JPH05114097A - Traffic flow detecting device - Google Patents

Abstract

PURPOSE:To detect the speed of a traffic flow by a simple device and to obtain a compact and inexpensive traffic flow detecting device by collecting noises by the 1st and 2nd sound collectors and analyzing the frequency of the collected noises. CONSTITUTION:The 1st and 2nd sound collectors 1, 2 are arranged on the same measuring point in the vicinity of a road and the noises of the traffic flows in the upstream and downstream directions from the measuring points are collected by respective sound collectors 1, 2. Respective collected noises generate a difference in frequency spectral distribution due to Doppler effect. Thereby a frequency analyzing circuit 6 finds out the representative values (mean values or peak values) fu, fd of respective frequency-analyzed frequency distribution, a frequency distribution storing/comparing circuit 7 finds of a difference (fu-fd) and a frequency/spedd computing circuit 8 executes the operation of v=V(fu- fd)/(fu+fd) to find out the speed (v) of a traffic flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traffic flow detecting device for detecting the state of traffic flow from noise emitted from a vehicle.

[0002]

2. Description of the Related Art Today, a road traffic information network is being established, and a traffic flow detection device for detecting the speed of vehicles passing through the road and the degree of traffic congestion (state of traffic flow) is installed on a main road. ing.

Conventionally, as the traffic flow detecting device, an ultrasonic system or a microwave system which emits ultrasonic waves or microwaves toward a passing vehicle and receives the reflected waves to detect the state of the traffic flow. Alternatively, a loop coil system is generally used in which a loop coil is embedded in a road and a change in the inductance of the loop coil by a vehicle passing over the loop coil is used.

[0004]

The above-mentioned ultrasonic or microwave type traffic flow detecting device must be provided with a emitting part for emitting ultrasonic waves and microwaves and a receiving part for receiving reflected waves. However, the manufacturing cost of these launching parts is relatively high (especially the device for generating microwaves is expensive), and the manufacturing cost of one device is considerably high under the present circumstances.

Further, in the above-mentioned loop coil type traffic flow detecting apparatus, the loop coil itself is very expensive, and large-scale construction such as burying a large loop coil under the road surface is required.

By the way, in order to detect the traffic flow not only at one point on the road but also on the entire road, it becomes necessary to disperse a plurality of traffic flow detection devices on the road.
In this case, in the above-described conventional traffic flow detecting devices, the installation cost of the device becomes enormous, so that a small and inexpensive traffic flow detecting device is now desired.

Although not common, traffic flow detection devices of other methods such as an electromagnetic induction method, an infrared method, a geomagnetic method, a radiation temperature detection method, an image processing method, etc. are being developed, A small and inexpensive device has not been realized yet.

The present invention has been made in view of the above, and an object thereof is to provide a small-sized and inexpensive traffic flow detecting device.

[0009]

Therefore, in order to solve the above-mentioned problems, a traffic flow detecting apparatus according to the present invention is installed at one measurement point near a road, and the noise of traffic flow upstream from the measurement point. A first sound collecting means for collecting sound, for example, a unidirectional microphone, and a second sound collecting means for installing noise at a traffic flow downstream from the measuring point, installed at the same measurement point as the first sound collecting means.
Sound collecting means, for example a unidirectional microphone, and the first
A frequency analysis is performed on the noise collected by the sound collecting means to obtain a first frequency spectrum distribution, and a frequency analysis is performed on the noise collected by the second sound collecting means. The second frequency analysis means for obtaining the frequency spectrum distribution of the above and the speed detection means for obtaining the speed of the traffic flow based on the first frequency spectrum distribution and the second frequency spectrum distribution are provided.

[0010]

According to the above construction, the first sound collecting means and the second sound collecting means such as a unidirectional microphone are installed at the same measurement point near the road, and the first sound collecting means measures the sound. The noise of the traffic flow upstream from the point is collected, while the second sound collecting means collects the noise of the traffic flow downstream from the measurement point. Then, the noise of the traffic flow collected by the first sound collecting means is subjected to frequency analysis by the first frequency analyzing means to obtain a first frequency spectrum distribution, and also collected by the second sound collecting means. The noise of the traffic flow is frequency-analyzed by the second frequency analyzer to obtain the second frequency spectrum distribution.

