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    • 专利摘要:
    The present invention relates to the field of geolocation by satellites and more particularly to a method of spot localization of a vehicle traveling on a constrained trajectory, implemented by a locating device comprising tachometer means (32), means for odometry (31), a group of at least one satellite reception receiver (42) and a synchronized time base on a satellite navigation system, the location device detecting the passage of the vehicle as close as possible to a position predetermined by exploiting the knowledge of the vehicle movement, by predicting the shape of a set of satellite separation signals at the predetermined position and by testing the agreement between the predicted signals and those received by the group of at least one satellite receiver, the movement of the vehicle being determined from data are provided by odometry and mapping means (36) of the path.
    公开号:FR3057348A1
    申请号:FR1601449
    申请日:2016-10-06
    公开日:2018-04-13
    发明作者:Marc Revol
    申请人:Thales SA；
    IPC主号:
    专利说明:

    057 348
    01449 ® FRENCH REPUBLIC
    NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:
    (to be used only for reproduction orders)
    ©) National registration number
    COURBEVOIE © Int Cl 8 : G 01 C21 / 00 (2017.01), G 01 C 22/00, 25/00, G 01 S 5/00, B 61 L 25/02
    A1 PATENT APPLICATION
    ©) Date of filing: 06.10.16. ©) Applicant (s): THALES Société anonyme - FR. ©) Priority: (© Inventor (s): REVOL MARC. ©) Date of public availability of the request: 13.04.18 Bulletin 18/15. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ©) Holder (s): THALES Société anonyme. related: ©) Extension request (s): ® Agent (s): MARKS & CLERK FRANCE Company in collective name.
    METHOD FOR THE PUNCTUAL LOCATION OF A VEHICLE MOVING ON A CONSTRAINED TRAJECTORY AND ASSOCIATED SYSTEM.
    FR 3 057 348 - A1 (LY) The present invention relates to the field of geolocation by satellites and more particularly a method of punctual location of a vehicle moving on a constrained trajectory, implemented by a location device comprising means of tachymetry (32), odometer means (31), a group of at least one receiver (42) for satellite mapping and a time base synchronized with a satellite mapping system, the location device detecting the passage of the vehicle as close as possible to a predetermined position by exploiting the knowledge of the movement of the vehicle, by predicting the shape of a set of satellite signaling signals at the predetermined position and by testing the agreement between the predicted signals and those received by the group of at least one satellite positioning receiver, the movement of the vehicle being determined based on data provided by the odometry means and a cartography (36) of the trajectory.
    METHOD FOR PUNCTUAL LOCATION OF A VEHICLE EVOLVING ON A CONSTRAINED PATH AND SYSTEM THEREOF
    The present invention relates to the field of geolocation by satellites. The invention relates more particularly to a method and a system for the punctual location of a vehicle operating on a constrained trajectory.
    The present invention applies to any means of locomotion traveling on a constrained road and aims to ensure punctual positioning of this means at different points in its trajectory.
    In mobile command and control systems such as trains, it is necessary to have a reference mark with two objectives, calculate the control curves precisely and safely and position the mobile. Indeed, if the train follows rails and therefore has only one degree of freedom, it is however necessary to give it a location on the axis of the track. Currently, this tracking calls for a punctual information transmission technology comprising two components, namely a fixed beacon (Eurobalise), placed on the track and an antenna on board the mobile. The ground beacon is passive and contains its location references in a memory. On the mobile, on board, there is the antenna which has two functions, on the one hand the emission of a radioidentification signal, (or RFID for “Radio Frequency / Dentification * according to the English terminology) which has for aim of transmitting energy to the beacon when the mobile passes over it and on the other hand the reception of the message sent by the beacon with the energy emitted by the mobile.
    The passage of a train over one of these beacons, therefore triggers the emission of a radio-identification signal, which is detected and dated by a positioning system, on board the train, and used to find out punctually the precise position of the train and thus readjust the on-board location means, the odometry.
    The disadvantage of this positioning system is that it constitutes a significant infrastructure load. Indeed, this system requires the installation of RFID tags approximately every two kilometers and once installed, these tags need to be maintained, which represents a high maintenance cost.
    There is also known a project to improve this positioning system using, among other things, a satellite positioning device (or GNSS for 8 Global Navigation Satellite System ”according to English terminology) on board the vehicle and providing a permanent and continuous location (only in position) as well as virtual beacons placed along the trajectory of the vehicle. The principle is simply to follow the position provided by the GNSS receiver and to detect the date of passage as close as possible to positions defined a priori (say, virtual beacons).
    In use linked to the railway sector, the location device is configured to trigger an 8 position top® equivalent to that of a Eurobalise, when the position provided by the location device passes as close as possible to the virtual beacon. This makes it possible to remain compatible with the physical beacon detection interfaces defined by the standards of the European train control system (or ETCS for 8 European Train Control System ”according to English terminology)
    A disadvantage of this system is that the radius of protection of the integrity of a GNSS positioning varies between 10m and 50m depending on the use or not of spatial augmentation systems such as differential GPS (or DGPS for 8 Differential Global Positioning System ”According to Anglo Saxon terminology) or SBAS (for 8 Satellite-Based Augmentation Systems® according to Anglo Saxon terminology), and according to the augmentation system (DGPS, SBAS, ...) considered. Such a protection radius makes it difficult to meet the integrity performance objectives imposed by standards which are less than 5m or even less, like localization capabilities based on RFID tags. In addition, the quality of the measurements can be degraded by the effect of propagation disturbances or local interference in the reception environment.
