JP7625191B2 - Underwater positioning system and underwater positioning device - Google Patents

Description

The present invention relates to an underwater positioning system and an underwater positioning device that detects the three-dimensional position of an object to be positioned underwater.

The present invention relates to a method for detecting the three-dimensional position of an object to be measured underwater, where underwater includes the sea, rivers, lakes, and the like, and the object to be measured includes artificial objects such as underwater robots known as ROVs (Remotely Operated Vehicles). Methods for performing underwater positioning using acoustics such as ultrasound include the long base line (LBL) method, the short base line (SBL) method, and the super short base line (SSBL) method. There are various methods for specifying a three-dimensional position using an underwater acoustic positioning system using the SSBL method, and at least three pieces of information are required: distance, angle of arrival, and depth. The SSBL method refers to a method in which the receiver interval (baseline) is approximately the wavelength of the sound wave. Note that the object to be measured requires one transmitter to emit a target sound.

Conventional underwater positioning systems/devices include those shown in the following Patent Documents 1 to 5. Patent Document 1 discloses a method for determining the direction, identification information, and depth of multiple objects to be positioned. Patent Document 2 discloses an apparatus that receives signals transmitted from the objects to be positioned using at least three receiving devices and processes the signals. Patent Document 3 discloses a configuration in which signals from multiple transmitters installed underwater are received by a receiver of the object to be positioned, GPS (GNSS) antennas are connected to the receiver and transmitter, and the position of the object to be positioned is calculated based on the propagation time of sound waves emitted from the multiple transmitters to the receiver in response to the GNSS signals received by the transmitting GNSS antenna. Patent Document 4 discloses a configuration in which multiple signals transmitted from multiple transmitters are received by multiple receivers and data processed to reduce variation in the positioning results and improve accuracy. Patent Document 5 discloses a configuration in which received signals received by a pair of receivers installed at a predetermined distance are calculated, and the arrival angle is calculated by calculating the propagation time difference of the signals.

JP 2011-252747 A, FIG. 1, FIG. 10, claim 1 Japanese Patent No. 4968827, FIG. 2, claim 1 JP 2018-204970 A, FIG. 1, claim 1 JP 2019-219274 A, FIG. 1, claim 1 JP 2020-176902 A, FIG. 1, claim 6

In the configuration disclosed in Patent Document 1, signals transmitted from multiple objects to be located are received, but when focusing on one object to be located, there are two receivers that receive a signal from one transmitter, but the configuration has a complex structure in which the correlation between the received signals is obtained to determine the information. In addition, in the embodiment of FIG. 10, it is necessary to measure the distance using a transponder to identify the accurate three-dimensional position. In the configuration disclosed in Patent Document 2, a transponder or four receivers are required to identify the three-dimensional position. In the configuration disclosed in Patent Document 3, GNSS antennas are required on both the transmitting and receiving sides. In the configuration disclosed in Patent Document 4, the positioning results obtained using multiple pairs of receivers (three or more) are processed to improve accuracy, and many receivers are required. In the configuration disclosed in Patent Document 5, the angle of arrival is obtained, and no method for identifying the three-dimensional position of the object to be located is mentioned.

In this invention, in order to solve the problems of the conventional technology described above, depth information of the object to be positioned is obtained from a depth detection device attached to the object to be positioned itself, and a signal transmitted from the object to be positioned is received by two receivers arranged at a predetermined interval. The distance to the object to be positioned and the angle of arrival of the signal transmitted from the transmitter are calculated by a predetermined calculation including a correlation function calculation and a time difference calculation of the timing of the correlation function output obtained as a result of the correlation function calculation, and the three-dimensional coordinates of the object to be positioned are obtained using the depth information and the calculated distance and angle of arrival.

That is, according to the present invention, a transmission signal generating means for generating a transmission signal;
a synchronization signal generating means for generating a synchronization signal having a predetermined time relationship with said transmission signal;
a wired cable for transmitting the transmission signal to a transmitter mounted on the underwater object to be positioned;
A depth detection device mounted on the object to be positioned;
a wired cable for transmitting depth information indicating the depth of the object to be positioned detected by the depth detection device;
a first and a second receiver disposed at a predetermined distance from each other for receiving a signal transmitted from the transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixing means for mixing the synchronous signal generated by the synchronous signal generator with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
An underwater positioning system is provided having a

With this configuration, the three-dimensional position of an underwater object can be obtained using only one transmitter and two receivers, and without using a GPS antenna/receiver.

