METHOD FOR DETERMINING AT LEAST ONE GEOMETRY PARAMETER OF A RAILWAY TRACK AND SYSTEM FOR EXECUTING THE METHOD

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The invention relates to the determination of certain parameters of the geometry of a railway track, in particular with a view to its inspection or control, for example during its installation, monitoring, maintenance or repair. ETAT DE LA TECHNIQUE ANTERIEURE

[0002] The main parameters of track geometry defined in standard EN 13848 are: the gauge: smallest distance between the rails up to 14mm below the running surface; longitudinal leveling: variation of the successive altitudes of the running surface in relation to a reference altitude which is a sliding average; the cant: difference in altitude between the running surfaces of the left and right rails; the dressing: variation of the positions in the horizontal plane of the position of each rail wire in relation to a reference position which is a sliding average; the left: variation of the cant.

[0003] Longitudinal leveling, straightening and left measurements are variation measurements. These are referred to as relative measurements in opposition to the cant and the spacing, which are absolute measurements. According to the standard, longitudinal leveling and straightening are studied in different wavelength ranges: D1: 3m to 25m D2: 25m to 70m D3: 70m to 150m

[0004] To determine the geometry of a railway track, it is known to run an instrumented vehicle on the track, the body or bogie chassis of which is equipped with an inertial unit providing gyroscopic measurements of yaw, pitch and roll angles and accelerometric measurements along three axes. The vehicle is also equipped with detection lasers to determine the relative position of the chassis, and therefore of the inertial unit, in relation to the lines of rails of the railway.

[0005] Such a non-contact inertial measurement device is notably implemented in the IRIS 320 high-speed measuring train (TGV d'Inspection Rapide des Installations de Sécurité at 320 km / h), which allows measurement of all track geometry parameters up to a running speed on the train track of 360 km / h.

[0006] A disadvantage of this device is that it imposes a minimum speed of movement of the measuring vehicle on the track. At low speeds, the accelerometric signals which, by double temporal integration, allow access to displacements in the three dimensions of space, are weak and do not exploit the full dynamics of the sensors. It follows that the accelerometric measurements are potentially affected by inaccuracies or systematic biases, which are amplified by the double integration operations, to the point of generating a constant temporal drift in the estimation of displacements in the three dimensions. In practice, we observe that these drifts are no longer negligible below a certain speed of circulation, which in practice can be 60 km / h, so that it is not possible to obtain measurements for slow walking or with stops.The scope of application of measuring vehicles equipped with such a conventional inertial measurement system is therefore limited. In particular, they cannot be used on a railway repair site, which progresses at a working speed well below the minimum operating speed of the measuring device and which may have zero speed during stops of arbitrarily long duration.

[0007] In the document José L. Escalona: "A methodology for the measurement of track geometry based on computer vision and inertial sensors", ARXIV.ORG, CORNELL UNIVERSITY LIBRARY, 201 OLIN LIBRARY CORNELL UNIVERSITY ITHACA, NY 14853, August 9, 2020, XP081737359, a method according to the preamble of claim 1 is described. DISCLOSURE OF THE INVENTION

[0008] The invention aims to remedy the drawbacks of the state of the art and to propose means for determining, with the precision desired in practice, the geometry of a railway track, which can be implemented at low running speed on the track including arbitrarily long stops.

[0009] To do this, according to a first aspect of the invention, a method is proposed for determining at least one geometric parameter of a railway track with two lines of rails, in which: a vehicle carrying an inertial unit, equipment for measuring at least one relative orientation component of at least one of the two lines of rails with respect to the inertial unit, and one or more odometers is rolled on the railway track, successive values ​​of at least one absolute orientation component of the inertial unit in a geostationary reference frame are determined, based on at least signals delivered by the inertial unit, for at least one line of rails observed among the two lines of rails, and preferably for each of the two lines of rails taken as the observed line of rails, successive values ​​of the curvilinear abscissa of the vehicle on the observed line of rails are determined, based on at least signals delivered by the odometer(s),successive values ​​of at least one relative orientation component of the row of rails observed with respect to the inertial unit, we calculate, as a function at least of the successive values ​​of the absolute orientation component of the inertial unit and of the successive values ​​of the relative orientation component of the row of rails observed with respect to the inertial unit, successive values ​​of at least one absolute orientation or absolute positioning component of the row of rails observed, we construct a function s → , G (s) linking at least some of the successive values ​​of curvilinear abscissa to concomitant values ​​among the successive values ​​of the absolute orientation or absolute positioning component of the line of rails observed in space, a high-pass or band-pass linear filter is applied to the function s → G (s), so as to construct a filtered function s → F (s),we estimate, for a succession of current values ​​of curvilinear abscissa l among the curvilinear abscissa values, an integral I(l), on a given interval of curvilinear abscissas bounded by a reference curvilinear abscissa value l 0 and by the current value of curvilinear abscissa l , of the filtered function I l = ∫ s = l o s = l F s ds

[0010] By carrying out, for each row of rails observed, a single spatial integration rather than a double temporal integration of a filtered function linking the curvilinear abscissa of the vehicle on the row of rails observed to a component of absolute orientation or absolute positioning, we eliminate all time-related effects and in particular drift effects.

