Underwater acoustic positioning system, transmitting device, and receiving device

Abstract

Provided is an underwater acoustic positioning system capable of reducing time variations that occur until a signal generation timing at which an ultrasonic signal is generated. In the underwater acoustic positioning system, a transmitting device generates a sampled transmission signal on the basis of a first timing signal. The transmission signal is then converted into an ultrasonic signal, and the ultrasonic signal is transmitted. The first timing signal is corrected so as to be synchronized with a reference signal. A receiving device calculates a propagation delay time by calculating a time difference between a sampling time of an output signal from an ultrasonic signal receiving unit and a cycle timing of a second timing signal, and calculates an underwater position having unknown coordinates on the basis of the propagation delay time. The second timing signal is corrected so as to be synchronized with the reference signal.

Description

Underwater acoustic positioning system, transmitting device and receiving device

[0001] The technology according to the present disclosure (the present technology) relates to an underwater acoustic positioning system, and a transmitting device and a receiving device provided in the underwater acoustic positioning system.

[0002] BACKGROUND ART Conventionally, the underwater positions of heavy machinery such as backhoes and bulldozers that perform work underwater or on the bottom of water, and structures such as immersed tunnels, have been measured.

[0003] For example, Patent Document 1 discloses an underwater acoustic positioning system that includes a transmitter installed at known coordinates, such as a breakwater, a receiver installed on a backhoe, a signal generation unit connected to the transmitter, a D / A (digital / analog) converter, an amplifier, and a GNSS antenna, and a control device that estimates the coordinates of the backhoe based on the propagation time of sound waves emitted from the transmitter to the receiver at predetermined intervals.

[0004] However, in the system described in Patent Document 1, the sound waves emitted from the transmitter and reaching the receiver include not only sound waves that travel straight from the transmitter to the receiver (direct waves), but also sound waves that are reflected by the water surface, the bottom of the water, or a structure (reflected waves), and sound waves that are diffracted by the bottom of the water or a structure (diffracted waves).

[0005] Therefore, even if one were to individually calculate the impulse responses of the propagation path between the transmitter and receiver and use the peak arrival time as the direct wave arrival time to estimate the coordinates of the transmitter, the sound waves received by the receiver are subject to interference from direct waves, reflected waves, and diffracted waves. Therefore, simply calculating the peak arrival time of each impulse response individually would not be enough to accurately calculate the arrival time of the direct wave, and there is a risk of large errors or missing measurements in the receiver position estimation results.

[0006] Patent Document 2 discloses an underwater acoustic positioning system that uses a database in which the time window during which sound waves generated from a transmitter reach a receiver is stored in advance for each region, calculates the dot product of the time window and the impulse response of the sound wave propagation path from the transmitter to the receiver, excludes unintended sound waves contained in the impulse response, and compares the magnitude of the total energy of the time window-applied impulse response for each region to estimate the region in which a transmitter or receiver located at unknown coordinates is located.

[0007] JP 2018-204970 A JP 2023-020001 A

[0008] In an underwater acoustic positioning system, when an ultrasonic signal is generated using a GNSS timing signal as a trigger, it is necessary to reduce the time variance from the GNSS timing signal input timing to the signal generation timing in order to reduce positioning variance. However, when ultrasonic signal generation is performed by SW (Software) processing, if the GNSS timing signal is used as an ultrasonic signal generation trigger by interrupt processing, variance occurs in the SW execution timing after the interrupt, which causes positioning variance.

[0009] In the systems described in Patent Document 1 and Patent Document 2, time synchronization is performed between the transmitter and receiver, but there is no mention of reducing the time variation from the GNSS timing signal input timing to the signal generation timing.

[0010] The present disclosure has been made in consideration of these circumstances, and aims to provide an underwater acoustic positioning system, a transmitting device, and a receiving device that can reduce the time variability that occurs until the signal generation timing for generating an ultrasonic signal.

[0011] One aspect of the present disclosure is an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, wherein the transmitting device includes a first timing generating unit that generates a first timing signal, a transmitting signal generating unit that generates a sampled transmitting signal based on the first timing signal generated by the first timing generating unit, an ultrasonic signal transmitting unit that converts the transmitting signal generated by the transmitting signal generating unit into the ultrasonic signal and transmits the ultrasonic signal toward the receiving device, a first reference signal receiving unit that receives a first reference signal at a constant period, and a receiving unit that receives the first timing signal by the first reference signal receiving unit. and a first correction unit that corrects the second timing signal so that it is synchronized with the first reference signal received by the second reference signal receiving unit, and the receiving device comprises an ultrasonic signal receiving unit that receives the ultrasonic signal, a second reference signal receiving unit that receives a second reference signal at a constant period, a second timing generating unit that generates a second timing signal, a position calculation unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of the output signal of the ultrasonic signal receiving unit and the period timing of the second timing signal, and calculates an underwater position of the unknown coordinates based on the propagation delay time, and a second correction unit that corrects the second timing signal so that it is synchronized with the second reference signal received by the second reference signal receiving unit.

