(19)
(11)EP 3 131 803 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
20.11.2019 Bulletin 2019/47

(21)Application number: 15780435.2

(22)Date of filing:  07.04.2015
(51)International Patent Classification (IPC): 
B61K 9/08(2006.01)
G01M 5/00(2006.01)
E01B 35/12(2006.01)
(86)International application number:
PCT/SE2015/050414
(87)International publication number:
WO 2015/160300 (22.10.2015 Gazette  2015/42)

(54)

METHOD AND APPARATUS TO DETERMINE STRUCTURAL PARAMETERS OF A RAILWAY TRACK

VERFAHREN UND VORRICHTUNG ZUR BESTIMMUNG DER STRUKTURPARAMETER EINER EISENBAHNSCHIENE

PROCÉDÉ ET APPAREIL POUR DÉTERMINER DES PARAMÈTRES STRUCTURELS D'UNE VOIE DE CHEMIN DE FER


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 15.04.2014 SE 1450463

(43)Date of publication of application:
22.02.2017 Bulletin 2017/08

(73)Proprietor: Eber Dynamics AB
791 42 Falun (SE)

(72)Inventor:
  • BERGGREN, Eric
    791 42 Falun (SE)

(74)Representative: Brann AB 
P.O. Box 3690 Drottninggatan 27
103 59 Stockholm
103 59 Stockholm (SE)


(56)References cited: : 
WO-A1-2012/158091
US-A- 5 386 727
US-A- 6 119 353
US-A1- 2008 228 436
US-A1- 2012 245 908
US-A1- 2012 300 060
WO-A1-2012/158091
US-A- 5 753 808
US-A1- 2006 144 129
US-A1- 2012 245 908
US-A1- 2012 300 060
US-B1- 6 405 141
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to monitoring of railway tracks. By examining an implicitly measured deflection shape under a loaded axle, and comparing with a deflection shape from a model, structural parameter of the track can be determined.

    BACKGROUND



    [0002] A railway track has several properties that need to be monitored to ensure safe travel, some of them geometrical and some of them structural. Certainly there are links between structural and geometrical parameters. Track geometry quality is a set of parameters that describe current geometry of the track such as vertical and lateral irregularities/alignment (vertical alignment is often referred to as "surface" in the USA and "longitudinal level" in Europe), track gauge, cross level and curvature. In the remaining part of the text the term "geometrical parameter(s)" is used for vertical and lateral irregularities/alignment.

    [0003] Track geometry quality is measured with track recording cars, or by unattended systems fitted on ordinary cars. Measurement frequency can range from e.g. 1 - 20 times per year depending on safety regulations and maintenance management strategy.

    [0004] Examples of structural parameters are track stiffness/modulus (both vertical and lateral); clamping force of the fastener between sleeper and rail; stress free temperature of the rails and shear wave velocity of the soil. All these parameters influence the deflection shape of the rail under a given load.

    Industrial relevance and prior art of stress free temperature (SFT) and lateral stiffness/resistance



    [0005] Track buckling is formation of large lateral misalignments in railway track, sometimes resulting in train derailments. Buckles are typically caused by a combination of three major factors: high compressive forces, weakened track conditions, and vehicle loads (train dynamics).

    [0006] Compressive forces result from stresses induced in a constrained rail by temperatures above its "stress free" state, and from mechanical sources such as train braking and acceleration.

    [0007] The temperature of the rail at the stress-free state is known as the stress free temperature (SFT) (i.e. the temperature at which the rail experiences zero longitudinal force). Initially, the rail's installation temperature or anchoring temperature is the rail's SFT. Hence, at rail temperatures above the neutral, compressive forces are generated, and at temperatures below the neutral, tensile forces are developed. Track maintenance practices address the high thermal load problem by anchoring the rail at a (neutral) temperature of 10 - 40 °C depending on yearly average temperature. SFT may change over time due to for example track maintenance, geometrical track degradation and lateral track shift in curves.

    [0008] Weakened track conditions impacting the tracks buckling potential include: reduced track resistance, lateral alignment defects, and lowered rail SFT. Track resistance is the ability of the ballast, sleepers and fasteners to provide lateral and longitudinal strength to maintain track stability. Resistance is lowered if ballast is missing from under or between the sleepers, or from the ballast shoulder. A full ballast section is important, especially in curves. Track resistance is lowered when ballast is disturbed. Tamping (surfacing), sleeper renewal and undercutting operations will weaken ballast resistance to a great extent. Providing longitudinal resistance to the rail/sleeper structure by adequate rail anchoring is important to prevent rail running and hence the decrease of rail neutral temperature.

    [0009] To prevent track buckling, SFT and track resistance have to be monitored. Currently there exist a couple of methods to monitor SFT e. g.
    • Cut-method (The rail is cut and the gap is an estimate of SFT). This is a destructive method, a new weld is needed.
    • A method wherein fasteners are released and rail lifted. Lifting force is proportional to SFT


    [0010] Common to most of the prior art methods is that measurements are taken in one position at a time. This makes the methods time consuming and hence interval between measurements may be stretched (both in time and position along the track).

