LT6678B - Method for fast determining of vehicle movement speed and device with amr sensors implementing it - Google Patents

Abstract

When measuring the vehicle speed with two magnetic sensors, the time difference between dependencies measured by two different sensors (magnetic signatures, signatures) is determined. The higher the number of points in the signature, the more accurate information can be obtained from measurements. On the other hand, a high number of points lengthens the processing time and increases the energy consumption for computations. When it is necessary to accurately identify a vehicle that exceeds the set speed, the data must be processed extremely fast to allow the capture camera (or other vehicle identification means) to capture the offender. This invention provides a new fast method for determining the speed and device implementing it. The method for determining the speed uses the difference of “mass centres” as the initial information for computing the cross-correlation coefficient. Then, the cross-correlation coefficient maximum is searched using a set of shifts, the centre of which is the difference of “mass centres”. The computation method provided not only shortens the computation time, but also allows more efficient use of the energy used by the speed meter .In addition, using two speed meters (having vehicle identification means) arranged at a known distance, the average vehicle speed on the stretch between these two meters can be determined.

Description

TECHNICAL FIELD

The present invention relates to the field of speed measurement of land vehicles, and more particularly to the determination of speed using a number of magnetic sensors located in the vicinity of moving vehicles and calculating the time difference (delay) in the arrival of the signal in different sensors. A new way of calculating the difference in the time of onset of signals is described, which reduces the computation time and allows more efficient use of energy.

TECHNICAL LEVEL

This description provides a new way of calculating the speed of land vehicles using AMR sensors and a device implementing that method. At least two AMR sensors (at a certain, known distance from each other (eg 20-30 cm)), which measure the changes in the Earth's magnetic field over time (magnetic signatures, signatures), shall be placed on the road surface or in other places close to passing vehicles ) while the vehicle is moving above / near the AMR sensors. Measuring the time difference between the time dependencies of the magnetic field measured by different sensors, the vehicle speed is determined. The more points a signature has, the more accurate the information is from the measurement, while the large amount of data increases the processing time and consumes more energy. Controlling traffic flows requires rapid measurement of vehicle speed, fast data processing and transmission without sacrificing information quality.

This description introduces a new way to quickly calculate a vehicle's speed. Reducing the speed from 50 to 1000 times the computation speed allows the use of the difference of mass centers in the calculation of the maximum of the correlation function. From the signatures of both AMR sensors the mass centers J? I and R2 are calculated. The calculated difference between the mass centers 7? I and Ri is used as the initial difference to calculate the correlation coefficient between the signatures. Afterwards, the maximum of the correlation coefficient is searched using the set of displacements /? 2 - /? Ι ± δ. 2δ is the width of the maximum search area. In this way, the computationally correlation-intensive computation is performed only at points in the 2δ interval.

The new method of calculation is adapted to the measurement of average speed over a given section of the road using two gauges at a known distance from each other, using technical means of vehicle identification.

Patent document US6208268 (B1) (published March 27, 2001) provides a similar system for determining vehicle speed: two magnetic sensors are positioned along the vehicle's motion direction, captures the change in magnetic field, compares the difference in time measured by different sensors, speed. The quoted document provides a simple way of calculating speed without estimating the time it will take the calculator to calculate the speed of the vehicle. Nothing is said about the efficient use of energy for computing. It is unclear whether the method presented is sufficiently accurate or the calculation is adequate to reliably determine the velocity with an acceptable error.

US2013057264 (A1) (published March 7, 2013) discloses a similar method of determining the speed of a vehicle using magnetic sensors, the magnetic signature (signature) they generate, and the time counting between signatures generated by different sensors. The paper presents a calculation method using Anderson's function, calculating the correlation between signals. The document does not provide calculation speed data, but it is clear from the calculation method that the calculation method is not intended for the rapid processing of large quantities of measurement data while maintaining the speed measurement efficiency.

The following disadvantages can be summarized in the present state of the art documents:

- provides a method of calculation that does not estimate large amounts of data and the time it takes to process such amounts; not suitable for fast processing of measurement data;

- the method of measurement and calculation does not ensure acceptable speed measurement errors;

- the cited documents do not mention the possibility of calculating the average speed of a vehicle over a certain length of road of known length;

- nothing is mentioned about energy efficiency.

The technical solution presented in this description does not have the drawbacks listed above.

THE SUBSTANCE OF THE INVENTION

When measuring the speed of vehicles with two magnetic sensors, the time difference between the measured dependencies (magnetic signatures, signatures) of the two different sensors is determined. The higher the number of dots in a signature, the more accurate information can be obtained from measurements. On the other hand, a large number of pixels increases the processing time of the data and increases the amount of energy used for calculations. When it is necessary to accurately identify a vehicle exceeding a set speed, the data must be processed extremely rapidly so that the imaging camera (or other means of identifying the vehicle) can capture the offender.

