FR2873480A1 - Vehicle e.g. heavy vehicle, speed monitoring system, has Doppler radar calculating speed using received signals, and category selection unit selecting vehicle category based on vehicle profile derived from distance between vehicle and radar - Google Patents

Abstract

The system has a bi-frequency Doppler radar (2) calculating a vehicle speed using signals received by a transmission and reception antenna (3) associated to a viewing angle (C) covering a part of a traffic lane. A profile determination unit (6) determines profile of each of vehicles from a distance between the vehicle and the radar. A category selection unit (7) selects a category for each vehicle based on the determined profile. An independent claim is also included for a method for monitoring vehicles moving along a path.

Description

METHOD AND SYSTEM FOR MONITORING VEHICLES IN

MOVEMENT

  The present invention relates to the field of monitoring vehicles traveling on a taxiway.

  This monitoring generally comprises, on the one hand, at least the measurement of the speed of vehicles using devices such as a radar, a laser or a pair of pneumatic sensors located in the roadway. On the other hand, it includes, in the case of the demonstration of a violation relating for example to the exceeding of a maximum authorized speed, the triggering of a camera to provide at least one image of the vehicle in violation. The image or images thus obtained provide a representation of the license plate and possibly a representation of the driver's face. They are then used for the identification of the vehicle and the driver, as well as for the establishment of the statement of offense.

  The radar, associated with a field of view centered around a line of sight, is generally arranged at the edge of the road or in height, so that the angle between the trajectory of the vehicles and the line of sight of the radar is of the order of 20 to 25 degrees. It measures the projection on the line of sight of the speed of a vehicle present in its field of view.

  There are different categories of vehicles, which are divided mainly according to their weight and / or their size. These categories include, for example, motorcycles, light vehicles, vehicles with caravans, cars without a license, trucks that can be divided into several subcategories, and so on. Vehicle monitoring may need to be adapted to the category of vehicles. For example, trucks are limited, on certain sections of road presenting a strong inclination, with a maximum speed which is lower than the maximum speed authorized for the other vehicles circulating on this section of road.

  Thus it is interesting to be able to determine the category of vehicles 30 present in the field of view of a radar, and whose speed is calculated using said radar, so as to be able in particular to determine in real time whether it is in offense or not.

  In a case of a section of road as indicated above with a maximum authorized speed different according to whether the vehicle is a truck or not, if means are not available to determine the category of the vehicle, either the radar systematically maximum speed equal to that allowed by the trucks, and in this case many light vehicles will be wrongly identified as infringement. It is only when an operator analyzes the image representing the vehicle that he can stop the establishment of the statement of offense for these vehicles. However, this means a waste of images, speed data, etc. stored unnecessarily. Either the radar is set systematically at a maximum speed equal to that allowed for vehicles other than trucks, and in this case, we can not identify the trucks in violation, while excessive speed of a truck on this type stump is very dangerous.

  US 6,614,536 (Doemens et al.) Discloses a device for simultaneously measuring the speed and profile of moving vehicles. This device comprises, with reference to Figure 1 of the document, two ramps of each 32 CMOS sensors, 1 meter apart from each other, arranged above the vehicles and perpendicular to the road. The device further comprises a light source, for example laser diodes. After a light emission, each sensor of a ramp analyzes the light signals returned by a vehicle traveling under the ramp, and deduces a distance between the sensor and the vehicle as a function of the light intensity received at two determined times. This establishes a cross section of the vehicle, that is to say a section perpendicular to the road. By combining several cuts, a profile of the vehicle is established. The speed is determined from the time elapsed between the detection of a profile by the first ramp and the detection of the same profile by the second ramp.

  This device however has a number of disadvantages. It requires an installation of ramps above the track, which is not always easy especially when the road has several lanes. On the other hand, it is necessary that the ramp is fixed securely, that it resists wind gusts etc, which is not compatible with a traveling use of the device. And the latter is not compatible with discreet vehicle monitoring. Indeed, the drivers of the vehicles are warned of the surveillance by the presence of the ramps.

  Other techniques, for example that described in the document US 2003/0189500 (Lim), use, to determine the category of the vehicles, digital treatments on the captured images in order to measure the width of the tires and the distance between the tires of the vehicle. 'a vehicle.