    [0011] SE534724C2 describes a continuous method to estimate SFT and track resistance from measurement of track geometry and rail temperature. Two sets of measurements are used from different occasions in order to have a temperature difference.

    [0012] The present invention is different in that only one measurement at one rail temperature is needed.

    [0013] US 5 386 727 describes an ultrasonic based method for determining the longitudinal stress in a rail section based on the alteration of an ultrasonic signal transmitted through said rail.

    Industrial relevance and prior art relating to fastener clamping force



    [0014] In ordered to keep a continuously welded rail in place at correct track gauge, the rails are clamped to the sleepers with a fastener system. Many fastener systems use an elastic clip which holds the rail with a certain force. Sometimes the clamping force may be reduced and the clip may even break. If consecutive clips are missing there may be a safety issue with train derailment as the worst scenario.

    [0015] One important property of the fastener is that it increases the rail bending stiffness.

    [0016] Missing clips are traditionally monitored by manual visual inspection. To date there exist a couple of automated systems based on cameras and image processing to find missing clips.

    Industrial relevance and prior art of wheel-rail contact force measurement



    [0017] Wheel-rail contact force measurements are used in various applications. Such measurements can be used to find discontinuities in the rail such as a sharp edge at a weld or at the crossing nose of a turnout. It is also often used in the homologation process of new railway vehicles in order to prove safe and comfortable ride and to restrict train-track interaction forces within certain limits.

    [0018] Wheel-rail contact forces can be measured with strain gauges mounted on the wheels. Also load cells and/or accelerometers mounted in the wheel-set or bogie can be used in different configurations.

    Industrial relevance and prior art of track stiffness and track bed modulus measurement



    [0019] Track stiffness and track bed modulus describe how much the track deflects at a given load. Track deflection needs to be within certain limits. Swift changes of track stiffness along the track can often explain maintenance problems.

    [0020] SE535848C2 describes a continuous method to determine track stiffness/deflection using track geometry quality parameters measured from a track recording car. Two different measurement systems for track geometry quality are used and by comparing them deflection can be found.

    [0021] US-6,119,353 describes a continuous method to determine track deflection using laser Doppler technique.

    [0022] US2006144129 discloses a noncontact measurement system for measuring the vertical stiffness of a railway track. The system comprises first and second optical emitters which are mounted to a measuring vehicle and configured to emit beams of light that are detectable on the underlying surface. A camera is mounted to the vehicle for recording the distance between the beams of light as the vehicle travels along the surface. The distance between the beams of light, which is a function of the surface stiffness, is then measured using image recognition US2012/0300060, in combination with US2009/0070064 and US2008/0228436, discloses a system to determine the rail modulus by using a camera/laser system attached to a railway vehicle travelling along the railway to measure the deformation of the rail induced by the wheel of the vehicle in order to determine the rail modulus.

    Industrial relevance and prior art of critical speed determination



    [0023] Under certain condition of soft soil and high travelling speed of trains (or airplanes take-off or landing on runways) a high-speed phenomenon can take place. When the speed approaches or exceeds the critical wave velocity for the compound track-ground structure, the track response dramatically changes characteristics. Propagating chock waves are generated by the moving load. This causes extensive vibration and large deflection of the ground. The short term solution is to restrict higher speed through affected areas. In order to resolve the problem, different methods to strengthen the soil can be used.

    [0024] Current methods to detect and quantify high-speed vibration phenomenon include e.g. geo-dynamic testing to determine the soil shear-wave velocity and stiffness/modulus as well as measurement of vibration when a high-speed train is passing. All current methods though, instrument the track and/or soil at a specific location and cannot be used on a running train to monitor larger distances.

    SUMMARY OF THE INVENTION



    [0025] As shown in the background section there exist a number of prior art methods for determining some of the structural parameters of railway tracks. However, these methods are either complex (e.g. require more than one measurement), destructive (e.g. requires a cut of the rail to determine rail stress state), time-consuming (non-continuous methods where only one position along the track is measured) or focused on only one parameter. All prior art methods determines only one structural parameter per method, or requires more than one measurement.

    [0026] In view of shortcomings of prior art methods relating to determination of structural parameters of railway tracks, the inventor has devised an improved method, by means of which a set of structural parameters is determined at the very same time.

    [0027] Thus, the present invention relates to the determination of a set of structural parameters of a railway track at the same time with only one passage over the railway track with a measurement vehicle.

    [0028] The invention is based on looking at and comparing the reaction of the track in terms of the rail deflection shape under influence of different loads. Loads are in all cases the train-track interaction load from the measurement vehicle wheel (s), and (if the structural parameter: rail-stress-state is considered), also temperature induced forces or loads in the rail-steel material). Comparison is done with the theoretical deflection shape of a model which is defined by the structural parameters. By varying the parameters of the model to best possible fit, structural parameters of the track are determined.

    [0029] The invention is defined by claim 1.