A preferred embodiment of the underwater positioning system of the present invention is that the transmission signal generating means, the synchronization signal generating means, the first and second receivers, the first and second receiving amplifiers, the mixing means, the signal processing unit, and the three-dimensional coordinate calculation means are provided in an underwater positioning device located away from the object to be positioned.

A preferred embodiment of the underwater positioning system of the present invention is that the transmission signal generating means and the synchronization signal generating means are mounted on the object to be positioned, and the first and second receivers, the first and second receiving amplifiers, the mixing means, the signal processing unit, and the three-dimensional coordinate calculation means are provided in an underwater positioning device located away from the object to be positioned.

According to the present invention, an underwater positioning device for detecting the three-dimensional position of an underwater object to be positioned includes a transmission signal generating means for generating a transmission signal, a synchronization signal generating means for generating a synchronization signal having a predetermined time relationship with the transmission signal, a wired cable for transmitting the transmission signal to a wave transmitter mounted on the underwater object to be positioned, a wired cable for transmitting depth information indicating the depth of the object to be positioned detected by a depth detection device mounted on the object to be positioned, first and second wave receivers arranged at a predetermined distance and for receiving the signal transmitted from the wave transmitter, first and second receiving amplifiers for amplifying the signals received by the first and second wave receivers, respectively, and the synchronization signal generator. The underwater positioning device has a mixing means for mixing the synchronization signal generated by the first receiving amplifier with the output signal of the first receiving amplifier, a signal processing unit that inputs the output signal of the mixing means and the output signal of the second receiving amplifier via the audio L channel or R channel input, respectively, and calculates the distance to the object to be positioned and the angle of arrival of the signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of the timing of the correlation function output obtained as a result of the correlation function calculation, and a three-dimensional coordinate calculation means that obtains the three-dimensional coordinates of the object to be positioned using the depth information and the distance and the angle of arrival indicated by the output signal of the signal processing unit.

With this configuration, there is no need to provide devices such as a signal generator or a transmitting amplifier in the object to be positioned, and there is no need to design a pressure-resistant container to house these inside the object to be positioned. In addition, by using a PC, smartphone, tablet, or other device with two-channel audio input as the signal processing unit, it is possible to obtain the three-dimensional position of the underwater object to a considerable degree of accuracy with a simple configuration.

According to the present invention, there is also provided an underwater positioning device for detecting a three-dimensional position underwater, comprising:
a wired cable for receiving a synchronization signal having a predetermined time relationship with a transmission signal generated by the object to be positioned;
a wired cable for receiving depth information indicating the depth of the object to be positioned detected by a depth detection device mounted on the object to be positioned;
a first wave receiver and a second wave receiver disposed at a certain distance from each other when the transmission signal is amplified and transmitted from a wave transmitter mounted on the object to be located, the first wave receiver and the second wave receiver receiving the signal transmitted from the wave transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixing means for mixing the synchronous signal generated by the synchronous signal generator with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
An underwater positioning device is provided having:

With this configuration, the underwater positioning device does not send a transmission signal to a transmitter attached to the object to be positioned, so there is no need to consider the energy attenuation of the electrical signal depending on the cable length. By using a PC, smartphone, tablet, or other device with two-channel audio input as the signal processing unit, it is possible to obtain the three-dimensional position of the underwater object to be positioned with considerable accuracy using a simple configuration.

The present invention has the above configuration, so that the three-dimensional position of an underwater object can be obtained using only one transmitter and two receivers, and without using a GPS receiver. In addition, a personal computer, smartphone, tablet, or the like having two-channel audio input can be used as the signal processing unit that constitutes the present invention.

Table 1 shows a comparison of the present invention with various conventional methods.

In Table 1, when synchronization is "required," this means that synchronization is achieved using time information obtained from a GPS receiver, or that a synchronization signal is sent and received between devices via a wired cable.

