JP7835396B2 - Displacement measurement system and displacement measurement method - Google Patents

Description

This invention relates to a displacement measurement system and a displacement measurement method for measuring displacement in mountain tunnels.

During construction of mountain tunnels, there is a type of measurement called "A-measurement." A-measurements include, for example, "internal displacement measurement,""crown settlement measurement,""leg settlement measurement," and "ground surface settlement measurement." Even when the displacement is small, the standard measurement frequency is "1 to 2 times per day," which requires effort and time. Until now, displacement measurements have been performed using lasers (for example, using optical distance meters). Regarding displacement measurement, technologies such as those described in Patent Documents 1 and 2 are known.
The technology described in Patent Document 1 is a method for measuring the internal displacement of a tunnel. In the measurement method of Patent Document 1, several measurement points are set up within the same cross-section of the tunnel, and the set up measurement points are sighted using an optical measuring instrument (optical distance meter). The position data of the sighted measurement points is acquired in a three-dimensional coordinate system, and the distance between measurement points is determined by coordinate calculation. Here, each measurement point is set up by embedding bolts in the ground, sprayed concrete surface, or steel support surface around the tunnel, and attaching a measuring reflector plate with a reflective sheet to the bolt with a nut.
The technology described in Patent Document 2 is a system for measuring tunnels under construction. The system in Patent Document 2 comprises a plurality of measuring devices for measuring predetermined control dimensions inside the tunnel, and communication means for transmitting the measurement data from these measuring devices to a predetermined control center. For example, assuming the measurement of internal displacement, the measuring device consists of a laser transmitter/receiver equipped with the function of transmitting and receiving a laser horizontally from the inner wall of the tunnel, and a laser reflector equipped with the function of reflecting the laser light transmitted by the laser transmitter/receiver back towards the laser transmitter/receiver.

Japanese Patent Application Publication No. 5-99670 Japanese Patent Publication No. 2000-304531

Conventional laser-based measurements have the problem of requiring a lot of time and effort. For example, optical distance meters and laser transmitters/receivers must be kept level, and installation and verification work takes time. In particular, there are various obstacles inside tunnels, and if these obstacles interfere with laser measurements, the optical distance meters and laser transmitters/receivers must be moved and the installation and verification work must be repeated, which is a great deal of trouble.
From this perspective, the present invention provides a displacement measurement system and a displacement measurement method that can reduce the labor and time required for displacement measurement in mountain tunnels.

The displacement measurement system according to the present invention is a displacement measurement system for mountain tunnels. This displacement measurement system comprises a transmitting unit installed at a measurement point on the inner wall of the tunnel and transmitting ultrasonic waves, a receiving unit that receives ultrasonic waves transmitted from the transmitting unit, and a position estimation unit that estimates the position of the transmitting unit based on the ultrasonic waves received by the receiving unit. The receiving unit is composed of a plurality of microphones arranged at each vertex of a rectangular parallelepiped , and the position estimation unit estimates the position of the transmitting unit based on the time difference in which the ultrasonic waves reach each microphone.
The position estimation unit, for example, detects the peaks of the ultrasonic signals received by each of the microphones, determines the time difference between these peaks, and estimates the position of the transmitter using a position estimation algorithm.
In the displacement measurement system according to the present invention, there is no need to ensure horizontal alignment, and the time required for installation and verification work can be reduced compared to conventional systems. As a result, the labor and time required for displacement measurement can be reduced compared to conventional systems. In particular, even if the arrival of ultrasonic waves is obstructed by obstacles in the tunnel, the receiving unit only needs to be moved, making installation and verification work extremely easy.

The position estimation algorithm uses, for example, the least squares method. The position estimation algorithm represents the coordinates of the transmitter as the sum of an initial value and an error, and by changing the initial value and repeating the calculation, the error is reduced until the error becomes infinitely small, at which point the calculated coordinates of the transmitter are taken as the true position. As the initial value, it is preferable to set the coordinates on the extension of the line segment connecting the first microphone that first received the ultrasound and the last microphone that last received it, specifically on the extension on the side of the first microphone.
This approach speeds up convergence and reduces the likelihood of finding the wrong solution (increasing the certainty of finding the correct solution).
The transmitting units may be installed at multiple locations within the same cross-section of the mountain tunnel, and the position estimation unit may calculate the distance between two points from the position of each transmitting unit.
The transmitting unit may be housed in a socket embedded in the inner wall of the tunnel. This makes it less likely for the transmitting unit to interfere with blasting or other operations, and also prevents it from unintentionally becoming detached.
The receiving unit may be installed inside the mountain tunnel by means of legs that can be erected on the ground or by a fixing part that is magnetically fixed to a support structure. This makes the installation of the receiving unit easier.

