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  • 101.
    Lukaszewicz, Piotr
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Running resistance - results and analysis of full-scale tests with passenger and freight trains in Sweden2007In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 221, no 2, p. 183-193Article in journal (Refereed)
    Abstract [en]

    This paper presents experimental results of running resistance tests. Running resistance is determined for conventional passenger trains, freight trains, and the X2 high-speed train. The influence of variables such as speed, number of axles, number of coaches, axle load, track type, and train length is studied. The running resistance is expressed in a general form by a second degree polynomial. The three terms in the polynomial are functions of these variables. The magnitude of the first term is speed independent and varies with number of axles, axle load, and type of track. The second term varies with speed and train length. No influence of axle load is distinguished. The third term is related to the air drag and varies with the speed squared and train configuration. It can be divided into two parts. One part is constant and depends upon the front and rear of the train, and another part increases approximately linearly with train length.

  • 102.
    Lukaszewicz, Piotr
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Running resistance and energy consumption of ore trains in Sweden2009In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 223, no 2, p. 189-197Article in journal (Refereed)
    Abstract [en]

    Running resistance of ore trains consisting of Uad-type wagons is determined from full-scale measurements on Malmbanan. Tests are also run in curves with the Uad equipped with three piece bogies where the axles are non-steerable and an ore wagon equipped with bogies allowing the axles to better align themselves on straight track and more radially in curves, thus making them steerable. Influence of speed, axle load, curve radii, and train length is studied and quantified. The running resistance is parameterized and expressed in a general way so that it can be calculated for any Swedish ore train consisting of Uad-type wagons. The study shows that the increase in running resistance is linear due to the increasing axle load on tangent track and train length. The increase in resistance due to curves is significant and increases as the curve radius decreases. If the axles align themselves radially, the curve resistance reduces by 40 per cent, compared with the Uad. The results show which parameters in a running resistance formula should be paid extra attention when constructing a train model for simulation purposes. A comparison is made between ore trains and ordinary Swedish loco-hauled freight trains. The energy consumption of an ore train is not much affected if the operational speed increases from 50 to 60 km/h. Also, a reduced aerodynamic drag has a very little effect on the consumption due to the low operational speed. In this article, a review of the study is made with conclusions.

  • 103.
    Lönnbark, Gustav
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Characterization of Track Irregularities With respect to vehicle response2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis a study, investigating the correlation between vehicle/track forces and track irregularities, is presented. The aim is to see if the correlation increases, using the first and second order derivatives of the track irregularities instead of the amplitude of the irregularities themselves. Data from on track tests during the DynoTRAIN measurement campaign is used as input to a MatLab program. The program processes the data with filtering and calculation of the derivatives, as well as a meter-by-meter alignment of the parameters. A linear regression analysis is done and the results are presented in scatter diagrams along with their correlation coefficients. The results are inconclusive implying that there are more parameters affecting the results than the ones analyzed, suggesting multidimensional regression analysis to be used.

  • 104.
    Martin, Michael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    The Effect of Geometrical Contact Input to Wheel-Rail Contact Model2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wheel-rail contact is an important aspect of railway, the forces transferred between the wheel and rail are the one that guide, brake, or accelerate the train, and that is why the understanding of the contact between wheel and rail is an interesting research topic. In this master thesis wheel-rail contact model named ANALYN is used to see the effect of the different geometrical input, like undeformed distance, relative longitudinal curvature, and relative lateral curvature calculation affect the contact patch estimation formed at the wheel-rail contact. 

    In the process, a geometrical contact search code is made to find the contact point between wheel and rail for certain lateral displacement, yaw angle, and roll angle of the wheelset. The codes used to calculate the three geometrical inputs are also prepared, with two methods are prepared for each input. The results that generated from combination of the geometrical contact search and geometrical input preparation are used as the input to ANALYN.

    The results showed that different geometrical input calculations do affect the shape of the contact patch, with the calculation of lateral curvature being the most important since it affects the shape of the contact patch greater than other geometrical inputs. It is also shown that taking yaw angle into account in the contact search will affect the shape of the contact patch.

  • 105.
    Odermatt, Irene
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Implementation of novel wearprediction methodology fordamage calculation in rail vehicles2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The discretisation of the track network and the operating conditionsis an important part of a wear calculation. Due to computational costrepresentative track parts and conditions are selected to be simulated.The characteristic point method provides a set of simulation cases withdifferent curvatures and non-compensated accelerations. The severityof wear as a function of curvature is considered by the energy dissipationbetween rail and wheel. Quasi-static multibody simulations witha Bo’Bo’ vehicle and ideal track are run in GENSYS. The normal forcesare calculated with Hertz’ theory. The tangential contact problem issolved with FaStrip, a combination of FASTSIM and Strip theory. Wearis calculated with Archard’s formula. In order to simplify the implementation,wear is calculated only for one step of a full wear calculationwithout wheel profile updating. The result for the total weardepth over the wheel profile shows two peaks, at the flange and atthe wheel tread. Further research should show the influence of usingquasi-static instead of dynamics simulations with track irregularities.

