JP2001021663A - Radar device for underground prospecting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device for underground prospecting that can expand a detection range by using a small number of antennas. SOLUTION: The radar device for underground prospecting is installed along with an underground excavator with an excavation blade that is mounted to a tip part while being inclined from an erect state for an excavation direction. Then, the radar device for prospecting the underground is provided with radar antennas 3 and 4 for prospecting the underground that is mounted to one portion of the excavation blade and or the rear portion and transmission parts 2a and 2b for selectively supplying a pulse signal with a different main frequency component to the radar antenna 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground exploration radar device mounted on an underground excavator called a shield machine or the like, and an antenna used for the radar device. The present invention relates to a radar apparatus for underground exploration and an antenna thereof having an improved detection function.

Conventionally, a shield excavation method has been known as a non-cutting method for forming various tunnels in the ground without performing cutting from the ground. The shield excavator used in such a shield excavation method is usually large enough to allow a person to stand and work inside the excavator, and the excavation speed is as low as about 10 cm per minute.

[0003] In such a large excavator, an underground radar device for monitoring an obstacle ahead is installed at the center of a disk-shaped rotary blade for excavation installed at the tip of the excavator. JP-A-8-278371, etc.). In some cases, an underground radar device is installed on the side peripheral surface of a shield excavator for the purpose of monitoring changes in geology (Japanese Patent Publication No. 4-329).
No. 19).

Recently, as a very small shield drilling device,
50m diameter at the tip of a flexible rod called a rod
An excavator with a size of about m to 60 mm is attached, and the rotational force and the propulsion force are transmitted from the driving device installed on the ground to the excavator attached to the tip of the excavator via the rod-shaped body, thereby making the excavator smaller in the ground. A method of forming a tunnel has been adopted. A cutting edge is fixed to the tip of the excavator in a state inclined with respect to the propulsion direction, and the cutting edge is rotated as the excavator rotates. The shield excavation method for forming such an ultra-small diameter tunnel is called a non-cutting drilling method or the like, and is used for forming a tunnel for piping a small-diameter gas pipe.

[0005] The non-cutting drilling method will be described with reference to FIG. First, as shown in FIG. 6A, a driving device R is installed on the ground, a flexible elongated rod Q is connected to the driving device R, and an excavator P is attached to the tip of the rod Q. . An excavation blade is fixed to the tip of the excavator P. The excavator P is made to enter the ground from the shaft, and the rotational force and the propulsive force are transmitted from the driving device R via the rod Q to the excavator P, so that the excavator P has a small diameter of 50 mm to 60 mm between the shaft and the next shaft. Tunnel is formed.

After the formation of the small-diameter tunnel, as shown in FIG. 6B, the excavator P is removed from the tip of the rod Q, and the excavator S having a diameter of about 200 mm is called a back reamer. After the tip of the cable T to be laid is attached, the rod Q is retracted. Along with this, the diameter of the tunnel is enlarged by the back reamer, and a cable is laid in the tunnel with the increased diameter.

In the above-mentioned conventional non-cutting drilling method, prior to the formation of a tunnel, the burial condition of existing facilities such as gas pipes, water pipes, and power cables existing in the ground to be formed is determined on the ground by an underground radar apparatus. Explored by manipulating Underground radar devices operated on the ground like this
It is disclosed in Japanese Utility Model Publication No. 3-55122. Then, a route for forming a tunnel that can avoid contact with the existing buried object is determined.

However, in practice, due to the above-mentioned underground radar device for ground operation, the position detection error of the existing underground buried equipment, the control error concerning the route selection at the time of tunnel formation, etc. It often happens that the tunnel collides with or gets too close to the buried object, requiring a re-creation of the tunnel. Particularly problematic is that, as illustrated in FIG.
6A does not hinder the formation of a small-diameter tunnel, but hinders the formation of a large-diameter tunnel using a back reamer, as illustrated in FIG. 6B. This is because, in such a case, all the operations need to be started again from the formation of the first small-diameter tunnel, and the labor and time spent on the operations up to that point are wasted.

