JPS646520B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle classification device, and more particularly to a vehicle classification device using a loop coil type vehicle sensor.

For example, on toll roads, tolls are determined by vehicle type, so it is necessary to determine the vehicle type.

Conventionally, pattern recognition using an optical system has been used to determine the type of car, but this method requires the use of a computer for processing, which is complicated, and requires cleaning the lens, which poses problems in terms of maintenance. It was hot.

In addition, two ultrasonic vehicle detectors are installed to detect the vehicle commander.
A method of determining the vehicle type based on the data obtained by determining the vehicle height has also been used, but ultrasonic waves are prone to errors due to fluctuations caused by wind and the like.

The present invention has been made in consideration of the above-mentioned conventional problems, and its object is to provide a device for determining the type of vehicle using a loop coil type vehicle sensor that does not have the above-mentioned drawbacks.

This invention will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of one example of a device for carrying out the present invention, in which 1 is a loop coil for vehicle sensing, and its short side is oriented in the direction of travel of the vehicle (indicated by 10). The long side is oriented perpendicular to the direction of travel of the vehicle. 2 is a light emitter, 3 is a light receiver, and the line connecting the light emitter 2 and the light receiver 3 is parallel to the right side 101 in the diagram of the loop coil 1, and the distance from this right side 101 is 1.5 m. Receiver 3
receives the light projected from the light projector 2 and converts it into an amount of electricity. 4 is an amplifier; 5 is a differentiating circuit; the output of the photoreceiver 3 is input to the amplifier 4; and the output of the amplifier 4 is input to the differentiating circuit 5. 6 is a vehicle sensor connected to the loop 1, 7 is a gate, and 8 is a Schmitt circuit.The output of the differentiating circuit 5 is input to the gate 7, and the output of the sensor 6 is connected to the Schmitt circuit by opening the gate 7. 8 is input. Note that 9 indicates a road, and arrow 10 indicates the direction of travel of the vehicle.

Experiments have shown that the inductance of a loop coil sensor changes in relation to the height of the bottom of a vehicle passing over it. For example, the floor height of a passenger car is lower than that of other vehicles, so when the floor or bottom of the passenger car is on the loop, the inductance of the loop coil is compared to when the floor of a large bus is on the loop coil. and grow bigger.
This invention utilizes the above phenomenon to distinguish large buses and large trucks from other vehicle types. The distance between the line connecting the emitter 2 and the receiver 3 and the right side 101 of the loop coil 1 is the first distance when a passenger car or a small truck passes over the loop coil 1.
The distance may be selected to correspond to the position of the tip of the vehicle when the vehicle sensor 6 produces the maximum output or a value close to the maximum output.

Next, the operation will be explained.

FIG. 2 shows the amount of change in the inductance of loop 1 while the vehicle moves in the direction of arrow 10 in FIG. A graph showing changes in the output of the sensor 6,
A, B, C, and D show actual measured values when the sensing vehicle was a passenger car, a bus, an 11-ton truck, and a Datsun Truck (registered trademark), respectively.
However, the length of the loop coil 1 (dimension in the direction perpendicular to arrow 10) was 2.5 m, and the width (dimension in the same direction as arrow 10) was 0.75 m.

At the time marked t1 in A to D, the tip of each vehicle is at the loop coil 1.
Floodlight 2 located at a distance of 1.5 m from the front side 101 of
It is assumed that the line that connects the light receivers 3 has been reached. The highest value of the output of the sensor 6 occurs while the vehicle is on the loop coil 1. Assuming that the maximum value of the output of the sensor 6 while the passenger car passes by the loop coil 1 is 18 (hereinafter these numbers are used as comparison values) as shown in A, then the tip of the vehicle is on the front side of the loop coil 1. Arrow 10 by 1.5m further than 101
The output of the sensor 6 is 16 when the vehicle reaches a position advanced in the direction of (hereinafter referred to as forward). As shown in Figure B, the maximum output from sensor 6 until the bus passes loop coil 1 is 10 (this number also applies to buses when the maximum output from sensor 6 for passenger cars is 18). (This is a number indicating the maximum value for.)
When this bus comes 1.5m in front of the loop coil 1, the output of the sensor 6 is 4. Similarly, as shown in C and D, for the 11-ton truck and the Datsuto Sun Truck (registered trademark), the output of the sensor 6 is 4.5 and 12.5, respectively, and the output of the sensor 6 is 4.5 and 12.5, respectively, when the sensor comes 1.5 m in front of the loop coil 1. The output of 6 is 4.5, 10.

