Automatic counting device with thermal sensor associated with a magnetometer

Abstract

The invention relates to a device for counting moving targets, which includes a pyroelectric sensor (2) having at least two detection cells configured to thermally detect the passage of one of the targets in front of each of the detection cells, and a computer (6) coupled to the pyroelectric sensor (2) and configured to determine the direction of passage of the target in front of the detection cells. The device further includes a metal detector (4) which is internal to the device, coupled to the pyroelectric sensor (2), and configured to activate upon detection of the target by the pyroelectric sensor (2) and to evaluate the amount of metal in the target.

Description

[0001] DESCRIPTION

[0002] TITLE: AUTOMATIC COUNTING DEVICE WITH THERMAL SENSOR ASSOCIATED WITH A MAGNETOMETER

[0003] Technical field

[0004] The present invention relates to a counting device, intended to count the passages of moving targets characterized by a thermal signature and by the more or less strong presence of ferromagnetic metallic masses, such as pedestrians, cyclists and motorized vehicles as well as a method of implementing such a device.

[0005] Previous techniques

[0006] In the state of the art, counting devices are known for counting the passage of moving targets based on the thermal signature of the targets.

[0007] When these devices are used for counting on shared roads open to motorized vehicles and soft mode traffic (bicycle, pedestrian, scooter), these devices do not allow discrimination between users of soft modes of transport (bicycle, pedestrian, scooter, roller skates) and motorized modes of transport such as motor vehicles, for example cars, trucks, agricultural machinery or others.

[0008] Some types of meters, on the other hand, are capable of ensuring counting by ensuring discrimination between users of soft modes and those of motorized modes. This is particularly the case for meters using a video sensor, or buried magnetic loops associated with a pyroelectric detector or buried piezoelectric linear sensors.

[0009] Video counting devices thus make it possible to classify moving targets with precision, but existing solutions are not energy-independent and require a power supply to be able to count on long durations (for example, 6 months, 1 year or 2 years). Solutions based on magnetic loops or piezoelectric linear sensors make it possible to distinguish targets, but they are very intrusive since they require making a groove in the roadway.

[0010] Statement of the invention

[0011] The invention aims to overcome at least some of the aforementioned drawbacks and to propose a device for counting and determining the passage of a target, capable of discriminating the target according to its nature, while being energy-autonomous and non-intrusive for the roadway. The objective of the invention is therefore to provide a counting device suitable for shared roads which is easy and quick to install, unlike the existing state of the art.

[0012] In view of the above, the subject of the invention is a target counting device having a thermal signature, said device comprising a pyroelectric sensor having at least two detection cells configured to thermally detect the passage of a target in front of each of said detection cells, a computer coupled to the pyroelectric sensor and configured to determine the direction of passage of said target in front of said detection cells, the device further comprising an internal metal detector coupled to the pyroelectric sensor and configured to activate upon detection of the target by said pyroelectric sensor in order to evaluate the quantity of metal in said target.

[0013] Such a device allows independent counts to be made depending on the type of target detected by the device, each count being characterized by the detection of a moving target in front of a detection cell or by a passage in front of the two detection cells, and by an evaluation of the quantity of metal in this target.

[0014] In addition, such a device is compact, easy to install and maintain, and advantageously connected, allowing maximum information to be collected on the detected targets.

[0015] Preferably, the metal detector comprises a magnetometer configured to detect a variation in magnetic fields caused by the movement of the target during or after the passage of said target in front of each of said detection cells when said magnetometer is activated.

[0016] The magnetometer is for example configured to exploit the detection of variation of magnetic fields, only during the period of acquisition of the thermal signals, with the aim of providing a ferromagnetic metal detection signal complementary to the two thermal signals and of minimizing consumption to allow the energy autonomy of the system.

[0017] For example, the magnetometer is configured to be algorithmically operated during the period of acquisition of thermal signals, namely a duration of between one hundred and one thousand milliseconds after its activation caused by the detection of the passage of the target in front of the pyroelectric sensor.

[0018] Advantageously, the activation time of the magnetometer is between three hundred and six hundred milliseconds when a single target such as a pedestrian, bicycle or vehicle passes.

[0019] According to one embodiment, the pyroelectric sensor is a digital sensor with stereoscopic operation associated with an infrared lens and making it possible to measure the speed of passage of the moving target.