    [0030] A major advantage over prior art methods is that the present method is performed at one time only, i.e. it is not necessary to perform measurements at different times and/or temperatures.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0031] 

    Fig. 1 shows an example of system including a sensor array of laser/cameras fitted under a railway car body;

    Fig. 2 is an illustration of geometrical irregularities (vertical alignment) (dashed dotted line), deflection due to wheel load Q (solid line) and combination of the two (dashed line);

    Fig. 3 is an illustration of measured geometrical irregularities (vertical alignment) from four different sensors at different distance from the loaded wheel;

    Fig. 4 is an illustration of theoretical deflection shape and measured deflection shape at one position;

    Fig. 5 shows the longitudinal force resultant in vertical direction from geometrical irregularities, s(x) (dashed-dotted line), and deflection, w(x) due to a load in position 0 (solid line) at a temperature 30 °C above SFT; and

    Fig. 6 is a flow chart of the method according to the invention.


    DESCRIPTION OF THE INVENTION



    [0032] The invention relates to a method for determining structural parameters of a railway track comprising a sensor array configured to measure the deflection shape of the rail, which is under influence of one or several forces, together with geometrical irregularities. Preferably the sensors are mounted under the car body of a railway vehicle which makes continuous measurements along the rail possible. The deflection shape can also be created from a model where different parameters influence the deflection shape.

    [0033] The invention thus is in a first aspect a method for determining structural parameters of a rail track using a measurement system comprising a sensor array configured to measure at least the vertical and/or lateral irregularities of a rail under influence of different loads at a plurality of points along the rail, and at different distances from the wheel The sensor array also provides signals corresponding to said rail irregularities, the sensor array being positioned in a railway car being a measurement vehicle adjacent to the contact point between said wheel and said rail; and a processor configured to process the signals from the sensor array. The method further comprises measuring from the moving measurement vehicle at least the vertical and/or lateral irregularities of said rail with the sensor array along the rail, thereby providing signals corresponding to the geometrical irregularities at different distance from the wheel, i.e. under different load influence. A model is provided describing the deflection shape of a rail, wherein the deflection shape is dependent on structural parameters of the rail and on the loads on the rail, said model being stored in the processor. In the processor said geometrical irregularities are compared under different load influence in order to separate deflection due to the wheel load(s) from non-loaded geometrical irregularities, thus generating a measured deflection shape. At least one theoretical rail deflection shape is generated using the model by varying the structural parameters and the load in the model. At least one of said theoretical deflection shapes is compared with said measured deflection shape for each point of the rail, and the structural parameters of that theoretical deflection shape which best matches said measured deflection shape are determined.

    [0034] The loads are wheel loads and temperature induced longitudinal loads in the rail.

    [0035] The structural parameters that are determined are selected from track modulus, stress free temperature of the rails, bending moment of the rails, track damping, critical speed of the ground.

    [0036] The model describing the deflection shape of a rail, is preferably selected from linear or nonlinear beam model with foundation or linear or nonlinear FEM-model.

    [0037] In another aspect the invention provides an apparatus for determining structural parameters of a rail track having a measurement system comprising a sensor array configured to measure at least the vertical and/or lateral irregularities of a rail under influence of different loads at a plurality of points along the rail, and at different distances from the wheel, and to provide signals corresponding to said rail irregularities. The sensor array is positioned in a railway car adjacent to the contact point between said wheel and said rail; and a processor configured to process the signals from the sensor array. The processor being configured to perform the method according to any of claims 1- 8, by being setup to run a program. In a preferred embodiment the sensor array comprises sensors on both sides of the wheels in the longitudinal direction.

    [0038] A static model usable in the invention can include the following parameters:
    • Wheel-rail force
    • Rail bending stiffness with extra influence of fastener clip force (proportional to the 4th derivative of the deflection shape)
    • Temperature induced force of the rail, when the rail temperature differs from the SFT (proportional to the 2nd derivative of the deflection shape)
    • Track modulus (proportional to the deflection shape)


    [0039] A dynamic model usable in the invention can in addition include:
    • Vehicle speed
    • Inertial terms
    • Track and fastener damping (proportional to the 1st derivative of deflection by time)
    • Critical speed of the track


    [0040] By comparing the deflection shape measured by the sensors with the deflection shape calculated from the model, varying the parameters of the model to best possible fit, the structural parameters of the track can be determined.

    [0041] Other parameters can also be included in the model e.g. a more detailed model of track modulus to separate the pad stiffness of the fastener from ballast and substructure modulus.

    [0042] As different structural parameters are proportional to different orders of the deflection shape derivatives, the correlation between measured deflection shape and correlating model deflection shape will not be under-determined and thus solvable.

    [0043] The sensors could be of different kinds, point lasers, line-lasers with camera and optical triangulation, grid laser with camera and optical triangulation, laser-Doppler measuring velocity (which can be integrated to displacement), distance-radar etc.

    [0044] Sensors can be placed in boxes/fixtures where the relative motion of the fixtures compared to the rail are measured with accelerometers and gyros.