The displacement measurement method according to the present invention is a method for measuring the displacement of a mountain tunnel. This displacement measurement method comprises a transmission step of transmitting ultrasonic waves from a transmitting unit installed at a measurement point on the inner wall of the tunnel, a reception step of receiving ultrasonic waves transmitted from the transmitting unit with a receiving unit, and a position estimation step of estimating the position of the transmitting unit based on the ultrasonic waves received by the receiving unit. The receiving unit is composed of a plurality of microphones arranged at each vertex of a rectangular parallelepiped , and in the position estimation step, the position of the transmitting unit is estimated based on the time difference in which the ultrasonic waves reach each microphone.
In the displacement measurement method according to the present invention, for example, it is not necessary to ensure horizontality, and the time required for installation and verification work can be shortened compared to conventional methods. As a result, the labor and time required for displacement measurement can be reduced compared to conventional methods. In particular, even if the arrival of ultrasonic waves is obstructed by obstacles in the tunnel, it is only necessary to move the receiving unit, making installation and verification work very easy.

According to this invention, the labor and time required for displacement measurement in mountain tunnels can be reduced.

This is a schematic diagram of a displacement measurement system according to an embodiment of the present invention. This is a schematic diagram of the transmitting device. This is a schematic diagram of the receiving device. This is a schematic diagram of the control device. This is a block diagram of a displacement measurement system according to an embodiment of the present invention. This is a diagram illustrating the definitions used in the position estimation algorithm. This is a program flow for a displacement measurement system according to an embodiment of the present invention. This figure illustrates the measurement operation of a displacement measurement system according to an embodiment of the present invention. This figure illustrates the measurement procedure of a displacement measurement system according to an embodiment of the present invention. This is a diagram illustrating the measurement procedure of a displacement measurement system according to an embodiment of the present invention. These are examples of measurement screens; (a) is the measurement screen from the first measurement operation, and (b) is the measurement screen from the second measurement operation with the receiving device in a different position. This is an illustrative diagram of the information synthesis process used to store information in a group.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate. Each figure is only a schematic representation to the extent that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated examples. In each figure, common or similar components are denoted by the same reference numerals, and their redundant descriptions are omitted.
<Configuration of the displacement measurement system according to the embodiment>
Referring to Figure 1, the configuration of the displacement measurement system 1 according to the embodiment will be described. Figure 1 is a schematic diagram of the displacement measurement system 1 according to the embodiment. The displacement measurement system 1 is a system for measuring the displacement of a tunnel. The displacement measurement system 1 can be used in various situations for measuring the displacement of a tunnel, and is not particularly limited to the object of measurement. In this embodiment, "internal displacement measurement" in "Measurement A" will be used as an example. The purpose of internal displacement measurement is to obtain data for confirming the stability of the tunnel and the effectiveness of the support structure, determining the timing of support structure construction, and determining the timing of lining placement. For example, as a general rule, internal displacement measurements are performed at one location (one cross section) every "30m" and at locations (cross sections) where the design pattern is changed, and the measurement interval is adjusted considering the stage of construction and the grade of the ground.

As shown in Figure 1, the displacement measurement system 1 mainly comprises a transmitter 2, a receiver 3, an operating device 4, and an administrator terminal 5. In the displacement measurement system 1, ultrasonic waves emitted from the transmitter 2 are received by multiple microphones in the receiver 3, and the position of the transmitter 2 is estimated based on the time difference in the arrival of the ultrasonic waves at each microphone. The transmitter 2 is installed at positions (each measurement point) within the tunnel where displacement is to be measured, and the tunnel displacement is measured by examining the change in the coordinates of the transmitter 2 over time. Furthermore, the system automatically corrects for changes in sound velocity due to temperature and humidity using information from a temperature/humidity sensor built into the receiver 3, resulting in high measurement accuracy unaffected by changes in temperature and humidity.

