JPS6235157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a road surface detection device in a traffic flow measuring device using an optical system.

In a traffic flow measuring device using an optical system, the level of the output signal (road surface level) when there is no vehicle at the detection point and the optical system is detecting the road surface becomes the reference level for vehicle detection. Since this road surface level changes depending on the weather, for example, sunny, cloudy, rainy, etc., it is necessary to constantly detect the road surface level and update it with new data. Furthermore, the road surface level changes greatly between daytime and nighttime. The waveform of the vehicle detection signal from the optical system also differs significantly between daytime and nighttime, so the waveform processing method also differs. Therefore, if it is possible to determine whether it is daytime or nighttime based on the road surface level, the waveform processing method can be changed accordingly.

An object of the present invention is to provide a traffic flow measuring device using an optical system that can determine when the optical system is detecting a road surface.

The road surface detection device according to the present invention is a traffic flow measuring device equipped with an optical system including a light receiving element that is placed at a position overlooking a required detection point on a road and detects a vehicle passing through the detection point. Means for sampling the output video signal of the light receiving element at a predetermined sampling period that can be sampled multiple times while the vehicle passes, and for each sampling, a deviation between the current sampling data and previous predetermined reference data. a first detection means that compares this deviation with a predetermined reference amount and detects an equilibrium state in which the deviation is less than or equal to the reference amount; and a first detection means that detects an equilibrium state in which the deviation is less than or equal to the reference amount; a second detection means for detecting that the road surface level has been detected continuously for a plurality of times or more; and a means for storing that the road surface level is detected when the second detection means detects the detection result. It is characterized by

According to this invention, it is possible to reliably detect when the light receiving element in the optical system of the traffic flow measuring device is detecting the road surface. Since the level of the output signal of the light receiving element when the light receiving element is detecting the road surface is the road surface level, it is possible to always accurately grasp the road surface level, and vehicle detection processing is reliably performed using this road surface level as a reference. be able to. Furthermore, since it is possible to determine whether it is day or night based on the road surface level, it is also possible to execute processes depending on the day or night.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The example shown below is a case where the present invention is applied to a traffic flow measuring device installed at a position overlooking a road and having a large number of light receiving elements. This device has the advantage of being able to collect vehicle information from multiple points on the road at one location and being easy to install.

FIG. 1 shows how the camera of the traffic flow measuring device is installed. The camera 1 is placed at a required height position (for example, 6 m) above the road L using a support 3 or the like.
Required range in the length direction of road L (e.g. 100m)
It is set up to provide a bird's-eye view. As shown in FIG. 4, the camera 1 is equipped with an optical system 4 including a lens 5 and a large number of light receiving elements. In this example, there are six detection points P1 to P1 within the field of view of camera 1.
There is P6. 1 each on the image forming plane of the optical system 4 in the camera 1 and at locations corresponding to these detection points.
Pairs of light receiving elements dS1, dR1 to dS6, dR6 are arranged. These light receiving elements are composed of photo diodes, for example. As shown in FIG. 2, at each detection point (represented by P), a set area S and a reset area R are set at a required interval l. A pair of light receiving elements (represented by dS and dR) correspond to these regions S and R, respectively.

When the vehicle CA passes through the detection point P from the set area S to the reset area R, a vehicle detection signal is output from the light receiving elements dS and dR by a time t, as shown in FIG. Here, the rising edge of the output of each light receiving element dS, dR is detected, and the difference between the rising edges of both signals is defined as the detection time t. Since this detection time t is the time required for the vehicle to travel between the set area S and the reset area R (distance l), the traveling speed V of this vehicle is determined by the following equation.
However, K is a constant.

V=K・l/t The distance that a vehicle actually moves during the detection time t is affected by the vehicle shape, vehicle height, etc. and varies slightly from vehicle to vehicle, and is actually not equal to the above distance l. do not have. However, by imagining a sensing surface at a position above the road surface by the required height, measuring the distance between both areas S and R on this sensing surface, and statistically correcting this distance, it is possible to increase the vehicle's running speed. It is possible to measure with high precision. If necessary, 6
The average value of the traveling speeds of the same vehicle measured at the three detection points P1 to P6 may be calculated.