In the above-mentioned non-cutting drilling method, since the size of the excavator is significantly smaller than that of the conventional shield excavator, it is necessary to mount an antenna for an underground radar device on the excavator.
First, the size needs to be significantly reduced. Further, a second problem that occurs when the antenna for the underground radar device is mounted on the excavator using the non-drilling method is that the excavator used in the non-drilling method uses the excavator P as shown in FIG. The point is that the elongated rectangular plate-shaped excavation blade BL attached to the tip is attached in a state where the excavator P is inclined from an upright state with respect to the rotation axis Z of the excavator P.

That is, by attaching the transmitting antenna TX and the receiving antenna RX to the back side of the excavation blade BL,
It is possible to detect an underground obstacle with respect to a portion inside the radiation pattern of the transmission antenna indicated by a substantially solid line. It can be considered that the reflected wave caused by an obstacle propagates at least considerably behind, if not isotropically, over an open angular range, and the range where the transmission power can reach is detectable. This is because it can be approximated.
In other words, as long as a transmitted wave arrives and a reflected wave is generated, it can be approximated that all such reflected waves can be detected by a receiving antenna having a limited reception sensitivity pattern.

The detectable area faces upward in the position illustrated in FIG. 7A, and faces downward in the position illustrated in FIG. . That is, the detectable area surrounded by the solid line advances while spirally rotating with the rotation and advance of the excavator P. As a result, in the position of FIG. 7A, the lower part of the tip cannot be detected, and conversely, in the position of FIG. 7B, the upper part of the tip cannot be detected. Blind spots for detection occur on the upper, lower, left and right sides of the portion.

In order to reduce the blind spot of the detection of the straight ahead, as shown in FIG. 7 (C), the mounting surface of the transmitting antenna TX and the receiving antenna RX is made orthogonal to the rotation axis Z of the excavator P. Good. However, if you do so,
The antennas TX and RX recede considerably from the tip portion, and the radio wave spreads considerably at the position of the excavation blade BL so that it does not reach the front. In addition, there is a problem that the size of the dielectric window which must be provided on the metallic excavation blade BL for transmitting radio waves becomes large, and the mechanical strength of the excavation blade BL becomes lower than a required value.

Further, since a considerable part of the radio wave is radiated into the tip of the excavator P, the inner wall must be covered with a radio wave absorber. Therefore, the transmitting antenna T
The mounting surface of X and the receiving antenna RX cannot be tilted beyond a certain limit, for example, a limit illustrated in FIG. 7D, and a blind spot still remains.

The occurrence of this blind spot is caused by the fact that the excavating speed of this type of uncut drilling excavator is as large as 30 cm per second, which is different from about 10 cm per minute of the conventional shield excavator. I have. That is, focusing on the spiral motion performed by the radio wave beam directed upward and downward of the rotation axis, the pitch of the turning motion is small and the blind spot is small in the conventional shield excavator. On the other hand, in the excavator of the non-cutting drilling method, the pitch of the beam turning motion is large, and the blind spot is increased accordingly.

Further, as shown in FIGS. 7 (A) and 7 (B), when the antenna is mounted on the inclined cutting blade, a blind spot can be formed straight ahead. For this reason, there is also a problem that the excavator exists straight ahead and may collide with an obstacle that has been missed by the underground radar.

Japanese Patent Application No. 10-31 relating to the earlier application of the present applicant
No. 4,151, in order to eliminate the blind spots in the lateral detection described above, a plurality of directional antennas are attached at substantially equal intervals also around the side surface near the tip of the underground excavator. An underground radar device capable of detecting the entire periphery of the tip portion of the underground radar is disclosed.

[0017]

The underground radar apparatus of the prior application has a great advantage in that the blind spot for detecting the upper, lower, left and right sides of the excavator can be greatly reduced. However, it is necessary to install a plurality of antennas around the side surface of the tip of the underground excavator, which causes a problem that the cost increases. Also, this method is not effective in enlarging the field of view straight ahead. Accordingly, it is an object of the present invention to provide an economical underground exploration radar apparatus that uses a minimum number of antennas to reduce blind spots in detection including the straight ahead.

