JPH03260282A - Underground excavator position detection device - Google Patents

Abstract

PURPOSE:To make it possible to detect a deflection quantity with high degree of accuracy by moving forward either magnetic field generators or magnetic field detectors to bring them near each other, and performing the operation of a relative position of them based on the forward distance and magnetic field detection signals. CONSTITUTION:Magnetic field generators 14a - 14c consisting of a plurality of rectangular loops arranged in parallel are provided on one of either the tip of underground excavators 10 and 20 or the forward standard position. A plurality of loops are successively changed over to provide an excited controller 50, and magnetic field detectors 26a - 26c detecting the magnetic field are provided on the other. Either the magnetic field generators 14a - 14c or the magnetic field detectors 26a - 26c are advanced by a propeller to bring near each other. After that, the operation of a relative position of them is performed by a position operator 30 based on the forward distance of the propeller and detection signals of the magnetic field detectors 26a - 26c, and a deflection quantity of the underground excavators 10 and 20 is detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position detection device for detecting the position of an underground excavator that is excavating underground, and particularly relates to a position detection device for detecting the position of an underground excavator that is excavating underground.
The present invention relates to an underground excavator position detection device suitable for connecting two underground excavators underground.

[Conventional technology]

When constructing a tunnel on the ocean floor, it is not possible to install multiple vertical shafts for launching underground excavators.

However, excavating a long distance with one underground excavator not only makes it difficult to discharge the excavated soil, but also involves many dangers. For this reason, when constructing an undersea tunnel, in order to shorten the excavation distance of the underground excavators, two underground excavators are launched facing each other, and the tunnels excavated by each underground excavator are moved underground. Joining is performed in

However, at the joint point, the centers of both underground digging side machines are on the left and right,
If there is a vertical shift, the connected tunnel will become discontinuous, so it is necessary to find the relative positions of both underground excavators and correct the positional shift. Conventionally, when correcting the positional deviation between two underground excavators, both of them are corrected by detecting the positional deviation of each underground excavator with respect to the tunnel planning line and the position from a reference position such as the starting point. The relative positional deviation between the underground excavation fronts was determined and corrections were made based on this positional deviation.

Conventionally, the following methods have been used to locate underground excavators underground.

■ Determine the position of the underground excavator from the reference point and the deviation from the planned line by underground surveying using Transshift, etc.

■ An optical transmitter that generates coherent light such as a laser beam is installed in the starting shaft of the underground excavator, and this device illuminates the tunnel planning line and illuminates the light spot on the target attached to the underground excavator. Read and determine the position, deviation, and declination of the underground excavator from the starting shaft.

■ Combining an azimuth gyro, pressure type subsidence gauge, inclinometer, and mileage needle based on the segment length assembled in the tunnel, the relative position from the reference position is determined.

However, each of the conventional methods for determining the position of the underground excavator described above has the following drawbacks, making it difficult to accurately perform underground joints.

Method ■ is impractical because it requires taking many measurement points when excavating a tunnel with a bend, making it impossible to measure in real time. If the laser beam from the starting shaft cannot be irradiated to the target, the optical transmitter must be moved to an appropriate position.Furthermore, the optical transmitter cannot directly irradiate the entire length of the planned line. Each time the underground excavator is moved, the mutual positional relationship between the target, the optical surveying device, and the tunnel planning line is actually measured, and the planned route is calculated based on the measurement results, and then the position, deviation, and There is a problem in that the declination angle must be calculated, which requires manpower to relocate, measure, and calculate the optical transmitter, reducing the efficiency of excavation work.

Furthermore, method (■) causes cumulative errors and is not suitable for long-distance excavation, and is also not suitable for excavating curves with a small radius of curvature or excavating tunnels with continuous curves. It is also unsuitable.

In addition, when measuring the relative positions of two underground excavators, as in the case of underground joints, the error further increases.

Therefore, the applicant installed a magnetic field generator on one of the two underground excavators to be connected underground, and installed a magnetic field detector on the other underground excavator to detect the magnetic field generated by the magnetic field generator. , a position detection device is provided in which a magnetic field detector is brought close to a magnetic field generator by a polling device, and the detection signal of the magnetic field detector and the excavation amount of the polling device are inputted to the excavation device to determine the relative position of the two. (Patent Application No. 1-223035).