[0012] Another aspect of the present disclosure is a transmitting device of an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater, and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, the transmitting device comprising: a timing generating unit that generates a timing signal; a transmitting signal generating unit that generates a sampled transmitting signal based on the timing signal generated by the timing generating unit; an ultrasonic signal transmitting unit that converts the transmitting signal generated by the transmitting signal generating unit into the ultrasonic signal and transmits the ultrasonic signal toward the receiving device; a reference signal receiving unit that receives a reference signal at a constant period; and a correcting unit that corrects the timing signal so that it is synchronized with the reference signal received by the reference signal receiving unit.

[0013] Furthermore, another aspect of the present disclosure is a receiving device of an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater, and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, the receiving device comprising: an ultrasonic signal receiving unit that receives the ultrasonic signal transmitted from the transmitting device; a reference signal receiving unit that receives a reference signal at a constant period; a timing generating unit that generates a timing signal; a position calculating unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of the output signal of the ultrasonic signal receiving unit and the period timing of the timing signal, and calculates the underwater position of the unknown coordinate based on the propagation delay time; and a correction unit that corrects the timing signal so that it is synchronized with the reference signal received by the reference signal receiving unit.

[0014] FIG. 1 is a schematic diagram showing the configuration of an underwater acoustic positioning system according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram showing how an ultrasonic signal is propagated from a transmitter to a receiver in the first embodiment of the present disclosure. FIG. 3 is a block diagram showing a specific configuration of a signal generation timing control circuit shown in FIG. 3. FIG. 5 is a block diagram showing a specific configuration of a signal generation timing control circuit shown in FIG. 5. FIG. 6 is a schematic diagram showing the positional relationship between a transmitter and a receiver in the first embodiment of the present disclosure. FIG. 7 is a block diagram showing the configuration of a transmitter according to a second embodiment of the present disclosure. FIG. 8 is a block diagram showing the configuration of a receiver according to a second embodiment of the present disclosure. FIG. 9 is a block diagram showing the configuration of a receiver according to a third embodiment of the present disclosure.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings referred to in the following description, the same or similar parts are denoted by the same or similar reference numerals, and duplicate descriptions will be omitted.

[0016] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0017] 1 is a schematic diagram showing the configuration of an underwater acoustic positioning system 1. The underwater acoustic positioning system 1 uses a Global Navigation Satellite System (GNSS) to measure the underwater position (three-dimensional position) of a backhoe 2 lowered to the seabed. As the GNSS used to measure the underwater position of the backhoe 2, in addition to the Global Positioning System (GPS), for example, a system that dynamically switches between positioning using a Global Navigation Satellite System (GLONASS) and positioning using GPS, or a system that measures position using a combination of GPS and GLONASS, can be considered.

[0018] The backhoe 2 is operated by an operator on board and moves along the seabed to perform excavation and other operations. Power for the backhoe 2 is supplied from the support barge 3 via a power line (not shown).

[0019] The underwater acoustic positioning system 1 comprises a transmitter 10 (an example of a transmitting device) and a receiver 20 (an example of a receiving device). The transmitter 10 is a pinger that autonomously emits ultrasonic waves at regular intervals toward the receiver 20. The receiver 20 is attached to a stake (not shown) fixed to the seabed. The position of the receiver 20 is determined in advance and remains constant even while the backhoe 2 is working.

[0020] The transmitter 10 is mounted on the backhoe 2. The transmitter 10 is connected to the control device 30 via a first repeater 21 mounted on the backhoe 2 and a second repeater 22 mounted on the support barge 3. Specifically, the transmitter 10, the first repeater 21, the second repeater 22 and the control device 30 are wired together via power and signal lines.

[0021] A transmitting GNSS antenna 60 is connected to the transmitter 10. The transmitting GNSS antenna 60 is installed on the support barge 3. The transmitter 10 and the transmitting GNSS antenna 60 are connected by wire via a power supply / signal line 61. The transmitting GNSS antenna 60 receives GNSS signals from the GNSS satellite 50. The GNSS signals received by the transmitting GNSS antenna 60 are received by a GNSS receiver, which will be described later. The GNSS receiver transmits a 1 pps signal (an example of a first reference signal) containing timing information at predetermined intervals (for example, every second) to the transmitter 10 via the power supply / signal line 61. The GNSS signal contains time information from a highly accurate atomic clock installed on the GNSS satellite 50.

