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  • 1.
    Andersson, Evert
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    On the Optimization of a Track-Friendly Bogie for High Speed2009In: 21st International Symposium on Dynamics of Vehicles on Roads and Tracks, IAVSD'09, Stockholm, August 17-21, 2009., 2009Conference paper (Other academic)
    Abstract [en]

    When designing and optimizing a rail vehicle there is a contradiction between, on the one hand, stability on straight track at high speed and, on the other hand, reasonable wheel and rail wear in small- and medium radius curves. Higher speeds require to some extent stiffer wheelset guidance to avoid hunting and ensure stability. However, with stiffer wheelset guidance the risk of increased wheel and rail wear in curves is imminent. In this paper, the process of developing and optimizing a track-friendly bogie is described. A multi-body system (MBS) simulation model was used, taking due consideration to nonlinearities in suspension and wheel-rail contact, as well as realistic flexibilities in the track. Adequate and systematic consideration is taken to a wide range of possible non-linear wheel-rail combinations. Dynamic stability is investigated both on straight track and in wide curves at high speeds. The balance between flange wear and tread wear is studied in order to maximize wheel life between re-profiling operations in the intended average operation. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering, which in combination with appropriate yaw damping ensures stability on straight track at higher speeds. The bogie has been subject to both certification testing and long-term service testing in the Gröna Tåget (the Green Train) research and development programme.

  • 2.
    Andersson, Evert
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Radial self-steering bogies - Development, advantages and limitations2007In: ZE Vrail - Glasers Annalen: Zeitschrift fuer das gesamte System Bahn, ISSN 1618-8330, Vol. 131, no Suppl., p. 248-259Article in journal (Refereed)
    Abstract [en]

    Considering the total cost of railway operations, It is important to reduce the deterioration caused to the track by rail vehicles and vice versa. Radial steering running gear, where the wheelsets take up approximate radial positions in curves, is an important mean of reducing rail and wheel wear. They also allow curves to be negotiated at higher lateral acceleration on non-perfect track, without exceeding stipulated limits for lateral track shift forces. In order to run dynamically stable at high speed, the damping of the bogie must be appropriate, in particular the yaw damping between bogies and car body. Since the mid-1970's radial self-steering bogles have been developed and used in about 1 200 passenger rail vehicles in Scandinavia. This development continues and during 2006 a test train with radial self-steering bogies is run in speeds up till 281 km/h as part of the Swedish R&D program "GrönaTå get" (GreenTrain). Although there are limitations in the performance of passively self-steering bogles they are a simple and proven solution. Ultimately, In the future actively controlled radial steering may be considered asan appropriate mean to achieve higher performance and track-friendliness.

  • 3.
    Andersson, Evert
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Radial Self-Steering Bogies: Recent Developments for High Speed2009In: 7th International Conference on Railway Bogies and Running Gears / [ed] István Zobory, 2009, p. 63-72Conference paper (Other academic)
    Abstract [en]

    Considering the total cost of railway operations, it is important to reduce the deterioration caused to the track by rail vehicles and vice versa. Radial steering running gear, where the wheelsets take up approximate radial positions in curves, is an important mean of reducing rail and wheel wear. They also allow curves to be negotiated at higher lateral acceleration on non-perfect track, without exceeding stipulated limits for lateral track shift forces. In order to run dynamically stable at high speed, the damping of the bogie must be appropriate, in particular the yaw damping between bogies and carbody. Radial self-steering bogies are used on more than 1200 rail passenger vehicles in Scandinavia since the early 1980’s. The maximum service speed of these vehicles ranges up to 210 km/h. Ongoing development seems to confirm that the use of such bogies can be extended into the very high-speed area of at least 250 km/h. There has previously been some scepticism on the feasibility of soft wheelset guidance for higher speeds, in particular with respect to running stability. Although there are some limitations in the performance of radial self-steering bogies, this solution is robust and well-proven since about 25 years. The ultimate future may be a mechatronic bogie, where the wheelsets are guided in the most optimal way through controlled and forced radial steering. Such bogies may be justified if performance is out of the possible range of passive self-steering solutions.