[Problem to be solved by the invention]

However, the digit 1 detection device shown in the above-mentioned Japanese Patent Application No. 1-223035 uses a rectangular loop cable as a magnetic field generator, resulting in a large detection error. In other words, since the position detection device of Japanese Patent Application No. 1-223035 utilizes the technology of detecting the magnetic field generated by an infinitely long parallel cable, it does not require any other magnetic field to detect the strength of the magnetic field. The magnetic field generated from the pair of sides is also detected by the magnetic field detector, creating an error.

In other words, if the magnetic field ordering device can be regarded as a parallel cable of infinite length, for example, if it is a rectangular loop with a ratio b/a of the long side to the short side a of 100, then the center between the long sides Comparing the offset position X' in the direction perpendicular to the long side from the measured value X with the offset position X' determined based on the strength of the magnetic field detected by the magnetic field detector, the slope is 1 as shown in Figure 9. Therefore, the deviation amount χ' obtained from the detected magnetic field has a value equal to the actually measured value X.

However, when b/a is made small, the strength of the magnetic field detected by the magnetic field detector is affected by the magnetic field generated by the short side a, and the horizontal axis is the measured value X, and the vertical axis is based on the detected magnetic field strength. The slope when taking the eccentric position X' obtained by
This results in a detection error.

Therefore, it is conceivable to configure the magnetic field generator with a plurality of rectangular loops having a large ratio of long sides to short sides. but,
In this case, if a plurality of loops are simultaneously driven to generate a magnetic field, it is impossible to distinguish which loop is responsible for the strength of the magnetic field detected by the magnetic field detector.

The present invention makes it possible to know which loop is generating a magnetic field in a magnetic field generator consisting of a plurality of loops, thereby improving the accuracy of the position of an underground excavator determined based on the detection signal of the magnetic field detector. The purpose of the present invention is to provide a position detection device for an underground excavator that can detect the position of an underground excavator.

[Means to solve the problem]

In order to achieve the above object, the underground excavator position detection device according to the present invention is provided either at the tip of the underground excavator or at a reference position in front of the underground excavator. Control in which the magnetic field generator is composed of a plurality of rectangular loops arranged in parallel, each of the adjacent loops is arranged one on top of the other, and the plurality of loops are sequentially switched and excited to generate a magnetic field. a device, a magnetic field detector provided at either the tip of the underground excavator or the reference position and detecting the magnetic field generated by each of the loops; and a combination of the magnetic field detector and the magnetic field generator. A propulsion device that moves at least one of them forward to bring them closer together, and calculates the relative position of the underground excavator with respect to the reference position based on the forward distance of this propulsion device and the detection signal of the magnetic field detector. It is characterized by having a position calculator.

[Effect]

The present invention configured as described above advances at least one of a magnetic field generator and a magnetic field detector by a propulsion device,
A magnetic field generator and a magnetic field detector are placed close to each other. Then, a plurality of loops constituting the magnetic field generator are sequentially switched and excited while the two are brought close to each other, and the strength of the magnetic field generated by these loops is detected by a magnetic field detector. The strength of the magnetic field detected by this magnetic field detector is input to the position calculator together with the forward distance of the propulsion device.

The position calculator calculates the distance between the underground excavator and the reference position from the distance traveled by the propulsion machine. In addition, the position calculator detects the loop generating the magnetic field that provides the highest level detection signal from the detection signal of the magnetic field detector, calculates the relative position of the magnetic field detector with respect to this loop, and calculates the relative position of the magnetic field detector to this loop. The reference position of the machine! Calculates and outputs vertical and horizontal deviations.

Therefore, the distance to the reference position of the underground excavator and the center shift of the underground excavator with respect to the reference position can be easily determined, and the relative position of the underground excavator with respect to the reference position can be obtained.

Furthermore, the magnetic field generator consists of a plurality of rectangular loops arranged in parallel, with adjacent loops overlapping each other, and each loop being sequentially switched by a control device to generate a magnetic field. Therefore, the loop generating the magnetic field can be easily identified, and by increasing the ratio of the long side to the short side of the loop, the magnetic field detector detects the strength of the magnetic field generated on the long side. The detection signal can ignore the influence of the magnetic field generated by the short side, and has the same effect as detecting the strength of the magnetic field generated from an infinitely long parallel conductor, increasing the accuracy of position detection. be able to. And even if we reduce the distance between the long sides of each loop and increase the ratio of the long side to the short side,
By appropriately selecting the number of loops, the magnetic field detector will not come off the magnetic field generator, and a decrease in detection accuracy can be prevented.

