| 1. |
- Persson, Rickard, 1958-, et al.
(författare)
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On-track test of strategies for less motion sickness on tilting trains.
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Ingår i: Vehicle System Dynamics. - 0042-3114 .- 1744-5159.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Carbody tilting is today a mature and inexpensive technology that permits higher speeds in horizontal curves, thus shortening travel time. However, tilting trains run a greater risk of causing motion sickness than non-tilting ones. It is likely that the difference in motions between the two train types contributes to the observed difference in risk of motion sickness. Decreasing the risk of motion sickness has until now been equal to increasing the discomfort related to quasi-static lateral acceleration. But, there is a difference in time perception between discomfort caused by quasi-static quantities and motion sickness, which opens up for new solutions. One proposed strategy is to let the local track conditions influence the tilt and give each curve its own optimized tilt angle. This is made possible by new tilt algorithms, storing track data and using a positioning system to select the appropriate data. On-track tests involving more than 100 test subjects onboard a tilting train have been performed to evaluate the effectiveness of the new tilt algorithms and the different requirements on quasi-static lateral acceleration and lateral jerk. The evaluation shows that the rms values important for motion sickness can be influenced without changing the requirements on quasi-static lateral acceleration and lateral jerk. The evaluation also shows that reduced quantities related to motion sickness lead to a reduction in experienced motion sickness. However, this relation seems to be valid in a certain range as the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. This non-linear relation has also been observed by other researchers in laboratory tests.
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| 2. |
- Persson, Rickard, 1958-, et al.
(författare)
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Strategies for less motion sickness on tilting trains
- 2010
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Ingår i: Proceedings of Comprail 2010. - Southampton : WIT Press. - 9781845644680 ; , s. 581-591
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Many railways have put tilting trains into operation on lines with horizontal curves with small radii. Tilting trains have vehicle bodies that can roll inwards, reducing the lateral acceleration perceived by the passengers. Tilting trains can therefore run through curves at higher speeds. However, excessive tilt motions can cause motion sickness in sensitive passengers. On the other hand, too little tilting will cause discomfort from high lateral acceleration and jerk [1].The present paper presents new tilt algorithms aimed at balancing the conflicting objectives of ride comfort and less motion sickness. An enhanced approach is taken, where the amount of tilt depends on the local track conditions and the train speed. The paper shows how selected tilt algorithms influence certain motion sickness related carbody motions.Speed profiles designed to avoid local peaks in the risk of motion sickness are another possibility. The speed profiles for both tilting and non-tilting trains are today set from safety and comfort perspectives only, thus minimizing the running time. The present paper shows how speed profiles could be used to balance the conflicting objectives of running time and less risk of motion sickness. The result is derived from simulations and put in relation to today’s tilt algorithms and speed profiles on the Stockholm – Gothenburg main line in Sweden (457 km).
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| 3. |
- Persson, Rickard, 1958-
(författare)
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Motion sickness on-track testing
- 2008
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Ingår i: Proceedings of the 43rd UK Conference on Human Response to Vibration.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The present evaluation of motion sickness during on-track tests is based on data collected by the Fast And Comfortable Train (FACT) project at the Nordic field tests 2004. The method chosen for this analysis was to use linear regression between combinations of the collected motion data during the run and the passengers reported level of nausea. The methods of these analyses are based on earlier similar analyses, but here applied on an extended set of data including: transversal accelerations, rotational accelerations, products between transversal and rotational accelerations and more. Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The models of motion sickness are derived either by tests in laboratories or by tests on train. In mathematical statistical evaluations these models may be used as hypotheses to be tested. The present analysis is based on six different hypotheses. The model on vertical acceleration shows the highest correlation to motion sickness on trains with active tilt. It is consistent with increased levels of vertical motions in tilting trains compared with non-tilting ones. However, correlation is high between vertical acceleration and several other motions, which excludes that vertical acceleration is pointed out as the cause to motion sickness in tilting trains. This is a known problem caused by the rules to design railways and how tilting trains acts today.
