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The limitation in maximum packet size of fieldbuses, is one of the characteristics that limit throughput in these networks. This restricts the range of multimedia applications viable over these infrastructures. In Ethernet, the limitation of 1500 bytes is currently being surpassed by the use of jumbo-frames, which offer a maximum frame size of 9 Kb, thus significantly improving the throughput of Ethernet...
In-vehicle embedded systems typically consist of a set of nodes exchanging applicative data ("signals") through a stack of communication protocols that includes a middleware layer. On each node, tasks, both applicative and middleware level, are subject to deadline constraints. Furthermore, signals must be produced sufficiently recently for being safely consumed on the receiver end (so-called...
OPC-XML defines a standard method for accessing automation data in the industry field. This protocol relies on Web service communications allowing a great compatibility and a software/hardware independent definition. Nevertheless, this underlying protocol does not take into account temporal Quality of Service. Therefore, when a contract is defined between the client and the server, its execution has...
This paper presents an architecture to build distributed embedded real-time systems in the RTLinux-GPL platform. The architecture (built in a layered fashion) has being built around open source projects ranging from Ethernet drivers to a CORBA environment. The paper focuses on those layers that give support for QoS and real-time networking over Ethernet networks. The main ideas are: to accomplish...
Today communication networks are more and more used to implement distributed applications concerned by closed loop process controls. These applications require a timeliness service in order to guarantee performances (stability, ...). The goal of this paper is, by considering a closed loop process control application with an open loop transfer function of the type G(s)=K/s(1+taus) (both no position...
This paper compares the fieldbus protocols LIN 1.3, LIN 2.07 and TTP/A to the requirements of low-cost body electronic networks in the automotive domain. The examined protocols all aim at distributed smart sensor/actuator networks and provide support for low-cost implementation on standard microcontroller nodes. LIN comes with a rigid specification of the physical layer in order to support interoperability...
This article covers research work about unmanned helicopters that is being developed by the Portuguese SME Introsys, S.A. in the context of a generic project targeting the development of a multi-robot system for landmine detection. As helicopters are complex multivariable nonlinear underactuated systems with strong coupling in some control loops, they are an interesting subject of research for the...
This paper describes the development of a multi-robot system for area reduction in humanitarian demining. In spite of the specific requirements imposed to the work being carried out by the humanitarian demining domain, the results being achieved can also be used in other domains such as surveillance and remote monitoring. A multi-agent based architecture is responsible for coordinating a progressive...
The X-by-Wire systems in cars can only be accepted if they provide at least the same dependability than the traditional ones. In this paper we propose a new approach to evaluate the impact of the EMI perturbations on the dependability of an X-by-Wire architecture. The considered X-by-Wire architecture is distributed around a TDMA-like communication protocol. So a perturbation causes the loss of a...
The current work focuses on the electronic collaboration among companies for the efficient execution of the shiprepair supply chain. The shiprepair supply chain is a dynamic environment that consists of collaborating companies, each one is specialized in a certain set of manufacturing activities. All these activities are interrelated and that are extremely complex to manage since the highest portion...
An adaptive algorithm for identification of the unknown parameters of the dynamic environment in contact tasks is proposed in this paper using the augmented least square estimation method. An approximate environment digital simulator for the continuous environment dynamics is derived, i.e. a discrete transfer function which has the approximately the same characteristics as the continuous environment...
This paper presents the planned and on-going activities inside the FORDESIGN research project, funded by the Portuguese FCT (Foundation for Science and Technology), whose main objective is to foster the effective use of formal methods for embedded systems co-design. The project proposes a methodology where the use-cases are used as a starting point, not only for capturing requirements but also to...
The introduction of the workflow management provided companies with a flexible and robust approach to the supervision and execution of the business process. A further question that must be addressed is to help companies in the reuse of already developed workflows, thus saving investments and reducing time-to-market. This paper proposes a methodology aiming at providing reuse and modularity for production...
The IEC 61499 (function block) standard proposes an open architecture for distributed industrial-process measurement and control systems (IPMCS). The IEC 61499 defines the basic concepts and methodology for the design of modular reusable distributable systems, and paves the way for the new reconfigurable and flexible manufacturing. This paper presents the development of a software tool (IEC 61499...
Event-based approaches are becoming more and more popular for building large scale distributed systems and applications, especially in the Internet environment. In this paper, the concept and techniques of event-based communications are first discussed. A hybrid approach of event-based communications for real-time manufacturing supervisory control is then proposed together with an "event-based...
The goal of the presented research is to face the topic of reconfigurable control software development in a concrete fashion, i.e., by presenting a control software system development approach which has been used for a specific, although easy to be generalized, robotized manufacturing cell component. In particular, a methodology for the control software development of a planar robot (2-degrees of...
The paper presents a modular control model to develop the control functions for manufacturing systems and its implementation using IEC 61499 function blocks. In particular, a new control module for automation objects is formally specified and its use on a hierarchical functional architecture has been discussed and the possible distribution of its IEC 61499 implementation is investigated. Finally,...
In this work the characteristics of the radio channel of a typical industrial environment are examined in detail by means of experimental measurements. The channel impulse response is measured at several representative positions. These measurements are then used to calculate important propagation parameters like attenuation, rms delay spread and coherence bandwidth. Furthermore, directional antennas...
This work presents constraint programming (CP) approach applied to determine deadlock-free schedules in concurrent production processes. The rules of resource conflict resolution have been expressed by means of a set of predicates, which define constraints for the problem decisive variables. Predicate model has been defined in time and event domains and implemented in procedures of propagating and...
Industrial communication systems (ICS) are specifically designed for deterministic communication between sensors, actuators, programmable logic controllers, monitoring systems, and operator workstations. These networks are traditionally based on wired technology and a deterministic medium access control. Nowadays, the emerging trend is the availability of wireless technology for ICS, since this leads...
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