[0018]

An underground survey radar apparatus according to the present invention which solves the above-mentioned prior art has an underground excavator having an excavation blade which is attached to a tip portion in a state of being inclined from an upright state in a digging direction. It is installed along with. And this underground exploration radar device is an underground exploration radar antenna attached to or behind a part of the excavation blade,
A transmission unit for selectively supplying a pulse signal having a different main frequency component to the underground exploration radar antenna.

[0019]

According to a preferred embodiment of the present invention, the above-mentioned radar antenna for underground exploration comprises a dipole antenna of a plane type or the like.

According to another preferred embodiment of the present invention,
One of the main frequency components of the pulse signal is set so that the 1.5 wavelength of the center frequency is substantially equal to the entire length of the dipole antenna, so that the antenna is inclined 45 ° from the front direction of the antenna. It is configured to radiate radio waves in different directions.

According to still another preferred embodiment of the present invention, one of the main frequency components of the pulse signal has a value such that a half wavelength or one wavelength of the center frequency is substantially equal to the entire length of the dipole antenna. Is set.

According to still another preferred embodiment of the present invention, there is provided a reception signal separating means for separating the reception signal of the radar antenna for underground exploration based on the relationship between the level and the rotation angle of the excavator. Can be

[0023]

FIG. 1 is a block diagram showing the configuration of a radar apparatus for underground exploration according to an embodiment of the present invention, wherein 1 is a control processing section, 2a and 2b are transmitting sections, 3 is a transmitting antenna, and 4 is a transmitting antenna. Receiving antenna, 5 a receiving unit, 6 a synchronization signal generating unit, 7
Reference numerals a and 7b denote switches, 8 denotes a rotation angle detection unit, 9 denotes a screen display unit, and 10 denotes a key input unit.

As shown in the sectional view of FIG. 3, an excavating blade BL is attached to the tip of a cylindrical structure P of the excavator so as to be inclined with respect to the central axis of the structure P. The transmitting antenna 3 and the receiving antenna 4 are mounted adjacent to each other at the center of the excavation blade BL. Each of the transmitting antenna 3 and the receiving antenna 4 is composed of a planar dipole antenna. These dipole antennas are shown in FIG.
As shown in the plan view of FIG. 3, the power supply points are formed of two triangular metal plates or metal foils formed on a dielectric substrate with their vertices facing each other.

Radio waves radiated behind the planar dipole antenna are absorbed by a radio wave absorbing material such as ferrite provided on the back surface of the dielectric substrate, and only radio waves radiated forward are radiated into the ground. For further details on the construction and operation of this type of dipole antenna for subsurface radar, see
If necessary, refer to the patent application filed earlier by the present applicant (for example, Japanese Patent Application Laid-Open No. 10-20030).

When activated by a command from the control processing unit 1, the transmission units 2a and 2b include different main frequency components in synchronization with the synchronization signal supplied from the synchronization signal generation unit 6 via the switch 7a. Generates a pulse signal (baseband pulse signal). The pulse signal generated by the transmitting unit 2a has a waveform such that, when the center value of the main frequency component is converted into the wavelength λ, half the wavelength, that is, half the wavelength λ / 2, is equal to the total length 2h of the dipole antenna 3. .

As shown in FIG. 8, (λ / 2) / (2c)
(Where c is the propagation speed of an electromagnetic wave in a vacuum), a pulse P having a width of:
This is shown by a curve S. By passing this pulse P through a filtering circuit having a filtering characteristic shown by a curve F, when the center value of the main frequency component is converted into a wavelength λ, a half wavelength λ / 2
Can generate a pulse having a waveform that is equal to the total length 2h of the dipole antenna 3.