Table 1 compares the four conventional methods, Methods A to D, with the present invention in terms of the type of required information, the necessity for time synchronization, the number of required receivers, etc. The relationship between the technologies disclosed in the above patent documents and each method is as follows:
Patent Document 1: Method B or Method C, SSBL method Patent Document 2: Method B or Method C, SSBL method Patent Document 3: Method B, SSBL method Patent Document 4: Method A or Method D, LBL method or SSBL method In Table 1, a transponder is a device that responds to a signal received by a receiver of a certain device and returns some kind of signal from a transmitter, and a transmitter and receiver form one set. Methods for measuring distance are divided into those that require time synchronization and those that do not. When time synchronization is required, a method is generally used in which accurate time information is obtained from a 1PPS signal obtained from a GPS (GNSS) receiver, and the distance is calculated from the difference between the reference time and the time of reception of the sound wave. When it is not required, the distance is calculated from the round-trip sound transmission time in the transponder. The angle of arrival is measured by measuring the difference in arrival time between signals input to two receivers. One pair (two) receivers are required for one angle of arrival information.

1 is a block diagram showing a first embodiment of an underwater positioning system and an underwater positioning device of the present invention. FIG. 2 is a block diagram showing a second embodiment of the underwater positioning system and the underwater positioning device of the present invention. 3 is a signal waveform diagram for explaining the operation of the signal processing unit in each embodiment shown in FIG. 1 and FIG. 2, and is a timing chart of correlation function output for received signals Ch1 and Ch2. 3 is a signal waveform diagram for explaining the operation of the signal processing unit in each embodiment shown in FIG. 1 and FIG. 2, and is a waveform diagram/timing chart showing the operation of reading out a predetermined section from the received signal Ch1. 4 is a signal waveform diagram for explaining the operation of the signal processing unit in each embodiment shown in FIG. 1 and FIG. 2, and is a waveform diagram/timing chart showing the relationship between correlation output 1 and correlation output 2 when section A in FIG. 4 is read out. 4 is a signal waveform diagram for explaining the operation of the signal processing unit in each embodiment shown in FIG. 1 and FIG. 2, and is a waveform diagram/timing chart showing the relationship between correlation output 1 and correlation output 2 when section B in FIG. 4 is read out. 3 is a signal waveform diagram for explaining the operation of the signal processing unit in each embodiment shown in FIG. 1 and FIG. 2, and is a waveform diagram/timing chart showing the relationship between two received signals and correlation output 2 and correlation output 3. 3 is a flowchart for explaining the operation of a signal processing unit in each of the embodiments shown in FIG. 1 and FIG. 2 . 3 is a spectrum diagram showing the frequency relationship between a transmission signal and a synchronization signal in each of the embodiments shown in FIG. 1 and FIG. 2. 3 is a schematic diagram for explaining the operation of a three-dimensional position calculation unit in each of the embodiments shown in FIG. 1 and FIG. 2. FIG. 3 is a diagram showing measurement results in each of the embodiments shown in FIG. 1 and FIG. 2 . 3 is a waveform diagram showing the time position relationship of correlation function outputs 1 to 3 in each of the embodiments shown in FIG. 1 and FIG. 2.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of the underwater positioning system and the underwater positioning device of the present invention. The underwater positioning system of the present invention has a device mounted on a positioning object 10 placed underwater, and an underwater positioning device 20 placed on the water for measuring the three-dimensional position of the positioning object 10. In this specification, the entire configuration underwater and above the water is called the underwater positioning system, and the part placed above the water is called the underwater positioning device. The underwater positioning device 20 is usually mounted on a ship or a structure on the water. As the positioning object 10, an ROV, which is a remote-controlled unmanned submersible (underwater robot), is used. The positioning object 10 is equipped with a depth detection device (not shown) that acquires depth information and a transmitter 12. As the ROV, for example, an underwater robot BlueROV2 manufactured by BlueRobtics can be used. As the depth detection device, a water depth/water pressure sensor Bar30 manufactured by the same company can be used.

The underwater positioning device 20 includes a signal generator 22 that generates a transmission signal and a synchronization signal having a predetermined time relationship with the transmission signal, a transmission amplifier 24 that amplifies the transmission signal, a wired cable 14 that transmits the output signal of the transmission amplifier to a wave transmitter 22 mounted on the object to be positioned 10, a wired cable 16 that receives depth information from the object to be positioned 10, first and second wave receivers 26A and 26B that respectively receive the transmission signal transmitted from the wave transmitter 12, and a first and second wave receiver 26A and 26B that respectively amplify the received signals received by the first and second wave receivers 26A and 26B. The device has first and second receiving amplifiers 28A and 28B for detecting the distance and arrival angle of the object 10 to be positioned, an analog mixer 30 for mixing the output signal of the first receiving amplifier 28A with the synchronization signal generated by the signal generator 22, a signal processing unit 32 for inputting the output signal of the analog mixer 30 and the output signal of the second receiving amplifier 28B to calculate the distance and arrival angle, and a three-dimensional position calculation unit 34 for inputting the distance and arrival angle obtained by the signal processing unit 32 and the depth information provided by the object 10 to be positioned to calculate the three-dimensional position coordinates of the object 10 to be positioned.

