JP2835705B2 - Object detection method by microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an object, and more particularly to a method for detecting the position and presence of an object using a microwave as a detection medium.

[0002]

2. Description of the Related Art Conventionally, an object detection device using laser light or infrared light has been widely used at a factory production site or a work site to detect the presence or position of a moving object such as a processed product. ing. However, such a method using light has a drawback that, for example, in a use environment where steam mist and oil mist are present at high temperature and high humidity, the sensitivity is remarkably reduced and detection becomes difficult. Therefore, instead of the conventional optical system, microwaves are used as a detection medium of the object detection device. The detection principle of such an object detection method using microwaves is shown in FIGS.
This will be described with reference to FIG.

FIG. 3 is a schematic diagram showing a method of detecting an object by a direct microwave wave. As shown,
The microwave transmitter 61 and the microwave receiver 64 are
The microwave transmitter 6 is disposed at an appropriate distance from the microwave transmitter 6
The microwave receiver 64 is configured to directly receive the microwave 62 transmitted by the microwave receiver 1. Then, the detected object 65 moves in the Z direction from the point N1 in the drawing, and at the time when its tip passes through the point 0, the microwaves 62 (from the microwave transmitter 61 to the microwave receiver 64) proceed straight. (Direct wave) is cut off, and the microwave receiver 64 detects an input change due to the cutoff of the microwave 62,
The presence and position of the detected object 65 are detected.

FIG. 5 is a schematic view showing a method of detecting an object by a reflected microwave. As shown, a microwave transmitter 71 and a microwave receiver 74
Are arranged at a distance (L70) and inclined so as to face inward. Then, when the detected object 75 moving in the arrow Y direction passes through the intermediate point of the distance L70, the microwave transmitted by the microwave transmitter 71 is reflected by the detected object 75, and the reflected light is reflected. When the microwave 73 is received by the microwave receiver 74, the position or presence of the detected object 75 is detected.

Further, a microwave transmitter and a microwave receiver are provided, and the microwaves emitted from one of the microwave transmitters are received by the other microwave receiver, whereby the positional relationship between the microwave receivers is established. For example, a crane facility 80 in a factory as shown in FIG. 6 is conceivable. As shown, a plurality (2 in the example of the figure)
Base) A self-propelled crane A82 and a self-propelled crane B83 are movably incorporated on a rail 81. When the transmission range of the microwave transmitted from the microwave transmitter 84 of one crane and the reception range of the microwave receiver 85 of the other crane overlap, both recognize the position of each other. , To prevent collision.

[0006]

The microwave as a detection medium has a single wavelength, unlike a light wave such as a laser beam, which has a complex wavelength. There was a problem. First, in the method for detecting the interruption of the microwave by the detected object as shown in FIG. 3, the microwave receiver 64 is directly incident from the microwave transmitter 61 and emitted directly. In addition to 62, a reflected wave 63 reflected by the surface of the leading end of the approaching detected object 65 enters. Therefore, the microwave receiver 64 receives a composite wave of the direct incident wave 62 and the reflected wave 63 as reception power.

Here, the following relationship is established between the direct incident wave 62 and the reflected wave 63 when the propagation distance D1 of the direct incident wave 62, the propagation distance (D2 + D3) of the reflected wave 63, and the wavelength λ of the microwave. Expression (A) [(D2 + D3) -D1] / λ (A) (λ: wavelength of microwave) exists. In the relational expression (A), when a remainder occurs, it indicates that a phase shift occurs between the direct incident wave 62 and the reflected wave 63, which means that the direct incident wave 62
And the reflected wave 63 cause interference. When there is interference, the direct incident wave 62 and the reflected wave 63
The combined wave increases and decreases with a phase shift from the received power of the direct incident wave 62 alone.

In the above-described method for detecting the interruption of the microwave, the operation level of the receiver is set to Th60, and the microwave receiver 64 is operated when the received power becomes equal to or less than Th60. Generally, local decrease in received power due to the interference becomes noise,
Even when the tip of the detected object 65 has not yet reached the point O, it may operate. For example, FIG. 4 shows an example of the received power PW of the microwave receiver 64 when there is interference. As shown in the figure, the received power PW locally decreases with the position of the detected object 65. ing. In such a state, even before the tip of the detected object 65 reaches the point 0, for example, between the point N2 and the point N3 and between the point N4 and the point O, the received power PW of the microwave receiver 64 is reduced. There is a problem that the operation becomes lower than the operation level and the microwave receiver 64 operates. Similarly, the detected object 65
Even between the point P2 and the point P3 where the rear end has already passed the point 0, the reflected wave from the rear end of the detected object 65 enters and interferes, so that the microwave receiver 64 also operates. This malfunction due to the incidence of the reflected wave from the rear end of the detected object 65 is particularly important when the detected object continuously approaches.