[0020] In one embodiment, the pyroelectric sensor comprises two pairs of two cells, each pair of two cells comprising a masked reference cell and an unmasked detection cell.

[0021] Advantageously, the device further comprises an optical lens adapted to the thermal infrared signal emitted by the target and arranged in front of the pyroelectric sensor.

[0022] The device may further provide that the optical lens is a Fresnel lens, a Germanium lens or a zinc selenide lens.

[0023] Preferably, the device comprises at least one connection from the pyroelectric sensor to the computer and one connection from the metal detection sensor to the computer. Furthermore, the computer is capable of incrementing several counting lists as a function of the simultaneous detections of the pyroelectric sensor and the metal detector and according to said quantity of metal in said target relative to a range of metal quantity values.

[0024] The invention also relates to a method for implementing a counting device as defined above, for counting targets having a thermal signature, said method comprising the following steps:

[0025] - a first wake-up step during which the pyroelectric sensor detects the presence of a target in front of at least one of the detection cells by detecting the thermal signature of said target in front of the pyroelectric sensor;

[0026] - a second acquisition step during which the metal detector is activated as long as thermal extrema are detected and then for a predefined duration; and

[0027] - a third analysis step during which the calculator compares on the one hand absolute data and derivatives of two thermal curves from the two detection cells of the same pyroelectric sensor, and on the other hand absolute data and derivatives of magnetic variation curves from the metal detector.

[0028] Brief description of the drawings

[0029] The invention will be better understood from a detailed study of an embodiment taken as a non-limiting example and illustrated by the appended drawings, in which:

[0030] [Fig 1] schematically represents the architecture of the counting device.

[0031] [Fig 2] represents detection results of two passages of a motor vehicle in front of the device, this detection being characterized by a medium or strong measurement of metal detection; and [Fig 3] represents detection results of two passages of a pedestrian or a cyclist in front of the device, this detection being characterized by a weak measurement of metal detection. Detailed description

[0032] Figure 1: Descriptive functional diagram of the counting device

[0033] Figure 1 illustrates a target counting device 1 according to the invention.

[0034] Targets are entities such as moving objects or living beings with a thermal signature, for example pedestrians, cyclists, scooters and vehicles including cars, camper vans, buses, agricultural vehicles, construction vehicles, or any other vehicle.

[0035] By "thermal signature", it is understood in the context of the present description that the target is distinguished from its environment by a characteristic thermal trace, that is to say infrared signals that said target emits as a function of its temperature in a thermal detection beam 10 created by the assembly of a thermal detector positioned in the focal plane of an 8-12 pm infrared lens adapted to the radiation of the human body.

[0036] The device 1 comprises a pyroelectric sensor 2 having at least two detection cells.

[0037] The two detection cells can, for example, be included in an array comprising several detection cells, for example four cells, of which only two are used.

[0038] The two detection cells are configured to thermally detect the passage of moving targets in front of each of said detection cells.

[0039] The device 1 is equipped with a metal detector consisting of a second metal detection sensor 4 giving a signal characteristic of the metal detection created, or not, during the movement of the target moving by creating thermal detection beams 10.

[0040] The device 1 further comprises a computer 6 with which the pyroelectric sensor 2 communicates via a link 11a and the metal detection sensor via a link 11b. The computer 6 comprises a data processing unit, capable of recovering the signals coming from the pyroelectric sensor 2 and the metal detection sensor 4 and then processing them to create data classified by channel and stored internally in a non-volatile memory which can then be transmitted to internal storage means and then to a data transfer means 5 to computer tools associated with the data from the single or multi-channel counting boxes.

[0041] The computer 6 carries out its tasks in an organized manner over time by means of a clock internal or external to its processing unit and which can be programmed to apply a method for processing the data collected, in particular to store them in time-stamped slots of 15 minutes, to then transmit them automatically between 1 and 96 times per day.

[0042] The computer 6 is connected to the pyroelectric sensor 2 and configured to determine the direction of passage of said target in front of said detection cells, namely a first direction 7 in which a first of the two detection cells detects the target first then the second of the two detection cells detects the target second, or in a second direction 8, opposite to said first direction during its passage in front of the device 1, and in which the second of the two detection cells detects the target first then the first of the two detection cells then detects the target during its passage in front of the device 1.