[0022] A water pressure gauge 23 is preferably provided near the transmitter 10. The water pressure gauge 23 transmits its measurement value to the control device 30 via the first repeater 21 and the second repeater 22. This makes it possible to measure the water depth near the transmitter 10. Note that reference numeral 24 in Fig. 1 denotes a compass that detects the orientation of the backhoe 2 and transmits the detection result to the control device 30 via the first repeater 21 and the second repeater 22.

[0023] The operation of the underwater acoustic positioning system 1 is controlled by a control device 30. The control device 30 is, for example, a personal computer mounted on the support barge 3. The control device 30 has an input section and an output section (not shown), and an operator on board the support barge 3 can operate the control device 30 and check the underwater position of the backhoe 2.

[0024] A receiving GNSS antenna 40 is connected to the receiver 20. The receiving GNSS antenna 40 is installed on a breakwater, but it may also be installed on the sea surface. The receiver 20 and the receiving GNSS antenna 40 are connected by a signal line 41. The receiving GNSS antenna 40 receives GNSS signals from GNSS satellites 50. The GNSS signals received by the receiving GNSS antenna 40 are received by a GNSS receiver, which will be described later. The GNSS receiver transmits a 1 pps signal (an example of a second reference signal) containing timing information at predetermined intervals (for example, every second) to the receiver 20 via the signal line 41.

[0025] (Installation Positions of Transmitter 10 and Receiver 20) FIG. 2 is a schematic diagram showing how an ultrasonic signal propagates from the transmitter 10 to the receiver 20 underwater. In the underwater acoustic positioning system 1, an ultrasonic signal propagates between the transmitter 10 and the receiver 20, and the receiver 20 identifies the underwater position of the transmitter 10. The receiver 20 is equipped with three hydrophones 211, 212, and 213 (an example of an ultrasonic signal receiving unit). The ultrasonic signal propagates through the water at approximately 1500 m / s before reaching the hydrophones 211, 212, and 213 of the receiver 20. The three hydrophones 211, 212, and 213 are located at known coordinates (Xr1, Yr1, Zr1), (Xr2, Yr2, Zr2), and (Xr3, Yr3, Zr3), respectively.

[0026] 3 is a block diagram showing the configuration of the transmitter 10. The transmitter 10 includes a signal generation timing control circuit 110, a signal generator 120 (an example of a transmission signal generating unit), a D / A (digital / analog) converter 130, a transducer 140 (an example of an ultrasonic signal transmitting unit), and a GNSS receiver 150 (an example of a first reference signal receiving unit).

[0027] The signal generation timing control circuit 110 generates a signal generation timing signal (an example of a first timing signal). The signal generation timing control circuit 110 also includes a correction unit (an example of a first correction unit) that corrects the signal generation timing signal so as to synchronize with the 1 pps signal output from the GNSS receiver 150.

[0028] The signal generator 120 generates a sampled digital transmission signal based on the signal generation timing signal generated by the signal generation timing control circuit 110. The digital transmission signal is converted into an analog transmission signal by the D / A converter 130 and transmitted into the water from the transducer 140 as an ultrasonic signal.

[0029] 4 is a block diagram showing a specific configuration of the signal generation timing control circuit 110. The signal generation timing control circuit 110 includes an oscillator (NCO) 111 (an example of a first timing generating unit), a signal generator 112 (an example of a reference signal generating unit), a D / A converter 113, an A / D converter 114, an A / D converter 115, a phase difference detector 116 (an example of a phase comparing unit), a filter 117 (an example of a control unit), and an integrator 118 (an example of a control unit).

[0030] Oscillator 111 generates a signal generation timing signal. The signal generation timing signal is output to signal generator 120 and also to signal generator 112. Based on the signal generation timing signal, signal generator 112 generates an unmodulated carrier signal (an example of a reference signal) having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal. The unmodulated carrier signal is converted from a digital signal to an analog signal by D / A converter 113 to become a signal generation timing signal, and is then converted from an analog signal to a digital signal by A / D converter 114 to be output to one input terminal of phase difference detector 116.

