Traffic Classification Arrangement for Detection of Metal Tires Tread

Abstract

A tire or tread detection device for the classification of vehicular traffic. The invention allows the detection of tires by identifying with certainty the number of axles that make up a vehicle, thus determining its traffic category or classification, for the determination of loads, toll collection and evaluation of traffic supply and demand. The invention is a development integrated by hardware and software, electronic control devices, signal analysis and communications. The device is made up of Hall Effect sensors for detecting the magnetic field and magnetic field reinforcement magnets, geometrically arranged and interconnected to a microcomputer that interprets analog signals, to obtain the detection of the tire.

Claims

1. A tread or tire detection arrangement (1) for the classification of vehicular traffic, comprising: a cabinet (2) that houses a plurality of sensing units (6); characterized in that each one of the sensing units (6) is formed by a magnet (3) and a Hall effect sensor (4).

2. The arrangement according to claim 1, characterized in that each of said Hall effect sensors (4) are connected to an analog bus (5) that transmits the signals emitted by each sensor (4) to a signal conditioning interface (12) that injects the conditioned signals to a microcontroller (7); said interface (12) and said microcontroller (7) also being contained within the cabinet (6); and a multi-pair cable (8) that electrically feeds the arrangement (1) and transmits the signals generated by the microcontroller (7) to a remote processing terminal.

3. The arrangement according to claim 2, characterized in that all the elements (3; 4; 5; 7; 12) contained within the cabinet (2) are embedded in epoxy resin (9).

4. The arrangement according to claim 2, characterized in that the cabinet houses 8 to 16 sensing units (6).

5. The arrangement according to claim 2, characterized in that the cabinet has a length that varies from 1.50 m to 2.20 m.

6. The arrangement according to claim 2, characterized in that the magnets (3) are made of Neodymium N45.

7. The arrangement according to claim 2, characterized in that the magnets (3) have sizes 30×20×10 mm.

8. The arrangement according to claim 2, characterized in that said cabinet (2) is made of aluminum, has a thickness of 1.5 mm.

9. The arrangement according to claim 2, characterized in that said cabinet (2) measures 1500 to 2400 mm long, 25 mm wide and 25 mm high.

10. The arrangement according to claim 2, characterized in that the sensing units are located inside the cabinet with a separation of 150 mm from each other.

11. The arrangement according to claim 2, characterized in that it comprises two opto-coupler transistors to generate opto-coupled ON/OFF outputs.

12. The arrangement according to claim 11, characterized in that the multipair cable (8) is 4 pairs of the FTP (Foil Twisted Pair) type Category 6.

13. The arrangement according to claim 12, characterized in that a first pair (8A) of the multi-pair cable (8) supplies the sensing units (6), the conditioning unit (12) and the microcontroller (7), with a supply voltage, a second pair (8B) communicates data to and from the remote terminal by EIA RS485/232 or USB protocol; a third pair (8C) works as an ON/OFF output for indication of the presence of a single wheel and a fourth pair (8D) works as an ON/OFF output for an indication of the presence of a double wheel.

14. The arrangement according to claim 13, characterized in that each of the third (8C) and fourth (8D) pairs connect to an opto-coupled output.

15. The arrangement according to claim 14, characterized in that each of the third (8C) and fourth (D) pairs are connected to an intermediate micro-relay to provide dry contact signal.

16. The arrangement according to claim 13, characterized in that the supply voltage is 12 VDC.

17. The arrangement according to claim 2, characterized in that said conditioning interface (12) comprises low-pass filters and level conditioners (21; 24).

18. The arrangement according to claim 2, characterized in that said microcontroller comprises an A/D converter (26) that converts analog signals to digital signals and a CPU (29) that processes the signals received from said A/D converter (26) by means of resident digital processing software (27).

19. The arrangement according to claim 2, characterized in that in the absence of a radial tire (16) on the sensing arrangement (1), the sensing units (6) detect constant magnetic field lines (14), whereby the output signal in the signal pairs (8B; 8C; 8D) of the multipair cable (8) is null; and with the presence of a radial tire (16) on the sensing arrangement (1), the sensing units (6) detect variations in the magnetic field (15) whereby the output signal in the signal pairs (8B; 8C; 8D) of the multipair cable (8) is an activating one.

20. The arrangement according to claim 2, characterized in that, the microcontroller calculates the time that the vehicle's patch or tread remains on the sensor (dt0), 7 to determine how many dt0 units the next axis is located, and this dt0 unit is multiplied by a factor K=1, 2, 3, . . . 6, K*dt.sub.0 to obtain the time in which a new axis is expected (dt1) and, if this detection occurs within the dt1 interval, the formation is configured as a tandem axle; if another axis is received again within the time dt1, a tridem axle is formed; with which different formations are configured according to their axle configuration.