The signal generator 22 and the transmission amplifier 24 constitute a transmission signal generating means. The signal generator 22 also constitutes a synchronization signal generating means. The analog mixer 30 constitutes a mixing means. Furthermore, the three-dimensional position calculation unit 34 constitutes a three-dimensional coordinate calculation means. The wired cable 16 may be a dedicated wired cable used to transmit a control signal from an above-water control device (not shown) that controls the operation of the object to be positioned 10 itself to the object to be positioned 10. As these wired cables, underwater cables manufactured by BlueRobtics may be used.

The signal processing unit 32 can be a personal computer, smartphone, tablet, etc. with a two-channel stereo audio input terminal. In the first embodiment of FIG. 1, the output of the analog mixer 30 is supplied to the L (left) channel input, and the output of the second receiving amplifier 28B is supplied to the R (right) channel input, but this is not limited to the left and right. Various calculations are performed on the signals input to these left and right channels by a predetermined signal processing method described below. The first and second receivers 26A and 26B are arranged at a predetermined interval.

Next, the operation of the first embodiment of FIG. 1 will be described. Underwater sound signals transmitted from the transmitter 12 mounted on the object 10 to be positioned are received by the first and second receivers 26A and 26B, which are spaced apart by a predetermined distance, and converted into electrical signals, respectively. These electrical signals are amplified by the first and second receiving amplifiers 28A and 28B, respectively, and the output signal of the first receiving amplifier 28A is mixed with a synchronization signal by the analog mixer 30 and then input to the signal processing unit 32. The signal processing unit 32 can be configured as a computer with two channels of audio input, or other similar device. The distance and angle of arrival in the signal processing unit 32 are calculated by software calculation processing, as described later. From the depth information acquired from the object 10 to be positioned and the distance and angle of arrival information obtained by the signal processing unit 32, the three-dimensional coordinates are calculated in the three-dimensional position calculation unit 34, as described later.

The timing chart of the transmission signal, synchronization signal, and reception signal is shown in Figure 3. The transmission signal and synchronization signal are generated and output by the signal generator 22. The transmission signal and synchronization signal are pseudo-noise signals or chirp signals generated from the PN code. The transmission signal is repeatedly transmitted with a period T. The synchronization signal is repeatedly transmitted at a time position shifted by half a period (T/2) from the timing of the transmission signal. Since the transmission signal becomes a reception signal via the transmitter 12, underwater acoustic transmission, and the first and second receivers 26A and 26B, the time position of the reception signal moves according to the sound wave propagation time. Since the synchronization signal is transmitted as an electrical signal via the wired cable 14, its transmission delay can be ignored. The output signal of the first reception amplifier 28A, i.e., one of the reception signals Ch1 and the synchronization signal, are mixed by the analog mixer 30 and input to the signal processing unit 32.

In order to find the time positions of the synchronization signal and the received signal in the signal processing unit 32, a correlation function calculation is performed using the synchronization signal replica and the received signal. Here, the synchronization signal replica is explained. The signal generator 22 in FIG. 1 outputs the transmission signal and synchronization signal, but in order to generate these signals, the transmission signal data and synchronization signal data are calculated in advance on software, the data is stored in memory, and the data is repeatedly read from the memory, digital-to-analog converted by a D/A converter, and then output as an analog signal. If the signal processing unit 32 in FIG. 1 performs the same calculation process as the software in the signal generator 22, it can generate the exact same transmission signal data and synchronization signal data. These data are called the "synchronization signal replica" and the "transmission signal replica".

Correlation function output 1 is the correlation function between received signal Ch1 and the synchronization signal replica, and correlation function calculation output 2 is the correlation function between received signal Ch1 and the transmission signal replica. The time difference Δ ₁ [s] is found from the time position of the maximum peak of correlation function output 1 and the time position of the maximum peak of correlation function output 2. Since the time position of the synchronization signal is shifted by half a period from the transmission signal, the time difference between the transmission signal and received signal Ch1 can be found from Δ ₂ = Δ ₁ -t/2 [s]. This time difference is the sound wave propagation time from the transmitter to the receiver, so the distance R [m] is found from equation (1).

where C [m/s] is the speed of sound in water.

