Underwater Acoustic Positioning System

Abstract

To measure underwater coordinates of subdevices such as AUV cruising underwater by only two points in total, a first reference point defined as a ship at seat and a second point defined as a buoy towed by the ship.SOLUTION: An undersea acoustic positioning system comprises two reference points of a first reference points and a second reference point that are served references for positioning points and located on the water, and two or more subdevices cruising in water. The subdevices execute: a distance calculation step of calculating a distance between the first reference point and each subdevice, a distance between the respective subdevices, a distance between the second reference point and each subdevice, and a distance between the respective subdevices based on a transmission time when each reference point transmits an acoustic signal and a reception time when each subdevice receives the acoustic signal; and an underwater coordinates determination step of determining underwater coordinates of the subdevice from absolute coordinates received from the respective reference points, a dive depth measured by a depth sensor and an arrival direction of an acoustic signal transmitted from the other subdevice detected by a transducer. Thereby, the undersea acoustic positioning system measures the underwater coordinates of the respective subdevices.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a system for measuring the absolute position of an underwater object such as an AUV (autonomous underwater vehicle) navigating underwater by using an acoustic signal from a reference point installed on the sea surface.

Background Art

[0002] Conventionally, in order to measure the absolute position of an underwater object navigating underwater, it has been impossible to measure the absolute position of the underwater object unless the distances from three or more reference points whose absolute values can be grasped are measured. For example, in Patent Document 1, when there are three offshore ships and one underwater AUV, a watercraft navigating on the sea acquires the position of an underwater vehicle navigating underwater and acquires the position information of the underwater vehicle so as not to lose sight of it. An underwater positioning method is disclosed.

[0003] Also, as a conventional method, a positioning method by the LBL (long baseline) method, that is, a method of grasping the absolute coordinates of the earth (Fig. 22), is known by three reference points installed in the sea. T1, T2, and T3 are reference points provided in the sea, and since the absolute coordinates of the earth are known, the absolute coordinates of the submarine M can be calculated by measuring the distances R1, R2, and R3 from T1, T2, and T3. This method is a so-called triangulation method, and if there are three or more reference points, it becomes possible to uniquely determine the position of the submarine.

[0004] Also, as another conventional method that does not use the surveying method with three reference points, a method using an inertial navigation device is known. This is a method of measuring the current position of an AUV by calculating the displacement from the initial position by time integration while continuously measuring the moving speed and moving direction of the AUV after measuring the initial position of the AUV. Similarly, a method (FIG. 23) is known for measuring the moving speed of a ship by transmitting an acoustic signal (Doppler sonar) from a ship on the sea toward the seabed and measuring the reflected signal, and it can be used as an input to the inertial navigation device described above.

[0005] However, when using three ships as in the invention disclosed in Patent Document 1, the burden on personnel, fuel, etc. required for ship navigation increases. For example, even if one ship and two buoys towed from that ship are used as reference points on the sea, if a third reference point is required, another ship is needed, and the burden on personnel, fuel, etc. required for ship navigation cannot be reduced. On the other hand, if it is possible to have only two reference points on the sea necessary for measuring the position of the underwater slave device, one ship will be sufficient, and substantially, measurement will be possible with only one ship towing the buoy. However, a method of measuring the position of an underwater slave device with only two reference points on the sea has not been known until now.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, the problem to be solved by the present invention is to provide a positioning system capable of measuring the absolute position of an underwater object such as an AUV (hereinafter referred to as a "slave device") diving in the sea with only two reference points, for example, a first reference point which is a ship on the sea and a second reference point which is a buoy towed by that ship. At the same time, by using this slave device as a group of slave devices such as AUVs that operate in a group, and having a plurality of slave devices cooperate to conduct surveys in the sea, the efficiency of underwater exploration and seabed mapping can be improved.

Means for Solving the Problem

[0008] The present invention utilizes two reference points installed on the sea where absolute coordinates can be grasped by a satellite positioning system GNSS (Global Navigation Satellite System) or the like that measures the current position using artificial satellites. A plurality of slave devices such as AUVs that can measure the distance from the reference points by acoustic signals and navigate underwater receive acoustic signals from the reference points on the sea and then exchange another acoustic signal between the slave devices with a certain time delay. Each slave device measures the absolute coordinates in the sea based on the depth information grasped by a depth gauge. It is an underwater acoustic positioning system characterized by this. Specifically, it is as follows.

