Showing papers in "IEEE Transactions on Industrial Informatics in 2006"

Semantic web services in factory automation: fundamental insights and research roadmap

Abstract: One of the significant challenges for current and future manufacturing systems is that of providing rapid reconfigurability in order to evolve and adapt to mass customization. This challenge is aggravated if new types of processes and components are introduced, as existing components are expected to interact with the novel entities but have no previous knowledge on how to collaborate. This statement not only applies to innovative processes and devices, but is also due to the impossibility to incorporate knowledge in a single device about all types of available system components. This paper proposes the use of Semantic Web Services in order to overcome this challenge. The use of ontologies and explicit semantics enable performing logical reasoning to infer sufficient knowledge on the classification of processes that machines offer, and on how to execute and compose those processes to carry out manufacturing orchestration autonomously. A series of motivating utilization scenarios are illustrated, and a research roadmap is presented.

Two-Stage Method for Synthesizing Liveness-Enforcing Supervisors for Flexible Manufacturing Systems Using Petri Nets

Abstract: This paper develops a two-stage approach to synthesizing liveness-enforcing supervisors for flexible manufacturing systems (FMS) that can be modeled by a class of Petri nets. First, we find siphons that need to be controlled using a mixed integer programming (MIP) method. This way avoids complete siphon enumeration that is more time-consuming for a sizable plant model than the MIP method. Monitors are added for only those siphons that require them. Second, we rearrange the output arcs of the monitors on condition that liveness is still preserved. The liveness is verified by an MIP-based deadlock detection method instead of much time-consuming reachability analysis. Experimental studies show that the proposed approach is more efficient than the existing ones and can result in more permissive and structurally simpler liveness-enforcing supervisors than all the known existing methods. This paper makes the application of siphon-based deadlock control methods to industrial-size FMS possible

On the use of wireless networks at low level of factory automation systems

Abstract: Wireless communication systems are rapidly becoming a viable solution for employment at the lowest level of factory automation systems, usually referred to as either "device" or "field" level, where the requested performance may be rather critical in terms of both transmission time and reliability. In this paper, we deal with the use of wireless networks at the device level. Specifically, after an analysis of the communication requirements, we introduce a general profile of a wireless fieldbus. Both the physical and data link layers are taken directly from existing wireless local area networks and wireless personal area networks standards, whereas the application layer is derived from the most popular wired fieldbuses. We discuss implementation issues related to two models of application layer protocols and present performance results obtained through numerical simulations. We also address some important aspects related to data security and power consumption.

Application of neural networks in optical inspection and classification of solder joints in surface mount technology

Abstract: The defect detection on manufactures is extremely important in the optimization of industrial processes; particularly, the visual inspection plays a fundamental role. The visual inspection is often carried out by a human expert. However, new technology features have made this inspection unreliable. For this reason, many researchers have been engaged to develop automatic analysis processes of manufactures and automatic optical inspections in the industrial production of printed circuit boards. Among the defects that could arise in this industrial process, those of the solder joints are very important, because they can lead to an incorrect functioning of the board; moreover, the amount of the solder paste can give some information on the quality of the industrial process. In this paper, a neural network-based automatic optical inspection system for the diagnosis of solder joint defects on printed circuit boards assembled in surface mounting technology is presented. The diagnosis is handled as a pattern recognition problem with a neural network approach. Five types of solder joints have been classified in respect to the amount of solder paste in order to perform the diagnosis with a high recognition rate and a detailed classification able to give information on the quality of the manufacturing process. The images of the boards under test are acquired and then preprocessed to extract the region of interest for the diagnosis. Three types of feature vectors are evaluated from each region of interest, which are the images of the solder joints under test, by exploiting the properties of the wavelet transform and the geometrical characteristics of the preprocessed images. The performances of three different classifiers which are a multilayer perceptron, a linear vector quantization, and a K-nearest neighbor classifier are compared. The n-fold cross-validation has been exploited to select the best architecture for the neural classifiers, while a number of experiments have been devoted to estimating the best value of K in the K-NN. The results have proved that the MLP network fed with the GW-features has the best recognition rate. This approach allows to carry out the diagnosis burden on image processing, feature extraction, and classification algorithms, reducing the cost and the complexity of the acquisition system. In fact, the experimental results suggest that the reason for the high recognition rate in the solder joint classification is due to the proper preprocessing steps followed as well as to the information contents of the features