[0031] The other input terminal of the phase difference detector 116 receives the 1 pps signal received by the GNSS receiver 150 and converted into a digital waveform by the A / D converter 115. The phase difference detector 116 compares the digitized signal generation timing signal with the digitized 1 pps signal, and outputs a digital value (an example of a phase difference) corresponding to the amount of deviation between the two. After a filter 117 removes, for example, noise components, the digital value is output to an integrator 118.

[0032] The integrator 118 cumulatively adds the input digital values ​​and outputs the cumulatively added value as a frequency control value to the oscillator 111. Then, feedback control is performed so that the frequency is lowered if the phase of the signal generation timing signal is ahead of the 1 pps signal, and conversely, the frequency is raised if it is behind, so that the signal generation timing signal becomes synchronized in phase with the 1 pps signal.

[0033] 5 is a block diagram showing the configuration of the receiver 20. The receiver 20 includes a signal generation timing control circuit 220, an A / D converter 230 (an example of an ultrasonic signal receiving unit), a position estimator 240 (an example of a position calculation unit), a GNSS receiver 250 (an example of a second reference signal receiving unit), and a signal generator 260 (an example of a receiving-side transmission signal generating unit).

[0034] The signal generation timing control circuit 220 generates a signal generation timing signal (an example of a second timing signal) in the same manner as the signal generation timing control circuit 110. The signal generation timing control circuit 220 also includes a correction unit (an example of a second correction unit) that corrects the signal generation timing signal so as to synchronize with the 1 pps signal output from the GNSS receiver 250.

[0035] The ultrasonic signals received by each hydrophone 211, 212, 213 are amplified by an amplifier not shown, then converted into digital electrical signals (referred to as received signals) by an A / D converter 230 and output to the position estimator 240, respectively.

[0036] The signal generation timing signal generated by the signal generation timing control circuit 220 is output to the signal generator 260. Based on the signal generation timing signal, the signal generator 260 generates a transmission signal replica equivalent to the digital transmission signal of the transmitter 10. The transmission signal replica is output to the position estimator 240.

[0037] The position estimator 240 calculates the propagation delay times t1, t2, and t3 from the transmitter 10 to each hydrophone 211, 212, and 213 by calculating the time difference between the sampling time of the received signal from each hydrophone 211, 212, and 213 and the sampling time of the transmitted signal replica, and calculates the underwater position of the transmitter 10, which is an unknown coordinate, based on the propagation delay times t1, t2, and t3.

[0038] 6 is a block diagram showing a specific configuration of the signal generation timing control circuit 220. The signal generation timing control circuit 220 includes an oscillator (NCO) 221 (an example of a second timing generating unit), a signal generator 222 (an example of a reference signal generating unit), a D / A converter 223, an A / D converter 224, an A / D converter 225, a phase difference detector 226 (an example of a phase comparing unit), a filter 227 (an example of a control unit), and an integrator 228 (an example of a control unit).

[0039] Oscillator 221 generates a signal generation timing signal. The signal generation timing signal is output to signal generator 260 and also to signal generator 222. Based on the signal generation timing signal, signal generator 222 generates an unmodulated carrier signal (an example of a reference signal) having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal. The unmodulated carrier signal is converted from a digital signal to an analog signal by D / A converter 223 to become a signal generation timing signal, and is converted from an analog signal to a digital signal by A / D converter 224 to be output to one input terminal of phase difference detector 226.

[0040] The other input terminal of the phase difference detector 226 receives the 1 pps signal received by the GNSS receiver 250 and converted into a digital waveform by the A / D converter 225. The phase difference detector 226 compares the digitized signal generation timing signal with the digitized 1 pps signal, and outputs a digital value (an example of a phase difference) corresponding to the amount of deviation between the two. After a filter 227 removes, for example, noise components, the digital value is output to the integrator 228.

[0041] The integrator 228 cumulatively adds the input digital values ​​and outputs the cumulatively added value as a frequency control value to the oscillator 221. Then, feedback control is performed so that the frequency is lowered if the phase of the signal generation timing signal is ahead of the 1 pps signal, and conversely, the frequency is raised if it is behind, so that the signal generation timing signal becomes synchronized in phase with the 1 pps signal.

[0042] (Position Calculation Operation) Next, a procedure for estimating the underwater position of the transmitter 10 will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing the positional relationship between the transmitter 10 and the receiver 20 in the first embodiment of the present disclosure. The position estimator 240 calculates propagation delay times t1, t2, and t3 for each of the hydrophones 211, 212, and 213. Next, the propagation delay times t1, t2, and t3 are multiplied by the sound speed c of the ultrasonic signal in water to obtain distances l1, l2, and l3 from the transmitter 10 to each of the hydrophones 211, 212, and 213.