[0009] The underwater acoustic positioning system according to the present invention comprises two reference points, a first reference point and a second reference point, located on the water surface, which serve as a reference for the positioning location, two or more slave devices that travel underwater, and The first reference point and the second reference point comprise signal transmission means for transmitting an acoustic signal toward the slave device, coordinate measurement means for measuring the absolute coordinates on the earth, transmission time measurement means for measuring the transmission time of the acoustic signal transmitted toward the slave device, measurement information transmission means for transmitting the measured absolute coordinates and transmission time to the slave device, and are provided with The slave device comprises signal transmission means for transmitting an acoustic signal toward another slave device, measurement information reception means for receiving the absolute coordinates and transmission time transmitted from each reference point, a transducer in which two or more elements independently receive an acoustic signal transmitted by another slave device, and can detect the arrival direction of the acoustic signal transmitted from another slave device from the difference in reception times, a depth sensor that measures the diving depth of the slave device by water pressure, Receiving time measurement means for measuring the receiving time of the received acoustic signal, Distance calculation means for calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device based on the received transmission time and the measured receiving time, In a configuration including, A slave device, Based on the transmission time when each reference point transmitted the acoustic signal and, The receiving time when each slave device received the acoustic signal, The distance between the first reference point and each slave device, and the distance between each slave device, and, The distance between the second reference point and each slave device, and the distance between each slave device, and, A distance calculation step for calculating, The absolute coordinates received from each reference point, The diving depth measured by the depth sensor, The arrival direction of the acoustic signal transmitted from another slave device detected by the transducer, An underwater coordinate determination step for determining the underwater coordinates of the slave device from, Executing, and, The distance calculation step described above, For each two or more slave devices, 、 An n×1 matrix of the measured values n of the receiving times when one slave device received acoustic signals 1 to n, Take the left side as, Of the first term, An n×n square matrix, and, An n×1 matrix of the distances between the slave devices, To the product of, Of the second term, An n×1 matrix arranging the delay times of the acoustic signals transmitted by the slave device, The sum of, Is, Make the right side of the equal sign the same as the said left side The relational expression, Under the condition that the inverse matrix exists, For the number of slave devices, By calculating using matrices, The underwater coordinates of each slave device can be measured, Characterized by this.

[0010] In addition, the underwater acoustic positioning system according to the present invention includes two reference points, a first reference point and a second reference point, located above water, which serve as reference points for the positioning location, two or more slave devices traveling underwater, which are connected by wireless communication means, at the first reference point and the second reference point, performing the step of transmitting an acoustic signal toward the slave device, performing the step of measuring the absolute coordinates on the earth, performing the step of measuring the transmission time of the acoustic signal transmitted toward the slave device, performing the step of transmitting the measured absolute coordinates and transmission time to the slave device, causing to execute, at the slave device, performing the step of transmitting an acoustic signal toward another slave device, performing the step of receiving the absolute coordinates and transmission time transmitted from each reference point, performing the step of independently receiving, by two or more elements of the transducer, the acoustic signal transmitted by another slave device, and detecting the arrival direction of the acoustic signal transmitted from another slave device from the difference in reception times, performing the step of measuring the diving depth of the slave device by the depth sensor according to the water pressure, performing the step of measuring the reception time of the received acoustic signal, performing the step of calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device, based on the received transmission time and the measured reception time, causing to execute, further, at the slave device, based on the transmission time when each reference point transmits the acoustic signal and the reception time when each slave device receives the acoustic signal, the distance between the first reference point and each slave device, and the distance between each slave device, and the distance between the second reference point and each slave device, and the distance between each slave device, and performing the step of calculating, the absolute coordinates received from each reference point and The diving depth measured by the depth sensor, and The arrival direction of the acoustic signal transmitted from other slave devices detected by the transducer, and Determining the underwater coordinates of the slave device from In causing to execute For the above The transmission time when each reference point transmitted an acoustic signal, and Based on the reception time when each slave device received the acoustic signal, The distance between the first reference point and each slave device, and the distance between each slave device, and The distance between the second reference point and each slave device, and the distance between each slave device, and The step of calculating For each of two or more slave devices 、 The n×1 matrix of the measured value n of each reception time when one slave device received acoustic signals 1 to n Take the left side as, For the first term, The n×n square matrix, and The n×1 matrix of the distance between slave devices, and To the product of For the second term, The n×1 matrix arranging the delay times of the acoustic signals transmitted by the slave devices The sum of To Make the right side of the equal sign the same as the said left side The relational expression Under the condition that the inverse matrix exists, For the number of slave devices, By calculating using the matrix, The underwater coordinates of each slave device can be measured Characterized by this.

Effect of the Invention

[0011] According to the underwater acoustic positioning system according to the present invention, the number of reference points installed on the sea can be reduced to two, and the burden on personnel, fuel, etc. required for the ship's navigation can be reduced. In addition, as a result of the exchange of a series of acoustic signals, each of the multiple existing slave devices can measure the absolute positions of all the slave devices that make up all the groups, and by being able to grasp each other's positions, it becomes possible to operate as a group.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] FIG. 1 is a diagram showing the configuration of an embodiment of an underwater acoustic positioning system, and shows the positional relationship when using two reference points on the sea and three slave devices in the sea. As the reference points on the sea, two are used: ship 11 (BS1) as the first reference point and buoy 12 (BS2) as the second reference point. The reference points (BS1, BS2) both measure the absolute coordinates on the earth using a satellite positioning system GNSS (Global Navigation Satellite System) or the like that measures the current position using artificial satellites, and transmit the measured absolute coordinates to the slave devices in the sea. Since the buoy 12 (BS2) is towed by the ship 11 (BS1), only one ship is needed to operate the ship. From these two reference points, respective acoustic signals are transmitted to the AUV group 14 composed of three AUVs 13 (UE1, UE2, UE3), which are slave devices in the sea. The respective acoustic signals transmitted from the ship 11 (BS1) and the buoy 12 (BS2) can change the frequency so that it is clear which signal it is, or when they are of the same frequency, they can be transmitted alternately with a time shift from the ship 11 and the buoy 12 so that it is possible to tell which acoustic signal it is.

