EP2927089B1 - Method for computing an interval of positions for a railway vehicle along a railway track and corresponding device - Google Patents

Description

The present invention relates to a method for calculating a position interval of a railway vehicle on a railway track, said position interval corresponding to a segment of the track between a front end and a rear end.

The invention applies to the field of railway safety, in particular to automatic control systems for rail traffic. Such systems are, for example, so-called "train-based communication management systems", or CBTC (Communication Based Train Control).

In a conventional manner, for a rail vehicle traveling on a railway track, the interval of positions of the vehicle on the railway is determined by an on-board computer on board the vehicle. The position interval of the vehicle is then sent, for example by radio waves, to a central computer on the ground. The ground computer is adapted to receive the range of positions of a plurality of railway vehicles and to control the running or stopping of each vehicle according to the range of positions of other vehicles and other points of contact. constraints present on the way. For example, a poorly positioned switch will lead the computer to the ground to command the stopping of the trains approaching this switch.

For the purpose of the present invention, the term "position range" is understood to mean a segment of a railway line in which the railway vehicle is likely to be with an uncertainty lower than a predetermined threshold.

The on-board computer is adapted to determine the position of the vehicle from for example beacons arranged on the railway, and whose locations on the railway are previously known. More precisely, the on-board computer determines the range of positions of the railway vehicle from the location of the last beacon encountered and the movement of the vehicle from the latter beacon, said displacement being for example measured by an odometer.

In certain situations, the on-board computer is no longer able to calculate the position interval of the rail vehicle with sufficient accuracy. This is called loss of location. A loss of location occurs for example if no new beacon is detected after the rail vehicle has traveled a distance greater than or equal to a predetermined threshold, since the last beacon detected. For safety reasons, a control system of the railway vehicle then controls the stopping of the vehicle.

In case of stopping the railway vehicle, it is known to involve an operator to manually operate the stopped railway vehicle and route it to the next functional beacon, so that the onboard computer determines again the range of positions of the vehicle to allow a return to the autonomous and automatic operation of the railway vehicle.

It is also known to allow a remote operator to maneuver the railway vehicle, after the operator has verified the absence of obstacles in the direction towards which he wishes to route the railway vehicle. As before, automatic operation is found as soon as the railway vehicle meets a functional beacon.

The document EP 1 388 480 A1 discloses a system for determining the position of a railway vehicle.

Nevertheless, such methods are not entirely satisfactory.

Indeed, such methods require the intervention of an operator, which is likely to lead to incidents related to human error. In addition, such methods involve the immobilization of the railway vehicle for long periods, for example the intervention time of the operator, which is even more penalizing for driverless transport systems. This affects the quality of the traffic, especially for urban transport networks.

An object of the invention is therefore to provide a method of locating a railway vehicle that allows safe and automated operation, and rapid recovery of rail traffic in case of loss of location.

• d'identification, par des capteurs à la voie, d'un canton de la voie ferrée occupé par le véhicule ferroviaire ;
• de transmission, à un ordinateur au sol, d'un identifiant du canton occupé ;
• de calcul, par l'ordinateur au sol, d'un intervalle de positions du véhicule ferroviaire en tenant compte d'une position géographique du canton occupé associée à l'identifiant dudit canton occupé; et
• de transmission, depuis un calculateur embarqué à bord du véhicule ferroviaire vers l'ordinateur au sol, d'un intervalle de positions du véhicule ferroviaire déterminé par ledit calculateur embarqué, l'étape de calcul d'un intervalle de positions du véhicule ferroviaire tenant également compte de l'intervalle de positions déterminé par ledit calculateur embarque.

For this purpose, the subject of the invention is a process of the aforementioned type, in which the process comprises the steps of:

• identification, by track sensors, of a township of the railway track occupied by the railway vehicle;
• transmitting, to a computer on the ground, an identifier of the occupied township;
• calculating, by the computer on the ground, an interval of positions of the railway vehicle taking into account a geographical position of the occupied township associated with the identifier of said occupied township; and
• transmission, from an on-board computer on board the rail vehicle to the computer on the ground, a position interval of the railway vehicle determined by said on-board computer, the step of calculating a position interval of the railway vehicle also holding account of the position interval determined by said board computer.

Indeed, the calculation of the position interval of the rail vehicle by a computer on the ground from information provided by sensors to the track allows a safe and automated location of the railway vehicle, even if the onboard computer is no longer able to calculate this location.