    [0045] One example of a measurement setup generally designated 10 is shown in Fig. 1 (direction of movement is the x direction). The setup comprises a sensor array 12 comprising a set-up of lasers and cameras arranged in front of a pair of wheels 14. The four vertical arrows 16 illustrate line lasers lighting a cross-section of the rail 18 and the broken lines 20 illustrate the camera view of the laser line. The sensor array 12 is coupled to a processor 22 configured to process signals from the sensors according to a program for determining structural parameters of the rail.

    [0046] In the figure, only one rail 18 is shown, but of course both rails can be monitored at the same time with two arrays of sensors.

    [0047] This described measurement setup is used to determine structural parameters originating from a static model (as described previously). As the deflection shape is symmetric around the wheel (or bogie) only one side of the wheel/bogie has to be monitored.

    [0048] A non-contact temperature sensor such as an infrared thermometer is used to measure the rail temperature. The sensor or thermometer can then be directed towards the rail web or foot. The temperature sensor (Trail) is used to relate determined stress state (Plong) of the rail to SFT (Tsft), with denotations from Eq.2.

    [0049] The main influencing forces creating a deflection shape, origin from the wheels. One minor influencing force taken into consideration by this invention is the vertical (z) and lateral (y) resultant coming from longitudinal (x) forces when the rail temperature differs from the SFT. This resultant force is proportional to the second derivative of the geometrical deviation with respect to x, the longitudinal elongation of the rail.

    [0050] One static model that can be used to describe the deflection shape is the Euler-Bernoulli beam on a Winkler foundation with the addition of longitudinal force from a rail temperature different from the SFT shown in Eq. 1.



    • w(x) denotes deflection shape (either vertical or lateral).
    • s(x) denotes vertical or lateral geometrical deviations. s(x) of equation 1, is considered as non-loaded geometry.
    • γ denotes increase of rail bending stiffness due to fasteners connecting the rail to the sleepers.
    • E is the rail-steel elastic modulus.
    • I is the area moment of inertia of the rail cross section (different in vertical and lateral direction).
    • Plong is the longitudinal force (temperature dependent stress state) of the rail apparent when the rail temperature, Trail, differs from the stress free temperature Tsfd (shown in Eq.2).
    • µ denotes the track modulus.
    • Q denotes wheel-rail force.
    • δ(x0) denotes the dirac-function making sure that Q is only acting at the wheel position x0.
    • α is the coefficient of heat expansion of rail steel.
    • A is the cross section area of the rail.


    [0051] E, I, A and α are considered as material constants although I and A will change slightly if the rail is worn.

    [0052] More advanced models can also be used using e.g. more advanced beam theory, finite elements, discrete supports of the rail with masses, springs and dampers at sleeper positions, vehicle speed, critical speed of the soil and an appropriate vehicle model to represent the wheel force to mention a few possible expansions.

    [0053] There exist closed form solutions for equation 1 if the unknown structural parameters γ, µ, and Plong are regarded as constants yielding a linear differential equation. Also Laplace/Fourier techniques can be used to solve the equation and compare/correlate with measured deflection.

    [0054] With varying unknown terms, Eq. 1 becomes non-linear and non-linear numerical solutions are needed.

    [0055] The displacement sensor array will measure a combination of the non-loaded geometrical irregularities (vertical and/or lateral alignment) and the structural deflection shape as is illustrated with circles in Fig. 2 for a measurement array with sensors at distances [0.5 1.5 2.5 3.5] meters from the wheel. The dashed-dotted line represents the unloaded vertical alignment, which are the geometrical irregularities of the rail before the train is coming. The dashed line represents the loaded vertical alignment when the wheel load is at position x = 6m. The solid line is the deflection shape due to the load at position x = 6m and naturally the difference between the unloaded and loaded vertical alignment.

    [0056] An illustration of readings from all four sensors is shown in Fig. 3. One specific position in the track, corresponding to the position of sensor 1 at x = 9.5m in Fig. 2, is illustrated for all four sensors with square (sensor 1), diamond (sensor 2), star (sensor 3) and circle (sensor 4). It is clear that the load influence from the wheel will increase as sensors are placed closer to the wheel. The readings from this position, forming a deflection shape measurement, is illustrated in Fig. 4 where also a theoretical deflection shape from the model in Eq. 1 is shown as a solid line. As a first try, all four sensor readings are adjusted so that sensor 1 has a zero-reading.

    [0057] As the measurement vehicle moves, each position along the track will have one measurement sample per sensor as illustrated in Figs. 3-4. Each position along the track will thus have measurements with different influence from the load. This is the basis for separating geometrical irregularities s(x) from deflection w(x).

    [0058] If the rail temperature differs from the SFT, longitudinal forces will be present in the rail. Both geometrical irregularities and deflection shape due to a wheel load will cause the longitudinal rail force to have vertical and lateral resultants. The resultants will be proportional to the second derivative of irregularities/deflection shape as shown in Eq. 1. Fig. 5 shows an example of resultant vertical forces with the basis from Fig. 2 and a rail temperature 30 °C above current SFT.

    [0059] Naturally these extra forces will cause minor extra deflection, which will make it possible to determine the structural parameter of the rail stress state and SFT.

