| 1. |
- Adolfsson, Stefan, et al.
(författare)
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Automatic Detection of Burn-through in GMA Welding Using a Parametric Model
- 1996
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Ingår i: Mechanical Systems & Signal Processing. - London : Academic Press. - 0888-3270. ; 10:5, s. 633-651
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal are (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through-a broadband long-lasting voltage component-this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.
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| 2. |
- Adolfsson, Stefan, et al.
(författare)
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Quality Monitoring in Robotised Welding using Sequential Probability Ratio test
- 1996
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive sequential probability ratio test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) type test. The test statistics is based upon the variance of the amplitude of the weld voltage. It is shown that the variance of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line
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| 3. |
- Akkermans, Hans, et al.
(författare)
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Homebots : Intelligent Decentralized Services for Energy Management
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The deregulation of the European energy market, combined with emerging ad-vanced capabilities of information technology, provides strategic opportunities for new knowledge-oriented services on the power grid. HOMEBOTS is the name we have coined for one of these innovative services: decentralized power load management at the customer side, automatically carried out by a ‘society’ of interactive house-hold, industrial and utility equipment. They act as independent intelligent agents that communicate and negotiate in a computational market economy. The knowl-edge and competence aspects of this application are discussed, using an improved version of task analysis according to the COMMONKADS knowledge methodology. Illustrated by simulation results, we indicate how customer knowledge can be mo-bilized to achieve joint goals of cost and energy savings. General implications for knowledge creation and its management are discussed.
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| 4. |
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| 5. |
- Angelin, Lars
(författare)
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On the Properties of a Congestion Control Mechanism for Signaling Networks Based on a State Machine
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Congestion control in signaling systems is a necessity to fulfil the requirements of a tele-communication network that aims satisfy the customers’ requirements on service quality. Heavy network load is an important source of customer dissatisfaction as congested net-works result in deteriorated service quality. Sessions of a signaling service with high real time demands which are subject to unacceptable delays may be obsolete or prematurely terminated by the customer; in either way, they are a burden to the signaling network. It would ease the load of the network and improve the performance of all sessions in progress, if such delayed sessions could be aborted as quickly as possible. By measuring the network delay on individual signals of a service session, it is possible to perform signaling network congestion control that considers the state in the entire signaling network. Under the assumption that a session comprises a sequence of signals between one originating node and an arbitrary number of destination nodes, it is possible to predict the total duration of a session. The prediction is calculated from previously completed signals using a state machine, which is defined per signaling link. The annihilation of sessions, for which the prediction exceeds a predefined time limit, is an embryo of a simple signaling network congestion control mechanism (CCM). This simple CCM increases the number of successfully completed services with several hundred percent under favorable circum-stances. The state machine approach is proven to perform well in all types of environ-ments. The robustness and stability of the proposed CCM is demonstrated in a wide range of environments. The fairness in the admission of signaling services into the network at very high loads are also shown to be good.
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| 6. |
- Angelin, Lars, et al.
(författare)
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On the Robustness of a Congestion Control Algorithm for Signaling Networks Based on a State Machine
- 1996
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Konferensbidrag (refereegranskat)abstract
- Sessions of a signaling service with high real time demands which are subject to unaccept-able delays may be obsolete or prematurely terminated by the customer; in either way, they are a burden to the signaling network. It would ease the load of the network and im-prove the performance of all sessions in progress, if such delayed sessions could be abort-ed as quickly as possible. By measuring the network delay on individual signals of a service session, it is possible to perform signaling network congestion control that consid-ers the state in the entire signaling network. Under the assumption that a session comprises a sequence of signals between one originating node and an arbitrary number of destination nodes, it is possible to predict the total duration of a session. The prediction is calculated from previously completed signals using a state machine, which is defined per signaling link. The annihilation of sessions, for which the prediction exceeds a predefined time limit, is an embryo of a simple signaling network congestion control mechanism (CCM). This simple CCM increases the number of successfully completed services with a few hundred percent under favorable circumstances. The state machine approach has been proven to function well in all types of environments. The robustness and stability of the proposed CCM is demonstrated and the fairness in the admission of signaling services into the net-work at very high loads are also shown.
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| 7. |
- Arvidsson, Åke, et al.
(författare)
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Congestion Control in Intelligent Networks for Real Time Performance and Profit Optimisation
- 1996
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Konferensbidrag (refereegranskat)abstract
- Current developments in technologies and markets stress the importance of exible and robust performance optimisation and congestion control. In intelligent networks, congestion control has traditionally taken a purely technical view and focused on pro- tecting individual nodes from harmful overloads. We take a profit oriented, network wide view and develop a congestion control mechanism to ensure real time performance under profit maximisation. Numerical studies in a simulator show that the proposed mechanism is robust and, in particular in overloaded states, provides a substantial improvement in comparison to conventional load control mechanisms.
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| 8. |
- Arvidsson, Åke, et al.
(författare)
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Reduction of Routing Complexity in Telecommunication Networks by a Novel Decomposition Method
- 1996
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Konferensbidrag (refereegranskat)abstract
- Routing problems are often encountered when designing and managing telecommuni- cation networks. Today, routing problems are affected by the growing sizes of networks, which increase the complexity, and by introduction of new services and technologies, which rise the demands. Rather than resorting to entirely heuristic algorithms and/or large data bases with off-line precomputed routing information for various situations, we propose a a new decomposition method whereby any routing algorithm is speeded up considerably, thus permitting the deployment of well founded routing algorithms even for real time purposes. In our paper, we present this new method in formal terms, and apply it to a real routing problem. Finally, investigating the performance of our fast implementation by comparing it to the optimal, non-accelerated solution, we find that considerable time savings can be made at a limited cost in terms of non-optimality of the final solution. It is also emphasised that in real-time applications with non-constant traffics, this nominal degradation might be more than compensated for by the prompt delivery.
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| 9. |
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| 10. |
- Bosch, Jan
(författare)
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A Model for a Flexible and Predictable Object-Oriented Real-Time System
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The requirements on real-time systems are changing. Traditionally, reliability and predictability of, especially hard, real-time systems were the main requirements. This lead to systems that were stand-alone, embedded and static. Future real-time systems, but also current systems, still require reliability and predictability, but also distribution of the real-time system, integration with non real-time systems and the ability to dynamically change the components of the system at runtime. Traditional approaches to real-time system development have difficulties in addressing these additional requirements. Therefore, new ways of constructing real-time systems have to be explored. In this article, we develop a real-time object-oriented model that facilitates the requirements of flexibility without sacrificing the predictability, integration and dynamicity aspects.
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