Timeliness of real-time IP communication in switched industrial Ethernet networks

Abstract: Through several giant evolutionary steps, Ethernet has become an almost ubiquitous technology for communication. Being versatile enough to be employed in new and various fields of application, it is now making inroads in factories. However, automated systems are different from many other applications of Ethernet,first and foremost because they require the network technology to deliver real-time performance. In the present study, a number of critical aspects of Ethernet, usually referred to as an Industrial Ethernet, are examined. More specifically, there is a focus on the application-to-application delay and jitter characteristics of such networks, when using Internet protocols such as UDP and TCP. It is demonstrated how important it is to take control of the latency in the station nodes, since the main communication delays occur inside the nodes, and different solutions are presented for controlling these delays. In particular, a priority-based protocol stack is assessed. The results show that real-time, Ethernet-based IP communication is now adequate even for demanding automated applications. In this paper, substation automation (power distribution) is used as an example of a demanding automation system.

Vertical integration of enterprise industrial systems utilizing web services

Abstract: The need for interoperability is prominent in the industrial enterprise environment. Different applications and systems that cover the overall range of the industrial infrastructure from the field to the enterprise level need to interoperate. This quest is driven by the enterprise need for greater flexibility and for the wider possible integration of the enterprise systems. This paper presents a distributed system architecture that utilizes dominant state-of-the-art standard technologies, such as workflows, ontologies, and web services, in order to address the above quest in an efficient way.

Network architecture and communication modules for guaranteeing acceptable control and communication performance for networked multi-agent systems

Abstract: When sensory and actuation devices in a control system are exchanging data through one common communication medium, the sharing of communication bandwidth will induce unavoidable data latency and might degrade the control performance. Hence, the utilization of communication resource and the requirement of control specification should be analyzed and properly designed when implementing a control system over a network architecture. In this paper, we analyze the performance of information sharing of multiple cooperative agents over one communication network, and propose design methodologies of guaranteeing acceptable control and communication performance in a networked control system. In particular, we study the relationship between the sampling rates of a control system,and the transmission rates of a communication network, and then utilize an integrated networked control design chart to help select design parameters and visualize overall system performance at different sampling and transmission rates. Based on the design parameters selected, the communication modules by utilizing deadband control and state estimation are presented for guaranteeing both control and communication performance. Simulation studies are conducted in a network-and-control simulation tool that is developed on the Matlab/Simulink platform and is used to demonstrate the proposed design methodologies. Both the analysis and simulation results illustrate the characteristics of designing mechanisms between control and communication performance and show the improvement of implementing the proposed communication modules.

Combustion efficiency optimization and virtual testing: a data-mining approach

Abstract: In this paper, a data-mining approach is applied to optimize combustion efficiency of a coal-fired boiler. The combustion process is complex, nonlinear, and nonstationary. A virtual testing procedure is developed to validate the results produced by the optimization methods. The developed procedure quantifies improvements in the combustion efficiency without performing live testing, which is expensive and time consuming. The ideas introduced in this paper are illustrated with an industrial case study

An active star topology for improving fault confinement in CAN networks

Abstract: The controller area network (CAN) is a field bus that is nowadays widespread in distributed embedded systems due to its electrical robustness, low price, and deterministic access delay. However, its use in safety-critical applications has been controversial due to dependability limitations, such as those arising from its bus topology. In particular, in a CAN bus, there are multiple components such that if any of them is faulty, a general failure of the communication system may happen. In this paper, we propose a design for an active star topology called CANcentrate. Our design solves the limitations indicated above by means of an active hub, which prevents error propagation from any of its ports to the others. Due to the specific characteristics of this hub, CANcentrate is fully compatible with existing CAN controllers. This paper compares bus and star topologies, analyzes related work, describes the CANcentrate basics, paying special attention to the mechanisms used for detecting faulty ports, and finally describes the implementation and test of a CANcentrate prototype.