[0011] In practice, the successive values ​​of the curvilinear abscissa are not necessarily determined at a constant distance interval. The different signals can in particular be sampled at a constant time interval, preferably in a synchronized manner so as to obtain good concomitance between the values ​​determined from the signals of the inertial unit, the odometer(s) and the measuring equipment.

[0012] The inertial unit implemented must be of a level of precision that effectively allows access to absolute orientation components in a geostationary frame of reference, i.e. without drift. It is therefore a type of unit whose gyroscopes are able to detect the projection of the rotation of the Earth and whose accelerometers are able to detect the projection of gravity.

[0013] By applying the band-pass or high-pass filter to the input function s → G( s ) before the integration operation, potential numerical instabilities that would result from an integration of the continuous component of the input function are avoided. The linear filter implemented is preferably a finite impulse response filter of any order N, preferably greater than or equal to 2.

[0014] Preferably, the linear filter is a bandpass filter, preferably in one of the following three bands: 3m to 25m, 25m to 70m, 70m to 150m, or a deflection calculation function. In practice, one can naturally construct from the same function s → G (s) several filter functions in parallel, each for a wavelength band or filter type.

[0015] In practice, the estimate of the integral is obtained by a discrete sum, preferably the integral I(l)is estimated by a Riemann sum or by the trapezoid method on the given interval, with a step less than 25cm, and preferably less than 1cm.

[0016] According to one embodiment, the operation of calculating the successive values ​​of at least one absolute orientation or positioning component of the observed line of rails consists, at successive times, of an algebraic sum of an instantaneous value of the absolute orientation component of the inertial unit and of a simultaneous instantaneous value of the relative orientation component of each of the observed line of rails with respect to the inertial unit.

[0017] According to one embodiment, the relative orientation component of the line of rails observed with respect to the inertial unit is an orientation angle in a horizontal plane, and the absolute orientation component of the inertial unit is a yaw angle, the integral I(l) being a dressing parameter. If we note ψ R the instantaneous value of the angle determined by the measuring equipment in the horizontal plane between the longitudinal direction of the inertial unit and the direction of the observed rail line, and ψ C the instantaneous value of the yaw angle determined simultaneously by the inertial unit, the absolute orientation component ψ A of the observed line of rails can be expressed as the algebraic sum: ψ A = ψ R + ψ C

[0018] According to another embodiment, the relative orientation component of the line of rails observed with respect to the inertial unit is an orientation angle with respect to a longitudinal vertical plane (V) of the vehicle, and the absolute orientation component of the inertial unit is a pitch angle, the integral I(l) being a longitudinal leveling parameter. If we note i R the instantaneous value of the angle determined by the measuring equipment in the longitudinal vertical plane between the longitudinal direction of the inertial unit and the direction of the observed rail line, and i C the instantaneous value of the pitch angle determined simultaneously by the inertial unit, the absolute orientation component of the line of rails can be expressed as the algebraic sum: θ A = θ R + θ C

[0019] Preferably, the operations of calculating the successive values ​​of at least one absolute orientation component of a row of rails observed among the two rows of rails, of constructing the function s → G ( s ), application of a linear filter, construction of the filtered function s → F ( s ) and estimation of the integral I(l) are performed in parallel to obtain the intrinsic dressing coordinate and the intrinsic longitudinal leveling coordinate.

[0020] According to one embodiment, it is provided that for each row of rails observed, the measuring equipment delivers at least two simultaneous signals for measuring the lateral distance between two reference points of the vehicle and the row of rails observed, the two reference points being at a distance (A) from each other greater than 250 mm, and preferably greater than 500 mm. If A is the distance between the two reference points targeting the same row of rails observed, y 1 and y 2 the lateral distances measured between the observed line of rails and each reference point and assuming that when y 1 = y 2, the longitudinal axis of the inertial unit is aligned with the longitudinal axis of the rail line, the measuring equipment allows access to the relative orientation component constituted by the yaw angle ψ R of the inertial unit relative to the observed line of rails, by the equation: ψ R = arctan y 1 − y 2 A

[0021] According to one embodiment, it is provided that for each row of rails observed, the measuring equipment delivers at least two simultaneous signals for measuring the vertical distance between two reference points of the vehicle and the row of rails observed, the two reference points being at a distance (B) from each other greater than 250 mm, and preferably greater than 500 mm. If B is the distance between the two reference points targeting the same row of rails observed, z 1 and z 2 the vertical distances measured between the observed line of rails and each reference point and assuming that when z 1 = z 2, the longitudinal axis of the inertial unit is aligned with the longitudinal axis of the rail line, the measuring equipment allows access to the relative orientation component constituted by the yaw angle iR of the inertial unit relative to the observed line of rails, by the equation: θ R = arctan z 1 − z 2 B