  • 106.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Active Secondary Suspension in Trains: A Literature Survey of Concepts and Previous Work2008Report (Other academic)
  • 107.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Methods for Reducing Vertical Carbody Vibrations of a Rail Vehicle: A Literature Survey2010Report (Other academic)
    Abstract [en]

    The trend towards higher rail vehicle speeds generally results in increased vibrations in the carbody, which has a negative impact on ride comfort. Carbody vibrations can be reduced either by focusing on the structural stiffness of the system or by optimizing the damping components. When a conventional passive damping system cannot be further optimized, active components can be a solution to achieve improvements.

    Previous research concerning active control in rail vehicles to improve ride comfort show that significant benefits may be gained compared to a passive system. The overall goals are normally to improve, or at least maintain, ride comfort at increased vehicle speed or when running on tracks of inferior quality. Therefore, active suspension can be regarded as a cost-efficient solution if vehicle speed can be increased or track maintenance costs can be minimised. However, despite satisfactory results throughout the years, active suspension in rail vehicles has not yet made a convincing breakthrough in operational use. The main reason for the lack of success is most likely that the solutions offered so far have been too expensive in relation to the benefits gained.

    The purpose of this literature survey is to give an overview of previous studies regarding methods to passively or actively achieve vertical vibration reduction in a rail vehicle. The main focus is on active components.

  • 108.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    On Active Secondary Suspension in Rail Vehicles to Improve Ride Comfort2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One way to make rail vehicles a competitive means of transportation is to increase running speed. However, higher speeds usually generate increased forces and accelerations on the vehicle, which have a negative effect on ride comfort. With conventional passive suspension, it may be difficult to maintain acceptable passenger comfort. Therefore, active technology in the secondary suspension can be implemented to improve, or at least maintain, ride comfort at increased vehicle speeds or when track conditions are unfavourable.

    This thesis describes the development of an active secondary suspension concept to improve ride comfort in a high-speed train. Firstly, an active lateral secondary suspension system (ALS) was developed, including dynamic control of the lateral and yaw modes of the carbody. Furthermore, quasi-static lateral carbody control was included in the suspension system in order to laterally centre the carbody above the bogies in curves at high track plane acceleration and hence to avoid bumpstop contact. By means of simulations and on-track tests, it is shown that the ALS system can offer significant lateral ride comfort improvements compared to a passive system.

    Two different control strategies have been studied—the relatively simple sky-hook damping and the multi-variable H∞ control—using first a quarter-car and then a full-scale vehicle model. Simulation results show that significant ride comfort improvements can be achieved with both strategies compared to a passive system. Moreover, H∞ control in combination with the carbody centring device is better at reducing the relative lateral displacement in transition curves compared to sky-hook damping.

    Secondly, an active vertical secondary suspension system (AVS) was developed, using simulations. Dynamic control of the vertical and roll modes of the carbody, together with quasi-static roll control of the carbody, show significant vertical ride comfort improvements and allow higher speeds in curves. Further, the AVS system compensates for negative ride comfort effects if the structural stiffness of the carbody is reduced and if the vertical air spring stiffness is increased.

    Finally, the two active suspension systems (ALS and AVS) were combined in simulations. The results show that both lateral and vertical ride comfort is improved with the active suspension concept at a vehicle speed of 250 km/h, compared to the passive system at 200 km/h. Further, active suspension in one direction does not affect the other direction. The ALS system has been included in two recent orders comprising more than 800 cars.

  • 109.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Simulation of Rail Wear on the Swedish Light Rail Line Tvärbanan2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rail wear can result in extensive costs for the track owner if it is not predicted and preventedin an efficient way. To limit these costs, one measure is to predict rail wear through wear simulations. The purpose with this work is to perform simulations of successive rail wear on the Swedish light rail line Tvärbanan in Stockholm, by means of the track-vehicle dynamics software GENSYS in combination with a wear calculation program developed in MATLAB.

    The simulation procedure is based on a methodology with a simulation set design, where the simulations to be performed are selected through a parametric study. The simulations include track-vehicle simulations, where the wheel-rail contact is modelled according to the Hertzian contact theory together with Kalker’s simplified theory (including the numerical algorithm FASTSIM). The results from the track-vehicle simulations serve as input to the wear calculations. When modelling rail wear Archard’s wear model has been used, including wear coefficients based on laboratory measurements. The measurements have been performed under dry conditions, so the wear coefficients under lubricated conditions (both natural and deliberate lubrication) are reduced by factors estimated by field observations. After the wear depth calculations the wear distribution is smoothed and the rail profile is updated. The simulation procedure continues with a new wear step as long as the desired tonnage is not attained.