[0043] Then, the position estimator 240 solves the simultaneous equations shown in Equation 1 using the least squares method or the like based on the coordinates and distances l1, l2, l3 of each hydrophone 211, 212, 213, and identifies the underwater position of the transmitter 10, i.e., the unknown coordinates (Xt, Yt, Zt).

[0044]

[0045] <Effects of the First Embodiment> As described above, according to the first embodiment, an ultrasonic signal with little timing variation can be generated by correcting the signal generation timing signal that generates a transmission signal in the transmitter 10 so that it is synchronized with a 1 pps signal having a constant period. Also, by correcting the signal generation timing signal that is equivalent to the signal generation timing signal that generates a transmission signal in the receiver 20 so that it is synchronized with the 1 pps signal, the underwater position of unknown coordinates, i.e., the underwater position of the transmitter 10, can be accurately calculated using the ultrasonic signal with little timing variation.

[0046] Furthermore, according to the first embodiment, by generating a transmission signal replica at the same timing as the transmitter 10 in the receiver 20, while in conventional technology it was necessary to synchronize the time between the transmitter 10 and the receiver 20, the propagation delay time can be measured from the relative time difference between the received signal of each hydrophone 211, 212, 213 and the transmission signal replica, so time synchronization between the transmitter 10 and the receiver 20 is no longer necessary.

[0047] In the above-described underwater acoustic positioning system 1, the underwater position of the transmitter 10 is calculated as unknown coordinates, but conversely, the underwater position of the receiver 20 may be calculated as unknown coordinates. Furthermore, in the above-described underwater acoustic positioning system 1, an example has been described in which the transmitter 10 is mounted on the backhoe 2 and the receiver 20 is installed on the breakwater, but it is also possible to implement an example in which the receiver 20 is mounted on the backhoe 2 and the transmitter 10 is installed on the breakwater.

[0048] Second Embodiment Fig. 8 is a block diagram showing the configuration of a transmitter 10A according to a second embodiment of the present disclosure. In Fig. 8, the same parts as those in Fig. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0049] The transmitter 10A includes an interpolator 160, a D / A converter 170, and an A / D converter 180. The interpolator 160 interpolates transmission data (Tx data) stored in, for example, a ROM based on a signal generation timing signal generated by the oscillator 111 to generate a digital transmission signal, and also generates carrier data (Cerrier Data) stored in, for example, a ROM as an unmodulated carrier signal. The transmission data has predetermined sampling points, and the interpolator 160 interpolates the sampling points based on the signal generation timing signal into the transmission data.

[0050] The D / A converter 170 converts the input digital transmission signal into an analog transmission signal and outputs it to the transducer 140, and also converts the unmodulated carrier signal into an analog signal and outputs it to the A / D converter 180 as a signal generation timing signal.

[0051] The A / D converter 180 converts the signal generation timing signal into a digital signal and outputs it to the phase difference detector 116 , and also converts the 1 pps signal into a digital waveform and outputs it to the phase difference detector 116 .

[0052] 9 is a block diagram showing the configuration of a receiver 20A according to the second embodiment of the present disclosure. In Fig. 9, the same parts as those in Fig. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0053] The receiver 20A includes an interpolator 270 and an A / D converter 280. The interpolator 270 generates a transmission signal replica by interpolating transmission data (Tx data) stored in, for example, a ROM based on a signal generation timing signal generated by an oscillator 221, and also generates carrier data stored in, for example, a ROM as an unmodulated carrier signal.

[0054] The A / D converter 280 converts the signal generation timing signal output from the D / A converter 223 into a digital signal and outputs it to the phase difference detector 226 , and also converts the 1 pps signal into a digital waveform and outputs it to the phase difference detector 226 .

[0055] <Operational Effects of the Second Embodiment> As described above, according to the second embodiment, in the transmitter 10A, for example, the transmit data (Tx data) stored in ROM is interpolated by the interpolator 160 to generate a digital transmit signal, and the carrier data stored in ROM is generated as an unmodulated carrier signal by the interpolator 160, thereby providing the same operational effects as in the first embodiment. Furthermore, in the receiver 20A, for example, the transmit data (Tx data) stored in ROM is interpolated by the interpolator 270 to generate a transmit signal replica, and the carrier data stored in ROM is generated as an unmodulated carrier signal by the interpolator 160, thereby providing the same operational effects as in the first embodiment.