    Another disadvantage comes from the fact that the availability of positioning signals by satellites may not be sufficient in the case of vehicles operating on the ground, for reasons of masking the signals, or of unavailability of the satellite signals. Thus, the accuracy and integrity of location measurements can be significantly worse than that provided by a robust physical tag.
    An object of the invention is in particular to correct all or part of the drawbacks of the prior art of GNSS positioning by proposing a solution making it possible to readjust a location device on board a vehicle with a reference system not requiring a beacon physics placed on its trajectory.
    To this end, the subject of the invention is a method of punctual location of a vehicle moving on a constrained trajectory, said method being implemented by a location device comprising tachymetry means, odometry means, a group at least one satellite positioning receiver and a time base synchronized with a satellite positioning system, said location device detecting the passage of the vehicle as close as possible to a predetermined position by exploiting the knowledge of the movement of the vehicle, by predicting the shape of a set of satellite positioning signals at the predetermined position and by testing the agreement between the predicted signals and those received by the group of at least one satellite positioning receiver, the movement of the vehicle being determined from data provided by odometry means and a e trajectory mapping.
    According to one mode of implementation, the method comprises:
    a step of estimating an average date of passage of the vehicle as close as possible to the predetermined position, on the basis of the average current time, the average speed of the vehicle and the average distance between the current position of the vehicle and the position predetermined,
    - a step of estimating possible dates of passage of the vehicle as close as possible to the predetermined position, around said average date of passage, taking into account the uncertainties on the basis of time of the location device,
    - for each of the possible dates, a step of estimating the possible positions of the vehicle on the date considered taking into account the uncertainties of position and speed of the vehicle,
    a step of calculating, for each of the possible dates of passage of the vehicle as close as possible to the predetermined position and each of the possible positions of the vehicle, of all of the phases of the positioning signals associated with each possible position and expected on the date average,
    a step of spatial correlation of the received position signals with the expected position signals associated with each possible date and each possible position, the correlation of the signals being carried out taking into account, simultaneously, several received position signals.
    a step for detecting a maximum correlation, said maximum correlation indicating the date of passage closest to the predetermined position.
    The subject of the invention is also a device for punctual location of a vehicle moving on a constrained trajectory configured to implement the location method described above, said device comprising tachymetry means configured to deliver a signal representative of the speed of the vehicle, odometry means configured to deliver a signal representative of the movement of the vehicle, at least one location receiver configured to receive and process location signals by satellites, a time base synchronized to GNSS time via the receptor for the map.
    According to one embodiment, the point location device is configured to implement the point location method described above when the distance between the vehicle and a predetermined position is less than a predetermined value.
    Another object of the invention is a computer program product comprising computer readable instructions which, when executed on a processor, cause the processor to execute the method described above.
    The subject of the invention is also the use of the point location method of a vehicle operating on a constrained trajectory, previously described, by a point location device, as described above, in order to readjust the odometric means of said location device. on board the vehicle.
    Other particularities and advantages of the present invention will appear more clearly on reading the description below, given by way of illustration and not limitation, and made with reference to the appended drawings, in which:
    Figure 1 illustrates the relationship between the time correlation and the spatial correlation;
    - Figure 2 shows possible steps of the location method according to the invention;
    FIG. 3 illustrates an example of implementation of the prediction of the phases of the codes expected at the level of the group of possible positions of the vehicle as close as possible to a virtual beacon;
    - Figure 4 illustrates an example of implementation of the detection of the date of passage of the vehicle as close as possible to a virtual beacon;
    FIG. 5 illustrates the principle of multi-satellite correlation for a given virtual beacon position;
    FIG. 6 illustrates the principle of detecting the position and the date of passage as close as possible to a virtual beacon;
    FIG. 7 represents an example of a result obtained after quadratic summation of satellite spatial correlation functions at different incidence.
    Thereafter, a “predetermined position” or reference point, whose coordinates are known precisely, will be called a “virtual beacon”.
    Preferably but not limited to, the present invention finds its application in the railway sector for resetting the odometric measurements carried out on board the power train of a train. In general, the invention can be applied to any means of locomotion traveling on a constrained trajectory to ensure punctual positioning at different points of its trajectory. This can be the case, for example, in the maritime domain, for the positioning of ships in "navigation rails *, in the transport domain, for example, for the localization of public transport vehicle, for space navigation in fixed orbit, to ensure a system for verifying the passage of a vehicle to compulsory positions, etc.
    The point localization method according to the invention takes advantage of the fact that the vehicle which it is sought to locate is moving on a constrained trajectory whose route is known. According to one embodiment, the different points of this plot, or trajectory plan, can be saved in a memory area like a database. This database can allow the vehicle to reconstruct its trajectory. The geolocation of the vehicle is therefore limited to a search for one dimension, time. The reference points through which the vehicle will pass are known but the unknown is the date on which the vehicle will pass at these points.
    Thereafter, it will be assumed that in the vehicle that it is sought to locate is on board a location device comprising means for measuring the speed of movement of the vehicle as well as means for positioning by odometric measurements. The location device is therefore capable of estimating at all times the current position of the vehicle and the uncertainty of position along the curvilinear axis which is associated therewith as well as the current speed of the vehicle and an estimate of the error on the speed current.