Automatic fuzzy ontology generation for semantic help-desk support

Abstract: Customer service support is an important operation for most multinational manufacturing companies. With the advancement of internet technologies, customer services nowadays are supported through web-based systems. More recently, rapid development of the semantic web and semantic web services has prompted us to develop a semantic help-desk for supporting customer services over the semantic web environment, which is presented in this paper. In particular, a fuzzy formal concept analysis (FCA)-based approach is developed for automatic generation of fuzzy machine service ontology that can deal with uncertain information. The proposed automatic fuzzy ontology generation technique consists of the following steps: fuzzy formal concept analysis, fuzzy conceptual clustering, and ontology generation. As such, the supporting machine services provided by the proposed system will potentially improve customer satisfaction in terms of reducing machine down time and increasing productivity. In this paper, an experiment has also been conducted for performance evaluation. The experimental result shows that the proposed approach has attained good performance in terms of both accuracy and efficiency when the queries are associated with appropriate membership values, and a suitable confident threshold is set

Service-Oriented Architecture for Distributed Publish/Subscribe Middleware in Electronics Production

Abstract: The Computer Aided Manufacturing using XML (CAMX) framework enables integrating electronics production systems using message-oriented middleware, offering standards-based communication among machines and control software applications. CAMX frameworks implement publish/subscribe of XML messages through an entity called the message broker (MSB), which provides the messaging service using a web-based interface. A challenge for MSB-based systems is that they must scale to handle large volumes of messaging traffic, which is a characteristic of modern information-intensive manufacturing systems. This paper first tackles this challenge by presenting an array of architecture patterns for creating distributed MSB frameworks, focusing mainly on globally distributed federations and locally distributed clusters. A unified architecture is subsequently presented that leverages the different patterns by combining federated frameworks with locally distributed clusters into a unified set of architecture elements and interactions. A service-oriented approach is followed to provide a uniform interface for distributed MSB elements, whether federated or locally distributed. The service-oriented approach is also used to dynamically discover resources and automatically invoke the (re)configuration and messaging services. The services are enriched with semantics in order to facilitate automatic discovery and selection of services using the semantic web services formal ontology. Semantic service advertisements are propagated using a peer-to-peer discovery protocol. The approach presented in this paper is not limited to the CAMX case and is generally applicable to distributed event-based manufacturing systems

Pervasive grid for large-scale power systems contingency analysis

Abstract: Optimal control and management of power systems require extensive analyses of phenomena that can compromise their operation in order to evaluate their impact on the security and reliability levels of the electrical networks. For complex networks, this process, known as power systems contingencies analysis, requires large computational efforts, whereas computation times should be less than a few minutes for the information to be useful. Even though many architectures based on conventional parallel and distributed systems have been widely proposed in the literature, they are characterized by low extensibility, reusability, and scalability, and so, they require a sensible hardware upgrade when more computational resources are necessary. This event is not infrequent in power systems where the constant growth of the electrical network complexity and the need for larger security and reliability levels of the plant infrastructures lead to the need of more detailed contingency analysis in shorter times. To address this problem, this paper proposes a pervasive grid approach to define a user-friendly software infrastructure for data acquisition from electrical networks and for data processing in order to simulate possible contingencies in a real electrical network. The grid infrastructure adopts a brokering service, based on an economy-driven model, to satisfy the quality of service constraints specified by the user (i.e., a time deadline to simulate the contingencies). This paper also discusses the deployment of the infrastructure on a network of heterogeneous clusters and PCs to compute the contingency analysis of a realistic electrical network. The experimental results obtained demonstrate the effectiveness of the proposed solution and the potential role of grid computing in supporting intensive computations in power systems

