit modules to coordinate and synchronize control actions.     

A predictable real-time kernel for distributed multisensor systems

The authors present a real-time kernel developed to support a distributed multisensor system encountered in robotics applications. To ensure predictability, the kernel provides services with bounded worst-case execution times. In addition, the kernel allows the programmer to specify timing constraints for process execution and interprocess communication. The kernel uses these timing constraints both for scheduling processes and for scheduling communications. To illustrate the kernel, the authors describe a multisensor system being developed on their distributed real-time system. They present the measured performance of kernel primitives along with conclusions and remarks regarding distributed real-time systems     

Fault-tolerant real-time communication in distributed computingsystems

The delivery delay in a point-to-point packet switching network is difficult to control due to the contention among randomly-arriving packets at each node and multihops a packet must travel between its source and destination. Despite this difficulty, there are an increasing number of applications that require packets to be delivered reliably within prespecified delay bounds. This paper shows how this can be achieved by using real-time channels which make “soft” reservation of network resources to ensure the timely delivery of real-time packets. We first present theoretical results and detailed procedures for the establishment of real-time channels and then show how the basic real-time channels can be enhanced to be fault-tolerant using the multiple disjoint paths between a pair of communicating nodes. The contribution of the former is a tighter schedulability condition which makes more efficient use of network resources than any other existing approaches, and that of the latter is a significant improvement in fault tolerance over the basic real-time channel, which is inherently susceptible to component failures