JP7037169B2 - Object detection device and object detection method - Google Patents

Description

The present invention relates to an apparatus and a method for detecting an object.

In recent years, the demand for sensors has been increasing particularly in the fields of crime prevention security and robots, and various sensors have been devised as shown in Patent Document 1, for example.

Japanese Unexamined Patent Publication No. 2014-7629

However, the proximity sensor disclosed in Patent Document 1 has a problem that the distance to a detectable object is only about 10 to 30 cm at the most.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an object detection device and an object detection method capable of detecting an object in a wider range.

In order to solve the above problems, the present invention presents a coordinating means that expresses the reflection coefficient measured by an antenna that generates an electromagnetic field with coordinates on a complex plane, and a detection object according to the coordinates generated by the coordinating means. Provided is an object detection device provided with a detection means for detecting the above.

Further, in order to solve the above problems, the present invention first measures the reflectance coefficient of an antenna that generates an electromagnetic field in advance in a state where there is no object to be detected, and expresses the measured reflectance coefficient by coordinates on a complex plane. Step, and in a state where there is a detection target, the reflection coefficient is measured while changing the distance between the antenna and the detection target, and the measured coordinates of the reflected coefficient on the complex plane and the first By comparing with the above coordinates obtained in the step, an object detection method including a second step of detecting a detection target is provided.

According to the present invention, it is possible to provide an object detection device and an object detection method capable of detecting an object in a wider range.

It is a block diagram which shows the structure of the object detection apparatus 1 which concerns on embodiment of this invention. It is a block diagram which shows the structure of the object detection part 14 shown in FIG. It is a flowchart which shows the object detection method which concerns on embodiment of this invention. It is a figure for demonstrating the coding in step S1 shown in FIG. It is a 1st figure for demonstrating the addressization in step S2 shown in FIG. It is a 2nd figure for demonstrating the coding in step S2 shown in FIG. It is a figure for demonstrating the detection method of the detection object in step S3 shown in FIG. It is a 1st figure for demonstrating a specific example of the object detection method shown in FIG. It is a 2nd figure for demonstrating a specific example of the object detection method shown in FIG. It is a 3rd figure for demonstrating a specific example of the object detection method shown in FIG. It is a schematic diagram showing the relationship between the electromagnetic field generated from the antenna and the object to be detected. FIG. 11A shows an electromagnetic field of a spherical wave generated from a wave source, and FIG. 11B shows an actual electromagnetic field from the wave source. Indicates a case where is generated. It is a figure which shows the transmission line model which showed the relationship shown in FIG. It is a graph which shows the reflection coefficient S (L) obtained from Table 1. It is a figure for demonstrating the method of detecting the detection object according to the relationship between the irradiation range of the electromagnetic field generated from an antenna, and the position of the detection object.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, the same reference numerals indicate the same or corresponding parts.

FIG. 1 is a block diagram showing a configuration of an object detection device 1 according to an embodiment of the present invention. As shown in FIG. 1, the object detection device 1 is connected to an antenna 3 that generates an electromagnetic field 5 at an input / output terminal 2, and is connected to a sine wave generator 11, a matching circuit 12, a reflectance coefficient measuring unit 13, and an object detecting unit 14. To prepare for.

Here, the sine wave generator 11 generates a sine wave signal. Further, the matching circuit 12 is connected between the sine wave generator 11 and the input / output terminal 2, and impedance matching is achieved between the antenna 3 externally connected to the input / output terminal 2 and the sine wave generator 11. Further, the reflection coefficient measuring unit 13 is connected to the matching circuit 12 and measures the reflection coefficient in the antenna 3. Further, the object detection unit 14 is connected to the reflectance coefficient measuring unit 13 to detect the detection target object 4, which will be described in detail below.

Since the matching circuit 12 is a circuit that matches in the environment before shipping to the market, the object detection device 1 operates in a state deviated from perfect matching in the actual usage environment. Further, when the reflection coefficient is measured without generating the electromagnetic field 5 from the antenna 3 as a real wave, the backflow of power to the sine wave generator 11 is prevented instead of the matching circuit 12, and the reflection coefficient is increased. An adjustment circuit having a function of adjusting a position on a complex plane is used.