[0056] Third Embodiment Fig. 10 is a block diagram showing the configuration of a receiver 20B according to a third embodiment of the present disclosure. In Fig. 10, the same parts as those in Fig. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0057] The receiver 20B includes four A / D converters 231, 232, 233, and 234. That is, the ultrasonic signal received by the hydrophone 211 is amplified by an amplifier (not shown), converted into a received signal by the A / D converter 231, and output to the position estimator 240. The ultrasonic signal received by the hydrophone 212 is amplified by an amplifier (not shown), converted into a received signal by the A / D converter 232, and output to the position estimator 240. The ultrasonic signal received by the hydrophone 213 is amplified by an amplifier (not shown), converted into a received signal by the A / D converter 233, and output to the position estimator 240. The signal generation timing signal output from the D / A converter 223 is converted into a digital signal by the A / D converter 233 and output to the position estimator 240. This allows the position estimator 240 to perform more accurate position estimation based on the three received signals, the signal generation timing signal, and the transmitted signal replica.

[0058] <Effects of the Third Embodiment> As described above, according to the third embodiment, the receiver 20B can perform accurate position estimation using the signal generation timing signal in addition to the three received signals and the transmitted signal replica. Note that in the third embodiment, the three received signals and the signal generation timing signal may be input to the position estimator 240. In this case, the position estimator 240 calculates the propagation delay time by calculating the time difference between the sampling time of each received signal and the cycle timing of the signal generation timing signal, and calculates the underwater position of the unknown coordinates based on the propagation delay time.

[0059] <Other Embodiments> As described above, the present technology has been described using the first to third embodiments and a modified example of the third embodiment. However, the descriptions and drawings that form part of this disclosure should not be understood to limit the present technology. Upon understanding the gist of the technical content disclosed in the first to third embodiments, it will be clear to those skilled in the art that various alternative embodiments, examples, and operational techniques can be included in the present technology. Furthermore, the configurations disclosed in the first to third embodiments and the modified example of the third embodiment can be appropriately combined within a range that does not cause contradictions. For example, configurations disclosed in multiple different embodiments may be combined, or configurations disclosed in multiple different modified examples of the same embodiment may be combined.

[0060] The present disclosure can also be configured as follows. (1) An underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, wherein the transmitting device comprises: a first timing generating unit that generates a first timing signal; a transmitting signal generating unit that generates a sampled transmitting signal based on the first timing signal generated by the first timing generating unit; an ultrasonic signal transmitting unit that converts the transmitting signal generated by the transmitting signal generating unit into the ultrasonic signal and transmits the ultrasonic signal towards the receiving device; a first reference signal receiving unit that receives a first reference signal at a constant period; and a first correcting unit that corrects the first timing signal so as to be synchronized with the first reference signal received by the first reference signal receiving unit; and wherein the receiving device comprises: an ultrasonic signal receiving unit that receives the ultrasonic signal; a second reference signal receiving unit that receives a second reference signal at a constant period; and a second timing generating unit that generates a second timing signal. an underwater acoustic positioning system comprising: a position calculation unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of the output signal of the ultrasonic signal receiving unit and the period timing of the second timing signal, and calculates an underwater position of the unknown coordinates based on the propagation delay time; and a second correction unit that corrects the second timing signal so as to synchronize with the second reference signal received by the second reference signal receiving unit. (2) The underwater acoustic positioning system described in (1) above, wherein the first reference signal receiving unit and the second reference signal receiving unit receive reference signals transmitted from a satellite of a satellite positioning system. (3) The underwater acoustic positioning system described in (1) above, wherein the receiving device further comprises a receiving-side transmission signal generating unit that generates a signal equivalent to the transmission signal based on the second timing signal, and the position calculation unit calculates the propagation delay time based on the output signal of the ultrasonic signal receiving unit and the output signal of the receiving-side transmission signal generating unit.(4) The underwater acoustic positioning system according to (1), wherein the first correction unit comprises: a reference signal generating unit that generates, based on the first timing signal, a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal; a phase comparing unit that compares the reference signal with the first reference signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the first timing generating unit based on the phase difference. (5) The underwater acoustic positioning system according to (1), wherein the second correction unit comprises: a reference signal generating unit that generates, based on the second timing signal, a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal; a phase comparing unit that compares the reference signal with the second reference signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the second timing generating unit based on the phase difference. (6) The underwater acoustic positioning system according to (1), wherein the transmission signal generating unit of the transmitting device generates a transmission signal based on the first timing signal, and generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the first correction unit. (7) The underwater acoustic positioning system according to (3), wherein the receiving-side transmission signal generating unit of the receiving device generates a transmission signal based on the second timing signal, and generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the second correction unit.(8) A transmitting device of an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, comprising: a timing generating unit that generates a timing signal, a transmitting signal generating unit that generates a sampled transmitting signal based on the timing signal generated from the timing generating unit, an ultrasonic signal transmitting unit that converts the transmitting signal generated by the transmitting signal generating unit into the ultrasonic signal and transmits the ultrasonic signal toward the receiving device, a reference signal receiving unit that receives a reference signal at a constant period, and a correcting unit that corrects the timing signal so as to synchronize with the reference signal received by the reference signal receiving unit. (9) The transmitting device according to (8) above, in which the reference signal receiving unit receives a reference signal sent from a satellite of a satellite positioning system. (10) The transmitting device according to (8), wherein the correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal based on the timing signal, a phase comparing unit that compares the reference signal with the standard signal to determine a phase difference corresponding to the amount of deviation between the two, and a control unit that controls an oscillation frequency of the timing generating unit based on the phase difference. (11) The transmitting device according to (8), wherein the transmission signal generating unit generates a transmission signal based on the timing signal, and generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the correction unit.(12) A receiving device of an underwater acoustic positioning system in which one of a transmitting device that transmits ultrasonic signals and a receiving device that receives the ultrasonic signals is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, comprising: an ultrasonic signal receiving unit that receives the ultrasonic signals transmitted from the transmitting device, a reference signal receiving unit that receives a reference signal of a constant period, a timing generating unit that generates a timing signal, a position calculating unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of an output signal of the ultrasonic signal receiving unit and the period timing of the timing signal, and calculates an underwater position of the unknown coordinate based on the propagation delay time, and a correcting unit that corrects the timing signal so as to synchronize with the reference signal received by the reference signal receiving unit. (13) The receiving device according to (12) above, in which the reference signal receiving unit receives a reference signal transmitted from a satellite of a satellite positioning system. (14) The receiving device according to (12), further comprising a transmission signal generating unit that generates a signal equivalent to the transmission signal of the transmitting device based on the timing signal, wherein the position calculation unit calculates the propagation delay time based on the output signal of the ultrasonic signal receiving unit and the output signal of the transmission signal generating unit. (15) The receiving device according to (12), wherein the correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal based on the timing signal, a phase comparator that compares the reference signal with the standard signal to determine a phase difference corresponding to the amount of deviation between the two, and a control unit that controls an oscillation frequency of the timing generating unit based on the phase difference. (16) The receiving device according to (14), wherein the transmission signal generating unit generates a signal equivalent to the transmission signal of the transmitting device based on the timing signal, and generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the correction unit.