Due to the Doppler effect, the first frequency spectrum distribution is higher in frequency band than the frequency spectrum distribution of the noise of the traffic flow itself, and conversely,
The second frequency spectrum distribution shifts to the lower side. Then, there is a correlation between the frequency shift (difference) between the first frequency spectrum distribution and the second frequency spectrum distribution caused by the Doppler effect and the speed of the traffic flow.

Therefore, the speed of the traffic flow can be obtained from the first frequency spectrum distribution and the second frequency spectrum distribution, and this is performed by the speed detecting means.

As described above, a simple device for collecting traffic flow noise by the first sound collecting means and the second sound collecting means installed near the road and analyzing the frequency (measurement signals such as ultrasonic waves and microwaves). It is possible to obtain the speed of the traffic flow by means of the need for the launching part of (1), and the size and cost of the device can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

Due to the Doppler effect, the traffic noise detected at a certain measurement point P near the road (see FIG. 3) is in the upstream direction from the measurement point P (close to the measurement point P as shown in FIG. 4). Direction), compared with the frequency spectrum distribution F ₀ of the noise (traffic flow noise itself) when the traffic flow passes through the measurement point P, the frequency band of the frequency spectrum distribution F _u shifts to the higher side, Further, in the downstream direction from the measurement point P (measurement point P
(The direction away from), the frequency spectrum distribution F
The frequency band of _d shifts to the lower side.

A representative value (for example, an average value or a peak value) of the frequency spectrum distribution F _u · F _d · F ₀ is calculated as a frequency f _u · f _d.
When f ₀ , V is the speed of sound, and v is the average speed of the traffic flow, f _u = f ₀ (V + v) / V (1) f _d = f ₀ (V-v) / V ( 2) f ₀ = ( _fu + f _d ) / 2 (3)

From the above equations 1, 2 and 3, the average velocity v of the traffic flow
_{Is, v = V (f u -f} d) / (f u + f d) a (4).

Therefore, the frequency spectrum distribution F _u of traffic flow noise in the upstream direction and the frequency spectrum distribution of traffic flow noise in the downstream direction are measured from a certain measurement point P (see FIG. 3) using a collection of various vehicles as the traffic flow. The average velocity v of the traffic flow can be obtained from the above equation 4 by measuring F _d and determining the frequency f _u · f _d that is a representative value of these.

Therefore, as shown in FIG. 1, the traffic flow detecting apparatus according to this embodiment has a first sound collector (first sound collecting means) 1
And a second sound collector (second sound collecting means), and amplifier circuits 3 and 4
A switching circuit 5, a frequency analysis circuit (first and second frequency analysis means) 6, a frequency distribution storage / comparison circuit (speed detection means) 7, and a frequency / speed calculation circuit (speed detection means).
8, a timing control circuit 9, and a speed display output circuit 10
It has and.

The first and second sound collectors 1 and 2 are installed at the same measurement points near the road (side of the road or above the road). The first and second sound collectors 1 and 2 are unidirectional microphones. The first sound collector 1 emits noise emitted from a traffic flow in an upstream direction from the measurement point, and the second sound collector 2 produces measurement noise. The noise generated from the traffic flow in the downstream direction is collected. Then, the first and second sound collectors 1 and 2 convert the collected noise into an electric signal corresponding to the sound pressure level, and transmit the electric signal to the amplifier circuits 3 and 4 via a communication unit (not shown).

In the case of this embodiment, the first and second sound collectors 1
・ Except for 2, all are installed in the road management office, and the system is such that the collected noise data can be processed by the road management office at the receiving end through communication means.

The amplifier circuit 3 amplifies the signal from the first sound collector 1 input via the communication means and outputs the signal A (see FIG. 2) to the switching circuit 5. In addition, the amplifier circuit 4
Outputs the signal B (see FIG. 2) to the switching circuit 5 by amplifying the signal from the second sound collector 2 which is also input via the communication means.

The timing control circuit 9 outputs a control signal C (see FIG. 2) for alternately switching the signal A and the signal B output to the frequency analysis circuit 6 to the switching circuit 5, and the signal switching operation of the switching circuit 5. To control.