FIG. 2 is a block diagram showing the configuration of the object detection unit 14 shown in FIG. As shown in FIG. 2, the object detection unit 14 includes an input / output terminal 21, a bus 22 connected to the input / output terminal 21, and a coordinating unit 23, a detection unit 24, and a storage unit 25 connected to the bus 22, respectively. , A display unit 26, and an operation unit 27. The object detection unit 14 is connected to the reflectance coefficient measuring unit 13 at the input / output terminal 21.

FIG. 3 is a flowchart showing an object detection method according to an embodiment of the present invention. Hereinafter, the object detection method according to the embodiment of the present invention will be described in detail with reference to FIG.

In the following, as an example, the case where the above-mentioned object detection method is realized by the operation of the object detection device 1 shown in FIGS. 1 and 2 will be described, but this method is not limited to the object detection device 1 and can be widely applied. Needless to say.

In step S1, the reflectance coefficient measuring unit 13 measures the reflectance coefficient in the antenna 3 that generates the electromagnetic field 5 in advance in a state where there is no detection object 4, and the coordinating unit 23 measures the reflectance coefficient under the normal learning mode. The reflectance coefficient measured by the unit 13 is expressed by the coordinates on the complex plane and mapped on the complex plane.

Here, in the complex plane, the first and second coordinate axes are the real axis and the imaginary axis as shown in FIG. 4, but as described above, in the sensing area by the electromagnetic field 5 generated from the antenna 3. In the absence of the detection object 4, the reflection coefficient is mapped to the stop point C0 in the complex plane.

Next, in step S2, the reflectance coefficient measuring unit 13 measures the reflectance coefficient in advance while changing the distance between the antenna 3 and the detection object 4 in a state where the detection object 4 is present, and the coordinate conversion unit 23 approaches the object. Under the time learning mode, the reflectance coefficient measured by the reflectance coefficient measuring unit 13 is expressed by the coordinates on the complex plane and mapped on the complex plane as a function of the distance.

Here, under the object approach learning mode, as shown in FIG. 5, the reflectance coefficient is around the central axis CA in a three-dimensional space having a third coordinate axis orthogonal to the complex plane as an objective distance. It is mapped in a spiral with a wide base formed. When the spiral map shown in FIG. 5 is projected onto the complex plane, a spiral map as shown in FIG. 6 can be obtained.

At this time, for example, as the detection object 4 moves closer to the antenna 3 from a distance, that is, as the distance L from the detection object 4 to the antenna 3 decreases, as shown in FIGS. 5 and 6, the complex plane The radius of gyration of the locus of the reflectance coefficient by mapping in is large.

Therefore, when the distance L becomes longer as the distances L1, L2, and L3 in order, if the points on the complex plane to be mapped are the points M1, M2, and M3, respectively, the points M1, M2, and M3 and the stop point C0. The distance on the complex plane, that is, the turning radius of the above, becomes shorter as the radii R1, R2, R3 in order as shown in FIG.

From this, in the coordinate conversion unit 23, the objective distance and the turning radius corresponding to the respective points M1, M2, M3 are shown on the graph in which the horizontal axis is the objective distance and the vertical axis is the turning radius on the complex plane in the above. To generate the function F as shown in FIG. 7 by plotting each of them.

On the other hand, when the detection object 4 approaches the antenna 3, that is, when the distance L decreases, and conversely, when the detection object 4 moves away from the antenna 3, that is, when the distance L increases. , The rotation direction is opposite in both the spiral locus by mapping in the three-dimensional space and the spiral locus by the projection of this locus onto the complex plane.

The map, graph, and rotation direction data generated by the coordinate conversion unit 23 as described above are stored in the storage unit 25 and displayed on the display unit 26 in response to the operation of the operation unit 27 by the user.

Next, in step S3, the detection target is detected by comparing the coordinates of the reflection coefficient measured by the reflection coefficient measuring unit 13 on the complex plane with the coordinates obtained in step S2.

More specifically, for example, in the object detection mode, the reflectance coefficient measured by the reflection coefficient measuring unit 13 is represented by the coordinates on the complex plane by the coordinating unit 23 and then mapped to the complex plane. The detection unit 24 detects the detection target object 4 by comparing it with the map on the complex plane obtained in step S2. Note that the detection unit 24 does not have the detection object 4 when the map drawn on the complex plane by the coordinate conversion unit 23 under the same mode has only the stationary point C0 as shown in FIG. Presumed to be.