[0009] Such interference is caused by the object 65 to be detected.
This also occurs due to the shape of the front end or the rear end of the camera, the vertical movement during movement, and the like, causing the same malfunction. Furthermore,
In some cases, a reflected wave from an object in the surrounding environment may enter the microwave receiver 64, and as a result, a similar malfunction may occur.

[0010] Further, the above-mentioned problem of interference becomes a similar problem in the crane equipment 80 in the factory described with reference to FIG. That is, the distance detection and collision prevention of the self-propelled cranes 82 and 83 are performed based on the direct wave 87 of the microwave, but other devices and walls disposed in the factory become the reflecting objects 86, and As a result of the reflected wave 88 being incident on the microwave receiver 85, the reception power is reduced due to the same interference as described above, and a malfunction occurs.

On the other hand, in the method of detecting a reflected wave as shown in FIG. 5, the reflected wave is transmitted from a microwave transmitter 71,
In addition to the reflected wave 73 reflected on the surface of the detected object 75 approaching in the direction of the arrow W, there is also a direct incident wave 72 that is not reflected and directly reaches the microwave receiver 74 from the microwave transmitter 71. . As a result, as described above, the reflected wave 73 and the directly incident wave 72 interfere with each other, resulting in a local decrease in the received power, thereby causing a malfunction that the microwave receiver 74 malfunctions. This becomes more remarkable when the microwave transmitter 71 and the microwave receiver 74 are arranged close to each other. Furthermore, as a result of arranging the transmitter and the receiver as far apart as possible to minimize the adverse effect caused by the phase difference between the reflected wave 73 and the directly incident wave 72, the microwave transmitter 71 and the microwave receiver There is a drawback that the distance between the 74 is long. In addition, for example, when the present invention is applied to an apparatus that detects the detection target object 75 placed on a belt conveyor, the position (height) of the reflection surface differs depending on the size of each detection target object 75, so that the reflection position is constant. A configuration for emitting microwaves toward the bottom surface of the detection object 75 must be adopted, and there is a problem that the configuration of the device is limited.

As described above, in the conventional object detection method using a microwave, reflected waves having different phases from a moving object and a surrounding environment enter the microwave receiver and are emitted from the microwave transmitter. As a result of interference with the detected microwave for detection, a local decrease in the received power occurs, causing a malfunction, and there is a problem that sufficient detection accuracy cannot be obtained. The present invention has been made to solve such problems and disadvantages, and an object of the present invention is to provide a microwave-based object detection method capable of detecting an object without malfunction and with high detection accuracy.

[0013]

The object of the present invention is to provide: (1) a microwave transmitter and a microwave receiver arranged on one side of a moving path of an object to be detected; A microwave reflector is arranged on the other side, and the microwave receiver receives the microwave emitted from the microwave transmitter and reflected by the microwave reflector, and the object to be detected is In the method of detecting the position of the object to be detected or the presence or absence of the object to be detected by blocking the microwave, the microwave transmitter may be configured such that the electric field distribution is either clockwise or counterclockwise. While the rotating wave is emitted toward the microwave reflecting means, the microwave receiver is reflected an even number of times by the microwave reflecting member and emitted from the microwave transmitter. Object detection method by microwave, characterized by receiving a rotating wave rotating in the same direction as the rotating wave,
Or (2) by reflecting microwaves emitted from one side by microwave reflecting means provided on the other side and receiving the reflected wave by the microwave receiver on the other side, whereby both are reflected. Is a method of detecting each other's position and distance, the microwave transmitter converts the electric field distribution to a rotating wave that rotates in any one of clockwise or counterclockwise direction and emits it, Microwave receiver,
The object detection method is achieved by a microwave-based object detection method, comprising receiving a rotating wave that is reflected an even number of times by the microwave reflecting means and rotates in the same direction as a rotating wave emitted from the microwave transmitter. .

In the object detection method using microwaves according to the present invention, a rotating wave which is circularly polarized and rotates clockwise or counterclockwise is reflected by a reflection in a direction opposite to the rotation direction before the reflection. Use inversion. Therefore, the rotating wave emitted from the microwave transmitter is reflected by the reflection means an even number of times and is incident on the microwave receiver, and the microwave receiver is rotated with the rotating wave emitted from the microwave transmitter. By receiving only rotating waves that rotate in the same direction, reflected waves from other than the object to be detected are automatically excluded, and erroneous detection can be eliminated. Also, for example, like a crane facility in a factory, it is mutually determined that one microwave receiver receives microwaves emitted from one microwave transmitter and reflected by the other microwave reflecting member. This is effective in preventing malfunctions even in a configuration in which mutual positional relationships are detected. Further, the microwave transmitter and the microwave receiver can be arranged close to each other, so that the device is downsized and the mounting position is not restricted.

