JPH0312756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a traffic flow measuring device used for monitoring and controlling motor vehicle traffic on roads and road networks.

(Structure of conventional example and its problems) A conventional traffic flow measuring device will be explained based on FIGS. 1 to 3.

In FIG. 1, 1a and 1b are vehicle sensors, with 1a installed on the upstream side and 1b installed on the downstream side in the direction of vehicle travel. 2 is a speed calculation unit, 3 is a modulation device,
4 is a demodulating device, and 5 is a central device, each of which is connected by wire as shown in the figure to constitute a traffic flow measuring device.

Next, the operation of the conventional example having the above configuration will be explained.
As shown in timing charts of the conventional example described above in FIGS. 2A to 2C, the speed calculation unit 2 detects the rise of the vehicle presence pulse c of the upstream vehicle sensor 1a, and raises the speed pulse e. Further, by similarly detecting the rising edge of the vehicle presence pulse d from the downstream vehicle sensor 1b in the speed calculating section 2, the speed pulse e is lowered. Therefore, the speed of the vehicle can be detected from the installation distance of the pair of vehicle sensors 1a and 1b and the duration of the speed pulse e. Furthermore, the number of vehicles and the occupation can be obtained from the vehicle presence pulse c. That is, the vehicle presence pulse c and the speed pulse e are connected to the central device 5 via the modulation device 3 and the demodulation device 4,
One signal transmission system is constructed. A large number of demodulators 4' and signal transmission systems are connected to the central device 5.

However, the above conventional example has the following drawbacks. That is, vehicle sensor 1
Ultrasonic sensors are usually used for a and 1b, but
Due to the shape of the vehicle body or the phase interference of reflected waves, the vehicle-present pulses c and d are missing as shown in Figure 3 A' and B'. −
2, d-3 may occur. Due to this pulse missing phenomenon, an erroneous vehicle detection signal occurs.

The operation of the vehicle sensor will be explained in more detail with reference to FIG. 6. As shown in FIG. 6A, the vehicle sensor 1a, 1b transmits an ultrasonic signal T, for example, every 60 msec. The ultrasonic signals transmitted from the vehicle detectors 1a and 1b are reflected by the vehicle, and as shown in FIG.
As shown in the figure, the vehicle sensor 1a,
The reflected wave is received at 1b. When the reflected wave R is detected within a predetermined time range, a presence pulse _C1 of a predetermined time length (60 msec.) is generated after the predetermined time range has elapsed, as shown in FIG. 6C. If this operation is performed every 60 msec. and the reflected wave from the vehicle is always detected, C ₂ ,
As a result of the occurrence of C ₃ , C ₄ . . . , vehicle presence pulses c and d having a predetermined time width corresponding to the vehicle length are obtained as shown in FIGS. 2A and 2B. However, if the reflected wave from the vehicle is not detected within a predetermined time range,
As shown in A′ and B′, the fixed time length (60×Nmsec.
N: An integer) presence pulses are not generated, resulting in a pulse dropout during the vehicle presence pulse. Central device 5
Internally, it is common to measure the number of passing vehicles by detecting the rising or falling signals of vehicle presence pulses c to d and counting the number of vehicle presence pulses. As shown in the figure, when pulses are missing, there is a drawback that a large error occurs in the number of measurement units. That is, the third
As shown in Figure A', when there are pulse omissions c-1 and c-2, there is a drawback that the number of vehicles is incorrectly measured as three.

(Object of the Invention) The present invention eliminates the drawbacks of the conventional example described above, and aims to improve the error in measuring the number of vehicles caused by the omission of the vehicle presence pulse.

(Structure of the Invention) In order to achieve the above object, the present invention measures the number of passing vehicles from the conventional number of vehicle presence pulses to the upstream vehicle presence pulse in the central device or a preprocessing device installed at the front stage thereof. By changing the number of vehicle speed pulses generated from the downstream vehicle presence pulse and the number of vehicle speed pulses to be used, the accuracy of measuring the number of vehicles can be significantly improved.

(Description of Embodiment) The configuration of an embodiment of the present invention will be described based on FIGS. 4 and 5.

FIG. 4 shows a block diagram of an embodiment of the traffic flow measuring device of the present invention. Vehicle sensor 1a, 1b
is connected to a central device 5 via a modulator 3, a demodulator 4, and a preprocessor 6.

FIG. 5 is an internal configuration diagram of the preprocessing device 6, showing an upstream vehicle sensor 1a and a downstream vehicle sensor 1.
Each vehicle presence pulse c, d of b is a pulse shaping circuit 7
a, 7b, and is connected to the central device 5 via a speed pulse setting circuit 8 and a vehicle number measuring circuit 9.
Therefore, as shown in the figure, the central device 5 receives the shaped upstream vehicle presence pulse f, the speed pulse h, and the measured vehicle number signal i obtained from the speed pulse h. Note that a plurality of sets of vehicle sensors are connected to the preprocessing device 6.