21. The arrangement according to claim 2, characterized in that multipair cable (8) transmits the signals generated by the arrangement to a remote terminal (not shown in the figures) wherein they are processed to allow full management of vehicle control.

22. The arrangement according to claim 2, characterized in that said remote terminal is a tablet, a desktop PC or a dedicated terminal for receiving data.

23. The arrangement according to claim 2, characterized in that said terminal re-transmits the data wirelessly via wired internet, WIFI or GSM to process the data in a remote computer center.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0068] FIG. 1 shows a known device that is used in statistical control in the determination of speed and length.

[0069] FIG. 2 shows another known device that is made up of contact (switch) and loop wheel sensors, classifies by number of axles, single and dual, and it does so at low speed.

[0070] FIG. 3A presents an example of a known device designed for a low or high speed single lane.

[0071] FIG. 3B shows a photograph of a known contact (switch) device and one according to the present invention to make comparative tests on a toll road.

[0072] FIGS. 3C and 3D show photographs of the device of the present invention installed in a toll station.

[0073] FIG. 4 presents a known arrangement suitable for being used on multiple lanes.

[0074] FIG. 5 shows a side view of the device of the present invention.

[0075] FIG. 6 shows a cross-sectional view of the sensor installation of the present invention.

[0076] FIG. 7 shows a side cutaway view of the internal diagram of the sensor of the present invention.

[0077] FIG. 8 shows a detailed cross-sectional view of the sensor of the present invention.

[0078] FIG. 9 shows a functional block diagram of the detection system of the present invention.

[0079] FIG. 10 presents the arrangement of the present invention detecting the passage of a single wheel.

[0080] FIG. 11 shows/presents the arrangement of the present invention detecting the passage of a double wheel.

[0081] FIG. 12 shows the method of detecting tandem, tridem axle train formations.

[0082] FIG. 13 shows in detail the operation for the detection of axle train formations.

DETAILED DESCRIPTION OF THE INVENTION

[0083] The present invention is based on the detection of radial tires, that is, with metal treads, therefore, it is not suitable for detecting the passage of non-radial tires, that is, “biasply” tire with Nylon tread. However, the inventors have concluded that this does not pose any practical disadvantage since the use of non-radial or “biasply” tires with Nylon tread does not have a major impact on the tire market compared to radial wheels.

[0084] To justify this, a market research has been requested on the percentage of radial and non-radial or “biasply” tires in different countries of the world, wherein it is of interest to apply this technology, and in a document by the consulting firm Grand View Research®, the market penetration percentages for radial and biasply tires for various countries in the world can be seen. Table 1 shows the results for some countries of interest.

TABLE-US-00001 TABLE 1 Country Vehicle % biasply % radial USA For passengers 0.0 100.0 Light utility 1.0 99.0 Heavy utility 2.0 98.0 Two-wheeled 9.5 90.5 Mexico For passengers 2.0 98.0 Light utility 21.0 79.0 Heavy utility 30.0 70.0 Two-wheeled 24.0 76.0 Great Britain For passengers 0.0 100.0 Light utility 2.5 97.5 Heavy utility 5.5 94.5 Two-wheeled 25.0 75.5 Germany For passengers 0.0 100.0 Light utility 1.5 98.5 Heavy utility 5.0 95.0 Two-wheeled 20.0 80.0 France For passengers 0.0 100.0 Light utility 6.0 94.0 Heavy utility 67.0 33.0 Two-wheeled 22.0 78.0 Italy For passengers 0.0 100.0 Light utility 2.5 97.5 Heavy utility 5.0 95.0 Two-wheeled 8.0 92.0 Spain For passengers 0.0 100.0 Light utility 3.0 97.0 Heavy utility 6.0 94.0 Two-wheeled 12.0 88.0 China For passengers 0.0 100.0 Light utility 4.0 96.0 Heavy utility 5.0 95.0 Two-wheeled 28.0 72.0 Japan For passengers 0.0 100.0 Light utility 4.0 96.0 Heavy utility 6.0 94.0 Two-wheeled 20.0 80.0 Brazil For passengers 1.0 99.0 Light utility 40.0 60.0 Heavy utility 65.0 35.0 Two-wheeled 25.0 75.0 Argentina For passengers 4.0 96.0 Light utility 45.0 55.0 Heavy utility 67.0 33.0 Two-wheeled 22.0 78.0 Colombia For passengers 3.0 97.0 Utility 70.0 30.0 Two-wheeled 24.0 76.0 Chile For passengers 5.0 95.0 Utility 68.0 32.0 Two-wheeled 27.0 73.0

[0085] The equipment of the present invention does not contain moving parts nor does it require pressure deformation to detect the wheel, thus extending its useful life. The invention is a development integrated by hardware and software, electronic control devices, signal analysis and communications.