Here, the detection unit 24 estimates the objective distance L by using the radius of gyration R on the complex plane obtained in the object detection mode as an argument of the function F, and the radius of gyration R is predetermined. When the value becomes larger than the value, the approach of the detection object 4 is detected. Further, the detection unit 24 stores the rotation direction of the locus mapped in the three-dimensional space shown in FIG. 5 or the locus on the complex plane shown in FIG. 6 in the same mode in step S2. The increase / decrease in the objective distance is also estimated by comparing with the data regarding the direction.

As described above, the data on the objective distance and the presence / absence of approach estimated by the detection unit 24, and the data indicating the increase / decrease in the objective distance are displayed on the display unit 26 according to the operation of the operation unit 27 by the user. , Stored in the storage unit 25.

Hereinafter, specific examples of the above-mentioned object detection method will be described in detail.

The graph shown in FIG. 6 has a counterclockwise spiral shape when the detection object 4 approaches the antenna 3, while it has a clockwise spiral shape when the detection object 4 moves away from the antenna 3. Then, in these spiral loci, the distance (objective distance) from the antenna 3 to the detection object 4 makes one rotation in the complex plane for each half wavelength of the electromagnetic field 5.

That is, assuming that the wavelength of the electromagnetic field 5 is λ, when the stationary point of the complex plane is the origin, the change of one rotation (2π) corresponds to the spatial movement of λ / 2 by the detection object 4.

For example, when the wavelength λ is 100 cm (cm), the locus of the reflectance coefficient on the complex plane obtained when the detection object 4 moves from the objective distance of 0 cm to 50 cm is as shown in FIG. .. In addition, this locus connects 11 measurement points (indicated by dots in the figure) indicating the reflectance coefficient measured every time the objective distance changes from 0 cm to 5 cm in order, and clockwise as described above. It becomes a spiral shape.

Here, as shown in FIG. 8, assuming that the complex coordinates during movement are the coordinates (r2, i2) and the stationary point is the coordinates (r1, i1), the phase θ at the objective distance of 10 cm is the following equation ( It can be calculated by 1).

Similarly, assuming that the complex coordinates during the next movement are the coordinates (r3, i3) shown in FIG. 9, the phase Φ at an objective distance of 15 cm can be calculated by the following equation (2).

Therefore, since the phase difference Δθ between each point consisting of the difference between the phase θ and the phase Φ is obtained, the moving distance ΔL of the detection target object 4 is calculated by the following equation (3).

It should be noted that the positive or negative of the phase difference Δθ described above makes it possible to distinguish whether the detection object 4 approaches or moves away from the antenna 3.

By the way, in the above example, since the origin of the complex plane and the stationary point are close to each other, the difference between the phase calculated around the origin and the phase centered on the stationary point is not conspicuous. However, the positional relationship between the origin and the stationary point of the complex plane changes greatly depending on the height of the antenna 3 from the ground.

Therefore, when the origin and the stationary point of the complex plane are separated from each other, the change in the phase angle when the detection object 4 moves by the length of half a wavelength of the electromagnetic field 5 becomes narrow as shown in FIG. That is, as shown in FIG. 10, the phase θ seen from the stationary point changes by 2π due to the movement of the half wavelength as described above, but the phase θ ′ seen from the origin does not change by π / 2.

From this, the equation (3) can be effectively used by using the phase θ with respect to the stationary point.

Therefore, as described above, the positional relationship between the origin and the stationary point of the complex plane changes greatly depending on the height of the antenna 3 from the ground. Therefore, the graph obtained after installing the antenna 3 is automatically displayed. If the stationary point is transitioned to the origin by calibrating, the moving distance ΔL can be obtained by the equation (3) using the above phase θ.

In the above, the coordinate conversion unit 23 shown in FIG. 2 expresses the measured reflection coefficient to the coordinates on the complex plane and maps it on the same plane, but does not necessarily draw by the mapping. Also good. That is, the coordinate conversion unit 23 can detect the object by learning the coordinates of the expressed stationary point and storing them in the storage unit 25. Specifically, the complex distance on the complex plane corresponding to the above-mentioned turning radius can be calculated by using the stored coordinates of the stop point and the coordinates corresponding to the observed reflection coefficient, and the said. The above-mentioned phase θ centered on the stop point can also be calculated by Eq. (1).