    For example, in the railway sector, it is known that this type of odometric measurement quickly drifts, of the order of 5% to 10% of the distance traveled and therefore needs to be readjusted regularly in order to know the position. precise of the driving power of the train along its displacement.
    To readjust the position measurements of a vehicle moving along a well-defined trajectory, the method according to the invention uses virtual beacons positioned along the path of the vehicle in order to obtain the precise date of its passage at most near landmarks whose position is perfectly known. These beacons can be distributed regularly or not along the trajectory of the vehicle. According to a particular embodiment, the virtual beacons can be spaced about two kilometers apart. Each time as close as possible to a virtual beacon, the detected torque (date of passage, reference position) is integrated into the odometric measurements in order to correct their drift.
    Advantageously, the positioning of the vehicle is not carried out continuously but on an ad hoc basis. It is only carried out in the vicinity of the position of installation of the virtual beacons, when the vehicle passes near the position of the virtual beacons. It is not necessary to insure it outside these reference points.
    The point location method according to the invention consists in detecting the passage of a vehicle as close as possible to reference points, using a positioning system by satellites (or GNSS for “Global Navigation Satellite System”). according to Anglo-Saxon terminology), like the GPS, Galileo, Glonass or any other equivalent system, by exploiting the knowledge of the movement of the vehicle and by predicting the form of a set of satellite signaling signals in a range of positions around the predetermined position. The invention therefore realizes, in a punctual manner, a synchronization in time and in position between expected GNSS signals, predicted for the date of passage and the expected position of a virtual beacon from measurements carried out on board the vehicle with the signals. GNSS received using an on-board GNSS receiver. For this, it is assumed that the location device comprises at least one GNSS signal receiver for synchronizing its local time (current system time) with the time of the GNSS system. We consider an uncertainty over time of a few hundred nanoseconds. As a reminder, an uncertainty of 1ps corresponds to approximately 300m of uncertainty linked to time.
    Unlike a conventional method consisting in performing, by suitable filtering, a time synchronization of the satellite signals received by exploring the domain of propagation delays, corresponding to the domain of position uncertainty, the invention uses an approach based on a principle. “detection on the lookout® for GNSS signals, purely dedicated to detecting the passage of the vehicle at a reference position. The principle consists in predicting a date of passage of the vehicle at a particular point and in carrying out a synchronization in position by intercorrelation of the pseudo-random codes of the signals of satellite positioning signals.
    Figure 1 illustrates the equivalence between time synchronization by time correlation and position synchronization by spatial correlation.
    This figure presents a graphical representation, as a function of time, of a temporal correlation function 11 of the signal received from a satellite from positioning with the expected signal at an abscissa point X cpa and at a time of passage T cpa at closer to a virtual beacon. The support T cor r of this time correlation function corresponds to a chirp of code (term used in GNSS techniques to differentiate from a bit which is used to define a unit of information), ie 1ps for the GPS system. The maximum 110 of this time correlation function is obtained at the time of synchronization of the expected signal with the received signal. It indicates the date of passage closest to the virtual beacon.
    FIG. 1 also presents a graphical representation, as a function of the curvilinear abscissa, of a spatial correlation function 12 equivalent to the signal received from a satellite from positioning with the expected signal at an abscissa point X cpa and at a instant of passage T cpa as close as possible to a virtual beacon. The support X CO rr of this spatial correlation function corresponds to the projection of the temporal correlation support on the displacement axis. It can be given by the formula:
    Xcorr = C. T CO rr / COS (a)
    In which X CO rr represents the support of the spatial correlation function c represents the speed of light;
    Tcorr represents the support of the time correlation function;
    a represents the angle of incidence of the satellite signal relative to the direction of travel of the vehicle;
    io operator 8 . 8 represents the multiplied sign.
    The maximum 120 of this function corresponds to the abscissa of synchronization of the expected signal with the received signal, it indicates the position closest to the virtual beacon.
    FIG. 2 represents a flowchart illustrating possible steps of an example of implementation of the method of punctual location of a vehicle moving on a constrained trajectory according to the invention.
    The method may include a first step EtpO of estimating an average date of passage of the vehicle as close as possible to a predetermined position or virtual beacon. This date is estimated from the average current time, the average vehicle speed and the average distance between the current position of the vehicle and the predetermined position.
    In order to take account of the uncertainties on the time base of the receiver of the location device, a step Etp1 of estimation of several possible dates of passage of the vehicle as close as possible to the predetermined position can be carried out, for example, by a module of calculation of the localization device. These possible dates are estimated around said average date of passage closest to the predetermined position.
    A step Etp2 of estimating the range of possible positions of the vehicle at the average date of passage can then be implemented, for example by a module for calculating the location device, taking into account the uncertainties of position and speed of the vehicle. estimated at current time and extrapolated to the average date of passage of the vehicle closest to the next virtual beacon,
    During a step Etp3, a module for calculating the localization device estimates, for a sampling of positions covering the possible positions of the vehicle, all of the phases of the positioning signals associated with each possible position and expected on the average date of passing the vehicle as close as possible to the next virtual beacon,
    The method can then include a step Etp4 of spatial correlation of the location signals received by a GNSS receiver of the point location device with the predicted location signals associated with each possible position of the vehicle.
    The date of passage closest to the predetermined position is finally determined during a step Etp5 of detecting a maximum correlation, the latter indicating the date of passage closest to the predetermined position.
    These different stages will now be developed with reference to FIGS. 3 to 6.