[0022] The sensors of the measuring equipment can operate according to different principles (optical, magnetic, capacitive, etc.), which operate linearly and optimally within a relatively narrow operating range. It is therefore important that the positioning of the vehicle on the railway, both vertically and laterally, is close to an "ideal" alignment position at all times.For this purpose, it may be provided that at least one actuator for correcting the registration of the vehicle on the railway track is controlled as a function of the signals delivered by the measuring equipment or of the successive values ​​of the relative orientation component of the row of rails observed with respect to the inertial unit to reduce a difference between the signals delivered by the measuring equipment and predetermined values, or to reduce a difference between the successive values ​​of the relative orientation component of the row of rails observed and a predetermined value of the relative orientation component of the row of rails observed. The correction operation will be particularly useful for a vehicle running on a single pair of wheels.

[0023] According to one embodiment, the operation of determining the successive values ​​of the curvilinear abscissa of the vehicle on the observed line of rails is carried out as a function of at least signals delivered by an odometer associated with the observed line of rails among the odometer(s). In the case where each of the lines of rails is associated with at least one odometer, this operation may be carried out for each of the lines of rails.

[0024] According to one embodiment, the operation of determining the successive values ​​of the curvilinear abscissa of the vehicle on the observed line of rails is carried out as a function of at least signals delivered by an odometer which is not associated with the observed line of rail among the odometer(s) and signals delivered by the measuring equipment. In the case where only one of the lines of rails is associated with an odometer, this operation may be carried out for the other line of track.

[0025] In practice, the wheels to which the odometer(s) are linked may temporarily lose contact with the observed line of rails, in which case the signals delivered no longer provide reliable information on the positioning of the vehicle relative to the observed line of rails. According to one embodiment, failures of the odometer(s) are detected by comparing longitudinal acceleration values ​​delivered by the inertial unit with average acceleration values ​​determined as a function of the signals delivered by the odometer(s) and / or by comparing angular velocity values ​​around a vertical axis delivered by the inertial unit with angular velocity values ​​deduced from the signals delivered by the odometer(s).Preferably, it is provided that when a failure is detected, a safety procedure is executed, in which the successive values ​​of curvilinear abscissa of the vehicle on each of the two lines of rails are determined as a function of at least accelerometric signals or angular velocity delivered by the inertial unit.

[0026] According to another aspect of the invention, it relates to a system for implementing the method according to the first aspect of the invention, or one of its embodiments, comprising a vehicle capable of running on a railway track with two parallel lines of rails, the vehicle carrying an inertial unit with at least three gyrometers and three accelerometers, equipment for measuring a relative orientation of each of the two lines of rails with respect to the inertial unit, and one or more odometers, characterized in that the system further comprises calculation means programmed to execute the operations of calculating the successive values ​​of at least one absolute orientation or positioning component of a line of rails observed among the two lines of rails, of constructing the function s → G ( s ), application of a linear filter, construction of the filtered function s → F ( s) and estimation of the integral I(l).

[0027] According to one embodiment, the measuring equipment comprises, associated with each of the two rows of rails, at least two sensors for measuring the lateral distance between two reference points of the vehicle and the associated row of rails, the two reference points being at a distance (A) from each other greater than 250 mm, and preferably greater than 500 mm. Each of the sensors is here dedicated to measuring a lateral distance at one of the reference points.

[0028] According to one embodiment, the measuring equipment comprises, associated with each of the two rows of rails, at least two sensors for measuring the vertical distance between two reference points of the vehicle and the associated row of rails, the two reference points being at a distance (B) from each other greater than 250 mm, and preferably greater than 500 mm. Each of the sensors is here dedicated to measuring a vertical distance at one of the reference points.

[0029] Other principles for measuring the relative orientation of the inertial unit with respect to each of the rows of rails are envisaged. According to one embodiment, the measuring equipment comprises at least one and preferably at least two cameras for detecting one or more linear laser beams projected onto each of the rows of rails. For example, each camera can capture the position of a laser line projected onto the row of rails observed, the measuring equipment determining by triangulation the relative vertical and lateral position between the row of rails observed and the camera, placed in the reference frame of the inertial unit.

[0030] According to another embodiment, the measuring equipment comprises at least one and preferably at least two laser rangefinders scanning the lines of rails of the railway. According to the principle of laser rangefinders, the distance is given by measuring the delay between the emission of a pulse and the detection of a reflected pulse. The projected laser beam is oriented by a rotating mirror, which makes it possible to scan a plane of space which can cover the two lines of rails and to deduce therefrom by triangulation for each line of rails a lateral distance measurement and a vertical distance measurement. With two laser rangefinders placed at a distance from each other in the longitudinal direction of the vehicle, it is thus possible to obtain the eight desired dimensions, namely four lateral distances and four vertical distances.

