JPH0318129B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a signal waveform pattern detection device, and more particularly, to detect whether a signal level that changes over time tends to increase, decrease, or is in an equilibrium state where it neither increases nor decreases. This invention relates to a device that detects the waveform pattern of a signal by checking whether the signal is maintained.

Detection of signal waveform patterns is necessary for pattern discrimination of various signal waveforms. Detection of signal waveform patterns is generally performed by sampling the input signal at regular intervals and comparing the signal level at this sampling point with the signal level at the previous sampling point to determine the magnitude. . At this time, in addition to determining whether the signal level is large or small, it is also determined whether the deviation of the signal level between the previous and current sampling points exceeds a certain reference amount. It is advantageous to detect whether there is an equilibrium state or not.

In such signal waveform pattern detection, the sampling period and reference amount should be determined appropriately according to the waveform of the signal to be detected, but if the signal to be detected has a steep rise or fall, or If the waveform includes various waveforms such as those showing slow changes, it is very difficult to determine the sampling period and reference amount. For example, when the reference amount is set to a large value, rising and falling edges cannot be detected unless the sampling period is lengthened. If the sampling period is lengthened, the rising or falling point will be detected later than the actual point, and if the rising or falling point is detected and used for some kind of measurement, there will be a problem that a detection error will occur. It's raining. Therefore, it is desirable to make the reference amount as small as possible, but if the reference amount is too small, it will fall within the error of AD conversion, making detection impossible. Therefore, it is necessary to set the reference amount to an appropriate value that is not so small that it becomes undetectable. In this case, it is naturally preferable that the sampling period be short. However, if the sampling period is short, a sudden rise or fall can be detected, but a very gentle rise or fall cannot be detected.

The present invention has been made in view of the above circumstances, and provides a signal waveform pattern detection device that can clearly distinguish between a slow rise or fall and an equilibrium state even if the sampling period is as short as possible. It is.

A signal waveform pattern detection device according to the present invention includes: a sensor that outputs an electrical signal representing a detected physical quantity; a sampling circuit that samples the electrical signal output from the sensor at a predetermined sampling period; and a pattern discrimination device that takes in sampled data and discriminates its change pattern, and the pattern discrimination device determines whether the output signal of the sensor is in an increasing state, decreasing state, or in an equilibrium state. This is to determine if there is.

The pattern discrimination device includes a memory and a counter. The memory includes a first area that stores current data, a second area that stores preprocessed data that is previous data, and a third area that stores a specified period that is multiple times the sampling period. ing. The above counter counts the number of consecutive samplings.

The pattern discrimination device compares the current data and the preprocessed data at each sampling period, and increments the counter when the deviation is smaller than a predetermined reference amount. Further, when the deviation is larger than the reference amount, it is determined that the deviation is positive or negative, respectively, to be in an increasing state or a decreasing state, and the preprocessing data of the second area is updated with the current data. When the count value of the counter reaches a value representing the specified period, it is determined that an equilibrium state is reached, the preprocessing data of the second area is updated with the current data, and the counter is cleared.

According to this invention, a specified period that is multiple times the sampling period is set, and whether or not the deviation has reached the reference amount within the specified period is checked for each sampling period, so the sampling period can be shortened. However, it is possible to clearly distinguish between a slow rise or fall and an equilibrium state. Further, since the deviation and the reference amount are compared at each sampling period, sudden rises and falls can be detected quickly. In this way, according to the present invention, highly accurate waveform pattern detection can be achieved.

Hereinafter, a case in which the present invention is applied to a traffic flow measuring device will be described in detail with reference to the drawings. A traffic flow measurement device collects traffic information such as the speed of vehicles traveling on a road, the number of vehicles passing, the distance between vehicles, the degree of congestion, and so on.

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 length range for road L (for example, 100m)
It is set up to provide a bird's-eye view. As shown in FIG. 4, the camera 1 includes an optical system 4 and a large number of light receiving elements. In this example, there are six detection points P1 to P6 within the field of view of the camera 1. Pairs of light receiving elements dS1, dR1 to dS6, dR6 are arranged on the imaging plane of the optical system 4 in the camera 1 at locations corresponding to these detection points.
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) are connected to each of these regions S,
Each corresponds to R.

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 outputted 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 vehicle color, 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 vehicle at the detection point P1 is detected, 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, as mentioned above, various processes are performed by the processing device 2.
It will be held in Referring to FIG. 4, the output signals of each light receiving element dS and dR in the camera 1 are amplified by an amplifier 5 equipped with an automatic gain control function, and then sent to a multiplexer channel device 6, where The outputs of the 12 light receiving elements are sequentially switched and sent to the AD converter 7. The AD converter 7 performs AD conversion on the output of the light receiving element input at a predetermined sampling period (4.8 mS in this example), and sends the result to a central processing unit (referred to as CPU) 8. CPU8 is
It controls the multiplexer/channel device 6 and the A/D converter 7, and also performs signal waveform pattern detection processing described later and various traffic information calculation processing described above. In addition to the program memory (not shown) that stores the execution program, the CPU 8 also stores data.
It is equipped with a memory 9. The processing device 2 has a camera 1
A filter circuit and an amplifier are provided to remove low frequency components of signals input from the input signal, but illustration thereof is omitted for the sake of brevity.