The above two replicas (copies) are digital data stored in software or memory and are not materialized. However, they are materialized only when the data of the synchronization signal replica and transmission signal replica stored in the memory of the signal generator 22 is read out and output by a D/A converter, becoming the original synchronization signal and transmission signal. In other words, the timing of reading the beginning of the data of the synchronization signal replica and transmission signal replica becomes the transmission timing of the synchronization signal and transmission signal.

In order for the signal processing unit 32 to generate a "synchronization signal replica" and a "transmission signal replica," there are no particular restrictions on the timing of reading data from memory, and there is no need to synchronize with the timing of reading (A/D conversion and data entry into memory). For example, if we consider the section surrounded by dotted line A and the section surrounded by dotted line B for the waveform of the received signal Ch1 of the signal processing unit 32 as shown in Figure 4, these two sections A and B show states in which reading is performed at different times and in different sections.

Now, for the section A in Fig. 4, when a correlation function calculation is performed on these captured data using the synchronization signal replica and the transmission signal replica, the waveforms of the correlation function output 1 and the correlation function output 2 as shown in Fig. 5 are obtained. As described above, the time difference _Δ1 can be obtained from the peak timing difference between the correlation function output 1 and the correlation function output 2. On the other hand, for the section B in Fig. 4, that is, even if the data is captured at a timing different from that of the section A, the peak timing difference between the correlation function output 1 and the correlation function output 2 is the same as shown in Fig. 6, so that the distance and the angle of arrival can be detected regardless of the timing at which the waveform is captured. Therefore, the timing at which the waveform is captured in the signal processing unit 32 is arbitrary, and it is not necessary for the signal processing unit 32 to perform control to match the transmission timing of the transmission signal and the synchronization signal output from the signal generator 22.

The arrival angle is calculated by measuring the time difference between two received signals using software processing in the signal processing unit, and converting the time difference into the arrival angle θ [deg]. The method for measuring the time difference is also described in Patent Document 5, but the general method is described below.

Fig. 7 is a timing chart of the correlation function output for received signals Ch1 and Ch2. As explained in Fig. 3, correlation function output 2 is obtained by calculating the correlation function between received signal Ch1 and the transmission signal replica. Correlation function output 3 is obtained by performing the correlation function calculation process of received signal Ch2 and the transmission signal replica in the same manner. The time positions of the waveform peaks of correlation function output 2 and correlation function output 3 are found, and the time difference Δ ₃ [s] between them is measured. The above time difference is converted to the angle of arrival using the following formula.

C [m/s] is the speed of sound in water, and d [m] is the installation distance between the first receiver 26A and the second receiver 26B shown in Figure 1.

Figure 8 is a flow chart explaining the operation of the CPU when the signal processing unit 32 is configured as a computer. In step S1, a "synchronization signal replica is generated using the method described above. Next, in step S2, a transmission signal replica is generated in a similar manner. In step S3, a correlation function between the received signal, which is the output signal of the first receiving amplifier 28A, and the synchronization signal replica is calculated to obtain correlation function output 1. Next, in step S4, a correlation function between the received signal, which is the output signal of the first receiving amplifier 28A, and the transmission signal replica is calculated to obtain correlation function output 2. In step S5, the time difference Δ1 between the correlation function outputs 1 and 2 is calculated from the time positions of the maximum peaks of each. In step S6, the time difference Δ1 is used to calculate two periods of the transmission signal. A time difference Δ2 between the transmission signal and the reception signal, which is the output signal of the first reception amplifier 28A, is calculated by subtracting one-third of the time. In step S7, the time difference Δ2 and the speed of sound in water are used to calculate the distance between the transmitter 12 and the first receiver 26A. In step S8, the correlation function between the reception signal, which is the output signal of the second reception amplifier 28B, and the transmission signal replica is calculated to obtain a correlation function output 3. In step S9, the time difference Δ3 between the two is calculated from the time positions of the maximum peaks of the correlation function output 2 and the correlation function output 3. In step S10, the angle of arrival θ is calculated using the time difference Δ3, the speed of sound in water, and the installation distance between the first and second receivers.

