JP2819044B2 - Underground excavator position detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position detection device for detecting the position of an underground excavator excavating underground, and particularly relates to two sets of vehicles which are started facing each other. The present invention relates to a position detection device of an underground excavator suitable for joining an underground excavator underground.

[Related Art] When constructing a tunnel on the sea floor, it is not possible to install many shafts for starting an underground excavator. However, excavating over a long distance with one underground excavator not only causes difficulty in discharging excavated earth and sand, but also involves many dangers. For this reason, when constructing a submarine tunnel, two underground excavators are launched in opposition to each other to shorten the excavation distance of the underground excavator, and tunnels excavated by underground excavators are placed underground. Is performed.

However, if the centers of the two underground excavators are shifted left and right and up and down at the junction, the joined tunnel becomes discontinuous. Therefore, it is necessary to obtain the relative position of the two underground excavators and correct the positional deviation. Conventionally, when correcting the displacement between two underground excavators, the displacement of each underground excavator with respect to the tunnel planning line and the position from a reference position such as a starting point are detected. The relative displacement between the underground excavators was determined, and correction was performed based on the displacement.

Conventionally, the following method has been employed to determine the position of an underground excavator underground.

The position of the underground excavator from the reference point and the deviation from the planned line are determined by underground surveying using transit.

An optical transmission device that generates coherent light such as laser light is installed in the starting shaft of the underground excavator, irradiates the tunnel planning line with this device, and reads the light spot on the target attached to the underground excavator , The position, deviation and declination of the underground excavator from the starting shaft.

The azimuth gyro, pressure squat gauge, inclinometer, and odometer based on the length of the segment assembled in the tunnel are combined to determine the relative position from the reference position.

However, the conventional methods for obtaining the position of the underground excavator described above have the following disadvantages, and it has been difficult to perform underground joining accurately.

The method of (1) requires a large number of measurement points when excavating by bending a tunnel, and cannot be measured in real time, which is impractical. In the method, if the tunnel planning line is bent, the laser beam from the starting shaft may not be able to irradiate the target, and the optical transmitter must be moved to an appropriate position. In addition, since the laser beam cannot be directly irradiated over the entire length of the planning line, each time the optical transmitter is moved, the mutual positional relationship between the target, the optical surveying device, and the tunnel planning line is actually measured, and calculations are performed based on the measurement results. After obtaining the planned route, the position, deviation and declination of the underground excavator must be calculated. For this reason, there is a problem that the transfer, measurement, and calculation of the optical transmission device require labor and the efficiency of the excavation work is reduced.

In addition, the method is also applicable to the case where a cumulative error occurs, it is not suitable for excavation over a long distance, and when excavating a curve with a small radius of curvature, or when excavating a tunnel with a continuous curve Not suitable for And when measuring the relative position of two underground excavators like underground joining,
The error further increases.

Accordingly, the applicant of the present application has attached a magnetic field generator to one of two underground excavators to be joined underground, and provided a magnetic field detector for detecting a magnetic field generated by the magnetic field generator to the other underground excavator. , A magnetic field detector is brought close to a magnetic field generator by a boring device, and a detection signal of the magnetic field detector and an excavation amount of the boring device are input to an arithmetic device, and a position detecting device capable of calculating a relative position between the two is proposed. (Japanese Patent Application No. 1-223035).

[Problems to be solved by the invention]

However, the position detection device disclosed in Japanese Patent Application No. 1-223035 described above uses a rectangular loop cable as a magnetic field generator, and therefore has a large detection error. That is, the position detecting device disclosed in Japanese Patent Application No. 1-223035 utilizes a technology for detecting a magnetic field generated by a parallel cable that is infinitely long or similar to the position detecting device. The magnetic field generated from the pair of sides is also detected by the magnetic field detector, causing an error.

That is, when the magnetic field generator can be regarded as a parallel cable having an infinite length, for example, when the ratio b / a of the long side b to the short side a is a rectangular loop having 100, the center between the long sides The deviation amount in the direction perpendicular to the long side from the deviation amount x ′ obtained based on the strength of the magnetic field detected by the magnetic field detector and the measured value x
9, the inclination becomes 1 as shown in FIG. 9, and the amount of displacement x 'obtained from the detected magnetic field is equal to the measured value x.