[0086] Its technical object is the measurement by Hall sensors of the variation of a magnetic field caused by a magnet when approaching the metallic tread that radial tires have, for the measurement and classification of traffic as a wheel counter device.

[0087] The Hall Effect sensor uses the Hall Effect to measure magnetic fields or currents or to determine the position thereof. If current flows through a Hall sensor and approaches a magnetic field that flows in a vertical direction to the sensor, then the sensor creates an output voltage proportional to the product of the magnetic field strength and the current. If both the magnetic field strength and the current are known, then the Hall sensor can be used as a metal detector. As a position sensor or detector for magnetic components, Hall sensors are especially advantageous if the variation in the magnetic field is comparatively slow or zero. In these cases the inductor used as a sensor does not provide a relevant induction voltage.

[0088] The application of the invention is applied to traffic control, volume measurement, classification of categories for the toll collection at toll stations and free flow.

[0089] The device of the present invention is capable of detecting single and dual wheels (axles) in a single device, involving simple installation and having long useful life.

[0090] The material with which it is built has a resistance with characteristics similar to the pavement in which it is installed, without suffering deformations resulting from the pressure exerted by the tires on the sensor.

[0091] Embedded in rigid or flexible pavement using epoxy component sealants, the magnetic variation detection mechanism of the present invention allows wheels to be detected at high speed pitch.

[0092] The reduced size of the device of the present invention facilitates installation, in a small cut of few millimeters. In a preferred embodiment the volume occupied by the sensor device is 30 mm×30 mm, 30 mm×1500 mm, or 2400 mm in length, according to the application.

[0093] The device of the present invention works embedded in the pavement and leveled with it, it does not present edges that may cause impacts on the tires.

[0094] Its visibility after being installed is similar to a sealing of a pavement expansion joint, being imperceptible for circulation. See FIGS. 3B, 3C and 3D.

[0095] Construction details: FIG. 5 shows a side view of the sensor arrangement of the present invention and it is observed that it has a rectangular parallelepiped shape and it is observed the power, digital output and communication cable 8 connected at one of its ends. In a preferred embodiment, the cabinet 2 has the following measurements L=1500-2400 mm; W=25 mm; H=25 mm, but these measurements may vary according to the need of the installation (See FIGS. 7 and 8).

[0096] In FIG. 6 it is observed that the sensing arrangement 1 is embedded and fixed inside the pavement 10 by means of an epoxy adhesive 13.

[0097] FIG. 7 shows that the sensing arrangement is contained within a cabinet 2 which in a preferred embodiment may be made of “U” type aluminum and may be 1.5 mm thick. Inside the cabinet there is a line of magnets 3, geometrically arranged together with the unipolar Hall Effect sensors 4, connected to the analog bus 5, and this bus to the electronic signal conditioning interface 12 that is connected to the microcontroller 7; the entire system has communication, digital outputs and power supply via the multi-pair cable 8.

[0098] Each pair of sensor 4 and magnet 3 is a sensing unit 6, which are the basic elements for detecting the metallic tread of the tire. In a preferred implementation, the magnets 3 are of Neodymium N45 with dimensions 30×20×10 mm and the Hall effect sensors 4 make up the sensing units 6, which can vary from 8 to 16 units depending on the length sought. In a preferred implementation, the Hall Effect sensors are unipolar Hall Effect sensors, proportional to the magnetic field flow of the S pole, specially designed with precision for positioning and angular movement, with a very good sensitivity and dynamic range 200 mV/mT, 20-mT.

[0099] The preferred distance F between sensing units 6 is 150 mm, discriminating single wheels with the excitation of one or two sensing units 6, for tires from 120 mm to 240 mm and the excitation of 3 or more sensing units 6 for dual or wide wheel. See FIGS. 10 and 11.

[0100] Cable 8 is a multipair type of 4 pairs FTP (Foil Twisted Pair) Category 6, which can be up to 300 m in length, where each pair fulfills the function of: 8A: power supply of the arrangement with 12 V.sub.DC, 8B: for communication, means for carrying data communication protocol EIA RS485/232 or USB output, 8C: ON/OFF opto-coupled output indicating single wheel detection, 8D: ON/OFF opto-coupled output indicating dual wheel detection. To provide opto-coupled outputs the device of the present invention comprises a pair of output opto-coupler transistors (not shown in the figures). For replacements of existing arrangements the outputs can be optionally connected to external relays to provide dry contacts.

[0101] FIG. 8 shows a front cross section of the elements of the arrangement. The thickness of the cabinet 2 walls of approximately 1.5 mm is observed. The position of the magnet 3, the hall effect sensor 4, connected by 11 to the analog bus 5, which receives the signals from each Hall effect sensor 4, and interconnects to the interface 12 and is connected to the microcontroller 7; the entire set embedded in epoxy resin 9.