• l'étape de calcul d'un intervalle de positions comprend une première phase dans laquelle l'intervalle de positions est pris égal à l'intervalle de positions du véhicule ferroviaire déterminé par le calculateur embarqué, et une deuxième phase dans laquelle une extrémité avant de l'intervalle de positions est déplacée suivant la direction de déplacement du véhicule ferroviaire jusqu'à atteindre une extrémité du canton occupé, qui se trouve en avant du véhicule ferroviaire ;
• l'extrémité avant de l'intervalle de positions est déplacée au cours de cycles de calcul successifs de durée prédéterminée d'une distance égale au produit de la vitesse du véhicule ferroviaire par la durée prédéterminée ;
• le procédé comporte en outre une étape de calcul, par l'ordinateur au sol, d'un deuxième intervalle de positions du véhicule ferroviaire à partir de l'intervalle de positions du véhicule ferroviaire déterminé par le calculateur embarqué, l'étape de calcul comportant une première phase dans laquelle l'ordinateur détermine une position limite avant que le véhicule ferroviaire n'est pas autorisé à dépasser, une deuxième phase dans laquelle le deuxième intervalle de position est prise égale à l'intervalle de positions déterminé par le calculateur embarqué, et une troisième phase dans laquelle une extrémité avant de la deuxième position est déplacée jusqu'à atteindre la limite avant ;
• l'extrémité avant du deuxième intervalle de positions est déplacée au cours de cycles de calcul successifs de durée prédéterminée d'une distance égale au produit de la vitesse du véhicule ferroviaire par la durée prédéterminée ;
• si la vitesse du véhicule n'est pas disponible, la distance est égale au produit de la vitesse maximale du véhicule ferroviaire par la durée prédéterminée ;
• le procédé comporte une étape de calcul d'un intervalle auxiliaire du véhicule ferroviaire, l'intervalle auxiliaire étant égal à une intersection du premier intervalle de positions et d'un deuxième intervalle de positions.

According to other advantageous aspects of the invention, the method comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

• the step of calculating a position interval comprises a first phase in which the position interval is taken equal to the position interval of the rail vehicle determined by the onboard computer, and a second phase in which a front end of the range of positions is moved in the direction of travel of the railway vehicle to an end of the occupied block, which is in front of the railway vehicle;
• the front end of the position interval is displaced during successive calculation cycles of predetermined duration by a distance equal to the product of the rail vehicle speed by the predetermined duration;
• the method further comprises a step of calculating, by the computer on the ground, a second interval of positions of the railway vehicle from the position interval of the railway vehicle determined by the onboard computer, the calculation step comprising a first phase in which the computer determines a limit position before the railway vehicle is not allowed to overtake, a second phase in which the second position interval is taken equal to the position interval determined by the onboard computer, and a third phase in which a leading end of the second position is moved to the front limit;
• the front end of the second position interval is moved during successive calculation cycles of predetermined duration by a distance equal to the product of the rail vehicle speed by the predetermined duration;
• if the speed of the vehicle is not available, the distance is equal to the product of the maximum speed of the railway vehicle by the predetermined duration;
• the method comprises a step of calculating an auxiliary interval of the railway vehicle, the auxiliary interval being equal to an intersection of the first position interval and a second position interval.

In addition, the subject of the invention is a device for calculating a range of positions of a railway vehicle on a railway, for the implementation of the calculation method as defined above.

• la figure 1 est une représentation schématique d'un dispositif de localisation propre à mettre en oeuvre un procédé de localisation selon l'invention ;
• la figure 2 est une représentation schématique d'une situation de fonctionnement normal du véhicule ferroviaire ;
• la figure 3 est une représentation schématique d'une phase intermédiaire d'une première étape du procédé de localisation selon l'invention ;
• la figure 4 est une représentation schématique d'une phase finale de l'étape de la figure 3 ;
• la figure 5 est une représentation schématique d'une phase intermédiaire d'une deuxième étape du procédé selon l'invention ;
• la figure 6 est une représentation schématique d'une phase finale de l'étape de la figure 5 ;
• la figure 7 est une représentation schématique d'une première étape du procédé de localisation d'un véhicule ferroviaire suite à la remise en service d'un calculateur embarqué du dispositif de localisation ;
• la figure 8 est une représentation schématique d'une étape successive à l'étape de la figure 7 ;
• la figure 9 est une représentation schématique d'une étape successive à l'étape de la figure 8 ; et
• la figure 10 est une représentation schématique d'une étape successive à l'étape de la figure 9.

