EP1610279B1 - Method and system for the surveillance of moving vehicles - Google Patents

Abstract

The method involves comparing calculated speed of each of multiple vehicles (9, 11, 12) with an allowed speed (V max). An image representative of a viewing angle of a Doppler effect dual frequency radar (2) is captured and stored when the vehicles exceed the speed (V max). A number (N) of vehicles situated in the angle is determined from reflection signals received by the radar, when the vehicle exceeds the speed to process image. An independent claim is also included for a system to monitor vehicles moving along trajectories.

Description

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

This monitoring generally comprises, on the one hand, 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 to exceeding 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 is generally located at the edge of the road or at a 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 its line of sight of the speed of the vehicle present in its field of view.

Radars appeared, measuring not only the speed, but also the distance to the radar of a vehicle in the beam. These radars thus allow when there are several vehicles simultaneously in the beam and a vehicle has committed a speeding, to determine which of these vehicles is affected by the speeding.

The document US 6,266,627 describes a technique for determining both the speed and the position of a vehicle using a pulsed Doppler monofrequency radar, that is to say emitting pulse signals. Knowing the speed of propagation of the wave, we deduce from the time elapsed between the transmitted signal and the reflected signal the distance to the target.

The document EP 0 933 648 describes a traffic measurement system using a two-frequency Doppler radar. Such a type of radar emits successively signals with two adjacent frequencies. By analysis of frequency offset between a signal transmitted by the radar and a signal received by the same radar and coming from a reflection on a vehicle of the transmitted signal, the Doppler frequency and therefore the speed are determined. The distance is deduced from the phase shift between the signals reflected after successive transmissions at alternating frequencies.

Generally, the subsequent processing of offense data, which includes captured images, calculated speeds and distances, and which are used to establish the official statement of offense, differs according to whether a vehicle or that several vehicles appear on the image. For example, some legislations do not allow the use, in an official statement of offense, of a photo representing several vehicles. However, the finding of the presence of more than one vehicle on the picture is generally carried out late. Indeed, it often takes place after an official agent has received all of the data in bulk and has reviewed the photos provided.

The document DE 198 10 302 describes a technique for determining whether one or more vehicles are present in the radar field of measurement, using digital image processing, to avoid unnecessary storage of measures in countries whose legislation refuses velocity measurements in case more than one vehicle is in the measuring field.

The present invention aims at providing a method and a system making it possible advantageously to take advantage of the information delivered by a radar allowing the measurement of the speed and the distance of a vehicle situated in the field of view, in order to optimize the data processing of offense.

• on calcule la vitesse des véhicules situés dans le champ de visée ;
• on compare la vitesse calculée d'un véhicule à une vitesse autorisée ;

Le procédé comprend en outre les étapes suivantes en cas de dépassement de vitesse autorisée par un des véhicules :

• on capture et on stocke une image représentative du champ de visée du radar, pour identifier le véhicule ;
• à partir des signaux de réflexion reçus par le radar, on détermine un nombre de véhicules situés dans le champ de visée lors de la capture de l'image ;
• et on traite l'image capturée et la vitesse pour le véhicule en dépassement, en fonction du nombre de véhicules déterminé.

For this purpose, according to a first aspect, the invention provides a method for monitoring vehicles moving along tracks. Velocity is measured by radar from received reflection signals for vehicles in the radar field of view. The method comprises the following steps:

• the speed of vehicles in the field of view is calculated;
• comparing the calculated speed of a vehicle with an authorized speed;

The method further comprises the following steps in case of exceeding the speed allowed by one of the vehicles:

• capturing and storing an image representative of the field of view of the radar, to identify the vehicle;
• from the reflection signals received by the radar, a number of vehicles located in the field of view are determined during the capture of the image;
• and processing the captured image and the speed for the overtaking vehicle, according to the determined number of vehicles.

The method according to the invention makes it possible to adapt the processing of the infringement data as soon as these data are generated, on the basis of the information available at this stage. The exploitation of the number of vehicles can be immediate to realize the adapted treatment. It is not necessary to wait for the intervention of an operator to do this.