    [0060] Another measurement setup could be used to determine critical speed of the track. When a train approaches critical speed, the deflection shape under a wheel or bogie will not be symmetric. In order to compare deflection shape before and after the wheel or bogie for critical speed determination, a similar sensor array is mounted on the other side of the wheel/bogie, thus making it possible to detect non-symmetric deflection shape when comparing deflection shape before and after the wheel. The actual speed of the measurement vehicle is measured at the same time to relate the non-symmetric deflection shape with critical speed. Structural parameters are in this case determined with the help of a dynamic model (as described above).

    [0061] One possible dynamic model is described by the differential equation (3)

    w(x,t) is now dependent of both position (x) and time (t). Variables, not already mention previously, are:
    • m: equivalent mass of the track per meter.
    • c: track damping
    • v: speed of vehicle


    [0062] Solving for critical speed with prior art will give the relation:



    [0063] A couple of passages at different speeds are often required in order to see increasing asymmetry in the deflection shape and from that determine unknown terms for Eq. 3 and 4.

    Calibration



    [0064] The geometrical irregularities measured with the sensor array will differ from time to time for various reasons. The wheel-rail contact position will vary and cause small variation of height between the car body where sensors are mounted and the rail. The suspension system of wheel and bogie of the car will also cause variations in height. To some extent, an inertial measurement platform close to the sensor array with accelerometers and gyros can compensate for this. An accurate calibration is important where it is ascertained that the whole sensor array has the same height reference. This can e.g. be done with a steel rural with defined straightness combined with an accurate inclinometer.

    [0065] Remaining variations can be included as an error state in the numerical solution.

    Numerical solution/implementation of the invention



    [0066] There exists a range of methods to make parameter adjustments of a model in order to fit the model to measurements and in that way estimate the parameters. One such method is the Kalman filter which exists in several different variants depending on model complexity and linearity/non-linearity. Examples of other methods are the family of adaptive filters and sequential Monte Carlo methods.

    [0067] A Kalman filter works on discrete data. The standard denotation of a Kalman-filter state is x. In the following n denotes discretization of the position along the track and x denotes the Kalman filter state.

    [0068] A Kalman filter that determines the structural parameters of Eq. 1-2 is described in Eq. 5-14. The basic equation (Eq. 5) describes the position-update (x(n+1)) solving for next position along the track and the measurement update (y(n)). In this implementation, the position update is linear with the transfer matrix F, and process noise v(n). The measurement update is non-linear for some states and linear for others. This is described with the non-linear function h() which is dependent on the filter states x(n) and the measurement noise e(n). Underline denotes a vector and a line above the symbol denotes a matrix.



    [0069] The covariance of v(n) is denoted Qcov(n) and the covariance of e(n) is denoted Rcov(n). The state vector x(n) contains the following states:



    [0070] The vectors W(n) and S(n) contain necessary derivatives at samples spanning the whole distance of the sensor array according to:





    [0071] Searched parameter vectors Tsft, µ, γ, Q also span the interval between n and n-m., as showed for modulus µ in Eq. 9.



    [0072] In one example of the invention n is the position at 3.5 m to the right of the wheel, at the first sensor position, and n-m is the position at 0.5 m to the right of the wheel at the fourth (last) sensor. These four sensor positions are indicated in Fig. 1 and 2. If the sampling frequency fs is 10 samples per meter, Δn = 0.1 m, the number of states x, will be 279 (W- 93 states, S - 62 states, Tsft - 31 states, µ - 31 states, γ - 31 states, Q - 31 states).

    [0073] The position update matrix F will consist of a number of sub-matrixes shown in Eq. 10.



    [0074] Fw and FY will be built on the symmetrical numerical double derivative:



    [0075] Taking the position update (from x(n) to x(n+1)) and expanding the derivatives leads to:

    and

    which fill basis for FW and FS.

    [0076] The remaining sub-matrixes of F, can be unity matrixes as an adequate position-update is the last estimate.

    [0077] The measurement update includes both linear and non-linear updates. The linear measurement update is naturally measurements from the sensors as in Equation 14. With Δn = 0.1 m, 10 samples shift corresponds to one meter, and as seen from the equation, sensors are placed at one meters distance from each other in this example.



    [0078] As can be seen from the equation and also from Figs. 2-4, sensor measurements are a combination of deflection (w(n)) and geometrical irregularities (s(n)) together with a measurement error (e(n)).

    [0079] Measurements of the wheel force can easily be incorporated as a measurement update if sensors for measuring wheel force are available.

    [0080] Finally, the non-linear measurement updates tie the model from Eq. 1 with estimated values of deflection and geometrical irregularities. This can be executed for each position spanned by the sensor array, or in order to reduce calculation complexity, only at the positions of the sensors as outlined in Eq. 15.



    [0081] The measurement updates y5(n) - y8(n) are formed to equal to zero.

    [0082] To have the wheel-force influencing the measurement equation directly, a closed form solution of Eq. 1 could be implemented as a measurement update. Another alternative is to extend the equations with states to include also the wheel position.

    [0083] The non-linear measurement update is implemented with for example an extended Kalman filter or an unscented Kalman filter.