The distance between vehicles and the degree of congestion can also be calculated based on this traveling speed. For example, when a certain vehicle is detected at the detection point P1, the headway distance can be determined from the product of the speed of the preceding vehicle detected at the detection point P1 and the elapsed time. For example, the degree of traffic congestion is determined when the measured travel speed is a predetermined speed (for example, 20 km/h) among six points P1 to P6.
h) It can be determined by the number of the following points:

Now, the various processes described above are carried out by the processing device 2.
It will be held in Referring to FIG. 4, the output video signals of each of the light receiving elements dS and dR in the camera 1 are amplified by an amplifier 6 equipped with an automatic gain control function, and then sent to a multiplexer channel device 7. here
The outputs of each of the 12 light receiving elements are sequentially switched to A-
The signal is sent to the D converter 8. The A/D converter 8 performs AD conversion on the input output of the light receiving element at a predetermined sampling period (4.8 mS in this example), and sends the result to a central processing unit (referred to as CPU) 9. CPU9
is multiplexer channel device 7 and A-D
It controls the converter 8, and also performs signal waveform pattern detection processing, which will be described later, and various traffic information calculation processing, which will be described above. The CPU 9 includes a data memory 10 in addition to a program memory (not shown) that stores the execution program. The processing device 2 is provided with a filter circuit and an amplifier for removing low frequency components of the signal input from the camera 1, but illustration thereof is omitted for the sake of simplification.

FIG. 5 shows an example of the waveform of the video signal output from the light receiving element of the camera 1. This signal is AD-converted by an A-D converter 8 every sampling period. This time's AD conversion result is the current data
Let it be Dt. In order to determine whether the current data Dt is increasing, decreasing, or in an equilibrium state compared to the previous data, it is necessary to find the deviation Δω between the current data Dt and the previous data. Previous data to be used for determining this deviation Δω is assumed to be preprocessed data Do. In addition, for the above judgment, this time data Dt and preprocessed data
The reference amount to which the deviation Δω from Do is compared is defined as a reference amount ωo. Furthermore, the concept of a prescribed period T is introduced, and this prescribed period T is set to be a time multiple times (in this example, four times) the sampling period. Then, the deviation Δω and the reference amount ωo are compared for each sampling period, and if the deviation Δω is greater than or equal to the reference amount ωo, or when the specified period T has elapsed, the current data Dt is used as the preprocessing data Do for this preprocessing. data
Update Do. If the rise or fall of the signal is slow, the amount of increase or decrease may not reach the reference amount ωo during the sampling period. A prescribed period T is introduced to detect such slow changes in the signal, and it is checked whether the amount of change reaches the reference amount ωo within the range of the prescribed period T.

The states of signal change include increase, decrease, and equilibrium state where neither increase nor decrease occurs. within the specified period T
If Dt−Do≧ωo, it is regarded as an increasing state. If Dt-Do≦-ωo within the specified period T, it is regarded as a decreasing state. Then, when these determinations are made, the current data Dt is adopted as the preprocessing data Do. Also, even if the specified period T has elapsed, |Dt−Do|<ωo
If so, it is considered to be an equilibrium state, and the preprocessing data Do
As such, we will adopt data Dt this time.

When there is no vehicle at the detection point P and the light-receiving element is detecting the road surface, the level of the output signal of the light-receiving element hardly changes, so the equilibrium state continues continuously. When the equilibrium state continues a required number of times (this is referred to as the equilibrium continuation determination amount Co), the level of the equilibrium state is defined as the road surface level Lo. The road surface level Lo is updated every time a vehicle passes and the equilibrium state continues for a determination amount Co or more. In this example, the road surface level Lo is updated at the time when the vehicle reaches the detection point P and the output signal of the light receiving element rises or falls. In other words, the converted state of the signal is continuously
The end of the vehicle detection signal is confirmed by continuing for more than Co, and after this, when the next vehicle reaches the detection point P and the signal changes from equilibrium to an increasing or decreasing state, the preprocessing data Do used at that time Update the road surface level by setting it as road surface level Lo. A vehicle signal flag F is used to store the state in which a vehicle is detected.

Referring to FIG. 5, let Do1 be preprocessed data at time t1 when no vehicle is detected. The signal hardly rises during each subsequent sampling period. From time t1, the specified period T
Even after (time t2) the deviation (Δω=
Since Dt-Do1) has not reached the reference amount ωo,
There is an equilibrium state between times t1 and t2. Therefore, the current data at this time is updated as preprocessed data Do2.

In the next sampling cycle, the signal rises rapidly and Δω≧ωo, so from time t2 to t
3 is an increasing state. Therefore, the road surface data Lo is updated using the preprocessed data Do2 at this time as the road surface data Lo, and the vehicle signal flag F is turned on. Furthermore, the current data at time t3 is updated as preprocessed data Do3. In the next sampling period after time t3, the deviation Δω does not reach the reference amount ωo. Furthermore, when the deviation Δω is obtained at time t4 after one sampling period has passed and compared with the reference amount ωo, Δω≧ωo is determined, and it is determined that the increasing state is occurring.
Preprocessing data is updated as Do4.