However, when b / a is reduced, 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 is based on the actually measured value x on the horizontal axis and the strength of the detected magnetic field on the vertical axis. The inclination when the displacement x 'obtained in this manner is taken becomes smaller than 1 as shown in FIG. 10, and the displacement x' becomes smaller than the actually measured value x, thereby causing a detection error.

Therefore, it is conceivable to configure the magnetic field generator with a plurality of rectangular loops having a large ratio between the long side and the short side. However, in this case, when a plurality of loops are simultaneously driven to generate a magnetic field, it is not possible to distinguish which loop the magnetic field strength detected by the magnetic field detector is due to.

The present invention improves the detection accuracy of the position of an underground excavator obtained based on a detection signal of a magnetic field detector, by being able to know a loop that is generating a magnetic field of a magnetic field generator including a plurality of loops. It is an object of the present invention to provide an underground excavator position detecting device capable of performing the operation.

[Means for solving the problem]

In order to achieve the above object, the underground excavator position detecting device according to the present invention is provided at one of a tip portion of the underground excavator and a reference position in front of the underground excavator. A magnetic field generator comprising a plurality of rectangular loops arranged in parallel, and arranging adjacent loops on top of each other, and exciting each of the loops with a different frequency; and A magnetic field detector is provided at one of the tip of the underground excavator and the reference position, and detects a magnetic field generated by each of the loops.A detection signal of the magnetic field detector is input, and the loop is connected to the magnetic field detector. A filter that passes a detection signal having a frequency corresponding to the frequency being excited, a propulsion device that advances at least one of the magnetic field detector and the magnetic field generator, and brings them close to each other; Advancing distance on the basis of the detection signal passing through the filter and it is characterized by having a position calculator for calculating a relative position with respect to the reference position of the underground excavator.

The position calculator can be provided with a control unit for switching the center frequency of the filter.

[Action]

In the present invention configured as described above, at least one of the magnetic field generator and the magnetic field detector is advanced by the propulsion device, and the magnetic field generator and the magnetic field detector are brought close to each other. And
Each loop of the magnetic field generator is excited at a different frequency in a state where both are close to each other, and the strength of the magnetic field by each loop is detected by the magnetic field detector. The detection signal of this magnetic field detector is
Only a signal corresponding to the excitation frequency of the loop is extracted by the filter and input to the position calculator. The position calculator detects a loop generating a magnetic field in which the largest detection signal is output based on the input detection signal of the magnetic field detector, and obtains a deviation amount of the magnetic field detector with respect to this loop, The vertical and horizontal deviations of the underground excavator from the reference position are calculated and output. Further, the position calculator determines the distance between the underground excavator and the reference position from the distance the propulsion device has advanced. 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 obtained, and the relative position of the underground excavator with respect to the reference position can be obtained.

In addition, the magnetic field generator is composed of a plurality of rectangular loops arranged in parallel, adjacent loops are overlapped, the excitation frequency of each loop is different, and the detection signal of the magnetic field detector is a filter. As a result, the frequency corresponding to the excitation frequency of the loop is selected, so that it is possible to easily know which loop magnetic field has the detected magnetic field strength. Moreover, by increasing the ratio of the long side to the short side of the loop, the detection signal of the magnetic field detector that detects the strength of the magnetic field generated by the long side can ignore the influence of the magnetic field generated by the short side. An effect similar to that of detecting the strength of a magnetic field generated from a substantially infinitely long parallel conductor can be obtained, and the position detection accuracy can be improved. And even if the distance between the long sides of each loop is reduced and the ratio of the long side to the short side is increased, the number of loops makes the magnetic field detector separate from the magnetic field generator by adjusting the number of loops as appropriate. Therefore, a decrease in detection accuracy can be prevented.

Also, a control unit for switching the center frequency of the filter is provided in the position calculator to switch to the center frequency corresponding to the excitation frequency of the loop, and the timing of capturing the detection signal is synchronized with the switching, so that the input detection signal Can be easily known which loop is caused by the magnetic field.