    Four curves of Tvärbanan with different curve radii, ranging from 85 to 410 m, have beenstudied in this work. On three of the curves the high rail is deliberately lubricated, whereas no lubrication has been applied in the widest curve. The vehicle operating the light rail line is an articulated tram with two motor end bogies and one intermediate trailer bogie. The line was opened in August 1999 and extended in one direction one year later. Rail profile measurements have been carried out by SL since March 2002. The traffic tonnage at the selected sites from the opening of the line to the last measurement occasion (September2004) is at most 8.9 mega gross ton per track.

    The results of the rail wear prediction tool are evaluated by comparing worn-off area of the simulated rail profiles with that of the measured rail profiles. Simulated and measured resultsdo not agree too well, since the simulated rail wear is more extensive than the measured one, especially on the outer rail. However, the shapes of the simulated worn rail profiles are comparable to those of the measured rail profiles.

  • 110.
    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)
  • 111.
    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. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Persson, Rickard
    Active Lateral Secondary Suspension with H∞ Control to Improve Ride Comfort: Simulations on a Full-Scale Model2011In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 49, no 9, p. 1409-1422Article in journal (Refereed)
    Abstract [en]

    In this study, a full-scale rail vehicle model is used to investigate how lateral ride comfort is influenced by implementing the H and sky-hook damping control strategies. Simulations show that significant ride comfort improvements can be achieved on straight track with both control strategies compared with a passive system. In curves, it is beneficial to add a carbody centring Hold-Off Device (HOD) to reduce large spring deflections and hence to minimise the risk of bumpstop contact. In curve transitions, the relative lateral displacement between carbody and bogie is reduced by the concept of H control in combination with the HOD. However, the corresponding concept with sky-hook damping degrades the effect of the carbody centring function. Moreover, it is shown that lateral and yaw mode separation is a way to further improve the performance of the studied control strategies.

  • 112.
    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. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Persson, Rickard
    An Active Secondary Suspension Concept to Improve Lateral and Vertical Ride ComfortIn: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423Article in journal (Other academic)
    Abstract [en]

    This paper presents an active secondary suspension conceptfor lateral and vertical ride comfort improvement in arail vehicle. Dynamic control of the lateral, yaw and verticalcarbody modes is achieved by means of actuators replacingthe conventional lateral and vertical dampers in the secondarysuspension. Active damping significantly improveslateral and vertical ride comfort compared to a passive system.Besides dynamic control, the actuators can generatequasi-static lateral and roll control of the carbody. This allowsfor higher speeds in curves, without negatively affectingride comfort. Furthermore, the active suspension concept reducesthe influence on ride comfort caused by the air springstiffness. This means that the total air spring volume can bereduced.

  • 113.
    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. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Persson, Rickard
    Aspects of Using Active Vertical Secondary Suspension to Improve Ride Comfort2011In: 22nd International Symposium on Dynamics of Vehicles on Roads and Tracks, IAVSD'11, 2011Conference paper (Other academic)
    Abstract [en]

    This paper presents various aspects of using active vertical secondary suspension in a rail vehicle to improve ridecomfort. Dynamic control of the vertical and roll modes of the carbody is achieved by means of actuators replacingthe conventional vertical dampers in the secondary suspension. Active damping improves vertical ride comfort,compared to a passive system. Besides dynamic control, the actuators are able to generate quasi-static roll controlbetween the carbody and bogies in curves. This allows for higher speeds in curves, without negatively affecting ridecomfort.

  • 114.
    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. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Persson, Rickard
    Aspects of Using Active Vertical Secondary Suspension to Improve Ride ComfortIn: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017Article in journal (Other academic)
    Abstract [en]

    This paper presents various aspects of using active vertical secondary suspension in arail vehicle to improve ride comfort. Dynamic control of the vertical and roll modes ofthe carbody is achieved by means of actuators replacing the conventional vertical dampersin the secondary suspension. Active damping improves vertical ride comfort, compared toa passive system. Besides dynamic control, the actuators are able to generate quasi-staticroll control between the carbody and bogies in curves. This allows for higher speeds incurves, without negatively affecting ride comfort. Furthermore, the anti-roll bar is removedto reduce the number of components.

  • 115.
    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.

  • 116.
    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.

  • 117.
    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)
  • 118.
    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.

  • 119.
    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.

  • 120. 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.

  • 121.
    Ouyang, Zhan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Investigation of Causes for Wheel Squeal on Roslagsbanan in Stockholm 2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this work is to investigate the possible causes of wheel squeal on Roslagsbanan, a

    narrow gauge (891mm) suburban railway system in Stockholm, Sweden. Simulation of the dynamic behaviour of vehicles negotiating curves was carried out by means of the Swedish multibody simulation software GENSYS [1].

