JPS5825962B2 - Vehicle type identification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle type discrimination method capable of determining the type of vehicle.

In recent years, in traffic control, the necessity of traffic regulation and traffic control based on vehicle type, in addition to traffic volume and traffic speed, has been discussed.

Conventional vehicle detectors, such as ultrasonic detectors and loop-type detectors, are mainly used to detect the presence of a vehicle, and in order to detect the speed and type of vehicle, two detectors must be installed close to each other. Must be.

In addition, the above-mentioned loop type has to be buried in the road, which requires extensive construction work.

Furthermore, since the ultrasonic type uses intermittent oscillation, errors are likely to occur, which poses a serious problem in practical terms.

The present invention is a microwave Doppler radar set vehicle detector that is capable of identifying vehicle types.
The output from one sensor G can be used effectively.

Doppler radar is a radar that utilizes the fact that microwaves are irradiated onto an object to be detected, and the reflected waves undergo a frequency shift proportional to the speed of the object due to the Doppler effect, as shown in Figure 4. As shown in FIG.
5, the output of the microwave oscillator 22 is sent out from the antenna 24 via the circulator 23, the reflected wave from the object to be detected is received by the antenna 24, and the circulator 2
3, the signal is mixed with a part of the output of the microwave oscillator 22, and a Doppler signal is obtained from the detector 25.

The present invention will be specifically explained below.

Assume now that the l-axis 1 is located at the center of the lane on the road surface, and the d-axis 2 is located in the transverse direction.

A microwave Doppler radar transmitting/receiving antenna 3 is installed at a height h5 from the intersection of the l-axis 1 and the d-axis 2.

The directivity and mounting angle of the antenna 3 are determined so that the equal sensitivity pattern on the road surface by the antenna 3, that is, the vehicle detection area 4, is elongated toward the vehicle entrance side as shown in FIG.

Generally, when detecting the speed of a vehicle using a Doppler radar, let θ be the angle between the vehicle's direction of travel, the installation position of the antenna 3, and the straight line connecting the radio wave violation point, as shown in A in Figure 2.
Detection is performed for the actual speed ■.

Note that the specific angle θ can be detected when the Doppler signal level exceeds a certain value.

In other words, the speed information of the Doppler signal obtained as the vehicle advances, as shown in Figure 2, the detection speed decreases as the vehicle approaches the antenna, reaches its lowest point directly below the antenna, and increases as the vehicle passes under the antenna. do.

Focusing on this change in speed, the speed of the vehicle is detected when the angle θ is as small as possible, and the detected speed is set as Vl.

Memorize the speed v1 and compare it with the speed V as the vehicle progresses, A vehicle type signal (time interval T) corresponding to the condition is created.

Expressing this as the time interval T of the vehicle type signal, the detected speed v1, and the distance traveled by the vehicle during that time, when the vehicle approaches the antenna, the main reflection is from the head of the vehicle, and after passing directly under the antenna, the main reflection is (It is thought that the main reflection is from the rear of this vehicle, so L, L
The relationship between c and La is as shown at the beginning of Figure 2.

The slope of this l-■ curve becomes steeper as it approaches the origin ζ, so even if the error in detection speed ■1 is taken into account, the distance traveled can be determined with considerable accuracy, so using this information, It is possible to determine the type of vehicle.

In other words, an antenna with an elliptical equal sensitivity pattern shown in Fig. 1 is used to detect the vehicle speed ■1, and the time T at which the velocity component V that changes as the vehicle passes ■<αv1 (0<α<1) is determined. By creating a vehicle type signal corresponding to , and performing a calculation called vIT, length information including a vehicle length component is obtained, and this is then filtered so that the vehicle type (vehicle length) can be determined.

Next, a specific example of the configuration will be described according to FIG.

Vehicle detection circuit 6 based on the Doppler signal input from terminal 5
This creates a sensing output at terminal 16.

On the other hand, the period measurement of the Doppler frequency is always carried out by the period measuring circuit 7 which operates at the clock frequency fc applied to the terminal 18,
A memory circuit 8 stores the period at which the sensed output is generated at the terminal 16.
Move to.

The stored information is converted into a speed output by the speed calculation circuit 9.

This speed output is output to terminal 17.

The above points are already known, but the terminal 19
A period measurement circuit 10 operating at a clock frequency αfc (0<α<1) applied to A vehicle type signal generation circuit 12 generates a signal corresponding to a point in time when the output of the signal 10 becomes large and, conversely, a point in time when the output becomes small.

(See FIG. 2) The time interval of this vehicle type signal is measured by a time measuring circuit 13, and the result is multiplied by the speed output by a multiplier 14.

In this case, the output of the multiplier 14 is the unit of length, and this signal is compared with the reference signal applied to the terminal 21c in the determination circuit 15 (from this, the output of vehicle types such as large, medium, and small can be obtained at the terminal 20). can.

As is clear from the above embodiments, according to the present invention, by installing one Doppler radar type vehicle sensor, it is possible to determine the vehicle speed and the type of vehicle.

Moreover, when installing the measuring device, it is only necessary to install the antenna at a predetermined height, and the installation work is easy.

[Brief explanation of drawings]

Figure 1 shows the equivalent antenna pattern, Figure 2 A shows the Doppler signal detection band diagram, Figure 2 shows the Doppler signal speed information diagram, and Figure 3 shows the Doppler signal speed information diagram.
The figure shows an embodiment of the present invention (a circuit to which the vehicle type discrimination method is applied, and FIG. 4 is a block diagram of a Doppler radar. 3...Antenna, 6...Vehicle detection circuit, 13... Time measurement circuit, 14... Multiplier.

Claims (1)

[Claims] 1. Vehicle speed Vo detected above the lane to be detected (from a Doppler signal above a certain level that can be obtained through an antenna installed).
At the same time, the vehicle length is determined from the time during which the speed component Vo', which changes as the vehicle passes, is α times (0<α<1) the vehicle speed Vo and the vehicle speed Vo, and the vehicle type is determined. A vehicle type identification method that is characterized by a low G. 2 The center of the antenna's equal-sensitivity pattern is shifted from directly below the antenna, the vehicle speed is detected at a position far from the antenna, and length information including the length of the vehicle commander valve is obtained from the subsequent speed component information and vehicle speed information, and from this the vehicle type is determined. A vehicle type discrimination method according to claim 1, characterized in that a determination is made.