    [0084] From an initial estimate, the Kalman filter improves the estimate as position-updates and measurement updates progress. Normally some 10-20 meters are needed to separate deflection from geometrical irregularities and to give adequate determination of structural parameters.


    Claims

    1. A method for determining structural parameters of a rail track using a measurement system (10) comprising a sensor array (12) configured to measure at least the vertical and/or lateral irregularities of a rail (18) under influence of different loads at a plurality of points along the rail, and at different distances from a wheel (14), and to provide signals corresponding to said rail irregularities, the sensor array and the wheel being positioned in a railway car being a measurement vehicle adjacent to the contact point between said wheel (14) and said rail (18); and a processor configured to process the signals from the sensor array; the method comprising

    measuring from the moving measurement vehicle at least the vertical and/or lateral irregularities of said rail with the sensor array along the rail, thereby providing signals corresponding to the geometrical irregularities at different distance from said wheel, i.e. under different load influence;

    providing a model describing the deflection shape of a rail, wherein the deflection shape is dependent on structural parameters of the rail and on the loads on the rail, said model being stored in the processor; and

    characterized by, in the processor

    comparing said geometrical irregularities under different load influence in order to separate deflection due to the wheel load(s) from non-loaded geometrical irregularities, thus generating a measured deflection shape;

    generating at least one theoretical rail deflection shape using the model by varying the structural parameters and the load in the model;

    comparing at least one of said theoretical deflection shapes with said measured deflection shape for each point of the rail; and

    determining the structural parameters of that theoretical deflection shape which best matches said measured deflection shape.


     
    2. The method according to claim 1, wherein the loads are wheel loads and temperature induced longitudinal loads in the rail.
     
    3. The method according to claim 1 or 2 wherein structural parameters are selected from track modulus, stress free temperature of the rail, bending moment of the rail, track damping, critical speed of the ground.
     
    4. The method according to any preceding claim, wherein the sensor array for measuring said irregularities comprises any of lasers, laser and camera, laser-doppler for velocity, radar.
     
    5. The method according to any preceding claim, wherein the model describing the deflection shape of a rail, is selected from linear or nonlinear beam model with foundation or linear or nonlinear FEM-model.
     
    6. The method according to any preceding claim, wherein the step of comparing the least one of said theoretical deflection shapes includes use of any of Kalman filters, adaptive filters or sequential Monte Carlo methods.
     
    7. The method according to any preceding claim, wherein in order to compare deflection shape before and after the wheel or a bogie for critical speed determination, a similar sensor array is mounted on the other side of the wheel/bogie in the longitudinal direction, and measuring said irregularities thus making it possible to detect non-symmetric deflection shape when comparing deflection shape before and after the wheel.
     
    8. The method according to claim 1 and 3, where the structural parameter stress state is related to stress free temperature by measuring the rail temperature with a thermometer and comparing with a stress free state in accordance with the equation: Plong = α EA(Trail - Tsft), with Plong being the longitudinal force of the rail appearing when the rail temperature (Trail) differs from the stress free temperature (Tsft), E being the rail elastic modulus, A the rail cross section and α the heat expansion coefficient of the rail.
     
    9. An apparatus for determining structural parameters of a rail track (18) having a measurement system (10) comprising a sensor array (12) configured to measure at least the vertical and/or lateral irregularities of a rail under influence of different loads at a plurality of points along the rail (18), and at different distances from the wheel (14), and to provide signals corresponding to said rail irregularities, the sensor array (12) being positioned in a railway car adjacent to the contact point between said wheel and said rail; and a processor (22) configured to process the signals from the sensor array (12), the processor (22) being configured to perform the method according to any of claims 1- 8.
     
    10. The apparatus according to claim 9, wherein the sensor array comprises sensors on both sides of the wheel in the longitudinal direction.
     