Similarly, when the center value of the main frequency component of the pulse signal generated by the transmitting section 2b is converted into the wavelength λ, 1.5 times, that is, 3λ / 2 becomes equal to the total length 2h of the dipole antenna 3. It has such a waveform. As shown in FIG. 9, (3λ / 2) / (2c) (where c
When a pulse P having a width of (the propagation speed of an electromagnetic wave in a vacuum) is generated, its frequency spectrum is represented by a curve S. By passing this pulse P through a filtering circuit having a filtering characteristic shown by a curve F, when the center value of the main frequency component is converted into a wavelength λ, 1.5 wavelengths (3λ / 2) are equal to the total length 2h of the dipole antenna 3. A pulse having such a waveform can be generated.

That is, the center frequency of the pulse signal generated by the transmitting unit 2a is set so that its half-wavelength conversion value is equal to the total length (2h) of the dipole antenna, and the center frequency of the pulse signal generated by the transmitting unit 2b is set. Is 1.5
The wavelength conversion value is set so as to be substantially equal to the total length (2h) of the dipole antenna.

Here, the wavelength of the radio wave radiated from the dipole antenna is not the wavelength in vacuum or in the air, but the wavelength in the ground where the radio wave is radiated. In general, since the dielectric constant of the soil is greater than 1 in the ground, the wavelength of the radio wave is shorter than the value in the air. The dielectric constant of soil changes depending on the components of the soil, the water content, and the like. Therefore, the length of the dipole antenna may be set in consideration of the dielectric constant of the soil at the tunnel forming point which has been investigated in advance, or the average wavelength calculated based on the average dielectric constant of various soils may be determined. The length of the dipole antenna may be set in consideration of this.

The control processing unit 1 operates the switch 7a to supply the synchronization signal generated by the synchronization signal generation unit 6 to one of the activated transmission units 2a and 2b, and operates the switch 7b. Then, the pulse signal generated by the active transmitting unit is supplied to the transmitting antenna 3.

A beam B0 indicated by a solid line in FIG. 3 is a case where a pulse signal having a relation that the half-wavelength converted value of the center value of the main frequency component is substantially equal to the total length (2h) of the dipole antenna is radiated from the transmitting antenna 3. 3 shows a radiation beam pattern (antenna gain curve). The loop indicated by a dotted line for the receiving antenna 4 is a receiving sensitivity (antenna gain curve) having the same shape as the pattern of the radiation beam from the transmitting antenna.

The method of radiating a pulse signal having a main frequency component in which the half-wavelength converted value of the center frequency shown in FIG. 3 is substantially equal to the entire length of the dipole antenna has been conventionally used.
This method has been used in underground radar. This technique is
Although the antenna gain is reduced as compared with the case of radiating a pulse signal composed of frequency components in which the one-wavelength conversion value of the center frequency becomes substantially equal to the entire length of the dipole antenna (λ = 2h), the distance between the antenna and the feed line is reduced. There is an advantage that impedance matching is easy to perform, and in consideration of this advantage, it has been widely adopted in conventional underground radars.

On the other hand, three beams Bc, B _L , and B _R shown by solid lines in FIG. FIG. 11 shows a radiation beam pattern when a pulse signal having a frequency component having a relationship that is substantially equal to (2h) is emitted. The loop indicated by the dotted line for the receiving antenna 4 is the receiving sensitivity having the same shape as the pattern of the radiation beam from the transmitting antenna.

As discussed above with respect to FIG. 7, it can be considered that the reflected wave caused by the obstacle propagates over a large, if not isotropic, range of angles that are open backwards. Therefore, it can be approximated that the range in which the transmission power reaches reaches the detectable range. In other words, as long as a transmitted radio wave arrives and a reflected wave is generated, it can be approximated that all such reflected waves can be detected by a receiving antenna having a spatially limited receiving sensitivity pattern.

In the example of FIG. 4, the beam Bc at the center is directed obliquely upward, the beam B _{R at} the right of the center is directed almost directly above,
The beam B _L on the left side of the center is almost forward. The center beam Bc and the right beam B _{R form} an angle of 360 ° with the up, down, left and right directions when the excavator blade BL and the transmitting / receiving antennas 3 and 4 rotate around the central axis of the excavator P with the rotation of the excavator P. Turn around a range. On the other hand, even if the transmitting / receiving antennas 3 and 4 rotate around the central axis of the excavator P with the rotation of the excavator P, the left beam B _L facing substantially in the forward direction does not change its direction much. Do not change.