  The present invention aims to propose a system and a method of monitoring road traffic to define the category of vehicles traveling on a track and simple to implement.

  For this purpose, according to a first aspect, the invention provides a vehicle monitoring system moving along a path, and which comprises a Doppler radar. This radar comprises a generator of successive pulses at two frequencies and a transmitting and receiving antenna associated with a field of view. The field of view covers part of the track. The radar is adapted to measure, at times of determined measurements, the signals received by the antenna and originating from the reflection of the pulses emitted by the antenna and to calculate, from said signals, the speed of the vehicles located in the field of aim and the distance between these vehicles and the radar.

  The system according to the invention further comprises profile determination means for determining a profile of each of the vehicles from the distances between the vehicle and the radar calculated by said radar during several successive measurement instants.

  The system according to the invention also comprises category definition means adapted to select a category for each vehicle from predetermined categories, according to the profile determined for this vehicle.

  Thus a system according to the invention uses the same signals to define the category of a vehicle as those used to measure the speed in a two-frequency radar of known technology.

  Such a system can be easily transported and installed quickly in different successive locations. It also allows discreet surveillance of vehicles because it is much less identifiable than a ramp disposed above the road, as described in the prior art.

  According to a second object, the invention proposes a method for monitoring vehicles moving along a track part of which is included in a field of view of a Doppler effect radar comprising a generator of successive pulses at two frequencies. and a transmitting and receiving antenna associated with the field of view. The method according to the invention comprises the following steps: the signals originating from the reflection of the pulses emitted by said antenna and received by this antenna are measured at times of determined measurements, and the speed of the vehicles situated in said field of view and the distance between these vehicles and the radar are calculated from said signals; a profile of each of said vehicles is determined from the distances between said vehicle and the radar calculated by the radar during several measurement instants; - A category for each of said vehicles is selected from predetermined categories, according to the profile determined for each vehicle.

  Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the accompanying drawings, in which: - Figure 1 shows an embodiment of the invention; - Figure 2 shows on the same reference a heavy truck profile and a light vehicle profile, determined according to the present invention; - Figures 3a, 3b and 3c show different profiles of heavy trucks determined according to the present invention.

  In Figure 1 is shown a system 1 according to the invention installed on the edge of a road comprising at least one traffic lane Vc; rc. The system 1 comprises a 2-frequency radar Doppler effect whose technology is known. The radar 2 is for example similar to that described in the document EP 0 933 648. The radar 2 is associated with a field of view C centered on a line of sight U of the radar 2. The field C has a width of about 5 degrees and corresponds to a beam of waves emitted by a transmitting and receiving antenna 3 of the radar 2. The line of sight U is at an angle of 20 to 25 degrees with the direction of the Vcirc. The field of view C projects mainly in a substantially elliptical surface on the Vc; rc track and has a larger diameter of about 2 meters.

  In an advantageous embodiment, the antenna 3 of the radar 2 is disposed overhanging the track, so that the parasitic reflections of the transmitted beam are reduced. Indeed, the vehicle wheels are generating stray lines in the spectrum of the received signal.

  In the embodiment shown, the antenna 3 is disposed on a mast M at a height Kant relative to the road.

  The radar 2 comprises a pulse generator 4 adapted to emit a pulse signal and to regularly switch the frequency of the signal emitted by the antenna 3, between a value f1 and a value f2. In the embodiment described here, for example, f1 = f0 + AF / 2 and f2 = f0 - AF / 2, with f0 = 24.125 GigaHertz (GHz) and AF = 800 kilohertz (kHz). The frequency signal f1, respectively f2, is transmitted for a duration of one microsecond (1 ps) before being switched to the frequency signal f2, respectively f1. The successive transmission of a signal to f1 and a signal to f2 constitute a transmission cycle (fi, f2).

  Each vehicle traversing the field of view during its path on the Vc; rc channel, respectively give rise to reflected signals picked up by the antenna 3.

  The radar 2 comprises inter alia signal processing means 5 operating on the signals emitted by the antenna 3 and on the signals received by the antenna originating from the reflection of the signals transmitted on the vehicles crossing the radar field of view C 2. These signal processing means 5 make it possible to determine the speed of these vehicles and the distance, on the line of sight U, respectively separating them from the radar 2.

