JP2006145302A - Method and system for measuring underground position - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and system for measuring an underground position for simultaneously measuring ground three-dimensional coordinates at a plurality of underground positions. <P>SOLUTION: From a plurality of reference positions R on known three-dimensional coordinates above the ground or in the ground, cyclic reference signals fr modulated by identification code strings P of strong autocorrelation but of weak cross correlation are transmitted on a rotating magnetic field 3 of a prescribed carrier frequency fc into the ground 2. A magnetic field measuring instrument 20 is disposed in a prescribed posture S at a measurement position Q in the ground 2, with three or more reception coil element groups 21 being mounted in a prescribed interrelation on the measuring instrument 20, to measure signals fq induced in the respective coil elements 21 by the magnetic field 3. Phases τ of the respective reference signals fr at the measurement position Q are detected based on a correlation between the signals fq in the respective coil elements 21 and the respective code strings P while detecting the directions θ<SB>R</SB>of the respective reference positions R from phase differences Δτ between coil elements of the phases τ of the respective reference signals fr, the prescribed interrelation of the element groups 21, and their postures S. The ground three-dimensional coordinates of the measurement position Q are calculated from the known three-dimensional coordinates and the directions θ<SB>R</SB>of the respective reference positions R. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an underground position measuring method and system, and more particularly to a method and system for measuring ground three-dimensional coordinates using the principle of electromagnetic induction.
INDUSTRIAL APPLICABILITY The present invention can be used for position measurement when a structure is constructed at a planned position in the ground in the field of civil engineering and architecture. It can also be used when laying underground cables etc. at the planned position in the power / communication field and when laying underground pipes at the planned position in the gas / water supply / sewerage field.

  The earth coordinate system for underground tunnel construction with shield excavators, underground laying work such as communication cables and water pipes, soil surveys during construction of underground structures, and surveys of underground foundations of structures due to earthquakes, etc. Surveying the absolute position of the earth in the ground (hereinafter sometimes referred to as ground three-dimensional coordinates). Conventionally, as a method of surveying the ground three-dimensional coordinates in the ground, for example, as disclosed in Patent Document 1, a sensor probe containing an angular velocity sensor and an acceleration sensor is connected to a communication cable or the like and moved in an underground pipe. A method for measuring the movement direction and distance of the sensor probe from the outputs of both sensors and the transmission amount of the communication cable to obtain the movement locus of the sensor probe and measuring the underground three-dimensional coordinates of the buried piping is known. . Further, as disclosed in Patent Document 2, light from a light source installed in a transmission shaft of a shield excavator is made to reach the face along the underground tunnel by a relay means (reflecting mirror, etc.), and the face is shielded according to the principle of optical wave surveying. A method for measuring the underground position of an excavator is also known.

  However, the method using the angular velocity and acceleration sensor as in Patent Document 1 is likely to accumulate measurement errors due to integration errors, drifts, etc., so accurate surveying is possible when the buried piping is long (the movement distance of the sensor probe is large). Becomes difficult. In addition, the method based on optical wave surveying as in Patent Document 2 also requires that the adjacent relay means be arranged so that the line can be seen in a straight line. Therefore, the arrangement of the relay means becomes complicated in the curved portion, and the underground tunnel becomes long again. Accurate surveying becomes difficult.

  On the other hand, as disclosed in Patent Documents 3 and 4, there is a method of measuring the position and displacement of underground buried objects and excavators using the principle of electromagnetic induction. For example, in Patent Document 3, a detection magnetic field generation device (solenoid coil) is inserted or mounted in a vertical posture in an underground underground pipe or shield excavator, and the magnetic field measurement device is moved while moving the magnetic field measuring device on the ground surface above it. The point where the vertical component of the generated magnetic field is minimized is measured, and the horizontal position and depth of the underground magnetic field generator are measured from the center position and diameter of the circle connecting the points where the vertical component is minimized. . According to this method, it is possible to accurately measure the three-dimensional coordinates of the ground position by moving the magnetic field generator to the ground position to be surveyed regardless of the length of the buried pipe or tunnel. . However, since the methods of Patent Documents 3 and 4 require that the magnetic field measuring device be moved on the ground, for example, when there is an obstacle such as a structure on the ground, the magnetic field measuring device cannot be moved. There is a problem that cannot be applied to mid-position surveying.

  On the other hand, Patent Documents 5 and 6 propose a method of detecting the position of the magnetic field generator in the ground without moving the magnetic field measuring device while using electromagnetic induction. The underground position detection method according to Patent Document 6 will be described with reference to FIG. 11 to the extent necessary for understanding the present invention. As shown in FIG. 5A, a first transmission coil 56 and a second transmission coil 57 having a common center point and orthogonal to each other are mounted on a moving carriage 52 to be inserted into an underground buried pipe 51. The transmission coils 56 and 57 are connected to the signal supply device 60 via signal lines 58 and 59. As shown in FIG. 6B, the signal supply device 60 performs spread spectrum modulation on the carrier wave of, for example, 200 kHz generated by the signal generator 60a with the code sequence of the spread code generator 60b by the spread spectrum modulator 60c, and then AM. The modulator 10d applies AM modulation with a sinusoidal wave of 400 Hz, for example, and applies a cos-modulated alternating current to the first transmission coil 56, and applies a sin-modulated alternating current to the second transmission coil 57. A circular rotating magnetic field is generated from the transmission coils 56 and 57 by applying alternating currents (two-phase alternating current) having a phase difference of 90 degrees to the transmission coils 56 and 57 orthogonal to each other.

  On the other hand, as shown in FIG. 11 (A), a rotary displacement rod 64 having a first receiving coil 66 and a second receiving coil 67 wound around both ends as a magnetic detection coil at an observation point on the ground can be translated. The receiving coils 66 and 67 are connected to the signal measuring devices 70 and 71 via the signal lines 68 and 69, respectively. That is, the pair of receiving coils 66 and 67 are arranged on the same central axis, and the magnetic detection surfaces 66a and 67a of both are made parallel to each other. The signal measuring devices 70 and 71 receive the measurement signals of the magnetic field strength measured by the receiving coils 66 and 67, perform synchronous detection with the reference signal (carrier frequency) from the signal supply device 60, and code sequence of spread spectrum modulation The reception level (for example, a 400 Hz sine wave signal) corresponding to the relative position between the transmission coils 56 and 57 and the reception coils 66 and 67 and the phase of the signal wave is output to the signal display 74.