[0014] Figure 2 is a diagram showing the respective straight-line distances based on the positional relationships of a total of five units: the ship 11 (BS1), the buoy 12 (BS2), and the AUVs 13 (UE1, UE2, UE3). The respective distances from BS1 to UE1, UE2, and UE3 are denoted as r11, r12, and r13, the respective distances from BS2 to UE1, UE2, and UE3 are denoted as r21, r22, and r23, and the respective distances between UE1, UE2, and UE3 are denoted as a, b, and c.

[0015] Figures 3 to 5 are diagrams showing the time required for UE1, UE2, and UE3 to receive the acoustic signal transmitted from BS1 and the plurality of acoustic signals transmitted from each of UE1, UE2, and UE3, for each received signal. Therefore, the horizontal axis of the figure represents the time axis. Originally, the number obtained by dividing the distance by the propagation speed was the time required for each acoustic signal to be received by the slave device. However, in the figure, for simplicity, the time it takes for the acoustic signal to reach each of UE1, UE2, and UE3 from BS1 is represented by the same "r11", "r12", "r13" as the respective distances from BS1 to UE1, UE2, and UE3, in the sense of time corresponding to the distance. Similarly, the time it takes for a plurality of acoustic signals transmitted from each of UE1, UE2, and UE3 to reach each of UE1, UE2, and UE3 is represented by the same "a", "b", "c" as the distances between each of UE1, UE2, and UE3. Also, the upward arrows in the figure indicate that the timing is when the "time of receiving the signal" is measured. In addition, UE1, UE2, and UE3 are set to transmit with a delay of a predetermined time so that the acoustic signals transmitted from each do not overlap, and the delay times are represented by "o1", "o2", "o3",... Although not shown in FIGS. 3 to 5, the time it takes for the acoustic signal to reach each of UE1, UE2, and UE3 from BS2 can be represented by the same "r21", "r22", "r23" as the respective distances from BS2 to UE1, UE2, and UE3, as shown in FIG. 7.

[0016] By measuring the times of the leading positions (at the time of reception) of the signal A received by UE1, UE2, and UE3 with reference to the time of the leading position (at the time of transmission) of the signal A transmitted by BS1, r11, r12, and r13 (all times) can be calculated. By multiplying these times by the propagation speed, the respective distances of r11, r12, and r13 can be calculated. In calculating this distance, it is necessary for the times of BS1 and the slave devices UE1, UE2, and UE3 to be completely synchronized, or for UE1, UE2, and UE3 to know the transmission time of the acoustic signal by BS1. Therefore, the reference points (BS1, BS2) measure the transmission times of the acoustic signals transmitted to the slave devices (UE1, UE2, UE3) and transmit the transmission times to the slave devices (UE1, UE2, UE3). As a result, the slave device can know the transmission time of the acoustic signal transmitted by the reference point, and can completely synchronize the time between the reference point and the slave device. Therefore, in this embodiment, the description will be made on the premise that the times of each reference point BS1 (BS2) and each slave device UE1, UE2, UE3 are completely synchronized.

[0017] Based on FIG. 3, the measurement methods of the distances r11, r12, r13, a, b, c will be described. The locations with horizontal lines drawn within the square frames indicate the acoustic signals transmitted from each of BS1, UE1, UE2, UE3. For example, BS1 transmits an acoustic signal A for timing detection at the time indicated by A, and then each of UE1, UE2, UE3 transmits acoustic signals C, D, E, F, G, H, J, K, L for data communication at the times indicated by C, D, E, F, G, H, J, K, L. Hereinafter, the acoustic signals transmitted at each time will be represented as signal A, signal C, signal D, etc. Also, the locations with vertical lines drawn within the square frames in the figure indicate that each of UE1, UE2, UE3 has received an acoustic signal.

[0018] Since the acoustic signal A for timing detection in FIG. 3 is a signal for timing detection, it is a longer signal compared to other signals, and it is shown as an "OFDM packet" on the premise of using the orthogonal frequency division multiplexing OFDM method.

[0019] After receiving signal A, UE1 transmits signal C with a delay of a predetermined time (delay time o1). Similarly, after receiving signal A, UE2 and UE3 also transmit signal D and signal E respectively with a delay of a predetermined time (delay times o2, o3). FIG. 3 is an embodiment in the case where the distances between the AUVs (UE1 to UE3) are short (located close to each other). Therefore, UE2 measures the "time when signal C was received" at the timing indicated by the second upward arrow from the left. It can be seen that signal C was received by UE2 and UE3 immediately after being transmitted by UE1.

[0020] The signal A transmitted from BS1 propagates through the underwater distance r11 and reaches UE1. Therefore, the time it takes for the signal A transmitted from BS1 to be received by UE1 is the time it takes to propagate through the distance r11, which is r11 (time). UE1 transmits signal C after a predetermined delay time o1 so as not to overlap with the acoustic signals transmitted from UE2 and UE3. The signal C transmitted from UE1 propagates through the underwater distance a and reaches UE2. Therefore, the time it takes for the signal C transmitted from UE1 to be received by UE2 is the time it takes to propagate through the distance a, which is a (time). Therefore, by measuring the "time when signal C was received" by UE2, the sum of r11 (time) + delay time o1 + a (time) can be obtained. Similarly, by measuring the "time when signal C was received" by UE3, the sum of r11 (time) + delay time o1 + c (time) can be obtained. And by each of UE1 and UE3 measuring the "time when signal D was received", UE1 can obtain the sum of r12 (time) + delay time o2 + a (time), and UE3 can obtain the sum of r12 (time) + delay time o2 + b (time).