〔Example〕

A preferred embodiment of the underground excavator position detecting device of 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, the underground excavators 10 and 20 have cutter drums 12 and 22 each having a cutter (not shown). The cutter drums 12 and 22 are rotatable and can be stopped at an arbitrary rotation position. Also,
The underground excavators 10 and 20 advance while rotating the cutter drums 12 and 22, thereby taking in the earth and sand excavated by the cutter into the cutter drums 12 and 22, and transferring the soil backward by a screw conveyor or the like. I have. These underground excavators 10 and 20 excavate from different starting shafts in directions approaching each other along the tunnel planning line, and join the excavated tunnels.

On the front part of one underground excavator 20, small diameter boring devices 24a, 24b, 24c of a consolidation excavation type are provided. These boring devices 24a, 24b, 24c have magnetic field detectors 26a, 26b, 26c described in detail below, and
It plays the role of a propulsion device that retreats b and 26c.

Each of the boring devices 24a, 24b, 24c is provided on the rear side of the cutter drum 22 of the underground excavator 20, and is provided at 90-degree intervals on the circumference of the radius r with respect to the center (origin) of the underground excavator 20. Are located. That is, when the X axis is taken in the excavating direction passing through the center of the underground excavator 20, the Z axis is taken in the vertical direction, and the Y axis is taken in the direction orthogonal to the X axis and the Z axis, each boring device 24a, 24b, 24c
(0, 0, r), (0, r, 0), and (0, -r, 0). The cutter drum 22 is provided with through holes (not shown) corresponding to the boring devices 24a, 24b, and 24c. When the cutter drum 22 stops at the standard position, the through holes are formed in the boring devices 24a, 24b, and 24c. Located in front of 24c. Therefore, the boring devices 24a, 24b, 24c
When the cutter drum 22 stops at the standard position, it can dig ahead of the through hole and move the magnetic field detectors 26a, 26b, 26c forward toward the other underground excavator 10. I have.

On the other hand, the other underground excavator 10 is located at a reference position with respect to the underground excavator 20, and a magnetic field generator 14 (to be described in detail later) is provided on the front side of the cutter drum 12 or inside the cutter drum 12.
a, 14b and 14c are provided. These magnetic field generators 14a, 14
b, 14c are the boring devices 24a, 24b, 24 of the underground excavator 20
When the cutter drums 12, 22 are stopped at the standard position, the magnetic field detectors 26a, 26b, 26c The center and the centers of the boring devices 24a, 24b, and 24c match.

Each of the magnetic field generators 14a, 14b, 14c is connected to a power supply 19, and is supplied with power from the power supply 19 to generate a magnetic field. Each of the magnetic field generators 14a, 14b, and 14c has the same structure, and has a structure in which a pair of loop portions 16a and 16b are arranged orthogonally as shown in the example of the magnetic field generator 14a in FIG. .

As shown in FIG. 3, each of the loop portions 16a and 16b has a plurality of, for example, five rectangular loop cables 18a to 18e.
Consists of The loop cables 18a to 18e are arranged in parallel along the long side, and adjacent loop cables overlap each other by half. Then, these loops cables 18a~18e constitute the power supply 19 is connected to an AC power source 19f _a ~19f _e output frequency, each different, so as to generate different AC magnetic field frequencies independently I have.

Note that the loop cable 18a constituting the loop portion 16a
To 18e are arranged such that the long sides thereof are parallel to the Z axis of the underground excavator 10, and the loop cables 18a to 18e constituting the loop portion 16b have the long sides of the Y axis of the underground excavator 10. It is arranged so that it may become parallel.

On the other hand, each of the magnetic field detectors 26a, 26b, 26c is composed of a Y-axis direction detection unit 28a and a Z-axis direction detection unit 28b, as shown in FIG. 2 by taking the magnetic field detector 26a as an example.
Each of the Y-axis direction detection unit 28a and the Z-axis direction detection unit 28b is composed of a pair of detection coils arranged orthogonally, and outputs a detection signal corresponding to the strength of the magnetic field detected by each detection coil. That is, the detection coil of the Y-axis direction detection section 28a detects the strength of the magnetic field generated by the loop section 16a, and the detection coil of the Z-axis direction detection section 28b detects the strength of the magnetic field generated by the loop section 16b. Each outputs a detection signal corresponding to the strength of the magnetic field. Then, each magnetic field detector 26a, 26b, 26
The detection signal of c is input to the position calculator 30 via the filter devices 42a to 42c (see FIG. 1).