  In FIG. 11, the reception levels of the reception coils 66 and 67 represent the relative positional relationship with the transmission coils 56 and 57 as a phase difference, and when the two phases coincide with each other, the central axis direction of the reception coils 66 and 67 is the transmission coil 56. , 57 is shown, and when the two phases do not match, the displacement rod 64 is rotated or translated so that the phases match. By obtaining the direction of the underground buried pipe 1 from the central axis direction in which the reception levels of the receiving coils 66 and 67 coincide with each other, the ground three-dimensional coordinates of the underground buried pipe 1 are detected. According to this underground position detection method, it is not necessary to move the magnetic detection coil on the ground, and the underground position below the structure or the like can be measured.

JP-A-8-178653 JP 2001-021356 A JP 57-133373 A JP 59-153112 A JP-A-9-014958 JP-A-9-32503 US Pat. No. 5,337,002 US Pat. No. 6,250,402

  However, the position detection methods of Patent Documents 5 and 6 have a problem that a plurality of underground positions cannot be measured simultaneously. For example, in shield tunnel construction, when tunnels are joined by excavating two shield excavators from different directions toward the same underground position, the underground positions of the two shield excavators are simultaneously set near the joint position. Surveying is required. Further, in underpinning work for constructing a structure below the foundation of the structure, simultaneous surveying of a plurality of underground positions is required. In the position detection method of FIG. 11, when a plurality of transmission coils 56 and 57 are provided in the ground to generate a rotating magnetic field, the combined magnetic fields of the transmission coils 66 and 67 are received at the observation point on the ground. However, it is difficult to detect the underground position of the transmission coils 56 and 57 even if the phases of the combined magnetic fields of the reception coils 66 and 67 are matched. Development of technology that can survey multiple underground positions simultaneously is required.

  In addition, the position detection methods of Patent Documents 5 and 6 measure the three-dimensional coordinates of the ground position at an observation point on the ground, for example, to reflect the measurement result in the operation of an underground shield excavator or the like. Must transmit the ground measurement results to the underground shield excavator via a signal transmission means such as an electric cable, etc., and the shield excavator moving in the ground cannot directly grasp its own three-dimensional coordinates to the ground. There are also problems. On the ground, a global positioning system (hereinafter referred to as GPS) has been developed that can directly measure the three-dimensional coordinates of the ground while moving to any point. Development of a technology that can directly measure the three-dimensional coordinates of the ground while moving to any point is desired.

  Therefore, an object of the present invention is to provide an underground position measuring method and system capable of measuring ground three-dimensional coordinates at a plurality of underground positions simultaneously.

  The present inventor transmits electromagnetic signals from a plurality of reference positions with known ground three-dimensional coordinates to the ground, receives these electromagnetic signals at the ground measurement positions, and measures his own three-dimensional coordinates. We focused on surveying the underground position. However, in this case, as described above, since the combined electromagnetic field signal from each reference position is received at the underground measurement position, it is necessary to separate the combined signal into signals at each reference position. As a method of signal separation, as in the case of terrestrial broadcast radio waves, the transmission frequency of the electromagnetic wave signal transmitted from each reference position is changed to be multi-channel, and the signal is separated by synchronous detection at each reference position at the measurement position in the ground. It is possible. However, since the frequency band with good propagation characteristics in the ground is extremely narrow compared to the ground, considering the separation characteristics (band-pass characteristics) of the synchronous circuit, it is necessary to secure a sufficient number of channels in the case of multi-channeling by frequency. Is difficult. The present inventor obtained knowledge that the method of encoding and separating signals from each reference position is effective for surveying the underground position, and as a result of research and development based on the knowledge, the present invention was completed. .

Referring to the embodiment of FIG. 1 and the flowchart of FIG. 2, the ground position measuring method of the present invention is based on a plurality of reference positions R ₁ , R ₂ , R ₃ whose ground or ground three-dimensional coordinates are known. reference position R _1, R _2, R ₃ correlation strong autocorrelation weak digital reference position identification for each code sequence P _1, P _2, modulated periodic reference signal _{P 3 fr 1, fr 2,} fr 3 Is transmitted to the underground 2 on the rotating magnetic field 3 having a predetermined carrier frequency fc, and three or more receiving coil element groups 21 ₁ , 21 ₂ , 21 ₃ are located at the measurement position Q of the underground 2 where each rotating magnetic field 3 reaches. A magnetic field measuring device 20 attached with a predetermined mutual relationship Q ₁ , Q ₂ , Q ₃ is arranged in a predetermined posture S, and signals fq ₁ induced in the coil elements 21 ₁ , 21 ₂ , 21 ₃ by the rotating magnetic field 3, fq _2, measured fq _3, the measurement based on the correlation between the coil elements 21 _1, 21 _2, 21 ₃ of the measurement signal fq _1, fq _2, fq ₃ and each identification code strings P _1, P _2, P ₃ Each group at position Q Signals fr _1, fr _2, fr phase tau ₁ of _3, τ _2, τ ₃ detects each reference signal fr _1, fr _2, phase tau ₁ of fr _3, τ _2, τ ₃ coil elements inter-position Seen from the measurement position Q by the phase differences Δτ _1-2 , Δτ _1-3 , Δτ _2-3 and the predetermined interrelationships Q ₁ , Q ₂ , Q ₃ and posture S of the coil element groups 21 ₁ , 21 ₂ , 21 ₃ . each reference position R _1, R _2, R ₃ orientation θ _R1, θ _R2, θ _R3 detects, each reference as viewed from the reference position R _1, R _2, known three-dimensional coordinates and measurement position Q of R ₃ The three-dimensional coordinates of the measurement position Q are calculated from the orientations θ _R1 , θ _R2 , θ _{R3 of the} positions R ₁ , R ₂ , R ₃ .