The invention will be better understood with the aid of the description which follows, given solely by way of nonlimiting example and with reference to the appended drawings in which:

• the figure 1 is a schematic representation of a localization device adapted to implement a localization method according to the invention;
• the figure 2 is a schematic representation of a normal operating condition of the railway vehicle;
• the figure 3 is a schematic representation of an intermediate phase of a first step of the locating method according to the invention;
• the figure 4 is a schematic representation of a final phase of the stage of the figure 3 ;
• the figure 5 is a schematic representation of an intermediate phase of a second step of the method according to the invention;
• the figure 6 is a schematic representation of a final phase of the stage of the figure 5 ;
• the figure 7 is a schematic representation of a first step of the locating method of a railway vehicle following the return to service of an on-board computer of the locating device;
• the figure 8 is a schematic representation of a successive step at the stage of figure 7 ;
• the figure 9 is a schematic representation of a successive step at the stage of figure 8 ; and
• the figure 10 is a schematic representation of a successive step at the stage of figure 9 .

A railway vehicle 2 traveling on a railway line 4 is represented on the figure 1 .

The location of the railway vehicle 2 is achieved by a locating device 3 comprising a ground component and an onboard component.

"Location" means the calculation of a range of positions of the railway vehicle 2 on the railway line 4.

For the ground component, the railway line 4 is subdivided into a plurality of successive blocks 6. Each canton is identified by an identifier, which is associated with the geographical position of the canton.

A plurality of secondary detection devices 8, also called track sensors, are arranged along the railway line 4. Each secondary detection device 8 is associated with a block 6. For example, the railway line 4 comprises a first block 6A, a second block 6B and a third block 6C, each block 6A, 6B, 6C being associated with a corresponding secondary detection device 8.

Each secondary detection device 8 is able to determine whether the corresponding block 6 is vacant or occupied. By "busy" is meant a block 6 on which the railway vehicle 2 is engaged at least partially.

The secondary detection devices 8 are, for example, track circuits or axle counters.

Each secondary detection device 8 is further connected to a computer on the ground 12 for transmitting to the computer on the ground 12 information relating to the occupied or vacant state of the corresponding block 6. In addition, each secondary detection device 8 is able to transmit to the computer on the ground 12 the identifier of the corresponding block 6.

For the onboard component, a plurality of beacons (not shown) are arranged along the railway line 4. The beacons are arranged successively along the railway line 4, at predetermined geographical locations. Each tag is identified by a unique tag ID.

The railway vehicle 2 comprises at least one beacon sensor, that is to say an antenna, able to detect the presence of a beacon when it is close to it and to capture information relating to that beacon. tag detected. Preferably, the beacon is able to communicate its beacon identifier to the beacon sensor of the railway vehicle 2.

The railway vehicle 2 also comprises instruments for measuring the movement, speed or acceleration of the railway vehicle 2. The measuring instruments are, for example, odometers or accelerometers.

In addition, the railway vehicle 2 comprises an onboard computer 10.

The measuring instruments and the beacon sensor are connected to the onboard computer 10.

The beacon sensor is capable of transmitting, to the onboard computer 10, data relating to the beacons detected. In particular, the beacon sensor is capable of transmitting, to the on-board computer 10, the beacon identifier of each beacon detected during the movement of the railway vehicle 2 along the railway line 4.

The on-board computer 10 includes a memory in which are stored the beacon identifier and the geographical location of each of the beacons of the railway line 4.

The on-board computer 10 is able to convert the measurements made by the measuring instruments into a measurement of the displacement and / or speed of the railway vehicle 2. For example, for measuring instruments adapted to measure the movement of the railway vehicle 2, the embedded calculator 10 is clean to determine the speed of the railway vehicle 2 by derivation in relation to the time of displacement. For example, for the measuring instruments adapted to measure the instantaneous speed of movement of the railway vehicle 2, the on-board computer 10 is able to calculate the distance traveled by the railway vehicle 2 by integration with respect to the speed of the railway vehicle 2 For example, for measuring instruments adapted to measure the instantaneous acceleration of the railway vehicle 2, the on-board computer 10 is able to calculate the speed of the railway vehicle 2, then the distance traveled by the railway vehicle 2, by successive integrations by relation to the acceleration time of the railway vehicle 2.

