JP3094204B2 - Object detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detecting device, and more particularly to an object detecting device for detecting the entrance of a car in a parking lot or the like.

[0002]

2. Description of the Related Art Conventionally, the most usual method of detecting a car is performed by a loop coil buried under the floor. The loop coil method is suitable for detection of automobiles and the like because the reaction detection target is metal and the detection unit is under the floor and has no exposed portion, and is still frequently used. Ultrasonic sensors used in conventional parking prohibition systems are relatively frequently used as sensors for detecting the presence or absence of an automobile because the manufacturing unit price is easily reduced.

[0003]

In the conventional loop coil system as described above, when the parking space is adjacent to the passage in the parking lot due to the large shape of the coil and the low positional resolution. However, it cannot be installed so as to detect a car passing through the passage and not to detect a car to be parked. In addition, when two loop coils are buried for discriminating the direction of the vehicle, the shape becomes larger.
Furthermore, since the loop coil must be basically buried under the floor, a floor peeling work is required when installing the loop coil in an existing parking lot.

[0004] On the other hand, in the ultrasonic sensor, malfunctions are likely to occur when air flows due to wind or the like because of the use of sound waves. In order to prevent the malfunction, it is necessary to prevent the malfunction by, for example, averaging a large number of detection results, so that the response of the detection is deteriorated. Further, since the directivity of the sound wave is wide, when a large number of sensors are placed to detect the passage of a vehicle, the interval between the sensors must be considerably widened, and the shape becomes large.

The invention according to claim 1 has been made in order to solve the above-mentioned problems, and is easily mounted.
Another object of the present invention is to provide an object detection device with high detection accuracy. A third object of the present invention is to provide, in addition to the object of the first embodiment, an object detecting device capable of detecting a passing speed of an object more accurately.

[0006]

Means for Solving the Problems To achieve the above object, an invention according to claim 1 is described as follows. "An irradiation unit for irradiating light is provided at predetermined intervals in a traveling direction of a passing object. Two sensor means including a detection unit for detecting a change in the amount of reflected light from the object of the emitted light,
Calculating means for calculating a passing speed of the object, based on a time-series change in the amount of light detected by each of the sensor means, wherein the calculating means comprises: Waveform forming means for forming a first waveform and a second waveform based on a change in the amount of light detected by each, and a time for obtaining a maximum value of a cross-correlation between the first waveform and the second waveform. And a maximum correlation time calculating means that calculates the passing speed based on the calculated time and the predetermined interval.

Further, according to a third aspect of the present invention, there is provided a light emitting device, comprising: an illumination unit for irradiating light; a radiation unit for irradiating light; Two sensor means including a detecting unit for detecting a change in light amount, and a calculating means for calculating a passing speed of the object based on a time-series change in light amount detected by each of the sensor means. An object detecting device, wherein the calculating means comprises: a waveform forming means for forming a first waveform and a second waveform based on a change in the light amount detected by each of the sensor means; Based on the change of, the determination means for determining the passage start time and the passage end time of the object, and a passage time consisting of the passage start time and the passage end time is divided into a plurality of sections, and for each of the sections The first Calculating means for calculating the time for obtaining the maximum value of the cross-correlation between the waveform and the second waveform, and calculating the passing speed for each section based on the time calculated for each section and the predetermined interval To do it.

[0008]

As described above, according to the first aspect of the present invention, the change in the amount of reflected light detected by each of the sensors installed at predetermined intervals in the traveling direction of the passing object is represented by the waveform forming means. And the processing by the maximum correlation time calculating means, the passing speed of the object is calculated. Therefore, according to the first aspect of the present invention, the sensor can be easily installed, and the accuracy of detecting the passing speed is improved.

In addition, as described above, according to the third aspect of the present invention, since the passing speed is detected for each section obtained by dividing the passing time, in addition to the effect of the first aspect,
The detection accuracy of the passing speed is further improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a schematic configuration of a vehicle detecting device according to a first embodiment of the present invention. Referring to the figure, a vehicle detection device is provided with a sensor 34 for detecting that a vehicle 45 passes therethrough.
And a multiplexer 35 for receiving a plurality of outputs from the sensor 34 and controlling them in a multiplex manner, and an A / D converter 37 for converting an analog signal output from the multiplexer 35 to a digital signal. A CPU 39 for receiving digital signals output from the A / D converter 37 and performing various controls and calculations; a storage device 41 for storing data and the like calculated by the CPU 39;
9 includes a relay contact output for outputting a pulse through which one vehicle has passed to output the result calculated in 9 and an output device 43 such as a display or a printer for displaying the counting result. The CPU 39 controls the multiplexer 35 to output the signals input from the sensor 34 to the A / D converter 37 in a predetermined order.