[0021] UE2 is transmitting signal D, and the delay time o2 is set to be longer than the delay time o1. This is to prevent the acoustic signals transmitted and received by each slave device from colliding. After that, UE1 transmits signals H and K at timings delayed by the preset delay times o6 and o8 from the times when signals D and E were received, respectively. Similarly, UE2 and UE3 also transmit each signal at a timing delayed by the delay time shown in the figure.

[0022] Through the above process, UE1 to UE3 each measure the seven "times when the signal was received" indicated by the upward arrows in the figure. Since there are six distances to be measured, namely r11, r12, r13, a, b, and c, in the embodiment of FIG. 3, seven "times when the signal was received" are measured. However, if the measured values of six appropriate "times when the signal was received" are used, these six distances can be obtained. That is, when each UE can measure the reception times of six signals, as described above, by measuring the times of the leading positions (at reception) of signal A received by UE1, UE2, and UE3 based on the time of the leading position (at transmission) of signal A transmitted by BS1, r11, r12, and r13 (all of which are times) can be calculated. By multiplying these times by the propagation speed, the distances r11, r12, r13, a, b, and c can be calculated. Similarly, the respective distances r21, r22, and r23 from the second reference point BS2 to UE1, UE2, and UE3, and the distances a, b, and c between UE1 to UE3 can also be obtained by measuring the reception times of the signals transmitted from BS2 and the reception times of the six signals received by each UE.

[0023] FIG. 4 shows an embodiment in which the distances between the AUVs (UE1 to UE3) are long (located at positions slightly separated from each other) compared to the embodiment of FIG. 3. UE1, UE2, and UE3 transmit signals C, D, and E respectively at timings delayed by the times of delay times o1, o2, and o3. UE1 receives signals D and E, UE2 receives signals C and E, and UE3 receives signals C and D. In this way, from UE1 to UE3, acoustic signals are transmitted and received with each other, and by measuring the reception times of each signal, the distances r11, r12, r13, a, b, and c can be calculated in the same manner as described in the embodiment of FIG. 3.

[0024] FIG. 5 shows an embodiment in which, compared with the embodiment of FIG. 3, the AUVs (UE1 to UE3) transmit signals C, D, E, signals H, F, G, and signals K, L, J at timings delayed by the same delay time o1. When UE1 is close to UE2 and UE3 respectively, UE1 will receive signals D and E transmitted from UE2 and UE3 at almost the same timing. However, even if signals D and E are received at the same timing, by separating the reception times of their leading positions (the upward arrows in the figure), overlapping reception of signals becomes possible. In particular, in this embodiment, when the delay time o1 for transmitting signals C, D, and E is the same, the total time required for transmitting and receiving signals among the AUVs (UE1 to UE3) can be shortened, and the absolute positions of the slave devices can be measured earlier.

[0025] FIG. 6 shows, using matrices, the relational expressions for obtaining distances r11, r12, r13, a, b, and c based on the reception times measured in the embodiments of FIGS. 3 to 5. Taking the measured values of the reception times of each signal by each AUV (UE1, UE2, UE3), which are slave devices in the sea, as the left side, the product of the relational matrix and the parameter vector r11, r12, r13, a, b, c regarding the distances between the slave devices is shown in the first term on the right side, and the sum with the vector regarding the transmission and reception delay is shown in the second term on the right side. Also, the determinant in the first row is the expression regarding UE1. UE1_A, UE1_D, UE1_E, UE1_F, UE1_G, and UE1_J on the left side mean the measured values of the reception times of signals A, D, E, F, G, and J received by UE1 with respect to the reference time in FIGS. 3 to 5.

[0026] In the embodiments of FIGS. 3 to 5, the signals for measuring the reception times include a total of 7 signals including "L" in addition to A, D, E, F, G, and J. Among these, if the measured values of the reception times of 6 appropriate signals are known, the distances r11, r12, r13, a, b, and c can be obtained. Therefore, an example using the measured values of the reception times of 6 signals A, D, E, F, G, and J is shown in the determinant of FIG. 6. By substituting 0 (zero) or the pre-determined delay time values up to the delay times o1 to o7 into the right side of this determinant, the distances r11, r12, r13, a, b, and c can be obtained. Similarly, the second determinant is an equation for UE2, and the third determinant is an equation for UE3. By solving each determinant, the distances r11, r12, r13, a, b, and c can be obtained.

[0027] That is, for each of two or more slave devices, the product of the n×1 matrix of the measured values n of each reception time when the single slave device received the acoustic signals 1 to n described on the left side, the n×n square matrix of the first term, and the n×1 matrix of the distances between the slave devices, and the sum of the n×1 matrix of the delay times of the acoustic signals transmitted by the slave devices of the second term, are shown in the relational expressions. Under the condition that the inverse matrix exists, by calculating using matrices for the number of slave devices, based on the transmission time when each reference point transmitted the acoustic signal and the reception time when each slave device received the acoustic signal, the distances between the first reference point and each slave device, and the distances between each slave device, the distances between the second reference point and each slave device, and the distances between each slave device can be calculated.