Referring also to the embodiment of FIG. 1, the underground position measurement system of the present invention is installed at a plurality of reference positions R ₁ , R ₂ , R ₃ whose ground or underground three-dimensional coordinates are known and used as a reference. For each position R ₁ , R ₂ , R ₃ , a periodic reference signal fr ₁ , fr ₂ , fr ₃ modulated with a digital reference position identification code string P ₁ , P ₂ , P ₃ with strong autocorrelation and weak cross-correlation Signal transmitters 10 ₁ , 10 ₂ , 10 ₃ that are transmitted to the underground 2 on the rotating magnetic field 3 having a predetermined carrier frequency fc are arranged in a predetermined posture S at the measurement position Q of the underground 2 where each rotating magnetic field 3 reaches. In addition, signals fq ₁ , fq ₂ , fq ₃ induced by the rotating magnetic field ₃ are measured by three or more receiving coil element groups 21 ₁ , 21 ₂ , 21 ₃ attached with a predetermined mutual relationship Q ₁ , Q ₂ , Q _3. Magnetic field measuring device 20, three-dimensional coordinates for each of reference positions R ₁ , R ₂ , R ₃ and identification code strings P ₁ , P ₂ , P ₃ and predetermined interrelationship Q of coil element groups 21 ₁ , 21 ₂ , 21 _{3 1} , Q ₂ Storage means 31, the coil elements 21 _1, 21 _2, 21 ₃ of the measurement signal fq _1, fq _2, each identified by entering the fq ₃ code sequence P _1, P ₂ for storing and Q ₃ and posture S, Phase detection means 32 ₁ , 32 ₂ , 32 ₃ , each reference signal for detecting the phase τ ₁ , τ ₂ , τ ₃ of each reference signal fr ₁ , fr ₂ , fr _{3 at} the measurement position Q based on the correlation with P ₃ fr ₁ , fr ₂ , fr ₃ phases τ ₁ , τ ₂ , τ ₃ phase differences between coil elements Δτ _1-2 , Δτ _1-3 , Δτ _2-3 and coil element groups 21 ₁ , 21 ₂ , 21 predetermined correlation to Q _{1 3,} Q _2, Q ₃ and the posture respective reference positions as viewed from the measurement position Q by the _{S R 1, R 2, R} 3 orientation θ _R1, θ _R2, orientation detection for detecting the theta _R3 The orientations θ _R1 , θ _R2 , θ _R3 and the respective reference positions R _{1 of the} reference positions R ₁ , R ₂ , R ₃ by the means 33 ₁ , 33 ₂ , 33 ₃ and the direction detection means 33 ₁ , 33 ₂ , 33 ₃ , R ₂ , R ₃ coordinate coordinate calculation means 34 for calculating the ground three-dimensional coordinates of the measurement position Q from the three-dimensional coordinates It is something to be made.

Preferably, an attitude measurement device 26 that measures the arrangement attitude S of the magnetic field measurement device 20 is provided, and each reference position R ₁ , R is detected from the measurement attitude S of the attitude measurement device 26 by the direction detection means 33 ₁ , 33 ₂ , 33 _{3. 2} , R ₃ directions θ _R1 , θ _R2 , θ _R3 are detected. More preferably, the three or more receiving coil element groups 21 ₁ , 21 ₂ , and 21 ₃ are attached to three or more predetermined positions on the magnetic field measuring apparatus 20 that are not on the same straight line. The predetermined carrier frequency fc of the rotating magnetic field 3 transmitted by the signal transmission devices 10 ₁ , 10 ₂ , 10 ₃ is preferably a frequency with a small attenuation in the ground, for example, 200 kHz or less, and more preferably about 10 kHz. .

  The ground position measurement method and system of the present invention transmits a periodic reference signal modulated by a reference position identification code string from a plurality of reference positions whose ground three-dimensional coordinates are known to the ground, on a rotating magnetic field, The signal induced by the rotating magnetic field is measured by three or more receiving coil element groups provided at the measurement position in the ground, and each reference signal at the measurement position is based on the correlation between the measurement signal of each coil element and each identification code string. The direction of each reference position viewed from the measurement position is detected from the phase difference of each reference signal between the coil elements, and the measurement position is determined from the known three-dimensional coordinates of each reference position and the direction of each reference position. Since the three-dimensional coordinates of the ground are calculated, the following remarkable effects are obtained.

(A) Since the phase of each reference signal can be detected from a measurement signal obtained by combining a plurality of reference signals, it is possible to simultaneously measure the ground three-dimensional coordinates at a plurality of measurement positions in the ground.
(B) Further, the three-dimensional coordinates of the ground can be directly measured by moving three or more receiving coil element groups to an arbitrary measurement position in the ground.
(C) Since each reference position need not be directly above the measurement position within the range where the rotating magnetic field reaches the measurement position, it can be used for surveying the underground position when there are obstacles such as structures on the ground. Is also applicable.
(D) By positioning a large number of reference positions on the ground appropriately and receiving at least three reference signals at arbitrary positions within the measurement target range in the ground, a positioning system similar to GPS on the ground is Can be realized.
(E) Effective use can be expected for shield construction, horizontal boring construction that surveys the position while moving underground, and underpinning construction that requires simultaneous survey of multiple underground positions below the structure.

  FIG. 1 shows a block diagram of an underground position measurement system according to the present invention. The underground position measurement system shown in the figure includes a signal transmission device 10 installed at each of a plurality of reference positions R having known ground three-dimensional coordinates, a magnetic field measurement device 20 disposed at a measurement position Q of the underground 2, and position measurement. Device 30. A periodic reference signal fr modulated with a different reference position identification code string P by each signal transmitting device 10 is transmitted to the underground 2 on the rotating magnetic field 3, and the rotating magnetic field 3 is generated at the measuring position Q by the magnetic field measuring device 20. The induced signal fq is measured, and the position measurement device 30 calculates the three-dimensional ground coordinate of the measurement position Q from the measurement signal fq and the known three-dimensional coordinates of each reference position R. In the illustrated example, each reference position R is provided on the ground, but the reference position R may be provided in the ground such as in a borehole. Preferably, three or more reference positions R are provided as in the illustrated example, and the ground three-dimensional coordinates of the measurement position Q are calculated based on the known three-dimensional coordinates of the three or more reference positions R.