A common method for detecting the position of an object using the above correlation function is to calculate the correlation function for a signal and detect the time position of the signal from the peak position. For example, in the document (Nop. 1059 September 2003) of the Port and Airport Research Institute, pages 9-10, 4.4 "Measurement of Propagation Time Using M-sequences" describes an underwater coordinate measurement technology using ultrasonic waves. The URL for the document is shown below.
https://www.pari.go.jp/search-pdf/no1059.pdf

Figure 9 is a spectrum diagram showing the frequency relationship between the transmission signal and the synchronization signal. By using different frequency bands for the transmission signal and the synchronization signal, interference between the two is prevented after output from the analog mixer 30. The synchronization signal can be assigned a band different from the transmission and reception frequency bands of the transmitter 12 and receivers 26A and 26B. The synchronization signal is assigned a band that falls within the frequency characteristics of the analog mixer 30 so that the signal does not oscillate when input to the analog mixer 30.

When the depth obtained from the object 10 to be positioned is D [m], a method for calculating the three-dimensional position from the depth, distance, and angle of arrival is shown in Fig. 10. The coordinates of the first receiver 26A are the origin O (0,0,0), and the coordinates of the object 10 to be positioned (sound source position) are Q ( _xT , _yT , _zT ). The coordinate Q is on a line of a circle with a distance (radius) R from the origin on a plane formed by the angle of arrival θ, and exists at a position where the z coordinate is the depth D, so _xT , _yT , _zT indicating the three-dimensional position can be calculated by the following three equations.

Using the _xT , _yT , _zT data indicating the three-dimensional position thus obtained, the sound source position, i.e., the position of the object to be located, can be mapped on a three-dimensional or two-dimensional graph.

A positioning experiment was carried out in the Kitami Municipal Heated Pool in Hokkaido, in which a wave transmitter 12 was attached to an underwater robot (object 10) to determine the three-dimensional position of the underwater robot. The size of the pool was 25 m wide, 15 m deep, and 1.35 m deep. The frequency band of the transmission signal was 12 kHz to 32 kHz, and the frequency band of the synchronization signal was 2 kHz to 8 kHz. The distance between the first wave receiver 26A and the second wave receiver 26B was 0.3 m. The positioning results are shown in Figure 11. The first wave receiver 26A was installed at position (0,0,0) in the xyz coordinate system, and the relative position of the wave transmitter 12 from that reference point was plotted on a three-dimensional graph.

12 shows the waveforms of correlation function output 1, correlation function output 2, and correlation function output 3 for a given transmitter position. The time difference Δ ₁ = 53 [ms] between correlation function output 1 and correlation function output 2 peak is calculated, and the time difference between the transmission signal and the reception signal Ch1 is calculated using Δ ₂ = Δ ₁ - T/2 = 3 [ms]. Therefore, the distance is calculated as R = 4.5 [m] from equation (2) using the underwater sound speed C = 1500 [m/s]. The time difference between correlation function output 2 and correlation function output 3 peak is Δ ₃ = 0.135 [ms], and the arrival angle θ = 41.8 [deg] from equation (2) using the reception interval d = 0.3 [m]. The depth output from the depth detection device of the underwater robot BlueROV is D = 1.2 [m], and by substituting numerical values for each variable in equations (3) to (5), the three-dimensional coordinates ( _xT , _yT , _zT ) = (3.1, 3.5, 1.2) are obtained. Note that the positive and negative directions of the z-axis are reversed in the graph of Figure 11, and the positioning point is plotted at the position (3.1, 3.5, -1.2).

Next, a second embodiment of the present invention will be described with reference to FIG. 2. In the first embodiment described above, the underwater positioning device 20 is provided with a signal generator 22 and a transmission amplifier 24, but in the second embodiment, the signal generator 22 and the transmission amplifier 24 are mounted on the object to be positioned 10A, not on the underwater positioning device 20A. The transmission signal generated by the signal generator 22 is amplified by the transmission amplifier 24 and provided to the wave transmitter 12, and a predetermined transmission signal is transmitted from the wave transmitter 12. The synchronization signal generated by the signal generator 22 is supplied to the analog mixer 30 in the underwater positioning device 20A via the wired cable 18. Depth information detected by a depth sensor (not shown) mounted on the object to be positioned 10A is supplied to the three-dimensional position calculation unit 34 in the underwater positioning device 20A via the wired cable 16. The other configurations are the same as those of the first embodiment, so description will be omitted.