〔Example〕

A preferred embodiment of the position detection device for an underground excavator according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of a position detection device for an underground excavator according to an embodiment of the present invention.

In FIG. 1, an underground excavator 10.20 has a cutter drum 12.22 with a cutter not shown. This cutter drum 12.22 is rotatable and
It can be stopped at any rotational position. In addition, the underground excavator 10.20 has a cutter drum 12.
．． By moving forward while rotating the cutter, the earth and sand excavated by the cutter is taken into the Casitadora L12.22 and transported rearward by a screw conveyor or the like. And these underground excavators10.
The tunnels 20 are excavated from different starting shafts in directions approaching each other along the tunnel planning line, and the excavated tunnels are joined together.

The front part of one of the underground excavators 20 is provided with small-diameter poling devices 24a, 24b, and 24c of compaction type. These boring devices 24a, 24b, and 24c have magnetic field detectors 26a, 26b, and 26c, the details of which will be described later, inside, and serve as propulsion devices that move the magnetic field detectors 26a, 26b, and 26c forward and backward.

Each boring device 24a, 24b, 24c is provided on the rear side of the cutter drum 22 of the underground excavator 20, and is spaced at 90 degree intervals on a circumference with a radius r relative to the center (origin) of the underground excavator 20. It is located. In other words, the X-axis is in the direction of excavation passing through the center of underground excavation [120], the Z-axis is in the vertical direction, and the X-axis and Z-axis are
If the Y-axis is taken in the direction perpendicular to the axis, each boring device 24a, 24b, 24c
, O), (Ol-r, 0).

The cutter drum 22 includes a boring device 24a,
Through holes (not shown) are provided corresponding to the boring devices 24b and 24c, and when the cutter drum 22 stops at the standard position, the through holes are located in front of the boring devices 24a, 24b and 24c. Therefore, the boring devices 24a, 24b, 2
4c digs forward from the through hole when the cutter drum 22 stops at the standard position, and detects the magnetic field detectors 26a and 26b.
, 26c can be advanced toward the other underground excavation @10.

On the other hand, the other underground excavator 10 is a reference position with respect to the underground excavator 20, and has a magnetic field generator 14a, which will be described in detail later, on the front side of the cutter drum 12 or inside the cutter drum 12. , 14b, and 14C are provided. These magnetic field generators 14a, 14b, 14C are installed in the underground excavator 20.
are provided corresponding to the boring machines 24a, 24b, and 24c of The centers of the bowls 26a, 26b, 26c are aligned with the centers of the boring devices 24a, 24b, 24c.

Each magnetic field generator 14a, 14b, 14c has a control bag W50
It is connected to a power supply device 19 controlled by the power supply device 19, and receives power from the power supply device 19 to generate a magnetic field. And each magnetic field generator 14a, 14b, 14c,
They have the same structure, and as shown in FIG. 2 by taking the magnetic field generator 14a as an example, a pair of loop parts 16a, 16
It has a structure in which the points b are arranged perpendicularly to each other.

Each loop portion 16a, 16b is, as shown in FIG.
Plural, for example, five rectangular loop cables 18a
~18e. Each loop cable 18a-1
8e are arranged in parallel along the long sides, each adjacent loop cable overlaps each other by half, and each is connected to AC power supplies 19a to 18e constituting the power supply device 19. , so that it can independently generate a magnetic field.

Each of these AC power supplies 19a to 18e is connected to a control device 50, and the Ha device 50 switches control signals to AC@
, to sources 19a to 18e, and AC power fi19a to 18e.
The corresponding loop cables 18a to 18e are sequentially switched and driven. The loop cables 183 to 18e constituting the loop portion 16a have long sides connected to the underground excavation 1.
The loop part 1 is arranged parallel to the Z axis of 110.
The loop cables 18a to 18e configuring 6b are as follows:
It is arranged so that the long side is parallel to the Y axis of the underground excavator 10.