[0028] Similarly, by transmitting signals from BS2 as well and measuring the reception time of each signal at each AUV (UE1, UE2, UE3) that receives this, the distances r21, r22, r23, a, b, and c can be obtained. Figure 7 shows each signal transmitted and received by two reference points (BS1, BS2) on the sea and each AUV which is a slave device in the sea, and the arrival time of the acoustic signal. For example, if BS1 and BS2 repeatedly transmit acoustic signals at 1-second intervals, each UE can calculate the values of r11, r12, r13, r21, r22, r23 every 2 seconds and the values of a, b, c every 1 second. The locations with horizontal lines drawn within the square frames indicate the transmitted signals, and the locations with vertical lines drawn within the square frames indicate the received signals.

[0029] FIG. 8 shows an example of a signal transmitted from a reference point BS1 on the sea to each AUV (UE1, UE2, UE3), which is a slave device in the sea, and an SL signal transmitted and received between the AUVs (UE1, UE2, UE3). Since the signal transmitted from the reference point BS1 on the sea to each AUV (UE1, UE2, UE3), which is a slave device in the sea, is a signal transmitted in the sea direction, it is represented as a DL (downlink) signal. The DL signal in FIG. 8 is an example of an embodiment. The signal Agc shown at the far left means auto - gain control, and it means a signal for adjusting the amplification gain of the amplifier at the signal input part on the receiving side to an appropriate value. Similar to the embodiments shown in FIGS. 3 - 5, signal A means a signal for timing detection used for distance measurement. After the transmission of signal A (to the right of signal A in the figure), in the downlink, it shows a communication signal for sending coordinate information indicating the position of the reference point BS1 on the sea, time information, or commands for the AUV. Since each signal is premised on using the orthogonal frequency - division multiplexing (OFDM) method, it is shown in OFDM symbols. Generally, for OFDM signals, a signal called a guard interval or a cyclic prefix is often inserted between signals. Therefore, signal G is inserted between OFDM signals for illustration. Also, as signals transmitted and received between AUVs (UE1 - UE3), in the embodiments of FIGS. 3 - 5, nine signals C, D, E, F, G, H, J, K, L are used. The signal transmitted and received between these AUVs (UE1 - UE3) is represented as an SL (side - link) signal. In FIG. 8, signal C among the SL signals is shown.

[0030] FIG. 9 shows a waveform of an embodiment of the DL signal, which is shown as a complex signal in the base - band signal processing part. The DL signal is a signal with a changing frequency and is called a chirp signal. A ship on the sea has large vertical height fluctuations due to waves and the like, and is also affected by the Doppler effect. Therefore, as an example, a chirp signal that is easy to detect even when there is a frequency displacement is shown. FIGS. 10 and 11 show waveforms using a signal called the Zadoff-Chu sequence in the SL signal. In particular, it is a waveform of a signal assuming the embodiment of FIG. 5, and a sequence with good separation detection characteristics is used so that different SL signals can be separated and detected at the time of reception. Since different signals can be created according to prime values in the Zadoff-Chu sequence, FIG. 10 shows an example of the waveform of a signal corresponding to the prime value 23, and FIG. 11 shows an example of the waveform of a signal corresponding to the prime value 67. Each waveform in FIGS. 9 to 11 means that the upper part is the real part and the lower part is the imaginary part.

[0031] From the above embodiments, a method for calculating the distances r11, r12, r13, r21, r22, r23, a, b, c based on the arrival (reception) times of acoustic signals transmitted and received by two reference points (BS1, BS2) on the sea and each AUV (UE1, UE2, UE3) which is a slave device in the sea has been described. However, even if the absolute coordinates on the earth of the ship 11 (BS1) which is the first reference point on the sea and the buoy 12 (BS2) which is the second reference point on the sea, and further the distances r11, r12, r13, r21, r22, r23, a, b, c can be calculated, this alone cannot obtain the absolute coordinates on the earth of each AUV.

[0032] FIG. 12 is a schematic diagram showing the system configuration of signal processing of AUVs (UE1, UE2, UE3) which are slave devices in the sea. The AUV is equipped with a transducer 21 and can detect the arrival direction of an acoustic signal arriving at the time of side link reception, and is also equipped with a depth sensor 22. The AUV needs to receive the DL signal, transmit and receive the SL signal, and transmit a UL (uplink) signal for transmitting a monitor signal or the like to the BS. However, the transducer 21 for transmitting and receiving an acoustic signal includes two elements A and B. When transmitting an acoustic signal, either one of the elements A or B may be used for transmission. However, when receiving, the two elements A and B each independently receive the signal, and the arrival direction of the received signal is estimated based on the difference in their reception times. Note that the number of elements of the transducer 21 can also be two or more. If there are at least two or more, the arrival direction of the signal can be estimated. The depth sensor 22 measures the diving depth of the AUV based on the water pressure. Based on the estimation of this arrival direction and the information on the diving depth, the distances from two absolute coordinates (the first and second reference points) on the earth and the distance between the AUVs can be measured.

[0033] Figure 13 is a diagram showing the position of one AUV (UE1) assumed based on the distance between a ship (BS1) and a buoy (BS2) at sea. The position of one AUV (UE1) assumed from the distances r11 and r21 from the ship (BS1) and the buoy (BS2) at sea is represented by the locus 81. And UE1 can identify the constant-depth surface 82 by obtaining depth information from the depth gauge. Thereby, if UE1 knows the distances from BS1 and BS2, it can identify that its current position is either UE1a or UE1b.