    Wheel squeal may arise due to insufficient radial steering capability of the vehicles in curves causing too high levels of creep (relative sliding) in the wheel/rail-contact. Based on this theory, an advanced model of the creep-creep force relation was introduced. In this model the creep force decreases after creep reaches a certain level, called critical creep. It is believed that wheel squeal occurs after the creep level exceeded the critical creep value.

    Measured rail profiles of the curve together with measured wheel profiles were used as wheel/rail geometry input data. Other interesting parameters for the simulations, such as friction coefficient, primary suspension stiffness and damping, vehicle speed, braking/acceleration were varied and their effects on the outcome were tested.

    Worn wheels on newly grinded and worn rails under dry conditions are most likely to generate curve squeal. We believe the long term solution for Roslagsbanan is to grind the rail profiles into a shape more similar to the 50E3 with inclination 1/40. This will give a more even wheel wear over the whole wheel surface. However, curves below ca 300 m cannot be negotiated without wheel squeal, why all

    curves on the track tighter than ca 300 m have to be lubricated.

  • 122. Persson, Richard
    et al.
    Andersson, Evert
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Bogies towards higher speed on existing tracks2014In: International Journal of Rail transportation, ISSN 2324-8378, E-ISSN 2324-8386, Vol. 2, no 1, p. 40-49Article in journal (Refereed)
    Abstract [en]

    Running faster on existing tracks is a common operator’s wish that should be set in relation to the necessary infrastructure maintenance costs for track quality enhancement. Designing a track-friendly running gear that exerts moderate forces on the track is a key to relax this relation. A design providing good ride quality even on non-perfect track is preferred to avoid excessive track maintenance costs when speeds are higher. This paper describes how simulations and tests have been performed to optimise certain parts of a high-speed bogie. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering in common curve radii, which in combination with appropriate yaw damping ensures stability at higher speeds. It also includes active secondary suspension to further ease the maintenance requirements on the track and/or to improve ride quality. This bogie has been tested and approved according to EN 14363 for a service speed of 250 km/h in combination with enhanced curving speed. Both simulations and recently performed on-track tests further showed that the ride comfort with active secondary suspension at 250 km/h can be at least as good as with passive suspensions at 200 km/h.

  • 123.
    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.

  • 124.
    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.

  • 125.
    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.

  • 126.
    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.

  • 127.
    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.

  • 128.
    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).

  • 129.
    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.

  • 130.
    Pintado, P.
    et al.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    Ramiro, C.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Morales, A. L.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    Nieto, A. J.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    Chicharro, J. M.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    Miguel de Priego, J. C.
    Patentes Talgo, Paseo Tren Talgo 2, Madrid 28290, Spain..
    Garcia, E.
    Univ Castilla La Mancha, Dept Mech Engn, Ave Camilo Jose Cela S-N, E-13071 Ciudad Real, Spain..
    On the mechanical behavior of rubber springs for high speed rail vehicles2018In: Journal of Vibration and Control, ISSN 1077-5463, E-ISSN 1741-2986, Vol. 24, no 20, p. 4676-4688Article in journal (Refereed)
    Abstract [en]

    There are many engineering design problems that call for rubber components as the best solution. Vulcanized rubber has found its way into all sorts of devices, from the universal automobile pneumatic tire to the ubiquitous compliant bushing. Some high-speed rail vehicle suspensions make use of rubber, not only in the air spring itself, but also in the auxiliary spring. The mechanical characteristics of this component influence vehicle dynamics and, therefore, accurate spring models with which to conduct dynamic analysis would make for powerful design tools. Nevertheless, the mechanical behavior of rubber defies simple modeling on account of stress relaxation, creep, set, viscosity, internal friction, and nonlinear stress-strain relations. Despite the advances in the micromechanical understanding of these phenomena, as well as in the macroscopic modeling of rubber spring behavior, there is ample room for refinement, and this is precisely the goal of this paper. The mechanical behavior of a particular rubber spring for high speed rail vehicles has been characterized. The results reveal the necessary components of the model, and suggest the appropriate procedure for parameter extraction. Our model proposal consists of three elements in parallel: a nonlinear elastic spring; a soft friction element; and a Maxwell viscous component. The characterization procedure takes into account both stress relaxation and nonlinear elasticity. The proposed model accurately reproduces experimental results and may then be used with confidence in any type of numerical simulation. Nevertheless, for this statement to be true, the problem of numerical softening potentially induced by soft friction models should be resolved. The paper will show that a trailing moving average filter, seamlessly tied to the model, wipes out the softening effect.