[0043] The metal detector 4 connected to the computer 6 is configured to activate upon detection of said target by said pyroelectric sensor 2 in order to evaluate the quantity of metal in said target. A magnetometer will advantageously be used, making the detector capable of being placed in a waterproof case and whose power consumption will remain particularly low.

[0044] We thus produce a device 1 having two sensors in a single box, which is installed in a non-invasive manner, that is to say without requiring the installation of infrastructure or work in the area to be monitored, unlike known devices which require, for example, the installation of sensors cast into the roadway or connected to the electrical network.

[0045] For example, a device 1 can be produced which forms a counting box which integrates a stereoscopic thermal sensor in native mode on a motherboard as well as an optional magnetometer on a daughter card managed by the computer 6 of the motherboard when the pyroelectric sensor 2 launches an acquisition.

[0046] The calculator 6 is further configured to count said target in at least one counting list according to said quantity of metal, stored locally in the data processing and / or storage unit 5. The counting lists are incremented according to the simultaneous detections of the pyroelectric sensor and the metal detector and according to said quantity of metal in said target relative to a range of metal quantity values.

[0047] A counting device 1 is thus produced which is capable of counting people, vehicles or other moving objects with a thermal signature (pedestrians, cyclists, human-powered vehicles, motor vehicles, etc.), of detecting the direction of passage of this target, of evaluating its passage speed, of evaluating its metallic mass using the metal detector, and of classifying the target counted in a particular list, which makes it possible to identify the uses of the area monitored by the device 1 (types of target classified according to a movement speed threshold and a second threshold linked to the evaluation of the metallic mass, etc.), and this with very low energy consumption to be energy-independent while guaranteeing operation in the field for several months to several years.

[0048] The metal detector 4, internal to the device, may be of a different type from the magnetometer, provided that it allows the characterization of the target, and in particular its classification as a vehicle, a cyclist or a pedestrian, for example, directly or indirectly, via a variation in curve detected when this target passes.

[0049] Preferably, the magnetometer is configured to detect a variation in magnetic fields induced by the movement of the metal associated with the target during or after the passage of said target in front of each of said detection cells when said magnetometer is activated.

[0050] The metal detector can be made from a high-precision magnetometer that allows direct detection of a variation in the Earth's magnetic field in front of it or around it, caused by the movement of a metal mass associated with the moving target.

[0051] By activating the magnetometer measurement only when a target is detected by the pyroelectric sensor 2 which monitors the area continuously when it is in operation, the device 1 has a particularly low energy consumption in order to allow its energy autonomy for a period of several months to several years.

[0052] The device 1 is therefore self-powered, that is to say powered internally by an energy accumulator such as an electric cell or a battery connected to a means of energy production, directly coupled to the device 1 to power it, such as a solar panel.

[0053] The magnetometer is activated for the detection of variation in local terrestrial magnetic fields when the target is detected by the pyroelectric sensor 2, i.e. the target triggers one of the detection cells or both detection cells by crossing configurable thresholds.

[0054] The magnetometer is then configured to detect a variation in the magnetic field at the target when said target passes through the area monitored by said magnetometer. A passage is considered to be made by a target when it passes consecutively at least once in front of each of the two detection cells, the counting device 1 aiming to count the passages of the targets in a particular delimited area corresponding to the detection limits of the pyroelectric sensor 2 associated with an infrared lens to create a detection cone 9.

[0055] The pyroelectric sensor 2 is for example a digital bus thermal sensor, which allows minimal energy consumption and high thermal robustness of the signal to be processed by the computer 6.

[0056] The pyroelectric sensor 2 contains, for example, two detection pairs, each formed of two masked detectors to serve as a stable thermal reference for the two detectors remaining active in the two detection pairs.

[0057] Figure 2 and 3: Thermal curve and metal detection measurements according to the direction of passage and types of practices.

[0058] As illustrated by Figures 2 and 3, the signals of the link 11a coming from the different cells of the pyroelectric sensor 2 indicate that each pair of cells provides a signal of the same type but shifted in time taking into account the passage of the target in front of one cell then the other, which makes it possible to analyze these passages.

[0059] Curve 14 (THERMAL CURVE 1) represents a detection curve of a target in front of a first cell, and curve 15 (THERMAL CURVE 2) that in front of a second cell.