    With reference to FIG. 3, throughout the movement of the vehicle, the on-board tachometer 32 and odometer means 31 supply the location device with signals representative of the speed and movement of the vehicle along its trajectory. From this data and as a function of the positions of the various beacons, a calculation module 35 of the location device evaluates the distance which separates the vehicle from the next virtual beacon. The position of the various virtual beacons on the curvilinear axis of the trajectory and the order in which these beacons will be crossed can, for example, be recorded in a memory area 34 of the location device. According to a variant implementation of the method, this information can be transmitted to the location device via a means of communication.
    Knowing the average speed of the vehicle, a calculation module 35 of the location device can extrapolate an average date Tp cpa of passage as close as possible to the next virtual beacon on its trajectory.
    A first problem arises because the local time 33 of the vehicle which it is sought to locate is not perfectly synchronized with the time of the GNSS system. For example, if we consider an offset of 1ps between the local clock 33 of the positioning receiver and the time base of the satellites of the GNSS system, this desynchronization generates a calculation error of the position of the vehicle by 300m. In order to take account of this uncertainty on the clock of the GNSS signal receiver, the uncertainty domain ATp cpa on the time of passage closest to the virtual beacon will be sampled. These different samples will correspond to different hypotheses of the date of reception of the GNSS signal in order to take into account different hypotheses of synchronization of the local clock 33 with the time base of the GNSS system.
    The uncertainty domain ATp cpa on the time of passage as close as possible to a virtual beacon can be determined for example using a model of the evolution of the system time error, that is to say of the local clock 33 of the receiver of the location device. This model can for example be stored in a memory area 37 of the location device.
    Several possible dates of passage of the vehicle are therefore estimated to be closest to the predetermined position. These possible passage dates are determined around the average date Tp cpa of passage closest to the virtual beacon considered. By way of illustration, the temporal uncertainty domain ATp cpa can for example be sampled by taking ten samples which corresponds, if we consider an uncertainty domain of 1 ps, to an assumption of synchronization to the nearest 0.1 ps.
    Another problem stems from the fact that the signal representative of the speed of the vehicle supplied by its tachymetry means is tainted with uncertainties just like the signal representative of the movement of the vehicle along its trajectory supplied by the odometric means between the position of the vehicle during the last registration of the odometric means and its current position. In addition, to estimate the average date Tp cpa of passing as close as possible to the next virtual beacon, the location device uses an average speed of the vehicle. This adds additional uncertainty about the average date of passing closest to the next virtual beacon. Indeed, this assumption assumes that the future average speed of the vehicle between the current position and the position of the next virtual beacon will be identical to the average speed between the position of the previous virtual beacon and the current position of the vehicle.
    Because of these uncertainties, at the average date predicted by the positioning device, the vehicle may not be at the position of the virtual beacon but either before or after this position. In order to take account of this error on the average date of passing as close as possible to the virtual beacon, the positioning device does not estimate a position but a framing of the position of the vehicle around the position of the virtual beacon, at the average date Tp cpa predicted. This spatial framework, or area of uncertainty, is a function of the uncertainties about the speed of the vehicle and its position when the average date of passage closest to the next beacon is extrapolated as well as the uncertainty about the future speed of the vehicle between the position at the time when said average date is extrapolated and the position of the next virtual beacon.
    As a remark, the calculation modules 35 stated may be the same module or separate modules.
    The positioning device therefore estimates for each of the possible dates of passage of the vehicle as close as possible to the predetermined position considered, during a step Etp2 of the point location process, a set of possible positions Be of the vehicle, around the position of the virtual beacon, expected on the average date Tp cpa predicted according to all the uncertainties. By way of nonlimiting example, one can consider a domain of uncertainty in curvilinear position APb cpa of approximately 500m around the virtual beacon. In the time domain, this translates into an uncertainty of around 5s for a vehicle traveling at 100m / s (360 km / h) on its curvilinear abscissa.
    The area of uncertainty in the curvilinear position APb cpa can be determined for example using a model of evolution of the error of the speed of the vehicle that it is sought to locate. This model can for example be stored in a memory area 38 of the location device.
    The number of possible positions Be of the vehicle and their locations can be defined so as to frame the domain of uncertainty in position according to the curvilinear abscissa of the trajectory and so as to sufficiently finely sample the domain of spatial correlation. The spacing between the possible expected positions can be chosen so that the spatial correlation samples are separated by less than a code chip (i.e. 300m for the C / A code of the GPS system), so that they can be reconstructed by interpolation the precise position of the maximum of the correlation function on the trajectory of the vehicle. As a reminder, the acquisition code C / A (for “Coarse Acquisition 8 or coarse acquisition) is a digital signal composed of 1023 chips (term used in GNSS techniques to differentiate from a bit which is used to define a unit of information) and which is repeated every millisecond.
    As an illustration, we can choose a spacing of 0.2 chirp (60m for the GPS system) around the position of the virtual beacon considered. If we consider an area of spatial uncertainty of 500m around a virtual beacon, this implies to calculate in parallel 500/60 or approximately 83 virtual positions. Each position is delayed or advanced by approximately k.0,2.cos (a) ps relative to the median expected date of passage (k representing the index of the possible position relative to the location of the virtual beacon, a representing the angle of incidence of the signal with respect to the direction of movement at each position and “.” representing the multiplicative operator).
    Advantageously, the uncertainty on the date of passage of the vehicle at a given reference point is transformed into an uncertainty in position around the virtual beacon at the estimated time of passage.