  • 131.
    Prevolnik, Robin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On estimating the risk of wheel damage for wagons with paper rolls considering various dynamic conditions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hector Rail AB is a Swedish line haul provider for the European Rail Transport Market. On one of their lines, Hector Rail transports large cylinder-shaped paper rolls of different sizes from Holmsund to Skövde, and compressed recycled paper back to Holmsund, with Y25 bogie wagons. The wheels of these wagons experience surface initiated rolling contact fatigue, RCF, which is increasing the maintenance cost. In a collaboration with KTH Royal Institute of Technology a study of the risk of developing RCF cracks when comparing different track qualities, load cases, speeds, curves and wheel-rail friction coefficients as well as the consideration of wear is carried out.

    The difference in surface initiated RCF when applying the different input parameters is analysed. The location along the track where the wheels are likely to initiate RCF is calculated, as well as the location of RCF on the wheels. The model also provides the curve characteristics that are most likely to initiate RCF on the wheels. This tool can be used for optimising and further streamlining the operation for freight traffic on this (or any other) line with respect to wheel damages and planned maintenance.

  • 132.
    Prevolnik, Robin
    et al.
    Alten Sweden.
    Casanueva, Carlos
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Hossein Nia, Saeed
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On estimating the risk of wheel damage for wagons with paper rolls considering various dynamic conditions2017In: Proceedings of the 11th International Heavy Haul Association Conference IHHA, 2017Conference paper (Refereed)
    Abstract [en]

    Hector Rail AB is a Swedish line haul provider for the European Rail Transport Market. On one line, Hector Rail transports large cylinder-shaped paper rolls of different sizes from Holmsund to Skövde, and compressed recycled paper shaped as cubes back to Holmsund. The wheels of their Y25 bogie wagons are experiencing surface initiated rolling contact fatigue (RCF), which is increasing the maintenance cost and sometimes interrupting the time schedule. In a collaboration with KTH Royal Institute of Technology a study of the risk of developing RCF cracks when comparing different track qualities, load cases, speeds, curves and wheel-rail friction coefficients as well as the consideration of wear is carried out. The results show the difference in surface initiated RCF when applying the different input parameters, including the location along the track where the wheels are likely to initiate RCF, as well as the location of RCF on the wheels. The model also provides the curve cases where the wheels are most likely to initiate RCF. This tool can be used for optimising and further streamlining the operation for freight traffic on any line with respect to wheel damages and planned maintenance.

  • 133.
    Pálinkó, Márton
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Estimation of wheel-rail friction at vehicle certication measurements2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. Behaviour on straight and curved tracks, including twisted tracks at various speeds, is of great importance. However, the wheel-rail friction should always be high corresponding to dry conditions. It means that the certification tests have to be carried out during dry weather conditions and unlubricated rails. But measuring the friction at test conditions is a great challenge.Therefore, in a recent work (Petrov et al.), an algorithm was proposed for the continu-ous estimation of wheel-rail friction along both rails. The algorithm is based on wheel-rail forces in all three directions (Y, Q, X ) for both wheels in a wheelset, lateral contact po-sition on its wheels and wheelset angle of attack. The algorithm was evaluated with a fictional vehicle with vehicle-track dynamics simulations on various tracks (straight and curves) and track irregularities.In cooperation with SNC Lavalin (formerly Interfleet Technology), an opportunity arose to get the required data from on-track tests. In this way, all nine quantities above were measured during test runs of a new vehicle, so the algorithm could be evaluated under realistic conditions. The tests in tight curves of radius 150 m are used in the present work for this purpose. The measured data and the algorithm were processed in a Matlab program to get the friction estimate. Apart from the friction, the creepages and spin are also estimated with the aim to serve as quality indicators of the estimated friction.As the vehicle measurements include noise, errors and uncertainties, a statistical tool was introduced. Moreover, a sensitivity analysis was performed. It was observed that in these tight curves, the friction estimation on the outer wheel is poor, but a phenomenon arose that with increasing spin corresponding to even higher contact angle the friction might be estimated again. However, small spin gives a good friction estimation provided the total creep is high enough. Therefore, sharp curves, traction/braking or large track irregularities are necessary to estimate the friction well.In order to continue the work deeper into the area, other tests with the above scenarios would be useful