[0031] Where appropriate, the measuring equipment may also include a track gauge sensor, although this dimension may be derived from the lateral distance measurements between the various reference points and the two lines of rail. Where appropriate, the measuring equipment may also include a track cant sensor.

[0032] According to one embodiment, the vehicle is a two-wheeled cart, driven by a machine and connected to the machine via at least three links making it possible to control the attitude and the registration of the cart according to the relative orientation components.

[0033] According to an alternative embodiment, the vehicle is a cart with at least four wheels. BRIEF DESCRIPTION OF THE FIGURES

[0034] Other characteristics and advantages of the invention will emerge from reading the description which follows, with reference to the appended figures, which illustrate: there figure 1 , a schematic side view of a system for determining geometric parameters of a railway track according to an embodiment of the invention; the figure 2 , a schematic top view of the system of the figure 1 ; there figure 3 , a schematic view of distance sensors integrated into a measuring equipment of the system of the figure 1 ; There figure 4 , a visualization diagram of a method for determining the geometric parameter of a railway track according to an embodiment of the invention; The figure 5 , a visualization diagram of a filtering operation of the process of the figure 4 .

[0035] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DESCRIPTION DÉTAILLÉE DE MODES DE REALIZATION

[0036] On the figures 1 and 2A system 10 is illustrated for determining at least one geometric parameter of a railway track 1 with two lines of rails 2, comprising a vehicle 12 capable of running on the railway track, coupled to a railway machine 14, which may in particular be a machine for laying, repairing or renewing the railway track. The vehicle 12 is here a trolley comprising a non-deformable chassis 16 resting on a single pair of wheels 18, if necessary with the interposition of a primary suspension. The trolley 12 is preferably without means of propulsion, and simply towed or pushed by the railway machine 14 as the latter advances on the track. The coupling 20 connecting the carriage 12 to the railway machine 14 is here constituted by a connection with two ball joints 22 and two jacks 24 to allow the angular orientation of the chassis 16 to be adjusted relative to the railway machine 14 and to the railway track 1, in particular in a vertical plane and in a transverse plane.It will be noted, however, that the adjustment of the orientation of the chassis 16 relative to the railway track 1 can, if necessary, be obtained by other adjustment means, in particular by controlling actuators arranged at the level of a primary suspension between the chassis 16 and the wheels 18. It will also be noted that the wheels 18 are preferably independent, in the sense that they rotate independently of one another.

[0037] The carriage 12 is instrumented with various measuring devices, and in particular at least one odometer 26 equipping for example one of the wheels 18 of the carriage 12 to determine the distance traveled on the line of rails 2 on which the wheel 18 rolls, or the curvilinear abscissa of the carriage 12 relative to this line of rails 2. Preferably, each of the two wheels 18 is equipped with an odometer 26, so as to be able to directly determine the curvilinear abscissa of the carriage 12 relative to each of the two lines of rails 2 of the railway track 1.

[0038] The carriage 12 further comprises measuring equipment 28 intended to determine the orientation of the chassis 16 relative to each rail line 2, at least in a reference plane of the chassis 16, and preferably in at least two orthogonal planes, namely a horizontal plane H and a longitudinal vertical plane V.

[0039] For this purpose, the measuring equipment comprises, associated with at least one of the two rows of rails 2, and preferably with each of the two rows of rails 2, at least two lateral distance measuring sensors 30 between two reference points of the vehicle and the associated row of rails, the two reference points being at a distance A from each other, as illustrated in the figure 2 . If we note y 1 and y 2 the lateral distances measured between the observed line of rails 2 and each reference point 30 and assuming that when y 1 = y2, the longitudinal axis of the chassis 16 is aligned with the longitudinal axis of the row of rails 2, the measuring equipment allows access to the relative orientation component constituted by the yaw angle ψ R of the chassis relative to the row of rails observed in a horizontal plane, by the equation: ψ R = arctan y 1 − y 2 A

[0040] The precision of the result naturally increases with the distance A, which should preferably be greater than 250mm, and preferably greater than 500.

[0041] Similarly, for the orientation of the chassis of the trolley observed in a vertical plane V, the measuring equipment comprises, associated with at least one of the two rows of rails 2, and preferably with each of the two rows of rails 2, at least two vertical distance measuring sensors 32 between two reference points of the vehicle and the associated row of rails, as illustrated in the figure 1. If we note B the distance between the two reference points 32 aiming at the same row of rails observed, which we will preferably choose to be greater than 250mm, and preferably greater than 500, and z 1 and z 2 the vertical distances measured between the observed line of rails and each reference point and assuming that when z 1 = z 2, the longitudinal axis of the 16th frame is aligned with the longitudinal axis of the rail line, the measuring equipment allows access to the relative orientation component constituted by the pitch angle i R of the chassis relative to the row of rails observed in a vertical longitudinal plane of the chassis, by the equation: θ R = arctan z 1 − z 2 B

[0042] The distance measurement to the rail line 2 can be done with non-contact sensors 30, 32 as illustrated in the figure 3, including proximity sensors, including inductive, photoelectric, magnetic, capacitive, ultrasonic sensors. To avoid interference between sensors targeting the same region of a line of rails, two different types of sensors can be chosen for lateral and vertical distance measurements.