  In the embodiment considered, the signal processing means 5 are further adapted to calculate the interdistance value D relative to a vehicle V1. This interdistance value consists of the distance between this vehicle V1 traveling on the track Vc; rc and situated in the field of view, and the vehicle V2 preceding it on this same track Vc; rc and for which the speed has previously been calculated by the signal processing means 5. The interdistance calculated by multiplying the last calculated speed relative to the vehicle V2, by the time elapsed between the instant corresponding to this last velocity measurement and the moment corresponding to the first velocity measurement relative to the vehicle VI.

  The system 1 further comprises a profiling module 6 operating from data provided by the signal processing means 5.

  The system 1 comprises a category definition module 7 operating in particular from data provided by the profile determination module 6 and which is associated with a memory area 8 storing data relating for example to 3 predetermined vehicle categories: vehicle light weight (category C1), vehicle with caravan (category C2), heavy weight (category C3). In the embodiment described, the memory area 8 stores surface limit values SI, S2 and S3.

  The system 1 further comprises an offense determination block 9, associated with a memory zone 10 storing in particular maximum authorized speeds (Vimax, V2max and V3max respectively) and minimum allowed interdistances between vehicles (D1max, respectively D2max and D3max ) for each category of vehicles (Cl, respectively C2 and C3).

  The offense determination block 9 is further adapted to constitute parts of the statement of offense to be established when a vehicle has been detected in violation, and to store them in the memory zone 10.

  The system 1 also includes a camera 11 whose field of view is suitable for photographing a vehicle located in the field of view C of the radar 2. The field of view is such that it allows the reading of the license plate of the vehicle. In the embodiment, the camera 11 is a digital apparatus having a memory for storing the captured digital images. It is possibly equipped with a flash allowing the illumination of the scene during the shooting.

  The offense determination block 9 is adapted to suppress under certain conditions, explained below, images stored in the camera 11.

  Furthermore, the system 1 comprises a counting module 12 comprising three counters each adapted to count the number of vehicles of a respective category among the categories Cl, C2 and C3 flowing on the see Vc; rc and crossing the field of view C during a previously defined observation period. Counters are zeroed at the beginning of the observation period.

  The calculation of the speed of a vehicle is carried out by determining in a known manner the Doppler frequency generated by each vehicle present in the field of view C. In the embodiment considered, the signals received by the antenna 3 and corresponding signals in frequency and phase to the transmitted signals, are combined in the signal processing means 5, to provide a signal whose frequency is equal to the offset between the frequency of the reflected signal and that of the transmitted signal. This Doppler frequency fD is representative of the speed of the vehicle at the origin of the reflections. Indeed, it is equal to 2 * Vu / A, where VU is the projection of the velocity vector of the vehicle on the line of sight U and A is the wavelength of the emitted signal. We deduce from it Vu, then the velocity V of the vehicle equal to Vulcosa.

  The signal processing means 5 are adapted to process the signals reflected by a vehicle, so as to extract, in addition to the speed, the associated distance value. This is calculated from the phase differences between reflected signals and signals emitted alternately at f1 and f2.

  If a single frequency equal to f0 of transmitted signal was used, a distance value ranging from 0 to about 0.6 centimeters would be obtained (see EP 0 933 648). The fact of not using a single frequency f0 but the two frequencies f1 and f2 makes it possible to obtain an exact distance measurement given the configuration in which the measurements are made (indeed the distance value obtained is in a range of from 0 to 150 meters).

  The distance d is related to the phase differences by the following equation: 1) 2 cD1 = 2 * d * λ1 22 * 2n, where A1 and A2 are the wavelengths 21 * 22 respectively corresponding to the signals of frequency f1 and f2, and where 01, respectively (1) 2, are the phase differences between the transmitted and received signals at the frequency f1, respectively f2.

  With reference to FIG. 1, when the light vehicle A begins to cross the field of view C of the radar 2, it will give rise, on the one hand, to the triggering of an image capture by the camera 11 and on the other hand, to the computation of the interdistance DA, to several calculations of speed (VA1, ÉÉE, VAn) and of distance (dA1, ..., dAn) carried out by the means 5 of signal processing from radar 2 to a number n of instants TA1 to TAn of measurements (the frequency of these measurement instants depends on the configuration of radar 2).