From the above, the signal D (see FIG. 2) output from the switching circuit 5 to the frequency analysis circuit 6 is the signal A, the signal B, the signal A, the signal B, ... Become. The timing control circuit 9 outputs an analysis start signal E (see FIG. 2) synchronized with the signal C to the frequency analysis circuit 6 every time the switching circuit 5 is switched.

The frequency analysis circuit 6 uses the analysis start signal E.
The signal D from the switching circuit 5 is sampled from the time when the signal is input to the next signal is input, and the frequency of the sampled signal is analyzed every time the analysis start signal E is input. Thereby, the signal A and the signal B are alternately sampled and frequency-analyzed, and the frequency spectrum distribution of the signal A (first frequency spectrum distribution) and the frequency spectrum distribution of the signal B (second frequency spectrum distribution) are obtained. Sequentially required.

Further, the frequency analysis circuit 6 uses the obtained signal A
From the frequency spectrum distribution of the signal B and the frequency spectrum distribution of the signal B, the frequency f _un (n = 1, 2, ...) And the frequency f _dn (n = 1, 2, …), And the data signal G representing these
(See FIG. 2) is output to the frequency distribution storage / comparison circuit 7.

Further, the timing control circuit 9 starts the comparison operation in synchronization with the signals C and E each time the switching operation of the switching circuit 5 is performed twice, and starts the comparison operation signal H (see FIG. 2). Is output to the frequency distribution storage / comparison circuit 7.

The frequency distribution storage / comparison circuit 7 is provided with storage means (not shown) such as a RAM having an area for storing the data of the frequencies f _un and f _dn of the signal G. In the frequency distribution storage / comparison circuit 7, first, the frequency f _u1
Data is input and stored in the storage means. Then, at the same time as the data of the frequency f _d2 is input, the comparison start signal H is input, and the difference f _v1 (f _v1 = F _u1 −f _d1 ) is obtained. Thereafter, similarly, the frequency distribution storage / comparison circuit 7 causes f _vn (f _vn =
f _un −f _dn , n = 1,2, ...) are sequentially obtained.

Further, the frequency distribution storage / comparison circuit 7 is
A data signal J (see FIG. 2) representing the difference f _vn between the frequencies f _un and f _dn is output to the frequency / speed calculation circuit 8.

The frequency / speed arithmetic circuit 8 calculates the following equation 5 (see equation 4) on the basis of each data (f _un , f _dn , f _vn ) of the input signal J to average traffic flow. Speed v _n
(N = 1,2, ...)

V _n = _{Vf vn} / (f _un + f _dn ) (5) Further, the frequency / speed calculation circuit 8 calculates the average speed v _n (n = 1, 2, ...) Of the traffic flow. 2) is output to the timing control circuit 9 and the speed display output circuit 10.

The frequency distribution storage / comparison circuit 7 and the frequency / speed operation circuit 8 constitute a speed detecting means.

Then, the speed display output circuit 10 sequentially outputs signals for displaying the obtained average speed v _n of the traffic flow to a display means (not shown).

If the frequencies f _un and f _dn analyzed by the frequency analysis circuit 6 and compared by the frequency distribution storage / comparison circuit 7 _belong to the same group of vehicles (traffic flow), they are the most accurate. Various measured values (average speed v _{n of} traffic flow) are obtained.
To this end, the switching timing of the switching circuit 5 (that is, the timing of sampling) is changed according to the speed of the traffic flow, and the noise of the group of vehicle aggregates collected by the first sound collector 1 is after a certain time It suffices that the switching circuit 5 is switched by the tamming just collected by the second sound collector 2.

Therefore, the timing control circuit 9 outputs the control signal C of the switching timing corresponding to the obtained speed v _n to the switching circuit 5 to correct the switching timing. As a result, the switching timing of the switching circuit 5 is feedback-adjusted so as to be always optimum based on the speed v _n that is sequentially obtained. Further, the timing control circuit 9 synchronizes with the signal C and outputs the signal E and the signal H.
Is output, and the frequency analysis circuit 6 and the frequency distribution memory comparison circuit 7 are analyzed in accordance with the switching timing of the switching circuit 5.
Controls the timing of the comparison operation.