The magnetic field detector 26a that detects the magnetic field generated by the magnetic field generator 14a has the same structure as the magnetic field detectors 26b and 26c, and includes a Y-axis direction detection section 28a and a two-axis direction detection section 28.
b, each consisting of a pair of detection coils arranged orthogonally. Then, the direction detection unit 28a at Y*,
The strength of the magnetic field generated by the loop portion 16a is detected and a detection signal is sent to the position calculator 30 (see FIG. 1). Similarly, the Z-axis direction detection section 28b detects the strength of the magnetic field generated by the loop section 16b, and inputs a detection signal to the position calculator 30.

The position calculator 30 includes each magnetic field detector 26a, 26b, 26
c detection signal and each polling device 24a, 24b, 2
From the amount of excavation of 4c, the underground excavator 10 of the underground excavator 20
The relative distance to, the Y-axis direction, the amount of deviation in the Y-axis direction, the pitching angle and rolling angle with respect to the axis (X-axis) of the underground excavator 10 are calculated and output to the display device 32 for display.

Underground excavator 1O120 according to the embodiment configured as described above
The relative position between them is determined as follows.

First, cutter drum 12.22 of underground excavator 10.20
Next, drive the polling devices 24a, 24b, 24c installed in the underground excavation $120,
The tip of each underground excavation #1]0 is used as a reference position.
, 26c are placed close to the magnetic field generators 14a, 14b, 14c, and the fact that the tip of each polling device 24a, 24b, 24c reaches the front of the underground excavator 10 is detected based on the magnitude of digging resistance, etc. Each polling device 24a,
The excavation distances 24b and 24c are input to the position calculator 30.

The magnetic field detectors 26a, 26b, 26c are the magnetic field generator 14a
, 14b, 14c, the control device 5
0 sends a control signal to the power supply bag 219 to sequentially switch on each AC power source 19a to 18e, and each magnetic field generator 1
The loop cables 18a to 18e of the loop portion 16a or loop portion 16b of 4a, 14b, and 14C are sequentially switched and driven to generate a magnetic field.

The method of sequentially switching and driving the loop cables 18a to 18e, that is, the pattern of the switching control signal that the control device 50 gives to the power supply device 19, is arbitrary. For example, as shown in FIG. You can switch it to turn it on for just one hour. Further, as shown in FIG. 5, the drive signal is output every ΔT, and the drive signal is continuously applied to the first AC power source 19a twice, and the other AC power source 19a is outputted twice. It is also possible to apply a drive signal to A once at a time so that the first loop cable 18a can be distinguished. Furthermore, a time proportional to the loop cable number (sequence number) (for example, n7 seconds for the nth)
It may also be driven.

The Y-axis direction detection section 28a of the magnetic field detector 26a sequentially detects the strength of the magnetic field from the loop cables 18a to 18e that constitute the loop section 16a of the magnetic field generator 14a, and responds to the strength of the detected magnetic field. The detected signal is input to the position calculator 30. Further, the Z-axis direction detection section 28b detects the loop section 16.
The strength of the magnetic field from the loop cables 18a to 18e constituting the loop cable 18b is detected, and a detection signal corresponding to the strength of the detected magnetic field is input to the position calculator 30.

When the detection signals are input from the Y-axis direction detection section 28a, the position calculator 30 compares the detection signals with each other and selects the signal with the highest signal level.

Then, when the Y-axis direction detection section 28a detects this highest level signal, the position calculator 30 detects the loop cable 18i that is generating a magnetic field, and detects the loop cable 18i that is generating the magnetic field.
The position of the detected loop cable 1B+ with respect to the center of is calculated.

A method for detecting the above-mentioned loop cable 184. For example, a counter is provided in the position calculator 30 to count the input detection signals from the magnetic field detector, or the magnetic field generator 14 side and the magnetic field detector 26 side are synchronized. It can be detected by taking the following. If the pattern for driving the loop cables is the pattern shown in Figure 5, and the level of the detection signal of the magnetic field detector due to the magnetic field from each loop cable is as shown in Figure 6, then the position calculator The loop cable 18i is identified by counting how many consecutive detection signals of the same strength have been received by the highest level detection signal.

The position of the loop cable 18i is determined as follows.