    11. The apparatus according to claim 9 or 10, further comprising a thermometer for measuring the rail temperature.
     


    Ansprüche

    1. Verfahren zum Bestimmen von Strukturparametern eines Schienenwegs, das ein Messsystem (10) verwendet, das ein Sensor-Array (12) umfasst, das konfiguriert ist, um mindestens die vertikalen und/oder seitlichen Unregelmäßigkeiten einer Schiene (18) unter Einfluss unterschiedlicher Lasten an einer Vielzahl von Stellen entlang der Schiene und an unterschiedlichen Abständen von einem Rad (14) zu messen, und um Signale, die den Schienenunregelmäßigkeiten entsprechen, bereitzustellen, wobei das Sensor-Array und das Rad in einem Waggon, der ein Messfahrzeug benachbart zu der Berührungsstelle zwischen dem Rad (14) und der Schiene (18) ist, positioniert ist; und einen Prozessor, der konfiguriert ist, um die Signale von dem Sensor-Array zu verarbeiten;
    wobei das Verfahren das Messen von dem Messfahrzeug in Bewegung mindestens der vertikalen und/oder seitlichen Unregelmäßigkeiten der Schiene mit dem Sensor-Array entlang der Schiene umfasst, wodurch Signale bereitgestellt werden, die den geometrischen Unregelmäßigkeiten an einem unterschiedlichen Abstand von dem Rad entsprechen, das heißt unter unterschiedlichem Lasteinfluss;
    das Bereitstellen eines Modells, das die Biegungsform einer Schiene bereitstellt, wobei die Biegungsform von Strukturparametern der Schiene und von den Lasten auf der Schiene abhängt, wobei das Modell in dem Prozessor gespeichert ist; und
    gekennzeichnet durch
    das Vergleichen in dem Prozessor der geometrischen Unregelmäßigkeiten unter unterschiedlichem Lasteinfluss, um Biegung aufgrund der Radlast(en) von unbelasteten geometrischen Unregelmäßigkeiten zu unterscheiden, so dass eine gemessene Biegungsform erzeugt wird;
    das Erzeugen mindestens einer theoretischen Schienenbiegungsform unter Verwenden des Modells durch Variieren der Strukturparameter und der Last in dem Modell;
    das Vergleichen mindestens einer der theoretischen Biegungsformen mit der gemessenen Biegungsform für jede Stelle der Schiene; und
    das Bestimmen der Strukturparameter derjenigen theoretischen Biegungsform, die der gemessenen Biegungsform am besten entspricht.
     
    2. Verfahren nach Anspruch 1, wobei die Lasten Radlasten und durch Temperatur induzierte Längslasten in der Schiene sind.
     
    3. Verfahren nach Anspruch 1 oder 2, wobei die Strukturparameter aus Gleismodul, beanspruchungsfreier Temperatur der Schiene, Biegemoment der Schiene, Wegdämpfen, kritischer Geschwindigkeit des Grunds ausgewählt werden.
     
    4. Verfahren nach einem der vorstehenden Ansprüche, wobei das Sensor-Array zum Messen der Unregelmäßigkeiten Laser, Laser und Kamera, Laser-Doppler für Geschwindigkeit, Radar umfasst.
     
    5. Verfahren nach einem der vorstehenden Ansprüche, wobei das Modell, das die Biegungsform einer Schiene beschreibt, aus einem linearen oder nichtlinearen Modell mit Fundamentträger oder linearen oder nichtlinearen FEM-Modell ausgewählt wird.
     
    6. Verfahren nach einem der vorstehenden Ansprüche, wobei der Schritt des Vergleichens der mindestens einen der theoretischen Biegungsformen das Verwenden von Kalman-Filtern, adaptiven Filtern oder sequenziellen Monte-Carlo-Verfahren einschließt.
     
    7. Verfahren nach einem der vorstehenden Ansprüche, wobei zum Vergleichen der Biegeform vor und nach dem Rad oder eines Drehgestells für Bestimmung der kritischen Geschwindigkeit ein ähnliches Sensor-Array auf die andere Seite des Rads/Drehgestells in die Längsrichtung montiert wird, und Unregelmäßigkeiten gemessen werden, so dass es möglich ist, unsymmetrische Biegungsform zu erfassen, wenn die Biegungsform vor und nach dem Rad verglichen wird.
     
    8. Verfahren nach Anspruch 1 und 3, wobei der Strukturparameterbeanspruchungszustand mit beanspruchungsfreier Temperatur zusammenhängt, durch Messen der Schienentemperatur mit einem Thermometer und Vergleichen mit einem beanspruchungsfreien Zustand in Übereinstimmung mit der Gleichung Plong = α EA(Trail-Tsft), wobei Plong die Längskraft der Schiene ist, die erscheint, wenn die Schienentemperatur (Trail) von der beanspruchungsfreien Temperatur (Tsft) unterschiedlich ist, E das Elastizitätsmodul der Schiene ist, A der Schienenquerschnitt ist und α der Wärmeausdehnungskoeffizient der Schiene ist.
     
    9. Einrichtung zum Bestimmen von Strukturparametern eines Schienenwegs (18), das ein Messsystem (10) aufweist, das ein Sensor-Array (12) umfasst, das konfiguriert ist, um mindestens die vertikalen und/oder seitlichen Unregelmäßigkeiten einer Schiene unter Einfluss unterschiedlicher Lasten an einer Vielzahl von Stellen entlang der Schiene (18) und an unterschiedlichen Abständen von dem Rad (14) zu messen, und Signale bereitzustellen, die den Schienenunregelmäßigkeiten entsprechen, wobei das Sensor-Array (12) in einem Waggon benachbart zu der Berührungsstelle zwischen dem Rad und der Schiene positioniert ist; und
    einen Prozessor (22), der konfiguriert ist, um die Signale von dem Sensor-Array (12) zu verarbeiten, wobei der Prozessor (22) konfiguriert ist, um das Verfahren nach einem der Ansprüche 1-8 auszuführen.
     
    10. Einrichtung nach Anspruch 9, wobei das Sensor-Array Sensoren auf beiden Seiten des Rads in die Längsrichtung umfasst.
     