[0061] 1 Underwater acoustic positioning system 2 Backhoe 3 Support barge 10, 10A Transmitter 20, 20A, 20B Receiver 21 First repeater 22 Second repeater 23 Water pressure gauge 30 Control device 40 Receiving GNSS antenna 41 Signal line 50 GNSS satellite 60 Transmitting GNSS antenna 61 Power supply / signal line 110, 220 Signal generation timing control circuit 111, 221 Oscillator (NCO) 112 Signal generator 113, 130, 170, 223 D / A converter 114, 115, 180, 224, 225, 230, 231, 232, 233, 234, 280 A / D converter 116, 226 Phase difference detector 117, 227 Filter 118, 228 Integrator 120, 260 Signal generator 140 Transducer 150 GNSS receiver 160, 270 Interpolator 211, 212, 213 Hydrophone 222 Signal generator 240 Position estimator 250 GNSS receiver

Claims

1. An underwater acoustic positioning system in which one of a transmitting device for transmitting an ultrasonic signal and a receiving device for receiving the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, wherein the transmitting device comprises: a first timing generating unit for generating a first timing signal; a transmitting signal generating unit for generating a sampled transmitting signal based on the first timing signal generated by the first timing generating unit; an ultrasonic signal transmitting unit for converting the transmitting signal generated by the transmitting signal generating unit into the ultrasonic signal and transmitting the ultrasonic signal towards the receiving device; a first reference signal receiving unit for receiving a first reference signal of a constant period; and a first correction unit for correcting the first timing signal so as to be synchronized with the first reference signal received by the first reference signal receiving unit; and wherein the receiving device comprises: an ultrasonic signal receiving unit for receiving the ultrasonic signal; a second reference signal receiving unit for receiving a second reference signal of a constant period; and a second timing generating unit for generating a second timing signal. an underwater acoustic positioning system comprising: a position calculation unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of the output signal of the ultrasonic signal receiving unit and the period timing of the second timing signal, and calculates an underwater position of the unknown coordinates based on the propagation delay time; and a second correction unit that corrects the second timing signal so as to be synchronized with the second reference signal received by the second reference signal receiving unit.

