JPH0317159B2 - - 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 vehicle traffic flow on roads and road networks.

Conventional configuration and its problems FIG. 1 shows a conventional traffic flow measuring device.

The configuration of this conventional example will be explained below with reference to FIG. In FIG. 1, 1a and 1b are vehicle sensors, 1a is installed on the upstream side in the direction of vehicle movement, and 1b is installed on the downstream side. Reference numeral 2 denotes a speed calculating section, 3 a modulating device, 4 a demodulating device, and 5 a central device, which are connected to each other 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 FIGS. 2A to 2C, timing charts of the conventional example, the speed calculation section 2 detects the rise of the vehicle presence pulse c of the upstream vehicle sensor 1a, and raises the speed pulse e. Furthermore, the rising edge of the vehicle presence pulse d of the downstream vehicle sensor 1b is calculated by the speed calculation unit 2.
By similarly detecting at , 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 speed pulse e are connected to the central device 5 via the modulation device 3 and the demodulation device 4, thereby forming one signal transmission system.
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, although ultrasonic sensors are usually used as the vehicle detectors 1a and 1b, the vehicle presence pulses c and d are
As shown in Figures D and E, the chips are c-1, c-2, c-
3. d-1, d-2, and d-3 may occur.
Due to this pulse missing phenomenon, an erroneous vehicle detection signal occurs. That is, since the vehicle presence pulse c is partially missing, the exact total vehicle presence time becomes unknown, and at the same time, the exact number of passing vehicles becomes unknown. Furthermore, as shown in FIG. 2F, the velocity pulse e rises in response to the rise of the existing pulse c, and the velocity pulse e
The unnecessary speed pulse e corresponds to the missing parts c-2 and d-1 of the illustrated pulse because it falls in accordance with the falling of the pulse e.
-2 is generated. Unnecessary pulse e-2 is generated due to irregular pulse dropout, so it may become abnormally short as shown in the figure, or it may be caused by pulse dropout on the falling signal side d.
If -1 to d-3 do not exist, the dashed line e-
2', the signal has an extremely irregular shape and becomes an abnormal length signal.

As described above, the conventional example has various problems such as the extended vehicle presence time, the number of vehicles, the number of speed pulses, and the occurrence of abnormal short and long speed pulses due to the phenomenon of partial omission of vehicle presence pulses.

Purpose of the Invention The present invention eliminates the drawbacks of the above-mentioned conventional example, and provides a traffic flow measuring device that is capable of highly accurate measurement by introducing a preprocessing device that has a function of correcting pulse dropout phenomenon and canceling abnormally long and short pulses. It provides:

Structure of the Invention In order to achieve the above object, the present invention disposes a preprocessing device at the front stage of a central device, and once introduces the vehicle presence pulse of a conventional vehicle sensor into the preprocessing device. A highly accurate vehicle passing signal is obtained by performing various shaping, calculations, and corrections in the speed pulse setting circuit and abnormal pulse correction circuit and transmitting the signal to the central device.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows a block diagram of an embodiment of the traffic flow measuring device of the present invention. The vehicle sensors 1a and 1b are connected to a central device 5 via a modulator 3, a demodulator 4, and a preprocessor 6.
FIG. 4 is an internal configuration diagram of the preprocessing device 6, and the vehicle presence pulses c and d of the upstream vehicle sensor 1a and the downstream vehicle sensor 1b are pulse shaping circuits 7a and 7b.
is connected to the central device 5 via a speed pulse setting circuit 8 and an abnormal pulse correction circuit 9. Note that a plurality of sets of vehicle sensors are connected to the pre-processing device 6.

The vehicle sensor 1a, 1b transmits an ultrasonic signal T, for example, every 60 msec, as shown in FIG. 6A. The ultrasonic signals transmitted from the vehicle sensors 1a, 1b are reflected by the vehicle, and the reflected waves are received by the vehicle sensors 1a, 1b within a predetermined time range, as shown in FIG. 6B. When the reflected wave R is detected within a predetermined time range, as shown in FIG. 6C, a presence pulse _c1 of a predetermined time length (60 msec) is generated after the predetermined time range has elapsed. If this operation is performed every 60 msec and a reflected wave from the vehicle is always detected, c ₂ , c ₃ , c ₄ . , B, vehicle presence pulses c and d of a predetermined time width depending on the vehicle length are obtained. However, if the reflected wave from the vehicle is not detected within a predetermined time range,
As shown in B, a presence pulse of a certain length (60 msec) is not generated, resulting in a pulse dropout during the vehicle presence pulse.