[0043] To the non-deformable chassis 16 of the carriage 12 is fixed an inertial unit 34 with at least three gyrometers and three accelerometers, this inertial unit 34 being said to be precision, in the sense that it is capable of delivering absolute orientation signals, that is to say without drift, in a geostationary reference frame. It is therefore a type of unit whose gyroscopes are capable of detecting the projection of the rotation of the earth and whose accelerometers are capable of detecting the projection of gravity.

[0044] Thus instrumented, the carriage 12 makes it possible to determine on the one hand the absolute orientation of the inertial unit 34 in a geostationary reference frame, and on the other hand the relative orientation of each of the rail lines 2 with respect to the chassis 16, therefore to the inertial unit 34 secured to the chassis 16. To deduce from these metrological data parameters of the geometry of each of the rail lines 2 in an absolute reference frame, a specific method is proposed, illustrated in the figures 4 and 5 .

[0045] While the trolley 12 is traveling at low speed, in particular at a speed of less than 10 km / h, a speed which may not be constant and the machine 14 being likely to slow down, or even stop for a prolonged period at the rate of the work undertaken on the railway track 1, the signals from the odometers 26, the measuring equipment 28 and the inertial unit 34 are simultaneously sampled at constant time intervals.

[0046] As a function of at least signals delivered by the inertial unit 34, successive values ​​of at least one absolute orientation component of the inertial unit 34 in a geostationary reference frame are determined, for example successive values ​​of the roll angle and / or successive values ​​of the pitch angle (operation 40).

[0047] For at least one observed line of rails 2 among the two lines of rails, and preferably for each of the two lines of rails 2 taken as the observed line of rails, successive values ​​of the curvilinear abscissa of the vehicle on the observed line of rails 2 are determined, as a function of at least signals delivered by the odometer 26 associated with the observed line of rails (operation 42).

[0048] We determine, as a function at least of signals delivered by the measuring equipment 28, successive values ​​of at least one component of relative orientation of the observed row of rails 2 with respect to the inertial unit 34, and preferably of the two components discussed previously which are the yaw angle ψ R of the chassis relative to the observed rail line 2, and the pitch angle i R of the chassis relative to the observed rail line (operation 44).

[0049] From these elements, it is possible to calculate, as a function at least of the successive values ​​of the absolute orientation component of the inertial unit and of the successive values ​​of the relative orientation component of the row of rails observed with respect to the inertial unit, successive values ​​of at least one absolute orientation or positioning component of the row of rails observed 2. In practice, an algebraic sum is simply performed of an instantaneous value of the absolute orientation component of the inertial unit and of a simultaneous instantaneous value of the relative orientation component of each of the row of rails observed with respect to the inertial unit (operation 46).

[0050] So, if we note ψR (t) the value at a time t of measurement of the angle determined by the measuring equipment 28 in the horizontal plane between the longitudinal direction of the inertial unit 34 and the direction of the observed line of rails 2, and ψ C (t) the value at the same time t of the yaw angle determined simultaneously by the inertial unit 34, the absolute orientation component ψ A (t) of the observed rail line can be expressed as the algebraic sum: ψ A t = ψ R t + ψ C t

[0051] Similarly, if we note i R (t) the instantaneous value of the angle determined by the measuring equipment in the longitudinal vertical plane between the longitudinal direction of the inertial unit 34 and the direction of the observed line of rails 2, and i C (t) the instantaneous value of the pitch angle determined simultaneously by the inertial unit 34, the absolute orientation component iA (t) of the rail line can be expressed as the algebraic sum: θ A t = θ R t + θ C t

[0052] We are then able to construct one or more functions s → G ( s ) linking at least some of the successive values ​​of the curvilinear abscissa to concomitant values ​​among the successive values ​​of the absolute orientation or positioning component of the line of rails observed in space. (operation 48)

[0053] Thus, for the yaw component of one of the rail lines, the function s → GL ( s ) will be constructed by connecting for all measurement times t or for at least some of them, the value s(t) measured by the odometer associated with the observed line of rails to the value ψ A (t). Similarly, the function s → GT ( s) will be constructed by connecting for all measurement times t or for at least some of them, the value s(t) measured by the odometer associated with the observed line of rails to the value i A (t).