  • 4.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Andersson, Evert
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Development of Track-Friendly Bogies for High Speed: A Simulation Study2007Report (Other academic)
  • 5.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Development and test of active secondary suspension in a rail vehicle2009In: Proceedings of the 21st International Symposium: Dynamics of Vehicles on Roads and Tracks, 2009Conference paper (Other academic)
    Abstract [en]

    This paper deals with a quarter-car rail vehicle model using active lateral secondary suspension. H control theory is applied to the active suspension with the purpose of improving the dynamic performance of the vehicle. In H control, weight functions are applied to certain signals in order to design the controller. Different combinations of signal weighting have been evaluated through simulations. The main goal is to minimise the carbody acceleration and hence improve ride comfort. Furthermore, the H control theory is compared to sky-hook damping, which has been used in previous studies by the authors. Simulation results show that both control methods significantly improve the ride comfort as compared to a passive case. Compared to sky-hook damping, H control provides more flexibility in the design process due to the possibility to control several parameters. Furthermore, H control generates similar carbody accelerations at the same control force as sky-hook damping; however, the relative displacement is somewhat lower with H control.

  • 6.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    On-track tests with active lateral secondary suspension: a measure to improve ride comfort2008In: ZEV Rail Glasers Annalen, ISSN 1618-8330, Vol. 132, no 11-12, p. 469-477Article in journal (Refereed)
    Abstract [en]

    At increased rail vehicle speed it may be difficult to maintain acceptable passenger ride comfort with conventional passive secondary suspension. This paper presents the development of an active secondary suspension that provides good ride comfort improvements, but still at an acceptable cost level to enable future implementation. On-track tests have been performed with a two-car Regina train, using electro-hydraulic actuators together with sky-hook damping control and a Hold-Off-Device function to actively control the secondary suspension. The evaluated measurement results show that the active suspension system significantly reduces the lateral dynamic carbody motions and the lateral quasi-static displacements between carbody and bogies in curves, which improves the ride comfort and allows higher speeds, particularly in curves.

  • 7.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Ride Comfort Improvements in a High-Speed Train with Active Secondary Suspension2009In: Proceedings of the International Symposium on Speed-Up, Safety and Service Technology for Railway and Maglev Systems, STECH'09, Niigata, Japan, June 16-19, 2009, 2009Conference paper (Refereed)
  • 8.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Ride comfort improvements in a high-speed train with active secondary suspension2010In: Journal of Mechanical Systems for Transportation and Logistics, ISSN 1882-1782, Vol. 3, no 1, p. 206-215Article in journal (Refereed)
    Abstract [en]

    A combination of increased vehicle speeds and non-improved railway tracks may have a negative impact on passenger comfort. Active technology can replace the conventional passive solution of the secondary suspension of a rail vehicle in order to maintain good passenger comfort even when vehicle speed is increased and track conditions are inferior. This paper focuses on the benefits of using a so-called Hold-Off-Device (HOD) function in the lateral secondary suspension. On-track tests have been performed with the active secondary suspension concept implemented in a two-car Regina train during the summers of 2007 and 2008. The evaluated measurement results have been very satisfactory and the device will be implemented in long-term tests in service operation. These tests were carried out in the beginning of 2009.

  • 9.
    Orvnäs, Anneli
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Ride Comfort Improvements of a REGINA Train with Active Lateral Secondary Suspension2010In: 8th International Conference on Railway Bogies and Running Gears, BOGIE '10, Budapest, Hungary, September 13-16, 2010., 2010Conference paper (Other academic)
    Abstract [en]

    This study describes the development of a system of active lateral secondary suspension (ALS) for commercial use. Simulations and on-track tests have been performed with a two-car REGINA train-set since 2007, using electro-hydraulic actuators together with sky-hook damping and a carbody centring Hold-Off Device to actively control the secondary suspension. Measurement results show that the ALS system significantly reduces the lateral dynamic carbody accelerations. Furthermore, the lateral quasi-static displacements between carbody and bogies in curves at high track plane accelerations are significantly reduced. Hence, lateral ride comfort is improved and higher speeds, particularly in curves, may be allowed. The satisfactory results have led to long-term tests in service operation, which are being carried out since the beginning of 2009.