    Once the possible dates of passage of the vehicle as close as possible to the predetermined position have been determined and the possible positions Be of the vehicle for each possible date around the predicted average date Tpcpa, it is possible to predetermine the Pdee code phases of each satellite received at each location of the possible positions of the vehicle and for each of the possible dates of passage as close as possible to the virtual beacon, by means of the estimation of the distances between each satellite from the map and each possible position of the vehicle. The position of the visible map satellites can be calculated using the ephemeris. Thus, for each of the possible positions of the vehicle on each of the possible dates, and for each of the visible positioning satellites at each possible position of the vehicle, a module for calculating the positioning device estimates, during a step Etp3, all of the satellite signals from the expected satellite, as they will be at the position considered and at the average date of passage of the vehicle at the level of the virtual beacon. Since the signals from the landmarks are deterministic, it is possible to anticipate the sequence of the signal (code delay, position of the satellites, Doppler channel) for each of the satellites which will be visible at the position considered and at the average date of passage of the vehicle. predicted. These various signals can be recorded in a memory zone of the localization device in order to prepare it to receive these signals from the satellites of the positioning system when the vehicle approaches the considered virtual beacon. The generation of local satellite codes, at current time, can, for example, be carried out using digitally controlled oscillators (or NCO for “Numerical Controlled Oscillator * according to English terminology) controlled from the code phase expected at time Tp cpa , for each of the signals received on each of the possible positions of the vehicle on the predicted date.
    According to a feature of the invention, the detection of the position of the vehicle is effected by a "detection on the lookout * for signals from the position. As stated previously, all of the expected map signals, for each of the possible positions of the vehicle at the predicted average date and for each of the visible map satellites at each of these possible positions are recorded in a memory area and are compared. signals received by the GNSS receiver from the positioning device when the vehicle is moving along its path. All the signals from the visible satellites of the vehicle having been prepared with the correct offset, there will only be one point in the trajectory of the vehicle for which all will be synchronized at the same time. Knowing the position of this point will allow the tracking device on board the vehicle to be reset.
    The group of possible positions of the vehicle for each of the possible dates of passage as close as possible to the virtual beacon considered will make it possible to sample several functions of curvilinear correlation between the GNSS signals received by the GNSS receiver (s) of the location device during the passage of the vehicle in these areas of spatial and temporal uncertainty, and the satellite signals expected at each of the possible positions of the vehicle, and for each of the possible dates of passage as close as possible to the virtual beacon considered.
    îo FIG. 4 illustrates an example of implementation of the detection of the date of passage of the vehicle as close as possible to a virtual beacon. In order not to overload the figure, we consider only one possible date of passage closest to the virtual beacon. The principle consists in carrying out a continuous adapted filtering between the signals of satellite positioning received by a GNSS receiver of the locating device and a set of local codes of visible satellites, synchronized on the phases of the code and the carrier expected from the signals of positioning on the possible date of passage as close as possible to the virtual beacon considered and for each of the possible positions of the vehicle.
    For each of the possible positions Be of the vehicle, a calculation module 35 of the punctual location device generates, at the current time t, the expected position signals Ci (t) calibrated on the predicted phase on the possible date of passage of the vehicle as close as possible to the virtual beacon considered. For this, the calculation module 35 can use, for each of the possible positions, a time base 33 synchronized with the time of the GNSS system as well as the results of calculation of the Pd code phases of each of the GNSS signals of the satellites visible at the level of the possible position considered. These results can be provided by a calculation module, as shown in FIG. 4 or can be read in a memory area of the device.
    If we consider the general case in which several possible dates are predicted, the operations presented above are carried out in parallel for each of the possible dates of passage closest to the virtual beacon considered.
    For each of the possible dates and at each possible position of the vehicle, the expected position signals {Ci (t)} b e associated with the possible date of passage as close as possible to the virtual beacon considered and each visible position satellite is then correlated with the SISgnss landing signals received by the GNSS receiver 42 from the positioning device during the movement of the vehicle along its trajectory during an Etp4 step of spatial correlation. Advantageously, the correlation of the positioning signals is a global correlation taking into account, simultaneously, the signals received from several visible positioning satellites from the possible position considered. According to a preferred mode of implementation, the correlation uses the signals of all the visible satellites of the visible position. This multisatellite correlation is possible because, the vehicle moving on a constrained trajectory, the research is done according to only one dimension. It is known that when the vehicle passes at the level of the position of the virtual beacon, all the signals from the visible satellite of the satellites will present the maximum of the correlation function at the same time. The advantage of this global correlation is that by accumulating the signals, the method gains in precision and therefore in robustness.
    Another advantage of this global spatial correlation is that it makes it possible to benefit from better robustness with respect to specular multiple paths compared to a monosatellite correlation.
    For each of the possible positions of the vehicle and for each of the possible dates of passage as close as possible to the virtual beacon, the output signals from the correlators are summed in a non-coherent manner. In fact, the coherence of the carrier phase not being ensured with sufficient precision, due to the vagaries of propagation (for example due to ionospheric delays, multiple paths, etc.), summation should not be carried out. consistent correlation outputs of different satellites in the same position. The residual errors on the code, after correction of the delays from the models being low compared to the correlation support, they do not significantly impact the value of the correlation function and can be summed quadratically.