FIG. 5 shows an example of the waveform of a signal output from the light receiving element of the camera 1. This input signal is AD-converted by an A-D converter 7 every sampling period. The current A/D conversion result is defined as current data Dt. The current data Dt is increasing more than the previous data, but in order to determine whether it is decreasing or in equilibrium, it is necessary to find the deviation Δω of the current data Dt from the previous data. . Previous data to be used for determining this deviation Δω is defined as preprocessed data D0. Further, for the above determination, the reference amount to be compared with the deviation Δω between the current data Dt and the preprocessed data D0 is defined as a reference amount ω0. 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 ω0 are compared for each sampling period, and if the deviation Δω is greater than or equal to the reference amount ω0, or when the specified period T has elapsed, the current data Dt is used as the preprocessing data D0 and the preprocessing is performed. Update data D0. If the rise or fall of the signal is slow, the amount of increase or decrease may not reach the reference amount ω0 during the sampling period. A prescribed known T is introduced to detect such slow changes in the signal, and it is checked whether the amount of change reaches the reference amount ω0 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-D0≧ω0, it is regarded as an increasing state. If Dt-D0≦-ω0 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 preprocessed data D0. Also, even if the specified period T has elapsed, |Dt−D0
If |<ω0, it is regarded as an equilibrium state, and the current data Dt is adopted as the preprocessed data D0.

Referring to FIG. 5a, in a steady state where no vehicle is detected, the preprocessing data is 0 (time t1).
The preprocessed data at this time is assumed to be D01. The signal hardly rises during each subsequent sampling period, and even when the specified period T has passed (time t2), the deviation (Δω = Dt - D01) has not reached the reference amount ω0, so at time t1 The period between t2 and t2 is an equilibrium state. Therefore, the current data at this time is updated as preprocessed data D02.

Even in the next sampling period, the deviation Δω is the reference amount ω
It has not reached 0. Therefore, when one more period of sampling has elapsed (time t3), the deviation Δω is obtained and compared with the reference amount ω0. When two sampling periods have passed since time t2 (time t3), Δω≧ω0, so from time t2 to
t3 is an increasing state. Therefore, at time t3, the current data at that time is updated as preprocessed data D03. Even when one sampling period has passed since time t3 (time t4), Δω≧ω0 and it is determined that there is an increasing state, and the preprocessed data is updated as D04.

During the period of four sampling cycles after time t4 (regular cycle T), the signal is in an equilibrium state with almost no change, and the preprocessed data is changed to D05 at time t5. Between times t5 and t7, the signal rises rapidly and is determined to decrease at each sampling period, and the preprocessed data is updated (D06,
(denoted as D07). After time t7, an equilibrium state is reached again, and the preprocessing data is updated every prescribed period T (D08, etc.).

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

The output signal of the light receiving element of camera 1 is based on the shape of the vehicle,
Varies depending on color, speed, and other factors. Another waveform example is shown in Figure 5b. It will be appreciated that this signal waveform consists of a pattern of balance, increase, decrease, increase, decrease, balance, decrease, and balance.

This kind of signal waveform pattern detection processing is
To be executed by CPU 8, data memory 9 contains
Areas M1 to M11 are provided for storing various data. Elijah M1 has data Dt this time,
Elijah M2 has preprocessed data D0, Elijah M3
The deviation Δω is stored in the area M4, the previous signal state is stored in the area M5, and the reference amount ω0 is stored in the area M5. Area M6 is an area for storing waveform patterns, and has a large number of storage locations, each of which is assigned a consecutive address number n0 to nn. The address of the storage location where the next detection pattern is to be stored is specified by the contents of area M7.

The prescribed period T is stored in the area M8, and the equilibrium continuation determination amount C0 is stored in the area M9, and the areas M10 and M11 are used as a period counter C1 and an equilibrium counter C2, respectively. The period counter C1 counts whether the specified period T has been reached, and its contents are incremented by 1 every sampling period, and when the specified period T is reached, it is reset. The equilibrium counter C2 counts the number of times the equilibrium state continues, and is used to distinguish between a steady state where no vehicle is detected and an equilibrium state during vehicle detection such as from time t4 to t5. The equilibrium continuation determination amount C0 represents the number of times the equilibrium state continues, which serves as a criterion for this distinction, and a value larger than the maximum possible number of times the equilibrium state can be continued in vehicle detection is adopted. Then, when the content of the balance counter C2 is equal to or greater than the determination amount C0, it is determined that the steady state is present.