The transmitting device 2 shown in Figure 1 is a device that transmits ultrasonic waves. The transmitting device 2 is, for example, an ultrasonic beacon, and intermittently transmits ultrasonic waves at regular intervals. The transmitting device 2 is installed at the locations (each measurement point) where displacement within the tunnel is measured. In other words, the transmitting device 2 is installed at the target locations in conventional laser-based measurements. In this embodiment, since we are assuming measurement of internal displacement in measurement A, the transmitting device 2 is installed at multiple measurement points within the same cross-section of the tunnel. The positions of the transmitting device 2 are, for example, locations where measurements can be taken along "measurement line A" to "measurement line D".

The receiving device 3 is a device that receives ultrasonic waves transmitted by the transmitting device 2, and is installed within the range (acquisition location) of the ultrasonic waves. The receiving device 3 has, for example, legs that can be erected on the ground or a fixing part that is magnetically fixed to a support structure, and can be installed at any location within the tunnel using the legs or fixing part. Receiver 3A has a tripod and is placed on the ground within the tunnel. Receiver 3B has a magnet attached to its base and is fixed to a support structure.

The operating device 4 is a device for operating the receiving device 3, and is operated, for example, by tunnel construction workers. The operating device 4 is, for example, a portable terminal that is easy to carry.
The administrator terminal 5 is installed, for example, in a location away from the receiving device 3 inside the tunnel and is operated by the tunnel construction manager or similar person. The administrator terminal 5 can be, for example, a PC (Personal Computer), a smartphone, or a tablet device. Alternatively, the administrator terminal 5 may be installed in an office outside the tunnel.

The configuration of the transmitting device 2 is shown in Figure 2. Figure 2 is a schematic diagram of the transmitting device 2. The transmitting device 2 of this embodiment is configured to be usable when fitted into a recess formed in the wall surface of a tunnel. The transmitting device 2 mainly comprises a wireless module 21, an ultrasonic speaker (transmitting unit) 22, a battery 23, and a control board 24, and these components are housed in a case 20. The case 20 plays a role in protecting the components it houses and, for example, can be sealed. The battery 23 is rechargeable and can be removed as needed. The transmitting device 2 is housed in a socket 6 embedded in the wall surface. The socket 6 has a space for housing the transmitting device 2 and an opening 6a for mounting the transmitting device 2. For example, a hole is formed in the ground (or support structure) before concrete is sprayed, the socket 6 is embedded, and the opening 6a is sealed using a sealing means such as a lid. Then, after concrete is sprayed, the sealing means is removed and the transmitting device 2 is fixed inside the socket 6. This allows the transmitter 2 to be embedded in the tunnel wall, making it less likely to interfere with blasting or other operations. It is preferable that one or both of the transmitter 2 and the socket 6 be designed to prevent the transmitter 2, housed in the socket 6, from unintentionally popping out (falling). Alternatively, the socket 6, with the transmitter 2 housed inside, could be covered with concrete, leaving the transmitter 2 permanently embedded.

The configuration of the receiving device 3 is shown in Figure 3. Figure 3 is a schematic diagram of the receiving device 3. The receiving device 3 of this embodiment is configured to be movable within a tunnel. The receiving device 3 mainly comprises a receiving unit 31, a wireless module 33, a temperature/humidity sensor 34, a battery 35, and a control board 36. The receiving unit 31 is the part that receives ultrasonic waves emitted from the ultrasonic speaker 22, which is the transmitting unit. The receiving unit 31 has a plurality of microphones 32, and these microphones 32 are installed on the base unit 31a. It is desirable that the plurality of microphones 32 be arranged in an array. In this embodiment, the microphones 32 are arranged at each vertex of a rectangular parallelepiped. Note that the microphones 32 do not have to be arranged in an array, and it is also possible to have separate configurations instead of installing all microphones 32 on a single base unit 31a. The wireless module 33, temperature/humidity sensor 34, battery 35, and control board 36 are housed in a case 30. The case 30 serves to protect the components it houses and, for example, is airtight. The case 30 and the base 31a are connected by a connecting portion 31b. The receiving device 3 preferably has a fixed portion that can be magnetically attached to, for example, legs that can be erected on the ground or to a support structure (see Figure 1). The receiving device 3 is provided with a USB terminal 37 for maintenance and a charging terminal 38 for charging. Communication between the receiving device 3 and the operating device 4 is performed wirelessly using wireless modules 33 and 42, but it may also be done via wired communication. If the administrator terminal 5 has the functions of the operating device 4, the receiving device 3 and the administrator terminal 5 communicate wirelessly (or via wired communication).