As shown in FIG. 4, the filter devices 42a to 42c include band-pass filters 44a and 44b, and the Y-axis direction detecting unit 28a or the Z-axis direction detecting unit 28a is provided on the input side of the band-pass filters 44a and 44b.
The detection coils 46a and 46b constituting the axial direction detection unit 28b are connected. Further, a control unit 32 of the position calculator 30 is connected to the band-pass filters 44a and 44b.
, The center frequency of the filter can be changed in response to a control signal.

The position calculator 30 includes a control unit 32 and a signal processing unit 34, and the signal processing unit 34 receives a timing signal from the control unit 32 and captures detection signals of the magnetic field detectors 26a, 26b, and 26c. , These detection signals and each boring device 24a, 24
From the excavation amounts of b and 24c, the relative distance of the underground excavator 20 to the underground excavator 10, the amount of deviation in the Y-axis direction and the Z-axis direction, the pitching angle of the underground excavator 10 with respect to the axis (X-axis) , The rolling angle is calculated and output to the display device 36 for display (see FIG. 1).

The relative position between the underground excavators 10 and 20 according to the embodiment configured as described above is obtained as follows.

First, the cutter drums 12, 22 of the underground excavators 10, 20 are stopped at the standard position. Next, the boring devices 24a, 24b, and 24c provided in the underground excavator 20 are driven to excavate until the respective ends reach the front surface of the underground excavator 10 that is the reference position, and the magnetic field detectors 26a and 26b , 26c to the magnetic field generators 14a, 14b, 1
4c. The fact that the tip of each boring device 24a, 24b, 24c has reached the front of the underground excavator 10 is detected by the magnitude of the excavation resistance, etc.
The excavation distances of b and 24c are input to the position calculator 30.

Magnetic field detectors 26a, 26b, 26c are magnetic field generators 14a, 14b, 14c
, Each AC power supply 19f _{a of the} power supply 19
Turned on ~19f _e, the magnetic field generator 14a, 14b, the loop cable constituting the loop portion 16a or the loop portion 16b of 14c
Power is supplied to 18a to 18e to generate alternating magnetic fields having different frequencies.

The Y-axis direction detector 28a of the magnetic field detector 26a
Loop cables 18a to 18e constituting the loop portion 16a of a
Then, a detection signal corresponding to the detected magnetic field strength is input to the filter device 42. That is, Y
The detection signals of the detection coils 46a and 46b constituting the axial direction detection unit 28a are input to the band-pass filters 44a and 44b.

The band-pass filters 44a and 44b are a control unit of the position calculator 30.
The center frequency by 32 are sequentially changed to match the output frequency of the AC power supply 19f _a ~19f _e. The detection signal that has passed through the band-pass filters 44a and 44b is
a, 48b, amplified by the signal processor 34 of the position calculator 30
Sent to

The signal processing unit 34 includes a control unit 32 that controls the bandpass filters 44a and 44a.
4b receives the frequency selection signal to be output to the detection signal as a detection signal capture signal, and synchronizes with the capture signal to amplifiers 48a and 48b.
Reads the detection signals output from each other, and compares the detection signals with each other to select a signal having the highest signal level. And
The position calculator 30 detects the loop cable 18i generating the magnetic field detected by the Y-axis direction detection unit 28a of the signal having the highest level, and calculates the detected position of the loop cable 18i with respect to the center of the loop unit 16a. I do.

By the way, as described above, the AC power supplies 19f _{a to} 19f _e
The output frequencies are different, and the magnetic fields generated by the loop cables 18a to 18e are also AC magnetic fields having different frequencies. Therefore, the magnitude of the detection signal of the magnetic field detectors 26a, 26b, 26c for detecting the strength of the magnetic field by the induced electromotive force of the detection coil changes depending on the frequency of the magnetic field generated by the loop cables 18a to 18e.