[0034] Figure 14 is a diagram showing, in the same way as Figure 13, the situation of the positions of three AUVs (UE1, UE2, UE3) assumed based on the distance between a ship (BS1) and a buoy (BS2) as seen from the sea surface towards the sea. Each of UE1, UE2, and UE3 is on the constant-depth surface 82 in the same way as in Figure 13. Therefore, if the distances a, b, and c between the AUVs (UE1, UE2, UE3) and the distances from BS1 and BS2 can be calculated, the positions of the three AUVs (UE1, UE2, UE3) can be determined to be in either of the two triangles on the left and right in Figure 14.

[0035] After identifying up to this point, by using the detection results of the arrival directions of the acoustic signals detected by each AUV, it is possible to determine whether the positions of the three AUVs (UE1, UE2, UE3) are in the positions of either of the two triangles on the left and right. This determination finally makes it possible to uniquely identify the positions of the three AUVs (UE1, UE2, UE3) in the sea. For example, when the upward direction in FIG. 14 is the traveling direction of each AUV, if it is found that the acoustic signal received by UE1 from UE2 is sent from the right direction in FIG. 14, it can be determined that the current locations of UE1, UE2, and UE3 are at the positions of the triangle consisting of UE1a, UE2a, and UE3a. On the other hand, if it is found that the acoustic signal received by UE1 from UE2 is sent from the left direction in FIG. 14, it can be determined that the current locations of UE1, UE2, and UE3 are at the positions of the triangle consisting of UE1b, UE2b, and UE3b.

[0036] By the above method, one ship as the first reference point installed on the sea and a buoy towed from the ship as the second reference point installed on the sea are used. With only these two reference points, each AUV can independently identify the absolute positions of three AUVs submerging in the sea. At the same time, when a group of slave devices such as a plurality of AUVs submerging in the sea cooperate to conduct an investigation in the sea, since the current positions of those groups of slave devices can be identified, the efficiency of underwater exploration and the creation of seabed maps can be improved.

[0037] In the same way as the above description, FIG. 15 shows an example of identifying the current positions of three groups of AUVs 14 submerging in the sea by using three groups of three AUVs 14 with respect to the reference points BS1 and BS2 on the sea. For example, different Zadoff-Chu sequences are used so that the SL signals of each group of AUVs 14 do not interfere with the SL signals of other groups of AUVs 14. In addition, since each group of AUVs 14 can share the information of the reference points BS1 and BS2 on the sea, the cost of the system can be reduced. In the embodiment of FIG. 15, the number of UEs constituting one AUV group 14 is three, but it can be two as shown in FIG. 16 or four as shown in FIG. 17.

[0038] FIG. 18 is a diagram showing the arrival times of acoustic signals transmitted and received between the offshore reference device (BS1) and two underwater slave devices in the embodiment of FIG. 16, similar to FIGS. 3 to 5 and FIG. 7. The locations with horizontal lines drawn within the square frames indicate that acoustic signals have been transmitted from BS1, and the locations with vertical lines drawn within the square frames indicate that acoustic signals from BS1 have been received. And FIG. 19 shows a determinant for obtaining distances from the transmission and reception of acoustic signals in the embodiment of FIG. 18.

[0039] Also, FIG. 20 is a diagram showing the arrival times of acoustic signals transmitted and received between the offshore reference device (BS1) and four underwater slave devices in the embodiment of FIG. 17, similar to FIGS. 3 to 5 and FIG. 7. The locations with horizontal lines drawn within the square frames indicate that acoustic signals have been transmitted from BS1, and the locations with vertical lines drawn within the square frames indicate that acoustic signals from BS1 have been received. In the embodiment of FIG. 17, the distances between the UEs are six, namely a, b, c, d, e, f. By increasing the signals transmitted and received between each UE, similar to the determinant for obtaining distances from the transmission and reception of acoustic signals shown in FIG. 21, the current positions of the four UEs constituting the AUV group 14 can be calculated. Note that in the determinant of FIG. 21, the transmission signals at the locations with horizontal lines drawn within the square frames of FIG. 20 are not used in the calculation formula. This is because the existence of an inverse matrix in the 10x10 square matrix of the matrix equation shown in FIG. 21 is a condition for the matrix equation to be solvable, and thus they are appropriately selected to ensure the existence of the inverse matrix. The determinant of FIG. 21 has a 10X10 coefficient matrix. Since an inverse matrix exists, the distances r11, r12, r13, r14, a, b, c, d, e, f can be obtained.

[0040] The transmission and reception of acoustic signals, the measurement of time and distance, and the determination of underwater coordinates based on the above embodiments can be realized by the computers mounted on the ship (BS1) as the first reference point and the buoy (BS2) as the second reference point, and the computers mounted on the AUVs submerged in water. By causing each computer to execute each procedure according to the execution procedure of the program shown in the flowchart of FIG. 24, each AUV can independently determine its underwater coordinates. In addition to the underwater coordinates, each AUV can independently obtain longitude, latitude, and depth in real time. These data, including the underwater coordinates, can be transmitted to a server on the sea or on the ground, or can be integrated into the storage device of each AUV and used as data for controlling the automatic navigation of the AUV. As a result, it is also possible for a plurality of AUVs to explore the seabed topography and create a seabed topographic map based on the integrated measured values of longitude, latitude, and depth.

