JPS6225240B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vehicle type classification device. Expressways and other toll roads have a system in place to collect tolls that vary depending on the type of vehicle, including large vehicles, small vehicles, buses, and trucks. Therefore, in order to automate toll collection, it is necessary to determine the type of vehicle. Vehicle type classification is often required when automatically managing, managing, or controlling vehicles, not only on toll roads. By the way, some devices that classify vehicle types use an optical system to capture the vehicle as an image and use pattern recognition to determine the vehicle type. There is a problem that maintenance is troublesome. In addition, two ultrasonic transducers are installed at a required height above the road surface at a required interval in the direction of travel of the vehicle, and the vehicle length is measured using the received signal from one ultrasonic transducer. There is a known method that measures vehicle height and classifies the vehicle type based on vehicle length and vehicle height (Special Publication No. 24161/1973). However, this device can only distinguish between large cars and small cars, and cannot distinguish between passenger cars included in small cars and small vehicles of other types. In addition, multiple small loop coils are placed at appropriate intervals along the direction of travel of the vehicle, and the length of the vehicle is detected based on the vehicle detection signal from each loop coil. A device for classifying vehicle types is also known (Japanese Patent Publication No. 49-29800), but this can only distinguish between large cars with a long length and small cars with a short length; Whether it is a passenger car, a small bus, or a small truck, they have approximately the same length, so it is impossible to distinguish only the passenger car from these small cars. In view of the above circumstances, it is an object of the present invention to provide a vehicle type classification device that can reliably distinguish passenger cars from other vehicle types. The vehicle type classification device according to the present invention includes a loop coil that is buried near the road surface and whose length is relatively short in the direction of vehicle travel compared to the width, and is placed at a position ahead of the loop coil in the direction of travel of the vehicle. This is a constant that detects when the tip of a passing vehicle reaches a position where the inductance of the loop coil, which changes as the vehicle passes, shows a larger value only in the case of a passenger car than in other vehicle types. a position detector, an inductance detection circuit that detects the inductance of the loop coil when a vehicle is detected by the fixed position detector, and an inductance detection circuit that discriminates the output of the inductance detection circuit at a predetermined level, and detects the inductance of the inductance detection circuit. The present invention is characterized in that it includes a level discrimination circuit that outputs a passenger car detection signal when the output exceeds the predetermined level. In this invention, since the floor height of a passenger car is extremely low compared to other types of vehicles, the influence on the loop coil is large, and as will be demonstrated in detail later, the front end of the vehicle is lower than the loop coil. Attention is focused on the fact that the inductance of the loop coil when the vehicle reaches a predetermined position in front of the vehicle in the direction of travel, that is, the inductance at a fixed position, becomes extremely large in the case of a passenger vehicle. This fixed position inductance is detected by the fixed position detector and the inductance detection circuit, and the detected inductance is discriminated at a predetermined level by the level discrimination circuit. It can even be distinguished from small cars other than passenger cars. Embodiments of the present invention will be described in detail below with reference to the drawings. In FIGS. 1 and 2, a long loop coil 1 is buried near the road surface at a location where the type of vehicle is classified in a driving lane between lane separation strips P on a road L. This long loop coil 1 is formed in a rectangular shape, and has a size corresponding to the floor shape of the large bus to be identified, and has a width S1 (in the width direction of the road L) of the vehicle. The length S2 is made longer in the direction of travel of the vehicle (the direction of travel of the vehicle is indicated by arrow W). In this example, the width S1 is 2.5 m and the length S2 is 12.0 m. In addition, a loop coil 2 having a shorter length S3 in the direction of travel of the vehicle than the width S1 is buried at the location where the long loop coil 1 is buried. The width of this loop coil 2 is the same as the width S1 of the long loop coil 1,
The length S3 is 0.75m. And this loop
A vehicle detector 5 is provided at a location separated from the coil 2 by a required distance S5 in the direction in which the vehicle travels.
In this example, the distance S5 is 1.5 m. As the vehicle detector 5, a photoelectric detector is used. Two ultrasonic transducers 3 and 4 are installed at a required height above the location where these loop coils 1 and 2 are buried, with a required spacing in the traveling direction of the vehicle. These transducers 3 and 4 transmit ultrasonic waves vertically downward toward the road surface, and receive reflected waves from the road surface or the vehicle. Since the transmitted ultrasonic waves and their reflected waves have an appropriate spread, the transducers 3 and 4 have a sensing range R, which is usually circular. In this example, the diameter of the sensing range R is 1.1 m. The distance S4 between the sensing range R of both transducers 3 and 4 is 6.25 m.
