FR2549625A1 - Device for classifying vehicles travelling on a roadway into categories. - Google Patents

Abstract

Device for classifying vehicles on a roadway into categories taking account of the number of axles of the vehicle and of the distance between axles, using a linear sensor 3 perpendicular to the roadway. The sensor used permits very good measurements of time by virtue of the quality of its signal, the presence of the vehicle is determined by an induction loop 2. Device using various sensors and variants of electronic systems.

Description

It is known to use tubes, piezoelectric or triboelectric sensors for road counting of vehicle axles, measurement of vehicle speeds ...

The object of the present invention is to determine the class of the vehicle by associating a linear sensor perpendicular to the roadway with an electronic assembly measuring the inter-axle distances and comparing them with each other. It is thus possible, to determine with very good accuracy, the type of vehicle according to the European classification table (Table 1). The electronic system can be realized either in wired logic, or in digital system using a calculator, micro-calculator or integrating a microprocessor.

The distance between the axles will be measured by measuring the times between the passage of the different axles in one place; it is therefore essential to carry out the measurement in an area where the vehicle speed is constant. The measurement of the times between axles must also be very precise; a certain number of sensors or sensor installation techniques will therefore have to be rejected for such a system:
- pneumatic tube
- induction loop
- photoelectric cell or optical system
due to the existence on some vehicles
wheels of different diameters,
Two sensors will be recommended for this type of measurement
- piezoelectric sensor by triggering the measurements
of time on the falling edge of the signal like
indicated at 1 in Figure 2.

- PTOSE dielectric coaxial cable with small diameter
also synchronizing the measurement on the forehead
descending signal.

The following example makes it easier to see the interest of the system and its mode of operation.

The measurement station defined in Ligure 3 includes the following elements for each traffic lane - a magnetic loop (2) to determine the presence
of a vehicle and therefore the start and end of the vehicle.

- a piezoelectric or PTFE coaxial sensor (3)
perpendicular to the traffic axis (4)
all the sensors are connected to the electronic system (5)
which includes the detectors and the measurement unit and comparai
its times.

The system (5) will be constituted as follows (ig.6):
* a presence detector (16) connected to the electro loop
magnetic (2)
* a detector (17) for piezoelectric sensor or for
coaxial cable (3)
* a system (18) for measuring and recording dry times
trimming the axles and axle counting
* a comparator of these times between them and with a
reference table (19)
* the detector (16) determines the presence of the vehicle (9)
by its state (1) in Figures 3 and 4; during the presence
of the vehicle, the piezoelectric detector (17J determines
in (22) If the axle weight is greater than a threshold
given adjustable or not, and,
supplied in (8) a calibrated pulse synchronized on the
zero of the falling edge of the piezoelectric signal (7).

* the system (18) measures the times between the signals
supplied by the detector (17) and address the values thereof
to the system (19) which compares them.

The example given in FIGS. 4 and 5 illustrates the case of two heavy goods vehicles with 4 axles but of different classes with the recognition mode carried out by the system which is the subject of the present invention.

- in the first case, the time (11) is greater than the time (10)
and the time (12) less than the time (11); it is a
vehicle of the "heavy goods" class (4) according to table (i) - in the second case, the time (11) is less than the time (10)
and the time (12) greater than the time (11); the vehicle is
of the "heavy goods" type (5) according to table (1).

The axle weight criterion will only apply for the discrimination of vehicles with 2, 3 or 4 axles which can be: - 2 axles: motorcycle, car, heavy goods vehicle - 3 axles: car with trailer or heavy goods vehicle - 4 axles: car with trailer or truck
The two cases given above by way of example, can be generalized in table -7- where the categories and criteria used for classification appear.

Another type of table (8) can be used.

Claims (3)

1 / electronic vehicle classification device  into categories, characterized in that the distribution  axle geometry is given by the determination  and comparing the transit times of the different  axles, in a single line perpendicular to the roadway  materialized by a coaxial lizoelectric sensor  linear, implanted in the pavement and IournissaLt a  synchronized timing signal on the descending Iront  the sensor signal; the axle load being determined  born by the amplitude of the said signal. 2 / device according to claim 1, characterized  in that the piezoelectric sensor is replaced by  a coaxial cable with P T F E insulation of large diameter. 3 / device according to claim 1 or 2, characterized  in that the processing and comparison of timeframes is  wired logic or programmed system.