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- Illankoon, Prasanna, 1977-
(författare)
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Soft Issues of Industry 4.0 : A study on human-machine interactions
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous industrial operations are becoming the norm due to advancements in technology, which has led to both advantages and disadvantages for the organisations involved. The use of intelligent systems has resulted in higher system reliability, a higher quality product, and reduced risk for human error. These systems collect large amounts of information, analyse them, make predictions, and take decisions, of which humans cannot do in the same capacity, have led to new and expanded levels of interactions. One key aspect concerns the fact that human interaction has decreased although has become more critical than before. Even if the systems are advanced and automated, human intervention is still necessary: such as maintenance actions, selection of data to train the system, and advanced decision making. Human intervention is especially crucial when dealing with complex and safety critical systems, where and when immediate interventions are required. Moreover, an expert human can improvise and make novel decisions in a capacity that present intelligent systems cannot. The problem is that both humans and machines need assistance to perform well. Autonomous operation is not perfect and when problems arise, humans must react. Although it is common that humans when not actively interacting with the system tend to lose perspective and find it difficult to quickly analyse a situation when it arises. Which means that they “fall out of the loop”. Their ability to gain a good understanding of the situation and make good decisions when the system suddenly needs their interaction is lost. In other words, humans have lost their situation awareness (SA) and a good SA it is needed in dynamic environments if they are to intervene quickly and successfully. If, and when a system can assist a human to quickly assess the situation and get back “into the loop” then the human can make educated decisions in a much quicker fashion. The purpose of this research was to explore and describe the importance of SA in maintenance and to recommend how to develop and provide better SA for intelligent maintenance systems (IMS).This thesis consists of a literature study conducted to develop the theoretical framework and two case studies were used to test the theoretical concepts. The thesis work tested five systematic methodologies to find suitable interventions to fulfil the SA requirements. The first case study focused on SA requirements during maintenance execution in a manufacturing organisation; there a quick return to production was the focus. The second case study was SA requirements in maintenance in the aviation domain, where safety is a top priority. The case study data were collected using interviews, observations, focus groups, and archival records. These qualitative data were analysed using qualitative content analysis, cognitive task analysis, and case taxonomic analysis.This work resulted in the identification of seven key SA requirements for maintenance: consisting of detection of abnormalities; diagnosing and predicting their behaviour; making changes in system configuration; compliance with maintenance standards; conducting effective maintenance judgements; maintenance teams; and for safe maintenance work. Five strategies to maintain SA were identified: explicit knowledge status, sense making, recognition primed decision making, skilled intuition, and heuristics. We also argue why IMS will make it difficult for humans to use most of these strategies to maintain SA in future. Finally, a new theoretical model for decision support (Distributed Collaborative Awareness Model) was developed. The study also shows how to apply these interventions in the railway maintenance sector. In conclusion, this study shows that in the maintenance domain, keeping humans in the loop requires a novel collaborative approach where the integration of the strengths of intelligent systems and human cognition is necessary. We also argue that a better understanding of SA strategies will lead to the further development of SA support for the human operator and maintenance technician.
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| 6. |
- Montaño, Raúl, et al.
(författare)
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Resistance of spark channels
- 2006
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 34:5, s. 1610-1619
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Tidskriftsartikel (refereegranskat)abstract
- A study undertaken to measure the resistance ofspark channels in air with two different current waveforms ispresented. In one experiment, the spark was created by a Marxgenerator. In this case, the gap length was maintained at 12.8 cm,and the current flowing through the spark had a peak currentlying in the range of 0.2–2.2 kA. The decay time of the currentwas larger than 100 μs. In the other experiment, the spark wascreated by a current generator. In that experiment, the gap lengthwasmaintained at 1 cm, and the current flowing through the sparkhad peak-current amplitudes in the range of 35–48 kA. The decaytime of the current was larger than 500 μs. The results showthat the resistance of spark channels initially decreases, reaches aminimum value, and then recovers as the current in the spark gapdecreases. The minimum resistance of the spark channel decreaseswith an increasing peak current. The results are compared withvarious theories that attempt to predict the temporal variationof the resistance of spark channels. The comparison shows thatfurther developments in the existing theoretical models are neededin order to reproduce with better accuracy the dynamic behaviorof the channel resistance.
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| 7. |
- Perera, Chandana, et al.
(författare)
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Analysis of Channel Tortuosity using 8 m Long Laboratory Sparks
- 2018
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Ingår i: 34th International Conference on Lightning Protection (ICLP 2018). - : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- The tortuosity of the channel is defined as "Mean absolute angle change of the angle change and it measures how strongly the tortuous path of the channel of lightning/laboratory spark is twisting. 8 m Long laboratory sparks and high speed (20000 frames per second) technology used for this experiment. Using these data it has been calculated the channel tortuosity of 8 m long sparks and vertical profile of channel tortuosity. In addition to that spectral analysis of the angel change of the twisting path of the channel has been done in this study.
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- Rahman, Mahbubur, et al.
(författare)
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Measurements of NOx produced by rocket-triggered lightning
- 2007
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:3, s. L03816-
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Tidskriftsartikel (refereegranskat)abstract
- We present the first direct measurements of NOx generated by specific lightning sources. In July 2005, three negative lightning flashes were triggered using the rocket-and-wire technique at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The NOx produced by these three rocket-triggered flashes was measured. The NOx production per unit charge was between 2 and 3 · 1020 molecules per meter per coulomb. The data show that the NOx production is primarily from long-duration, steady currents, as opposed to microsecondscale impulsive return stroke currents. This observation implies that cloud discharges, which transfer, via a steady current of the order of 100 A, larger charges than ground discharges, but do not contain return strokes, are as efficient as (or more efficient than) cloud-to-ground discharges in producing NOx.
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| 10. |
- Rahman, Mahbubur, et al.
(författare)
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NO(X) production by impulse sparks in air
- 2011
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Ingår i: Journal of Electrostatics. - : Elsevier BV. - 0304-3886 .- 1873-5738. ; 69:6, s. 494-500
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study on the production of NO(X) by impulse sparks in air is presented. The emphasis is placed on the dependence of the NO(X) yield on the signature of the discharge current waveforms. A voltage and two current impulses were used in the experiments to create a spark and the NO(X) production was measured by the method of chemiluminescence. The results show that, for a given current waveform, the NO(X) production varies linearly with the peak current and the gap length. In addition, it was found that the NO(X) yield increases with the duration of the current for a given peak current.
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