  Each signal transmission device 10 in the illustrated example supplies a plurality of transmission coils 11 and 12 arranged so as to generate the rotating magnetic field 3 and an alternating current having a phase difference corresponding to the arrangement to each transmission coil 11 and 12. And an alternating current supply device 13. In the illustrated example, as in the case of FIG. 11, a two-phase alternating current is generated from the alternating current supply device 13 by using the first transmitting coil 11 and the second transmitting coil 12 that have the same center point and are orthogonal to each other. By supplying, a circular rotating magnetic field 3 that rotates at the same speed as the alternating current (angular speed of periodic signal fs to be described later = 2πf) is generated from each of the transmission coils 11 and 12. However, the signal transmission device 10 used in the present invention only needs to generate the rotating magnetic field 3, and the configuration is not limited to the illustrated example.

The alternating current supply device 13 in the illustrated example includes a generator 14 that generates a periodic signal fs, a generator 15 that generates a digital reference position identification code string P having a strong autocorrelation and a weak cross-correlation for each supply device 13, A generator (oscillator) 16 that generates a carrier wave signal having a predetermined carrier frequency fc, and modulators 17 and 18 are included. An example of the periodic signal fs is a sine wave signal having a frequency of about 400 Hz as shown in FIG. An example of the digital reference position identification code sequence P is an n-bit (7 bits in the illustrated example) PN (Pseudo Noise) code sequence such as an M sequence (Maximum length sequence) as shown in FIG. . The PN code string is also called pseudo-noise, and is a code string that satisfies three randomities of balance, linkage, and correlation. 4A shows a 7-bit identification code sequence P ₁ {−1, 1, 1, 1, −1, −1, 1} generated by the identification code sequence generator 15 at the reference position R ₁ . Fig (B), the identification code string P ₂ of 7-bit identification code string generator 15 of the reference position R ₂ occurs {1, -1,1,1,1, -1, -1} indicates a.

For example alternating current supply device 13 of the reference position R ₁ is the modulator 17, the absolute value of the periodic signal fs is a sine wave signal with a period T ₀ (see FIG. 3 (B)), the half period T ₀ / second identification bit length code sequence P ₁ is modulated by (see FIG. 4 (a) refer), the transmitter coil 11 to send periodic reference signal fr ₁ ((1) see formula), periodic basis to send to the transmitter coil 12 A signal fr ′ ₁ (see equation (2)) is generated. The waveform of the periodicity reference signal fr ₁ is shown in FIG. Further, the modulator 18 puts the periodic reference signals fr ₁ and fr ′ ₁ on a carrier wave having a carrier frequency fc, and supplies the signals to the transmission coils 11 and 12 at the reference position R ₁ as a two-phase alternating current.

Similarly, the alternating current supply device 13 at the reference position R ₂ generates the periodic reference signals fr ₂ and fr ′ ₂ as shown in FIG. 5B by the modulator 17 and the carrier frequency fc by the modulator 18. supplied to the transmitter coil 11 and 12 of the reference position R ₂ as phase alternating current. The alternating current supply device 13 at the reference position R ₃ also generates periodic reference signals fr ₃ and fr ′ ₃ by the modulator 17 and transmits the reference position R ₃ as a two-phase alternating current at the carrier frequency fc by the modulator 18. Supply to coils 11 and 12. For each of the reference positions R ₁ , R ₂ , and R ₃ , the AC waveform supplied to the transmission coils 11 and 12 is encoded by the digital reference position identification code strings P ₁ , P ₂ , and P ₃ having strong autocorrelation and weak cross-correlation. Thus, even when the rotating magnetic fields 3 generated by the transmission coils 11 and 12 at the reference positions R ₁ , R ₂ and R ₃ are combined, they are combined based on the correlation with the identification code strings P ₁ , P ₂ and P _3. It is possible to separate the reference signals fr ₁ , fr ₂ , fr ₃ of the reference positions R ₁ , R ₂ , R ₃ from the waveform of the rotating magnetic field 3 that has been generated.

Frequency fs of the reference signal fr _1, fr _2, fr ₃ of the reference positions R _1, R _2, R ₃ is not particularly a problem at the same at all the reference position R _1, R _2, R _3, suitably chosen can do. On the other hand, the frequency fc of the carrier wave on which the reference signals fr ₁ , fr ₂ , and fr ₃ are placed is set to a low frequency band as much as possible in order to reduce the attenuation of the rotating magnetic field 3 in the ground, and magnetism existing in the ground (natural world). It is desirable that the frequency is such that a sufficient S / N ratio can be obtained against noise. For example, the carrier frequency fc is set to 200 kHz or less, preferably 100 kHz or less, and more preferably about 10 kHz.

The magnetic field measuring device 20 in the illustrated example arranged at the measurement position Q in the ground 2 has three or more receiving coil element groups 21 ₁ , 21 ₂ , 21 ₃ attached with predetermined interrelationships Q ₁ , Q ₂ , Q _3. , and a demodulator 23 _1, 23 _2, 23 ₃ to take out each receiving coil elements 21 _1, 21 _2, 21 ₃ demodulates the magnetic field strength measured by the measuring signal fq _1, fq _2, fq _3. Demodulator 23 ₁ in the illustrated example, 23 _2, 23 ₃ incorporates a signal generator having the same frequency as the carrier frequency fc of the alternating current supply device 13 (oscillator). Preferably, the receiving coil elements 21 ₁ , 21 ₂ , and 21 ₃ are placed at predetermined positions Q ₁ , Q ₂ , and Q ₃ that are not on the same straight line on the magnetic field measuring device 20, as will be described later with reference to FIG. Install. However, when the number of receiving coil elements 21 is four or more, the receiving coil elements 21 may be attached on the same straight line. The magnetic field measurement device 20 is arranged at a measurement position Q in a predetermined posture (for example, vertical orientation or horizontal orientation) S, or the arrangement posture S is measured by an orientation measurement device 26 described later.