This description provides a new rapid method of speed determination and a device for implementing this method. The velocity estimation method uses' the difference between the centers of mass as the initial information for calculating the correlation coefficient between them. The maximum of the correlation coefficient is then searched using a set of displacements whose center is the 'difference of the centers of mass. This calculation not only shortens the computation time but also allows for more efficient use of the energy used by the speedometer.

In addition, the use of two such speedometers (having vehicle identification means) at a known distance allows the average speed of the vehicle to be determined over the distance between the two.

PREFERRED EMBODIMENTS

There are many technical tools used to measure the speed of land vehicles; including one way to determine vehicle speed using magnetism phenomena. One way to determine speed is by using AMR (Anisotropic Magnetoresistive) sensors. AMR sensors are placed near moving vehicles, e.g. can be placed on the road, under the pavement, or near the lane. When a vehicle containing steel interacting with a magnetic field appears above / near the sensors, the Earth's natural magnetic field is distorted in the vicinity of the sensor. AMR sensors measure the change in the Earth's magnetic field. If more than one AMR sensor is positioned along the direction of vehicle movement, the vehicle in motion shall first change the magnetic field measured by one AMR sensor, followed by the magnetic field measured by another AMR sensor (which is in the vehicle's direction of motion behind the first AMR sensor).

The time dependence of the magnetic field change of the same vehicle on the different sensors is similar, so knowing the distance between each of said AMR sensors and determining the time difference between the measured dependencies can determine the vehicle speed, in some cases the vehicle length , other settings.

The magnetic sensor transforms the time dependence of the magnetic field in three-dimensional space into an electrical signal. The higher resolution (i.e., the number of dots per unit of time) of the aforementioned dependencies (or signal, signature, signature) allows for a more accurate determination of the vehicle speed and other parameters. However, the higher resolution i.e. the larger the amount of data, the computing hardware processing that data will be loaded. Data processing requires more time, and if vehicle speed measurement is used to detect and capture (for example, taking photos) speeding vehicles, the long processing time may cause the offender to be far from where the camera can be captured.

The terms "signal,, .signature," signatures used in this description refer to the change in time of the magnetic field and / or its corresponding electrical parameter over time.

The present invention provides a way to reduce the amount of computation efficiently and without losing the required information, so that data processing (e.g., peak-to-peak computation) is performed faster.

One of the known ways of calculating the difference in the onset of two signals is to compute the correlation between them. In the case of the present invention, the scope of the computation of the intercorrelation function is reduced by "utilizing the difference of mass centers in calculating the maximum of the intercorrelation function. The calculated difference of the centers of mass is used as the initial difference in the search for the peak location of the correlation coefficient between signatures.

The method of calculating a vehicle speed using AMR sensors of the present invention has the following steps:

- using at least two AMR sensors located on the road / in the pavement, alongside the moving vehicles and at a distance L in the direction of movement of the vehicles along the carriageway, continuously measuring in real time

Earth's magnetic field;

- as the vehicle travels above / near the sensor, the dependence of the Earth's magnetic field change over time (magnetic signature, signature) is recorded and data from at least two AMR sensors are stored in the microcontroller (or other computing device);

- calculating the Earth's magnetic field distortion modulus from the sensed x, y and z components of the Earth's magnetic field;

- calculate the mass centers 7? i and R2 of the magnetic signatures obtained from at least two AMR sensors:

NN

2Ą (n) n Σ ⁵ 2 ( ^π ) ^π d _n = ldn = l

2 Ą (n) Σ S ₂ («) n = ln = l where Si and S2 are discrete signal modules, N is the number of points depending on the threshold level. Threshold Level - Optionally sets a signal value from which it is assumed that the signal value exceeds the noise level from which all signal, signature values are used to achieve the calculation results.

- Calculate the difference between the mass centers of the magnetic signatures R2-R1.

- With this difference, the two signals are correlated between R2-R1S and R2-R1 + δ. δ - Half the search range.

- The difference between the two signals Δ corresponding to the maximum of the correlation coefficient of magnetic signatures is found.

- Calculation of vehicle speed

L

V = --A · where L is the distance between the sensors; Δ - time difference between 'magnetic signatures (as discrete references); ts is the duration between two adjacent counts.

The calculated difference between the mass centers 2? I and R2 is used as the initial difference to calculate the correlation coefficient between signatures. Afterwards, the maximum of the correlation coefficient is searched using the set of displacements-? 2-Τ? Ι ± δ. The width of the 2δ maximum search area. In this way, the computationally correlation-intensive computation is performed only at points in the 2δ interval.