  • 134.
    Qazizadeh, Alireza
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Development and on-Track Tests of Active Vertical Secondary Suspension for Passenger Trains2014Licentiate thesis, comprehensive summary (Other academic)
  • 135.
    Qazizadeh, Alireza
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On Active Suspension in Rail Vehicles2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The topic of this PhD thesis is active suspension in rail vehicles whichis usually realized through sensors, controllers and actuation components.A well established example of an active suspension is the tiltingcontrol system used to tilt the carbody in curves to reduce centrifugalacceleration felt by passengers. Active suspension for rail vehicles is beingstudied since 1970s and in this PhD thesis it has been tried to expandon some aspects of this topic.This study extends the research field by both experimental and theoreticalstudies. In the first phase of the study which led to a licentiatedegree the focus was more on experimental work with active verticalsuspension (AVS). This was implemented by introducing actuators inthe secondary suspension of a Bombardier test train, Regina 250, in thevertical direction. The aim has been to improve vertical ride comfort bycontrolling bounce, pitch and roll motions.In the second phase after the licentiate, the studies have been moretheoretical and can be divided into two parts. The first part of the workhas been more focused on equipping two-axle rail vehicles with differentactive suspension solutions for improving the vehicle performanceregarding comfort and wheel-rail interaction. Three papers are writtenon active suspension for two-axle rail vehicles. Two of the papers discussthe use of H¥ control for wheelset guidance in curves to reducewheel-rail damage. The third paper shows that by use of active verticaland lateral suspension (AVS and ALS) in two-axle rail vehicles goodcomfort can be achieved as well. The paper then studies how the threeactive suspension systems (ALS, AVS, and ASW) interact once implementedtogether on a two-axle rail vehicle.The second part is a study on safety of active suspension systems.The study discusses a possible procedure to ensure that a designed activesuspension for a rail vehicle will be safe in all possible failure situations.

  • 136.
    Qazizadeh, Alireza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, R.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On-Track Tests of Active Vertical Suspension on a Passenger Train2015In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 53, no 6, p. 798-811Article in journal (Refereed)
    Abstract [en]

    The classic way to design the suspension of a rail vehicle is to use passive elements such as dampers and springs; however, as sensors and actuators are getting more affordable and reliable, their potential benefit in the suspension system is increasingly studied. Active suspension can be used to keep ride comfort at an acceptable level or even improve it, while allowing tougher operation conditions or usage of lighter carbodies. Tougher conditions could be interpreted as higher speed or lower track quality, and lighter carbody means higher level of elastic vibrations. This paper is focused on the implementation and tests of active vertical suspension on the secondary suspension of a high-speed passenger electric multiple unit using hydraulic actuators and the skyhook method as the controller. Results from on-track tests indicate large ride comfort improvements.

  • 137.
    Qazizadeh, Alireza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, R.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Preparation and Execution of On-track Tests with Active Vertical Secondary Suspension2015In: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602XArticle in journal (Other academic)
  • 138.
    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.

  • 139.
    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.
    Active Lateral and Active Wheelset Steering Interference2017In: / [ed] Wanming Zhai, China, 2017Conference paper (Refereed)
    Abstract [en]

    Two-axle rail vehicles with only one level of suspension started operation in light traffic in the early 1930s. These vehicles were known to be cheap, light, and easy to maintain which made them suitable for parsley populated regional traffic. However, their limitations prevailed over their advantages which finally led to the extinction of these vehicles. These limitations were poor wheel-rail interaction, low capacity, and low comfort. Poor wheel-rail interaction which led to high wear and squeal noise on curves and low hunting speed on straight track was one of the major drawbacks. KTH rail vehicle division suggests reviving the old two-axle rail vehicle and improving its performance by introducing active suspension systems. Studies so far include improving ride comfort by active lateral and vertical suspension and active wheelset steering to improve curving and reduce wear. However, wheelset steering is not yet implemented together with active lateral and vertical suspension. Implementing them together can cause that the systems interfere in each other’s objectives. Hence it is necessary to study the interaction between the three systems. Results show that introducing active wheelset steering has a negative effect on the lateral comfort while active lateral suspension does not show significant effect on the wear performance of active wheelset steering. The study concludes that a vehicle with all the three active suspension systems included can improve all the three intended performances (lateral-vertical comfort and wheel wear) compared to the passive vehicle.

  • 140.
    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.
    IMPROVED CURVING PERFORMANCE FOR TWO-AXLE RAIL VEHICLES WITH ACTUATED SOLID WHEELSETS USING H-infinity CONTROL2016In: PROCEEDINGS OF THE ASME JOINT RAIL CONFERENCE, 2016, AMER SOC MECHANICAL ENGINEERS , 2016Conference paper (Refereed)
    Abstract [en]

    Application of active suspension on passenger vehicles has engaged many vehicle dynamics specialists in recent years. The technology can be used for different purposes including improving comfort, stability or wear behavior. Despite these benefits, industries do not yet find these technologies attractive enough. One reason is that the achieved benefits do not pay back for itself since the vehicle will become more expensive. Therefore, more steps should be taken to make active suspension attractive. One such a step can be using active suspension for resolving classical limitations in rail vehicle dynamics. An example of this is a non-bogie rail vehicle with two axles. One of the problems associated with these vehicles is their short axle distance limiting the length of the vehicle. The short axle distance is partly for limiting wheel-rail wear. This paper describes how to reduce wheel wear through achieving better wheelset steering in curves so that longer axle distances can be allowed. Wheelset steering is performed by H-infinity control strategy.