The magnetic field intensity at the measurement position Q is obtained by combining the rotating magnetic field 3 from each reference position R ₁ , R ₂ , R ₃ with time delay and amplitude attenuation due to underground propagation, and each receiving coil by electromagnetic induction. The waveforms of the measurement signals fq ₁ , fq ₂ , fq ₃ generated at the elements 21 ₁ , 21 ₂ , 21 ₃ are the positions of the reference signals fr ₁ , fr ₂ , fr _{3 at} the respective reference positions R ₁ , R ₂ , R _3. The waveform is in a state of interference with phase difference and amplitude difference. 6A and 6B show the phase difference = 414 degrees between the periodicity reference signal fr ₁ of FIG. 5A and the periodicity reference signal fr _{2 of} FIG. 5B at the measurement position Q, and the amplitude ratio. The waveform of the measurement signal fq ₁ measured by the reception coil element 21 ₁ and the waveform of the measurement signal fq ₂ measured by the reception coil element 21 ₂ when (fr ₂ / fr ₁ ) = 0.8 are combined. Each is shown. Measurement signal fq ₃ that is measured by the receiving coil element 21 ₃ also, although the phase and amplitude slightly different, it should be substantially the same waveform.

Measurement signals fq ₁ , fq ₂ , and fq ₃ output from the magnetic field measurement device 20 are input to the position measurement device 30, and the position measurement device 30 calculates the three-dimensional coordinates of the measurement position Q to the ground. The position measurement device 30 in the illustrated example includes a storage unit 31, a phase detection unit 32, a direction detection unit 33, and a coordinate calculation unit 34. The storage means 31 includes three-dimensional coordinates and identification code strings P ₁ , P ₂ , P ₃ for each of the reference positions R ₁ , R ₂ , R _3, and coil elements 21 ₁ , 21 ₂ , 21 _{3 of the} magnetic field measuring device 20. The predetermined mutual relations Q ₁ , Q ₂ , Q ₃ and the arrangement posture S of the magnetic field measuring apparatus 20 are stored. An example of the position measurement device 30 is a computer, and examples of the phase detection means 32, the orientation detection means 33, and the coordinate calculation means 34 are programs built in the computer.

FIG. 2 shows an example of a flowchart of the underground position measurement method using the system of FIG. Hereinafter, with reference to the flowchart, the measurement procedure of the three-dimensional coordinates of the measurement position Q according to the present invention and the processing by the phase detection means 32, the orientation detection means 33, and the coordinate calculation means 34 of the position measurement device 30 will be described. First, in step S101, a plurality of reference positions R on which the signal transmission devices 10 are to be installed are placed on the ground or in the ground so that the rotating magnetic field 3 of each signal transmission device 10 reaches the measurement position Q of the underground 2 to be measured. Set (see also FIG. 10). Further, the three-dimensional ground coordinates of each reference position R are measured by, for example, GPS, and stored in the storage unit 31 of the position measuring device 30. The signal transmission device 10 is installed at each set reference position R, and the periodic reference signal fr modulated by the different reference position identification code string P is placed on the rotating magnetic field 3 from each reference position R in step S102. Call 2nd. In step S103, the magnetic field measuring device 20 is arranged in a predetermined posture S at the measurement position Q in the ground 2. In step S105, the receiving coil elements 21 ₁ , 21 ₂ , 21 ₃ of the magnetic field measuring device 20 are rotated by the rotating magnetic field 3. The induced measurement signals fq ₁ , fq ₂ , and fq ₃ are measured and input to the position measurement device 30.

Step S106 in FIG. 2 shows processing by the phase detection means 32 of the position measuring device 30. The position measurement apparatus 30 in the illustrated example has three phase detection means 32 ₁ , 32 ₂ , and 32 ₃ , and each of the phase detection means 32 ₁ , 32 ₂ , and 32 ₃ has a receiving coil element 21 ₁ , 21 ₂ , 21 _{3, respectively.} Measurement signals fq ₁ , fq ₂ , fq ₃ are input and the correlation value M with each identification code string P ₁ , P ₂ , P ₃ is obtained while shifting the phase τ, and the identification code strings P ₁ , P ₂ , P ₃ correlation values M is the maximum of the phase τ _1, τ _2, the tau _3, each reference signal at each measuring position Q fr _1, fr _2, phase tau ₁ of fr _{3, τ 2,} is detected as tau ₃ . The correlation value M between the measurement signal fqj (j = 1, 2, 3) and the identification code string Pi (i = 1, 2, 3) can be defined, for example, as in equation (10). However, the calculation method of the correlation value M between the measurement signal fqj and the identification code string Pi is not limited to the equation (10).

For example, in the phase detection means 32 ₁ of the illustrated example, as shown in FIG. 7A, the portion of the measurement signal fq ₁ (see FIG. 6A) of the receiving coil element 21 ₁ with the phase τ = 0 to 1260 degrees storage means 31 identification code string stored in the P ₁ (see FIG. 4 (a) see) the product of the identification code string P ₁ of the period T correlation value by integrating over (see FIG. 4 (a) in the 1260 degrees) M Find (τ). Next, as shown in FIG. 7B, the cycle for obtaining the correlation value M (τ) is repeated while shifting the phase τ within the range of the period T, and the phase τmax at which the correlation value M (τ) is maximized is determined as the receiving coil. detecting a phase tau ₁ of the reference signal fr ₁ in 21 _1. In the embodiment of FIG. 7, the correlation value M (tau) is the phase in FIG (A) is larger than the phase of FIG. (B), by the repetition of this cycle, for example, the reference signal fr in the receiving coil 21 ₁ to detect the _first phase τ ₁ = 0.

Similarly, in the illustrated phase detection means 32 ₂ , as shown in FIG. 7C, the product of the measurement signal fq ₂ (see FIG. 6B) of the reception coil element 21 ₂ and the identification code string P ₁ is calculated. By repeating the cycle for obtaining the correlation value M (τ) by integrating over the period T of the identification code string P ₁ while shifting both phases τ within the range of the period T, the correlation value M (τ) is maximized. detecting a phase tau ₂ of the reference signal fr ₁ in the receiving coil 21 ₂ as a phase .tau.max. In the illustrated example, for example, the phase τ ₂ = 45 degrees of the reference signal fr ₁ in the receiving coil 21 ₂ is detected. Further the phase detecting means 32 _3, the cycles for obtaining the receiving coil element 21 ₃ of the measurement signal fq ₃ and the identification code strings P ₁ correlation values by integrating over the period T of the identification code strings P ₁ product of M (tau) repeatedly detects the phase tau ₃ of the reference signal fr ₁ in the receiving coil 21 ₃ in the same manner. The phase detection means 32 ₁ , 32 ₂ , 32 ₃ can obtain all the phases τ ₁ , τ ₂ , τ ₃ of the reference signal fr _{1 in} the receiving coil elements 21 ₁ , 21 ₂ , 21 _{3 at} the measurement position Q. .