The configuration of the operating device 4 is shown in Figure 4. Figure 4 is a schematic diagram of the operating device 4. The operating device 4 according to this embodiment is intended to be operated by a worker holding it with both hands. The case 40 of the operating device 4 has a shape that can be held by both hands on the left and right sides (for example, a plate shape that is long in the left-right direction and has a predetermined thickness). The operating device 4 mainly comprises a display unit 41, a wireless module 42, a battery 43, an operation unit 44, and a control board 45. The operation unit 44 includes a joystick 44a and various operation buttons ("transmitter search" button 44b, "measurement start/stop" button 44c, clear button 44d). The display unit 41 is, for example, a liquid crystal display, and the display unit 41 displays information necessary for performing measurements (for example, information for setting measurement conditions) and measurement result information. The joystick 44a is positioned so that it can be operated with the left hand, and can specify, for example, the up, down, left, and right directions. The "Transmitter Search" button 44b, the "Measurement Start/Stop" button 44c, and the clear button 44d are positioned for operation with the right hand. The wireless module 42 and battery 43 are housed in the case 40. The operating device 4 is provided with a USB terminal 46 for maintenance and a charging terminal 47 for charging. The receiving device 3 and the administrator terminal 5 may also have some or all of the functions of the operating device 4.

Referring to Figure 5 (and Figures 1 to 4 as appropriate), the information exchange within the displacement measurement system 1 will be explained. Figure 5 is a block diagram (including the software configuration) of the displacement measurement system 1 according to this embodiment.

When the transmitting device 2 receives a request from the receiving device 3 to start measurement via the wireless module 21, the transmitting control unit 24a instructs the pulse control unit 24b to transmit a signal. The pulse control unit 24b then transmits a pulse signal to the ultrasonic speaker 22. The ultrasonic speaker 22 then emits an ultrasonic pulse signal into the air, and the emitted ultrasonic pulse signal reaches the receiving device 3.

The receiving device 3 transmits a request to start measurement to the transmitting device 2 via the wireless module 33. In response, it receives ultrasonic pulse signals from the transmitting device 2 using multiple microphones 32, and the received pulse signals are sent to the control unit (position estimation unit) 36a. The control unit 36a also receives temperature and humidity information from the temperature/humidity sensor 34. Based on the ultrasonic pulse signals, temperature information, and humidity information, the control unit 36a estimates the position of the transmitting device 2. Details of the source position estimation will be described later. The receiving device 3 transmits the measurement results (information regarding the position of the transmitting device 2 and information regarding the distance between the two transmitting devices 2, etc.) to the operating device 4 via the wireless module 33.

The operating device 4 receives operator input via the operating unit 44 and transmits operator information (e.g., information about the transmitting device 2 performing the measurement and operation information for starting the measurement) to the receiving device 3 via the wireless module 42. The operating device 4 also receives measurement results (e.g., information about the position of the transmitting device 2 and information about the distance between the two transmitting devices 2) from the receiving device 3 via the wireless module 42, and the control unit 45a displays the received information on the display unit 41. Furthermore, the operating device 4 transmits the measurement results to the administrator terminal 5 via the wireless module 42. This allows the administrator to confirm the measurement results via the administrator terminal 5.

The display unit 41 of the operating device 4 displays, for example, the measurement screen M10. The measurement screen M10 has an ID display area M11, a position display area M12, a distance display area M13, and a group display area M14.
The ID display area M11 displays a list of IDs of transmitting devices 2 that are within communication range of the receiving device 3. The control unit 36a of the receiving device 3 transmits, for example, a wireless signal requesting a communication connection, and the control unit 45a of the operating device 4 displays the ID of the transmitting device 2 that received the response in the ID display area M11.

The position display area M12 displays the position (measurement result) of the transmitter 2, which is within communication range of the receiver 3. The control unit 36a of the receiver 3 determines the position of the transmitter 2 based on the ultrasonic signal emitted from the transmitter 2, and the control unit 45a of the operating device 4 displays the result in the position display area M12. The position of the transmitter 2 is estimated using a position estimation algorithm described later.

The distance display area M13 displays the distance between the two transmitting devices 2. The control unit 36a of the receiving device 3 calculates the distance between the two transmitting devices 2 for all combinations of transmitting devices 2 that are within communication range of the receiving device 3. The distance display area M13 can display a predetermined number of combinations (in Figure 4, three combinations are displayed: "ID(1)-ID(2)", "ID(1)-ID(3)", and "ID(2)-ID(3)"), and the displayed combination can be changed by operating the joystick 44a in the up and down direction.