[0060] For example, curve 14 represents the derivative of the thermal signal provided by the first cell of the pyroelectric sensor 2, and curve 15 represents the derivative of the thermal signal provided by the second cell of the pyroelectric sensor 2.

[0061] A first pass results in the activation of the first cell visible on curve 14 which is followed by the activation of the second cell immediately after, visible on curve 15.

[0062] In this case, the target passes in a first direction 7 from the first detector to the second.

[0063] Curve 16 (METAL DETECTION CURVE) represents the variation in magnetic field detected by the metal detector 4, during the acquisition period of the device 1.

[0064] A passage in the opposite direction results in the activation of the second cell visible on curve 14 which is followed by the activation of the first cell immediately after, visible on curve 15.

[0065] In this case, the target passes in a second direction 8 from the second cell to the first. If curve 16 does not undergo any notable variation, this indicates that the target does not contain any significant ferromagnetic metal mass and is therefore a pedestrian or a bicycle but not a vehicle (truck, car, agricultural or construction machinery, etc.). This field case with two user passages in soft mode in an opposite direction is illustrated in Figure 3.

[0066] If curve 16 shows significant variations above a configurable threshold, this indicates that the target contains a significant ferromagnetic metal mass and is therefore a vehicle (truck, car, agricultural or construction machinery, etc.) but not a pedestrian or a bicycle. This field case with two user passages in motorized mode in opposite directions is illustrated in Figure 2

[0067] The amplitude of the variations of the metal detector makes it possible to characterize the quantity of ferromagnetic metal in the vehicle and therefore to classify the presence of metal into several categories (very low, low, high or very high)

[0068] At rest, the computing unit cyclically examines the digital data from the two thermal detection cells contained in the thermal sensor, the consumption of which has a very low value, i.e. a few tens of microamperes.

[0069] According to one embodiment, the pyroelectric sensor 2 is a digital thermal sensor with stereoscopic operation.

[0070] Advantageously, the device 1 comprises at least one optical lens 13 adapted to the thermal infrared signal 10 emitted by the target and arranged in front of the pyroelectric sensor 2.

[0071] In particular, the pyroelectric sensor 2 is placed in the focal plane of the lens 13.

[0072] The combination of the pyroelectric sensor 2 having two signals of the same type from two pairs of detectors in the focal plane and close to the focus of the lens 13 makes it possible to use stereoscopic type algorithmic processing.

[0073] The assignment of the direction of passage can be arbitrarily defined on the device 1, or modified by the user via the 180° rotation of the sensor or in a control software setting. Thus, as the sensors are stereoscopic, and advantageously placed so that the object(s) / living being(s) pass in front of a first doublet of cells then a second, it becomes very easy to determine the direction of passage.

[0074] The device may provide, for example, that the optical lens 13 is a Fresnel lens, a Germanium lens or a zinc selenide lens.

[0075] Each lens-sensor pair is adjusted so that the detection cells are close to the focal plane detection cells and arranged to be substantially in the focal plane of the optical lens 13 or close to the focal plane, at a distance between the lens and the sensor which is adjusted so that the image received on the detection cells is sharp, that is to say with a focus carried out.

[0076] At rest, each of the detection cells near the focal point of the lens is illuminated by a stable thermal scene, which characterizes this state of rest by maintaining the derivatives of the digital thermal curves below a configurable threshold thanks to the fact that the signals from the detectors are of a comparable order of magnitude. During passages, the thermal equilibrium is broken and is detected by the program embedded in the computer 6 which triggers a signal processing algorithm using the measurement of the signals from the pyroelectric sensor 2 and jointly from the metal detection sensor 4, then a decision to count and classify the passages which consumes more energy than the previous standby state in the absence of target detection.

[0077] For example, the magnetometer is configured to be activated during a thermal acquisition period of between one hundred and one thousand milliseconds after the start of thermal acquisition activated after detection of the passage of the target by the pyroelectric sensor 2.

[0078] Thus, the algorithm for counting and classifying the passages can be launched from the start of thermal acquisition and enriched by the detection of variation in ferromagnetic metal mass measured by the metal detection sensor 4 with sufficient periodicity to detect magnetic variations while maintaining low consumption.