In one embodiment of the present invention described above, the existence pulse of a certain time width that is generated when a reflected wave is received.
The time width of c ₁ , c ₂ ... is determined by the pulse shaping circuit 7 in Fig. 4.
a and 7b are extended to, for example, 120 msec to prevent pulse dropouts even when one reflected wave cannot be detected.

To explain the operation of this embodiment having the above configuration, as shown in the timing charts of FIGS. 5A to 5G, the vehicle presence pulse c on the upstream side and the vehicle presence pulse d on the downstream side have irregular pulse missing parts. is shaped by the pulse shaping circuits 7a and 7b, resulting in smooth rectangular pulses f, as shown in FIGS. 5C and 5D.
g to the speed pulse setting circuit 8. In the speed pulse setting circuit 8, as shown in FIG. 5E, a speed pulse i is set which is set at the rising edge of the upstream speed pulse f and reset at the rising edge of the downstream speed pulse g. Therefore, the unnecessary speed pulse ia caused by the omission of the vehicle presence pulse is eliminated by the shaping action of the pulse shaping circuits 7a and 7b.

In addition, the speed pulse i-b shown in Figure 5E is generated due to the upstream vehicle presence pulse c-b generated due to the lane change behavior of a passing vehicle or surrounding noise. Since there is no downstream vehicle presence pulse, the speed pulse i-b is maintained in the rising state. In order to correct this abnormally long pulse, the abnormally long speed pulse is time-limited corrected by the abnormal pulse correction circuit 9. That is, k in Figure 5G
-b, the abnormally long velocity pulse i-b is corrected to the longest sensing time t _O as a timed velocity pulse. Further, the abnormal pulse correction circuit 9 is also provided with an abnormal short pulse correction function, so that even if an abnormally short speed pulse ia is input to the correction circuit 9, the pulse ia is erased. That is, abnormal short-speed pulses caused by circuit noise or pulse dropouts that cannot be completely corrected by the shaping circuits 7a and 7b are eliminated by the abnormal pulse correction circuit 9. Abnormal pulse correction circuit 9
is erased when the time width of the vehicle presence pulse output from the speed pulse setting circuit 8 is smaller than the first set value, and is set to a constant time width (t _O ) when it is larger than the second set value. This is a correction.

Note that various methods are possible for pulse correction in the abnormal pulse correction circuit 9. When the longest sensing time t _O is always constant as in the above embodiment,
It is set at the rising edge of speed pulse i, and is maintained for a certain period of time t _O
This can be easily realized by using a circuit that is reset after a certain period of time has elapsed.

Other abnormal pulse correction methods include the longest sensing time
Another possible method is to make _tO variable depending on the average speed of the vehicle being measured. That is, as an example, as shown in the following equation, V=α・V _P +(1−α)・V _R , t _O ′=(V) The longest sensing time t _O ′ (msec) is determined by the past vehicle speed pulse V _P ( msec) and measured vehicle speed pulse V _R (msec)
It is determined according to the average speed pulse V (msec) determined by the weighting coefficient α, and the maximum sensing time can be set according to the vehicle running speed, allowing highly accurate speed pulse correction. achieved.

In addition, as another abnormal pulse correction method, by introducing the upstream vehicle presence signal h, the downstream vehicle presence signal g, and the speed signal i into the abnormal pulse correction circuit 9, the pulse length t _U of the upstream signal h, the downstream The following equation is determined from the pulse length t _L of the side signal g and the pulse length t _V of the speed signal i.

0.5<t _L /t _U <2 C ₁ *t _V >t _U , t _L C ₁ : Constant As shown in the above formula, the ratio of vehicle sensing pulse lengths on the upstream and downstream sides must be within the ratio of 1:2. Therefore, there is no extreme difference in pulse length, and there is a certain correlation between the speed pulse length and the upper and lower pulse lengths, that is, the total vehicle length is usually less than 12 m, and the upstream and downstream vehicle sensing installation intervals are usually 5 m. Since the constant C ₁ is set to 3, the vehicle presence pulse lengths t _U and t _L are the speed pulses.
t The length must be less than three times _V. This is the installation interval
3 times 5m is 15m, which is inevitably determined because the total length of the vehicle is always less than 15m. Therefore, it is possible to determine the abnormality of each pulse based on the mutual ratio of the upper and lower pulse lengths and the ratio between the upper and lower pulse lengths and the speed pulse length, and if necessary, the pulses can be corrected to satisfy the above correlation. It's easy.

As described above, in this embodiment, the vehicle presence signal from the vehicle sensor is processed by the pre-processing device, including pulse shaping, speed pulse setting, and abnormal pulse correction, and the vehicle information is transmitted to the central device. Therefore, it is possible to prevent the occurrence of abnormal pulses and erroneous measurement of the number of passing vehicles due to the phenomenon of missing vehicle presence pulses.