It is. As will be explained later, this distance S4 serves as a criterion for distinguishing long vehicles from short vehicles in identifying vehicle lengths. In addition, when determining the vehicle type based only on the length of the vehicle without measuring the vehicle height, the ultrasonic transducers 3 and 4 are installed above a point slightly deviated to the side from the driving lane, and the ultrasonic waves are emitted. The wave may be transmitted diagonally downward toward the driving lane. In FIG. 3, the long loop coil 1 is connected to an inductance detection circuit 11. In FIG. This detection circuit 11 detects a change in the inductance of the coil 1 that occurs when the vehicle passes above the long loop coil 1, and is composed of, for example, an AC bridge circuit with the coil 1 as one side.
The output signal of the detection circuit 11 is sent to the level discrimination circuit 12. As will be clear from what will be explained later,
The output of the detection circuit 11 becomes larger than that for other types of vehicles only when a large bus passes above the coil 1. The discrimination circuit 12 is the detection circuit 11
outputs a large bus detection signal when the output exceeds the required discrimination level. Loop coil 2 is also long loop coil 1
Similarly, it is connected to the inductance detection circuit 21. The output of this detection circuit 21 is sent to a level discrimination circuit 23 via a gate circuit 22. On the other hand, the vehicle detection signal of the vehicle detector 5 is transmitted to the differentiating circuit 51.
is input to the differential circuit 51, and its rising edge is detected by the differentiating circuit 51. The vehicle detector 5 outputs an "H" level vehicle detection signal while the vehicle passes through the location where the detector 5 is installed. When the frontmost part of the vehicle traveling in the driving lane reaches the installation location of the detector 5, the output of the detector 5 rises. At this point, a detection pulse is output from the differentiating circuit 51 and sent to the gate circuit 22 as a gate control signal. Sent. The gate circuit 22 opens its gate when the detection pulse is input from the differentiation circuit 51 and sends the output of the detection circuit 21 to the level discrimination circuit 23. The output of the inductance detection circuit 21 at the time when the vehicle is traveling along the driving lane toward the loop coil 2 and the foremost part thereof has advanced by a distance S5 from the loop coil 2 is taken out by the gate circuit 22 and sent to the level discrimination circuit. It will be sent to the 23rd. The inductance of the loop coil 2 when the frontmost part of the vehicle passes the loop coil 2 and reaches a point a required distance S5 away from it is called the fixed position inductance. This fixed position inductance is the gate circuit 22
This detection output is expressed by the output of the detection circuit 21 that is sent through the sensor, and as will become clear from what will be described later, this detection output shows a larger value only in the case of a passenger car than in other types of vehicles. The level discrimination circuit 23 outputs a passenger car detection signal when the output of the gate circuit 22 exceeds a predetermined discrimination level. The period generating circuit 30 defines an ultrasonic wave transmission period T, and outputs a pulse signal A having a constant period T and a constant width t, as shown in FIG. This pulse width t becomes the transmission width of the ultrasonic wave. Pulse signal A is sent to modulation amplification circuits 31 and 41. The modulation amplification circuits 31 and 41 modulate and amplify the pulse signal A with a signal having a frequency in the ultrasonic band, and output an ultrasonic transmission signal B. This ultrasonic transmission signal B is sent to the transducers 3 and 4 via limiters 32 and 42, respectively, and the ultrasonic waves are transmitted from the transducers 3 and 4 toward the road surface. When this transmitted ultrasonic wave is reflected by the vehicle or the road surface and returns, this reflected wave is received by the transducers 3 and 4, and is sent as an ultrasonic reception signal C to the limiters 33 and 4.
3, the waveform is shaped and amplified by the waveform shaping circuits 34 and 44, and then the vehicle detection gate circuit 3
5 and a vehicle detection gate circuit 45, a high vehicle detection gate circuit 46, and a low vehicle detection gate circuit 47, respectively. The time it takes for the reflected waves to be received after transmitting ultrasonic waves differs depending on whether the reflected waves are reflected by a high vehicle, a low vehicle, or a road surface. Low cars and road surfaces return quickly. As shown in Figure 2, a high vehicle detection zone Z1, a low vehicle detection zone Z2, and a vehicle detection zone Z3 are assumed above the road surface, and ultrasonic waves are reflected and received within each of these zones Z1 to Z3. In this case, these reflected waves are considered to be waves reflected from a high vehicle, a low vehicle, and a vehicle, respectively. The high vehicle detection zone Z1 is located above the low vehicle detection zone Z2, and the vehicle detection zone Z3 is located above both zones Z.