[0015]

[First Embodiment]

FIG. 1 is a configuration diagram showing an embodiment of a microwave object detection method according to the present invention. As shown,
Microwave transmitter 100 and microwave receiver 110
Are arranged to face the reflection means 120. The microwave transmitter 100 includes a microwave oscillator 101 that oscillates a microwave based on a modulation circuit (not shown) and a polarization converter 102, and uses an output from the polarization converter 102 as a microwave 105A as an antenna ( (Not shown). Generally, a microwave is a wave directed in one direction having an electric field distribution (hereinafter, referred to as W100 in the drawing).
It is oscillated from the microwave oscillator 101 as a linear wave). When this linear wave reaches the polarization converter 102, it is converted into a wave (hereinafter, referred to as a rotating wave) in which the electric field distribution rotates clockwise or counterclockwise depending on the inclination direction of the polarization converter 102 (hereinafter, referred to as a rotating wave). And is emitted from the antenna (W101).

As the polarization converter 102, a known device can be used. For example, as shown in FIG.
It is configured by mounting a 0 ° phase difference plate in the waveguide 104.
The thickness of the 90 ° phase difference plate and the length of the waveguide 104 in the axial direction are adjusted to more effectively perform circular polarization. Further, for the same purpose, it is formed in a planar shape narrowed toward the axis of the waveguide 104 or in a planar shape in which a concave portion is partially omitted along the axis of the waveguide 104. Also,
Although not shown, a waveguide 1 is used instead of the 90 ° retardation plate.
A metal blade member of a predetermined length is attached to the inner wall of 04,
Alternatively, the polarization converter 102 can also be configured by attaching a metal lump to the inner wall of the waveguide 104 and making the cross-sectional shape thereof a circular shape with a part of the circumference missing. Further, although not shown, the turn-style branch circuit is connected to the waveguide 104.
To the polarization converter 102. Then, the polarization converter 102 is mounted in the waveguide 104 so as to intersect with a linear wave oscillated from the microwave oscillator 101 at a predetermined angle (for example, 45 °) (E1).

On the other hand, the microwave receiver 110 includes, for example, an antenna (not shown) for receiving the microwave 105A, a polarization converter 111, and a microwave detector 112. Output from
For example, after amplification by a low-frequency amplifier (not shown), waveform shaping and waveform adjustment are performed by a detection circuit and output from an output circuit. The polarization converter 111 has the same configuration as the polarization converter 102 of the microwave transmitter 100. However, the polarization converter 102 of the microwave transmitter 100 and the polarization converter 111 of the microwave receiver 110 have the same polarization action surface (90 ° retarder, metal blade, metal block, etc.) Are arranged so as to intersect with each other at an angle rotated by π / 2 (E2).

The microwave reflecting means 120 has a structure in which microwaves emitted from the microwave transmitter 100 are reflected an even number of times in the microwave reflecting means 120 and then incident on the microwave receiver 110. Any structure can be used. For example, as shown, when the microwave transmitter 100 and the microwave receiver 110 are arranged in parallel, a single plate may be bent at an angle of 90 degrees. Alternatively, two plate members may be opposed to each other at an angle of 90 degrees. Further, it may be a curved surface having a hemispherical surface or a semicircular cross section. When the microwave transmitter 100 and the microwave receiver 110 are not arranged in parallel, the angle of the plate material is set so that the microwave is reflected even number of times before being incident on the microwave receiver 110. And the curvature of the curved surface may be adjusted appropriately.

In such a configuration, the detected object 130
Moves in the direction of the arrow Z, if it is not on the propagation path of the microwave, the microwave 105A emitted from the microwave transmitter 100 goes straight and travels on one side of the microwave reflecting means 120. After being reflected on the reflection surface 120a and further on the other reflection surface 120b, the light enters the microwave receiver 110. That is, the microwave transmitter 100
From the microwave 105A is reflected twice by the microwave reflecting member 120 and is reflected by the microwave receiver 11
0 is received. Here, the microwave 105A is oscillated from the microwave oscillator 101 as a linear wave (W100) directed in one direction with its electric field distribution, and the polarization converter 10A
2 is converted into a rotating wave (W101) having a clockwise or counterclockwise electric field distribution by the microwave transmitter 10
Fired from 0. Next, the microwave reflecting means 120
The electric field distribution is inverted by the first reflection by the reflection surface 120a (W102), and the second reflection by the reflection surface 120b.
Rotational wave (W1) whose electric field distribution has been inverted again by the second reflection
03) and enters the microwave receiver 110. Then, it is converted into a linear wave (W104) by the polarization converter 111 in the microwave receiver 110 and detected by the microwave detector 112. As described above, the microwave 105
A is detected by the even number of reflections (in this case, two times) by the microwave reflecting means 120 while maintaining the electric field direction during oscillation.