For example, as shown in FIG. 5, a loop cable A having a width of 2a,
B and C are respectively f (= 276Hz), 2f (= 552Hz), 3f
(= 828 Hz), the detection signals based on the magnetic fields generated by the respective loop cables A, B, and C are as shown in FIG. Therefore, when the loop cables A, B, and C are simultaneously excited, if the loop cable 18i is to be detected only by the magnitude of the detection signal,
Even if the magnetic field detector is within the range of the loop cable A even though the band-pass filters 44a and 44b are used, the strength of the detection signal due to the magnetic field of the loop cables B and C may be larger, and the Detection becomes difficult. Therefore, the magnetic field generated by each loop cable has a magnitude inversely proportional to the excitation frequency, and the detection signal output from the magnetic field detector has a magnitude inversely proportional to the excitation frequency.

By doing so, the intensity distribution of the detection signal becomes as shown in FIG. 7, and the intensity of the detection signal passing through the band-pass filters 44a and 44b becomes as shown in FIG. It can be easily known whether the detection signal has the highest level, and the loop cable 18i can be specified without fail.

The position of the loop cable 18i with respect to the center of the loop portion 16a is obtained as follows.

For example, if the loop section 16a is composed of five loop cables 18a to 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 obtains distances l _y between the center of the loop cable 18d of the cable 18c, and stores in a storage unit (not shown). Thereafter, the position calculator 30 calculates the deviation δ of the Y-axis direction detector 28a with respect to the center of the loop cable 18e.
y is calculated based on the formula shown in Japanese Patent Application No. 1-65352 or Japanese Patent Application No. 1-223035 filed by the present applicant. Then, the position calculator 30 calculates the deviation dy from the center of the loop portion 16a of the Y-axis direction detection section 28a, that is, how much the center of the boring device 24a is shifted in the Y-axis direction with respect to the center of the magnetic field generator 14a. Is determined by the following equation.

_{dy = δy + l y ...... (} 1) The position calculator 30, the boring device 24a in the same manner, 24b, the magnetic field generator 14a of 24c, 14b, the Y-axis direction and the Z-axis direction from the center of 14c Determine the amount of deflection and use the underground excavator 20
Of the center of the underground excavator 10 with respect to the center and the direction of the deviation are calculated and displayed on the display device 32.

Further, the position calculator 30 is provided for each of the inputted boring devices.
From the excavation amounts of 24a, 24b, and 24c, an underground excavator was obtained by the method disclosed in Japanese Patent Application No. 1-223035 filed by the present applicant.
The pitching angle and the rolling angle for the 20 underground excavators 10 are obtained and displayed on the display device 32.

Thus, in the embodiment, the magnetic field generators 14a, 14a
Since the b and 14c are constituted by the rectangular loop cables 18a to 18e, the ratio of the long side to the short side (long side / short side) of each of the loop cables 18a to 18e is increased, so that the magnetic field detector 26a , 26b, 26c, the influence of the magnetic field generated by the short sides of the loop cables 18a to 18e can be reduced, and the accuracy of detecting the amount of deviation of the underground excavator 20 with respect to the underground excavator 10 can be improved. it can. Moreover, the plurality of loop cables 18a to 18e are arranged in parallel along the long side, and the adjacent loop cables are overlapped by half, and the excitation frequencies are made different, and the band-pass filters 44a, 44b By extracting the detection signal corresponding to the excitation frequency, the loop cables 18a to 18e
Are simultaneously excited, the loop cable generating the magnetic field having the largest detection signal can be easily identified. Further, even if the distance between the long sides of the loop cable is narrow, a necessary detection range can be easily secured by arranging the number according to the expected maximum deviation amount.

In the above embodiment, the case where the magnetic field detector 26 is advanced by the boring device 24 has been described, but the magnetic field generator 14 may be advanced, or both the magnetic field generator and the magnetic field detector 26 may be advanced. You may make it do. In the above embodiment, two underground excavators 1
Although the case of joining by 0 and 20 has been described, for example,
The present invention can also be applied to a case where a boring device 24 for advancing the magnetic field detector 26 is arranged in an arrival shaft, and the position of an underground excavator with respect to the arrival shaft is obtained. In the above-described embodiment, a case has been described in which the compacting and excavating type small-diameter boring device 24 is used as a propulsion device for moving the magnetic field detector 26 forward, but the propulsion device is not limited to this.