  • 10. Orvnäs, Anneli
    et al.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Qazizadeh, Alireza
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    An active secondary suspension concept to improve lateral and vertical ride comfort2013In: 9th international conference on railway bogies and running gears, Budapest, September 9-12 / [ed] Prof. Istvan Zobory, Budapest, Hungary: Department of Railway vehicles, Aircraft and Ships at the BME , 2013, p. 86-88Conference paper (Refereed)
    Abstract [en]

    When the speed of a rail vehicle is increased, ride comfort is normally negatively affected. The suspensions of the vehicle have to be modified in order to compensate for the amplified vibrations in the carbody. However, the possibilities of improvement by means of conventional passive damping will eventually reach a limit. Therefore, active suspension technology in rail vehicles is considered to be an alternative solution, since it offers better options of improving the vehicle’s dynamic performance compared to conventional passive solutions.

    Although previous research has been performed concerning concepts of combined active lateral and vertical secondary suspension – by replacing the lateral and vertical dampers with actuators – no such concept known to the authors has been introduced for service implementation.

    This paper presents an active secondary suspension concept used to simultaneously improve lateral and vertical ride comfort. In the first phase of the research project, focus was on an active secondary suspension concept in the lateral direction (ALS), including dynamic and quasi-static lateral control of the carbody. Simulations were validated against running tests, showing significant ride comfort improvements. The ALS system will soon be taken into service operation.

    In the next phase of the project, simulations were performed with the active suspension device in the vertical direction (AVS), including dynamic vertical and quasi-static roll control of the carbody. The simulations performed with the AVS system indicated significant ride comfort improvements compared to the passive system.

    In the final phase of the project, the ALS and AVS systems are combined. Simulation results show that the active system significantly improves lateral and vertical ride comfort compared to a passive system. Further, by means of the quasi-static roll control of the carbody, higher speeds in curves can be allowed without negatively affecting ride comfort. Moreover, the active suspension concept reduces the influence on ride comfort caused by the air spring stiffness. This means that the total air spring volume can be reduced.

  • 11.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Motion sickness on-track testing2008In: Proceedings of the 43rd UK Conference on Human Response to Vibration, 2008Conference paper (Other academic)
    Abstract [en]

    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.

  • 12.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Research on the competitiveness of tilting trains2007In: Proceedings of Railway Engineering - 2007, Edinburgh: Engineering Technics Press , 2007Conference paper (Other academic)
    Abstract [en]

    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.

  • 13.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Tilting trains: benefits and motion sickness2010In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 224, no F6, p. 513-522Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Tilting trains: Enhanced benefits and strategies for less motion sickness2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 15.
    Persson, Rickard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Tilting trains: Technology, benefits and motion sickness2008Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    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.

  • 16.
    Persson, Rickard
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Kufver, Björn
    Strategies for less motion sickness on tilting trains2010In: Proceedings of Comprail 2010, Southampton: WIT Press , 2010, p. 581-591Conference paper (Other academic)
    Abstract [en]

    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).

  • 17.
    Persson, Rickard
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Kufver, Björn
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On-track test of strategies for less motion sickness on tilting trains.In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159Article in journal (Other academic)
    Abstract [en]

    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.

  • 18.
    Persson, Rickard
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Kufver, Björn
    Ferroplan Engn, Linkoping, Sweden.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    On-track test of tilt control strategies for less motion sickness on tilting trains2012In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 50, no 7, p. 1103-1120Article in journal (Refereed)
    Abstract [en]

    Carbody tilting is today a mature and inexpensive technology that permits higher train 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 optimised tilt angle. This is made possible by new tilt algorithms, storing track data and using a positioning system to select the appropriate data. The present paper reports from on-track tests involving more than 100 test subjects onboard a tilting train. A technical approach is taken evaluating the effectiveness of the new tilt algorithms and the different requirements on quasi-static lateral acceleration and lateral jerk in relative terms. The evaluation verifies 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 shows that reduced quantities of motions assumed to have a relation to motion sickness also lead to a reduction in experienced motion sickness. However, a limitation of applicability is found as the lowest risk of motion sickness was not recorded for the test case with motions closest to those of a non-tilting train. An optimal level of tilt, different from no tilt at all, is obtained. This non-linear relation has been observed by other researchers in laboratory tests.