In the following, as an object detection method according to another embodiment of the present invention, a method of detecting an object without performing learning when approaching an object in step S2 shown in FIG. 3, that is, step S1 shown in FIG. A method of detecting the objective distance and the traveling direction of the object to be detected by simply grasping the stationary point will be described.

First, consider the case where one detection target is included in the electromagnetic field generated from the antenna. In this case, as the simplest example, consider a spherical wave from the wave source shown in FIG. 11 (a). However, in reality, as shown in FIG. 11B, the electromagnetic field generated from the wave source is spatially localized. In the figure, L indicates the distance between the wave source and the object.

Here, as shown in FIGS. 11A and 11B, a uniform space extends from the wave source to the detection target, and therefore, as shown in FIG. 12, a uniform transmission line 31 A model in which a load 30 is connected to the end of the can be considered.

In FIG. 12, _SO indicates the reflectance coefficient at the load end, L indicates the distance to the load 30, and S (L) indicates the reflectance coefficient at a point separated from the load end by a distance L. At this time, it is known that the following equation (4) holds between the reflection coefficient S (L) and the reflection coefficient S _O.

In Eq. (4), k is the wave number, λ is the wavelength, and j is the imaginary unit.

Considering that the spherical wave shown in FIG. 11A spreads as it moves away from the wave source, the amount of reflection of the wave is large when there is an object near the wave source, and the object is generated from the wave source. The amount of reflection decreases as the distance increases.

Therefore, it can be assumed that the reflectance coefficient S _O at the load end is a function that monotonically decreases with respect to the objective distance L, and the following equation holds.

The reflection of a wave by an object at a distance L from the wave source is related to the contrast between the area A of the object on the plane perpendicular to the traveling direction of the wave and the area 4πL ² of the equiphase plane at the distance L. When the distance L is sufficiently large, the following equation holds.

Here, when the distance L approaches 0, it covers half of the radiation surface of the wave source. Therefore, it is assumed that the relationship shown by the following equation is established for the reflection coefficient _SO .

Then, in consideration of the above equations (6) and (7), the following equation is defined as the reflection coefficient at the load end.

Here, assuming that the size of the object is about the wavelength, the reflection coefficient _SO at the load end can be expressed by the following equation, where the area A is λ ² .

On the other hand, the reflectance coefficient S (L) at a point separated by a distance L from the load end is expressed by the following equation.

In this equation (10), the degree of interaction between the electromagnetic field and the object to be detected is defined as the amplitude _SO (L), and the phase transition due to the uniform space portion is defined as the complex unit circle.

In the following, the behavior of the reflection coefficient S (L) when the distance (objective distance) L to the load end changes from 0 to half wavelength (λ / 2) by λ / 12 will be considered. When the order n changes by 1 from 0 to 6, each term required for calculating the reflection coefficient S (L) is shown in Table 1 below.

Then, the reflection coefficient S (L) calculated from each term in Table 1 is graphed as shown in FIG. As shown in FIG. 13, as the order n increases, it moves clockwise on the complex plane and the radius of gyration also decreases. At this time, the phase term 2 kL changes from 0 to 2π and makes one rotation, and the distance L increases by half a wavelength (λ / 2).

From this, the increase in the distance L is obtained from the increase in the phase term, which means that the distance L increases when the graph is drawn clockwise, and the distance L decreases when the graph is drawn counterclockwise. become.

By the way, when the detection object 4 moves back and forth in front of the antenna 3, the above explanation by the model shown in FIG. 12 can be applied. This is because the property of the amplitude _SO (L) at the load end, which indicates the degree of interaction between the electromagnetic field 5 generated by the antenna 3 and the object to be detected 4, has the same property as that of the point wave source. However, unlike the spherical wave, the energy distribution of the equiphase plane is not uniform but spatially biased as shown in FIG. 11 (b). Therefore, the above equation (6) is an element of the area ratio. In addition, it is necessary to consider the factors related to the overlap integral between the energy distribution function and the area occupied by the object. This bias in energy distribution and the degree of overlap according to the position of the object are called interactions.