[0054] Once this step is completed in the time domain, one or more functions have been constructed s → G ( s ) where time no longer appears as a variable. We are then able to apply to each function thus constructed a linear band-pass or high-pass filter, which is not a temporal filter, but a spatial filter, so as to construct a filtered function s → F ( s ) (operation 50). The linear filter implemented is preferably a finite impulse response filter of any order N, preferably greater than or equal to 2, which results in the following linear combination: F s n = ∑ k = 0 N − 1 b k . G s n − k Or bkdenotes the kth order coefficient of the filter transfer function, and yes denotes for 1 ≤ i ≤ n the successive values ​​of the curvilinear abscissa of the observed line of rails.

[0055] In practice, if the wish is to observe the parameters of the geometry of the railway according to the wavelength domains defined by the standard, at least one bandpass filter will be implemented in one of the following three bands: 3m to 25m (D1), 25m to 70m (D2), 70m to 150m (D3), or a bandpass filter produced by a deflection calculation function (CF), and in practice, operation 50 will be carried out in parallel for each of the desired wavelength domains among those available, which has been schematized in figure 5 by parallel sub-operations 510, 512, 514, 516.

[0056] Finally, we are able to estimate (operation 52), for a succession of current values ​​of curvilinear abscissa lamong the curvilinear abscissa values, an integral I(l), on a given interval of curvilinear abscissas bounded by a reference curvilinear abscissa value l 0 and by the current value of curvilinear abscissa l , of the filtered function I l = ∫ s = l o s = l F s ds

[0057] In practice, the integral I(l) is estimated by a Riemann sum or by the trapezoid method on the given interval, with a step less than 25cm, and preferably less than 1cm. For example, with a Riemann sum: I l ≈ ∑ n = 1 P F s n . s n − s n − 1 Or s 0 = l 0 and s P = l are the limits of the integration integral.

[0058] Where appropriate, this operation 52 is carried out in parallel for each of the observed wavelength domains, hence the parallel sub-operations 520, 522, 524, 526.

[0059] Assuming that the relative orientation component of the observed rail line 2 with respect to the inertial unit 34 is an orientation angle in a horizontal plane, and the absolute orientation component of the inertial unit is a yaw angle, the integral I(l) will be a dressing parameter.

[0060] Assuming that the relative orientation component of the observed rail line 2 with respect to the inertial unit 34 is an orientation angle with respect to a longitudinal vertical plane of the vehicle, and the absolute orientation component of the inertial unit is a pitch angle, the integral I(l) will be a longitudinal leveling parameter.

[0061] In practice, the calculations can be carried out in real time by a computer on board the vehicle 12, on the machine 14 or located remotely.

[0062] In parallel with these calculation operations, it is possible to use signals delivered by the measuring equipment 28 or successive values ​​of the relative orientation component of the observed row of rails 2 with respect to the inertial unit 34 to control the jacks 24 for coupling the trolley to the machine, with the aim of minimizing the alignment difference between the chassis 16 of the trolley 12 and the railway track 1.

[0063] If we are interested in alignment with respect to the longitudinal direction in the horizontal plane, we can for example construct a negative feedback loop aimed at minimizing the angle ψ R observed for one of the rows of rails 2, or more simply aiming to minimize in absolute value the difference | y 1 - y2 | observed on a row of rails 2. If we are interested in the two rows of rails, we can construct a feedback loop aimed at minimizing the sum of the absolute values ​​of the deviations observed for each of the two rows of rails: (| y 1 - y 2 | + |y 1 - y 2 |).

[0064] Similarly, if we are interested in alignment with respect to the longitudinal direction in the horizontal plane, we can for example construct a negative feedback loop aimed at minimizing the angle i R observed for one of the lines of rails, or more simply aiming to minimize in absolute value the difference | z 1 - z 2 | observed on a row of rails. If we are interested in the two rows of rails, or aiming to minimize the sum of the absolute values ​​of the deviations observed for each of the two rows of rails: (| z 1 - z 2 | + | z 1 - z 2 |).

[0065] If necessary, failures of the odometer(s) 26 can be detected by comparing longitudinal acceleration values ​​delivered by the inertial unit 34 with average acceleration values ​​determined as a function of the signals delivered by the odometer(s) 26 and / or by comparing angular velocity values ​​around a vertical axis delivered by the inertial unit 34 with angular velocity values ​​deduced from the signals delivered by the odometer(s) 26. When a failure is detected, a degraded mode operating procedure is executed, in which the successive curvilinear abscissa values ​​of the vehicle 12 are determined on each of the two lines of rails 2 as a function of at least accelerometric signals or angular velocity delivered by the inertial unit 34.

[0066] Naturally, the examples shown in the figures and discussed above are given for illustrative purposes only and are not limiting. It is explicitly provided that the different embodiments illustrated can be combined with each other to propose others.

[0067] As stated in the disclosure of the invention, other principles for measuring the relative orientation of the inertial unit with respect to each of the lines of rails are envisaged.