Combining operational flexibility and dependability in FTT-CAN

Abstract: The traditional approaches to the design of distributed safety-critical systems, due to fault-tolerance reasons, have mostly considered static cyclic table-based traffic scheduling. However, there is a growing demand for operational flexibility and integration, mainly to improve efficiency in the use of system resources, with the network playing a central role to support such properties. This calls for dynamic online traffic scheduling techniques so that dynamic communication requirements are adequately supported. Nevertheless, using dynamic traffic management mechanisms raises additional problems, in terms of fault-tolerance, related with the weaker knowledge of the future system state caused by the higher level of operational flexibility. Such problems have been recently addressed in the scope of using flexible time-triggered CAN (FTT-CAN) in safety-critical applications in order to benefit from the high operational flexibility of this protocol. This paper gathers and reviews the main mechanisms that were developed to provide dependability to the protocol, namely, master replication and fail-silence enforcement.

Providing Real-Time Applications With Graceful Degradation of QoS and Fault Tolerance According to $(m, k)$ -Firm Model

Abstract: The $(m, k)$ -firm model has recently drawn a lot of attention. It provides a flexible real-time system with graceful degradation of the quality of service (QoS), thus achieving the fault tolerance in case of system overload. In this paper, we focus on the distance-based priority (DBP) algorithm as it presents the interesting feature of dynamically assigning the priorities according to the system's current state (QoS-aware scheduling). However, DBP cannot readily be used for systems requiring a deterministic $(m, k)$ -firm guarantee since the schedulability analysis was not done in the original proposition. In this paper, a sufficient schedulability condition is given to deterministically guarantee a set of periodic or sporadic activities (jobs) sharing a common non-preemptive server. This condition is applied to two case studies showing its practical usefulness for both bandwidth dimensioning of the communication system providing graceful degradation of QoS and the task scheduling in an in-vehicle embedded system allowing fault tolerance.

On the properties of the flexible time division multiple access technique

Abstract: Flexible time division multiple access (FTDMA) is a medium access mechanism that some modern popular networks for use in passenger vehicles, such as Byteflight and FlexRay, rely on. Its development was driven explicitly by the new needs of automotive x-by-wire systems, which could not be satisfied by the existing solutions. The FTDMA technique was conceived primarily to overcome the limitations of controller area network and, in particular, for supporting high performance real-time communications. Even though this access scheme is mainly suitable for asynchronous transmissions, it can be adopted profitably for synchronous exchanges as well. In this paper, the main features of FTDMA are analyzed, and its performance is evaluated for different kinds of communications that have to be supported in today's vehicles.

Web-based command shaping of cobra 600 robot with a swinging load

Abstract: This work focuses on the real-time control of a swinging load through the Internet In particular, command shaping is applied to move a cable suspended load at the end point of an Adept Cobra 600 4-axis SCARA robot, with the objective of minimizing load swing The first part of this paper discusses inverse kinematics,pendulum dynamics calculations, the corresponding shaping control algorithm,and the effects of transmission time delay Standardized Internet interface via the DataSocket software in LabVIEW is then addressed in the second part Simulation and experimental results confirm the feasibility of real time command shaping control through the Internet