However, as shown in FIG. 14, when the detection object 41 is present in the region A1 outside the region A2 where the electromagnetic field 5 is localized, the magnitude of the interaction becomes small, so that the amplitude _SO (L) Does not have the property of simply decreasing monotonically with respect to the distance L.

Therefore, the generation range (localized state) of the electromagnetic field 5 is controlled by changing the height of the antenna 3 or changing the angle such as tilting the antenna 3 downward by an angle α from the horizontal plane as shown in FIG. Therefore, by performing the object detection as described above, the presence or absence of the object can be detected according to the change in the magnitude of the amplitude _SO (L), that is, the complex radius from the above-mentioned stop point.

From the above, according to the object detection device and the object detection method according to the embodiment of the present invention, it is possible to detect the object to be detected in a wider range, and it is expected that the object will be covered with a sparse substance such as rice. It can be detected even in a bad environment.

1 Object detection device 14 Object detection unit 23 Coordination unit 24 Detection unit 25 Storage unit

Claims (12)

Coordination means that generate coordinates with the real and imaginary parts of the complex reflectance coefficient measured in the antenna that generates the electromagnetic field as the values of the real and imaginary axes on the complex plane, respectively.
An object provided with a detection means for detecting an object to be detected by comparing the coordinates generated with the object to be detected by the coordinating means with the coordinates generated without the object to be detected. Detection device. The object detection device according to claim 1, wherein the coordinate-coding means maps the coordinates on the complex plane. The coordinating means maps a stationary point on the complex plane obtained in the absence of the object to be detected.
The detection means further reaches the antenna of the detection object according to the correspondence between the distance to the antenna of the detection object and the distance of the point drawn by the mapping from the stationary point. The object detection device according to claim 2, wherein the distance is estimated. The object detection device according to claim 3, wherein the detection means estimates the distance after transitioning the stationary point mapped by the coordinate conversion means to the origin of the complex plane. The second aspect of claim 2, wherein the detection means further estimates an increase or decrease in the distance according to a correspondence relationship between an increase or decrease in the distance between the antenna and the detection object and a rotation direction of a locus by the mapping. Object detector. In the absence of a detection object, the complex reflectance coefficient of the antenna that generates the electromagnetic field is measured in advance, and the measured real and imaginary parts of the complex reflectance coefficient are set to the values of the real axis and the imaginary axis on the complex plane, respectively. The first step to generate as coordinates ,
In a state where the detection target is present, the complex reflection coefficient is measured while changing the distance between the antenna and the detection target, and the measured real part and imaginary part of the complex reflection coefficient are respectively on the complex plane. An object detection method including a second step of detecting an object to be detected by comparing the coordinates of the real axis and the imaginary axis with the coordinates obtained in the first step. In a state where the detection target is present, the complex reflection coefficient is measured in advance while changing the distance between the antenna and the detection target, and the measured real part and imaginary part of the complex reflection coefficient are functions of the distance, respectively . Further includes a third step of generating as coordinates to be the values of the real and imaginary axes on the complex plane.
In the second step, the detection target is detected by comparing the measured coordinates of the complex reflectance coefficient on the complex plane with the coordinates obtained in the third step. Item 6. The object detection method according to Item 6. In the first and third steps, the coordinates are mapped on the complex plane.
The object detection method according to claim 7, wherein in the second step, the object is detected by comparing the maps obtained in the first step and the third step. In the first step, the stationary point on the complex plane is stored.
In the third step, the correspondence between the distance to the antenna in the detection object and the distance of the point drawn by the mapping from the stationary point is stored.
The object detection method according to claim 8, wherein in the second step, the distance to the antenna in the detection target is estimated in light of the correspondence. The object detection method according to claim 9, wherein in the second step, the stationary point is transitioned to the origin of the complex plane and then the distance is estimated. The object detection method according to claim 6, wherein in the second step, the reflection coefficient is measured by changing the generation range of the electromagnetic field. In the third step, the correspondence between the increase / decrease in the distance and the rotation direction of the locus due to the mapping is stored, and the correspondence is stored.
The object detection method according to claim 8, wherein in the second step, an increase or decrease in the distance in the detection object is estimated according to the correspondence relationship stored in the third step.

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