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AF
Gävle, Sweden

Nasselqvist M.,AF | Gustavsson R.,Vattenfall | Aidanpaa J.-O.,Lulea University of Technology
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2013

It is important to monitor the radial loads in hydropower units in order to protect the machine from harmful radial loads. Existing recommendations in the standards regarding the radial movements of the shaft and bearing housing in hydropower units, ISO-7919-5 (International Organization for Standardization, 2005, "ISO 7919-5: Mechanical Vibration-Evaluation of Machine Vibration by Measurements on Rotating Shafts-Part 5: Machine Sets in Hydraulic Power Generating and Pumping Plants, " Geneva, Switzerland) and ISO-10816-5 (International Organization for Standardization, 2000, "ISO 10816-5: Mechanical Vibration-Evaluation of Machine Vibration by Measurements on Non-Rotating Parts-Part 5: Machine Sets in Hydraulic Power Generating and Pumping Plants, " Geneva, Switzerland), have alarm levels based on statistical data and do not consider the mechanical properties of the machine. The synchronous speed of the unit determines the maximum recommended shaft displacement and housing acceleration, according to these standards. This paper presents a methodology for the alarm and trip levels based on the design criteria of the hydropower unit and the measured radial loads in the machine during operation. When a hydropower unit is designed, one of its design criteria is to withstand certain loads spectra without the occurrence of fatigue in the mechanical components. These calculated limits for fatigue are used to set limits for the maximum radial loads allowed in the machine before it shuts down in order to protect itself from damage due to high radial loads. Radial loads in hydropower units are caused by unbalance, shape deviations, dynamic flow properties in the turbine, etc. Standards exist for balancing and manufacturers (and power plant owners) have recommendations for maximum allowed shape deviations in generators. These standards and recommendations determine which loads, at a maximum, should be allowed before an alarm is sent that the machine needs maintenance. The radial bearing load can be determined using load cells, bearing properties multiplied by shaft displacement, or bearing bracket stiffness multiplied by housing compression or movement. Different load measurement methods should be used depending on the design of the machine and accuracy demands in the load measurement. The methodology presented in the paper is applied to a 40MW hydropower unit; suggestions are presented for the alarm and trip levels for the machine based on the mechanical properties and radial loads. Copyright © 2013 by ASME. Source


Andersson M.,AF | Sandblom F.,Volvo
Proceedings of the 16th International Conference on Information Fusion, FUSION 2013 | Year: 2013

This paper addresses a practical issue that arises when the output from two local trackers, using two different state-space models, are to be fused with each other in a global track-to-track fusion system. Such fusion algorithms require the local tracks to be represented in a joint state-space, meaning that at least one of these tracks needs to be transformed prior to the track fusion. © 2013 ISIF ( Intl Society of Information Fusi. Source


Pipkorn B.,Autoliv | Forsberg C.,Autoliv | Takahashi Y.,Honda Corporation | Ikeda M.,Honda Corporation | And 3 more authors.
2014 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury | Year: 2014

For evaluation of pedestrian-to-vehicle impacts and pedestrian dummy development, a mathematical and mechanical generic buck corresponding to a passenger vehicle front was developed. The buck consists of the major energy-absorbing structures of a passenger vehicle in a pedestrian-to-vehicle impact. The components are lower bumper, bumper, grille, hood edge, hood and windshield. Initially, the buck was developed by means of computer-aided engineering (CAE). A CAE model of the buck was refined and tuned. In the current study a physical version of the buck was fabricated. The fabricated buck parts were all tested at the component level. A comparison was made between the mechanical generic buck and the range of results from small family cars in EuroNCAP pedestrian tests to confirm the similarity between the buck and small family cars. Finally, the mechanical test results were used to compare the results with predictions from corresponding simulations with the CAE buck components to confirm correspondence between the CAE model of the buck and the mechanical counterpart. The pedestrian buck front-end stiffness was within the range of small family car stiffness derived from EuroNCAP pedestrian tests. Therefore, it can be concluded that the pedestrian buck, although a simplified and cost-effective design, is a good representation of small family cars on the European market. Source


Elofsson C.,AF | Karlsson C.,Radiobusters | Beckman C.,KTH Royal Institute of Technology
IEEE International Symposium on Electromagnetic Compatibility | Year: 2014

In 2011, the Swedish regulator (PTS) invited all interested parties to apply for licenses to use radio transmitters in the 790-862 MHz frequency band. The licenses are service and technology neutral but all licensees are expected to provide Mobile Broadband (MBB) services using the LTE standard. In order to protect the Digital Terrestrial Television (DTT) services provided in the adjacent bands from interference, PTS imposed a number of technical conditions on the licensees. Here, a brief overview of these technical conditions is given, and a measurement campaign in order to investigate the interference between MBB and DTT services was conducted. The measurements show that the technical requirements indeed provide the additional protection for DTT reception from the MBB downlink as envisioned by PTS. However, the measurements also indicate that MBB services may be suffering from interference from TV Channel 60 within a radius of about 5km from the DTT transmitter. One year after the rollout of MBB services in the Swedish 800MHz band, very few complaints had been received by the regulator. This may be explained with that in cases where interference with the TV reception did occur, the licensees have provided additional filters for free. Another reason may be that to date only a low number of terminals including the 800 band have yet reached the Swedish market and worse interference problems from the MBB uplink may still appear. © 2014 IEEE. Source


Hakansson C.,AF
Paper Conference and Trade Show 2010, PaperCon 2010 | Year: 2010

A growing focus on environmental and energy saving measures within the paper and pulp industry is a key driver for technological development, but many energy efficient improvements require significant financial investment. Process-based technology upgrades deliver productivity benefits as well as energy savings and can therefore be justified in many cases. However, many plants might currently be missing the opportunity to leverage the potentially substantial energy savings possible by simply adapting and refining processing capacity to actual need. Here, results from a study by ÅF based on process modifications at a sack paper machine in Scandinavia, quantify potential energy savings within the vacuum system of a paper machine. By adapting capacity of the vacuum system within the paper machine to the real demands of each product and adopting press nip dewatering, it is shown that no less than two out of ten Nash pumps could be taken out of operation without compromising product quality. Source

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