  • 141.
    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.
    Interference of active comfort and wheelset stability controllers2018In: The Dynamics of Vehicles on Roads and Tracks, CRC Press/Balkema , 2018, p. 741-746Conference paper (Refereed)
    Abstract [en]

    KTH railway group intends to revive the old two-axle rail vehicle concept and reintroduce it as a modern passenger vehicle with the operational speed up to 200 km/h. Two-axle rail vehicles are cheap, light and easy to maintain but have different running limitations. Different active suspension technologies can be used to improve on these limitations. One challenge with introducing different active suspension systems on vehicles with just one level of suspension is the high risk of active systems interfering in each other’s objectives. This study investigates the interference of active comfort and wheelset stability controllers.

  • 142.
    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.
    Feyzmahdavian, Hamid Reza
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Wheelset curving guidance using H∞ control2018In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 56, no 3, p. 461-484Article in journal (Refereed)
    Abstract [en]

    This study shows how to design an active suspension system for guidance of a rail vehicle wheelset in curve. The main focus of the study is on designing the controller and afterwards studying its effect on the wheel wear behaviour. The controller is designed based on the closed-loop transfer function shaping method and (Formula presented.) control strategy. The study discusses designing of the controller for both nominal and uncertain plants and considers both stability and performance. The designed controllers in Simulink are then applied to the vehicle model in Simpack to study the wheel wear behaviour in curve. The vehicle type selected for this study is a two-axle rail vehicle. This is because this type of vehicle is known to have very poor curving performance and high wheel wear. On the other hand, the relative simpler structure of this type of vehicle compared to bogie vehicles make it a more economic choice. Hence, equipping this type of vehicle with the active wheelset steering is believed to show high enough benefit to cost ratio to remain attractive to rail vehicle manufacturers and operators. 

  • 143.
    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.
    Feyzmahdavian, Hamid Reza
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Wheelset Curving Guidance Using H_infinity ControlIn: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159Article in journal (Other academic)
    Abstract [en]

    This study shows how to design an active suspension system for guidance of a rail vehiclewheelset in curve. The main focus of the study is on designing the controller and afterwardsstudying its eect on the wheel wear behavior. The controller is designed based on theclosed-loop transfer function shaping method and H1 control strategy. The study discussesdesigning of the controller for both nominal and uncertain plants and considers both stabilityand performance. The designed controllers in Simulink are then applied to the vehicle modelin Simpack to study the wheel wear behavior in curve. The vehicle type selected for thisstudy is a two-axle rail vehicle. This is because this type of vehicle is known to have verypoor curving performance and high wheel wear. On the other hand, the relative simplerstructure of this type of vehicle compared to bogie vehicles make it a more economic choice.Hence, equipping this type of vehicle with the active wheelset steering is believed to show highenough benet to cost ratio to remain attractive to rail vehicle manufacturers and operators.

  • 144.
    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, R.
    Studying Variations of Skyhook Method for Comfort ImprovementManuscript (preprint) (Other academic)
  • 145.
    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, R.
    Studying variations of skyhook method for comfort improvement2015In: Stephenson Conference Research for Railways 2015, Institution of Mechanical Engineers , 2015, p. 275-285Conference paper (Refereed)
    Abstract [en]

    To improve ride comfort on high speed passenger trains, active suspension technology can be used. An active secondary suspension is already developed for a Regina 250 EMU within a collaboration between KTH and Bombardier. Vertical dampers were replaced by four vertical actuators and the skyhook method was used to calculate reference forces for actuators. The basic idea of the skyhook method is that the force is proportional to the absolute velocity. The idea with this study is to explore variations of the skyhook method where the actuator force is proportional to other kinematic variables than just the absolute velocity of the carbody. These variables could be e.g. carbody-bogie relative position, carbodybogie relative velocity, carbody acceleration square etc. The aim of this study is to investigate possible advantages of these variations in improving ride comfort and carbody positioning compared to the original skyhook concept. Simulation results show that there are variations which perform better than the original skyhook method and improve either ride comfort or the relative displacement between carbody and bogie. 

  • 146.
    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.

  • 147.
    Quezada Guzmán, Felipe
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Continuous optimisation of passenger ride comfort and wheel/rail wear through the genetic algorithm2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The performance of a rail system can be severely affected if the track where the rail vehicle is intended to run is in very bad condition. In this case, a train could easily exceed the acceleration limit if a particular track section is sufficiently damaged. A modification of the suspension parameters could reduce the acceleration in that single section but also affect negatively the ride comfort for the rest of the network.

    The purpose of the present work is to develop a tool in MATLAB that allows a continuous optimisation of the passenger ride comfort and the wheel/rail wear of Alstom trams Citadis X05 for a specific track, speed profile and design parameters designated by the user. The track where the rail vehicles are intended to run will be divided into sections depending on the track geometry and track quality. The optimisation will be carried out through a genetic algorithm.