Reuse of CAN-Based Legacy Applications in Time-Triggered Architectures

Abstract: Upcoming car series will be deployed with time-triggered communication protocols due to benefits with respect to bandwidth, predictability, dependability, and system integration. In present day automotive networks, controller area network (CAN) is the most widely used communication protocol. Today, up to five CAN buses and several private CAN networks result from the bandwidth limits of CAN in conjunction with constraints concerning bus utilization aimed at controlling transmission latencies. In this context, the upcoming introduction of time-triggered networks into series production offers the potential to reduce the number of CAN networks by exploiting the high bandwidth of the time-triggered network instead of CAN buses. Due to the elimination of CAN buses, the resulting reduction of wiring and connectors promises a significant reduction in hardware cost and reliability improvements. In order to support the reuse of existing CAN-based application software, this paper presents a solution for the emulation of a CAN communication service on top of an underlying time-triggered network. By providing to CAN-based applications the same interface as in a conventional CAN system, redevelopment efforts for CAN-based legacy software are minimized. For this purpose, a CAN emulation middleware operates between a operating system and the CAN-based applications. In a first step, the middleware establishes event channels on top of the communication network in order to support on-demand transmission requests at a priori unknown points in time. The middleware then emulates the carrier sense multiple access collision avoidance (CSMA/CA) media access protocol of a physical CAN network for passing messages received via event channels to the application in the correct temporal order. Finally, the application programming interface (API) of the widely used HIS/VectorCAN driver provides a handle-based programming interface with support for message filtering and callbacks. A validation setup with a time-triggered protocol (TTP) cluster demonstrates that the CAN emulation can handle CAN-based legacy software and a real-world communication matrix provided by the automotive industry

Network Traffic Model for Industrial Environment

Abstract: In this paper, a model of LAN traffic is presented. In the model, the most important components influencing the network traffic are taken into account. Namely, the transmission protocols and information buffering, operating systems, and queuing algorithms as well as user behavior in network applications are considered. The model is based on an "on-off" function. The network traffic observed at the physical layer is a superposition of many sequential and self-similar "on-off" processes. It has been shown that the self-similarity of the traffic, measured by the Hurst parameter, changes from almost 1.0 for very low frequencies to 0.5 for high frequencies

Energy-efficient and intrusion-resilient authentication for ubiquitous access to factory floor information

Abstract: Linking factory floors to the Internet, coupled with the rapid deployment of wireless access networks, is initiating a new paradigm for factory automation-a corporate employee with a handheld computing device can have anytime, anywhere access to the latest factory floor information. Authentication between a factory database and a remote user is crucial for such paradigm; however, existing authentication protocols are inadequate to defend against strong adversaries with break-in capabilities. In this paper, we design and implement the Energy-Efficient and Intrusion-Resilient Authentication (ERA) protocol. Through a novel combination of hash chain,pin, and message authentication code (MAC), ERA can achieve the security self-recovery when strong adversaries compromise either a user's handheld device or a factory authentication server to obtain the authentication secrets. The technique of mutual MAC is proposed to defend against online pin-guessing attacks launched by strong adversaries. Furthermore, an optimization of tuning hash chain iteration is introduced to reduce energy consumption of a handheld device. Analytical and experimental results show that ERA provides a better security guarantee and incurs much less computation and communication overhead than the existing authentication protocols.

Early order completion contract approach to minimize the impact of demand uncertainty on supply chains

Abstract: Many optimization techniques have been proposed over the years to improve the performance of supply chains. Although these approaches have been shown to be effective, most of them were developed without considering uncertainties in supply chains to simplify the analysis. In fact, uncertainties can deteriorate the performance of supply chains, such as increase in total cost, or drop in fill rate, of the whole system. In distributed supply chains, participating members are not under a sole control by a central authority, the problem is even more stringent due to incomplete information sharing, or so called asymmetrical information sharing. One way to improve the system performance is to achieve coordination among participating parties through establishment of contracts. The objectives of this paper are i) to evaluate the effects of demand uncertainty in a distributed supply chain, which is modelled as an agent-based system; ii) to propose a coordination mechanism with early order completion contract to minimize the negative impacts of demand uncertainty; and iii) to present associated simulation results. Performance of the system is measured in terms of costs and fill rate. Simulation results indicate that the proposed contract approach is able to improve the performance measures of the system.