2. The underwater acoustic positioning system according to claim 1, wherein the first reference signal receiving unit and the second reference signal receiving unit receive reference signals transmitted from satellites of a satellite positioning system.

3. The underwater acoustic positioning system of claim 1, wherein the receiving device further comprises a receiving-side transmission signal generating unit that generates a signal equivalent to the transmission signal based on the second timing signal, and the position calculation unit calculates the propagation delay time based on the output signal of the ultrasonic signal receiving unit and the output signal of the receiving-side transmission signal generating unit.

4. The underwater acoustic positioning system of claim 1, wherein the first correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal based on the first timing signal; a phase comparing unit that compares the reference signal with the first standard signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the first timing generating unit based on the phase difference.

5. The underwater acoustic positioning system of claim 1, wherein the second correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency of n / m (m and n are integers) of the carrier frequency of the transmission signal based on the second timing signal; a phase comparing unit that compares the reference signal with the second reference signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the second timing generating unit based on the phase difference.

6. An underwater acoustic positioning system as described in claim 1, wherein the transmission signal generating section of the transmitting device generates a transmission signal based on the first timing signal, generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the first correction section.

7. An underwater acoustic positioning system as described in claim 3, wherein the receiving side transmission signal generating section of the receiving device generates a transmission signal based on the second timing signal, generates a reference signal having a frequency n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the second correction section.

8. A transmitting device of an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, the transmitting device comprising: a timing generating unit that generates a timing signal; a transmitting signal generating unit that generates a sampled transmitting signal based on the timing signal generated by the timing generating unit; an ultrasonic signal transmitting unit that converts the transmitting signal generated by the transmitting signal generating unit into an ultrasonic signal and transmits the ultrasonic signal towards the receiving device; a reference signal receiving unit that receives a reference signal at a constant period; and a correcting unit that corrects the timing signal so as to be synchronized with the reference signal received by the reference signal receiving unit.

9. The transmitting device according to claim 8, wherein said reference signal receiving section receives a reference signal transmitted from a satellite of a satellite positioning system.

10. The transmitting device according to claim 8, wherein the correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency of n / m (m and n are integers) of the carrier frequency of the transmission signal based on the timing signal; a phase comparing unit that compares the reference signal with the standard signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the timing generating unit based on the phase difference.

11. The transmitting device according to claim 8, wherein the transmission signal generating unit generates a transmission signal based on the timing signal, generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the correction unit.

12. A receiving device of an underwater acoustic positioning system in which one of a transmitting device that transmits an ultrasonic signal and a receiving device that receives the ultrasonic signal is installed at a known coordinate underwater and the other is installed at an unknown coordinate underwater, and the unknown coordinate is positioned, the receiving device comprising: an ultrasonic signal receiving unit that receives the ultrasonic signal transmitted from the transmitting device; a reference signal receiving unit that receives a reference signal of a constant period; a timing generating unit that generates a timing signal; a position calculation unit that calculates a propagation delay time from the transmitting device to the receiving device by calculating the time difference between the sampling time of the output signal of the ultrasonic signal receiving unit and the period timing of the timing signal, and calculates the underwater position of the unknown coordinate based on the propagation delay time; and a correction unit that corrects the timing signal so as to be synchronized with the reference signal received by the reference signal receiving unit.

13. The receiving device according to claim 12, wherein the reference signal receiving section receives a reference signal transmitted from a satellite of a satellite positioning system.

14. The receiving device described in claim 12, further comprising a transmission signal generating unit that generates a signal equivalent to the transmission signal of the transmitting device based on the timing signal, and the position calculation unit calculates the propagation delay time based on the output signal of the ultrasonic signal receiving unit and the output signal of the transmission signal generating unit.

15. The receiving device described in claim 12, wherein the correction unit comprises: a reference signal generating unit that generates a reference signal having a frequency that is n / m (m and n are integers) of the carrier frequency of the transmission signal based on the timing signal; a phase comparing unit that compares the reference signal with the standard signal to determine a phase difference corresponding to the amount of deviation between the two; and a control unit that controls the oscillation frequency of the timing generating unit based on the phase difference.

16. The receiving device described in claim 14, wherein the transmission signal generating unit generates a signal equivalent to the transmission signal of the transmitting device based on the timing signal, generates a reference signal having a frequency n / m (m and n are integers) of the carrier frequency of the transmission signal, and outputs the reference signal to the correction unit.

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