Phase detecting means 32 _1, 32 _2, in 32 _3, the phase tau ₁ of the reference signal fr _1, tau _2, not only tau _3, phase tau ₁ of the reference signal fr _2, tau _2, tau _3, and the reference signal fr ₃ phase τ _1, τ _2, τ ₃ can also be detected similarly. That is, in the phase detecting means 32 _1, 32 _2, 32 _3, the receiving coil elements 21 _1, 21 _2, 21 ₃ of the measurement signal fq _1, fq _2, fq ₃ the identification code string P ₂ (FIG. 4 (B) refer to ) To detect the phase τ ₁ , τ ₂ , τ ₃ of the reference signal fr _{2 at} the measurement position Q, and the measurement signals fq ₁ , fq ₂ , fq The phase τ ₁ , τ ₂ , τ ₃ of the reference signal fr _{3 at} the measurement position Q may be detected by obtaining the phase τmax that maximizes the correlation value M (τ) between ₃ and the identification code string P ₃ .

Step S107 in FIG. 2 shows processing by the orientation detection means 33 of the position measuring device 30. The position measurement apparatus 30 in the illustrated example has three direction detection means 33 ₁ , 33 ₂ , and 33 ₃ , and in each of the direction detection means 33 ₁ , 33 ₂ , and 33 ₃ , each reference signal fr ₁ , fr ₂ , fr ₃ The phase differences Δτ _1-2 , Δτ _1-3 , Δτ _2-3 between the coil elements of the phases τ ₁ , τ ₂ , τ ₃ are obtained, and the phase differences Δτ _1-2 , Δτ _1-3 , Δτ _{2- 3} and the coil elements 21 _1, 21 _2, 21 ₃ of a predetermined interrelationship Q _1, Q _2, Q ₃ and the placement position S, the reference position R _1, R _2, R ₃ orientation theta _R1, theta _R2, θ _R3 is detected.

For example, the orientation detection means 33 _{1 in the} illustrated example inputs all the phases τ ₁ , τ ₂ , τ ₃ of the reference signal fr _{1 at} the measurement position Q from the phase detection means 32 ₁ , 32 ₂ , 32 ₃ , and the reference signal fr ₁ Phase difference Δτ _1-2 between the coil elements 21 ₁ and 21 ₂ , phase difference Δτ _1-3 between the coil elements 21 ₁ and 21 ₃ , and phase difference Δτ ₂ between the coil elements 21 ₂ and 21 _{3. Find -3} . Since the reference signal fr ₁ rotates around the reference position R ₁ at the angular velocity of the periodic signal fs = 2πf, the phase difference between the coil elements 21 ₁ and 21 ₂ of the reference signal fr ₁ as shown in FIG. Δτ _1-2 corresponds to a circumferential angle having a line segment connecting the positions Q ₁ and Q ₂ of the coil elements 21 ₁ and 21 ₂ as a chord and a reference position R ₁ as an apex. That is, the reference position R ₁ includes the positions Q ₁ and Q ₂ of the coil elements 21 ₁ and 21 ₂ , and a spherical surface C _{1 having} a circumferential angle = Δτ _1-2 (in the embodiment shown in FIGS. 7A and 7B, a circle). It should be on the spherical surface C1) with a peripheral angle = 45 degrees. The reference position R ₁ includes the positions Q ₁ and Q ₃ of the coil elements 21 ₁ and 21 ₃ and is on the spherical surface C2 with the circumferential angle = Δτ _1-3 , and the position Q _{2 of the} coil elements 21 ₂ and 21 ₃ , Q ₃ and also on a spherical surface C3 with a circumferential angle = Δτ _2-3 . Therefore, the predetermined positions Q ₁ , Q ₂ , Q _{3 on} the magnetic field measuring device 20 of each coil element group 21 ₁ , 21 ₂ , 21 ₃ stored in the storage means 31 and the predetermined posture S of the magnetic field measuring device 20 are used. As shown in FIG. 8, by obtaining the coordinates of the intersection R ₁ of the spherical surfaces C 1, C 2, C ₃ from the phase differences Δτ _1-2 , Δτ _1-3 , Δτ _2-3 between the coil elements, the direction detecting means In 33 ₁ , the direction θ _R1 of the reference position R ₁ viewed from the measurement position Q can be detected.

Similarly, in the direction detection means 33 ₂ in the illustrated example, phase differences Δτ _1-2 , Δτ _1-3 , Δτ _2-3 between the coil elements are obtained from the phases τ ₁ , τ ₂ , τ ₃ of the reference signal fr _2. As shown in FIG. 8, the orientation θ _R2 of the reference position R ₂ viewed from the measurement position Q can be detected by obtaining the intersection R ₂ of the spherical surfaces C1, C2, and C3. In addition the orientation detection means 33 _3, the phase tau ₁ of the reference signal fr _3, tau _2, tau ₃ phase .DELTA..tau _1-2 between coil elements mutually from, .DELTA..tau _1-3, a calculated .DELTA..tau _2-3, 8 by obtaining the intersection R ₃ spherical C1, C2, C3 as it can detect the orientation theta _R3 of the reference position R _3, as viewed from the measurement position Q.

Reference numeral F in FIG. 8 represents the line of intersection of the spherical C1, C2, the intersection R ₁ of the spherical C1, C2, C3 indicate that obtained as the intersection of the intersection line F and the spherical C3. FIG. 8 shows an example in which receiving coil elements 21 ₁ , 21 ₂ , and 21 ₃ are attached to three predetermined positions Q ₁ , Q ₂ , and Q ₃ that are not on the same straight line on the magnetic field measuring apparatus 20. When the number of 21 is four or more, the direction θ _R of each reference position _R is detected from the phase difference Δτ between the four or more coil elements even when the receiving coil elements 21 are mounted on the same straight line. Is possible.