At this time, if the voltage application or the generation direction of the microwave oscillator 101 and the microwave detector 112 are made the same, the position of the object 130 or the presence or absence of the object Can be detected, and even if the detected object 130 approaches and the microwave 105A is reflected by its tip, erroneous detection due to interference of the reflected wave 105B can be prevented. That is, even if the detected object 130 moves in the direction of the arrow Z and a part of the microwave 105A is reflected at the tip, the reflected wave 105B is not reflected on the detected object 1
Since the direction of the electric field is inverted by the reflection with 30 (W105), it is not converted into a linear wave by the polarization converter 111 of the microwave receiver 110, but is detected by the microwave detector 112. Never. Similarly, even when the microwave 105A is reflected at the rear end of the detected object 130, erroneous detection due to interference can be prevented.

According to the above configuration, the microwave transmitter 100 and the microwave receiver 110 are connected to the object 1 to be detected.
Since it can be arranged on one side of the 30 transport paths (for example, a conveyor), the wiring of the microwave transmitter 100 and the microwave receiver 110 is excellent in the workability and the size of the apparatus can be reduced.

[Second Embodiment] The object detection method shown in the first embodiment is also effective for mutual detection in the crane equipment 80 described with reference to FIG. That is, the microwave transmitter 100, the microwave receiver 110, and the microwave reflecting means 120 shown in the first embodiment are attached to the self-propelled cranes 82 and 83, respectively. The microwave rotating wave is emitted toward the wave reflecting means 120, and the microwave receiver 110 is configured to detect the rotating wave rotating in the same direction as the rotating wave emitted from the microwave transmitter 100. Accordingly, similarly, a reflected wave from another device or a wall surface can be eliminated, and malfunction can be prevented.

Since the microwave reflecting means 120 is a non-electrical member, it has few failures and does not require much maintenance work. Even if the microwave transmitter or microwave receiver of one crane fails, If the other microwave transmitter or microwave receiver is functioning normally, microwaves can be transmitted to and received from the microwave reflecting means 120 of the failed crane. Can be prevented. Further, by installing the same microwave reflecting means 120 on the wall surface on the extension of the rail 81 and having the same configuration, it is possible to prevent the crane from colliding with the wall surface.

In each of the above embodiments, in order to convert a linear wave into a rotating wave and to restore a rotating wave into a linear wave, the inclination angle of the polarization converter in the waveguide and the microwave oscillator or The direction of the diode of the microwave detector is positioned so as to be an optimum angle (45 ° in the example of FIG. 1; hereinafter, referred to as an optimum conversion angle) for conversion from a linear wave to a rotation wave. However, in reality, due to various external factors, the direction of the diode and the inclination angle of the polarization converter may not be the conversion optimum angle, and accordingly, the mode conversion of the microwave is not performed accurately and the detection accuracy is reduced. There is a case where a problem of lowering occurs. In particular, if the positioning of the microwave oscillator 101 and the polarization converter 102 on the side of the microwave transmitter 100 is not accurate, generation of a rotating wave may be impossible. Therefore, as shown in FIG. 2, a polarization modifier 102a made of a conductive material is inserted between the microwave oscillator 101 and the polarization converter 102 of the microwave transmitter 100. In this case, it is necessary to arrange the polarization modulator 102a and the polarization converter 102 so as to intersect at the same angle θ as the optimal conversion angle. This is for the following reason.

As shown in the figure, even when the linear wave W100a oscillated from the microwave oscillator 101 has an electric field distribution crossing the polarization converter 102 at an angle other than the optimum conversion angle, the linear wave W100a is converted as shown. optimum angle to become component (for convenience, the vertical component W _v and) and the vertical component W _V perpendicular to the component (for convenience, the horizontal component W _H) can be decomposed into. Here, the polarization modifier 102a
And the polarization converter 102 are disposed so as to intersect with each other at an optimum conversion angle, so that the polarization rectifier 102a and the linear wave W1
Take parallel positional relationship with the horizontal component W _H of 00a. At this time, since the microwave cannot propagate in parallel with the conductor, the linear wave W100a is
, The horizontal component W _H cannot propagate through the polarization modulator 102 a, and only the vertical component W _V propagates and the polarization converter 1
Proceed to 02. This vertical component W _V is calculated by the polarization converter 1
Since it has an electric field distribution that intersects with an optimum conversion angle with respect to 02, it corresponds to the linear wave W100 in FIG. 1 and is thus reliably converted into a rotating wave by the polarization converter 102.