The sensor 34 is provided with a pair of optical sensor portions 31a and 31b attached at a predetermined interval L in the traveling direction of the automobile 45, and has the same (N- 1) A pair of optical sensor units 32a,
32b to 3Na and 3Nb are provided at a distance W from each other in a direction perpendicular to the traveling direction of the automobile 45.

Here, L is 10 in this embodiment.
0 mm and W is 600 mm. Each of the optical sensor parts is an infrared light emitting element LED that irradiates infrared light to the road surface
And a position detecting element PSD that receives the reflected light of the emitted infrared light, measures the distance h to an object (car) on the road surface, and simultaneously obtains the reflected light amount V.

In the following description, it is assumed that the vehicle 45 has passed below the pair of optical sensors 31a and 31b. FIGS. 2A and 2B are diagrams showing, in chronological order, changes in the waveform of the reflected light amount of the optical sensor unit, where (1) is the reflected light amount obtained from the optical sensor unit 31a, and (2) is the optical sensor unit. 31b is the amount of reflected light obtained from 31b.

Referring to these figures, at time T ₁ , the time point at which the leading end of the vehicle 45 starts passing below the optical sensor section 31 a is shown, and at time T ₃ , the time at which the vehicle 4
5 shows a point in time when the rear end of the optical sensor 5 passes below the optical sensor 31a. Here, the portions S ₁ and S ₃ are below the lower limit of the amount of reflected light because the front glass 4
7 and the rear glass 49 because the irradiated infrared rays are not sufficiently reflected in these portions. Also, part of the S ₂ is has become larger than the upper limit of the amount of reflected light, because the infrared radiation applied by the mirror effect of the roof of the motor vehicle 45 is reflected almost entirely. Therefore, these parts S _{1 to} S
Data _3, as the data of the reflected light amount say not appropriate, these data are processed is excluded as data relative to the upper and lower limit values.

FIG. 2B shows the waveform of the amount of reflected light obtained at the optical sensor section 31b. In this embodiment, since the vehicle 45 passes under the optical sensor unit 33 at a constant speed, the waveform obtained by the optical sensor unit 31a and the waveform obtained by the optical sensor unit 31b are substantially the same. They have the same shape, but these waveforms are shifted in time. That is, the time T ₂ the leading end of the car 45 begins to pass under the optical sensor portion 31b has a post for the time T from the time T _1. Similarly, the rear end of the car 45 is the optical sensor 31b.
Time T ₄ is from time T ₃ time T finished passing through the lower portion of the
Only later. In other words, time T is for car 4
5 can be said to be the time required to pass the installation interval L of the pair of optical sensor units 31a and 31b.

FIG. 3 corresponds to the waveform data of the reflected light amount shown in FIG. 2, and shows a change in data of the distance of the detected object from the road surface. FIG. 3A illustrates an installation height H of the optical sensor unit 31a from the road surface.
Is a graph obtained by subtracting the distance h to the object obtained by the optical sensor unit 31a from the data and plotting the change with time. The parts R _{1 to} R ₃ correspond to S ₁ to R ₃ shown in FIG.
It is those corresponding to the portion of the S _3, the data for not a reliable property deals with hatched portion excluding these portions as the correct data. The reason why the data of the portions R _{1 to} R ₃ is excluded is to prevent a detection error of the sensor due to, for example, a case where the road surface is wet with water. The average height of the target object from the road surface is obtained based on the data indicated by hatching and the like, and when the average height falls within a predetermined range, the detected target object is an automobile. Recognize that.

FIG. 3 (2) is based on data on the distance to the object obtained by the optical sensor section 31b, and is shifted from the data of FIG. 3 (1) by a time T. Data. FIG. 4 is a diagram plotting the result of calculating the cross-correlation from the waveform of the reflected light amount in (1) of FIG. 2 and the waveform of the reflected light amount in (2) of FIG.

The cross-correlation is defined as:
First, the reference time of one piece of data is combined with the reference time of the other piece of data and multiplied together with a window function, and the result of the addition is plotted as data having a correlation time of 0. Then, the same calculation is performed by shifting the reference time of the other data by a unit time (25 ms in this example). Then, the obtained data is plotted corresponding to the shifted time. Thereafter, the same calculation is repeated with a further shift by a unit time to plot each data, and the plotted data is connected to form a correlation curve and search for the top.