In addition, the signal processing in the second embodiment of FIG. 2 is the same as that described in the first embodiment above, so a duplicated description will be omitted. Here, the differences between the first and second embodiments will be considered. In the first embodiment, the object 10 itself does not need to be provided with devices such as a signal generator and a transmission amplifier, and there is no need to design a pressure-resistant container to house these inside the object. However, when sending an electrical signal from the transmission amplifier 24 provided in the underwater positioning device 20 to the transmitter 12 attached to the object 10 via the wired cable 14, it is necessary to consider the energy attenuation of the electrical signal according to the cable length, and the wired cable 14 needs to be a sturdy coaxial cable that can withstand high-voltage transmission in order to send a high-voltage electrical signal. In contrast, in the second embodiment, the signal generator 22 and the transmission amplifier 24 need to be housed in a pressure-resistant container (not shown) together with the control device of the object 10A, but the requirements for the wired cable 14 required in the first embodiment are relaxed. In the second embodiment, the object to be positioned 10A must be designed so that the signal generator 22 and the transmission amplifier 24 are housed in a pressure-resistant container of the object to be positioned 10A.

The underwater positioning system/device of the present invention has the above-mentioned configuration, and by using a personal computer, smartphone, tablet, etc. with two-channel audio input as the signal processing unit, it is possible to obtain the three-dimensional position of an underwater object to be positioned with considerable accuracy with a simple configuration, and is therefore useful in various industries including government, such as various underwater construction works under the sea, lakes, rivers, and other waters where it is necessary to grasp the three-dimensional position of an underwater object to be positioned, and ensuring the safety of ship routes by grasping the bottom of the sea, lakes, and rivers, as well as in the fishing industry.

10, 1A Positioning target (ROV)
12 Transmitter 14, 16, 18 Wired cable 20, 20A Underwater positioning device 22 Signal generator 24 Transmission amplifier 26A, 26B First and second receivers 28A, 28B First and second receiving amplifiers 30 Analog mixer 32 Signal processing unit 34 Three-dimensional position calculation unit A, B Signal extraction section

Claims (7)