Furthermore, in the above embodiment, although it has been explained that the maximum sensing time of the abnormally long speed pulse is variable controlled using the vehicle speed, there is a certain correlation between the vehicle speed and the traffic volume or occupancy. It is known from a traffic engineering perspective that this is the case. Therefore, it is clear that the object of the present invention can be achieved by variably controlling the longest sensing time in response to one or more signals of traffic information such as passing traffic volume or occupancy instead of the speed signal. be. More specifically, the maximum sensing time is set to be shorter when the traffic volume or occupancy is low, that is, when the vehicle speed is high, and the maximum sensing time is set to be longer when the traffic volume or occupancy is high, that is, when the vehicle speed is low. As a result, the same effect as control using a vehicle speed signal can be achieved.

It goes without saying that in the above embodiments, various types of presence type sensors other than the ultrasonic type can be used as the vehicle sensor. Furthermore, although pulse shaping circuits generally add a fixed holding time, it goes without saying that measures such as making the holding time variable depending on the vehicle running speed are also effective as a pulse shaping effect. . Furthermore, it is clear that the abnormal pulse correction circuit 9 operates effectively even when the pulse shaping circuits 7a, 7b and the speed pulse setting circuit 8 are arranged in parallel with each other.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

(a) Since the pre-processing device for vehicle detection signals is installed before the central device, it is possible to directly introduce and use existing vehicle sensor signals, and the pre-processing device is added to the conventional equipment. By doing so, it becomes possible to measure traffic flow with high precision while using the same equipment. Furthermore, by installing a preprocessing device just before the central device, the raw signal data from each vehicle sensor is directly transmitted, making it easy to collect and record the raw data, and in the unlikely event that a vehicle detection failure occurs. It has the advantage of being easy to discover and manage.

(b) By equipping the preprocessing device with a vehicle presence pulse shaping circuit, it is possible to correct abnormal missing portions of the vehicle presence pulse, making it possible to accurately measure occupancy and at the same time accurately measure vehicle passing. The number of units can be measured.

(c) A speed pulse setting circuit is installed in the preprocessing device, and by sending the accurate vehicle presence pulse after shaping to the speed pulse setting circuit, irregular abnormal speed pulses caused by missing presence pulses can be eliminated. Occurrence can be prevented.

(d) An abnormal pulse correction circuit is installed in the preprocessing device to set a time limit for the abnormal long speed signal when there is a shortage of downstream vehicle presence pulses, and to correct abnormal short speed signals due to lack of vehicle presence pulses or noise, etc. By providing a speed signal erasing function, it is possible to prevent abnormal speed signals from being sent to the central device and to measure traffic flow with high precision.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional traffic flow measurement device.
2A to 2F are timing charts of the same device, FIG. 3 is a block diagram of a traffic flow measuring device according to an embodiment of the present invention, FIG. 4 is a block diagram of a preprocessing device of the same device, and FIG. 5A -G are timing charts of the same device, and FIGS. 6A to 6C are timing charts illustrating the principle of vehicle presence pulse generation of the same device. 1a, 1b...vehicle sensor, 3...modulation device,
4... Demodulator, 5... Central device, 6... Preprocessor, 7a, 7b... Pulse shaping circuit, 8... Speed pulse setting circuit, 9... Abnormal pulse correction circuit.

Claims (1)

[Claims] 1. A plurality of vehicle sensors 1a, 1b, a plurality of pulse shaping circuits 7a, 7b, and a speed pulse setting circuit 8.
, an abnormal pulse correction circuit 9, and a central device 5, the plurality of vehicle detectors 1a and 1b are installed on the upstream and downstream sides of the road in the vehicle traveling direction, and are configured to detect the reflected waves of the transmitted ultrasonic waves. It senses the presence of a vehicle and generates a presence pulse with a predetermined time width, and the plurality of pulse shaping circuits 7a and 7b each hold the presence pulse from the plurality of vehicle sensors 1a and 1b for a predetermined time. The speed pulse setting circuit 8 uses the output signal of the pulse shaping circuit 7a on the upstream side as a set signal and the output signal of the pulse shaping circuit 7b on the downstream side as a reset signal to generate a speed pulse, The abnormal pulse correction circuit 9 has an abnormal long pulse correction function and an abnormal short pulse correction function, and the abnormal long pulse correction function corrects the speed pulse to the longest sensing time when it is longer than a predetermined time. The abnormal short pulse correction function is such that if the speed pulse is shorter than a predetermined time, the speed pulse is erased, and the central device 5 inputs the output signal of the abnormal pulse correction circuit 9, A traffic flow measurement device characterized by determining the traffic condition of the road.