The on-board computer 10 is also able to calculate an interval of positions S ₀ of the railway vehicle 2. As illustrated by FIG. figure 2 , the interval S ₀ corresponds to a front end segment A ₀ and a rear end segment Z ₀ . In particular, the on-board computer 10 is able to calculate an interval S ₀ of the railway vehicle 2 from the location of the last beacon detected by the beacon detector. In particular, the on-board computer 10 is able to determine an interval S ₀ of the railway vehicle 2 from the location of the last detected beacon and the movement of the railway vehicle from said last beacon detected, the displacement being measured by the instruments of measurement of the railway vehicle 2 or calculated by the on-board computer 10 from measurements made by the rail vehicle measuring instruments 2. Advantageously, the on-board computer 10 is able to take into account, when calculating the interval S ₀ , a potential margin of error related to the precision of the measuring instruments used, which leads to a safe calculation of the position interval S ₀ . For example, for an odometer, the margin of error takes into account the coefficient of adhesion between a wheel of railway vehicle 2 and a rail of track 4, this coefficient not being 100%.

The onboard computer 10 is further adapted to generate an alert signal in case of loss of location. By "loss of location" is meant a situation in which the data received by the on-board computer 10 do not make it possible to determine the position interval S ₀ of the railway vehicle 2 with an error lower than a predetermined threshold. The on-board computer 10 is for example configured to generate an alert signal if the location of a detected beacon is outside the position interval S ₀ of the rail vehicle calculated at this instant by the on-board computer 10. embedded computer 10 is for example configured to generate an alert signal if no tag has been detected after a displacement of predetermined length since the detection of the last tag. In addition, the onboard computer 10 is for example configured to generate an alert signal if, at the same time, the values of the displacement or speed measurements are different from one measuring instrument to another. For example when the means of odometries are redundant in the train it is possible to generate an alert if one of the odometers indicates that the train is stopped while the other odometer indicates that the train is moving.

Advantageously, the onboard computer 10 is also configured to generate an alert signal if railway vehicle integrity detectors 2 detect a loss of integrity of the railway vehicle 2, during a time interval of less than a predetermined duration duration. The railway vehicle 2 is said to be honest if it did not lose any cars during its journey. Preferably, the onboard computer 10 is configured to emit an alert signal after it is put into operation after a standby or an extinction. In this case, when the on-board computer 10 is put on standby or off, the ground computer 12 stores the orientation of the railway vehicle 2 with respect to the track 4, that is to say that the computer on the ground 12 stores the direction of travel of the railway vehicle 2.

The onboard computer 10 is able to communicate with the computer on the ground 12. The on-board computer 10 and the computer on the ground 12 are for example suitable for communicating with each other by radio waves.

The on-board computer 10 is able to transmit, to the computer on the ground 12, the last position interval S ₀ of the railway vehicle 2 calculated by the on-board computer 10.

The on-board computer 10 is also able to transmit, to the computer on the ground 12, the displacement values and the measured and / or calculated speed values.

The onboard computer 10 is further adapted to issue the alert signal to the computer on the ground 12, the alert indicating a loss of location.

The computer on the ground 12 includes a memory (not shown) in which the identifier of each block 6 is associated with the geographical position of the block 6.

The computer on the ground 12 is able to calculate a front limit position A _max and a rear limit position Z _max for the railway vehicle 2. The front limit positions A _max and rear Z _max are respectively the point of the railway line 4 downstream. of the railway vehicle 2 and the point of the railway line 4 upstream of the railway vehicle 2 that the railway vehicle 2 is not allowed to override by the movement commands given by the ground computer 12. In normal operation, the instantaneous position of the railway vehicle 2 is always between the limit positions before A _max and rear Z _max .

The computer on the ground 12 is able to retransmit the limit positions before A _max and rear Z _max to the onboard computer 10 and / or to a control system (not shown) of the railway vehicle 2. The limit positions A _max , Z _max correspond to the maximum movement authorizations given to the train. The on-board computer 10 is able to guarantee in safety that these positions are never exceeded by the railway vehicle 2.