Automated modeling and analysis of CSMA-type access schemes for building automation networks

Abstract: During the design of large technical systems, the use of analytic and simulative models to test and dimension the system before implementation is of practical importance for an efficient and reliable design process. However, setting up the necessary models is time-consuming and therefore often too expensive in practice. Usually most information for modeling is already available in the design tool used to develop such extensive systems and only needs to be extracted for automatic model building. This paper presents an automated modeling approach from an existing design database using the example of a network analysis for building automation fieldbuses. The analysis is based on an analytical decomposition approach that enables fast estimation of performance measures for large-scale networks. The combination of fast analytical algorithms with automatic model generation allows network performance engineering with minimized effort for model generation and analysis.

Time-triggered smart transducer networks

Abstract: The time-triggered approach is a well-suited approach for building distributed hard real-time systems. Since many applications of transducer networks have real-time requirements, a time-triggered communication interface for smart transducers is desirable; however, such a time-triggered interface must still support features for monitoring, maintenance, plug-and-play, etc. The approach of the Object Management Group (OMG) Smart Transducer Interface consists of clusters of time-triggered smart transducer nodes that contain special interfaces supporting configuration, diagnostics, and maintenance, without affecting the deterministic real-time communication. This paper discusses the applicability of the time-triggered approach for smart transducer networks and presents a case study application of a time-triggered smart transducer network

A novel approach toward integration of rules into business processes using an agent-oriented framework

Abstract: Every action a business process performs must be explicitly anticipated, designed for, and implemented by business professionals. The business process is dependent upon business rules (BRs) to achieve its objectives, which also involve pre- and post-conditions in the business process (BP). Most of the current techniques implement these rules directly into BPs. This will result in the BP becoming even more complicated and harder to customize. Most BRs (and laws) are buried in data warehouses as raw data. Incorporating the BRs into any BP is very complex, in terms of customization, reuse, and system integration. To overcome this problem, we propose and implement an agent-oriented framework. Using this framework, we can make the process of incorporating BR into BP less complex. The agent creates a bridge between components of the business structure, the BRs, and the BP. The BP consists of activities and sub-activities. The agent is able to communicate with BP and BRs to execute a BP. The agent can also communicate with other agents and have control over their own internal states and behavior. In this paper, we propose and implement a simple case study to execute a BP dependent upon BRs. The case study shows how the agent will synchronize, integrate, and deploy the BP

Development of Bluewave: A Wireless Protocol for Industrial Automation

Abstract: There is a growing trend in developing the wireless machine-to-machine (M2M) communication for factory automation. Currently, most wireless protocols for infrastructureless mobile ad-hoc networks focus on the mobility issue and are mainly suitable for narrowband radio devices. The mechanisms for route update and discovery that work well for wireless mobile ad-hoc networks prove to be redundant and instead add to processing overheads in a static wireless factory setting. This paper presents the development and implementation of a new wireless routing protocol, Bluewave, that caters specifically to wireless communication between machines in a factory setting. Bluewave utilizes features of Bluetooth technology when performing the route setup. The merits of the proposed protocol, in terms of shorter initialization time and route setup time, are duly discussed. A case study illustrating the application of Bluewave to an online condition-based maintenance scenario is presented. Experimental results obtained are furnished to show the viability of Bluewave in industrial automation