Step S108 in FIG. 2 shows processing by the coordinate calculation means 34 of the position measuring device 30. The coordinate calculation unit 34 in the illustrated example inputs the orientations θ _R1 , θ _R2 , and θ _R3 of the reference positions R ₁ , R ₂ , and R ₃ from the direction detection units 33 ₁ , 33 ₂ , and 33 ₃ , and stores them in the storage unit 31. From the stored three-dimensional coordinates of the reference positions R ₁ , R ₂ , and R ₃ , the three-dimensional ground coordinates of the measurement position Q are calculated according to the principle of triangulation. FIG. 9 shows a method of calculating the ground three-dimensional coordinates of the measurement position Q based on the known three-dimensional coordinates of three or more reference positions R. As shown in the figure, the three-dimensional coordinates of the measurement position Q to the ground are the plane H _1-2 including the reference positions R ₁ and R ₂ and the orientation vectors θ _R1 and θ _R2 , the reference positions R ₁ and R ₃ and the orientation vector. It can be calculated as the intersection of the plane H _1-3 including θ _R1 and θ _R3 and the plane H _2-3 including the reference positions R ₂ and R ₃ and the orientation vectors θ _R2 and θ _R3 . The symbol L in the figure represents an intersection line between the planes H _1-2 and H _1-3 , and indicates that the three-dimensional coordinates of the measurement position Q to the ground are obtained as an intersection between the intersection line L and the plane H _2-3 . However, if the orientations θ _R1 , θ _{R2 of} at least two reference positions R ₁ , R ₂ can be detected, the angles at the vertices of the triangles Q, R ₁ , R ₂ are determined, so the reference positions R ₁ , R ₂ It is possible to calculate the ground three-dimensional coordinates of the measurement position Q from the known three-dimensional coordinates by the principle of triangulation. The calculated three-dimensional coordinates of the measurement position Q with respect to the ground are, for example, output to the output device (display device) 39 of the position measurement device 30 and confirmed.

  In step S109 in FIG. 2, it is determined whether or not it is necessary to calculate the ground three-dimensional coordinates of another underground measurement position Q. If necessary, the process returns to step S103, and the magnetic field measurement device is moved to the next measurement position Q. 20 is arranged and steps S103 to S108 described above are repeated. For example, if a large number of reference positions R are arranged on the ground so that a plurality of reference signals fr can be received at an arbitrary position Q within the measurement target range of the underground 2 (see FIG. 10), the flowchart of FIG. Thus, it becomes possible to directly measure the three-dimensional coordinates of the ground at an arbitrary position Q while moving the measurement target range, and a positioning system similar to GPS on the ground can be realized in the ground. Further, according to the present invention, it is possible to survey the ground three-dimensional coordinates simultaneously at a plurality of measurement positions Q in the ground.

  Thus, the “underground position measuring method and system capable of simultaneously measuring ground three-dimensional coordinates at a plurality of underground positions”, which is an object of the present invention, can be achieved.

In the embodiment of FIG. 1, an attitude measurement device 26 that measures the arrangement attitude S of the magnetic field measurement device 20 is provided, and the arrangement attitude S of the magnetic field measurement device 20 is measured by the attitude measurement device 26 in step S104 of FIG. The orientations θ _R1 , θ _R2 , and θ _R3 of the reference positions R ₁ , R ₂ , and R ₃ are detected from the posture S. In order to detect the directions θ _R1 , θ _R2 , θ _R3 of the respective reference positions R ₁ , R ₂ , R ₃ by the direction detecting means 33 ₁ , 33 ₂ , 33 ₃ in step S107 in FIG. 2, the coil element 21 ₁ , 21 ₂ , 21 ₃ are required. In the present invention, it is sufficient to arrange the magnetic field measuring device 20 in a vertical direction or a horizontal direction. However, there may be a case where a sufficient S / N ratio cannot be obtained with respect to magnetic noise, or the posture may be shifted for some reason. The posture measurement device 26 in the illustrated example includes a posture control device 27, and selects the direction of the magnetic field measurement device 20 that provides a sufficient S / N ratio by the posture control means 37 and the posture control device 27 of the position measurement device 30. The orientation S of the magnetic field measurement device 20 is measured by the orientation measurement means 36 and the orientation measurement device 26 of the position measurement device 30 and stored in the storage means 31. By providing the attitude measurement device 26 and the attitude control device 27, it can be expected that the underground position measurement system of the present invention is automated.

FIG. 10 shows an embodiment in which the present invention is applied to underground tunnel construction using a plurality of shield excavators 6. In the illustrated example, a plurality of reference positions R on both sides of the plan line 9 along the excavation plan line 9 so that a plurality of reference signals fr can be received at each measurement position Q on the excavation plan line 9 in the ground 2. _{1 to} R ₁₁ are set on the ground, and signal transmission devices 10 ₁ to 10 ₁₁ are installed at reference positions R _{1 to} R ₁₁ , respectively. According to the present invention, it is possible to simultaneously measure the three-dimensional coordinates of the ground position Q at the tip of the shield excavator 6 while digging a plurality of shield excavators 6 along the planned line 9. This can be used effectively when excavating the excavator 6 from different directions toward the same underground position to join the tunnel. Even when there is a structure 5 or the like on the ground, it can be applied to surveying the measurement position Q below the structure as long as it is within the range where the plurality of reference signals fr reach. Therefore, it can be expected to be effectively used for underpinning work that requires simultaneous surveying of a plurality of underground positions below the structure.