The group display area M14 displays information about the groups. A group is a collection of measurement results. The control unit 36a of the receiving device 3 registers the results of multiple transmitting devices 2 measured in a single measurement operation as a single group. The group display area M14 displays identification information for a predetermined number of groups (in Figure 4, four groups, "Grp.1" to "Grp.4," are displayed), and a group can be selected by operating the joystick 44a left or right. The selected group is highlighted (in Figure 4, "Grp.1" is selected, and the text "Grp.1" is highlighted by enclosing it in a frame M14a).

Next, with reference to Figure 6, the estimation of the position of the transmitting device 2, which is the source of the ultrasonic waves, will be explained. Figure 6 is a diagram illustrating the definitions used in the position estimation algorithm. In this embodiment, it is assumed that the receiving device 3 performs the position estimation of the transmitting device 2, but other devices (e.g., the receiving device 3 or the administrator terminal 5) may also perform the position estimation of the transmitting device 2. The position estimation function (position estimation unit) is implemented, for example, by program execution processing by the CPU (Central Processing Unit).

As preparation for the measurement, a coordinate system (x,y,z) with its origin near microphone 32 is established. The coordinate system (x,y,z) can be a local coordinate system, and its orientation is arbitrary. Since the arrangement of microphones 32 from the 1st to the Nth (N is the number of microphones, and they are numbered in ascending order according to the order in which the ultrasound arrives) is known, the coordinates P _i (i=1 to N) of microphone 32 are known. In addition, the time difference "(t2 _{to N} ) - _t1 " of the reception times t _i (i=1 to N) at microphones 32 from the 1st to the Nth is known from the speed of sound and the coordinates P _i of microphone 32.
Thus, if the coordinates P _i of the microphone 32 and the reception time difference "(t2 _{to N} ) - _t1 " are known, and for example "N≧4", the coordinates P _P of the ultrasonic speaker 22 can be expressed by an equation. Then, by solving this equation using methods such as Newton's method, least squares method, or nearest four-point method, the coordinates P _P of the ultrasonic speaker 22 can be estimated.
Here, since the speed of sound is affected by temperature and humidity, the temperature/humidity sensor 34 measures the temperature and humidity in real time, and the speed of sound is corrected using the following formula. T is the temperature [°C] and H is the humidity [%].
・Sound speed C=331.4+0.606×T+0.0124×H

The control unit 36a (position estimation unit) of the receiving device 3 filters the sound signals received by each microphone 32 using a bandpass filter to extract only specific frequency components (the ultrasonic components emitted by the transmitting device 2) and remove high-frequency and low-frequency noise. The control unit 36a also detects peaks to determine the starting point of the filtered signal. For example, the control unit 36a sets a threshold for identifying peaks, and defines the timing of the first peak reached after exceeding the threshold as the signal's arrival time.

The control unit 36a uses a position estimation algorithm to estimate the position of the ultrasonic speaker 22 and the distance between the ultrasonic speakers 22, based on the time difference of the peaks of the sound signals received by each microphone 32. The least squares method will be used as an example in the following explanation.

The estimation of the position of the transmitting device 2, as described above, will now be explained with reference to Figure 7. Figure 7 is the program flow of the displacement measurement system 1 according to this embodiment.
Since the arrangement of each microphone 32 is known, a fixed value based on the arrangement is set for the coordinates P _i (x _i , y _i , z _i ) of each microphone 32 (step S11). Also, an appropriate value is set as the initial value P ₀ (x ₀ , y ₀ , z ₀ ) of the coordinates of the ultrasonic speaker 22 (step S12). Next, α _i , β _i , γ _i are calculated from equation (8) above (step S13), and _fi (R _i ) is calculated from equation (3) above (step S14). Next, _Δfi is calculated from equation (7) above (step S15), and the errors Δx, Δy, Δz are calculated from equation (10) above (step S16). If Δx, Δy, Δz are large and there is still an error (step S17), x _p , y _p , z _p are found from equation (5) above and set as new x ₀ , y ₀ , z ₀ (step S18). Then, steps S13 to S16 are performed to calculate new errors Δx, Δy, and Δz. If Δx, Δy, and Δz are sufficiently small (step S17), then x ₀ , y ₀ , and z ₀ become the coordinates of the transmitting device 2 (step S19).
Thus, in the position estimation method of this embodiment, during the iterative calculation, a provisional value for the coordinates _PP (x _p , y _p , z _p ) of the ultrasonic speaker 22 is used as the initial value x ₀ , y ₀ , z ₀ for the next calculation, and the iterative calculation is performed. When the error becomes small, the coordinates x ₀ , y ₀ , z ₀ (or coordinates _PP (x _p , y _p , z _p )) are taken as the true position of the ultrasonic speaker 22, and the iterative calculation is terminated. In other words, the coordinates _PP (x _p , y _p , z _p ) of the ultrasonic speaker 22 obtained in the first calculation are used as the initial value x ₀ , y ₀ , z ₀ for the second calculation, and the coordinates _PP (x _p , y _p , z _p ) of the ultrasonic speaker 22 are newly determined.