For example, if the loop section 16a is made up of five loop cables 18a=18e as shown in FIG. 3, and the level of the detection signal due to the magnetic field generated by the fourth loop cable 18d is the highest, the position calculator 30 Distance between the center of the loop cable 18c and the center of the loop cable 18d @1
．． ．． is calculated and stored in a storage unit (not shown). Thereafter, the position calculator 30 calculates the deviation δy of the Y-axis direction detection unit 28a with respect to the center of the loop cable 18e in Japanese Patent Application No. 1-65352 or Japanese Patent Application No. 1-223 filed by the present applicant.
Natsuyama is calculated based on the calculation formula shown in No. 035. The position calculation H30 calculates the deviation dy of the Y-axis direction detection unit 28a from the center of the loop portion 16a, that is, how far the center of the polling device 24a deviates from the center of the magnetic field generator 14a in the Y-axis direction. Use the following formula to find out whether

dy=δγ+! , −・−・−・(1) And,
The position calculator 30 similarly operates each polling device 24a.
, 24b, 24c magnetic field generators 14a, 14b, 14c
The offset position in the Y-axis direction and the Z-axis direction from the center of indicate.

Further, the position calculator 30 calculates the position of the underground excavator based on the input excavation amount of each polling device 24a, 24b, 24c by the method shown in Japanese Patent Application No. 1-223035 filed by the applicant of the present application. The pitching angle and rolling angle for the 20 underground excavators 10 are determined and displayed on the display device 32.

Thus, in the embodiment, the magnetic field generators 14a, 1
4b and 14c are rectangular loop cables 18 a-18
e, each loop cable 18
By increasing the ratio (long side/short side) of the long sides and short sides of a to 18e, the magnetic field generated by the short sides of the loop cables 18a to 18e relative to the detected magnetic fields of the magnetic field detectors 26a, 26b, and 26c is Underground excavation l12
The accuracy of detecting the amount of deviation relative to the underground excavator 10 of 0 can be improved. Moreover, a plurality of loop cables 18a
- 18e are arranged in parallel along the long side and each adjacent loop cable is overlapped in half, and the control device 50 sequentially switches and drives each loop cable 18a - 18e, so that each loop cable is different. Since the loop cable is designed to generate a magnetic field at a certain time, it is possible to easily identify the loop cable that is generating the magnetic field. Further, even if the distance between the long sides of the loop cable is narrow, by arranging the number of loop cables according to the expected maximum deviation amount, the necessary detection range can be easily secured.

FIG. 7 shows another embodiment.

In FIG. 7, the control device 50 is composed of a switching section consisting of a multi-channel switch, a relay, etc., and a control section (none of which is shown) that controls the switching section, and the switching section is connected to each loop cable 18a to 18e. A single AC power source 52 is connected. In addition, the control unit of the control device 50 and the position calculator 3
Clock 54.56 is connected to #0, and #door device 50
The drive of each of the loop cables 18a to 18e by the position calculator 30 and the reception of the detection signal from the magnetic field detector 26 by the position calculator 30 are synchronized.

In this embodiment configured as described above, the time of the clock 54 and the clock 56 are synchronized, and the control unit of the control unit W50 outputs a switching control signal to the switching unit. By synchronizing the cycle, length, etc. of capturing the detection signal from the device 26, the loop cable generating the magnetic field can be easily identified.

FIG. 8 shows another embodiment of the loop portion.

In FIG. 8, the loop portion 16 (16a, 16b) consists of a straight common line 34 and a plurality of branch lines 36a to 36g that are orthogonal to the common line 34 and parallel to each other. One end of the branch lines 36a to 36g is connected to the common line 34 at equal intervals, and the other end is connected to a movable contact a of a switching device 38 such as a relay.
- It is connected to g. Further, the fixed contact side of the switch 38 is connected to the AC power source 52 so that a current for generating a magnetic field can be supplied to the loop portion 16.

By switching the switch 38, the loop portion 16 configured in this way can, for example, switch the movable contact a to the 1 side (or the 2 side).
If you connect the movable contact C to the 2 side (or 1 side), a loop consisting of the branch line 36a, the common line 34, and the branch line 36c is formed, and the movable contact C is connected to the 1 side (or 2 side), the movable contact If you connect d to side 2 (or side 1), branch line 36b,
A loop consisting of the common line 34 and the branch line 36d is formed,
The same functions and effects as the loop cables 18a to 18e of the embodiments described above can be obtained.

It should be noted that the loop section 16 configured in this manner can be omitted due to symmetry at the terminals of the switching device 38, if the phase is ignored. Also, for example, move the movable contact a to II! l(
or 2 side), by connecting movable contact g to 2 side (or 1 side), by connecting movable contact S to IN (or 2 side), and connecting movable contact f to 2 side (or 1 side), etc. , the loop can be arbitrarily large.