The limit position before A _max depends on the spacing with the railway vehicle downstream of the railway vehicle 2 considered. The front limit position A _max is advantageously located, downstream of the railway vehicle 2, and with respect to the front of the railway vehicle 2, at a distance greater than 100 m, preferably greater than 200 m, for example equal to 500 m .

The rear limit position Z _max advantageously lies, upstream of the railway vehicle 2, and with respect to the rear of the railway vehicle 2, at a distance of less than 100 m, preferably less than 50 m, for example equal to 20 m .

The computer on the ground 12 is able to calculate a position interval of the railway vehicle 2 called "auxiliary interval" S _x , from the information received from the onboard computer 10, the secondary detection devices 8 and the limit positions A _max , Z _max provided by the ground computer 12 itself. As illustrated on the figure 1 , the auxiliary interval S _x has a front end A _x and a rear end Z _x .

For example, the computer on the ground 12 is able to calculate the auxiliary interval S _x of the railway vehicle 2 when receiving an alert signal from the onboard computer 10. The computer on the ground 12 is suitable for calculate the auxiliary interval S _x of the railway vehicle 2 from the last position of the railway vehicle 2 which has been calculated by the on-board computer 10, from the measured and / or calculated values of displacement and / or speed, from secondary detection devices 8 and from the limit positions A _max and Z _max provided by the ground computer 12 itself.

The computer on the ground 12 is able to transmit, to the onboard computer 10, the auxiliary interval S _x of the railway vehicle 2.

The locating device 3 is able to determine the interval S ₀ and / or the auxiliary interval S _x of the railway vehicle from data received by the onboard computer 10 and / or the ground computer 12.

The operation of the locating device 3 will now be described.

During an initial step of normal operation of the railway vehicle 2, there is no loss of location by the onboard computer and no alert has been issued. The on-board computer 10 determines the position interval S ₀ of the railway vehicle 2. The interval S ₀ is called the "initial interval" of the railway vehicle 2.

In the example illustrated by the figure 2 the railway vehicle 2 occupies the second block 6B. Thus, the second canton 6B is occupied and the first and third cantons 6A, 6C are vacant.

At the end of the initial step, a loss of location occurs. The on-board computer 10 then sends an error signal to the computer on the ground 12. The on-board computer 10 also transmits to the computer on the ground 12 the initial interval S ₀ of the railway vehicle 2 before the occurrence of the loss. location. In addition, the on-board computer 10 transmits to the computer on the ground 12 the value of the displacement and / or the speed of the railway vehicle 2 which is measured respectively by the displacement measuring instruments and by the speed measuring instruments.

The ground computer 12 then calculates a first auxiliary interval S _p , during a first step of the method, and a second auxiliary interval S _d , during a second step of the localization process. The computer on the ground 12 then calculates the intersection of the auxiliary intervals S _p and S _d to determine the auxiliary interval S _x , visible on the figure 1 .

The first auxiliary interval S _p and the second auxiliary interval S _d are respectively visible on the figures 4 and 6 . The first auxiliary interval S _p has a front end A _p and a rear end Z _p . The second auxiliary interval S _d has a front end A _d and a rear end Z _d .

As illustrated by Figures 3 and 4 the ground computer 12 calculates the first auxiliary interval S _p from the initial interval S ₀ and the limit positions before A _max and back Z _max .

The front end A _p is first taken equal to the front end A ₀ of the interval S ₀ . During successive calculation cycles of duration T, the ground computer 12 calculates a new location of the point A _p of the first auxiliary interval S _p . In particular, during the successive calculation cycles, the point A _p is moved on the track 4 according to the direction of travel of the railway vehicle 2, by an amount equal to the speed v of the railway vehicle 2 at the instant of calculated, multiplied by the duration T. For example, on the figure 3 , and for a constant speed v of the railway vehicle 2, at the end of a strictly positive integer number N of calculation cycles, the point A _p is situated at a distance N * v * T according to the direction of movement of the vehicle rail 2 with respect to the front end A ₀ of the interval S ₀ . Advantageously, in the case of a loss of location due to an inconsistency of measurement between the different measuring instruments of the railway vehicle 2, the speed v used is the maximum speed accessible to the railway vehicle 2.

In addition, the rear end Z _p is equal to the rear limit point Z _max .

The calculation stops when the point A _p of the first auxiliary interval reaches the limit point before A _max .

As a variant, the front ends A _p and the rear ends Z _p of the first auxiliary interval S _p are respectively equal to the limit points before A _max and rear Z _max from the first calculation cycle.