During the period of four sampling cycles after time t4 (regular cycle T), there is almost no change in the signal and there is an equilibrium state, and at time t5, the preprocessed data is changed to Do5. Between times t5 and t7, the signal falls sharply and is determined to decrease at each sampling period, and the preprocessed data is updated (Do6,
(shown as Do7). After time t7, an equilibrium state is reached again, and the preprocessing data is updated every prescribed period T (Do8, etc.). Then, when the conversion state continues by the conversion continuation determination amount Co, it is determined that the vehicle detection signal has ended and the flag F is turned off. As this equilibrium continuation determination amount Co, a value larger than the maximum possible number of continuations in vehicle detection is adopted, and this allows the continuation of the equilibrium state at road surface level Lo and the equilibrium state in vehicle detection (times t4 to t
5).

In FIG. 5, the signal increases twice in a row between times t2 and t4. Assuming that when the same signal change state continues in this way, the waveform pattern is the same, and when the signal changes to another state, the signal waveform pattern changes, then the signals shown in FIG. It consists of a pattern of decrease and equilibrium.

This kind of signal waveform pattern detection processing is
The data memory 10 has areas M1 to M13 for storing various data to be executed by the CPU 9.
is provided. Elijah M1 has this data
Dt is stored, preprocessing data Do is stored in area M2, deviation Δω is stored in area M3, previous signal state is stored in area M4, reference amount ωo is stored in area M5, and road surface level Lo is stored in area M6. be done.
Area M7 is an area for storing waveform patterns and has a large number of storage locations, each of which is assigned an address no to nn of a continuous signal. The address of the storage location where the next detection pattern is to be stored is specified by the contents of area M8.

The area M9 stores the prescribed period T, the area M10 stores the equilibrium continuation determination amount Co, and the areas M11 and M12 store the period counter C1, respectively.
Area M13 is used as a vehicle flag F. Period counter C1
is to count whether or not the specified period T has been reached, and the content is added +1 for each sampling period.
and is reset when the specified period T is reached. The equilibrium counter C2 counts the number of times the equilibrium state continues.

FIG. 6 shows the procedure of signal waveform pattern detection processing and road surface level determination processing by the CPU 9. First, it is checked whether the sampling period has elapsed (step 20), and if it is the sampling period, the input signal is AD converted by the A-D converter 8, and this AD conversion result is stored in the area M1 as the current data Dt. (Step 21). and,
The deviation Δω is calculated by subtracting the preprocessed data Do from the current data Dt (step 22), and this deviation Δω
The absolute value of is compared with the reference amount ωo to check the magnitude relationship between them (step 23). If the absolute value of the deviation Δω is smaller than the reference amount ωo, the period counter C
The contents of counter C1 are incremented by 1 (step 24), and it is checked whether the contents of counter C1 have reached the specified period T (step 25). If the prescribed cycle T has not been reached, the process ends.

When the specified period T has elapsed, the period counter C
1 and clear its contents (step 26), determine that it is in an equilibrium state (step 27), and then check from the contents of area M4 whether or not it was in an equilibrium state last time (step 28). If it is not an increase or a decrease, then the waveform pattern has changed, so the balanced pattern is stored in the address specified by the contents of area M8 in area M7 (step 29), and the next waveform pattern is stored. Therefore, add 1 to the contents of area M8 (step 30). After this, the current state is stored in area M4, and the process advances to step 31. If the previous state was in an equilibrium state, the process directly advances to step 31.

In step 31, the content of the equilibrium counter C2 is incremented by 1, and the magnitude relationship between the content of the equilibrium counter C2 and the equilibrium continuation judgment amount Co is checked (step 32).
If the content of the balance counter C2 is greater than or equal to the judgment amount Co, the vehicle detection signal has ended and the road surface detection state has definitely been reached. Therefore, no, which is the first address of area M7, is set in the content of area M8. (Step 33) The vehicle signal flag F is then turned off to prepare for the next vehicle detection. After this, step 4
9, the current data Dt is stored in the area M2 as the preprocessed data Do, and the processing ends. If the answer in step 32 is NO, the process also moves to step 49.