a transmission signal generating means for generating a transmission signal;
a synchronization signal generating means for generating a synchronization signal having a predetermined time relationship with said transmission signal;
a wired cable for transmitting the transmission signal to a transmitter mounted on the underwater object to be positioned;
A depth detection device mounted on the object to be positioned;
a wired cable for transmitting depth information indicating the depth of the object to be positioned detected by the depth detection device;
a first and a second receiver disposed at a predetermined distance from each other for receiving a signal transmitted from the transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixer for mixing the sync signal generated by the sync signal generating means with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
An underwater positioning system having: The underwater positioning system according to claim 1, characterized in that the transmission signal generating means, the synchronization signal generating means, the first and second receivers, the first and second receiving amplifiers, the mixing means, the signal processing unit, and the three-dimensional coordinate calculation means are provided in an underwater positioning device located away from the object to be positioned. A transmission signal generating means for generating a transmission signal mounted on the underwater object to be positioned;
a synchronization signal generating means for generating a synchronization signal having a predetermined time relationship with the transmission signal, the synchronization signal being mounted on the underwater object to be positioned;
a wired cable for transmitting the transmission signal generated by the transmission signal generating means to a wave transmitter mounted on an underwater object to be positioned;
A depth detection device mounted on the object to be positioned;
a wired cable for transmitting depth information indicating the depth of the object to be positioned detected by the depth detection device;
a first and a second receiver disposed at a predetermined distance from each other for receiving a signal transmitted from the transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixer for mixing the sync signal generated by the sync signal generating means with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
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An underwater positioning system, characterized in that the first and second receivers, the first and second receiving amplifiers, the mixing means, the signal processing unit, and the three-dimensional coordinate calculation means are provided in an underwater positioning device located away from the object to be positioned . the signal processing unit includes: a synchronization signal replica generating means for generating a synchronization signal replica having the same period as the synchronization signal; a transmission signal replica generating means for generating a transmission signal replica having the same period as the transmission signal; a first correlation function calculating means for calculating a correlation function between a reception signal which is an output signal of the first reception amplifier and the synchronization signal replica, which is included in an output signal of the mixing means, to obtain a correlation function output 1; a second correlation function calculating means for calculating a correlation function between a reception signal which is an output signal of the first reception amplifier and the transmission signal replica, to obtain a correlation function output 2; a first time difference calculating means for calculating a time difference Δ1 between the correlation function outputs 1 and 2 from the time positions of the maximum peaks of each of the correlation function outputs 1 and 2; a second time difference calculation means for calculating a time difference Δ2 between the transmission signal and the reception signal which is the output signal of the first receiving amplifier by subtracting the time between the transmission signal and the reception signal which is the output signal of the first receiving amplifier; a first distance calculation means for calculating a distance between the transmitter and the first receiver using the time difference Δ2 and the underwater sound speed; a third correlation function calculation means for calculating a correlation function between the reception signal which is the output signal of the second receiving amplifier and the transmission signal replica to obtain a correlation function output 3; a third time difference calculation means for calculating a time difference Δ3 between the two from the time positions of the maximum peaks of the correlation function output 2 and the correlation function output 3; and an arrival angle calculation means for calculating an arrival angle θ using the time difference Δ3, the underwater sound speed, and the installation interval between the first and second receivers. An underwater positioning device for detecting a three-dimensional position of an underwater object to be positioned, comprising: a transmission signal generating means for generating a transmission signal;
a synchronization signal generating means for generating a synchronization signal having a predetermined time relationship with said transmission signal;
a wired cable for transmitting the transmission signal to a transmitter mounted on the underwater object to be positioned;
a wired cable for transmitting depth information indicating the depth of the object to be positioned detected by a depth detection device mounted on the object to be positioned;
a first and a second receiver disposed at a predetermined distance from each other for receiving a signal transmitted from the transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixer for mixing the sync signal generated by the sync signal generating means with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
An underwater positioning device having: An underwater positioning device for detecting a three-dimensional position of an underwater object,
a wired cable for receiving a synchronization signal having a predetermined time relationship with a transmission signal generated by the object to be positioned;
a wired cable for receiving depth information indicating the depth of the object to be positioned detected by a depth detection device mounted on the object to be positioned;
When the transmission signal is amplified and transmitted from a transmitter mounted on the object to be located, first and second receivers are provided at a certain distance apart to receive the signal transmitted from the transmitter;
a first receiving amplifier and a second receiving amplifier for amplifying signals received by the first receiving device and the second receiving device, respectively;
a mixer for mixing the sync signal generated by the sync signal generating means with an output signal of the first receiving amplifier;
a signal processing unit which receives an output signal of the mixing means and an output signal of the second receiving amplifier via an audio L channel or R channel input, respectively, and calculates a distance to the object to be positioned and an angle of arrival of a signal transmitted from the wave transmitter by a predetermined calculation including a correlation function calculation and a time difference calculation of a correlation function output obtained as a result of the correlation function calculation;
a three-dimensional coordinate calculation means for obtaining three-dimensional coordinates of the object to be positioned by using the depth information, the distance and the angle of arrival indicated by the output signal of the signal processing unit;
An underwater positioning device having: the signal processing unit includes: synchronization signal replica generating means for generating a synchronization signal replica having the same timing period as the synchronization signal; transmission signal replica generating means for generating a transmission signal replica having the same timing period as the transmission signal; first correlation function calculating means for calculating a correlation function between a reception signal which is an output signal of the first reception amplifier and the synchronization signal replica, which is included in the output signal of the mixing means, to obtain a correlation function output 1; second correlation function calculating means for calculating a correlation function between a reception signal which is an output signal of the first reception amplifier and the transmission signal replica, to obtain a correlation function output 2; first time difference calculating means for calculating a time difference Δ1 between the correlation function output 1 and the correlation function output 2 from the time positions of the maximum peaks of each of the correlation function output 1 and the correlation function output 2; a second time difference calculation means for calculating a time difference Δ2 between the transmission signal and the reception signal which is the output signal of the first receiving amplifier by subtracting half the time of the transmission signal from the reception signal; a first distance calculation means for calculating a distance between the transmitter and the first receiver using the time difference Δ2 and the underwater sound speed; a third correlation function calculation means for calculating a correlation function between the reception signal which is the output signal of the second receiving amplifier and the transmission signal replica to obtain a correlation function output 3; a third time difference calculation means for calculating a time difference Δ3 between the two from the time positions of the maximum peaks of the correlation function output 2 and the correlation function output 3; and an arrival angle calculation means for calculating an arrival angle θ using the time difference Δ3, the underwater sound speed, and the installation interval between the first and second receivers.

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