As illustrated by Figures 5 and 6 the ground computer 12 calculates the second auxiliary interval S _d from the initial interval S ₀ and the information transmitted by the secondary detection devices 8 relating to the occupied or vacant state of the cantons 6.

In the example illustrated by the figure 2 at the end of the initial stage, the second block 6B is occupied and the first and third blocks 6A, 6C are vacant.

The front end A _d is first taken equal to the front end A ₀ of the initial interval S ₀ . During successive calculation cycles of duration T, the ground computer 12 calculates a new location of the point A _d of the second auxiliary interval S _d . In particular, during successive calculation cycles, point A _d is moved on track 4 in the direction of travel of railway vehicle 2 by an amount equal to the speed v of rail vehicle 2 at the calculation time. , multiplied by the duration T. For example, on the figure 5 , and for a constant speed v of the railway vehicle 2, at the end of a strictly positive integer number N of calculation cycles, the point A _d is situated at a distance N * v * T according to the direction of movement of the vehicle rail 2 with respect to the front end A ₀ of the initial interval S ₀ . Advantageously, in the case of a loss of location due to an inconsistency of measurement between the different measuring instruments of the railway vehicle 2, the speed v used is the maximum speed accessible to the railway vehicle 2.

The calculation stops when the front end A _d of the second auxiliary interval S _d reaches the transition between the currently occupied block and the vacant front block, i.e., in the example, at the transition between the second township 6B and the third township 6C. The rear end location Z _d is then taken equal to the transition between the currently occupied block and the rear vacant block, that is, in the example, at the transition between the second block 6B and the first block. township 6A.

Depending on the instantaneous position of the railway vehicle 2 at the time of the occurrence of the loss of location, the block 6 occupied at the end of the calculation of the second auxiliary interval S _d is the same or different from the block 6 occupied at the beginning of the calculating the second auxiliary interval S _d .

Preferably, and as it appears on the figure 6 at the end of the calculation previously defined, the front end A _d is shifted forwards by a first predefined offset D _A and the rear end Z _d is shifted towards the rear of a second offset predefined D _Z. The first offset D _A and the second offset D _Z make it possible to take into account any delays, for each secondary detection device 8, for detecting the entrance of the railway vehicle 2 on a corresponding block 6 or the exit of the railway vehicle 2 from a corresponding 6 canton.

The first offset D _A is advantageously between 10 m and 400 m, preferably between 50 m and 300 m, for example between 100 m and 200 m.

The second shift D _Z is advantageously between 10 m and 200 m, preferably between 20 m and 150 m, for example between 30 m and 100 m.

$${\mathrm{Z}}_{\mathrm{x}}=\max \left({\mathrm{Z}}_{\mathrm{p}},{\mathrm{Z}}_{\mathrm{d}}\right)$$

The computer on the ground 12 then calculates the auxiliary interval S _x . The auxiliary interval S _x is the intersection of the first auxiliary interval S _p and the second auxiliary interval S _d . In particular : $${\mathrm{AT}}_{\mathrm{x}}=\min \left({\mathrm{AT}}_{\mathrm{p}},{\mathrm{AT}}_{\mathrm{d}}\right)$$

$${\mathrm{Z}}_{\mathrm{x}}=\max \left({\mathrm{Z}}_{\mathrm{p}},{\mathrm{Z}}_{\mathrm{d}}\right)$$

The computer on the ground 12 then transmits the auxiliary interval S _x to the on-board computer 10.

On receiving the auxiliary interval S _x , the on-board computer 10 takes the auxiliary interval S _x as its current position interval S ₀ . The onboard computer 10 no longer emits an alert signal. The railway vehicle 2 is then authorized to resume its journey on the railway line 4.

Advantageously, the duration between the transmission of the warning signal by the on-board computer 10 to the computer on the ground 12, and the reception of the auxiliary interval Sx by the on-board computer 10 from the computer on the ground 12, is less than 20 s, preferably less than 10 s, for example less than 5 s.

As shown on the figure 7 , in the case of a restarting of the on-board computer 10 after a standby or an extinction, the on-board computer 10 emits an alert signal indicating a loss of location to the computer on the ground 12. computer on the ground 12 has previously memorized the orientation of the railway vehicle 2 relative to the track 4, that is to say the relative position of the head car of the railway vehicle 2, also called "before" with respect to the position of the tail car, also called "back".