Further, in the above-described embodiment, a case has been described in which a plurality of magnetic field generators and a plurality of boring devices are provided. However, the number of either one or both of them is set to one, and these are rotated to position the underground excavator. Alternatively, the measurement may be performed with different values.

〔The invention's effect〕

As described above, according to the present invention, the position calculator determines the distance between the underground excavator and the reference position based on the distance the propulsion device has advanced, and detects the underground from the detection signal of the magnetic field detector. The vertical and horizontal deviations from the reference position of the excavator 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 obtained, and the relative position between the underground excavator and the reference position can be obtained.

In addition, the magnetic field generator is composed of a plurality of rectangular loops, each of which is excited at a different frequency, and a filter is used to extract a detection signal corresponding to the excitation frequency of the loop. Even when the excitation is performed, the loop that generates the largest detection signal can be easily specified. By increasing the ratio between the long side and the short side of the loop, the magnetic field to be detected can ignore the influence of the magnetic field generated by the short side, and the magnetic field generated from the parallel conductor that is substantially infinitely long The same effect as detecting the strength is obtained, and the position detection accuracy can be improved.

And even if the distance between the long sides of each loop is reduced and the ratio of the long side to the short side is increased, the magnetic field detector can increase or decrease the number of loops in accordance with the expected maximum deviation amount. The detection accuracy can be prevented from lowering without deviating from the magnetic field generator.

Further, when the center frequency of the filter is changed by the control unit of the position calculator, the change of the center frequency and the acquisition of the detection signal are synchronized, whereby the loop can be more easily performed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a position detecting device of an underground excavator according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of the embodiment, FIG. 3 is a detailed explanatory view of a magnetic field generator, FIG. FIG. 5 is a block diagram of a circuit for processing a detection signal according to the embodiment, FIG. 5 is a layout diagram of a loop cable for explaining a relationship between an excitation frequency and a detection signal, and FIG. 6 is a loop cable shown in FIG. FIG. 7 is an explanatory diagram of the intensity distribution of the detection signal when the intensity of the magnetic field is adjusted, and FIG. 8 is a band-pass diagram of the intensity distribution of the detection signal shown in FIG. Fig. 9 shows the intensity after passing through the filter, Fig. 9 shows the relationship between the amount of deviation obtained by measuring the magnetic field from a parallel conductor that can be regarded as infinite length, and the measured deviation, and Fig. 10 shows a rectangular loop. The error of the deviation obtained by measuring the magnetic field with respect to the change in the ratio of the long side to the short side of the deviation from the measured deviation is It is to figure. 10, 20 ... Underground excavator, 14a-14c ... Magnetic field generator, 16
a, 16b: loop part, 18a to 18e: loop cable, 19
… Power supply unit, 24a to 24c… Propulsion unit (boring device), 26a to 26c… Magnetic field detector, 30… Position calculator, 32
... A control unit, 34 a signal processing unit, 42a to 42c a filter device, 44a and 44b a bandpass filter.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuo Kanemitsu 1200 Manda, Hiratsuka-shi, Kanagawa Prefecture, Japan Examiner, Komatsu Manufacturing Laboratory Co., Ltd. Toshiaki Nakamaki (58) Field investigated (Int.Cl. ⁶ , DB name) E21D 9 / 06 301 G01V 3/08 G01C 15/00

Claims (2)

(57) [Claims] A magnetic field generator provided at one of a tip portion of the underground excavator and a reference position in front of the underground excavator, comprising a plurality of rectangular loops arranged in parallel; Along with arranging adjacent loops on top of each other, a power supply for exciting each of the loops with a different frequency, and a power source provided at one of the tip of the underground excavator and the reference position A magnetic field detector that detects a magnetic field generated by each of the loops; a filter that receives a detection signal of the magnetic field detector and passes a detection signal having a frequency corresponding to a frequency at which the loop is excited; A propulsion device for moving at least one of a magnetic field generator and the magnetic field generator to approach them, and a propulsion device based on a forward distance of the propulsion device and a detection signal passed through the filter. Position detecting device of the underground excavator, characterized in that it comprises a position calculator for calculating a relative position with respect to the reference position of the underground excavator, a. 2. The underground excavator position detecting device according to claim 1, wherein the position calculator has a control unit for switching a center frequency of the filter.