[0041] In addition, since all AUVs constituting a plurality of AUV groups can independently obtain underwater coordinates (latitude, longitude) and depth, it is possible to perform automatic navigation of the AUVs while transmitting and receiving each other's position information and maintaining a certain distance from each other. In general, in order to control automatic navigation, it is necessary to measure the position, speed, depth, direction, etc. of the AUV in navigation using sensors. In particular, in the present invention, since the absolute position (underwater coordinates) of the AUV can be measured at regular time intervals according to the procedure of the above-described embodiment, the speed of each AUV can be calculated from the time change of the absolute position (underwater coordinates), and a special speed sensor or the like can also be used in combination. The traveling direction can be measured by something like an azimuth magnet using geomagnetism. Since various information from sensors includes noise, the noise is reduced and synthesized so as to output a value close to the true value, and the state (position, traveling direction, traveling speed) of the AUV is grasped. While comparing the actual position information of the AUV with the pre-programmed navigation route, based on the information of each AUV collected at regular time intervals, the rudder, power, depth adjustment, etc. of the AUV are repeatedly adjusted so as to navigate along the pre-set route, enabling the control of autonomous navigation.

[0042] Based on the above concept, by using multiple AUV groups consisting of multiple UEs, which are more underwater slave devices, the efficiency of underwater exploration and seabed mapping can be improved. Even in this case, since the number of reference points installed at sea can be limited to two, the burden on personnel, fuel, etc. required for the ship's submergence can be reduced, achieving cost reduction.

Explanation of Signs

[0043] 11 Ship (the first reference point at sea) 12 Buoy (the second reference point at sea) 13 AUV (underwater slave device) 14 AUV group (underwater slave device) 21 Transducer 22 Depth gauge 81 Locus of the current position of the AUV (UE1) assumed from the distances r11 and r21 from the ship, which is the first reference point at sea, and the buoy, which is the second reference point at sea 82 Iso-depth surface

Claims

1. Two reference points, a first reference point and a second reference point, located on the water surface, which serve as references for the positioning points, Two or more slave devices traveling in water, Composed of, The first reference point and the second reference point are, Signal transmission means for transmitting an acoustic signal toward the slave device, Coordinate measurement means for measuring the absolute coordinates on the earth, Transmission time measurement means for measuring the transmission time of the acoustic signal transmitted toward the slave device, Measurement information transmission means for transmitting the measured absolute coordinates and transmission time to the slave device, Equipped with, The slave device is, Signal transmission means for transmitting an acoustic signal toward other slave devices, Measurement information reception means for receiving the absolute coordinates and transmission time transmitted from each reference point, A transducer in which two or more elements independently receive the acoustic signal transmitted by other slave devices and can detect the arrival direction of the acoustic signal transmitted from other slave devices from the difference in reception times, A depth sensor for measuring the diving depth of the slave device by water pressure, Reception time measurement means for measuring the reception time of the received acoustic signal, Distance calculation means for calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device based on the received transmission time and the measured reception time, In a configuration equipped with, The slave device is, Based on the transmission time when each reference point transmits an acoustic signal and, Based on the reception time when each slave device receives the acoustic signal, The distance between the first reference point and each slave device, and the distance between each slave device, The distance between the second reference point and each slave device, and the distance between each slave device, A distance calculation step for calculating, The absolute coordinates received from each reference point, The diving depth measured by the depth sensor, The arrival direction of the acoustic signal transmitted from other slave devices detected by the transducer, An underwater coordinate determination step for determining the underwater coordinates of the slave device from, By executing, The underwater coordinates of each slave device can be measured A marine acoustic positioning system characterized by this.

2. Two reference points, a first reference point and a second reference point, located on the water surface, which serve as references for the positioning points, Two or more slave devices traveling in water, Composed of, The first reference point and the second reference point are, Signal transmission means for transmitting an acoustic signal toward the slave device, Coordinate measurement means for measuring the absolute coordinates on the earth, Transmission time measurement means for measuring the transmission time of the acoustic signal transmitted toward the slave device, Measurement information transmission means for transmitting the measured absolute coordinates and transmission time to the slave device, Equipped with, The slave device is, Signal transmission means for transmitting an acoustic signal toward other slave devices, Measurement information receiving means for receiving the absolute coordinates and transmission times transmitted from each reference point; Two or more elements independently receive an acoustic signal transmitted by another slave device, and from the difference in reception times, a transducer capable of detecting the arrival direction of the acoustic signal transmitted from another slave device; A depth sensor that measures the diving depth of the slave device by water pressure; Reception time measuring means for measuring the reception time of the received acoustic signal; Distance calculation means for calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device based on the received transmission time and the measured reception time; In a configuration having; The slave device Based on the transmission time when each reference point transmits an acoustic signal and Based on the reception time when each slave device receives an acoustic signal, The distance between the first reference point and each slave device, and the distance between each slave device, and The distance between the second reference point and each slave device, and the distance between each slave device, and A distance calculation step for calculating; The absolute coordinates received from each reference point, The diving depth measured by the depth sensor, The arrival direction of the acoustic signal transmitted from another slave device detected by the transducer, An underwater coordinate determination step for determining the underwater coordinates of the slave device from; While executing, The distance calculation step described above For each of two or more slave devices, Taking as the left side the n×1 matrix of the measured values n of each reception time when one slave device receives acoustic signals 1 to n, In the first term, The n×n square matrix, The n×1 matrix of the distances between the slave devices, To the product of In the second term, The n×1 matrix arranging the delay times of the acoustic signals transmitted by the slave devices Of the sum A relational expression with the left side equal to the right side of the equal sign, Under the condition that the inverse matrix exists, For the number of slave devices, By calculating using matrices, The underwater coordinates of each slave device can be measured An underwater acoustic positioning system characterized by that.