As a result, the receiving unit 5
The received level of the reflected wave received by the excavator is composed of a component that fluctuates greatly with the rotation of the excavator and a component that does not fluctuate much. The control processing unit 1 shown in FIG. 1 receives the reception signal from the reception unit 5 and receives the rotation angle of the excavator P detected by the rotation angle detection unit 8 from the detection unit, and determines the relationship between the level of the reception signal and the rotation angle. , The received signal is separated into a plurality of components.

For example, it is assumed that the level of the received signal R and the rotation angle θ of the excavator P have a relationship shown by a solid line in FIG. In this case, the received signal R includes a component Ra having a substantially constant level independent of the rotation angle θ of the excavator and a specific rotation angle θo corresponding to a position directly above the tip.
Is separated into a unimodal component Rb having a large level only in the vicinity of. The component Ra is recognized as a component of a reflected wave from a reflective object existing straight ahead of the excavator P, and the component Rb is a component of a reflected wave from a reflective object existing directly above a tip portion of the excavator P. Be recognized.

If necessary, the control processing unit 1 transmits the data to the transmitting unit 2b.
By operating the transmission unit 2a instead of the above, the transmission beam having the pattern as shown in FIG. 3 is transmitted into the ground, and the reflected wave from the ground is received. In this mode,
A search focusing on obstacles existing diagonally forward is performed.

The control processing section 1 creates display data such as a PPI display screen in accordance with a command from the key input section 10 in parallel with the above various controls and processes, and causes the display device 9 to display the data.

As described above, in consideration of the easiness of impedance matching, a transmitting unit for transmitting a pulse signal having a frequency component such that the half-wavelength converted value of the center frequency becomes substantially equal to the total length (2h) of the dipole antenna is provided. The configuration has been exemplified. However, instead of or in addition to such a transmission unit, a pulse signal having a frequency component such that the wavelength conversion value of the center frequency becomes substantially equal to the total length (2h) of the dipole antenna is transmitted. A configuration in which a transmission unit is provided may be employed.

Further, the configuration has been exemplified in which a plurality of transmission units for transmitting a plurality of pulse signals having different main frequency components are individually provided. However, it is also possible to provide a single transmitting unit and generate a plurality of pulse signals having different frequency components from this single transmitting unit.

Further, a configuration in which a plurality of transmission units for transmitting a plurality of pulse signals having different frequency components are provided has been exemplified. However, it is also possible to adopt a configuration in which a transmission unit that transmits only a pulse signal of an optimal frequency component is installed such that the 1.5-wavelength conversion value becomes substantially equal to the entire length of the dipole antenna.

Further, the configuration in which the transmitting antenna and the receiving antenna are mounted on the central portion of the excavating blade has been exemplified. However, as illustrated in (C) and (D) of FIG. 7, a configuration in which the transmitting antenna and the receiving antenna are installed at an angle closer to the vertical than the mounting angle of the digging blade behind the digging blade may be adopted. .

Also, the configuration in which the transmission-only antenna and the reception-only antenna are separately installed has been described as an example. However, a single antenna shared for transmission and reception is installed, and the transmission and reception shared antenna used after switching for reception after transmission is used. It can also be an antenna.

Further, the present invention has been described by taking a dipole antenna as an example. However, in general, the radiation pattern of an antenna changes according to the relationship between its size and the wavelength of a transmission pulse signal. Therefore, the present invention can be applied to an underground radar device using another type of antenna such as a slit antenna.

[0047]

As described in detail above, the underground radar apparatus of the present invention has an underground antenna attached to a part of or behind the excavating blade, and a pulse of a different frequency component is attached to the underground antenna. Since the signal is selectively supplied, the radiation pattern of the antenna and the pattern of the receiving sensitivity can be changed according to the point of interest, and the blind spot can be reduced without increasing the number of antennas.