If vehicle speed measurements are made to identify vehicles exceeding the speed limit at that location, then a vehicle identification method is required. The present invention provides a conventional means of identifying vehicles by capturing a vehicle registration number with video cameras. The imaging camera shall be positioned at a distance from the magnetic speed meters such that the speed-measuring device is capable of processing data intended to determine the speed of the vehicle and to transmit a signal so that the imaging camera is ready to record and capture the vehicle.

The method of determining the speed of vehicles described herein is implemented by known electronic computing means, as is conventionally provided with processor (s), microcontroller (s), or other computing means for performing logical operations; operative and / or continuous memory modules for storing data; means of communication for communication between internal elements and interfaces to external elements and other technical means specific to devices performing such or similar calculations. The part of the device that performs the measurement of the measured data is connected to the part of the device that performs the measurement of the change in the magnetic field of the Earth. The main component of this unit is magnetoresistive sensors; in this case AMR sensors are used. AMR sensors measure a three-dimensional magnetic field. The data measured by these are transmitted to the part of the device performing data processing via wired or wireless (eg radio) data transmission means.

Possible application of the present invention to the determination of average vehicle speed. In this embodiment of the invention, the instantaneous speed meters (having vehicle identification means) described are spaced apart from one another to calculate an average speed (e.g., 1 km). The first instantaneous speedometer in the direction of travel records the instantaneous speed, then technical means are used to accurately identify the vehicle (eg video camera). In one embodiment, said vehicle magnetic signature (signature) can be used to identify vehicles. The magnetic signature (in the form of an electrical signal) will be different for different vehicles; the shape depends on the amount of ferromagnetic materials, the shape, the magnetization of ferromagnetic materials in the vehicle, and other vehicle elements that cause the Earth's magnetic field to be distorted. A known method of accurately identifying vehicles by capturing state vehicle registration numbers by imaging cameras located outside the magnetic velocity sensors in the present invention in the direction of vehicle movement. The average speed of the vehicle between these two speedometers shall be calculated by detecting the vehicle at the first measuring point of the vehicle, then at the second measuring position and measuring the time taken by the vehicle to travel a certain distance between the first and second speedometers (known distance). . The magnetic signature of the speeding vehicle and the registered license plate number are transmitted to the speedometer below, thereby linking the two gauges to a common system for measuring average speed. The second gauge uses the magnetic signature (vehicle signature) of the vehicle to capture the correct vehicle using an image capture camera.

In order to illustrate and describe the present invention, the following is a description of the most preferred embodiments. It is not a detailed or restrictive description intended to determine the exact form or embodiment. The description above should be viewed as an illustration rather than a limitation. Obviously, many modifications and variations may be apparent to those skilled in the art. An embodiment is selected and described so that those skilled in the art will best understand the principles of the invention and their best practical application for different embodiments with different modifications suitable for a particular application or application. The scope of the invention is intended to be defined by the appended definition and its equivalents, in which all the foregoing terms have the widest possible meaning, unless otherwise stated.

Embodiments described by those skilled in the art may be made without departing from the scope of the present invention as defined in the following definition.

Claims (4)

DEFINITION OF INVENTION 1. The method of determining the vehicle speed using a gauge equipped with at least two AMR sensors shall include the following steps: - using at least two AMR sensors located on the pavement (sensors may be otherwise located near vehicles passing through (allowing the sensor to detect a change in the magnetic field) and at a distance L in the direction of vehicle movement along the carriageway, continuously that measure the Earth's magnetic field in real time; - as the vehicle travels above / near the AMR sensor, the Earth's magnetic field distortion, time dependence (magnetic signature, signature) is recorded, and at least two AMR sensors are recorded on the microcontroller (or other computing device), - calculating Earth's magnetic field distortion modulus from x, y and z components of Earth's magnetic field, measured by AMR sensors; characterized by the fact that - calculate the mass centers of magnetic signatures 2? 1 and Rr of at least two AMR sensors, - the difference between the mass centers Ri-R \ of the magnetic signatures, - having this difference correlates both signals at a selected interval; - the difference between the two signals corresponding to the maximum correlation coefficient of the magnetic signatures is found, - calculation of vehicle speed. 2. a device for determining the speed of the vehicle using the method of determining speed according to claim 1. 3. The device for determining vehicle speed according to claim 2, characterized in that it has technical means for identifying the vehicle, such as a video capture camera. 4. The device for determining vehicle speed according to claim 3, characterized in that the device is adapted to determine the average speed of the vehicle using two such devices at a known distance, at which the average speed of the vehicle is to be measured.