Development of a Profit-Based Air Cargo Loading Information System

Abstract: In today's competitive logistics business environment, airfreight forwarders need to optimize every aspect of their logistics operations. However, forwarders still heavily rely on human brain and working experiences for calculating complex cargo packing and scheduling problems. Although recent research studies related to cargo packing and scheduling problems have resulted in the development of a number of advanced techniques of cargo planning, it can be seen that most of the research work is focused on the optimization of space in order to achieve the maximum possible amount of cargo to be packed in the minimum of space. After numerous site evaluation and end-user feedbacks, it is found that space optimization does not necessarily cause profit optimization, which is the ultimate aim of logistics providers. A study of contemporary research publications indicates that there are inadequate research studies related to profit-based optimization in cargo packing areas. This paper presents a profit-based air cargo loading information system (ACLIS) that embeds an innovative technology known as heuristics iterative reasoning technology (HIRT) that supports loading plan generation, focusing on maximization of the profit margin. In general, the proposed system is meant to maximize the profit in the airfreight forwarding business. It adopts an objective function governed by a list of constraints together with rule-based reasoning to provide expert advice to support the generation of appropriate loading plans

Interactive Consistency on a Time-Triggered Real-Time Control Network

Abstract: Current and emerging safety-critical applications such as the automotive X-by-wire systems require a high degree of reliability. These dependable embedded distributed systems require an ultra-reliable communication system to exchange data between the distributed components. In addition to guaranteeing a high level of reliability, these communication systems should facilitate the development of fault-tolerant applications. This can be achieved by providing additional communication system services such as interactive consistency. Interactive consistency on a communication system can be defined as a means to ensure that all non-faulty nodes on the communication system receive a consistent value for any message communicated. This paper describes the adoption of an explicit interactive consistency algorithm on a time-triggered broadcast communication system, using a shared communication medium. This is supported by the development of a prototype implementation of the interactive consistency algorithm. This prototype system demonstrates that interactive consistency is successfully achieved in the presence of a number of faults

Applying and adapting the IEC 61346 standard to industrial automation applications

Abstract: The IEC 61346 standard describes a reference designation system for identifying the objects and structuring the information of virtually any kind of technical system. The generality of the standard leads in some cases to a slightly loose definition of its concepts, which can hamper its applicability to a concrete domain. Our aim is to make the IEC 61346 standard suitable for the construction of reference designations of industrial plants. Therefore, we impose some constraints to the standard and define the process to follow in order to apply it to industrial automation applications. The removal of ambiguities should also facilitate the interoperability of computer implementations of the standard coming from different vendors. Finally, we show as well how to combine IEC 61346 to existing standards on enterprise-control system integration

Analysis of a Software-Focused Products and Service Supply Chain

Abstract: In this paper, we study a software-focused products and service supply chain based on the practice of two leading electronic manufacturing services providers in the world and their major corporate clients We discuss the common and unique issues that a software-focused supply chain has compared with a traditional supply chain We also indicate the research challenges and opportunities for a software-focused supply chain

Coordinating Agents in Shop Floor Environments From a Dynamic Systems Perspective

Abstract: In this paper, we address agent coordination from a dynamic systems perspective and propose a dynamic coordination model, which is inspired by biological metabolic systems. A new coordination mechanism through dynamic local adjustment (CDLA) is presented, and coordination is achieved when every agent utilizes explicitly the global system dynamics and performs iteratively a dynamic local adjustment procedure. The CDLA mechanism is investigated in an example multiagent shop floor system. The results show that the example manufacturing process is well-coordinated and the coordination approach is practically applicable and effective

Performance Analysis of a Real-Time Control Network Test Bed in a Linux-Based System With Sporadic Message Arrivals

Abstract: This paper describes the results from a real-time network test bed for a Linux-based control system with event-driven message traffic. Interest has grown in the use of Linux as a cost-effective alternative to expensive proprietary real-time operating systems. However, kernel tasks in Linux can cause random delays in message transmissions. Event-driven traffic can result in unpredictable message inter-arrival rates. Nondeterministic delays in message transmissions and sporadic message arrival times complicate the design of the network as they require the use of an estimation technique to analyze feasibility. Random temporal behavior can lead to network overloads, where it becomes unavoidable that some messages will be late. We discuss the design and feasibility analysis for the network and evaluate the network's performance in the presence of random kernel delay and sporadic message arrivals. Three message scheduling approaches are evaluated using different Linux configurations at different levels of network loading