  The calculated distances dm to dAn and the associated measurement times TA1 to TAn are provided to the profile determination module 6. The latter, from each distance d calculated at a time T, determines a height h of the vehicle corresponding to the height at the ground of the reflection point situated on the vehicle A and on the line of sight U, using of the following equality: h = hant d * sina. Then he draws a profile curve P connecting points of coordinates (h, T).

  For the vehicle A, it thus determines n heights hA1, ..., hAn respectively associated with the measurement instants TA1 to TAn. Then the profile determination module 6 draws a curve PA in a frame of reference whose abscissa X represents the moments of measurement and the ordinate Y represents the height. This curve PA is the curve which connects the points MAI, ..., MAn relating to the vehicle A where MAJ (; = 1 to n) has for abscissa TA; and for ordinate hA ;. The duration during which measurements are taken on the vehicle A is representative of the length of the vehicle A. The curve PA thus represents the profile of the vehicle A. An example of curve PA is shown in FIG.

  In reality, the profile determination module 6 receives distances associated with measurement instants along the water, without knowing in advance the start and end points of the data relating to the same vehicle. It determines in fact the beginning and the end of a profile as a function of the presence of successive data ranges where the measured height is equal to the height of the road at the point of intersection between said road and the line of sight U , that is to say according to the detection of periods when no vehicle is in the field of view C. The memory area 8 stores surface limit values S1, S2, S3.

  The category definition module 7 is adapted to calculate the value S of the area delimited by each profile curve P determined by the profile determination module 6 and by the abscissa axis X. This calculated area corresponds to the surface area. a section of the vehicle made parallel to the path Vc; rc.

  Thus for the vehicle A, the category definition module 7 calculates the value SA of the surface delimited by the profile PA and the axis X. This surface is hatched by vertical lines in FIG.

  Then the surface value S thus calculated for each vehicle is compared with the surface limit values S1, S2 and S3 by the category definition module 7. If the surface is between SI and S2, the module 7 selects the category C1 ("light vehicle") for the vehicle in question. If the surface is between S2 and S3, it selects the category C2 ("vehicle with caravan") for the vehicle in question and if the surface is greater than S3, it selects the category C3 ("heavy weight").

  In the example considered with reference to FIG. 1, the category definition module 7 will thus assign the category C1 to the vehicle A. The surface limit values S1, S2, S3 are, for example, determined beforehand during a step d in which the surface area of a representative sample of vehicles of each category is measured, and these limit values are deduced therefrom.

  Then, once the category of the vehicle determined by the category definition module 7, the crime determination block 9 extracts from the memory zone 10 the maximum authorized speed for said category, respectively the minimum interdistance allowed for said category. , and compares them with the average of the speed values successively calculated by the signal processing means 5 of the radar 2 for the vehicle in question, respectively at the interdistance calculated for said vehicle.

  Thus, the crime determination block 9 extracts from the memory zone 10, for the vehicle A assigned to the category C1, the speed V1max, and compares it to the sum of the speeds VA1,..., VAn divided by n. Similarly, it extracts from the memory zone 10 the interdistance Dimin and compares it with the distance DA calculated for the vehicle A. If the speed calculated for the vehicle is greater than the maximum speed authorized for the category of the vehicle and / or if the calculated intercept for the vehicle is less than the minimum allowed distance for the category of the vehicle, then the vehicle is identified as a vehicle in violation of speed and / or interdistance. The offense determination block 9 then publishes an infraction file including the date, time, place, captured image relating to said vehicle, the calculated speed value, the maximum speed value authorized for this vehicle and / or the calculated interdistance value and the minimum interdistance value allowed for this vehicle. Then the offense determination block 9 stores the infringement file in the memory zone 10.

  If the vehicle in question is not identified as an infringing vehicle, the image captured for that vehicle by digital camera 11 is deleted by block 9.