In this circuit as well, by extending the pulse retention time to 120 msec. in the pulse shaping circuits 7a and 7b shown in FIG. Even if one reflected wave cannot be detected, pulse loss is prevented. As a result, the pulse missing portion with a pulse missing width of 60 msec. is corrected, that is, the missing portions c-2, d-1, and
d-2 is corrected and formatted as shown in FIG. 3 A'' and B''. However, pulse missing part c- of 60 msec. or more
1 and d-3 are only slightly corrected, but the error in measuring the number of vehicles due to the measurement of the number of pulses of the vehicle presence pulse signals f and g cannot be completely corrected. That is, even with the pulses A'' and B'' corrected by the pulse shaping circuits 7a and 7b, the number of vehicles counted is 2 vehicles per true value of 1 vehicle.

In contrast, in the present invention, the number of vehicles is measured by having a logical configuration in which the number of vehicles is counted by the number of vehicles measuring circuit 9 disposed behind the speed pulse h that is set based on the shaped vehicle presence pulses f and g. Accuracy can be greatly improved. In particular, since the vehicle-present pulses f and g after pulse shaping are used,
Temporary pulse cracking of pulses c and d before pulse shaping,
As is clear from the fact that the erroneous speed pulse e' caused by c-3 and d-1 can be shaped and removed, it has a feature that allows extremely highly accurate counting of the number of vehicles.
In other words, since the pulse omissions of vehicle presence pulses f and g are considered to be independent, the probability of error occurrence in the speed pulse generated by the combination of both pulses f and g is the product of the error probabilities of each pulse f and g. This allows for a significant improvement in measurement accuracy.

As is clear from the above explanation, while the conventional method measures the number of vehicles by measuring the number of vehicle presence pulses, the method of the present invention measures the number of vehicle presence pulses. By counting the number of vehicles, it is possible to significantly improve measurement accuracy.

Furthermore, in the description of the present invention, the vehicle number counting circuit may be provided as hardware in the pre-processing device as described above, but the number-of-vehicles counting function based on speed pulses may be provided in the pre-processing device or in the central device. The same effect can be achieved by configuring the software internally.

(Effects of the Invention) The present invention has the above configuration, and measures the number of traveling vehicles using a speed pulse signal that is set at the rising edge of the upstream vehicle presence pulse and reset at the rising edge of the downstream vehicle presence pulse. Therefore, compared to the conventional method of counting the number of vehicles that directly uses the vehicle presence signal, it is possible to significantly improve the accuracy of counting the number of vehicles.

Furthermore, by generating a speed signal using a signal after vehicle presence pulse shaping, there is an advantage that accuracy can be further improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional traffic flow measurement device.
Fig. 2 is a timing chart of the same device, Fig. 3 is a timing chart when the same pulse is missing, Fig. 4 is a block diagram of a traffic flow measuring device according to an embodiment of the present invention, and Fig. 5 is a diagram of the same device. The block diagram of the preprocessing device, FIG. 6, is a timing chart illustrating the principle of generation of the vehicle presence pulse in the vehicle sensor. 1a, 1b...Vehicle sensor, 2...Speed calculation unit, 3...Modulation device, 4, 4'...Demodulation device, 5
...Central device, 6...Pretreatment device, 7a, 7b...
...Pulse shaping circuit, 8...Speed pulse setting circuit,
9...Vehicle number measurement circuit.

Claims (1)

[Claims] 1 Consists of a first vehicle sensor 1a, a second vehicle sensor 1b, a modulation device 3, a demodulation device 4, a preprocessing device 6, and a central device 5; The second vehicle sensor 1a is disposed on the upstream side in the vehicle traveling direction, and the second vehicle sensor 1b is disposed on the downstream side in the vehicle traveling direction, and outputs vehicle presence pulses c and d, respectively. The demodulator 4 modulates and outputs the vehicle presence pulse c of the first vehicle sensor 1a and the vehicle presence pulse d of the second vehicle sensor 1b, respectively, and the demodulator 4 modulates and outputs the vehicle presence pulse c and the vehicle presence pulse from the modulator 3. The preprocessing device 6 demodulates and outputs each of
and a vehicle number measuring circuit 9, and the first pulse shaping circuit 7a has a vehicle presence pulse c
The second pulse shaping circuit 7b outputs the shaped vehicle presence pulse f by inputting the vehicle presence pulse d.
The speed pulse setting circuit 8 inputs the shaped vehicle presence pulse f and the shaped vehicle presence pulse g and outputs the speed pulse h, and the vehicle number measuring circuit 9 receives the speed pulse h as an input and outputs the speed pulse h and the measured number of vehicles signal i, and the central device 5 receives the shaped vehicle presence pulse f, the speed pulse h and the measured number of vehicles signal i as input, and outputs the speed pulse h and the measured number of vehicles signal i. A traffic flow measurement device that measures traffic flow.