JPH0436464Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to an underground position detection device that detects the position of a detected object underground using radio waves on the ground.

"Prior Art" First, an overview of a conventional device of this type will be explained. Figure 4 shows an excavator 3 drilling underground 2 for ground 1.
This figure shows hole 4 being dug almost horizontally. In this example, the object to be detected is the excavator 3, and the excavator 3 is lowered into the underground 2 from the shaft 5.
Dig hole 4 using this as a starting point.

In order to know the position of the excavator 3, a radio wave transmitter 11 is provided on the ground 1, and pulsed radio waves are transmitted from the radio wave transmitter 11 into the underground 2 at regular intervals.
On the other hand, a radio wave receiver 12 is provided in the excavator 3 which is the object to be detected. When the transmitter 11 is located directly above the receiver 12 and in the vicinity 13 thereof, the radio waves from the transmitter 11 are received by the receiver 12. The distance between the transmitter 11 and the receiver 12 is proportional to the time from when the transmitter 11 transmits a radio wave pulse until the receiver 12 receives it, and also proportional to the reception voltage of the receiver 11. Therefore, by moving the position of the transmitter 11 on the ground 1, the position of the receiver 12, that is, the excavator 3 can be detected.

For this purpose, a position detection trolley 21 is provided on the ground. The position detection trolley 21 has wheels 2 on both sides of a thin rectangular body 22, as shown in FIG.
3 and 24 are respectively attached, and the vehicle body 22
A wheel 25 is attached below the front protrusion.
A drive handle 56 for moving the trolley 21 is attached. A triangular dipole-shaped transmitting antenna 26 is housed inside the truck 21 . Although not shown in the figure, a transmitter is also accommodated, and a power supply and signal cable 27 for the transmitter is connected to the vehicle body 22.
It is derived from

A receiver 12 is attached to an excavator 3, which is an object to be detected. For example, as shown in FIG. 6, the receiving antenna 28 of the receiver 12 is constructed by attaching a pair of triangular antenna elements 31a and 31b to the circumferential surface of a cylindrical body 29 made of an insulating material. Although not shown in the figure, a receiver main body is housed inside the cylindrical body 29, and a received signal converted to a low frequency signal is outputted through a cable 32.

Radio wave pulses are radiated into the underground 2 from a transmitter in the position detection trolley 21 and received by the receiver 12 . From the directional characteristics of these two antennas, in order to make their detection relatively easy, if the axis of the cylindrical body 29 of the receiver 12 is set perpendicular to the plane of the drawing as shown in FIG. The ground 1 is moved in a direction perpendicular to the axis of 29. At this time, the directional characteristic curve 34 of the transmitting antenna 26 is wider on the page than the one perpendicular to the page, and similarly, the directional characteristic curve 35 of the antenna 28 of the receiver 12 is also wider on the page than on the page. It is wider than that in the vertical plane, and when selected in this way, it is easier to match the transmitting direction and the receiving direction, that is, the excavator 3
It is easy to detect the position of

However, although it is easy to detect the position of the excavator 3, both the transmitting antenna and the receiving antenna have relatively wide directional characteristics, for example, the half width is about 60 degrees, so
The drawback was that the detection position accuracy of the excavator 3 was poor.

In addition, in ground penetrating radar, the height of the antenna relative to the ground can be changed.
It is proposed in No. 59-101760 (Jikkoi No. 1-41205). Since underground radar has a transmitting antenna and a receiving antenna installed side by side, the radiation impedance of the antenna changes depending on the ground condition.
When a mismatch occurs, a large amount of the transmitted signal enters the receiving antenna, saturating the receiver's front-stage amplifier, and the saturation does not immediately disappear. The height of the antenna is adjusted to avoid this problem.

"Means for Solving Problems" According to this invention, a means is provided that can change the height of one of the antennas of the radio wave transmitter and the radio wave receiver attached to the position detecting trolley relative to the ground.

In both the antenna of a radio wave transmitter and a radio wave receiver, when the height relative to the ground is changed, the directivity characteristics change. Therefore, for example, first the antenna is brought close to the ground in the same manner as before to search for the object to be detected, and once transmission and reception are mutually confirmed, the height of the antenna is raised to sharpen the directional characteristics of the antenna on the ground. In this state, the object to be detected is searched so that the time from transmission to reception is minimized or the received voltage is maximized to improve the detection position accuracy.