The initial control signal C output from the timing control circuit 9 is switched by the switching circuit 5 at a predetermined interval.
For example, the switching timing is set by estimating the speed of the traffic flow during normal times on the road to be measured.

As described above, in the present embodiment, the traffic flow is collected by a simple device that only measures the traffic flow noise collected by the first and second sound collectors 1 and 2 installed near the road. The average speed of can be calculated. That is, unlike the conventional ultrasonic and microwave traffic flow detection devices, it does not require an ultrasonic or microwave emission unit, and does not require large-scale installation work such as a loop coil system, Miniaturization and cost reduction can be realized.

In this embodiment, the timing control circuit 9
The sampling timing is adjusted by the above so that the average speed of the traffic flow can be obtained more accurately. For example, the switching circuit 5 is switched at a constant cycle so that the sampling timing is constant. Even if there is, a measured value close to that of this embodiment can be obtained.

Further, in the present embodiment, each noise collected by the first and second sound collectors 1 and 2 can be frequency-analyzed by one frequency analysis circuit 6 by using the switching circuit 5. And the frequency analysis circuit 6 described above.
Serves as both the first frequency analysis means and the second frequency analysis means described in the claims, but is not limited to this. That is, the first and second
Each noise collected by the sound collectors 1 and 2 may be subjected to week frequency analysis by a separate frequency analysis circuit, and the data sampled simultaneously by the first and second sound collectors 1 and 2 may be analyzed. Even if it is used, a measured value close to that of this example can be obtained.

[0040]

As described above, the traffic flow detecting device according to the invention of claim 1 is installed at one measurement point near the road and collects the noise of the traffic flow upstream from the measurement point. The sound collecting means, the second sound collecting means installed at the same measurement point as the first sound collecting means, and collecting the noise of the traffic flow in the downstream direction from the measurement point, and the first sound collecting means. Second frequency analysis means for performing a frequency analysis of noise to obtain a first frequency spectrum distribution and frequency analysis of noise collected by the second sound collection means to obtain a second frequency spectrum distribution It is configured to include frequency analysis means and speed detection means for determining the speed of the traffic flow based on the first frequency spectrum distribution and the second frequency spectrum distribution.

Therefore, the speed of the traffic flow can be obtained by a simple device of collecting the traffic flow noise by the first sound collecting means and the second sound collecting means installed near the road and analyzing the frequency. Unlike the conventional ultrasonic and microwave traffic flow detectors, it does not require an ultrasonic or microwave emission part, and it does not require large-scale installation work such as the loop coil method, thus reducing the size of the device, This has the effect of realizing cost reduction.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a block diagram showing a configuration of a main part of a traffic flow detection device.

FIG. 2 is a time chart showing signals output from each circuit of the traffic flow detection device.

FIG. 3 is an explanatory diagram for explaining an influence of a Doppler effect of traffic flow noise measured at one measurement point near a road.

FIG. 4 is an explanatory diagram showing a deviation of a frequency spectrum distribution of traffic flow noise due to a Doppler effect.

[Explanation of symbols]

1 1st sound collector (1st sound collecting means) 2 2nd sound collector (2nd sound collecting means) 6 Frequency analysis circuit (1st and 2nd frequency analysis means) 7 Frequency distribution memory comparison circuit (speed detection means) ) 8 frequency / speed calculation circuit (speed detection means) v _n speed

Claims (1)

[Claims] 1. A first sound collecting means installed at one measurement point near a road and collecting noise of a traffic flow upstream from the measurement point, and installed at the same measurement point as the first sound collection means, Second sound collecting means for collecting noise of traffic flow downstream from the measurement point, and frequency analysis of the noise collected by the first sound collecting means to obtain a first frequency spectrum distribution. Analysis means, second frequency analysis means for performing a frequency analysis of the noise collected by the second sound collection means to obtain a second frequency spectrum distribution, the first frequency spectrum distribution and the second frequency spectrum A traffic flow detection device comprising: speed detection means for determining the speed of a traffic flow based on a distribution.