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| 4. |
- Persson, Rickard, 1958-
(författare)
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Research on the competitiveness of tilting trains
- 2007
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Ingår i: Proceedings of Railway Engineering - 2007. - Edinburgh : Engineering Technics Press.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Research has been conducted on areas identified to have potential to further improve the competitiveness of tilting trains. The running times improves with increased cant deficiency, top speed and tractive performance; however the benefit of increased top speed and tractive performance is small above a certain level. 15 minutes running time (9%) may be gained on the Swedish line Stockholm – Gothenburg (457 km) if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting train will, independent of top speed and tractive power, have longer running times than a tilting train with today’s maximum speed and tractive power. Guidelines for installation of cant are given, optimizing the counteracting requirements on comfort in non-tilting trains and risk of motion sickness in tilting trains. The guideline is finally compared with the installed cant on the Stockholm – Gothenburg line. Line design and particularly the distance between the passing possibilities are studied for different mixed traffic with high-speed tilting trains and freight trains. The necessary distance between the passing possibilities becomes short when the number of freight trains increases.
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| 5. |
- Persson, Rickard, 1958-
(författare)
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Tilting trains : Enhanced benefits and strategies for less motion sickness
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbody tilting is today a mature and inexpensive technology that allows higher train speeds in horizontal curves, thus shortening travel time. This doctoral thesis considers several subjects important for improving the competitiveness of tilting trains compared to non-tilting ones. A technology review is provided as an introduction to tilting trains and the thesis then focuses on enhancing the benefits and strategies for less motion sickness. A tilting train may run about 15% faster in curves than a non-tilting one but the corresponding simulated running time benefit on two Swedish lines is about 10%. The main reason for the difference is that speeds are set on other grounds than cant deficiency at straight track, stations, bridges, etc. The possibility to further enhance tilting trains’ running speed is studied under identified speed limitations due to vehicle-track interaction such as crosswind requirements at high speed curving. About 9% running time may be gained on the Stockholm–Gothenburg (457 km) mainline in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Non-tilting high-speed trains are not an option on this line due to the large number of 1,000 m curves. Tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The vertical acceleration model shows the highest correlation to motion sickness on trains with active tilt. However, vertical acceleration has a strong correlation to several other motions, which precludes vertical acceleration being pointed out as the principal cause of motion sickness in tilting trains. Further enhanced speeds tend to increase carbody motions even more, which may result in a higher risk of motion sickness. However, means to counteract the increased risk of motion sickness are identified in the present work that can be combined for best effect. Improved tilt control can prevent unnecessary fluctuations in motion sickness related quantities perceived by the passengers. The improved tilt control can also manage the new proposed tilt algorithms for less risk of motion sickness, which constitute one of the main achievements in the present study. Local speed restrictions are another means of avoiding increased peak levels of motion sickness when increasing the overall speed. The improved tilt control and the proposed tilt algorithms have proven to be effective in on-track tests involving more than 100 test subjects. The new tilt algorithms gave carbody motions closer to non-tilting trains. Rather unexpectedly, however, the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. It is likely that even better results can be achieved by further optimization of the tilt algorithms; the non-linear relation between motions and motion sickness is of particular interest for further study.