When the frequency of the pulse signal, that is, its wavelength λ is fixed, the wavelength conversion value of the pulse signal, which is almost equal to the total length 2h of the dipole antenna, is 0.5 λ.
And λ, 1.5 λ, the total length of the dipole antenna 2h is shortened, and the transmitting and receiving antennas are also reduced in size.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of an underground survey radar apparatus of the present invention.

FIG. 2 is a plan view showing a configuration of a two-dimensional dipole antenna forming a transmitting antenna and a receiving antenna of FIG. 1;

FIG. 3 is a conceptual diagram illustrating a pattern of a transmission beam and a reception sensitivity of a transmission / reception antenna in the underground search radar apparatus of the embodiment.

FIG. 4 is a conceptual diagram exemplifying a pattern of a transmission beam and a reception sensitivity of a transmission / reception antenna in the underground search radar apparatus of the embodiment.

FIG. 5 is a conceptual diagram showing an example of a received signal level and a rotation angle in the underground survey radar apparatus of the embodiment.

FIG. 6 is a diagram illustrating an operation of an excavator of a non-cutting drilling method using the underground survey radar apparatus of the present invention.

FIG. 7 is a diagram for explaining a problem related to an antenna of a radar device for underground exploration installed in association with an excavator using a non-cutting drilling method.

FIG. 8 is a conceptual diagram for explaining a transmission pulse waveform and a frequency component generated by a transmission unit 2a in FIG.

FIG. 9 is a conceptual diagram for explaining a transmission pulse waveform and a frequency component generated by a transmission unit 2b of FIG. 1;

[Explanation of symbols]

1 Control processing unit 2a Transmitter that transmits a burst signal whose half-wavelength is almost equal to the total length of the dipole antenna 2b 1.5 Transmitter that transmits a burst signal whose half-wavelength is almost equal to the total length of the dipole antenna 3 Transmitting antenna 4 Receiving antenna 5 Receiving unit 8 rotation angle detector P excavator BL digging edge _{B o, B L, B C} , transmission beam pattern B _R transmit antennas

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01Q 17/00 H01Q 17/00

Claims (9)

[Claims] 1. An underground exploration radar installed in association with an underground excavator having an excavation blade attached to a tip portion in a state of being inclined from an upright state with respect to the excavation direction, wherein: An underground exploration radar antenna, which is mounted on the rear side, and a transmission unit that selectively supplies a pulse signal having a different main frequency component to the underground exploration radar antenna. Radar equipment. 2. The underground survey radar apparatus according to claim 1, wherein the underground survey radar antenna comprises a dipole antenna. 3. The radar apparatus according to claim 2, wherein said dipole antenna is a planar dipole antenna. 4. A method according to claim 1, wherein one of the main frequency components of the pulse signal has a value such that 1.5 wavelengths of the center frequency are set to be substantially equal to the total length of the dipole antenna. Characteristic underground exploration radar equipment. 5. The ground according to claim 4, wherein another one of the main frequency components of the pulse signal is set such that a half wavelength of a center frequency is substantially equal to the total length of the dipole antenna. Medium exploration radar device. 6. The underground circuit according to claim 5, wherein another one of the main frequency components of the pulse signal has one wavelength of a center frequency set to a value corresponding to the entire length of the dipole antenna. Exploration radar equipment. 7. The apparatus according to claim 1, further comprising a received signal separating unit for separating a received signal of the underground exploration antenna based on a relationship between a level of the signal and a rotation angle of the excavator. Characteristic underground exploration radar equipment. 8. An underground exploration radar installed in association with an underground excavator equipped with an excavation blade attached to a tip portion in a state inclined from an upright state with respect to the excavation direction, wherein a part of the excavation blade or A radar antenna for underground exploration comprising a dipole antenna mounted on the rear side thereof, and a transmission for supplying a pulse signal having a main frequency component whose 1.5 wavelength is substantially equal to the entire length of the dipole antenna to the underground exploration radar antenna. And a subsurface radar. 9. The underground exploration apparatus according to claim 8, further comprising: a receiving signal separating unit that separates a receiving signal of the underground antenna based on a relationship between a level of the signal and a rotation angle of the excavator. Radar equipment.