The initial values x ₀ , y ₀ , z ₀ (the first values used in the iterative calculation) are not particularly limited and can be any coordinates. It is preferable to set the initial values x ₀ , y ₀ , z ₀ on the extension of the line segment connecting the first microphone 32 ₁ (the first microphone) that first received the ultrasound and the Nth microphone 32 _N (the last microphone) that last received the ultrasound, specifically on the extension on the first microphone 32 ₁ side (for example, a position a few meters away from the first microphone 32 ₁ ). This speeds up convergence and reduces the likelihood of obtaining incorrect solutions (increasing the certainty of finding the correct solution).

<Regarding the measurement operation of the displacement measurement system according to the embodiment>
Referring to Figure 8 (and Figures 1 to 7 as appropriate), an overview of the measurement operation of the displacement measurement system 1 according to the embodiment will be described. Figure 8 is a diagram illustrating the measurement operation of the displacement measurement system 1.
First, the receiving device 3 wirelessly requests the transmitting device ₂₁ (the transmitting device 2 of "ID(1)") to start transmitting (step S1). Upon receiving the request to start transmitting, the transmitting device ₂₁ begins transmitting ultrasound (step S2). The transmitting device ₂₁ intermittently transmits ultrasound at regular intervals, for example. The receiving device 3 receives the ultrasound emitted from the transmitting device ₂₁ with each microphone 32 and calculates the position of the transmitting device ₂₁ from the time difference Δt between the microphones 32 (step S3). Then, the receiving device 3 wirelessly requests the transmitting device ₂₁ to stop transmitting (step S4). Upon receiving the request to stop transmitting, the transmitting device ₂₁ stops transmitting ultrasound.

Next, the receiving device 3 wirelessly requests the transmitting device ₂₂ (the transmitting device 2 of "ID(2)") to start transmitting (step S5), and calculates the position of transmitting device ₂₂ using the same procedure as for transmitting device _21. In this way, the receiving device 3 sequentially calculates the positions of transmitting devices ₂₁ to _2N and determines the position of each measurement point in the tunnel. The receiving device 3 also calculates the distance between each measurement point (between each transmitting device ₂₁ to _2N ) based on the determined positions of each measurement point. Then, after a period of time, the positions of transmitting devices ₂₁ to _2N (the positions of each measurement point) are measured again, and the displacement of the tunnel is measured by comparing it with the previously measured positions and distances.

A more detailed measurement procedure will be described with reference to Figures 9 and 10 (and, as appropriate, Figures 1 through 8). Figures 9 and 10 are diagrams illustrating the measurement procedure of the displacement measurement system 1 according to an embodiment. Note that the measurement procedure described here is merely illustrative.
When a worker activates the receiver 3, the receiver 3 automatically connects to the transmitters 2 within its wireless range K. Here, as shown in Figure 9, assume that transmitters ₂₁ to ₂₈ (transmitters 2 with IDs 1 to 8) are within wireless range K, and the receiver 3 automatically connects to transmitters ₂₁ to _28. The IDs of the connected transmitters 2 are then displayed in the ID display area M11 of the measurement screen M10. As shown in Figure 11(a), the ID display area M11 of the measurement screen M10 displays a list of the IDs of the connected transmitters 2 (IDs 1 to 8). Figure 11 is an example of the measurement screen M10.

Next, the operator presses the "Start/Stop Measurement" button 44c (see Figure 4) to instruct the receiver 3 to start measuring the position of the transmitter 2. The receiver 3 measures the positions of transmitters ₂₁ to ₂₈ within the wireless range K and displays the coordinates of the transmitters 2 in the position display area M12, corresponding to their IDs (see Figure 11(a)). The receiver 3 also calculates the distance between the measured transmitters ₂₁ to ₂₈ and displays the calculated distance in the distance display area M13 (see Figure 11(a)). The receiver 3 then saves the information regarding the measured coordinates of the transmitters 2 and the calculated distance between the transmitters 2 to the selected group. In this case, as shown in Figure 11(a), "Grp.1" is selected, so the information of transmitters ₂₁ to ₂₈ is saved to "Grp.1". This completes the measurement by the receiver 3 at the position shown in Figure 9.