3. The acoustic signal transmitted from the first reference point towards the slave device Is a chirp signal whose frequency changes at a constant speed with time The underwater acoustic positioning system according to any one of claims 1 or 2, characterized by that.

4. The acoustic signal transmitted between the slave devices Is a Zadoff-Chu sequence corresponding to different prime number parameters for each slave device The underwater acoustic positioning system according to any one of claims 1 to 3, characterized by that.

5. Two or more slave devices traveling underwater Consist of a group of slave devices consisting of the same number of slave devices, For one group of slave devices, Two reference points, the first reference point and the second reference point located above the water, are in one set each Are configured The underwater acoustic positioning system according to any one of claims 1 to 4, characterized in that...

6. Two reference points, a first reference point and a second reference point, located on the water surface, which serve as references for the positioning location, Two or more slave devices traveling underwater, Are connected by wireless communication means, At the first reference point and the second reference point, Transmitting an acoustic signal towards the slave device, Measuring the absolute coordinates on the earth, Measuring the transmission time of the acoustic signal transmitted towards the slave device, Transmitting the measured absolute coordinates and transmission time to the slave device, Causing to execute, At the slave device, Transmitting an acoustic signal towards another slave device, Receiving the absolute coordinates and transmission time transmitted from each reference point, Two or more elements of the transducer independently receive the acoustic signal transmitted by another slave device, and detect the arrival direction of the acoustic signal transmitted from another slave device from the difference in reception times, The depth sensor measures the diving depth of the slave device due to water pressure, Measuring the reception time of the received acoustic signal, Calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device based on the received transmission time and the measured reception time, Causing to execute, Furthermore, at the slave device, Based on the transmission time when each reference point transmitted the acoustic signal and the reception time when each slave device received the acoustic signal, Based on, The distance between the first reference point and each slave device, and the distance between each slave device, The distance between the second reference point and each slave device, and the distance between each slave device, Calculating, The absolute coordinates received from each reference point, The diving depth measured by the depth sensor, The arrival direction of the acoustic signal transmitted from another slave device detected by the transducer, Determining the underwater coordinates of the slave device from, By causing to execute, The underwater coordinates of each slave device can be measured An underwater acoustic positioning program, characterized in that...

7. Two reference points, a first reference point and a second reference point, located on the water surface, which serve as references for the positioning location, Two or more slave devices traveling underwater, Are connected by wireless communication means, At the first reference point and the second reference point, Transmitting an acoustic signal towards the slave device, Measuring the absolute coordinates on the earth, Measuring the transmission time of the acoustic signal transmitted towards the slave device, Transmitting the measured absolute coordinates and transmission time to the slave device, Causing to execute, At the slave device, The step of transmitting an acoustic signal to other slave devices; The step of receiving the absolute coordinates and transmission time transmitted from each reference point; The step in which two or more elements of the transducer independently receive the acoustic signals transmitted by other slave devices, and detect the arrival direction of the acoustic signals transmitted from other slave devices from the difference in reception times; The step in which the depth sensor measures the submerged depth of the slave device based on the water pressure; The step of measuring the reception time of the received acoustic signal; The step of calculating the respective distances between the first reference point and each slave device, between the second reference point and each slave device, and between each slave device based on the received transmission time and the measured reception time; To execute; Furthermore, for the slave device, Based on the transmission time when each reference point transmitted an acoustic signal and the reception time when each slave device received the acoustic signal, the distance between the first reference point and each slave device, and the distance between each slave device, and the distance between the second reference point and each slave device, and the distance between each slave device, and the step of calculating; the absolute coordinates received from each reference point, the submerged depth measured by the depth sensor, the arrival direction of the acoustic signal transmitted from other slave devices detected by the transducer, and the step of determining the underwater coordinates of the slave device from; When executing, Regarding the above Based on the transmission time when each reference point transmitted an acoustic signal and the reception time when each slave device received the acoustic signal, the distance between the first reference point and each slave device, and the distance between each slave device, and the distance between the second reference point and each slave device, and the distance between each slave device, and the step of calculating is For each two or more slave devices, Taking the n×1 matrix of the measured values n of each reception time when one slave device received acoustic signals 1 to n as the left side, For the first term, the n×n square matrix and the n×1 matrix of the distance between slave devices, and the product of For the second term, the n×1 matrix arranging the delay times of the acoustic signals transmitted by the slave devices the sum of As a relational expression with the left side equal to the right side of the equal sign, Under the condition that the inverse matrix exists, For the number of slave devices, By calculating using matrices, the underwater coordinates of each slave device can be measured An underwater acoustic positioning program characterized by this.

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