According to a second object, the invention proposes a system for monitoring vehicles moving along tracks, which comprises means for implementing a method according to the first aspect of the invention. Such a system thus comprises a radar measuring the speed from reflection signals received from each of the vehicles located in the field of view of the radar. It further comprises offense determination means for identifying an authorized speed override of one of the vehicles, image capturing means for capturing an image representative of the field of view and storage means for storing said image, means for determining a number of vehicles for determining the number of vehicles in the field of view during the image capture, and processing means for processing the captured image for each passing vehicle, and the speed measured associated, depending on the number of vehicles determined.

• la figure unique représente un mode de réalisation de l'invention.

Other features and advantages of the present invention will become apparent in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

• the single figure shows an embodiment of the invention.

In the single figure is shown a system 1 according to the invention installed on the edge of a road with three channels V1, V2, V3. It includes 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 extending around the line of sight U of the radar 2, about 5 degrees wide, which corresponds to a beam of waves emitted by a transmitting and transmitting antenna. 3. The U axis of view is at an angle of 20 to 25 degrees with the direction of channels V1, V2 and V3.

The radar 2 comprises means for regularly switching the frequency of the signal emitted by the antenna 3, between a value f1 and a value f2. In one embodiment, for example, f1 = f0 + ΔF / 2 and f2 = f0 - ΔF / 2, with f0 = 24.125 GigaHertz (GHz) and ΔF = 800 kiloHertz (kHz). The frequency signal f1, respectively f2, is transmitted for a duration of one microsecond (1 μs) before being switched to the frequency signal f2, respectively f1. Successive transmission of a signal to f1 and a signal to f2 constitutes a transmission cycle.

Each vehicle traversing the field of view during its path on the tracks respectively give rise to reflected signals picked up by the antenna 3.

The radar 2 comprises, among other things, signal processing means 4 operating on the signals emitted by the antenna 3 and on the signals received by the antenna and originating from the reflection on the vehicles crossing the field of view of the radar 2, transmitted signals. These signal processing means 4 make it possible to determine the speed of these vehicles and the distance separating them respectively from the radar 2.

The system 1 further comprises a module 5 for determining the exceeding of a maximum authorized speed value Vmax. The speed Vmax is defined during a preliminary configuration operation of the module 5.

The system 1 also comprises a camera 6 whose field of view is representative of the field of view of the radar 2. The field of view allows the reading of the number plates and / or the identification of the driver's face of the vehicles present in the field of view at the time of the shooting. In the embodiment, the camera 6 is a digital camera. It is equipped with a flash allowing the illumination of the scene during the shooting.

The system 1 also comprises data storage means 7. These storage means 7 can store, for example, the data corresponding to the signals received or transmitted by the antenna 3, the image data captured by the camera 6, or calculated speeds and distances.

The system includes a module 8 for determining the number of vehicles present in the field of interest at a designated time, as well as means of constituting the offense data 10 for the subsequent establishment of the offense reports.

The calculation of the speed of a vehicle is performed by determining in a known manner the Doppler frequency generated by each vehicle present in the field of view.

In the embodiment considered, the received signals and signals corresponding in frequency and phase to the transmitted signals, are combined in the signal processing means 4, 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 f _D is representative of the speed of the vehicle at the origin of the reflections. Indeed it is equal to 2 * V _u / λ, where Vu is the projection of the vehicle speed vector on the line of sight U and λ is the wavelength of the transmitted signal. We deduce Vu, then the velocity V of the vehicle equal to Vu / cosα.

The digital processing conventionally comprises a frequency transformation of the signals by Fast Fourier Transform (FFT). Each vehicle located in the field of view at a given moment therefore gives rise to a line appearing in the spatial domain, at the Doppler frequency f _D representative of the speed of this vehicle.

The signal processing means 4 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.

où d est la distance entre le radar et le véhicule, λ1 et λ2 sont les longueurs d'onde correspondant respectivement aux signaux de fréquence f1 et f2, et où Φ₁, respectivement Φ₂ sont les différences de phase entre les signaux transmis et reçus à la fréquence f1, respectivement f2.Thus the distance is related to these phase differences by the following equation: ${\mathrm{\phi }}_{\mathrm{2}}\mathrm{-}{\mathrm{\phi }}_{\mathrm{1}}=2*\mathrm{d}*\frac{\mathit{\lambda }1-\mathit{\lambda }2}{\mathit{\lambda }1*\mathit{\lambda }2}*2\mathrm{\pi },$

where d is the distance between the radar and the vehicle, λ1 and λ2 are the wavelengths corresponding to the frequency f1 and f2 signals, and where Φ _1, Φ ₂ are respectively the phase differences between the transmitted and received signals at the frequency f1, respectively f2.