[0068] It is also possible to consider equipping the trolley with only one odometer, allowing the curvilinear abscissa of one of the lines of rails to be measured directly. The operation of determining the successive values ​​of the curvilinear abscissa of the opposite line of rails can then be carried out as a function of at least the signals delivered by the odometer and the signals delivered by the measuring equipment.

[0069] The method for determining the geometry parameters of the railway track described above can also be carried out using a four-wheeled trolley, or more generally a railway vehicle which can rest on several wheel sets or on several bogies. Where appropriate, the chassis to which the inertial unit is secured can be linked to the wheels by one or more suspension stages, for example a primary suspension and / or a secondary suspension.

[0070] In these hypotheses, the equipment for measuring the relative orientation of each of the rows of rails in relation to the inertial unit will preferably use measurement principles other than those described so far.

[0071] According to one embodiment, the measuring equipment comprises at least one and preferably at least two cameras for detecting one or more linear laser beams projected onto each of the rows of rails. For example, each camera is fixed to the frame carrying the inertial unit in a fixed manner in the frame of reference of the inertial unit, and oriented so as to aim and capture the position of a laser line projected onto the row of rails observed, the measuring equipment determining by triangulation the relative vertical and lateral position between the row of rails observed and the camera.

[0072] According to another embodiment, the measuring equipment comprises at least one and preferably at least two laser rangefinders also placed in the reference frame of the inertial unit so as to scan the lines of rails of the railway. According to the principle of laser telemetry, the distance is given by measuring the delay between the emission of a pulse and the detection of a reflected pulse. The projected laser beam is oriented by a rotating mirror, which makes it possible to scan a plane of space which can cover the two lines of rails and to deduce therefrom by triangulation for each line of rails a lateral distance measurement and a vertical distance measurement. With two laser rangefinders placed at a distance from each other in the longitudinal direction of the vehicle, it is thus possible to obtain the eight desired dimensions, namely four lateral distances and four vertical distances.

[0073] According to another variant, the measuring equipment includes at least one time-of-flight camera (ToF camera, "time of flight") placed in the frame of reference of the inertial unit, making it possible to visualize a scene in three dimensions in its field of vision. Since the field of vision of this type of camera is relatively narrow, it will be advantageous to use one camera of this type per line of rails.

Claims

1. A method for determining at least one geometric parameter of a railroad track (1) with two rows of rails (2), in which: - a vehicle (10) carrying an inertial unit (34), a piece of equipment (28) for measuring at least one relative orientation component of at least one of the two rows of rails with respect to the inertial unit, and one or more odometers (26) is made to travel over the railroad track (1), - successive values of at least one absolute orientation component of the inertial unit (34) in a geostationary reference frame are determined on the basis of at least signals produced by the inertial unit (34), - for at least one observed row of rails (2) from the two rows of rails (2), and preferably for each of the two rows of rails (2) taken as an observed row of rails, i) successive curved-abscissa values of the vehicle on the observed row of rails (2) are determined on the basis of at least signals produced by the odometer(s) (26), ii) successive values of at least one relative orientation component of the observed row of rails with respect to the inertial unit (34) are determined on the basis of at least signals produced by the measuring equipment (28), iii) successive values of at least one absolute orientation or absolute positioning component of the observed row of rails (2) are calculated on the basis of at least the successive values of the absolute orientation component of the inertial unit (34) and the successive values of the relative orientation component of the observed row of rails (2) with respect to the inertial unit (34), characterized in that: iv) a function s → G (s) is constructed which links at least some of the successive curved-abscissa values to concomitant values from the successive values of the absolute orientation or absolute positioning component of the row of rails observed in space, v) a high-pass or band-pass linear filter is applied to the function s → G (s) so as to construct a filtered function s → F (s), vi) for a succession of current curved-abscissa values l from the curved-abscissa values, an integral I(l) is estimated, over a given curved-abscissa interval bounded by a reference curved-abscissa value l0 and by the current curved-abscissa value l, from the filtered function I l = ∫ s = l o s = l F s ds 2. The method according to claim 1, characterized in that the linear filter is a band-pass filter, preferably in one of the three following bands: 3 m to 25 m, 25 m to 70 m, 70 m to 150 m, or an arrow calculation function.

3. The method according to either of the preceding claims, characterized in that the integral I(l) is estimated by a Riemann sum or by the trapezoidal method over the given interval, with a step size of less than 25 cm, and preferably less than 1 cm.

4. The method according to any of the preceding claims, characterized in that the operation of calculating successive values of at least one absolute orientation or positioning component of the observed row of rails (2) consists, at successive times, of an algebraic sum of an instantaneous value of the absolute orientation component of the inertial unit and of a simultaneous instantaneous value of the relative orientation component of each of the observed rows of rails with respect to the inertial unit.

5. The method according to any of the preceding claims, characterized in that the relative orientation component of the observed row of rails (2) with respect to the inertial unit (34) is an orientation angle in a horizontal plane, and the absolute orientation component of the inertial unit is a yaw angle, the integral I(l) being an alignment parameter.