    11. Einrichtung nach Anspruch 9 oder 10, das weiter ein Thermometer zum Messen der Schienentemperatur umfasst.
     


    Revendications

    1. Procédé de détermination de paramètres structurels d'une voie de chemin de fer en utilisant un système de mesure (10) comprenant un groupement de capteurs (12) configuré pour mesurer au moins les irrégularités verticales et/ou latérales d'un rail (18) sous l'influence de différentes charges au niveau d'une pluralité de points le long du rail, et à différentes distances d'une roue (14), et pour fournir des signaux correspondant auxdites irrégularités de rail, le groupement de capteurs et la roue étant positionnés dans un wagon de chemin de fer qui est un véhicule de mesure adjacent au point de contact entre ladite roue (14) et ledit rail (18) ; et un processeur configuré pour traiter les signaux du groupement de capteurs ; le procédé comprenant
    la mesure à partir du véhicule de mesure mobile d'au moins les irrégularités verticales et/ou latérales dudit rail avec le groupement de capteurs le long du rail, fournissant ainsi des signaux correspondant aux irrégularités géométriques à une distance différente de ladite roue, c'est-à-dire sous l'influence de charge différente ;
    la fourniture d'un modèle décrivant la forme de déflexion d'un rail, dans lequel la forme de déflexion est dépendante de paramètres structurels du rail et des charges sur le rail, ledit modèle étant stocké dans le processeur ; et
    caractérisé par, dans le processeur
    la comparaison desdites irrégularités géométriques sous l'influence de charge différente afin de séparer la déflexion en raison de la/des charge(s) de roue des irrégularités géométriques non chargées, générant ainsi une forme de déflexion mesurée ;
    la génération d'au moins une forme de déflexion de rail théorique en utilisant le modèle par variation des paramètres structurels et de la charge dans le modèle ;
    la comparaison d'au moins une desdites formes de déflexion théoriques avec ladite forme de déflexion mesurée pour chaque point du rail ; et
    la détermination des paramètres structurels de cette forme de déflexion théorique qui correspond le mieux à ladite forme de déflexion mesurée.
     
    2. Procédé selon la revendication 1, dans lequel les charges sont des charges de roue et des charges longitudinales induites par la température dans le rail.
     
    3. Procédé selon la revendication 1 ou 2, dans lequel des paramètres structurels sont sélectionnés à partir du module de voie, de la température exempte de contrainte du rail, du couple de flexion du rail, de l'amortissement de voie, de la vitesse critique du sol.
     
    4. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'groupement de capteurs pour la mesure desdites irrégularités comprend l'un quelconque parmi le laser, le laser et la caméra, le doppler laser pour la vitesse, le radar.
     
    5. Procédé selon l'une quelconque des revendications précédentes, dans lequel le modèle décrivant la forme de déflexion d'un rail, est sélectionné à partir du modèle de faisceau linéaire ou non linéaire avec fondation ou modèle FEM linéaire ou non linéaire.
     
    6. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de comparaison de l'au moins une desdites formes de déflexion théoriques inclut l'utilisation de n'importe lequel parmi les filtres Kalman, les filtres adaptatifs ou les procédés Monte Carlo séquentiels.
     
    7. Procédé selon l'une quelconque des revendications précédentes, dans lequel afin de comparer la forme de déflexion avant et après la roue ou un bogie pour la détermination de vitesse critique, un groupement de capteurs similaire est monté sur l'autre côté de la roue/du bogie dans la direction longitudinale, et la mesure desdites irrégularités permettant ainsi de détecter une forme de déflexion non symétrique lors de la comparaison de la forme de déflexion avant et après la roue.
     
    8. Procédé selon les revendications 1 et 3, dans lequel l'état de contrainte de paramètre structurel est lié à la température exempte de contrainte par la mesure de la température de rail avec un thermomètre et la comparaison avec un état exempt de contrainte selon l'équation : Plong = α EA(Trail - Tsft), avec Plong étant la force longitudinale du rail apparaissant lorsque la température de rail (Irail) diffère de la température exempte de contrainte (Tsft), E étant le module élastique de rail, A la section transversale de rail et α le coefficient de dilatation thermique du rail.
     
    9. Appareil pour déterminer des paramètres structurels d'une voie de chemin de fer (18) présentant un système de mesure (10) comprenant un groupement de capteurs (12) configuré pour mesurer au moins les irrégularités verticales et/ou latérales d'un rail sous l'influence de différentes charges au niveau d'une pluralité de points le long du rail (18), et à différentes distances de la roue (14), et pour fournir des signaux correspondants auxdites irrégularités de rail, le groupement de capteurs (12) étant positionné dans un wagon de chemin de fer adjacent au point de contact entre ladite roue et ledit rail ; et un processeur (22) configuré pour traiter les signaux du groupement de capteurs (12), le processeur (22) étant configuré pour réaliser le procédé selon l'une quelconque des revendications 1 à 8.
     
    10. Appareil selon la revendication 9, dans lequel l'groupement de capteurs comprend des capteurs sur les deux côtés de la roue dans la direction longitudinale.
     
    11. Appareil selon la revendication 9 ou 10, comprenant en outre un thermomètre pour la mesure de la température du rail.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description