In the embodiment described above, the magnetic field detector 26 is moved forward by the polling device 24, but the magnetic field generator 14 may be moved forward, or both the magnetic field generator and the magnetic field detector 26 may be moved forward. In addition, in the embodiment described above, the case where two underground excavators 10 and 20 are connected is described, but for example, the poling device 24 for advancing the magnetic field detector 26 may be placed in the reaching shaft. However, it can also be applied when determining the position of an underground excavator with respect to this reaching shaft. and,
In the embodiment described above, a case has been described in which the small-diameter compacted poling device 24 is used as a propulsion device for advancing the magnetic field detector 26, but the propulsion device is not limited to this.

Furthermore, in the above embodiment, a case was explained in which a plurality of magnetic field generators and a plurality of polling devices were provided, but either one or both of them may be set to one, and these may be rotated to position them with respect to the underground excavator. The measurement may be performed by changing the .

〔Effect of the invention〕

As explained above, according to the present invention, the position calculator calculates the distance between the underground excavator and the reference position from the distance traveled by the propulsion machine, and also calculates the distance between the underground excavator and the reference position from the detection signal of the magnetic field detector. The vertical and horizontal deviations of the medium excavator from the reference position are calculated and output.

Therefore, the distance to the reference position of the underground excavator and the amount of deviation of the underground excavator from the reference position can be easily determined, and the relative position of the underground excavator and the reference position can be obtained.

Moreover, since the magnetic field generator consists of a rectangular loop, by increasing the ratio of the long side to the short side of this loop, the detected magnetic field ignores the influence of the magnetic field generated by the short side. The same effect as detecting the strength of a magnetic field generated from a substantially infinitely long parallel conductor can be obtained, and the accuracy of position detection can be improved.

In addition, the magnetic field generator generates a magnetic field by having multiple rectangular loops arranged in parallel so that adjacent loops overlap, and each loop is sequentially switched to generate a magnetic field. Even if the loops are easily detected and the distance between the respective long sides of each loop is reduced and the ratio of long side to short side is increased, the number of loops can be increased or decreased depending on the expected maximum deviation position. , the magnetic field detector does not come off from the magnetic field generator, and a decrease in detection accuracy can be prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a position detection device for an underground excavator according to an embodiment of the present invention, FIG. 2 is a partially enlarged diagram of the embodiment, FIG. 3 is a detailed clear diagram of the magnetic field invention, and FIG. Figure 5 is a timing chart of an embodiment for driving a loop cable that constitutes a magnetic field generator, Figure 6 is an explanatory diagram showing an example of a method for identifying a loop cable that is generating a magnetic field, and Figure 7 is an explanatory diagram showing an example of a method for identifying a loop cable that is generating a magnetic field. The figure is an explanatory diagram of another embodiment, Figure 8 is an explanatory diagram of another embodiment of the loop part of the magnetic field generator, and Figure 9 is a deflection obtained by measuring the magnetic field from a parallel conductor that can be considered to be of infinite length. Figure 10 is a diagram showing the relationship between position and measured deviation, and shows the error of the deviation position obtained by measuring the magnetic field against the change in the ratio of the long side and short side of the rectangular loop with respect to the measured deviation position. be. 10.20---1 underground excavator, 14 a to 14 c
---Magnetic field generator, 16a, 16 b---Loop ridge 18
a to 18e ・-11--loop cable, 19 source device, 24 a to 24 c--propulsion device (Poly device)
, 26 a to 26 c----1 magnetic field detector, 3-
Position calculator, 34...--Common line, 36a-3--
...branch line, 50 --- one control device. Dengu 6g

Claims (1)

[Claims] (1) The magnetic field generator installed at either the tip of the underground excavator or the reference position in front of the underground excavator is composed of a plurality of rectangular loops arranged in parallel, and a control device that arranges matching loops on top of each other and sequentially switches and excites the plurality of loops to generate a magnetic field; and the other of the tip of the underground excavator and the reference position. a magnetic field detector that is installed in the loop and detects the magnetic field generated by each of the loops; a propulsion device that advances at least one of these magnetic field detectors and the magnetic field generator to bring them closer together; A position detection device for an underground excavator, comprising: a position calculator that calculates a relative position of the underground excavator with respect to the reference position based on a forward distance and a detection signal of the magnetic field detector. .