[0102] FIG. 9 shows two sensing units 6, each connected by 11 to the analog data bus 5, which carries the analog electrical signal from each sensing unit to signal conditioning interface 12, consisting of low-pass filters and level conditioners 21 and 24, with their outputs 22 and 25 connected to the inputs of the A/D converter 26 of the microcontroller 7.

[0103] The connectivity of the sensing arrangement 1 with the outside is through the multi-pair cable 8, according to the defined functions of each pair 8A-8B-8C-8D. Through the multipair cable 8, the signals generated by the arrangement are transmitted to a remote terminal (not shown in the figures) in which they are processed to allow full management of vehicle control. The remote terminal can be a tablet, a desktop PC or a dedicated terminal for receiving the data to re-transmit it wirelessly via wired internet, WIFI or GSM to process the data in a remote computer center.

[0104] The number of sensing units 6 can range from 8 to 16 modules, varying the length of the sensor from 1.50 m to 2.20 m. See FIG. 5.

[0105] All sensing unit modules 6, microcontroller 7 and their interconnections housed in containment cabinet 2, are embedded in epoxy resin 9, with optimal dielectric properties and mechanical resistance to traction and compression. See FIG. 3C.

[0106] The containment cabinet 2 of the arrangement is a “U” profile, preferably 1.5 mm thick and preferably with the measurements already mentioned above.

[0107] Operation

[0108] FIG. 10 shows that the passage of a radial tire 16 over the sensing arrangement 1 modifies the distribution of the field lines and the intensity of the magnetic field 15, which closes the magnetic circuit through the metal mesh of the tire, generating variations in the sensing units 6A involved.

[0109] In this FIG. 10 it is observed that, when there is no presence of radial tire 16 on the sensing arrangement 1, the sensing units 6 detect constant magnetic field lines 14, remaining in an idle or non-detection state.

[0110] FIG. 9 shows a detail of both operating conditions 14 and 15. For the case of idle state 14 the sensing unit 6 remains constant, but the analog signal of the Hall sensor 4 has voltage variations that range between maximum and minimum or off-set values 20 of the system, without exceeding the parameters set as the detection threshold.

[0111] The case 15, in the presence of a radial tire, the sensing unit 6, generates variations in the Hall sensor 4, higher than the voltage values set as parameters, producing a detection 23.

[0112] FIG. 9 shows how these variations 20 and 23 enter the analog signal conditioning electronic interface 12. This interface is made up of 8 or up to 16 passive filters, low passes, level conditioners 21-24, one for each sensing unit 6 of the sensing arrangement 1. The outputs of these filters 22-25 are connected to the inputs of the A/D converter 26 of the microcontroller 7.

[0113] The inputs of the A/D converter 26 of the microcontroller 7 read the conditioned analog signals 22-25 and the CPU 29 executes the digital conversion process through the digital signal processing software 27 resident in the microcontroller 7.

[0114] The result of the digital signal processing 27 shall indicate which of the sensing unit or units 6 has been activated, executing a software procedure that activates the software protocol, which sends the position data of the sensing unit or units 6 and the number of sensing units 6 being activated, by means of 28 to 8B, on an EIA RS485/232 protocol or USB output, thus communicating the position of the tread of the wheel, single wheels and double wheels (width).

[0115] The 2 potential-free ON/OFF contact outputs 8C and 8D (FIG. 7) are useful because they allow the arrangement of the present invention to be used as a direct replacement for existing contact (switch)—type systems, piezoelectric sensor, pneumatic sensor, fiber optic, etc. For example, FIG. 2 shows in an equipment of the prior art, the use of 3 axle counters each with on/off contact (switch) outputs that can be converted, by replacement by the equipment of the present invention, into a single counter (See FIG. 3), receiving the same contact (switch) type signals from this equipment.

[0116] The advantage of having various output signal protocols is that it allows integration into control systems developed by third parties, taking into account that this equipment is part of vehicle traffic and toll management systems.

[0117] FIG. 11 shows the activation of the sensing units 6A by the tread of dual wheels 17.

[0118] FIG. 12 shows the single axle 1, tandem 2, tridem 3 axle formations and the time differentials dt.sub.0 of one wheel and dt.sub.1 between wheels.

[0119] In FIG. 13 the differential dt.sub.0 shows the time that the patch or tread of the vehicle remains on the sensor, this time dt.sub.0 is the one that elapses between the beginning and the end of the tread of the wheel and is calculated by the microcontroller 7 to determine how many units dt.sub.0 the next axle is.

[0120] This unit dt.sub.0 is multiplied by a factor K=1, 2, 3, . . . 6, K*dt.sub.0=dt.sub.1, (FIG. 12), determining dt.sub.1 as the time in which a new axle is expected, if this detection occurs within the range dt.sub.1, the formation is configured as a tandem axle, if another axle is received again within the time dt.sub.1, a tridem axle is formed.

[0121] In this way, different formations are configured according to their axle configuration.