FIG. 6 shows the procedure of signal waveform pattern detection processing by the CPU 8. First, check whether the sampling period has elapsed (step (20)), and if it is within the sampling period, the input signal is
- AD conversion is performed by the D converter 7, and the AD conversion result is stored in the area M1 as current data Dt (step (21)). Then, the deviation Δω is calculated by subtracting the preprocessed data D0 from the current data Dt (step (22)), and the absolute value of this deviation Δω is compared with the reference amount ω0 to check the magnitude relationship between them (step (23)). )). The absolute value of the deviation Δω is the reference amount ω
If it is less than 0, the contents of the period counter C1 are +
1 (step (24)), and then it is checked whether the contents of this 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 is reset to clear its contents (step (26)), and an equilibrium state is determined (step (27)).
Then, it is checked from the contents of area M4 whether the previous time was in an equilibrium state (step (28)), and if the previous time was not in equilibrium but increasing or decreasing, the waveform pattern has changed, so The balanced pattern is stored at the address specified by the contents of area M7 (step (29)), and
The contents of area M7 are incremented by 1 in order to store the next waveform pattern (step (30)). After this, the current state is stored in area M4 and the process proceeds to step (31). If the previous state was in an equilibrium state, proceed directly 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 C0 is checked (step (32)). If the content of the equilibrium counter C2 is greater than or equal to the judgment amount C0, it is a steady state, so the area M
n0, which is the first address of area M6, is set in the contents of area M6 to prepare for the formation of a signal waveform pattern by the next vehicle (step (33)). After this, the process moves to step (46), where the current data Dt is converted to the preprocessed data D.
It is stored as 0 in area M2 and the process ends.
If step (32) is NO, also step (46)
Move to.

If the absolute value of the deviation Δω is greater than or equal to the reference amount ω0 (NO in step (23)), it is an increase or decrease, so the period counter C1 and the balance counter C2
Reset each (steps (35) and (36)),
Determine whether the deviation Δω is positive or negative (step (37)).
If the deviation Δω is positive, it is determined that the state is increasing (step (38)), and it is checked whether the previous state was increasing (step (39)). If the previous time was not in an increasing state, the increasing pattern is stored in area M6 (step (40)), and the contents of area M7 are incremented by 1 (step (41)). Then, the increased state is stored in area M4, and the process proceeds to step (46), where the current data Dt
is stored in area M2 as preprocessed data D0. If the previous time was an increase, proceed directly to step (46).

If the deviation Δω is negative, it is determined that it is in a decreasing state (step (42)), and as in the case of an increase, it is checked whether the previous state was in a decreasing state (step (43)), and the previous state is determined to be a decreasing state. Otherwise Elijah M6
The decreasing pattern is stored in the address specified by the contents of area M7 (step (44)), and
(step (45)), stores the decreased state in area M4, proceeds to step (46), and stores the current data Dt in area M as preprocessed data D0.
Store in 2. If there was a decrease last time as well, the process continues at step (46) and all processes are completed.

In this way, area M6 of data memory 9
The signal waveform patterns stored in the signal waveform patterns are used in various processes for measuring traffic flow, for example, to distinguish between a signal caused by a vehicle or a signal caused by the shadow of a vehicle. As shown in FIG. 5, the signal generated by the vehicle always rises from a steady state level, and the waveform pattern follows a pattern of equilibrium and then increase. On the other hand, the signal due to the shadow of the vehicle falls from the steady state level, and the waveform pattern becomes an equilibrium and then decreasing pattern. In this way, by changing the signal waveform pattern, it is possible to distinguish signals caused by vehicles from signals caused by the shadow of a vehicle, so signals caused by shadows can be eliminated and traffic flow information such as vehicle speed can be extracted from signals caused by vehicles. can be obtained accurately.

[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.
FIG. 6 is a flow chart showing the processing procedure when the waveform pattern detection device is executed by the CPU. 1...Camera (sensor), dS, dR, dS1~dS
6, dR1 to dR6... Light receiving element (sensor), 7...
...A-D converter (sampling circuit), 8...Central processing unit (CPU) (pattern discrimination device), 9...
...Data memory (memory), M1, M2, M8
...Memory area, C1...Period counter (counter), T...Regular cycle, Dt...Current data,
Do...preprocessing data, Δω...deviation, ω0...reference amount.

Claims (1)

[Claims] 1. A sensor 1, dS, dR that outputs an electrical signal representing a detected physical quantity, a sampling circuit 7 that samples the electrical signal output from the sensor at a predetermined sampling period, and the sampling circuit and a pattern discrimination device 8 that takes in the sampled data and discriminates its change pattern, and the pattern discrimination device allows
In the signal waveform pattern detection device for determining whether the output signal of the sensor is in an increasing state, decreasing state, or in an equilibrium state, the pattern determining device includes a memory 9 and a counter C.
1, and the memory has a first memory that stores the current data Dt.
, a second area M2 that stores preprocessed data Do that is previous data, and a third area M8 that stores a specified period T that is multiple times the sampling period, and the counter is continuous. The pattern discrimination device counts the number of sampling times, and the pattern discrimination device compares the current data and the preprocessed data at each sampling period, and increments the counter when the deviation Δω is smaller than a predetermined reference amount ω0; When the deviation is larger than the reference amount, it is determined that the deviation is in an increasing state or decreasing state depending on whether the deviation is positive or negative, and the preprocessing data of the second area is updated with the current data, and the counter is A signal waveform pattern detection device that determines an equilibrium state when the count value reaches a value representing the specified period, updates the preprocessed data of the second area with the current data, and further clears the counter. .