    The thesis work is divided into modelling, recognition of parameters and optimisation. The modelling of Citadis X05 is performed by GENSYS. This part includes a validation phase of the model. In the second phase, a sensitivity study is undertaken with the aim of identifying the design parameters that could have an impact on passenger ride comfort and wheel/rail wear. Finally, the implementation of the genetic algorithm and the development of a graphical user interface (GUI) in MATLAB is carried out.

    A simulation for two sections of a track has shown an improvement of the passenger ride comfort and wheel/rail wear for both sections. Furthermore, the algorithm provided different combinations of parameters that yielded in the same optimal solution, and thus more alternatives. Although the results are positive, the obtained set of design parameters must go through exhaustive tests to assure that both the operational and safety requirements are still fulfilled. Therefore, for further work, it is important to consider other aspects in the optimisation problem to enhance the reliability of solutions obtained by the algorithm. Furthermore, the addition of more design parameters such as geometric parameters and inertial property parameters can give us new, interesting results and approaches.

  • 148.
    Robla Sánchez, Ignacio
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Wheel Wear Simulation of the Light Rail Vehicle A322010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the last decade, a novel methodology for wheel wear simulation has been developed in Sweden. The practical objective of this simulation procedure is to provide an integratedengineering tool to support rail vehicle design with respect to wheel wear performance and detailed understanding of wheel-rail interaction. The tool is integrated in a vehicle dynamicssimulation environment.The wear calculation is based on a set of dynamic simulations, representing the vehicle, the network, and the operating conditions. The wheel profile evolution is simulated in an iterativeprocess by adding the contribution from each simulation case and updating the profile geometry.The method is being validated against measurements by selected pilot applications. To strengthen the confidence in simulation results the scope of application should be as wide aspossible in terms of vehicle classes. The purpose of this thesis work has been to try to extend the scope of validation of this method into the light rail area, simulating the light rail vehicleA32 operating in Stockholm commuter service on the line Tvärbanan.An exhaustive study of the wear theory and previous work on wear prediction has been necessary to understand the wear prediction method proposed by KTH. The dynamicbehaviour of rail vehicles has also been deeply studied in order to understand the factors affecting wear in the wheel-rail contact.The vehicle model has been validated against previous studies of this vehicle. Furthermore new elements have been included in the model in order to better simulate the real conditionsof the vehicle.Numerous tests have been carried out in order to calibrate the wear tool and find the settings which better match the real conditions of the vehicle.Wheel and rail wear as well as profile evolution measurements were available before this work and they are compared with those results obtained from the simulations carried out.The simulated wear at the tread and flange parts of the wheel match quite well the measurements. However, the results are not so good for the middle part, since themeasurements show quite evenly distributed wear along the profile while the results from simulations show higher difference between extremes and middle part. More tests would benecessary to obtain an optimal solution.

  • 149.
    S. Sichani, Matin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Enblom, Roger
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Comparison of Non-elliptic Contact Models: Towards Fast and Accurate Modelling of Wheel-Rail Contact2012In: Proceeding of 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, 2012, p. 120-128Conference paper (Refereed)
    Abstract [en]

    The demand to investigate and predict the surface deterioration phenomenain the wheel-rail interface necessitates fast and accurate contact modelling.During the past twenty years, there have been attempts to determine more realisticcontact patch and stress distributions using fast non-iterative methods.The main aim of the present work is to compare some of these state-of-theart,non-elliptic contact models available in the literature. This is consideredas the first step in introducing a fast and accurate non-elliptic contact modelthat can be used on-line with vehicle dynamics analysis. Three contact models,namely STRIPES, Kik-Piotrowski and Linder methods are implementedand compared in terms of contact patch prediction, as well as contact pressureand traction distributions. The paper also discusses the gaps to be filledin terms of contact model evaluation and the results indicate the need forbetter contact pressure and patch estimation in certain contact cases.

  • 150.
    Sh. Sichani, Matin
    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.
    Enblom, Roger
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    An approximate analytical method to solve frictionless contact between elastic bodies of revolutionManuscript (preprint) (Other academic)
    Abstract [en]

    An analytical method is proposed for calculating the contact patch and pressure distribution between two elastic bodies generated by rotating arbitrary profiles about parallel axes. The elastic deformation is approximated based on the separation between the bodies in contact. This makes it possible to estimate the contact patch analytically. The contact pressure distribution, in the direction perpendicular to the axes of rotation, is assumed to be elliptic with its maximum calculated by applying Hertz solution locally. The results are exact for contact between two ellipsoids when compared against Hertz's. In non-elliptic contact cases (e.g. in wheel-rail contact) good agreement is achieved in comparison to more accurate but computationally expensive methods such as Kalker's variational method (CONTACT algorithm). Compared to simplified non-elliptic contact methods based on virtual penetration, the calculated contact patch and pressure distribution are markedly improved. The computational cost of the proposed method is significantly lower than the more detailed methods, making it worthwhile to be applied to rolling contact in rail vehicle dynamic simulation.

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