Next, the worker operates the joystick 44a (see Figure 4) to change the selected group to "Grp.2" and moves the receiver 3 in the direction of the tunnel axis (see Figure 10). Then, the worker presses the "Transmitter Search" button 44b (see Figure 4) to instruct the receiver 3 to start searching for transmitters 2. The receiver 3 searches for transmitters 2 within the wireless range K (within the range where the receiver 3 can communicate). Here, as shown in Figure 10, it is assumed that transmitters ₂₅ to ₂₁₂ (transmitters 2 with "ID(5)" to "ID(12)") are within the wireless range K, and the receiver 3 connects to transmitters ₂₅ to _212. The IDs of the connected transmitters 2 are then displayed in the ID display area M11 of the measurement screen M10. As shown in Figure 11(b), the ID display area M11 of the measurement screen M10 displays a list of IDs of the connected transmitting device 2 ("ID(5)" to "ID(12)").

Next, the operator presses the "Start/Stop Measurement" button 44c (see Figure 4) to instruct the receiver 3 to start measuring the position of transmitter 2. The receiver 3 measures the positions of transmitters ₂₅ to ₂₁₂ within the wireless range K and displays the coordinates of transmitter 2 in the position display area M12, corresponding to their IDs (see Figure 11(b)). The receiver 3 also calculates the distance between the measured transmitters ₂₅ to ₂₁₂ and displays the calculated distance in the distance display area M13 (see Figure 11(b)). The receiver 3 then saves the information regarding the measured coordinates of transmitter 2 and the calculated distance between transmitters 2 to the selected group. In this case, as shown in Figure 11(b), "Grp.2" is selected, so the information of transmitters ₂₅ to ₂₁₂ is saved to "Grp.2". This completes the measurement by the receiver 3 at the position shown in Figure 10.

Furthermore, the receiving device 3 preferably has a function to combine the information stored in groups, and can re-register the information stored in two target groups as a single group. The receiving device 3 performs group combination using a positioning algorithm (for example, the ICP (Iterative Closest Point) algorithm or the Singular Value Decomposition (SVD) algorithm). Here, "positioning" refers to the process of estimating the positional relationship between three-dimensional point clouds acquired from different locations and combining the point clouds. For example, the ICP algorithm calculates a rotation matrix or translation matrix to align the second point cloud with the first point cloud. Group combination can be performed when there are three or more common transmitting devices 2 in each of the groups to be combined. Figure 12 shows an image of the information combination process for the information stored in the groups.

As shown in Figure 12(a), the measurement results of "Grp.1" store the measurement results (coordinates, etc.) of transmitter 2 for "ID(1)" to "ID(4)", and the measurement results of "Grp.2" store the measurement results (coordinates, etc.) of transmitter 2 for "ID(1)" to "ID(3)" and "ID(5)". Since "ID(1)" to "ID(3)" are common to both "Grp.1" and "Grp.2", it is possible to combine "Grp.1" and "Grp.2". In Figure 12, we assume that the measurement results of "Grp.2" are aligned with the measurement results of "Grp.1". As shown in Figure 12(b), rotation and translation are performed focusing on the coordinates of "ID(1)" to "ID(3)" included in "Grp.2" to align them with the coordinates of "ID(1)" to "ID(3)" included in "Grp.1". Then, with the coordinates of "ID(1)" to "ID(3)" in "Grp.2" matching those of "ID(1)" to "ID(3)" in "Grp.1," the remaining measurement results are combined. As a result, as shown in Figure 12(c), the measurement results of "Grp.1" and "Grp.2" are combined, and the measurement results of "ID(1)" to "ID(5)" are stored in a single group. The combination function allows for repeated measurements by the transmitter 2 if, for some reason, the measurements could not be taken simultaneously, even though saving them in a single group is desirable.

As described above, the displacement measurement system 1 according to this embodiment eliminates the need to ensure horizontal alignment, thus reducing the time required for installation and verification compared to conventional methods. Therefore, the effort and time required for displacement measurement can be reduced compared to conventional methods. In particular, even if the ultrasonic waves are obstructed by obstacles in the tunnel, only the receiving unit 31 (see Figure 3) needs to be moved, making installation and verification extremely easy.