In a next step, illustrated by the figure 8 , the computer on the ground 12 calculates the second auxiliary interval S _d according to the method described above. In particular, the location of the front end A _d of the second auxiliary interval S _d is taken as equal to the transition between the currently occupied block and the vacant block before, that is to say, in the example, at the transition between the second canton 6B and the third canton 6C. Then the front end A _d is shifted forward of the first predefined offset D _A.

In a next step, illustrated by the figure 9 , the computer on the ground 12 determines the location of a point P of the railway line 4. The point P is a point situated downstream, according to the orientation of the railway vehicle 2, of the rear end Z _d of the second auxiliary interval S _d . The point P is at a distance L from the rear end Z _d , the distance L being equal to the length of the railway vehicle 2. The point P is the most upstream point of the railway line 4 where is likely to find the head of the railway vehicle 2.

In a next step, illustrated by the figure 10 the ground computer 12 calculates the location of the front limit A _max from the location of the point P. The computer on the ground 12 then transmits the second auxiliary interval S _d to the on-board computer 10, as well as the front limit A _max .

On receipt of the second auxiliary interval S _d , the on-board computer 10 takes the second auxiliary interval S _d as its current position interval S ₀ . The onboard computer 10 no longer emits an alert signal. The railway vehicle 2 is then authorized to move on the railway line 4.

Claims (8)

1. A method for computing a range of positions of a railway vehicle (2) on a railway track (4), said range of positions corresponding to a segment of the track (4) between a front end and a rear end, the method including the steps:

   - identifying, by sensors on the track (8), a block (6) of the railway track (4) occupied by the railway vehicle (2);

   - transmitting to a computer (12) on the ground, an identifier of the occupied block (6); and,

   - computing, by the ground computer (12) a range of positions (S_d) of the railway vehicle (2) by taking into account a geographic position of the occupied block (6) associated with the identifier of said occupied block (6),

   characterised in that it comprises a step for transmitting, from an onboard computer (10) of the railway vehicle (2) towards the ground computer (12), a range of positions (S₀) of the railway vehicle (2) determined by said onboard computer (10), the step for computing a range of positions (S_d) of the railway vehicle (2) also taking into account the range of positions (S₀) determined by said onboard computer (10).
2. The method according to claim 1, characterised in that the step for computing a range of positions (S_d) comprises a first phase in which the range of positions is taken to be equal to the range of positions (S₀) of the railway vehicle (2) determined by the onboard computer (10), and a second phase in which a front end (A_d) of the range of positions (S_d) is moved along the displacement direction of the railway vehicle (2) until an end of the occupied block (6) is attained, which is found at the front of the railway vehicle (2).
3. The method according to claim 2, characterised in that the front end (A_d) of the range of positions (S_d) is displaced during successive computing cycles of a predetermined duration (T) by a distance equal to the product of the speed of the railway vehicle (2) by the predetermined duration (T).
4. The method according to any of claims 1 to 3, characterised in that it further includes a step for computing, by the ground computer (12), a second range of positions (S_p) of the railway vehicle (2) from the range of positions (S₀) of the railway vehicle (2) determined by the onboard computer (10), the computing step including a first phase in which the computer (12) determines a front limiting position (A_max) which the railway vehicle (2) is not authorized to exceed, a second phase in which the second range of position (S_p) is taken equal to the range of positions (S₀) determined by the onboard computer (10), and a third phase in which a front end (A_p) of the second position (S_p) is displaced until the front limit (A_max) is attained.
5. The method according to claim 4, characterised in that the front end (A_p) of the second range of positions (S_p) is displaced during successive computing cycles of a predetermined duration (T) by a distance equal to the product of the speed of the railway vehicle (2) by the predetermined duration (T).
6. The method according to any of claims 3 or 5, wherein, if the speed of the vehicle is not available, the distance is equal to the product of the maximum speed of the railway vehicle (2) by the predetermined duration (T).
7. The method according to claims 2 and 4 in combination, characterised in that it includes a step for computing an auxiliary range (S_x) of the railway vehicle (2), the auxiliary range (S_x) being equal to an intersection of the first range of positions (S_d) and of the second range of positions (S_p).
8. A device (3) for computing a range of positions (S₀) of a railway vehicle (2) on a railway track (4), for applying a method according to any of claims 1 to 7.

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