If the absolute value of the deviation Δω is greater than or equal to the reference amount ωo (NO in step 23), it is in an increasing or decreasing state, so the period counter C1 and the equilibrium counter C
2 respectively (steps 35 and 3).
6) Determine whether the deviation Δω is positive or negative (Step 3
7). If the deviation Δω is positive, it is determined that it is in an increasing state (step 38), and it is checked whether the previous state was an increasing state (step 39). If it was not an increasing state last time, the increasing pattern is stored in area M7 (step 40), the contents of area M8 are incremented by 1 (step 41), and the increasing state is stored in area M4.

If the deviation Δω is negative, it is determined that it is in a decreasing state (step 42), and similarly to the case of an increase, it is checked whether it was in a decreasing state last time (step 4).
3) If the previous state is not a decrease, store the decrease pattern in the address specified by the contents of area M8 of area M7 (step 44), add 1 to the contents of area M8 (step 45), and change the decrease state. Store in Elijah M4.

After processing steps 41 and 45, flag F
Check the status (step 46). If flag F is off, the equilibrium state of road surface level Lo has continued until now, and the signal has increased or decreased for the first time. Therefore, the preprocessed data Do is stored in area M6 as road surface data Lo, and the road surface level The data is updated (step 47) and flag F is turned on (step 48). If flag F is on, this means that the signal is increasing or decreasing in the vehicle detection state, so step 4
Do not process steps 7 and 48.

In either case of increase or decrease, the process then proceeds to step 49, where the current data Dt is stored in the area M2 as preprocessed data Do. If YES in steps 39 and 43, the process directly advances to step 49.

In the example shown in Figure 6, the road surface data Lo is detected when the signal increases or decreases for the first time.
However, when the number of consecutive equilibrium states reaches the equilibrium continuation judgment amount Co (in step 32),
YES), the road surface data Lo may be updated.

When the light receiving element detects a vehicle, the output signal of the light receiving element generally rises from the road surface level Lo and shows a high level. On the other hand, when the shadow of the vehicle is detected, the output signal of the light receiving element falls from the road surface level Lo and shows a level lower than the road surface level Lo. In the processing procedure shown in FIG. 6, the preprocessing data Do is set to the road surface level Lo both when the signal increases for the first time and when it decreases (step 47). Therefore, when either the vehicle or its shadow is detected, The road surface level Lo is also updated.

Road surface level Lo differs significantly between daytime and nighttime. Therefore, by setting the day/night determination level to a level between the average road surface level during the day and the average road surface level at night, and comparing the road surface level Lo with this determination level, daytime and nighttime can be distinguished. can do. If the vehicle signal processing method differs between daytime and nighttime, it is preferable to determine whether it is daytime or nighttime from the road surface level Lo and select a corresponding processing procedure from this determination result.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the installation state of the camera of the traffic flow measurement device, Figure 2 is an enlarged view of the detection point, Figure 3 is a waveform diagram showing the vehicle detection signal, and Figure 4 is the inside of the camera and the processing device. Fig. 5 is an explanatory diagram showing waveform pattern detection and road surface level determination, and Fig. 6 shows the processing procedure when waveform pattern detection processing and road surface level judgment processing are executed by the CPU. This is a flow chart. 4...Optical system, dS1 to dR6...Photodetector, Lo
... Road surface level, Dt ... Current data, Do ... Preprocessing data, Δω ... Deviation, ωo ... Reference amount,
Co...Equilibrium continuation judgment quantity.

Claims (1)

[Scope of Claims] 1. A traffic flow measuring device equipped with an optical system 4 including light-receiving elements dS and dR, which are arranged at a position overlooking a required detection point P on the road and detect a vehicle CA passing through the detection point P. means 8 for sampling the output video signal of the light-receiving element at a predetermined sampling period capable of performing multiple samplings while the vehicle passes the detection point; Deviation Δω from predetermined reference data
means for determining, comparing this deviation Δω with a predetermined reference amount ωo,
A first detection means for detecting an equilibrium state in which the above-mentioned deviation is less than or equal to a reference amount; detecting that the detection of the equilibrium state has continued consecutively for a required number of times or more, which is greater than the maximum number of times Co that can be continued in vehicle detection; A road surface detection device in a traffic flow measuring device, comprising: a second detection means; and a means for storing that the road surface level is detected when the second detection means detects the road surface level. 2. A patent that provides means for canceling the memory of being in a road level detection state when it is detected that the above deviation is greater than or equal to the reference amount when there is a memory of being in a road level detection state. A road surface detection device in a traffic flow measuring device according to claim 1.