In other words, when data of the same waveform is generated with a shift of time T, these cross-correlation values show the maximum value when the correlation time reaches T. As described above, when the maximum value Tm is obtained using the cross-correlation, in FIG. 2, the time T during which the vehicle 45 passes through the distance L between the optical sensor unit 31a and the optical sensor unit 31b is obtained.

The reason why the maximum correlation time is obtained to obtain the transit time between the sensors is that the time resolution inherent to the sensor can be improved. That is, when signal processing is performed in a state where the sensor signal is digitized, the signal sampling interval basically becomes a problem, and this interval becomes the minimum time resolution. In the case of an ON / OFF type (binarization) sensor, the time at which it can be determined as ON basically includes a predetermined error. In order to reduce this error to a negligible level, one-fifth of the time for the vehicle to pass between the two sensors
It is necessary to sample the signal at a short interval of about 1/10.

For example, when the speed of the vehicle is 60 km / h and the distance between the two points of the sensor is 100 mm, the time t1 at which the vehicle passes between the sensors is t1 = 100 / (6000).
(0000/3600) = 6 (ms). Assuming that 1/5 of the passing time is required for sampling, the sampling interval t2 is t2 = t1 / 5 = 1.2 (ms). That is, the sampling interval t2 must be 1.2 ms or less, and when the optical sensor unit 33 includes a large number of sensors, it is necessary to operate these sensors in a time division manner. For example, when 20 sensors are included, the time t3 required for sensing by each sensor is t3 = t2 / 20 = 0.06 (ms).

That is, sensing must be completed in 0.06 ms, and a sensor that responds at an extremely high speed is required. This result is inconsistent with the fact that the S / N ratio of the sensor must be increased, and as a result, it is difficult to achieve both. Therefore, as a countermeasure in such a case, if an attempt is made to increase the distance between the two sensors in the traveling direction, the overall shape of the sensor 34 becomes large, which is advantageous in terms of installation. Absent.

On the other hand, when the cross-correlation of the waveform data of the two sensors is used as described above, the correlation values are distributed around the maximum value, and the cross-correlation values obtained discretely in time are spline-interpolated. By doing so, the maximum correlation time is obtained with higher accuracy than the sampling interval. For example, assuming that a time resolution up to 1/4 of the sampling interval is obtained, in the above example, the sampling interval t2
Is t2 = t1 × 4 = 24 (ms), and the time t3 required for sensing of each sensor is t
3 = t2 / 20 = 1.2 (ms) That is, when the cross-correlation of the waveform data is used as in the embodiment of the present invention, the sampling interval of the sensor may be 24 ms or less, and the sensor can have a high S / N ratio.

Returning to FIG. 4, the maximum correlation value Tm is 1.25 ms from the obtained correlation curve. Here, the time required from time T ₁ to time T ₃ , that is, the total length of the reaction waveform is 48 m.
Assuming that s, the length L of the vehicle 45 in the passing direction is as follows: L = 48 × 100 / 1.25 = 3840 (mm) Then, the traveling direction of the automobile 45 is determined to be in the direction from the optical sensor unit 31a to the optical sensor unit 31b based on the time lag of the waveform data by the optical sensor units 31a and 31b. The same calculation is performed based on the waveform data obtained by the pair of optical sensor units 32a and 32b and the pair of optical sensor units 33a and 33b that have detected the change in the amount of reflected light. The lengths in the traveling direction of the vehicle 45 obtained by each of the pair of optical sensor units are defined as L ₂ and L ₃ . For example, L ₂ = 3550 (mm) and L ₃ = 3800
(Mm) is obtained, and based on these data, assuming that the plane projected area of the automobile 45 is S, S = (3840 + 3550 + 3800) / 3) × 3 ×
600 = 6714000 (mm ² ), and the plane occupied area of the car 45 that has passed can be determined from this value. Then, the plane occupied area is a value in a certain range if the passing object is a car,
The value of this area makes it possible to distinguish between another object (for example, a pedestrian or a motorcycle) and a car.