    By way of illustration, FIG. 5 represents an example of possible implementation of the simultaneous multisatellite correlation processing for a possible position of the vehicle Be, (the index i representing the rank of the position) at a possible date of passage as close as possible a virtual tag. The processing is applied to each of the signals received by the receiver 42 of the location device from the satellites taken into account and visible from the possible position considered. These satellite signals will provide as many spatial correlation functions along the curvilinear movement of the vehicle as of the visible map satellite taken into account.
    The code phases of the signals expected from each visible satellite taken into account the possible position considered, estimated during step Etp3 of the location method and for example stored in a memory area 51, can be generated by digitally controlled oscillators 54 synchronized by a time base or local clock 33. The output signals of these oscillators 54 are correlated with the satellite signals received by the GNSS receiver 42 of the point location device using correlators 55. The correlation functions thus obtained for the different visible satellites from the possible position considered are then accumulated quadratically.
    With reference to FIG. 4, at the end of the multisatellite correlation, we obtain several global correlation functions {rsc (0, t)} Be, calculated at the different possible positions Be of the vehicle and at the different possible dates in the domain of spatial and temporal search for the position of the virtual beacon.
    As the vehicle moves, a localization device calculation module tracks the progress of each correlation function in order to detect its maximum. The search for the instantaneous maximum of each correlation function along the abscissa is carried out at each instant of calculation of the correlation functions for each possible position of the vehicle and each possible date from the moment when the distance between the vehicle and the next virtual beacon is less than a predetermined value. According to one embodiment, the correlation functions can be calculated from the moment the vehicle enters the area of spatial determination of the position of the virtual beacon.
    According to a particular feature of the method according to the invention, the location device does not search for the maximum of the satellite-to-satellite correlation function but performs a massive multi-satellite correlation, that is to say a simultaneous correlation of all the signals of the positioning of the visible satellites for each of the possible positions of the vehicle and each of the possible dates of passage closest to the virtual beacon. A calculation module of the localization device carries out in parallel several suitable filters corresponding to the signals to be received at the different possible positions of the vehicle with respect to the virtual beacon, calculated for each possible date expected on the plane of the trajectory of the vehicle.
    The location of the vehicle position on the predicted date is carried out by detecting the maximum-maximorum of power of all the global correlation functions on the different possible positions surrounding the location of the virtual beacon and the different possible dates surrounding the date predicted Tp cpa , during a step Etp5 of the point localization process. After detection of this maximummaximorum the calculation module has access to the date T max of passage closest to the virtual beacon considered and can calculate, by interpolation, the precise position X max of the maximum of correlation according to the curvilinear abscissa, from time correlation maxima obtained at the various expected positions, distributed along the trajectory.
    By way of illustration, FIG. 6 presents an example of the result obtained by applying the method according to the invention and illustrates the principle of determining the position and the date of passage as close as possible to a virtual beacon. This figure represents the evolution of the multi-satellite correlation functions 61 as a function of time for each possible position of the vehicle and for the possible date corresponding to the best hypothesis of synchronization of the local clock 33 of the positioning device with the time base of the GNSS system.
    It is assumed that for each possible position of the vehicle on the possible date considered to pass as close as possible to the position X cpa of the virtual beacon, a module for calculating the positioning device has predetermined the expected positioning signals. When the vehicle will enter the search area for the position of the virtual beacon, the location device will implement the point location process. As the vehicle progresses, each correlation function 61, calculated at the various possible positions of the vehicle will increase, go through an instantaneous maximum 610 and then decrease. The localization device is pre-synchronized with the GNSS signal expected at each possible position and it is the movement of the vehicle which changes the correlation function.
    Among all these correlation points, only one is perfectly suited and reaches a maximum maximorum 615. It indicates the point for which the GNSS signal is perfectly synchronized with the predicted signal. For the other points, the GNSS signals received are offset from the expected signals and therefore pass through an instantaneous maximum 610 which is not the maximum maximorum 615.
    Once the maximum maximorum has been detected, a module for calculating the positioning device can deduce the date of passage T max closest to the virtual tag considered as well as the curvilinear abscissa Xmax closest to this tag. Indeed, we observe a maximum 615 of the correlation function on a position which is not the predicted position, which means that the assumptions which had been made at the start were not exact. The position difference which is observed corresponds to the initial position error and to the extrapolation error and allows the punctual localization device to readjust the odometry means on board the vehicle.
    It should be noted that the calculation module having to follow all the correlation functions in order to detect the maximum maximorum 615, this detection is not carried out at current time but is carried out once the search field of the virtual tag has been crossed and therefore once the X max curvilinear abscissa closest to the considered virtual tag passed. The registration of the odometry means on board the vehicle is therefore not carried out when passing through the virtual beacon but a posteriori.
    The area of spatial correlation of the satellite signals from being around 300m (for the GPS system) and depending on the incidence of GNSS signals, the positioning device can reconstruct the precise position of the maximum correlation according to the curvilinear abscissa by interpolation of the levels of correlations estimated on the set of possible positions Be of the vehicle on the date of passage closest to the virtual beacon.
    The duration of the correlation function scan is a function of the vehicle speed and direction of travel. As an example, if we consider a vehicle moving at 100m / s, for the GPS system with the code C / A, the minimum duration is 300/100 or 3s for a satellite in the axis of movement of the vehicle (with maximum contrast on the correlation function). This duration increases in 1 / cos (a) of the angle of incidence a of the satellite of positioning with respect to the displacement, îo thereby reducing the contrast of the correlation function.