In the overflow determination module 5, the calculated speed V for each vehicle with Vmax.

For example, with reference to the single figure, the velocity and the distance are measured for the vehicles 9, 11 and 12 respectively traveling on the tracks V1, V2 and V3 and crossing the field of view.

In case of overtaking noted, for example for the vehicle 9, is triggered immediately taking a photo of the field of view by the camera 6 and stored in the storage means 7 a file with the digital photo taken , the speed V9 and the distance d9 calculated for the vehicle 9.

According to the invention, during the observation of an authorized overspeed, the calculation, by the module 8, of the number of vehicles then present in the field of view of the vehicle is also triggered simultaneously with the shooting being triggered. radar 2.

This calculation is made from the signals received by the antenna 3 of the radar and coming from the reflection on the vehicles crossing the field of view, from the signals emitted by the antenna and from the data resulting from the processing of these signals by the radar processing means 4.

More or less complex calculations can be made according to the desired accuracy of the result.

In one embodiment, it is possible, for example, if the calculation of the speed V9 has been determined from signals reflected following the emission at a time T of a cycle (f1, f2), analyzing the signals received by the antenna 3 which come from all the reflections following the emission at the instant T of this cycle (f1, f2). A spectral image is obtained which comprises respective lines at the Doppler frequencies determined for each of the vehicles having reflected this cycle of transmitted signals. From the number of lines, we deduce an estimate of the number of vehicles present at time T in the field of view. The number of vehicles is then taken equal to the number of rays.

In another embodiment, a spectral image can be determined from signals of a cycle (f1, f2) received by the antenna 3, said cycle signals (f1, f2) being those reflected by the offending vehicle. at the time of the photo.

In another embodiment, an image can be reconstructed spectral field of view as appearing at the instant of taking the picture, taking into account, for the constitution of this spectral representation, the signals received by the antenna 3 and from the reflection of signals during a number determined cycles (f1, f2) preceding the moment of taking a picture.

Once the number N of vehicles appearing on the photograph at the time of the shooting thus estimated from the signals received by the radar, it processes the file stored in memory 7 and consisting of the image, the distance and the speed measured for the infringing vehicle in the means of constituting the infringement data 10.

If N = 1, a file is created for establishing an infringement contract using the image and speed data.

If N is strictly greater than 1, in the case of use in a country where the law prohibits the sending to the owner of a vehicle of a statement of offense including an image where his vehicle is not not the only vehicle represented, stop processing, for example by destroying the corresponding data file.

In another embodiment, a mapping of the channels has previously been recorded making it possible to deduce from a measured distance between a vehicle in the field of view and the radar, a corresponding channel. We have also previously established the correspondence between each channel, and the area where this path is represented in the photos.

Thus, when constituting infringement data for an infringing vehicle by the means 10, it is determined from the distance d to the radar calculated by the signal processing means 4, for the infringing vehicle considered, the track on which he is.

A process is then carried out to highlight the vehicle concerned by the infraction in relation to the other vehicles. For example, an automatic treatment surrounding the representation of the channel concerned by a red color and thus surrounding the vehicle in violation. In another embodiment, the zones corresponding to the representations of the tracks other than that on which the vehicle is located can be lightly grayed out.

Then we establish a file for the establishment of the official statement of offense including the image thus treated and the speed of the vehicle found in violation.

All the files for the establishment of the official statement of offense may be regularly transmitted to an official offense reporting center, for example through telecommunication links established between the system 1 and the center. . The identification of the vehicle will be done in this center.

The passage of a vehicle in the field of view of the radar 2 gives rise for example to about 50 analyzes. Each analysis corresponds to a particular Doppler frequency. The result of each analysis includes the speed of the vehicle, the distance between the radar and the vehicle and possibly additional information such as the intensity of the received signal, an indicator of the quality of the analysis, the duration of the analysis etc. .