In the first embodiment, when the vehicle passes under the optical sensor, the passing speed is assumed to be constant. However, the passing speed is not always constant. Therefore, in the second embodiment of the present invention, the length of the vehicle body is accurately measured even when the vehicle passes under the sensor while changing the speed. As shown in FIG. 1 according to the first embodiment, a pair of optical sensor units 31a and 31b are arranged in the traveling direction of the vehicle. Assuming that the reflected light amounts at the optical sensor units 31a and 31b are Va and Vb, respectively, the waveforms of Va and Vb are obtained as shown in (1) and (2) of FIG. Then, judging from the change in the reflected light amount Va and the height of the object to be measured (automobile) from the road surface, the time T ₁ at which the vehicle starts passing under the optical sensor unit 31a and the time T _{3 at which the} vehicle ends passing are determined Ask for.
Vehicle took to pass through the optical sensor unit 31a time T becomes T _L = T ₃ -T _1. Next, this time T is divided into N equal parts (N is about 5 to 30).
Then, assuming that the equally divided time is ΔT, ΔT = T _L / N. Here, a series of window functions W ₀ as shown in FIG.
(T), W ₁ (t), W ₂ (t),... W _N (t) are assumed. W ₀ (t) is a unimodal function having a maximum value at time T ₁ . W _N (t) takes a maximum value at time T ₃ . Then, Wi (t) (i = 0, 1, 2,...,
N) is assumed to satisfy the following relationship.

Wi (t + i · ΔT) = W ₀ (t) When the cross-correlation is calculated from the signals Va and Vb of the pair of optical sensor units 31a and 31b using the window function Wi (t), the maximum correlation time τi is, for example, It is obtained as shown in FIG. Since the maximum correlation time τi car at the time (T ₁ + i · ΔT) is considered as the time taken to transit the optical sensor unit 31a, the inter-31b, the time (T ₁ + i · ΔT) speed Vi of the vehicle in the optical Assuming that the distance between the sensor units 31a and 31b is P, Vi = P / τi is obtained as shown in FIG. When the vehicle length TL is determined based on the speed Vi of the vehicle at each time, from the trapezoidal integration formula,

[0027]

(Equation 1)

## EQU1 ## As described above, even if the speed of the vehicle changes when passing through the sensor, the length of the vehicle can be accurately obtained. As described above, in the second embodiment, it is assumed that the passing speed when the vehicle passes under the optical sensor changes. Therefore, in the third embodiment of the present invention, an attempt is made to calculate the overall length of the vehicle when the vehicle passes under the sensor at a constant acceleration as an example of a change in speed, that is, an acceleration. Things.

As shown in FIG. 9, a vehicle having a total length of 4 m passes under the optical sensor at a passing speed of 2.5 m / s (9 km).
/ H) to 5 m / s (18 km / H) at a constant acceleration. In this case, since the total length of the vehicle is 4 m during the time T from time T ₁ to time T ₃ , T _L = 4 / ((2.5 + 5) / 2) = 1.07 s. At this time, the optical sensor unit 31a and the optical sensor unit 3
It is assumed that the reflected light waveforms Va and Vb obtained from 1b are obtained, for example, as shown in (1) of FIG. 10 and (2) of FIG. Here, the installation distance between the optical sensor unit 31a and the optical sensor unit 31b is 100 mm. Assuming that six window functions (N = 5) are used to obtain the cross-correlation between the waveform Va and the waveform Vb, ΔT is about 0.213 seconds because ΔT = T _L / N, and the graph of the window function is FIG.
W ₀ (t) to W ₅ (t) shown in FIG.
When the maximum correlation time τi (i = 0, 1, 2, 3, 4, 5) is obtained, assuming that the time resolution is 5 ms, τ ₀ = 40 ms, τ ₁ = 35 ms, τ ₂ = 30 ms, τ
₃ = 25 ms, τ ₄ = 20 ms, τ ₅ = 20 ms. FIG. 12 is a diagram corresponding to each passing time divided into five equal parts. Therefore, the maximum correlation time τi
, V ₀ = 2.5 m / s, V ₁ = 2.9 m / s, V ₂ = 3.
3 m / s, V ₃ = 4.0 m / s, V ₄ = 5.0 m / s,
V ₅ = 5.0 m / s FIG. 13 is a diagram corresponding to each passing time divided into five equal parts. Thus, when the measured value of the length of the vehicle is calculated by substituting the value of the passing speed Vi and the value of the equally divided time ΔT into the expression (1) shown in the second embodiment, Lc = 4.0 m In addition, it is possible to accurately measure the entire length of a vehicle whose passing speed changes.