    The spatial correlation domain therefore depends on the direction of incidence of the GNSS signal relative to the axis of movement of the vehicle. Since the signals “orthogonal” to displacement cannot be used to lift the indeterminacy of position, we can possibly define the equivalent of a coefficient of weakening of the precision (or DOP for “Dilution Of Precision” according to the English terminology). ) to assess the ability to use the virtual beacon as an "absolute reference" taking into account the geometry of the satellites.
    As a reminder, for a standard resolution in the three dimensions, we use for this a matrix of the cosines guiding the angles of arrival, which in fact enter into the system of equation to be solved.
    In the case of a one-dimensional resolution, an equivalent rigorous criterion can be constructed. This criterion can take the form of:
    DOP = 1 / N Zi1 / cos (a0
    In which: DOP represents the equivalent criterion,
    N represents the number of positioning satellites in view, a, represents the angle of arrival of the i th satellite, i being an index varying from 1 to N.
    It is for example possible to limit the taking into account of the satellites to those which have an angle of incidence relative to the direction of movement of less than 60 °, which corresponds to a maximum elongation of the correlation support by a factor of 2.
    By way of illustration, FIG. 7 represents an example of the result obtained after quadratic summation of satellite spatial correlation functions at different incidences. The curves 71 to 73 are respectively graphical representations of correlation functions for an angle of incidence of the satellite signal relative to the direction of movement of 60 °, 45 ° and 30 °. Curve 74 is the graphical representation of the cumulative satellite correlation functions.
    According to a particular mode of implementation, the coherent integration time can be chosen between approximately 10 ms and approximately 20 ms, that is to say a temporal sampling of approximately 100 Hz. If we consider a vehicle moving at 100m / s, this sampling leads to an uncertainty of about 1m which is negligible in front of the correlation support (as a reminder the correlation support for the C / A code of the GPS system is about 300m).
    It is assumed that the standard signal-to-noise ratio of a GPS signal, in a 1 Hz band of noise, is 42 dB / Hz. If we consider a coherent integration time of 20ms (i.e. 50Hz of noise bandwidth), the noise level is multiplied by 50, i.e. a reduction in the signal to noise ratio (CN0) equal to 10log (50) or 17 dB . In addition, the non-coherent accumulations of the correlation functions of the Nsat satellites at the maximum point of the correlation function adds a term equal to 10.log.N sa t, N sa t representing the number of visible map satellites considered.
    The signal to noise ratio is therefore of the order of 42-17 + 10.log.Nsat or 25dB + 10.log.N sat which leads to uncertainty about the position resolution of the order of meter (once the axes with unfavorable views have been eliminated). This uncertainty is to be compared with errors of several tens of meters from a standard positioning.
    According to another mode of implementation, the correlation functions can be weighted by taking into account the axes with a geometric view. Advantageously, this makes it possible to strengthen the signal to noise ratio by 5.log (N sa t), Nsat representing the number of satellites visible from the possible position considered, compared to a conventional GNSS tracking and thus providing better sensitivity and better precision on the date and position of the abscissa for detecting the maximum correlation.
    According to an implementation mode, the propagation errors can be corrected before the summation.
    The correlation functions are not all centered exactly around the same instant of passage at maximum power, the synchronization differences between received satellite signals (due in particular to satellite clocks, delays in ionospheric and tropospheric propagation, multiple paths ... ) causing errors in the position of the spatial correlation function. These differences are of the order, at most of several tens of nanoseconds. If we consider a spread of 200ns (i.e. 60m on pseudo-distances) and a vehicle moving at around 100m / s, this results in a spread of the positions of the correlation maxima between satellites, obtained by scanning at vehicle speed , over a range of 30/100, i.e. 0.3 s.
    To compensate for the effect of this spreading, and therefore the maximum passage determination noise, the expected distances from the satellites can be corrected, when generating local codes, using the available error models (model d 'clock error, tropospheric & ionospheric error models ...) to reduce them to a few meters, excluding multiple paths and interference. These models can for example be supplied by an on-board GNSS receiver or via a support link.
    The punctual localization method according to the invention therefore relies on the detection of virtual beacons placed on the path of the vehicle based on a satellite satellite map produced autonomously on board the vehicle, and without physical infrastructure on the path of the vehicle.
    Advantageously, this localization method makes it possible to emulate with a GNSS receiver a detection of passage very similar to what a physical beacon allows, using for example the RFID technique, but without requiring costly infrastructures to install and maintain.
    For example, in a use in the railway sector, in order to readjust the on-board localization device on board the power train, this punctual localization process makes it possible to remain compatible with ETCS operating standards relating to the use of beacons RFID physical.
    In addition, the duration of exposure of the search function being limited to the duration of passage of the vehicle near the virtual beacons, the risks of non-integrity of the GNSS signal are reduced, compared to a conventional operation requiring continuous tracking. satellite signals.
    At the level of certain virtual beacons, the number of visible map satellites may not be sufficient to estimate a position, in this case the location device abandons the location of the vehicle at this virtual beacon. The registration of odometric means is not carried out and will be carried out at the level of the following virtual beacon. In order to take account of the fact that the registration has not taken place and therefore of the fact that the error to be corrected will be greater, the positioning device will consider a larger area of spatial uncertainty. It will do the same for the uncertainty of synchronization to take into account the evolution of the error of synchronization of the local clock 33 of the GNSS receiver with the time base of the satellites of the satellites.
    The present invention also relates to a point location device for a vehicle moving on a constrained trajectory configured to implement the point location process described above and to be taken on board the vehicle to be located.