1, Z2 is included. High vehicle detection gate circuit 46
The gate of the low vehicle detection gate circuit 47 is opened in the time period T1 when the ultrasonic wave reflected from the high vehicle detection zone Z1 is received by the transducer 4, and similarly, the gate of the low vehicle detection gate circuit 47 is opened in the low vehicle detection zone Z2. The gates of both vehicle detection gate circuits 35 and 45 are opened in a time period T2 in which the reflected ultrasonic waves are received by the transducer 4, and the gates of both vehicle detection gate circuits 35 and 45 are opened in a time period T3 that includes both time periods T1 and T2. Gate control signals D, E, and F that control opening and closing of the gates of these gate circuits 35, 45 to 47 are output from a timer circuit (not shown) or the like that receives the pulse signal A as an input. If a received signal is input while the gate of the high vehicle detection gate circuit 46 is open, this signal passes through the gate circuit 46 and is output as a high vehicle detection signal. Similarly, low vehicle detection gate circuit 47
The received signal passing through becomes a low vehicle detection signal. Vehicles with a high vehicle height include large buses and large trucks, and when these vehicles pass below the ultrasonic transducer 4, a high vehicle detection signal is generated. Vehicles with low vehicle height include passenger cars, small buses, and small trucks, and a low vehicle detection signal is output when these vehicle types pass. The received signal that passes through the vehicle detection gate circuits 35, 45 while the gates of the vehicle detection gate circuits 35, 45 are open is sent to the AND circuit 40 as a vehicle detection signal. As mentioned above, both transducers 3,
4 are arranged at required intervals in the direction of travel of the vehicle, and the distance between the detection ranges R is S4.
Therefore, only when a vehicle whose vehicle length is longer than this distance S4 passes below both transducers 3 and 4, vehicle detection signals are simultaneously output from both gate circuits 35 and 45. And only in this case
An output is generated from the AND circuit 40, and this output signal becomes a large vehicle detection signal. Vehicle types with longer vehicle length than distance S4 include large buses and large trucks.
These vehicle types are detected by the output of the AND circuit 40. Figures 5 to 7 show the output of the inductance detection circuit when a passenger car, a large truck, and a large bus are driven on a road where square loop coils are buried and these vehicles pass over the loop coils. An example of experimental results is shown for varying the dimensions of the loop coil. All these experiments were carried out using the same width (S1=
2.5 m) loop coil, and its length S2 was changed. In addition, in each figure, graphs 1 and 2 were obtained by burying loop coils of different lengths in the same location, and the frequency of the current flowing through the loop coils was changed to avoid mutual influence. However, this frequency does not affect the output of the inductance detection circuit. Track data in TR, bus data in BU
, and the numbers for passenger cars are omitted. In Figure 5, A is the length S2
is a 3.0m loop coil, and B is 1.5m in length.
m loop coil. In both graphs, the magnitude of the output signal does not change much depending on the vehicle type. In Figure 6, A is S2
= 6.0m, and B uses a loop coil with S2 = 0.75m. It can be seen that with the loop coil of S2 = 6.0 m, the output when the bus BU passes is clearly larger than that of other vehicle types. Also, with a loop coil of S2 = 0.75m, the bus
The output for BU and track TR is somewhat small. In Figure 7 A, S2 = 12.0m loop.
Regarding the coil, the output in the case of bus BU is significantly larger than in other car models. This experimental result shows that if the length S2 of the loop coil is 6.0 m or more, large buses can be distinguished from other vehicle types by level-discriminating the output of the inductance detection circuit at an appropriate level.