In the above embodiment, the number of window functions is fixed and the interval (ΔT) of the window functions is variable. On the contrary, the interval of the window functions is fixed and the number of window functions is variable. It may be calculated. Further, in the above-described embodiment, the target is a car, but the present invention is not limited to a car and can be similarly applied to any other passing object that causes a change in the amount of reflected light.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle detection device according to a first embodiment of the present invention.

FIG. 2 shows the optical sensor unit 31a and the optical sensor unit 31 shown in FIG.
FIG. 9 is a diagram showing a waveform of a reflected light amount obtained by each of FIGS.

FIG. 3 shows the optical sensor unit 31a and the optical sensor unit 31 shown in FIG.
FIG. 9 is a diagram showing a change in the distance of the reflecting surface of the passing vehicle from the road surface obtained by each of FIGS.

FIG. 4 is a diagram showing a correlation curve obtained by calculating a cross-correlation of each of the waveforms of the reflected light amounts shown in (1) and (2) of FIG.

FIG. 5 is a diagram showing a waveform of a reflected light amount obtained by each of an optical sensor unit 31a and an optical sensor unit 31b according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a window function used in the second embodiment of the present invention.

FIG. 7 is a diagram showing a distribution of a maximum correlation time calculated in the second embodiment of the present invention.

8 is a diagram showing a distribution of a passing speed of a vehicle at each passing time based on the maximum correlation time shown in FIG. 7;

FIG. 9 is a diagram showing a change in a passing speed of an automobile according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a waveform of a reflected light amount obtained by each of an optical sensor unit 31a and an optical sensor unit 31b according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a window function according to a third embodiment of the present invention.

FIG. 12 is a diagram showing a distribution of a maximum correlation time obtained by cross-correlation according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a distribution of passing speeds at each passing time using the maximum correlation time of FIG. 12;

[Explanation of symbols]

 31a, 31b to 3Na, 3Nb Optical sensor unit 34 Sensor 39 CPU 41 Storage device 45 Car Note that the same reference numerals in the drawings indicate the same or corresponding parts.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tanigawa 14th Yoshida Kawaramachi, Sakyo-ku, Kyoto Kinki District Invention Center Building Inside Giken Trading Co., Ltd. (56) References JP-A-4-247599 (JP, A) JP-A-3-14198 (JP, A) JP-A-59-183498 (JP, A) JP-A-55-162200 (JP, A) JP-A-54-125086 (JP, A) JP-A 52-143080 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G08G 1/04-1/16

Claims (4)

(57) [Claims] An illumination unit for irradiating light and a detection unit for detecting a change in the amount of reflected light of the emitted light from the object are provided at predetermined intervals in a traveling direction of a passing object. An object detection device comprising: two sensor units including: a calculating unit configured to calculate a passing speed of the object based on a time-series change in the amount of light detected by each of the sensor units. A calculating unit configured to form a first waveform and a second waveform based on a change in the amount of light detected by each of the sensor units; and a cross-correlation between the first waveform and the second waveform. An object detection device, comprising: maximum correlation time calculation means for calculating a time for obtaining the maximum value of the above, and calculating the passing speed based on the calculated time and the predetermined interval. 2. A determining means for determining a passing time consisting of a passing start time and a passing end time of the object based on a change in the amount of light detected by at least one of the sensor means, and the calculated passing speed. The object detection device according to claim 1, further comprising: a detection unit configured to detect a length of the object in the traveling direction from the determined passage time. 3. An irradiating unit which is installed at predetermined intervals in a traveling direction of a passing object and irradiates light, and a detecting unit which detects a change in the amount of reflected light of the irradiating light from the object. An object detection device comprising: two sensor units including: a calculating unit configured to calculate a passing speed of the object based on a time-series change in the amount of light detected by each of the sensor units. A calculating unit configured to form a first waveform and a second waveform based on a change in the light amount detected by each of the sensor units; and Determining means for determining a passage start time and a passage end time; dividing a passage time consisting of the passage start time and the passage end time into a plurality of sections; for each of the sections, the first waveform and the second Phase of the waveform And a calculating means for calculating a time to obtain the maximum value of the correlation, based on said a predetermined distance and the time that is calculated for each of the sections, and calculates the rate of passage of each of the sections, the object detecting device. 4. A detecting means for detecting a length of the object in the traveling direction of each of the sections from a time defining the section and a passing speed calculated for each of the sections, and a length detected for each of the sections. By adding
4. The object detection device according to claim 3, further comprising a detection unit configured to detect an entire length of the object in the traveling direction.