In a particular embodiment of the invention, the module 5 for determining the overshoot triggers the picture by the shooting means 6 and the calculation of the number of vehicles by the module 8 at the end of a fixed number. analysis that has determined a speed greater than the maximum speed.

Thus, a method and a system according to the invention allow automatic operations of monitoring and establishment of statements of offense adapted to the number of vehicles located a priori on the captured image. Since this number can be determined as soon as the images are taken, the treatments are optimized, for example by deleting the data comprising the image, the speed, etc. for cases for which the statements of offense can not be established when several vehicles appear on the image because of legislation or case law. Thus we reduce the number of useless data stored, and then transmitted on the communication links.

Claims (9)

1. Method for monitoring vehicles (9, 11, 12) moving along lanes (V1, V2, V3), the speed being measured by a radar (2) from received reflected signals, for vehicles located in a target field of said radar, said method comprising the following steps:

   - determining the respective speed of the vehicles in the target field;

   - comparing the calculated speed of each vehicle with an authorised speed (Vmax); and said method comprising the following steps if one of said vehicles exceeds the authorised speed:

   - taking and storing an image representative of the target field of the radar to identify the vehicle;

   - determining, from the reflected signals received by the radar, a number (N) of vehicles located in the target field when taking the image;

   - and processing the taken image as a function of said determined number of vehicles.
2. Method as claimed in Claim 1, wherein if said number is strictly greater than 1, at least the taken image is deleted.
3. Method as claimed in Claim 1, wherein for the vehicles in the target field of the radar the distance respectively separating them from the radar is calculated and if said number is greater than 1, elements of a proof of violation are established by implementing the following steps:

   - determining the location of the representation of the vehicle exceeding the speed on the taken image for the vehicle exceeding the speed, using the distance calculated for the vehicle;

   - processing to highlight on the image the representation of the vehicle in question with respect to the representation of the other vehicles appearing on the image;

   - and associating with the thus processed image at least the speed determined for the vehicle in order to establish a proof of violation element.
4. Method as claimed in any one of the preceding Claims, wherein the speeds and distances are measured at specific measurement times and a vehicle is considered to be exceeding the authorised speed at a measurement time when the speeds measured at the last measurement times and attributable to this vehicle are greater than a maximum speed value.
5. System (1) for monitoring vehicles moving along lanes (V1, V2, V3), comprising:

   - a radar (2) measuring, from received reflected signals, the speed of vehicles located in a target field of said radar;

   - violation determining means (5) for comparing the speed calculated for each vehicle with an authorised maximum speed (Vmax) and determining whether the authorised speed has been exceeded;

   - image taking means (6) for taking, if one of said vehicles has exceeded the authorised speed, an image representative of the target field to identify the vehicle, and storing means (7) for storing said image;

   - means (8) for determining the number of vehicles for determining, from the reflected signals received by the radar, the number of vehicles (N) located in the target field when taking the image;

   - and processing means (10) for processing the taken image and the speed measured for each vehicle exceeding the authorised speed, as a function of said determined number of vehicles.
6. System (1) as claimed in Claim 5, wherein if said number (N) of vehicles located in the target field when taking the image is strictly greater than 1, the means (10) for processing the image and the speed stops processing the data relating to the vehicle exceeding the authorised speed.
7. System (1) as claimed in Claim 5, further comprising:

   - distance calculating means (4) for calculating the distance separating the radar (2) from each vehicle located in the target field;

   - locating means (10) for determining, if said number is greater than 1, the location of the representation of said vehicle on the taken image for a vehicle, using the distance calculated for said vehicle;

   - highlighting means (10) for performing a processing step to highlight on the image, with respect to the other vehicles represented on the image, the vehicle in question and associating with the thus processed image with [sic] the speed determined for the vehicle in order to establish a proof of violation element.
8. System (1) as claimed in any one of the preceding Claims 5 to 7, wherein the radar (2) measures the speed and distance of the vehicles in the target field at specific measurement times, and wherein the violation determining means (5) consider that a vehicle is exceeding the authorised speed at a measurement time when the speeds measured at the last measurement times and attributable to this vehicle are greater than a maximum speed value.
9. System (1) as claimed in any one of Claim 5 to 8, wherein the radar is a dual-frequency Doppler radar.

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