Further, on the microwave receiver 110 side, an equivalent polarization rectifier 111a is provided between the microwave detector 112 and the polarization converter 111.
2, the electric field distribution of the linear wave restored by the polarization converter 111 can be matched with the detection direction of the microwave detector 112,
In combination with the microwave transmitter 100 described above, more accurate object detection can be realized. That is, the signal is collected by the microwave receiver 110 and the polarization converter 1
No matter what direction the electric field distribution of the linear wave W105a restored in 11 is directed, when passing through the polarization rectifier 111a, the component in the vertical direction with respect to the polarization rectifier 111a, that is, the microwave detector 112 Only the component (W104) parallel to the detection direction is incident on the microwave detector 112, and reliable detection is performed.

The polarization modifiers 102a and 111a are, as shown, plate-shaped members having a substantially "V" shape with a bent portion at the axis of the waveguide.
In both 2a and 111a, it is preferable in terms of conversion efficiency that the bent portions are arranged so as to face the traveling direction of the microwave. Further, the configuration provided with the polarization modifier can be applied to any of the above embodiments.

[0028]

As described above, in the object detection method using microwaves according to the present invention, a circularly polarized rotating wave that rotates clockwise or counterclockwise is reflected by the object to be detected. In this case, the fact that the rotation direction is reversed in the direction opposite to the rotation direction before the reflection is used. Therefore, the rotating wave emitted from the microwave transmitter is reflected by the reflection means an even number of times and is incident on the microwave receiver, and the microwave receiver is rotated with the rotating wave emitted from the microwave transmitter. By receiving only rotating waves that rotate in the same direction,
The erroneous detection can be eliminated by automatically rejecting reflected waves from objects other than the detected object. Also, for example, like a crane facility in a factory, it is mutually determined that one microwave receiver receives microwaves emitted from one microwave transmitter and reflected by the other microwave reflecting member. This is effective in preventing malfunctions even in a configuration in which mutual positional relationships are detected. Further, the microwave transmitter and the microwave receiver can be arranged close to each other, so that the device is downsized and the mounting position is not restricted.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an object detection method using microwaves according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the polarization rectifier when the polarization rectifier is provided in the object detection method using microwaves according to the present invention.

FIG. 3 is a schematic diagram illustrating a conventional object detection method using microwaves.

FIG. 4 is a graph showing a received power characteristic of a conventional microwave object detection method.

FIG. 5 is a schematic diagram illustrating another example of a conventional microwave object detection method.

FIG. 6 is a schematic diagram showing an example in which the object detection method using microwaves according to the present invention is applied to crane equipment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 Microwave transmitter 101 Microwave oscillator 102 Polarization converter 102a Polarization modifier 110 Microwave receiver 111 Polarization converter 111a Polarization modifier 112 Microwave detector 120 Microwave reflector 130 Object to be detected

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-107696 (JP, A) JP-A-50-120596 (JP, A) JP-A-8-248145 (JP, A) 26000 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01V 3/12 G01S 13/06

Claims (2)

(57) [Claims] 1. A microwave transmitter and a microwave receiver are arranged on one side of a moving path of an object to be detected, microwave reflecting means is arranged on the other side, and microwave transmission is performed. The microwave is received by the microwave receiver, which is emitted from the wave device and reflected by the microwave reflecting means, and the position of the detected object or the position of the detected object is obtained by the detected object blocking the microwave. In the method of detecting the presence or absence of a detected object, the microwave transmitter emits a rotating wave whose electric field distribution rotates in one of clockwise or counterclockwise directions toward the microwave reflecting means. The microwave receiver receives a rotating wave that is reflected by the microwave reflecting member an even number of times and rotates in the same direction as the rotating wave emitted from the microwave transmitter. Object detection method according microwaves characterized. 2. A microwave emitted from one side is reflected by microwave reflecting means provided on the other side, and the reflected wave is mutually received by the microwave receiver by the one side. A method in which both detect each other's position and distance, and the microwave transmitter converts the electric field distribution to a rotating wave that rotates in one of clockwise or counterclockwise directions and emits it, The microwave receiver receives a rotating wave that is reflected by the microwave reflecting means an even number of times and rotates in the same direction as the rotating wave emitted from the microwave transmitter. Object detection method.