6. The method according to any of the preceding claims, characterized in that the relative orientation component of the observed row of rails (2) with respect to the inertial unit (34) is an orientation angle with respect to a vertical longitudinal plane (V) of the vehicle (12), and the absolute orientation component of the inertial unit is a pitch angle, the integral I(l) being a longitudinal leveling parameter.

7. The method according to any of the preceding claims, characterized in that for each observed row of rails (2), the measuring equipment produces at least two simultaneous signals for measuring the lateral distance between two reference points (30) on the vehicle (12) and the observed row of rails (2), the two reference points (30) being separated from one other by a distance (A) of greater than 250 mm, and preferably greater than 500 mm.

8. The method according to any of the preceding claims, characterized in that for each observed row of rails (2), the measuring equipment produces at least two simultaneous signals for measuring the vertical distance between two reference points (32) on the vehicle (12) and the observed row of rails (2), the two reference points (32) being separated from one other by a distance (B) of greater than 250 mm, and preferably greater than 500 mm.

9. The method according to any of the preceding claims, characterized in that at least one actuator (24) for correcting the alignment of the vehicle (12) on the railroad track (1) can be controlled on the basis of the signals produced by the measuring equipment (28) or successive values of the relative orientation component of the observed row of rails (2) with respect to the inertial unit (34), in order to reduce a drift between the signals produced by the measuring equipment (38) and predetermined values or to reduce a drift between the successive values of the relative orientation component of the observed row of rails (2) and a predetermined value of the relative orientation component of the observed row of rails (2).

10. The method according to any of the preceding claims, characterized in that the operation of determining the successive curved-abscissa values of the vehicle (12) on the observed row of rails (2) is performed on the basis of at least signals produced by an odometer (26) associated with the observed row of rails (2) from the odometer(s).

11. The method according to any of the preceding claims, characterized in that the operation of determining the successive curved-abscissa values of the vehicle on the observed row of rails (2) is performed on the basis of at least signals produced by an odometer (26) not associated with the observed row of rails (2) from the odometer(s) and signals produced by the measuring equipment (28).

12. The method according to any of the preceding claims, characterized in that failures of the odometer(s) (26) can be detected by comparing longitudinal acceleration values produced by the inertial unit (34) with average acceleration values determined on the basis of the signals produced by the odometer(s) (26) and / or by comparing angular velocity values about a vertical axis produced by the inertial unit (34) with angular velocity values deduced from the signals produced by the odometer(s) (26).

13. The method according to claim 12, characterized in that when a failure is detected, a safety procedure is carried out, in which successive curved-abscissa values of the vehicle (12) on each of the two rows of rails (2) are determined on the basis of at least accelerometric or angular velocity signals produced by the inertial unit (34).

14. A system for implementing the method according to any of the preceding claims, comprising a vehicle capable of traveling on a railroad track (1) with two parallel rows of rails (2), the vehicle (12) carrying an inertial unit (34) with at least three gyrometers and three accelerometers, a piece of equipment (28) for measuring a relative orientation of each of the two rows of rails (2) with respect to the inertial unit, and one or more odometers (26), characterized in that the system further comprises computing means programmed to perform the operations of calculating successive values of at least one absolute orientation or positioning component of an observed row of rails (2) from the two rows of rails, constructing the function s → G (s), applying a linear filter, constructing the filtered function s → F (s), and estimating the integral I(l).

15. The system according to claim 14, characterized in that the measuring equipment (28) comprises, associated with each of the two rows of rails (2), at least two sensors for measuring the lateral distance (30) between two reference points on the vehicle and the associated row of rails, the two reference points being separated from one another by a distance (A) of greater than 250 mm, and preferably greater than 500 mm.

16. The system according to either of claims 14 to 15, characterized in that the measuring equipment (28) comprises, associated with each of the two rows of rails (2), at least two sensors for measuring the vertical distance (32) between two reference points on the vehicle and the associated row of rails (2), the two reference points being separated from one another by a distance (B) of greater than 250 mm, and preferably greater than 500 mm.

17. The system according to any of claims 14 to 16, characterized in that the measuring equipment (28) comprises at least one, and preferably at least two, camera(s) for detecting one or more linear laser beams projected onto each of the rows of rails.

18. The system according to any of claims 14 to 17, characterized in that the measuring equipment (28) comprises at least one, and preferably at least two, laser range finder(s) which scan(s) the rows of rails of the railroad track.

19. The system according to any of claims 14 to 18, characterized in that the vehicle (12) is a two-wheeled cart (18) which is driven by a machine (14) and connected to the machine via at least three links (22, 24) for controlling the position and alignment of the cart (12) on the basis of relative orientation components.

20. The system according to any of claims 14 to 18, characterized in that the vehicle (12) is a cart with at least four wheels.