    This device comprises means of tachometer means 32 configured to deliver a signal representative of the speed of the vehicle as well as odometry means 31 configured to deliver a signal representative of the movement of the vehicle. The device comprises at least one positioning receiver 42 configured to receive and process positioning signals by satellites. The device comprises a time base 33 synchronized with GNSS time via the location receiver 42. The device also comprises one or more calculation modules 35. This group of at least one calculation module 35 can be or include one or more microprocessors, processors, computers or any other equivalent means programmed in a timely manner.
    Another object of the present invention is a computer program product comprising instructions readable by a computer or any equivalent type of computer device which, when executed on a processor, cause the processor to execute the method of localizing point a vehicle operating on a constrained trajectory as described previously.
    权利要求:
    Claims (6)
    [1" id="c-fr-0001]
    1. A method of punctual location of a vehicle moving on a constrained trajectory, said method being implemented by a location device comprising tachymetry means (32), odometry means (31), a group of at least at least one satellite mapping receiver (42) and a time base synchronized with a satellite mapping system, said method being characterized in that said tracking device detects the passage of the vehicle as close as possible to a predetermined position by exploiting knowledge of the movement of the vehicle, by predicting the shape of a set of satellite positioning signals at the predetermined position and by testing the agreement between the predicted signals and those received by the group of at least one positioning receiver by satellites, the displacement of the vehicle being determined from data supplied by the means odometric data (31) and a cartography (36) of the trajectory.
    [2" id="c-fr-0002]
    2. Method according to the preceding claim comprising:
    a step (EtpO) of estimating an average date of passage of the vehicle as close as possible to the predetermined position, from the average current time, the average speed of the vehicle and the average distance between the current position of the vehicle and the predetermined position,
    - a step (Etp1) of estimating possible dates of passage of the vehicle as close as possible to the predetermined position, around said average date of passage, taking into account the uncertainties on the basis of time of the location device,
    - for each of the possible dates, a step (Etp2) of estimating the possible positions of the vehicle on the date considered, taking into account the position and speed uncertainties of the vehicle,
    - a step (Etp3) of calculation, for each of the possible dates of passage of the vehicle as close as possible to the predetermined position and each of the possible positions of the vehicle, of all of the phases of the signals of positioning associated with each possible and expected position on the average date,
    a step (Etp4) of spatial correlation of the received position signals with the expected position signals associated with each possible date and each possible position, the correlation of the signals being carried out by taking into account, simultaneously, several received position signals.
    a step (Etp5) of detecting a maximum correlation, said maximum correlation indicating the date of passage closest to the predetermined position.
    [3" id="c-fr-0003]
    3. device for punctual location of a vehicle moving on a constrained trajectory configured to implement the location method according to one of the preceding claims, characterized in that it comprises tachymetry means (32) configured to deliver a signal representative of vehicle speed, odometry means (31) configured to deliver a signal representative of the movement of the vehicle, at least one positioning receiver (42) configured to receive and process signals from positioning by satellites, a time base ( 33) synchronized with GNSS time via the location receiver (42).
    [4" id="c-fr-0004]
    4. Point location device according to the preceding claim wherein said device is configured to implement the point location method according to one of claims 1 or 2 when the distance between the vehicle and a predetermined position is less than a predetermined value.
    [5" id="c-fr-0005]
    5. A computer program product comprising computer readable instructions which, when executed on a processor, cause the processor to execute a method according to one of claims 1 or 2.
    [6" id="c-fr-0006]
    6. Use of the point-in-time location method of a vehicle moving on a constrained trajectory according to one of claims 1 or 2, by
    5 a point localization device according to one of claims 3 or
    4 in order to readjust the odometric means of said localization device on board the vehicle.
    1/6
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    同族专利:
    公开号 | 公开日
    EP3306272A1|2018-04-11|
    FR3057348B1|2019-07-19|
    US20180100934A1|2018-04-12|
    EP3306272B1|2021-02-24|
    US10481276B2|2019-11-19|
    ES2869303T3|2021-10-25|
    PT3306272T|2021-05-05|
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    法律状态:
    2017-09-29| PLFP| Fee payment|Year of fee payment: 2 |
    2018-04-13| PLSC| Publication of the preliminary search report|Effective date: 20180413 |
    2018-09-28| PLFP| Fee payment|Year of fee payment: 3 |
    2019-09-27| PLFP| Fee payment|Year of fee payment: 4 |
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    优先权:
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    FR1601449A|FR3057348B1|2016-10-06|2016-10-06|METHOD OF LOCALLY LOCATING A VEHICLE EVOLVING ON A CONSTANT TRACK AND ASSOCIATED SYSTEM|
    FR1601449|2016-10-06|FR1601449A| FR3057348B1|2016-10-06|2016-10-06|METHOD OF LOCALLY LOCATING A VEHICLE EVOLVING ON A CONSTANT TRACK AND ASSOCIATED SYSTEM|
    US15/726,292| US10481276B2|2016-10-06|2017-10-05|Point location method for a vehicle moving on a constrained trajectory and associated system|
    ES17194964T| ES2869303T3|2016-10-06|2017-10-05|Point location procedure for a vehicle moving on a restricted path and associated system|
    EP17194964.7A| EP3306272B1|2016-10-06|2017-10-05|Method for momentary location of a vehicle travelling on a limited path and associated system|
    PT171949647T| PT3306272T|2016-10-06|2017-10-05|Method for momentary location of a vehicle travelling on a limited path and associated system|
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