FIG. 8 shows the relationship between the output of the detection circuit and its frequency for large buses and large trucks. In this data, width S1 is 2.5m, length S2
This is the result of an experiment on a 12.0m loop coil. It will be appreciated that large buses and large trucks can be clearly distinguished from the output level of the detection circuit. In this way, the length S2 is 6.0m
Using the above loop coil, it is possible to distinguish between large buses and other vehicle types (especially large trucks) from the output of the inductance detection circuit. This seems to be because the floor area is large and the floor height (distance from the road surface to the floor surface) is low, so the influence on the long loop coil is large, and the change in its inductance becomes large. FIG. 9 shows an example of experimental results obtained by determining changes in the output of the inductance detection circuit 21 when the vehicle passes above the loop coil 2 for various vehicles. The loop coil 2 used had a width S1 of 2.5 m and a length S3 of 0.75 m. In Figure 9, A shows data about passenger cars, B shows data about large buses, C shows data about large trucks, and D shows data about small trucks. The point in time when the front end of these vehicle types has advanced a distance S5 (1.5 m) from the loop coil 2 is indicated by the vertical axis Y, and the output of the detection circuit 21 at this point is LT. This value LT corresponds to the above-mentioned positional inductance. As is clear from this experimental result, the fixed position inductance detection output LT has a significantly larger value only for passenger cars than for other vehicle types. FIG. 10 shows the relationship between the fixed position inductance detection output LT and its frequency for passenger cars, large and small buses, and large and small trucks. These data were also obtained as a result of experiments with the loop coil 2 having the same dimensions as above and the distance S5. It is understood that passenger cars and other vehicle types can be clearly distinguished from the fixed position inductance detection output LT, and therefore, a passenger car detection signal can be obtained by discriminating the fixed position inductance detection output LT at a required level. Good morning. In this way, passenger cars can be distinguished from other types of vehicles by using a loop coil whose length is shorter than its width and by using its fixed position inductance. This is thought to be because the inductance is extremely low compared to the vehicle, so it has a greater effect on the loop coil than in other types of vehicles, and its inductance changes greatly. The above-mentioned large bus detection signal, passenger car detection signal,
The following table summarizes whether the high vehicle detection signal, low vehicle detection signal, and large vehicle detection signal are output for large buses, large trucks, passenger cars, and small vehicles other than passenger cars.

[Table] Large vehicles such as large buses and large trucks, and small vehicles such as passenger cars, small buses and small trucks,
They can be identified by the presence or absence of a vehicle height detection signal and/or vehicle length detection signal; among large vehicles, large buses and large trucks can be distinguished by large bus detection signals; among small vehicles, passenger cars and other vehicles can be distinguished. A small car can be identified from a passenger car detection signal. Therefore, by combining the large bus detection signal, passenger car detection signal, vehicle height detection signal, and vehicle length detection signal, it is possible to classify large buses, large trucks, passenger cars, and small vehicles other than passenger cars. Here, it is sufficient to have either a low vehicle detection signal or a high vehicle detection signal as the vehicle height detection signal. Furthermore, although it is possible to distinguish between large and small vehicles using either the vehicle height detection signal or the vehicle length detection signal, both of the above detection signals are used to compensate for errors caused by ultrasonic fluctuations, etc. It is preferable. A logical operation device 10 shown in FIG. 3 performs logical operation processing on a large bus detection signal, a passenger car detection signal, a vehicle height detection signal, and a vehicle length detection signal, and outputs a large bus detection signal, a large truck detection signal, a passenger car detection signal, and the like. It outputs a detection signal for small vehicles other than passenger cars, and uses a logic circuit consisting of an AND circuit, an OR circuit, a matrix circuit, etc., or a microprocessor. Arithmetic device 10
When a microprocessor is used as the period generating circuit 30, the microprocessor
And each detection gate circuit 35, 45-47 may be controlled. In the description of claim 1 defining this invention, the loop coil 2 corresponds to the loop coil of claim 1, and the vehicle detector 5 and the differentiation circuit 51 are fixed position detectors. The inductance detection circuit 21 and the gate circuit 22 correspond to an inductance detection circuit, and the level discrimination circuit 23 corresponds to a level discrimination circuit. In the above example, a photoelectric detector is used as the vehicle detector 5, but an ultrasonic transducer is also installed at a distance S5 from the loop coil 2 to detect ultrasonic waves reflected from the vehicle. It is also possible to detect a vehicle based on the loop coil 2, and in addition, a loop coil can be buried at a distance S5 from the loop coil 2, and the change in the inductance of this loop coil can be used to detect the vehicle. It can also detect vehicles. Further, it goes without saying that the dimensions of the loop coil 2 and the distance S5 between the loop coil 2 and the vehicle detector 5 are not limited to the above example, and the optimum values may be determined experimentally. Furthermore, the vehicle detector 5 includes a loop coil 2
may be installed at a distance S5 along the path of the vehicle. In this case, the inductance of the loop coil 2 when the last part of the vehicle passes the location of the vehicle detector 5 will be determined as the positional inductance. The ultrasonic wave transmission period T by the ultrasonic transducers 3 and 4 is selected to be, for example, about 60 ms. Therefore, ultrasonic waves are transmitted to one vehicle several to 10 times, and the vehicle detection gate circuits 35, 4 are transmitted each time.
