| 1. |
- Adolfsson, Stefan, et al.
(författare)
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A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding
- 1997
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.
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| 2. |
- 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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| 3. |
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| 4. |
- Adolfsson, Stefan, et al.
(författare)
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On-line quality monitoring in short : circuit gas metal arc welding
- 1999
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Ingår i: Welding Journal. - New York,N.Y. : American welding society. - 0043-2296. ; 78:2, s. 59S-73S
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problems involved in the automatic monitoring of the weld quality produced by robotized short-arc welding. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), was used. The algorithm may similarly be viewed as a cumulative sum (CUSUM) type test, and is well-suited to detecting sudden minor changes in the monitored test statistic. The test statistic is based on the variance of the weld voltage, wherein it will be shown that the variance decreases when the welding process is not operating under optimal conditions. The performance of the algorithm is assessed through the use of experimental data. The results obtained from the algorithm show that it is possible to detect changes in weld quality automatically and on-line.
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| 5. |
- Adolfsson, Stefan, et al.
(författare)
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Quality Monitoring in Robotised Welding using Sequential Probability Ratio test
- 1996
-
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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| 6. |
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| 7. |
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| 8. |
- Alvesund, Carolin
(författare)
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Lokalt utvecklingsarbete i Svarte, Ystad kommun : en utvärdering.
- 1998
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Rapport (refereegranskat)abstract
- An evaluation of the local development work in Svarte, Ystad municipality, which has been carried on between 1995 and 1997. The evaluation aims to describe the local development work regarding 1)how the interplay between local and municipality actors has worked, 2)how local initiatives to development has been supported with municipal physical planning, 3)how civil ascendancy has come to expression, 4)how the collaboration within the municipality and between the municipality and other actors has worked, 5)how new forms of physical planning has been used.
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| 9. |
- Alvesund, Carolin
(författare)
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Lokalt utvecklingsarbete på Karlshamns landsbygd : en utvärdering.
- 1998
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Rapport (refereegranskat)abstract
- An evaluation of the local development work in the rural parts of Karlshamn municipality, which has been carried on between 1995 and 1997. The evaluation aims to describe the local development work regarding 1)how the interplay between local and municipality actors has worked, 2)how local initiatives to development has been supported with municipal physical planning, 3) how civil ascendancy has come to expression, 4)how the collaboration within the municipality and between the municipality and other actors has worked, 5)how new forms of physical planning has been used.
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| 10. |
- Andrén, Linus, et al.
(författare)
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Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration
- 1999
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Konferensbidrag (refereegranskat)abstract
- In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construction with integrated high magnetostrictive actuators was used. However, high magnetostrictive actuators generally have a non-linear behavior and it is a well known fact that non-linear properties in the forward path in an active control system is likely to degrade the robustness of the control system. A new generation embedded active tool holder shanks based on piezo ceramic actuators has been developed. Based on spectrum estimates, both coherence spectrum and frequency response function estimates has been calculated for both the old tool holder construction and the new generation active tool holder shank. From the results it follows that the phase delay is smaller and the linearity of the new generation active tool holder shank are superior compared to the old technology. The physical features and properties of the new generation active tool holders are superior to the old tool holder.
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