As mentioned above, this device differs from the known one shown in the above publication in that it detects a wide range or a narrow range by changing the height of the antenna to change the sharpness of the directional characteristics. The technology is different from ground penetrating radar.

"Embodiment" FIG. 1 shows an embodiment of this invention, which is applied to the transmitting side, and parts corresponding to those in FIG. 5 are given the same reference numerals. In this example, wheels 23-25
can be freely removed from the vehicle body 22, and its mounting position can be changed in the height direction. In Figure 1, the wheels 23 to 25 are located in the bottom bearing hole.
When the vehicle body 22 is installed, bearing holes 41 and 42 are formed above the bearing holes in a vertical arrangement on the side wall of the vehicle body 22, respectively. Therefore, when the wheels 23 to 25 are attached to the bearing hole 41, the antenna 26 approaches the ground, and when the wheels 23 to 25 are attached to the bearing hole 42, the antenna 26 comes closer to the ground and is almost in contact with the ground.

For example, the height from the ground to the antenna 26 is h,
If the wavelength used is λ, the directivity characteristic when h/λ=0 is broad as shown in Figure 2A, but h/λ
= 0.1, it becomes sharp as shown in Figure 2B.
Therefore, for example, as illustrated in FIG. 1, the height h of the antenna 26 is increased one after another, and at each height, the position detection trolley 21 is moved on the ground in a direction perpendicular to the traveling direction of the excavator 3. When the signal voltages of the received signals received by the receiver 12 are measured, the signal voltages are shown as curves 45, 46, and 47 in FIG. 3, for example. When the height h of the antenna 26 is low, as shown by a curve 45, the received voltage does not change much even if the position detection trolley 21 is moved considerably, but when the height h of the antenna 26 is increased, as shown by a curve 47 Reception is possible only when the position detection trolley is located almost directly above the receiver 12. Therefore, the antenna 26
search for the object to be detected, then lower antenna 2.
By increasing the value of 6, the position of the object to be detected can be detected with higher accuracy. Note that it is sufficient that the height of the antenna 26 can be changed in multiple steps within the range of h/λ from 0 to 0.1. Of course, it may be possible to change it continuously.

In addition, in FIG. 1, a transmitter 37 is installed inside the vehicle body 22.
A balun 38 is arranged between the transmitter 37 and the antenna 26. In the above description, any other means can be used to change the height of the antenna 26. Alternatively, the receiver 12 may be placed on the ground 1, and the transmitter 11 may be placed on the object to be detected underground.

"Effects of the invention" As described above, according to this invention, by changing the height of the antenna on the ground side relative to the ground surface, it is possible to easily locate the object to be detected and detect it with high positional accuracy. I can do it. For example, in the past, the detection position accuracy was about 1 m, but with this invention, the detection position accuracy can be reduced to about 1 cm.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of a position detecting cart which is a main part of the underground position detecting device according to this invention, and Fig. 2 shows the orientation when the height of the antenna 26 in Fig. 1 relative to the ground is changed. Diagram showing examples of characteristics, 3rd
The figure shows an example of the received voltage vs. bogie movement distance characteristic with the height of the antenna above the ground as a parameter.
The figure is a sectional view showing an example of an underground position detection device, FIG. 5 is a perspective view showing an example of a position detection trolley, FIG. 6 is a perspective view showing an example of a receiving antenna 28, and FIG. FIG. 3 is a diagram showing the arrangement relationship of receiving antennas.

Claims (1)

[Scope of Claim for Utility Model Registration] One of a radio wave receiver and a radio wave transmitter is attached to a detected object moving underground, and the other of the radio wave receiver or radio wave transmitter is attached to a position detecting cart on the ground. An underground detection device that detects the position of the object to be detected by receiving radio waves transmitted from the radio wave transmitter with the radio wave receiver and measuring the propagation time and/or received voltage of the received radio waves, comprising: As the antenna of the radio wave transmitter or radio wave receiver of the detection trolley, an antenna whose directional characteristic is directed toward the ground is used, and a means is provided for changing the height of the antenna with respect to the ground. An underground position detection device characterized by: