A device and method for accurately locating a sound source in an alkylbenzene medium

Abstract

The invention discloses a device and method for accurately locating a sound source in an alkylbenzene medium, belonging to the field of signal and information processing; comprising a main control computer, an interface extension, a transmitting transducer and a receiving transducer; the transmitting transducer is arranged on a positioned ROV, and the ROV is located in a spherical container filled with alkylbenzene medium; the transmitting transducer transmits an acoustic beacon signal at a set period, and uses a timing synchronization device to simultaneously detect and record the moment when the signal reaches the receiving transducer; 8 receiving transducers are evenly distributed on the inner wall of the spherical container filled with alkylbenzene medium, and the array positions are respectively located at 8 vertices of a space cube, receiving acoustic signals from the transmitting transducer. Then, the spatial positioning coordinate accuracy of the ROV is optimized by least squares, and the fitting of discrete points in space is applied to the positioning in the alkylbenzene medium. According to certain optimization criteria, the position accuracy of the ROV is optimized, and the distance measurement error accuracy of the ROV position can be achieved within a 30-meter sphere range, and is not greater than 30 cm.

Description

Technical Field

[0001] The invention belongs to the field of signal and information processing, and in particular relates to a device and method for accurately locating a sound source in an alkylbenzene medium. Background Art

[0002] Precise positioning of sound sources in alkylbenzene media is one of the important contents of neutrino research experimental equipment and is also a typical application of underwater acoustic short-baseline positioning technology.

[0003] Neutrinos are one of the most basic units that make up the material world. Compared with other basic particles, quarks and charged leptons, they have unique properties and are difficult to detect. They are the least understood particles and have many unsolved mysteries. Research on unknown issues of neutrinos will not only improve our understanding of the most basic laws of the material world, but also may lead to the existing theoretical system of particle physics. Entering the 21st century, neutrino research has flourished and has become one of the most important branches of particle physics. It has also expanded to many disciplines such as astronomy, cosmology, and geophysics, forming "neutrino science". The experimental research on neutrinos has a history of more than 60 years and has made many major discoveries, including the discovery of three types of neutrinos and the discovery of neutrino oscillations. It has been awarded the Nobel Prize three times. my country's neutrino experimental research started very late, but has achieved very good results. The idea of ​​the Daya Bay Reactor Neutrino Experiment was proposed in 2003. The experiment was completed at the end of 2011. In just over two months, a new neutrino oscillation mode was discovered, which shocked the international particle physics community and was rated as one of the top ten scientific breakthroughs of the year by the American Science magazine. In 2008, the idea of ​​measuring the mass order of neutrinos was proposed. In 2013, the Jiangmen Underground Neutrino Observatory (JUNO system) was approved and is expected to be completed in 2020. The main physical goals of this project are to determine the mass order and accurately measure the mixing parameters. At the same time, it can carry out a number of internationally leading studies on supernova neutrinos, solar neutrinos, terrestrial neutrinos, atmospheric neutrinos, etc. The JUNO project established an experimental station in Kaiping City, Jiangmen, Guangdong Province, 53km away from Yangjiang Nuclear Power Plant and Taishan Nuclear Power Plant. The experiment will build a liquid scintillator detection container filled with a mass of 20,000 tons. The liquid scintillator medium uses alkylbenzene medium and is located 700m underground. The project can carry out related research such as reactor neutrino energy spectrum measurement, as well as many other cutting-edge scientific research. The experimental equipment of this project is as follows: Figure 2 shown.

[0004] Before the entire test device officially starts working or during use, the photomultiplier tube needs to be calibrated. During the calibration work, a small vehicle (ROV) carrying a radioactive pod will move in the spherical tank under command control. According to the test requirements, the precise position of the ROV needs to be measured in real time, and the positioning error does not exceed 30mm. The positioning systems that can be used include laser positioning, electromagnetic positioning, and acoustic positioning. Due to the particularity of the neutrino experiment, electromagnetic and laser will affect the experiment, and the acoustic method becomes the only choice. Therefore, it is necessary to develop a positioning system to achieve accurate positioning of the ROV small vehicle. The system is collectively referred to as the Juno (JUNO) calibration system or the JUNO positioning system.

[0005] The hydroacoustic positioning system has a long history of development and has achieved many important results. The hydroacoustic positioning system is composed of multiple primitives, and the line between the primitives is called the baseline. The hydroacoustic positioning system can be classified according to the relative relationship between the baseline length and the detection distance, or according to the absolute size of the baseline. According to the absolute size of the baseline, the hydroacoustic positioning system can be divided into a long baseline system, a short baseline system and an ultra-short baseline system. The long baseline is about 100 to 6000 meters, the short baseline is 1 to 50 meters, and the ultra-short baseline is <1 meter.

[0006] The hydroacoustic positioning technology has been well developed at home and abroad, and the productization, industrialization and serialization of the hydroacoustic positioning system have been realized. The main international hydroacoustic positioning system manufacturers include: Norway, France, the United Kingdom and many other companies. Norwegian companies are currently the most prominent companies in the industry. Kongsberg has many mature HIRAP series products, which have many users in the civilian and military markets. In 1997, the company launched the HIRAP350 series of products, which is a milestone product of the long-range ultra-short baseline positioning system, and its working distance can reach 3,000 meters; followed by HIPAP500, the working distance of this model is further increased to 4,000 meters; the company's latest flagship product is IHPAP10, which can provide a ranging accuracy of better than 50 cm at a working distance of 10,000 meters. At present, the company has become the actual leader of industry standards, and the series of products are already excellent comprehensive positioning systems that can work in two modes: long baseline and ultra-short baseline.

[0007] Ixsea of ​​France also has a number of products that have been commercialized in multiple fields such as underwater positioning, navigation, and mapping. The products cover ultra-short baseline, short baseline, and long baseline systems. The company's high-precision short-baseline underwater positioning system POSIDONIA6000 is well-known in the industry. This model can still guarantee high performance under harsh conditions, with a maximum range of 6,000 meters. It is also used by many domestic scientific research ships. The company's MIPS system is a small ultra-short baseline positioning system designed for tracking underwater targets. The operating distance can reach 1,500 meters. Due to its low price and easy installation and use, it has also been widely used.

[0008] Sonardyne in the UK is another company that focuses on the research and development of hydroacoustic products and equipment. The company's products mainly involve the positioning of underwater buildings (such as drilling platforms), anti-frogman, ocean measurement, etc., and the product line also covers ultra-short baseline, short baseline, and long baseline systems. The company's Ranger series ultra-short baseline positioning system has two models: the regular version and the upgraded version. The regular version has a maximum range of 2,000 meters and can simultaneously locate and track 4 targets; the upgraded version has a maximum range of more than 4,000 meters and can simultaneously locate and track 10 targets.

[0009] Domestic research on underwater acoustic positioning technology has also made great progress, with research units including Northwestern Polytechnical University, Harbin Engineering University, 715 Institute, 726 Institute and Institute of Acoustics of the Chinese Academy of Sciences. Some long and short baseline positioning systems have also been developed and applied in marine engineering.

[0010] Judging from the current research and related products in existing technologies at home and abroad, the positioning accuracy of the relevant systems is mostly greater than 10 meters. In order to further improve the positioning accuracy, methods such as improving the signal-to-noise ratio are usually used to improve the positioning accuracy in seawater or lake environments. However, there will be a lot of reverberation in the organic glass environment of the JUNO system. By improving the signal-to-noise ratio, more noise will be generated, resulting in greater positioning errors. Therefore, the existing technology cannot meet the requirements of high-precision positioning of the JUNO system, and new methods must be found. This project designs a new precise sound source positioning system in alkylbenzene medium, which can fully meet the positioning requirements of the JUNO system.

[0011] The acoustic beacon accurate positioning device in the alkylbenzene medium of the present invention is a part of the acoustic positioning system specially designed for JUNO. The medium filled with the sphere is the alkylbenzene medium, so the positioning system of the system becomes the acoustic positioning problem in the alkylbenzene medium. Since the specific gravity of the alkylbenzene medium is close to that of the water medium, the speed of sound in the medium is also close to that of water, so the relevant method of acoustic positioning in water can be adopted. Summary of the invention

[0012] Technical issues to be solved:

[0013] In order to avoid the shortcomings of the prior art, the present invention proposes a device and method for accurately locating a sound source in an alkylbenzene medium. The device uses a precise positioning device with a transmitting transducer and a multi-element receiving array. The device can accurately determine the position of a small-sized vehicle ROV, and achieves a precise positioning indicator that the positioning distance error of the ROV in a spherical container filled with alkylbenzene medium with an inner diameter of 30 meters does not exceed 30 mm, which fully meets the positioning requirements of the JUNO system.

[0014] The technical solution of the present invention is: a device for accurately locating a sound source in an alkylbenzene medium, characterized in that it comprises a main control computer, an interface extension, a transmitting transducer and a receiving transducer, and the various parts are connected by cables;

[0015] The main control computer includes a display and control module and a comprehensive processing module, the display and control module is used to realize the comprehensive human-computer interaction of the positioning system, and the comprehensive processing module is used to realize the core control and positioning solution functions of the positioning system;

[0016] The interface extension includes a signal generating module and a signal receiving module, wherein the signal generating module is used to realize the generation of the transmission signal waveform and drive the transmission, and the signal receiving module is used to realize the preprocessing of the received signal and the signal detection;

[0017] The transmitting transducer is arranged on the positioned ROV, and the ROV is located in a spherical container filled with alkylbenzene medium; the transmitting transducer transmits the acoustic beacon signal at a set period, and uses a timing synchronization device to simultaneously detect and record the time when the signal reaches the receiving transducer;

[0018] The eight receiving transducers are evenly distributed on the inner wall of a spherical container filled with alkylbenzene medium, and the array positions are respectively located at the eight vertices of a space cube, for receiving acoustic signals from the transmitting transducer.

[0019] A further technical solution of the present invention is that the cable is a multi-core cable, which is retracted and released and its length is adjusted by a winch.

[0020] A further technical solution of the present invention is: the display and control module includes a display of target positioning information and a display of ROV sensor parameters, and is used to set relevant parameters of the transmitting and receiving modules and the ROV running trajectory.

[0021] A further technical solution of the present invention is: the comprehensive processing module includes distance information solution, position information solution, and transmitting and receiving module control to achieve comprehensive communication with the ROV system and comprehensive communication with the host computer system.

[0022] A method for positioning using a sound source accurate positioning device in an alkylbenzene medium, characterized by the following specific steps:

[0023] Step 1: Input the target location point that the ROV is expected to reach in the human-computer interaction interface of the display and control module;

[0024] Step 2: calling the signal generating module through the integrated processing module to drive the transmitting transducer to transmit an ultrasonic signal; then the receiving transducer receives the ultrasonic signal, and processes the ultrasonic signal through the signal receiving module;

[0025] Step 3: The received signal processed in step 2 is estimated by the comprehensive processing module, and the distance between the transmitting transducer and the receiving transducer is calculated according to the multiple sets of delay information;

[0026] Step 4: The comprehensive processing module calculates the current position and posture of the ROV based on the information of the distance between the multiple sets of transmitting transducers and receiving transducers;

[0027] Step 5: The comprehensive processing module sends the current position and posture of the ROV obtained in step 4 and the target position point in step 1 to the ROV system control, and the ROV system moves to the target position;

[0028] Step 6: After the ROV reaches the vicinity of the target position, the position and attitude are calculated again until the ROV system hovers stably at the target position, and finally the current target position is sent to the upper computer of the positioning device.

[0029] A further technical solution of the present invention is: the method for calculating the distance between the transmitting transducer and the receiving transducer in step 3: using a timing synchronization device to detect and record the time when the signal reaches the receiving transducer, and obtain the time difference t between the transmitting transducer transmitting the sound wave signal and the receiving transducer receiving the sound wave signal, and the receiving time is the time when the amplitude of the receiving signal reaches the threshold value;

[0030] Then, by formula S i =υt i , i = 1, 2, 3...8, calculate the distance S between the transmitting transducer and the i-th receiving transducer i , where υ is the propagation speed of sound waves in the medium, t i It represents the time difference between the transmitting transducer transmitting the sound wave signal and the i-th receiving transducer receiving the sound wave signal.

[0031] A further technical solution of the present invention is that the threshold value is an adaptive threshold value, firstly the amplitude of the transmitting signal of the transmitting transducer is obtained, and then the 2 / 3 peak amplitude of the transmitting signal amplitude is set as the threshold value.

[0032] A further technical solution of the present invention is that the propagation speed v of the sound wave in the medium varies with the depth. First, the transmission speed v0 of the sound wave from the transmitting transducer and the receiving speed v of the i-th receiving transducer are measured. ti , then calculate the average value to get the propagation speed υ, and then calculate the distance S between the transmitting transducer and the i-th receiving transducer by the following formula i :

[0033]

[0034] A further technical solution of the present invention is: in step 4, according to the measured distance between the transmitting transducer and the receiving transducer on the ROV and the corresponding geometric position, the precise spatial position of the ROV is obtained in real time; the center of the spherical container filled with alkylbenzene medium is set as the midpoint of the coordinate system, and the current position coordinates of the ROV are set as (x, y, z), and the position coordinates are solved by the least squares algorithm to obtain f(X)=(AX-b) T The minimum point of (AX-b) is the following equation, which is the x, y, and z position coordinates of the spacecraft;

[0035]

[0036] A and b are composed of 4 receiving points and corresponding 4 sets of distance information.

[0037] X=(x,y,z) T ,

[0038]

[0039] Then the simulated annealing method is used to find the optimal solution for the current position information. The function of the simulated annealing algorithm used for positioning to solve the minimum value F is:

[0040]

[0041] Where (x, y, z) is the current position coordinate, (x i ,y i ,z i ) is the coordinate of the ith array element, s i is the distance corresponding to the time delay received by the i-th receiving transducer;

[0042] The optimal solution is obtained by iteratively obtaining the minimum value of the objective function F, so that the maximum error of the receiving transducer position is controlled within 8 mm, the overall positioning error is within 25 mm, and the positioning error of the x and y coordinates of the ROV is within 25 mm.

[0043] Beneficial Effects

[0044] The beneficial effects of the present invention are:

[0045] At present, there is no related research on applying acoustic positioning technology to alkylbenzene media in the prior art. The prior art generally positions ROVs in seawater environments. The seawater environment is a relatively open environment, and the interference of reflected sound waves does not need to be considered during the propagation of sound waves. Therefore, the accuracy can be improved by improving the signal-to-noise ratio. The present invention uses sound waves to measure speed and position in a limited space. At the same time, the limited space is filled with alkylbenzene media. Therefore, the signal-to-noise ratio of the sound wave must be controlled within a range greater than 6dB, so that the interference of the reflected sound wave can be ignored relative to the test sound wave, and will not interfere with the test sound wave, thereby affecting the positioning accuracy.

[0046] The present invention arranges 8 receiving transducers on the inner surface of a spherical container filled with alkylbenzene medium with an inner diameter of 30 meters, and arranges a transmitting transducer on an ROV; the 8 receiving transducers constitute 8 vertices of a cube, and a total of 4 receiving transducers A, B, C, and D are evenly arranged along the circumferential direction in the same horizontal plane, and are respectively located in the first, second, third, and fourth quadrants, corresponding to 4 transducers a, b, c, and d in the vertical direction thereof. The error accuracy index requirement of the positioning system can be met by adopting this array mode; since the requirement for radiation in the alkylbenzene medium is relatively high, if the radiation exceeds the standard, the detection of neutrinos will be affected. In the present invention, the setting of the 8 receiving transducers can control the radiation below the standard requirement, thereby ensuring that the neutrino detection is not interfered with.

[0047] In general, the least square method is applied to linear fitting to solve the problem of linearization of discrete points. However, the present invention optimizes the spatial positioning coordinate accuracy of the ROV by the least square method, and applies the fitting of discrete points in space to the positioning in the alkylbenzene medium. The simulation results show that the maximum error of the array element position is controlled within 8mm, the overall positioning error can be within 25mm, and the positioning error of the x and y coordinates of the aircraft can be within 25mm. According to certain optimization criteria, the position accuracy of the ROV is optimized, and the distance measurement error accuracy of the ROV position can be achieved within a 30-meter sphere, and is no more than 30cm (single coordinate direction). BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the regular cube array model inside a sphere;

[0049] Figure 2 Schematic diagram of the neutrino detection test device;

[0050] Figure 3 Schematic diagram of the JUNO positioning system;

[0051] Figure 4 Distance measurement principle;

[0052] Figure 5 Schematic diagram of timing error caused by sound wave amplitude;

[0053] Figure 6 Schematic diagram of spatial geometric positioning;

[0054] Figure 7 Schematic diagram of single point angle error;

[0055] Figure 8 Schematic diagram of system module composition;

[0056] Fig. 9 System hardware composition;

[0057] Fig.10 Schematic diagram of the test layout; DETAILED DESCRIPTION

[0058] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0059] Reference Figure 3 , Figure 8 , Fig. 9 As shown, the device for accurately locating a sound source in an alkylbenzene medium of the present invention comprises a main control computer, an interface extension, a transmitting transducer and a receiving transducer, and each part is connected by a cable; the cable is a multi-core cable, which is retracted and released by a winch and its length is adjusted.

[0060] The main control computer includes a display and control module and a comprehensive processing module, and serves as a data processing and command center at the same time; the display and control module is used to realize the comprehensive human-computer interaction of the positioning system, including the display of target positioning information and the display of ROV sensor parameters, and is specifically used to set the relevant parameters of the transmitting and receiving modules and the ROV running trajectory. The comprehensive processing module is used to realize the core control and positioning solution functions of the positioning system, including distance information solution, position information solution, transmitting and receiving module control, and realizes comprehensive communication with the ROV system, as well as comprehensive communication with the host computer system.

[0061] The interface extension includes a signal generating module and a signal receiving module. The signal generating module is used to realize the generation of the transmission signal waveform and drive the transmission, and the signal receiving module is used to realize the preprocessing of the received signal and signal detection. It mainly completes the following functions:

[0062] Sending control commands, through the transmitting matching circuit, and through the cable, the transmitting transducer on the ROV transmits ultrasonic waves, including the corresponding control circuit, so that the electrical signal generated by the signal source can be more stable when transmitted to the transducer, reducing the probability of erroneous signals.

[0063] Under the calibration condition, the transmitting transducer at the end of the steel cable transmits an ultrasonic signal through the steel cable via the transmitting matching circuit.

[0064] Receive multiple (tentatively 12 channels, designed as 16 channels) receiving sensors (receiving transducers installed on the inner wall of the large sphere) echo signals, perform signal preprocessing on the multiple signals, including signal filtering, amplification, signal detection, etc., and send the trigger pulse corresponding to each signal back to the main control computer.

[0065] The transmitting transducer converts the electrical signal provided by the interface extension into an acoustic signal to transmit the ultrasonic signal. The receiving transducer converts the received ultrasonic signal into an electrical signal and sends it to the interface extension after primary amplification.

[0066] The transmitting transducer is arranged on the positioned ROV, and the ROV is located in a spherical container filled with alkylbenzene medium; the transmitting transducer transmits the acoustic beacon signal at a set period, and uses a timing synchronization device to simultaneously detect and record the time when the signal reaches the receiving transducer;

[0067] The control commands and attitude information of the ROV system, the commands to the interface extension, the ROV position information display, the ROV attitude display, the auxiliary information display and the ROV related information are synchronously sent to the host computer through the main control computer.

[0068] Complete the calculation of the position and posture of the ROV; send the target point position information and related commands to the ROV system to control the ROV movement.

[0069] Reference Figure 1 As shown, the eight receiving transducers are evenly distributed in a spherical container filled with alkylbenzene medium (refer to Figure 2 The array is located at the eight vertices of the space cube and is used to receive the acoustic signal from the transmitting transducer.

[0070] The method for positioning using the device for accurately positioning a sound source in an alkylbenzene medium of the present invention comprises the following specific steps:

[0071] Step 1: Input the target location point that the ROV is expected to reach in the human-computer interaction interface of the display and control module;

[0072] Step 2: calling the signal generating module through the integrated processing module to drive the transmitting transducer to transmit an ultrasonic signal; then the receiving transducer receives the ultrasonic signal, and processes the ultrasonic signal through the signal receiving module;

[0073] Step 3: The received signal processed in step 2 is estimated by the comprehensive processing module, and the distance between the transmitting transducer and the receiving transducer is calculated according to the multiple sets of delay information;

[0074] The calculation method of the distance between the transmitting transducer and the receiving transducer is as follows: Figure 4 The principle shown is that the transmitting transducer transmits sound waves outward, and the receiving transducer receives sound waves. The timing synchronization device is used to detect and record the time when the signal reaches the receiving transducer, and the time difference between the transmitting transducer transmitting the sound wave and the receiving transducer receiving the sound wave is obtained as t. The receiving time is determined by the moment when the amplitude of the received signal exceeds the threshold value; through the formula S i =υt i , i = 1, 2, 3...8, calculate the distance S between the transmitting transducer and the i-th receiving transducer i , where υ is the propagation speed of sound waves in the medium, t i It represents the time difference between the transmitting transducer transmitting the sound wave signal and the i-th receiving transducer receiving the sound wave signal.

[0075] Reference Figure 5 As shown in the figure, due to the differences in the measurement distance, the incident angle of the ultrasonic wave, the sound propagation medium, etc., the sound wave amplitude obtained by the receiving transducer varies greatly, and the timing error caused by the difference in the sound wave amplitude. Under the same threshold conditions, there is a timing difference t2-t1 at the arrival time of sound waves with different amplitudes, and the resulting timing error will eventually couple into the ranging error. In order to reduce the timing error caused by the threshold difference and improve the ranging accuracy, we adopted the adaptive threshold adjustment technology. By first obtaining the signal amplitude, and then setting the threshold according to the 2 / 3 peak amplitude according to the signal amplitude, the timing difference is reduced to 0 as much as possible to ensure the ranging accuracy.

[0076] The propagation speed of the sound wave in the medium varies with the depth. First, the transmission speed of the sound wave from the transmitting transducer υ0 and the receiving speed of the i-th receiving transducer υ ti , then calculate the average value to get the propagation speed υ, and then calculate the distance S between the transmitting transducer and the i-th receiving transducer by the following formula i :

[0077]

[0078] Step 4: The comprehensive processing module calculates the current position and posture of the ROV based on the information of the distance between the multiple sets of transmitting transducers and receiving transducers;

[0079] Eight receiving transducers are arranged at eight positions (with known coordinates) in the big sphere. When the position of the ROV needs to be calculated, the transmitting transducer (positioning sound source) on the ROV transmits a sound signal, which propagates to multiple pre-arranged receiving transducers. The distance from the positioning sound source to each different receiving transducer is calculated by judging the time difference between the arrival of the sound wave and the emission of the sound signal. The current position information of the transmitting sound source (i.e., the ROV) is then calculated using multiple sets of distance information and the position information of the receiving transducer position coordinate points.

[0080] Reference Figure 6 As shown in the figure, the positioning principle uses the basic geometric space positioning method to realize the coordinate positioning of the target. There are three different reference points P i (x i ,y i ,z i ), (i=1,2,3), to get the position of the target point T(x,y,z), just calculate the signal at two nodes T and P i The propagation time difference between them can then be used to obtain the distance R between the nodes. i =D(T,P i ), through the distance relationship between the target node and the known reference point, we get the following set of equations, and by solving (x, y, z) in the set of equations, we get the position of the target point and realize target positioning.

[0081]

[0082] The specific calculation is as follows: the center of the spherical container filled with alkylbenzene medium is set as the midpoint of the coordinate system, the current position coordinate of the ROV is set as (x, y, z, and the position coordinate is solved by the least squares algorithm to find f(X) = (AX-b) T The minimum point of (AX-b) is the following equation, which is the x, y, and z position coordinates of the spacecraft;

[0083]

[0084] A and b are composed of 4 receiving points and corresponding 4 sets of distance information.

[0085] X=(x,y,z) T ,

[0086]

[0087] Then the simulated annealing method is used to find the optimal solution for the current position information. The function of the simulated annealing algorithm used for positioning to solve the minimum value F is:

[0088]

[0089] Where (x, y, z) is the current position coordinate, (x i ,y i ,z i ) is the coordinate of the ith array element, s i is the distance corresponding to the time delay received by the i-th receiving transducer;

[0090] The optimal solution is obtained by iteratively obtaining the minimum value of the objective function F, so that the maximum error of the receiving transducer position is controlled within 8 mm, the overall positioning error is within 25 mm, and the positioning error of the x and y coordinates of the ROV is within 25 mm.

[0091] Reference Figure 7 As shown, ROV attitude determination: due to the implementation of geomagnetic shielding in the entire test field, the attitude of ROV can only be given by the external measurement method. For the vertical cylindrical ROV, it is planned to arrange 4 transmitting transducers above its shell surface, along its contour edge, in a central symmetrical manner, and arrange 1 transmitting transducer in the center, and 5 transducers constitute a plane transmitting transducer array. Through the positioning test of the transmitting transducer array and the test coordination of the combination of the self-contained high-precision pressure sensor (precision 0.02%), the position and attitude of ROV can be obtained. Because the test position center of the symmetrically arranged 4 attitude test transducers can be mutually verified with the test position of the central sound source positioning transducer, the accuracy of the ROV position test can be improved, and the test position of the 4 transducers can give the attitude information of ROV. Since ROV does not require high accuracy for attitude information, this scheme can meet the test requirements of ROV position and attitude.

[0092] With Δ Σ =30mm position test error to estimate the horizontal attitude angle of ROV. Assuming the ROV radius is 0.15m, the single point angle error is shown as follows Figure 4 As shown, the maximum angle error of a single point is:

[0093]

[0094] Through the composite least squares estimation of 5 measuring points, the attitude error can be given as 10°, which can meet the ROV motion solution requirements.

[0095] Step 5: The comprehensive processing module sends the current position and posture of the ROV obtained in step 4 and the target position point in step 1 to the ROV system control, and the ROV system moves to the target position;

[0096] Step 6: After the ROV reaches the vicinity of the target position, the position and attitude are calculated again until the ROV system hovers stably at the target position, and finally the current target position is sent to the upper computer of the positioning device.

[0097] Reference Fig.10 Pool test shown: This test verifies the ranging and positioning working principles of the acoustic positioning system (hereinafter referred to as the "positioning system"), verifies the effectiveness of the positioning method, examines whether the positioning accuracy can be achieved, and puts forward suggestions for system improvement.

[0098] The acoustic center frequency used in the test is 150kHz, which is consistent with the actual positioning system. Four receiving hydrophones (single layer) and one transmitting transducer are used for ranging and positioning tests, and the positions need to be accurately calibrated using an optical calibration device. The deployment position of the receiving hydrophone is required to be similar to the actual formation used. The ranging and positioning results of the optical calibration device and the positioning system are compared to analyze the causes of the errors.

[0099] Test Principle

[0100] 1. Distance measurement test

[0101] The sound source and the hydrophone are precisely positioned in the pool using an optical calibration device to obtain the accurate distance between the sound source and the hydrophone, and the distance is measured using a positioning system. Multiple sets of distance measurement results are recorded to analyze the system's ranging performance.

[0102] 2. Positioning test

[0103] The sound source and four transducers are precisely positioned in the water pool through an optical calibration device to obtain accurate spatial coordinates of the sound source and the four transducers (establishing x, y, and z coordinates). The four sets of distances (from the sound source to the four transducers) are measured through the positioning system. After obtaining the four sets of distance information, the coordinates of the sound source are calculated through the hydrophone coordinates and compared with the optically calibrated sound source coordinates to obtain positioning error information. The coordinates of the four transducers are kept unchanged, the coordinates of the sound source are changed, and multiple positioning tests are performed to verify the positioning effect.

[0104] 3. Test layout diagram

[0105] The test equipment connection diagram is as follows: Fig. 9 As shown in the figure, four receiving transducers and one transmitting transducer are used in the experiment. The placement of the four receiving transducers is shown in the figure, forming a rectangular receiving array basically located in the same plane. The receiving array is about 7m long and 6.7m wide. The transmitting transducer can be changed at will. The reference origin is shown as the red dot in the figure, which is located in the upper left corner of the figure.

[0106] 4. Test steps

[0107] Place 4 receiving transducers and 1 generating transducer, connect the positioning system and oscilloscope, debug the equipment, and ensure that the system works normally; use the optical calibration device to establish the coordinate system and calibrate the positions of the 4 receiving transducers (coordinates such as Fig.10As shown in the figure); deploy the transmitting transducer and use the optical calibration device to calibrate the position coordinates of the transmitting transducer; use the positioning system to measure the time it takes for the acoustic signal generated by the transmitting transducer to propagate to the four receiving transducers, and calculate four sets of distance information; change the position of the transmitting transducer, use the optical calibration device and the positioning system to perform multiple measurements, and complete data recording.

[0108] 5. Experimental data analysis

[0109] Ranging results analysis

[0110] In this test, the transmitting transducer changed its position 6 times, and the 4 receiving transducers obtained a total of 24 sets of ranging results as shown in the following table:

[0111] Table 1 Ranging results when the transmitting transducer is located at the first position

[0112]

[0113]

[0114] Table 2 Ranging results when the transmitting transducer is located at the second position

[0115]

[0116]

[0117] Table 3 Ranging results when the transmitting transducer is located at the third position

[0118]

[0119]

[0120] Table 4 Ranging results when the transmitting transducer is located at the 4th position

[0121]

[0122] Table 5 Ranging results when the transmitting transducer is located at the 5th position

[0123]

[0124] Table 6 Ranging results when the transmitting transducer is located at the 6th position

[0125]

[0126] Table 7 Relationship between ranging error and distance

[0127]

[0128] From the data in Tables 1 to 6, it can be seen that the ranging stability of the positioning system is very good, the ranging standard deviation is basically kept within 1mm, and the maximum standard deviation does not exceed 4mm. The error between the ranging results of the optical calibration system is mainly caused by the difference between the selected sound speed value and the actual sound speed. The sound speed value selected in this test is 1488m / s.

[0129] It can be seen from Table 7 that the ranging error basically increases with the increase of distance. This is because the signal amplitude weakens with the increase of distance. This test uses a fixed threshold to determine the signal arrival time. When the signal weakens, the detection threshold is too high, which will cause the detected signal arrival time to lag, so the ranging error increases. Since the receiving sensitivity of each hydrophone is different, the error size at the same distance is different.

[0130] 6. Positioning result analysis

[0131] Factors that cause the position solution error of the positioning system include the real-time sound speed error in water, the time error from transmission to reception, and random errors in the test process (including optical calibration error and deployment device error, etc.).

[0132] The main error in the test is caused by the sound speed error. In this test, all errors are compensated by sound speed revision. The compensation method is as follows: the original data obtained by the positioning system is the time T from the emission to the reception of the ultrasonic wave. The revised sound speed C is obtained by optically calibrating the distance S / time T. After averaging, C' is obtained as the real-time sound speed to obtain the revised distance S'. Finally, the source position is solved by the revised distance S'. The sound speed revisions are shown in Tables 8 to 11, and the positioning results and errors are shown in Tables 12 and 13.

[0133] Table 8 Reception 1 Distance Revision

[0134]

[0135] Table 9 Reception 2 Distance Revision

[0136]

[0137] Table 10 Receiving 3 Distance Revision

[0138]

[0139] Table 11 Receive 4 Distance Revision

[0140]

[0141] Table 12 Positioning results

[0142]

[0143] Table 13 Positioning error

[0144]

[0145] It can be seen from Table 13 that, through the simplest error correction, the obtained x and y coordinate errors are basically controlled within 20 mm, and the overall error of (x, y) is basically controlled within 30 mm. In the z coordinate, since the four receiving points are basically located in the same horizontal plane, there is not enough aperture in the z direction, so the error is large. In practice, a cube formation is used, and the error should be effectively controlled.

[0146] 7. Test conclusion

[0147] The ranging results have good stability. The corrected ranging error is basically controlled within 20mm. The overall positioning error in the x and y directions can be controlled within 30mm, meeting the precise positioning requirements of ROV.

[0148] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for positioning a sound source in an alkylbenzene medium by using a precise positioning device for a sound source, the precise positioning device for a sound source in an alkylbenzene medium comprising a main control computer, an interface extension, a transmitting transducer and a receiving transducer, wherein the various parts are connected by cables; The main control computer includes a display and control module and a comprehensive processing module, the display and control module is used to realize the comprehensive human-computer interaction of the positioning system, and the comprehensive processing module is used to realize the core control and positioning solution functions of the positioning system; The interface extension includes a signal generating module and a signal receiving module, wherein the signal generating module is used to realize the generation of the transmission signal waveform and drive the transmission, and the signal receiving module is used to realize the preprocessing of the received signal and the signal detection; The transmitting transducer is arranged on the positioned ROV, and the ROV is located in a spherical container filled with alkylbenzene medium; the transmitting transducer transmits the acoustic beacon signal at a set period, and uses a timing synchronization device to simultaneously detect and record the time when the signal reaches the receiving transducer; The eight receiving transducers are evenly distributed on the inner wall of a spherical container filled with alkylbenzene medium, and the array positions are respectively located at the eight vertices of a space cube, for receiving acoustic signals from the transmitting transducer; The cable is a multi-core cable, which is retracted and adjusted in length by a winch; The display and control module includes the display of target positioning information and the display of ROV sensor parameters, which are used to set the relevant parameters of the transmitting and receiving modules and the ROV running track; The comprehensive processing module includes distance information calculation, position information calculation, and transmitting and receiving module control, and realizes comprehensive communication with the ROV system and comprehensive communication with the host computer system; The method for positioning the sound source accurate positioning device in the alkylbenzene medium comprises the following specific steps: Step 1: Input the target location point that the ROV is expected to reach in the human-computer interaction interface of the display and control module; Step 2: calling the signal generating module through the integrated processing module to drive the transmitting transducer to transmit an ultrasonic signal; then the receiving transducer receives the ultrasonic signal, and processes the ultrasonic signal through the signal receiving module; Step 3: The received signal processed in step 2 is estimated by the comprehensive processing module, and the distance between the transmitting transducer and the receiving transducer is calculated according to the multiple sets of delay information; The method for calculating the distance between the transmitting transducer and the receiving transducer in the step 3 is as follows: using a timing synchronization device to detect and record the time when the signal of the receiving transducer arrives, and obtaining the time difference t between the transmitting transducer transmitting the sound wave signal and the receiving transducer receiving the sound wave signal, and the receiving time is the time when the amplitude of the receiving signal reaches the threshold value; The threshold value is an adaptive threshold value, which first obtains the amplitude of the transmitting signal of the transmitting transducer, and then sets the 2 / 3 peak amplitude of the transmitting signal amplitude as the threshold value; Then, by formula S i =υt i , i = 1, 2, 3...8, calculate the distance S between the transmitting transducer and the i-th receiving transducer i ,in, υ is the propagation speed of sound waves in the medium, t i It represents the time difference between the transmitting transducer transmitting the sound wave signal and the i-th receiving transducer receiving the sound wave signal; The propagation speed of the sound wave in the medium varies with the depth. First, the transmission speed of the sound wave from the transmitting transducer υ0 and the receiving speed of the i-th receiving transducer υ ti , then calculate the average value to get the propagation speed υ, and then calculate the distance S between the transmitting transducer and the i-th receiving transducer by the following formula i : Step 4: The comprehensive processing module calculates the current position and posture of the ROV based on the information of the distance between the multiple sets of transmitting transducers and receiving transducers; In step 4, the precise spatial position of the ROV is obtained in real time according to the measured distance between the transmitting transducer and the receiving transducer on the ROV and the corresponding geometric position; the center of the spherical container filled with alkylbenzene medium is set as the midpoint of the coordinate system, and the current position coordinate of the ROV is set as (x, y, z). The position coordinate is solved by the least squares algorithm to obtain f(X)=(AX-b) T The minimum point of (AX-b) is the following equation, which is the x, y, and z position coordinates of the spacecraft; A and b are composed of 4 receiving points and corresponding 4 sets of distance information. X=(x,y,z) T , Then the simulated annealing method is used to find the optimal solution for the current position information. The function of the simulated annealing algorithm used for positioning to solve the minimum value F is: Where (x, y, z) is the current position coordinate, (x i ,y i ,z i ) is the coordinate of the ith array element, s i is the distance corresponding to the time delay received by the i-th receiving transducer; The optimal solution is obtained by iteratively obtaining the minimum value of the objective function F, so that the maximum error of the receiving transducer position is controlled within 8 mm, the overall positioning error is within 25 mm, and the positioning error of the x and y coordinates of the ROV is within 25 mm; Step 5: The comprehensive processing module sends the current position and posture of the ROV obtained in step 4 and the target position point in step 1 to the ROV system control, and the ROV system moves to the target position; Step 6: After the ROV reaches the vicinity of the target position, the position and attitude are calculated again until the ROV system hovers stably at the target position, and finally the current target position is sent to the upper computer of the positioning device.

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