  In the embodiment considered, once the category definition module 7 has defined the category of a new vehicle, for example the category C1 in the case of the vehicle A, it provides the category defined in the counting module 12, which increments its vehicle counter of the category in question by one unit. Thus, if the vehicle is the vehicle A, the vehicle counter of the category C1 will be incremented by 1.

  In FIG. 2, the profile PB supplied by the profile determination module 6 during the passage, in the field of view C, of the heavy weight B (represented in FIG. 1 before passing through the field of view C) has been represented. from the time origin of the PA profile of the vehicle A. For the vehicle B, the category definition module 7 calculates the value SB of the surface delimited by the profile PB and the axis X. This surface is hatched by horizontal lines in Figure 2 (except for the part already covered by the surface associated with vehicle A).

  Operating in a manner similar to that described above with reference to the vehicle A, the category definition module 7 will thus select the category C3 for the vehicle B. Then the offense determination block 9 extracted from the zone 10, for the vehicle B assigned to the category C3, the speed V3max, and compares it to the sum, divided by m, m different speeds VB1, ..., VBm calculated by the signal processing means 5 during the passage of the heavy weight B in the field of view C of the radar. Similarly, it extracts from the memory zone 10 the interdistance D3min and compares it to the calculated DB interdeference for the vehicle B, also provided by the signal processing means 5.

  FIGS. 3a, 3b and 3c show three profiles obtained according to the invention during the passage of three different trucks in the field of view C. In one embodiment of the invention, the set of infringement files are routinely transmitted to an official offense reporting center, for example via telecommunication links established between the system 1 and said center. The identification of the vehicle will be done in this center.

  Thus, a method and a system according to the invention allow automatic surveillance operations and establishment of statements of offense adapted to different categories of vehicles, which are subject to offense characteristics specific to each category (limits speed, interdistance etc.).

  The invention makes it possible to define this category from the signals received by the dual-frequency radar.

  A system according to the invention can be used in a traveling manner. It can be installed satisfactorily quickly at any monitoring point and without the need for heavy infrastructure.

  Compared with the prior art, it makes it possible to reduce the number of useless data stored (images, speed, calculated interdistance), then possibly transmitted over communication links, by enabling in real time the definition of the category of a vehicle. and to immediately infer whether a finding should be made or whether the stored data should be deleted.

Claims (1)

13 Claims   1. System (1) for monitoring vehicles traveling along a track (Vcirc) comprising: - a radar (2) with a Doppler effect comprising a generator (4) of successive pulses at two frequencies (fi, f2) and a transmitting and receiving antenna (3) associated with a field of view (C) covering at least a part of said channel, said radar being adapted to the measurement, at times of determined measurements, of the signals received by the antenna and derived from the reflection on the vehicles of the pulses emitted by said antenna, and calculating, from said signals, the speed (VA ,, VB1) of the vehicles (A, B) situated in the field of view, and the distance (dAm, dBl) between these vehicles and the radar; means (6) for determining a profile (PA) capable of determining a profile of each of said vehicles (A) from the distances (dAl, ... dAn) between said vehicle and the radar calculated by said radar when several moments of measurement (TAI, ... TAn); - Category selection means (7) adapted to select for each vehicle a category from predetermined categories, according to said predetermined profile.   2. System (1) for monitoring vehicles according to claim 1, wherein the antenna (3) of the radar (2) is positioned overhanging the path (Vcirc). The vehicle monitoring system (1) according to claim 1 or claim 2, wherein the profile determining means (6) is adapted to determine the profile (PA) of a vehicle (A) under the shape of a curve in a given referential connecting points having as abscissa a measurement instant (TA1, ..., TAn) and as ordinate a height (hA1, ..., hAn), said height being determined according to the distance (dA1, ES, dAn) computed at said measurement instant, the height hart of the radar antenna with respect to the track (Vc; rc) and an angle value (a) equal to angle described by the track with respect to a line of sight (U) on which the field of view (C) is centered.   A vehicle monitoring system (1) according to any one of the preceding claims, wherein the category selection means (7) selects the category (C1, C2, C3) of a vehicle (A) by comparing the surface (SA) described by the profile (PA) determined for the vehicle (A) and surfaces (S1, S2, S3) respectively associated with the predetermined categories.   5. System (1) for monitoring vehicles according to any one of the preceding claims, further comprising means (10) for storing threshold speeds (V1max, V2max, V3max) associated respectively with categories (C1, C2, C3). predetermined means and having means (9) for determining an offense capable of comparing the measured speed of a vehicle with the threshold speed associated with the category selected for said vehicle, and thus determining whether the vehicle is in a state of offense and capable of to, if said vehicle is in a state of infringement, to edit corresponding infringement data.   The vehicle monitoring system (1) according to any one of the preceding claims, further comprising means (5) for measuring the distance between a first vehicle located in the field of view (C) and a second vehicle having preceded said vehicle in the field of view, means (10) for storing inter-vehicle minimum distances associated respectively with the categories (C1, C2, C3), and means (9) for determining an offense capable of comparing the interdistance (DA) measured for the first vehicle (A) at the minimum inter-vehicle distance (Dimin) associated with the category selected by said first vehicle, and thus to determine whether the vehicle is in a state of offense and to edit data offense if the vehicle is in a state of infringement.   7. System (1) for monitoring vehicles according to claim 5 or claim 6, further comprising means (11) for capturing at least one image of a vehicle when entering the field of view, and means (9) capable of associating said image with the infringement data edited for said vehicle.   The vehicle monitoring system (1) according to any one of the preceding claims, further comprising counting means (12) as a function of the category (C1, C2, C3) selected for vehicles traversing the field of view. (VS).   9. A method for monitoring vehicles traveling along a track (Vcirc), part of which is included in a field of view (C) of a Doppler radar (2) comprising a pulse generator (4). two successive frequencies (fi, f2) and a transmitting and receiving antenna (3) associated with said field of view, according to which: the signals originating from the reflection of the pulses emitted by said antenna and received by the antenna are measured at times of determined measurements, and the speed (VA1, VB1) of the vehicles (A, B) situated in said field of view and the distance (dAm, dBl) between these vehicles and the radar are calculated from said signals; a profile (PA, PB) of each of said vehicles is determined from the distances between said vehicle and the radar calculated by said radar during several measurement times; - A category for each vehicle is selected from predetermined categories according to the profile determined for said vehicle.   10. A vehicle monitoring method according to claim 9, wherein the antenna (3) of the radar (2) above the channel (Vc; rc.) Is positioned beforehand.   A vehicle monitoring method according to claim 9 or claim 10, wherein the profile of a vehicle is determined as a curve in a given frame, said curve connecting points having as abscissa an instant of measure (TAI, ... TAn), and as ordered a height (hA1, ... hAn), said height being determined as a function of the distance (dm ... dAn) computed at said moment of measuring the height (hant ) of the radar antenna with respect to the track and an angle value (a) equal to the angle described by the track with respect to a line of sight (U) on which the field of view (C) is centered .   A vehicle monitoring method according to any of claims 9 to 11, wherein the category of a vehicle is selected by comparing the area (SA) described by the profile (PA) determined for said vehicle (A) and to surfaces (S1, S2, S3) respectively associated with the predetermined categories.   13. Vehicle monitoring method according to any one of   Claims 9 to 12, according to which:   comparing the speed of a vehicle with a threshold speed (V1max, V2max, V3max) associated with the category selected for said vehicle (C1, C2, C3) and thus determining whether the vehicle is in a state of infringement; - if said vehicle is in a state of infringement, it publishes corresponding offense data.   14. The method of monitoring vehicles according to any one of claims 9 to 13, wherein: the interdistance (DA) is measured between a first vehicle (A) located in the field of view and a second vehicle preceding said vehicle in the field of view (C), comparing said measured interdistance for the first vehicle with a minimum inter-vehicle distance (Dimin) associated with the category (C1) of said first vehicle, and thus determining whether the vehicle is in offense status; - if said vehicle is in a state of infringement, it publishes corresponding offense data.   A vehicle monitoring method according to claim 13 or claim 14, wherein an image of a vehicle is captured upon entry into the field of view, and said image is associated with the edited offense data for said vehicle. to establish a statement of offense.   16. Vehicle monitoring method according to any one of claims 6 to 15, according to which the vehicles passing through the field of view (C) are counted according to the category (C1, C2, C3) of said vehicles.