A vehicle detection signal is output from 5. As shown in FIGS. 11 and 12, the vehicle detection gate circuit 3
Integral smoothing circuits 38 and 48 are provided at the subsequent stages of 5 and 45, respectively, and hold the vehicle detection signal for each cycle determined as vehicle detection to obtain integral smoothing outputs I and J corresponding to one vehicle, respectively. Good too. These outputs I and J are then sent to an AND circuit 40. If the length of the vehicle is longer than the distance S4, the outputs I and J overlap at a certain moment, so the AND circuit 40 outputs the large vehicle detection signal K at this time. An integral smoothing circuit is also provided at the subsequent stage of the high vehicle detection gate circuit 46 and the low vehicle detection gate circuit 47,
A high vehicle detection signal and a low vehicle detection signal corresponding to one vehicle may be obtained. Assuming that the speed at which a vehicle passes the point directly below the ultrasonic transducer 4 is constant, the longer the vehicle, the longer the time it takes to pass. can be distinguished. In FIGS. 13 and 14, an integral smoothing circuit 48 is provided after the vehicle detection gate circuit 45.
A vehicle length detection circuit 49 is connected to the subsequent stage. The vehicle length detection circuit 49 includes a timer circuit. This timer circuit starts its timing operation from the rising edge of the integrated smoothed output J, and is reset by the falling edge of the integrated smoothed output J. Then, after the start, the predetermined set time
If it is not reset before TA elapses, a large vehicle detection signal M is output. The ultrasonic waves transmitted from the ultrasonic transducer 4 are attenuated as they propagate, and the longer the propagation path, the greater the amount of attenuation. Therefore, the amplitude of the ultrasonic waves reflected and received by a vehicle with a low vehicle height is smaller than the amplitude of the ultrasonic waves reflected and received by a vehicle with a high vehicle height.
FIG. 15 shows a received signal of a reflected wave from a high car and a received signal of a reflected wave from a low car. By level-discriminating these received signals using an appropriate level N, high vehicles and low vehicles can be distinguished.

[Brief explanation of the drawing]

Figures 1 and 2 show the arrangement of the two loop coils and the ultrasonic transducer, Figure 1 is a plan view, Figure 2 is a vertical sectional view, and Figure 3 is a vehicle classification device. 4 is a time chart showing the output signals of each block shown in FIG. A graph showing the results of an experiment to obtain changes in the output of the inductance detection circuit when passing various types of vehicles. Figure 8 shows the relationship between the output of the inductance detection circuit and its frequency when using a long loop coil. FIG. 9 is a graph showing the results of an experiment to see changes in the output of the inductance detection circuit when various vehicles are run on the loop coil.
This shows that the magnitude of the fixed position inductance detection output varies depending on the vehicle type, and Figure 10 shows the relationship between the fixed position inductance detection output and its frequency for passenger cars, small and large buses, and small and large trucks. Graph, FIG. 11 is a block diagram showing another example of the vehicle length determination circuit, and FIG.
The figure is a time chart showing the output signals of each block shown in FIG. 11, FIG. 13 is a block diagram showing still another example of the vehicle length discrimination circuit, and FIG.
FIG. 15 is a time chart showing the output signals of each block shown in the figure, and a waveform chart showing another principle of vehicle height determination. 1... Long loop coil, 2... Loop coil, 3, 4... Ultrasonic transducer, 5... Vehicle detector,
10...Logic operation device, 11, 21...Inductance detection circuit, 12, 23...Level discrimination circuit, 22
...gate circuit, 35, 45...vehicle detection gate circuit, 46...high vehicle detection gate circuit, 47...low vehicle detection gate circuit, 49...vehicle length detection circuit, 51...differentiation circuit.

Claims (1)

[Claims] 1. A loop coil 2 which is buried near the road surface and whose length is shorter in the direction of vehicle travel than its width, and a predetermined position S5 ahead of the loop coil in the direction of travel of the vehicle. Detects when the tip of a passing vehicle reaches a position where the inductance of the loop coil, which changes as the vehicle passes, shows a larger value only in the case of a passenger car than in other vehicle types. fixed position detectors 5 and 51 for detecting a vehicle, inductance detection circuits 21 and 22 for detecting the inductance of the loop coil when a vehicle is detected by the fixed position detector, and an output of the inductance detection circuit at a predetermined level. A vehicle type classification device comprising: a level discrimination circuit 23 which discriminates the vehicle type and outputs a passenger car detection signal when the output of the inductance detection circuit exceeds the predetermined level. 2. The vehicle type classification device according to claim 1, wherein the fixed position detector is a photoelectric detector. 3. The fixed position detector is an ultrasonic transducer.
A vehicle type classification device according to claim 1. 4 the fixed position detector is a loop coil;
A vehicle type classification device according to claim 1.