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| 6. |
- Persson, Rickard, 1958-
(författare)
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Tilting trains : Technology, benefits and motion sickness
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbody tilting is today a mature and inexpensive technology allowing higher speeds in curves and thus reduced travel time. The technology is accepted by most train operators, but a limited set of issues still holding back the full potential of tilting trains. The present study identifies and report on these issues in the first of two parts in this thesis. The second part is dedicated to analysis of some of the identified issues. The first part contains Chapters 2 to 5 and the second Chapters 6 to 12 where also the conclusions of the present study are given. Chapters 2 and 3 are related to the tilting train and the interaction between track and vehicle. Cross-wind stability is identified as critical for high-speed tilting trains. Limitation of the permissible speed in curves at high speed may be needed, reducing the benefit of tilting trains at very high speed. Track shift forces can also be safety critical for tilting vehicles at high speed. An improved track standard must be considered for high speed curving. Chapters 4 and 5 cover motion sickness knowledge, which may be important for the competitiveness of tilting trains. However, reduced risk of motion sickness may be contradictory to comfort in a traditional sense, one aspect can not be considered without also considering the other. One pure motion is not the likely cause to the motion sickness experienced in motion trains. A combination of motions is much more provocative and much more likely the cause. It is also likely that head rotations contribute as these may be performed at much higher motion amplitudes than performed by the train. Chapter 6 deals with services suitable for tilting trains. An analysis shows relations between cant deficiency, top speed, tractive performance and running times for a tilting train. About 9% running time may be gained on the Swedish line Stockholm – Gothenburg (457 km) if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting very high-speed train (280 km/h) will have longer running times than a tilting train with today’s maximum speed and tractive power. This statement is independent of top speed and tractive power of the non-tilting vehicle. Chapters 7 to 9 describe motion sickness tests made on-track within the EU-funded research project Fast And Comfortable Trains (FACT). An analysis is made showing correlation between vertical acceleration and motion sickness. However, vertical acceleration could not be pointed out as the cause to motion sickness as the correlation between vertical acceleration and several other motions are strong. Chapter 10 reports on design of track geometry. Guidelines for design of track cant are given optimising the counteracting requirements on comfort in non-tilting trains and risk of motion sickness in tilting trains. The guidelines are finally compared with the applied track cant on the Swedish line Stockholm – Gothenburg. Also transition curves and vertical track geometry are shortly discussed. Chapters 11 and 12 discusses the analysis, draws conclusions on the findings and gives proposals of further research within the present area.
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| 7. |
- Persson, Rickard, 1958-
(författare)
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Tilting trains : benefits and motion sickness
- 2010
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - 0954-4097 .- 2041-3017. ; 224:F6, s. 513-522
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Tidskriftsartikel (refereegranskat)abstract
- Carbody tilting is today a mature and inexpensive technology that allows higher speeds on curves, thus shortening travel time. The technology has been accepted by many train operators, but some issues are still holding back the full potential of tilting trains. This paper focuses on improving the benefits and limiting the drawbacks of tilting trains. This is done by quantifying the possible running time benefits compared with today's tilting trains, identifying what motion components have an influence on motion sickness, and finally quantifying the influence from the increased speed on these motion components. A running time analysis was made to show what potential there is to further improve running times by optimizing tracks and trains. Relations between cant deficiency, top speed, tractive performance, and running times are shown for a tilting train. About 9 per cent running time may be gained on the Stockholm-Gothenburg (457 km) main line in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Introduction of non-tilting high-speed trains is not an option on this line due to the large number of 1000 m curves. However, tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Higher curve speeds will increase carbody motions still further, but there are some possibilities to trade between vertical and lateral carbody acceleration by increasing or decreasing roll.
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| 8. |
- Persson, Rickard, 1958-
(författare)
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Tilting trains : description and analysis of the present situation: literature study
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Growing competition from other modes of transportation has forced railway companies throughout the world to search for increased performance. Travelling time is the most obvious performance indicator that may be improved by introducing high-speed trains. Trains with capability to tilt the bodies inwards the curve is a less costly alternative than building new lines with large curve radii, which is needed for the non-tilted high-speed trains.Today, tilting has become a mature technology accepted by most operators, but not favoured by many. Research has been conducted on areas with potential to improve the competitiveness of tilting trains.Track shift force may be critical for a high-speed tilting train and improved levels of track irregularities must be considered. The risk of overturning may give restriction on cant deficiency at high speeds.Motion sickness in both non-tilting and tilting trains is still being reported. The sensory conflict is the most common explanation of motion sickness.The running times improve with increased cant deficiency, top speed and tractive performance; however the benefit of increased top speed and tractive performance is small above a certain level.Guidelines for installation of cant are given that optimize the counteracting requirements on good comfort in non-tilting trains and low risk of motion sickness in tilting trains.
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