[0079] During the acquisition period, the calculation unit 6 implements calculation algorithms to detect the extrema of each of the two thermal curves 14, 15, determine the direction of passage and evaluate the speed of passage by temporal comparison of the two thermal curves 14 and 15 while measuring the level of the ferromagnetic mass signal 16 associated with the moving target in order to determine whether the latter can be assimilated to a vehicle.

[0080] Advantageously, the duration of signal acquisition and activation of the magnetometer is between three hundred and one thousand milliseconds. However, in one embodiment, the acquisition phase lasts until there is no longer any thermal extrema detected for an adjustable duration of, for example, between 300 ms and 1000 ms.

[0081] Quantification of the passage speed can be done at the end of data acquisition, by calculating the average delay of the derivative of the end signal with respect to that of the start signal.

[0082] In one implementation mode, the algorithm also makes it possible to quantify the drift of the Earth's magnetic field induced by the variation in metallic mass near the magnetometer when the target passes by carrying out a comparison at the end of acquisition with preset thresholds of metallic mass (low mass, medium mass and high mass) to determine whether the target must be either excluded from the counts, for example by excluding motor vehicles if the device 1 is used to count only pedestrians, or counted in a specific dedicated channel, if it is desired to count vehicles using a shared road,

[0083] Advantageously, it is also possible to provide for the automatic sending of counting data to a remote server with regular frequency, which can vary, for example, from fifteen minutes to one day.

[0084] Preferably, the device 1 comprises a means 5 for automatic transmission of counting data for the data from several channels corresponding to the counting lists by direction and by category of practice (pedestrian, bicycle, vehicle), generated by the computer 6 from algorithms processing two thermal signals from the pyroelectric sensor 2 and a magnetic signal from the additional metal detection sensor 4.

Claims

CLAIMS 1. Device (1) for counting targets having a thermal signature, comprising a pyroelectric sensor (2) having at least two detection cells configured to thermally detect the passage of a target in front of each of said detection cells, a computer (6) coupled to the pyroelectric sensor (2) and configured to determine the direction of passage of said target in front of said detection cells, the device (1) being characterized in that it further comprises an internal metal detector (4) coupled to the pyroelectric sensor (2) and configured to activate upon detection of the target by said pyroelectric sensor (2) in order to evaluate the quantity of metal in said target.

2. Counting device (1) according to claim 1, wherein the metal detector (4) comprises a magnetometer configured to detect a variation in magnetic fields caused by the movement of the target during and / or after the passage of said target in front of each of said detection cells.

3. Counting device (1) according to claim 2, wherein the magnetometer is configured to be algorithmically operated during the period of acquisition of the thermal signals.

4. Counting device (1) according to any one of claims 1 to 3, in which the pyroelectric sensor (2) is a digital thermal sensor with stereoscopic operation associated with an infrared lens and making it possible to measure the speed of passage of the moving target.

5. Counting device (1) according to any one of claims 1 to 4, in which the pyroelectric sensor (2) comprises two pairs of two cells, each pair of two cells comprises a masked reference cell and an unmasked detection cell.

6. Counting device (1) according to any one of claims 1 to 5, further comprising an optical lens (13) adapted to the thermal infrared signal emitted by the target and arranged in front of the pyroelectric sensor.

7. Counting device (1) according to claim 6, wherein the optical lens (13) is a Fresnel lens, a Germanium lens or a zinc selenide lens.

8. Counting device (1) according to any one of claims 1 to 7, wherein the calculator is capable of incrementing several counting lists according to the simultaneous detections of the pyroelectric sensor and the metal detector and according to said quantity of metal in said target relative to a range of metal quantity values.

9. Method for implementing the counting device (1) according to any one of claims 1 to 8 for counting targets having a thermal signature, said method comprising the following steps: - a first wake-up step during which the pyroelectric sensor detects the presence of a target in front of at least one of the detection cells by detecting the thermal signature of said target in front of the pyroelectric sensor (2); - a second acquisition step during which the metal detector (4) is activated as long as thermal extrema are detected and then for a predefined duration; and - a third analysis step during which the calculator compares on the one hand absolute data and derivatives of two thermal curves from the two detection cells of the same pyroelectric sensor, and on the other hand absolute data and derivatives of magnetic variation curves from the metal detector;

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