In FIG. 1, when the vehicle is traveling in the direction of arrow 10 and comes to a position 1.5 m in front of loop coil 1, light receiver 3 generates an output signal, which is sent to differential circuit 5 via amplifier 4. join. Differentiating circuit 5 therefore produces a differential output, which opens gate 7. As shown in Figure 2, the inductance of loop coil 1 has changed even before the vehicle came 1.5m in front of loop coil 1.
An output is generated from the sensor 6 in accordance with the change. When the gate 7 is opened, the output of the sensor 6 is input to the Schmitt circuit 8 via the gate 7. Therefore, the Schmitt circuit 8 always receives the output of the sensor 6 when the vehicle comes 1.5 m in front of the loop coil 1. As shown in Figure 2, the ratio of the levels of these inputs is as follows: passenger car 16: bus 4: 11 ton truck 4.5: Datsuto Sun Truck (registered trademark) 10
It is. That is, compared to the output corresponding to a passenger car and a Datsun Truck (registered trademark), the output corresponding to a bus and an 11-ton truck is extremely small. Therefore, a threshold value is set in the Schmitt circuit 8 at a level lower than the output level of the sensor 6 corresponding to a passenger car and a Datsuto Sun Truck (registered trademark), but higher than the output level corresponding to a bus and an 11-ton truck. By doing so, the Schmitt circuit 8 outputs a high level "H" signal when a passenger car or Datsun Truck (registered trademark) is detected, and outputs a low level signal when an 11-ton truck or bus is detected. Generates “L”. These signals make it possible to distinguish between large vehicles such as buses and 11-ton trucks, and small vehicles such as passenger cars and Datsun Trucks (registered trademark).

In the above, 11 of the vehicles illustrated in Figure 2
The power curve of a Tonto Truck is generally similar to the power curve corresponding to a typical large truck, and the power curve of the Datsun Truck is generally similar to a power curve corresponding to a typical small truck.

In Fig. 2, the vertical axis indicates the inductance of the loop coil or the output of the sensor 6, which corresponds to the distance between the bottom or floor of the vehicle and the loop coil when the vehicle passes over the loop coil. The output from the sensor 6 changes; the output is small in the range where the bottom surface is high, and the output is large in the range where the bottom surface is low.

As can be seen from FIG. 2, there is not much difference in the maximum output of the sensor 6 for various vehicles between a bus, which is a large vehicle, and a Datsun Truck (registered trademark), which is a small vehicle. However, there is a large difference in the output of the sensor 6 when it comes 1.5m in front of the loop coil 1 between large vehicles (buses, large trucks) and small vehicles (passenger cars, Datsuto Sun Trucks (registered trademark)). . Therefore, according to the present invention, large vehicles and small vehicles can be accurately classified by determining the output level of the sensor 6 when the vehicle comes a certain distance from the leading edge of the loop 1.

The above-mentioned fixed distance can be arbitrarily set within a range that allows the type of vehicle to be discriminated based on the output of the loop sensor, which varies depending on the height of the bottom surface of the vehicle.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an example of a device for carrying out the present invention, and FIG. 2 is an output waveform diagram of a loop coil type vehicle sensor. DESCRIPTION OF SYMBOLS 1... Loop coil for vehicle sensing, 2... Emitter, 3... Light receiver, 6... Vehicle detector, 7... Gate, 8... Schmitt circuit, 101... Front side of loop coil 1.

Claims (1)

[Claims] 1. A substantially rectangular loop coil 1 installed on a road, with its long sides arranged in a direction perpendicular to the direction of travel of the vehicle, and its short sides arranged in a direction parallel to the direction of travel of the vehicle. a loop coil-type first vehicle sensor 6 that outputs a vehicle sensing output based on a change in inductance of the loop coil 1; and a front side 10 of the loop coil 1 in the vehicle traveling direction.
1, and a second vehicle sensor 2, 3 of a cut-off light emitting/receiving type is disposed a certain distance ahead of the loop coil 1, and the certain distance is the second vehicle sensor 2, 3 of a light emitting/receiving type that is disposed a certain distance ahead of the loop coil 1. The second vehicle sensor 6 is selected to have a distance corresponding to the tip position of the vehicle when the first vehicle sensor 6 produces the maximum output or near the maximum output, and further has a predetermined threshold value. a level discriminator 8 for discriminating the output level of the first vehicle sensor 6 and outputting a signal corresponding to a bus and a large truck or a signal corresponding to a passenger car and a small truck by discriminating the output level of the first vehicle sensor 6 at the time when the output signals of the first vehicle sensor 2 and 3 are generated; In preparation, the threshold value is higher than the output level of the first vehicle sensor 6 when the head of a bus or a large truck is detected by the second vehicle sensor 2 or 3, and A vehicle model using a loop coil type vehicle sensor, characterized in that the output level is lower than the output level of the first vehicle sensor 6 when the head is detected by the second vehicle sensor 2, 3. Classification device.