It is explanatory drawing of one Example of this invention. It is an example of the flowchart of the underground position measuring method of this invention. It is explanatory drawing of an example of the periodic signal fs before the modulation by the identification code string P. 5 is an explanatory diagram of an example of an identification code string P for each reference position R. FIG. It is explanatory drawing of an example of the periodicity reference signal fr (before the modulation | alteration by the carrier frequency fc) after modulating with the identification code string P. FIG. It is explanatory drawing of an example of the measurement signal fq which a coil element outputs It is explanatory drawing of the method of detecting the phase of each reference signal fr from the measurement signal fq. It is explanatory drawing of the method of detecting the direction of each reference position R seen from the measurement position Q by the phase difference Δτ between coil elements of each reference signal fr. 4 is an explanatory diagram of a method for calculating the three-dimensional coordinates of the measurement position Q from the three-dimensional coordinates of each reference position R and the direction of each reference position R viewed from the measurement position Q. It is explanatory drawing of the other Example of this invention. It is explanatory drawing of an example of the conventional underground position detection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ground surface 2 ... Underground 3 ... Rotating magnetic field 5 ... Structure 6 ... Shield excavator 7 ... Horizontal boring machine 9 ... Drilling plan line
10 ... Signal transmitter 11 ... Transmission coil
12 ... Transmitting coil 13 ... AC current supply device
14 ... periodic signal generator 15 ... identification code string generator
16 ... Carrier signal generator 17 ... Modulator
18 ... Modulator
20 ... Magnetic field measuring device 21 ... Receive coil element
22 ... Support 23 ... Demodulator
26… Attitude measurement device 27… Attitude control device
30 ... Position measuring device 31 ... Memory means
32 ... Phase detection means 33 ... Direction detection means
34: Coordinate calculation means
36 ... Attitude measurement means 37 ... Attitude control means
39 ... Output device (display device)
51… Underground piping 52… Moving cart
53 ... wheel 54 ... control device
55, 58, 59, 62, 63, 65 ... Signal line
56 ... 1st transmission coil 57 ... 2nd transmission coil
58, 59 ... Power line 60 ... Signal supply device
60a ... Signal generator 60b ... Spread code generator
60c ... Spread spectrum modulator
60d AM modulator
61… Magnetic detector 62… Base
63 ... Support plate 64 ... Displacement rod
65 ... Moving means 66 ... First receiver coil
67 ... Second receiving coil 70 ... First signal measuring instrument
71 ... Second signal measuring instrument 74 ... Signal indicator
74a… Display screen
fc ... carrier frequency fq ... measurement signal
fr ... periodicity reference signal fs ... periodicity signal A ... intersection C ... spherical surface F ... intersection line H ... plane L ... intersection line M ... correlation value P ... digital reference position identification code string Q ... measurement position
Qi: Coil correlation (coil mounting position)
R: Reference position S: Arrangement posture or measurement posture θ _R : Reference position direction τ: Phase Δτ: Phase difference

Claims (8)

  A rotating magnetic field having a predetermined carrier frequency is generated from a periodic reference signal modulated with a digital reference position identification code string having a strong autocorrelation and a weak cross-correlation for each reference position from a plurality of reference positions whose ground or ground three-dimensional coordinates are known. A magnetic field measuring device having three or more receiving coil element groups attached in a predetermined relationship at a measurement position in the ground where each rotating magnetic field arrives is placed in a predetermined posture and placed in the ground. To measure the signal induced in each coil element, detect the phase of each reference signal at the measurement position based on the correlation between the measurement signal of each coil element and each identification code string, and coil the phase of each reference signal The direction of each reference position seen from the measurement position is detected by the phase difference between the elements and the predetermined mutual relationship and posture of the coil element group, and each reference position seen from the known three-dimensional coordinates of each reference position and the measurement position Underground position measuring method comprising calculating the ground three-dimensional coordinates of the measurement position from the orientation.   2. The measuring method according to claim 1, wherein the three or more receiving coil element groups are attached to three or more predetermined positions that are not on the same straight line on the magnetic field measuring apparatus. 3. The measurement method according to claim 1, wherein the digital reference position identification code string is an n-bit PN (Pseudo Noise) code string, and the periodic reference signal is an absolute value of a sine wave having a period T ₀ and its half period T. _It is assumed that the signal is modulated by a PN code string having a bit length of 0/2, and the product of the measurement signal and each PN code string is integrated over the period T of the PN code string while shifting the phase of the measurement signal of each coil element. An underground position measurement method in which the phase of the measurement signal having the maximum integral value is detected as the phase of each reference signal.   A periodic reference signal modulated with a digital reference position identification code string that is installed at a plurality of known reference positions where ground or underground three-dimensional coordinates are known, and each of the reference positions has a strong autocorrelation and a weak cross-correlation. A signal transmitting device that transmits the rotating magnetic field to the ground, and the three or more receiving coil element groups that are arranged in a predetermined posture at a measurement position in the ground where each rotating magnetic field reaches and are attached in a predetermined relationship with each other. Magnetic field measuring apparatus for measuring a signal induced by a rotating magnetic field, storage means for storing a three-dimensional coordinate and identification code string for each reference position and a predetermined correlation and posture of the coil element group, measurement of each coil element Phase detection means for inputting a signal and detecting the phase of each reference signal at the measurement position based on the correlation with each identification code string, the phase difference between the coil elements of the phase of each reference signal and the coil element Direction detection means for detecting the orientation of each reference position viewed from the measurement position according to a predetermined mutual relationship and posture of the group, and the measurement position from the orientation of each reference position by the orientation detection means and the three-dimensional coordinates of each reference position An underground position measurement system comprising coordinate calculation means for calculating ground three-dimensional coordinates.   5. The measurement system according to claim 4, wherein an attitude measurement device that measures an arrangement attitude of the magnetic field measurement device is provided, and an orientation detection unit detects an orientation of each reference position from the measurement orientation of the orientation measurement device by the orientation detection unit. system.   The measurement system according to claim 4 or 5, wherein the three or more receiving coil element groups are attached to three or more predetermined positions that are not on the same straight line on the magnetic field measuring device. As in any of the measurement system of claims 4 6, wherein the digital reference position identification code string as the n-bit PN (Pseudo Noise) code sequence, the absolute value of the sine wave of period T ₀ the periodic reference signal and those modulated half cycle T _0/2 bit length of the PN code sequence, wherein the phase detection means, wherein the the product of the measurement signal and the PN code sequence while shifting the phase of the measurement signal of each coil element An underground position measurement system in which the phase of a measurement signal that is integrated over the period T of the PN code string and the integration value is maximum is detected as the phase of each reference signal.   8. The measurement system according to claim 4, wherein the predetermined carrier frequency of the rotating magnetic field is a frequency with a small attenuation in the ground.

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