  • 19.
    Qazizadeh, Alireza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On-Track Tests and Simulation of Active Secondary Suspension on a Rail Vehicle: Research, Development and Maintenance2014In: Proceedings of the Second International Conference on Railway Technology: Research, Development and Maintenance, Stirlingshire, UK: Civil-Comp Press , 2014, , p. 12Conference paper (Refereed)
    Abstract [en]

    Ride comfort is one of the important criteria when designing and approving a new train. This parameter is negatively affected by low track quality or by increased train speed. One way to improve ride comfort in such operation conditions is to use active suspension control. However, the solution needs to be economic and reliable to remain attractive to industry. In this paper such an active suspension is developed and tested in a collaboration between KTH and Bombardier. The active control is implemented by replacing secondary vertical and lateral dampers with actuators. Skyhook control theory is used in combination with mode separation to calculate the reference force to the actuators. A two carbody train set manufactured by Bombardier is used as a test train. One of the cars has conventional passive suspension and is used as a reference car and the other is equipped with active secondary lateral and vertical suspension. Before carrying out the measurements, different failure scenarios of the active suspension were defined and studied in the multi-body simulation software Simpack. Active secondary vertical and lateral suspensions were finally tested together for the first time in Sweden in May 2013. Measurements were performed at different speeds up to 200 km/h on tracks around Stockholm. The results show a significant reduction of the vibration level in the carbody. According to the comfort values, up to 44% improvement is achieved.

  • 20.
    Qazizadeh, Alireza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, Rickard
    Rolling Stock Central & Northern Europe and Asia, Sweden.
    Proposal for systematic studies of active suspension failures in rail vehicles2018In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 232, no 1, p. 199-213Article in journal (Refereed)
    Abstract [en]

    Application of active suspensions in high-speed passenger trains is gradually getting more and more common. Active suspensions are primarily aimed at improving ride comfort, wear or stability. Failure of these systems may not only just deteriorate the performance but it may also put vehicle safety at risk. There are not many studies that explain how a thorough study proving safety of active suspension should be performed. Therefore, initiating this type of study is necessary for not only preventing incidences but also for assuring acceptance of active suspension by rail vehicle operators and authorities. This study proposes a flowchart for systematic studies of active suspension failures in rail vehicles. The flowchart steps are solidified by using failure mode and effects analysis and fault tree analysis techniques and also acceptance criteria from the EN14363 standard. Furthermore, six failure modes are introduced which are very general and their use can be extended to other studies of active suspension failure. In the last section of the paper, the proposed flowchart is put into practice through four failure examples of active vertical suspension.

  • 21.
    Stichel, Sebastian
    et al.
    Bombardier Transportation, Västerås, Sweden .
    Persson, Rickard
    Bombardier Transportation, Västerås, Sweden .
    Himmelstein, Günther
    Andersson, Evert
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Development of Next Generation High-Speed Trains for Scandinavia2009In: Proceedings of the 12th International Conference on Civil, Structural and Environmental Engineering Computing, 2009Conference paper (Refereed)
    Abstract [en]

    This paper describes the development of new running gear technology for future high-speed trains within the Swedish development programme Gröna Tåget (Green Train). Three different technologies are developed and tested: a passive radial self-steering "soft" bogie, an active lateral suspension including also a Hold-Off-Device function and a mechatronic bogie actively controlling the wheelset motions with actuators attached to the bogie frame. In contrast to other high-speed train developments, focus is here the challenge of balancing the contradictory demands of good running behaviour at high speeds on straight track on the one hand and good curving performance with low track and wheel damage and maintained good ride comfort on the other hand. Results are presented which confirm that all three technologies in almost all aspects meet the goals set up in the beginning of the project.

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