Furthermore, in this embodiment, the ultrasonic speaker 22 (see Figure 2), which is the transmitting unit, is housed in a socket 6 (see Figure 2) embedded in the inner wall of the tunnel. This makes it less likely for the ultrasonic speaker 22 to interfere with blasting or other operations, and also prevents the ultrasonic speaker 22 from unintentionally coming loose.
Furthermore, in this embodiment, since the receiving unit 31 is installed inside the mountain tunnel by a fixed part that is fixed by magnetic force to a leg that can be erected on the ground or to a support structure, the installation of the receiving unit 31 is easier.

Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented without changing the spirit of the claims.
In this embodiment, the use of the displacement measurement system 1 was illustrated by describing "internal displacement measurement" in "Measurement A". However, the displacement measurement system 1 can also be used in other situations, for example, for "top settlement measurement" in "Measurement A". In that case, absolute coordinates can be provided to the receiving device 3 by some means.
In this embodiment, the operating device 4 and the administrator terminal 5 were described as separate devices. However, for example, the functions of the operating device 4 may be integrated into a PC (Personal Computer), smartphone, or tablet terminal and operated from the administrator terminal 5.

1. Displacement measurement system 2. Transmitter 3. 3A. 3B. Receiver 4. Operating device 5. Administrator terminal 6. Socket 20. Case 21. Wireless module 22. Ultrasonic speaker (transmitter)
23 Battery 24 Control board 30 Case 31 Receiving unit 32 Microphone 33 Wireless module 34 Temperature/humidity sensor 35 Battery 36 Control board 36a Control unit (position estimation unit)
40 Case 41 Display Unit 42 Wireless Module 43 Battery 44 Control Unit 44a Joystick 44b "Transmitter Search" Button 44c "Start/Stop Measurement" Button 44d Clear Button 45 Control Board 45a Control Unit M10 Measurement Screen M11 ID Display Area M12 Position Display Area M13 Distance Display Area M14 Group Display Area K Wireless Range

Claims (7)

A displacement measurement system for mountain tunnels,
A transmitting unit is installed at a measurement point on the inner wall of the tunnel and transmits ultrasonic waves,
A receiving unit receives ultrasonic waves transmitted from the transmitting unit,
The system includes a position estimation unit that estimates the position of the transmitting unit based on the ultrasonic waves received by the receiving unit,
The receiving unit consists of multiple microphones arranged at each vertex of a rectangular parallelepiped .
The position estimation unit estimates the position of the transmitting unit based on the time difference in which the ultrasonic waves reach each microphone.
A displacement measurement system characterized by the following features. The position estimation unit detects the peak of the ultrasonic signal received by each of the microphones, determines the time difference between the peaks, and estimates the position of the transmitter using a position estimation algorithm.
The displacement measurement system according to feature 1. The aforementioned position estimation algorithm uses the least squares method, where the coordinates of the transmitter are represented as the sum of the initial value and the error, and the error is reduced by repeatedly changing the initial value until the error becomes infinitely small, at which point the calculated coordinates of the transmitter are considered the true position.
As the initial value of the aforementioned initial value, the coordinates are set on the extension of the line segment connecting the first microphone that first received the ultrasound and the last microphone that last received it, specifically on the extension on the side of the first microphone.
The displacement measurement system according to claim 2. The transmitting unit is installed at multiple locations within the same cross-section of the mountain tunnel.
The position estimation unit calculates the distance between two points from the position of each transmitting unit.
The displacement measurement system according to feature 1. The displacement measurement system according to claim 1, characterized in that the transmitting unit is housed in a socket embedded in the inner wall of the tunnel. The receiving unit is installed in the mountain tunnel by a fixed part that is fixed by magnetic force to a support structure or by legs that can be erected on the ground.
The displacement measurement system according to feature 1. A method for measuring displacement in mountain tunnels,
A transmission process in which ultrasonic waves are transmitted from a transmitter installed at a measurement point on the inner wall of the tunnel,
A receiving step in which ultrasonic waves transmitted from the transmitting unit are received by the receiving unit,
The system includes a position estimation step for estimating the position of the transmitting unit based on the ultrasonic waves received by the receiving unit,
The receiving unit consists of multiple microphones arranged at each vertex of a rectangular parallelepiped .
In the position estimation step, the position of the transmitting unit is estimated based on the time difference in which the ultrasonic waves reach each microphone.
A displacement measurement method characterized by the following: