Flexible launch array directivity on-lake test method based on integration of underwater robot and self-contained hydrophone

Abstract

The invention relates to the technical field of sonar directivity testing, in particular to a flexible launch array directivity on-lake testing method based on integration of an underwater robot and a self-contained hydrophone, the underwater robot and the self-contained hydrophone are subjected to advantage integration, and through underwater robot path planning, autonomous cruise and data recording, a flexible launch array directivity on-lake testing method based on integration of the underwater robot and the self-contained hydrophone is obtained. The unmanned closed-loop data test is realized, the robot carries out full-automatic navigation and real-time underwater information recording by changing the motion mode and fixing the flexible launch array, the acquired data volume can be greatly improved, the requirements on a large-scale slewing mechanism and a fixing clamp are reduced, and the test efficiency is improved. The problems that the angle and the sonar state are not synchronous in the rotating process and the angle resolution is low in the vertical measurement process are solved, and the precision of the directivity measurement result of the flexible transmitting array can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sonar directivity test, and in particular to a lake test method for the directivity of a flexible transmitting array integrated with an underwater robot and a self-contained hydrophone. BACKGROUND

[0002] At present, sonar has been widely equipped in various ships, ocean unmanned vehicles and ocean instruments and equipment, wherein, as a typical sonar device, a large-aperture flexible transmitting array is usually carried by a water surface ship and used for underwater long-range detection, and the performance and stability thereof play a decisive role in the execution of a task. The directivity, including horizontal directivity and vertical directivity, is a basic item for measuring the acoustic performance of a sonar array, and is usually measured in an anechoic tank and an open water area on a lake. Due to the size of the anechoic tank and the performance of the anechoic member, all large-aperture, large-weight and medium-low frequency sonar arrays currently in the research, production and other stages need to be measured for directivity on a lake. An accurate and efficient measurement method is a basic guarantee for evaluating the performance of sonar, and a traditional lake sonar array directivity measurement mode refers to an anechoic tank, uses a large lifting and hoisting mechanism, cooperates with hoisting equipment, and carries out test work according to standard methods, which requires that the measured sonar array and the lifting and rotating mechanism are rigidly connected, and the acoustic center of the sonar array and the rotating shaft are consistent. For the measurement of a special array structure or a vertical large-aperture flexible transmitting array, due to the factors that the acoustic center cannot be known in advance, the rotation lags, and the flexible transmitting array cannot be horizontally hung, the traditional measurement mode cannot meet the accurate measurement of the directivity of the flexible transmitting array, and there are problems such as insufficient angle resolution, poor measurement accuracy and low efficiency. SUMMARY

[0003] In view of the deficiencies in the prior art, the present application aims to provide a lake test method for the directivity of a flexible transmitting array integrated with an underwater robot and a self-contained hydrophone, which can improve the test efficiency and accuracy, reduce the influence of human factors and operation errors on the test results, and fill the gap in the lake measurement capability of the existing large-aperture sonar array, and has important application value.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a lake test method for the directivity of a flexible transmitting array integrated with an underwater robot and a self-contained hydrophone, comprising the following steps: S1, obtaining relevant information of the measured flexible transmitting array and sound field arrangement information; S2, synchronizing time and setting parameters for the underwater robot and the self-contained hydrophone; S3, obtaining information recorded by the underwater robot and the self-contained hydrophone within a specified range of directions when the flexible transmitting array is continuously working; S4, calculating the directivity of the flexible transmitting array at the corresponding measurement frequency according to the received acoustic signals of the self-contained hydrophone and the corresponding underwater position information.

[0005] In some embodiments, in step S1, the acquired information about the measured flexible transmitting array includes geometric dimensions, acoustic center, and transmitting signal form.

[0006] In some embodiments, in step S1, the acquired acoustic field arrangement information includes the zero position direction, water entry depth, coordinate position, and water depth of the measured flexible transmitting array.

[0007] In some embodiments, in step S2, the internal clock of the underwater robot and the self-contained hydrophone are synchronized by using the same computer.

[0008] In some embodiments, the parameter settings of the underwater robot include the planned underwater path, running speed, real-time depth and position record, and the parameter settings of the self-contained hydrophone include the sampling rate, sampling duration, and gain.

[0009] In some embodiments, the underwater robot is a tethered underwater robot or an autonomous underwater robot.

[0010] In some embodiments, in step S3, the flexible transmitting array continuously emits periodic signals or continuous signals in a fixed mode, the underwater robot moves at a uniform speed along the planned path, the self-contained hydrophone is fixedly arranged on the body of the underwater robot, the received acoustic signals are recorded, and the underwater position information is recorded by the self-contained sensor of the underwater robot.

[0011] In some embodiments, in step S4, the depth and distance information recorded by the underwater robot at different times are converted into the direction of the measured flexible transmitting array, the recorded acoustic signals of the self-contained hydrophone are corresponded with the calculated direction based on time, the amplitude of the acoustic signals is calculated and corrected to 1m distance, the amplitudes of the transmitting signals at different directions are normalized, and the directivity measurement results of the flexible transmitting array are obtained.

[0012] Compared with the prior art, the present application has the beneficial effects that: based on the strong maneuverability of the underwater robot, the self-contained hydrophone is not bound by the traditional cable, the design combines the advantages of the two, through underwater robot path planning and position-sound signal synchronous data recording, unmanned closed-loop data testing is realized, human factors and operation errors can be reduced, the flexible launch array is kept stationary, full-automatic navigation and real-time underwater information recording are performed by the robot, the amount of data obtained can be greatly improved, the demand for large-scale rotating mechanism and fixed clamps is reduced, the problems of out-of-sync of the rotation process angle and the sonar state and low angle resolution in vertical measurement are avoided, the accuracy of the flexible launch array directivity measurement result can be effectively improved, the present method is a beneficial improvement on the current lake measurement capability of large-aperture flexible launch array directivity, and has important application value.

[0013] The details of one or more embodiments of the present application are presented in the following drawings and description to make the other features, objectives and advantages of the present application more clear, simple and easy to understand, and to make the present application more fully described and understood through the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A schematic diagram of the test method system of the present application is shown.

[0015] In the figure: 1, fixed laying mechanism; 2, connecting rod; 3, flexible rigging; 4, flexible launch array; 5, self-contained hydrophone; 6, underwater robot body; 7, control cable; 8, vertical travel path; 9, horizontal travel path. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0017] In the conventional lake sonar array directivity measurement method, the measured flexible launch array needs to be rigidly connected with the lifting rotating mechanism, and the acoustic center needs to be strictly aligned with the rotating shaft. However, when facing a vertical large-aperture flexible launch array, the acoustic center cannot be accurately calibrated in advance, and the spatial matching of the rotating shaft and the acoustic center is significantly deviated due to the influence of the dynamic deformation of the flexible structure. At the same time, the conventional method relies on a fixed hydrophone array or a single moving track to collect sound field data, resulting in limited azimuth angle coverage and inability to achieve high-resolution spatial sampling. Such a method is prone to angle positioning errors due to mechanical rotation lag during the test process, and the non-uniformity of the sound signal propagation path is further reduced due to the influence of water environment disturbance, thereby reducing the measurement accuracy.

[0018] If the above problems are not solved, the sonar array directivity measurement error will directly affect the sonar system beamforming and target detection performance, leading to the increase of false alarm rate of underwater long-range detection and the decrease of positioning accuracy. In addition, the inefficient test process is difficult to meet the rapid iteration verification requirements of large aperture flexible transmitting array, prolongs the research and development cycle, and increases the cost of lake test. The data distortion under the coupling effect of environmental disturbance and mechanical error may cover up the inherent defects of the transmitting array, affecting the reliability evaluation of sonar equipment.

[0019] In the face of the above problems, the present application first considers the problem of dynamic shift of acoustic center in traditional method leading to the failure of matching of rotary shaft. Since the acoustic center of flexible transmitting array cannot be pre-calibrated and there is dynamic deformation, the present application realizes that it is necessary to avoid relying on the mechanical structure of fixed rotary shaft and acoustic center alignment. In this regard, the present application explores the dynamic acquisition of acoustic field data to replace the mechanical rotation scheme, in which the underwater robot carries the hydrophone to move in multiple directions, eliminating the spatial matching error caused by rigid docking. For the problem of insufficient azimuth angle coverage, the present application analyzes the feasibility of using autonomous mobile platform to record acoustic signals continuously, realizes omnidirectional azimuth angle coverage by planning underwater path, and improves the spatial sampling density. In addition, the time synchronization error caused by mechanical rotation lag in traditional method, the present application proposes to accurately associate the underwater robot position information and hydrophone acoustic signal through time synchronization mechanism, avoiding the phase deviation caused by equipment response delay.

[0020] In this regard, as shown in Figure 1 The present application proposes a flexible transmitting array directivity lake test method based on underwater robot and self-contained hydrophone integration, the steps of which are: obtaining the relevant information of the measured flexible transmitting array and the sound field arrangement information; time synchronization and parameter setting of underwater robot and self-contained hydrophone; obtaining the information recorded by underwater robot and self-contained hydrophone within the specified range of azimuth during the continuous operation of flexible transmitting array; calculating the directivity of flexible transmitting array corresponding to the measured frequency according to the received acoustic signal of self-contained hydrophone and the corresponding underwater position information.

[0021] The underwater robot refers to a programmable control underwater submerged device, and can be specifically implemented by a cable remote control or autonomous navigation type underwater robot, moves in an underwater position through preset path planning, is used for carrying a self-contained hydrophone to dynamically collect sound field data, and solves the problem that a traditional fixed lifting rotary mechanism cannot adapt to the dynamic measurement demand of a flexible launch array. The self-contained hydrophone refers to a hydroacoustic signal collection device with independent data storage function, and can be specifically implemented by a hydrophone with a built-in storage module and a high-precision clock, synchronously records sound signals by being fixedly installed on the underwater robot body, and avoids signal interference and position deviation caused by a traditional hoisting device. The time synchronization refers to time calibration of internal clocks of the underwater robot and the self-contained hydrophone, and is specifically implemented by sending a unified time reference signal to the two by using the same computer, ensures that the recorded sound signals and underwater position information have time consistency, and solves the data matching error problem caused by traditional asynchronous operation of multiple devices. The parameter setting includes an underwater robot motion path, a speed and a hydrophone sampling rate, and specifically presets a navigation track, a uniform speed motion mode and a sampling frequency and time length of the hydrophone of the underwater robot through a computer software, ensures the cooperativity of sound signal collection and position recording, and improves the measurement efficiency. The specified azimuth range refers to a measurement region preset with the measured flexible launch array as a center, and specifically covers a target azimuth angle by underwater robot motion along an arc or straight line path, realizes multi-angle sound field data collection, and solves the problem of insufficient angle resolution of a fixed rotary mechanism in a traditional method. The sound signals and underwater position information refer to sound pressure data recorded by the self-contained hydrophone and depth and coordinates fed back by the underwater robot in real time, and are specifically associated through a time stamp, are used for calculating sound signal amplitudes in different azimuths, and eliminate the measurement error caused by sound center deviation in a traditional method. The calculation of the directivity of the flexible launch array refers to distance correction and normalization processing of the sound signal amplitude, specifically corrects the measurement value to a 1-meter reference distance by using a sound propagation loss model, and then normalizes based on the maximum response direction, directly outputs a directivity function, and solves the problem of insufficient precision caused by rigid installation in a traditional method.

[0022] The core innovation of the present application is that the underwater robot carries the self-contained hydrophone to dynamically collect multi-azimuth sound field data, and replaces the rigid installation mode of the traditional large lifting rotary mechanism by combining time synchronization and parameter cooperative control, to realize high-precision and high-efficiency measurement of the directivity of the flexible launch array.

[0023] The working process and principle of the present application include vertical directivity measurement and horizontal directivity measurement. In the vertical directivity measurement, the flexible launch array 4 is connected to the connecting rod 2 of the fixed laying mechanism 1 through the flexible rigging 3, and according to the requirements of free field measurement conditions or hydrostatic pressure, the water depth of the flexible launch array 4 can be changed by adjusting the length of the flexible rigging or the connecting rod. The testers synchronized the underwater robot and the self-contained hydrophone 5 on the shore using a computer, calculated the free field remote measurement conditions according to the measurement requirements, and set the underwater robot's parameters such as running speed, travel path, real-time depth and position recording rate, and the self-contained hydrophone's sampling rate, sampling duration and gain. After setup, the self-contained hydrophone is fixed to the underwater robot body 6 near the head using a clamp, avoiding the thrusters. The underwater robot is required to have underwater path planning, visual ranging, and high-precision underwater positioning capabilities.

[0024] The testers deployed the underwater robot with the self-contained hydrophone fixed in place into the water. They operated the robot to navigate to the predetermined coordinates and wait for instructions via control line 7. They operated the flexible transmitter array to continuously transmit periodic or continuous signals in a fixed mode. The underwater robot was then started to navigate along the planned vertical travel path 8 and automatically returned to the destination after reaching it.

[0025] The testers processed the underwater robot's location log file and the acoustic data recorded by the self-contained hydrophone. First, they converted the depth and distance information recorded by the underwater robot at different times into the orientation of the flexible transmitter array under test. Then, using time as a reference, they mapped the acoustic signal recorded by the self-contained hydrophone to the calculated orientation and plotted them on the same coordinate axis. They calculated the amplitude of the acoustic signal recorded by the hydrophone and corrected for the loss caused by the sound wave propagation distance. They obtained the amplitude of the transmitted signal at a distance of 1m from the equivalent sound center of the flexible transmitter array under test at different orientations. After normalization, they obtained the directivity measurement results of the flexible transmitter array.

[0026] Based on the above method, when performing horizontal pointing measurement, it is only necessary to set the underwater robot's path to the horizontal travel path 9, and the other operation methods are the same.

[0027] Through the above-described scheme, this application achieves high-precision measurement of the directivity of a large-aperture flexible transmitter array. By employing an underwater robot carrying a self-contained hydrophone for dynamic measurement, the inaccuracies caused by acoustic center offset and mechanical rotation errors in traditional fixed measurements are avoided. The flexible mobility of the underwater robot enables omnidirectional measurement coverage, increasing spatial sampling density. The timing synchronization mechanism ensures precise correspondence between position information and acoustic signals, eliminating time synchronization errors. This method not only improves measurement accuracy but also significantly enhances testing efficiency, providing strong support for the rapid iterative verification of flexible transmitter arrays. Furthermore, because it does not rely on a fixed mechanical structure, this method is applicable to flexible transmitter arrays with various special array structures, exhibiting broad applicability. This application further proposes to obtain relevant information about the flexible transmitter array under test, including its geometric dimensions, acoustic center, and transmitted signal type.

[0028] The geometric dimensions are obtained through three-dimensional measuring instruments to acquire the shape data of the transmitting array, the acoustic center is calculated using an acoustic simulation model to obtain its spatial coordinates, and the transmitted signal format includes pulse width, modulation method, and frequency components. The geometric dimensions are used to plan the coverage area of ​​the underwater robot's motion trajectory, the acoustic center serves as the reference point for azimuth angle calculation, and the transmitted signal format provides a basis for setting matching sampling parameters for the self-contained hydrophone.

[0029] Specifically, during implementation, geometric measurement data is input into the underwater robot control system to generate an arc-shaped motion path adapted to the physical dimensions of the transmitting array, ensuring the hydrophone moves within the effective sound field. The coordinates of the sound center serve as a spatial reference point, establishing a coordinate system with the real-time position data recorded by the underwater robot to eliminate azimuth errors caused by the suspension offset of the transmitting array. Specific parameters of the transmitted signal format are synchronously transmitted to the self-contained hydrophone, enabling it to automatically configure the bandpass filter cutoff frequency and integration time window. By accurately acquiring these three parameters, the spatial position of the transmitting array, the trajectory planning, and the signal acquisition parameters are coordinated and optimized, ensuring that subsequent azimuth angle calculation errors are controlled within a preset range.

[0030] As a preferred embodiment, the solution of this application is specifically implemented as follows: When obtaining relevant information about the flexible transmitting array under test, this includes its geometric dimensions, acoustic center, and transmitted signal type. Specifically, the geometric dimensions can include the length, width, and thickness of the flexible transmitting array. The acoustic center refers to the center point of sound wave radiation, which can be obtained through calculation or experimental measurement. The transmitted signal type can be a continuous wave signal or a pulse signal, where the continuous wave signal can be a sine wave; the pulse signal can be a square wave pulse.

[0031] Through the above technical solution, this application can accurately obtain the key parameters of the flexible transmission array under test, providing necessary basic data for subsequent directivity testing. Therefore, testers can rationally plan test schemes and select appropriate test equipment and parameter settings based on this information, thereby improving the accuracy and efficiency of the test. Furthermore, obtaining the transmitted signal format helps in signal matching and analysis during subsequent data processing, improving the accuracy of directivity calculations. This application further proposes that the acquired acoustic field layout information includes the zero-position direction of the measured flexible transmitting array, the water depth, the coordinate position, and the water depth.

[0032] Among them, the zero-position direction serves as the reference direction for the sound field, used to determine the initial orientation of the transmitting array; the water depth is obtained through a pressure sensor or a preset calibration value, used to correct the propagation path of the sound signal; the coordinate position is recorded through GPS or an underwater positioning system, providing an absolute spatial reference for the transmitting array; and the water depth is obtained through a depth sounder or preset hydrological data, used to assess sound field reflection interference.

[0033] Specifically, when setting up the test sound field, an azimuth coordinate system is first established based on the zero-position direction, combined with the geometric dimensions of the transmitting array and the position of the sound center. The water depth is monitored in real-time or by inputting preset parameters to ensure that the sound field propagation of the transmitting array at different test frequencies meets the far-field conditions. The coordinate position is recorded using positioning equipment, recording the latitude, longitude, and elevation information of the transmitting array to provide a spatial reference for underwater robot path planning. The water depth is determined through on-site measurement or historical data retrieval to determine whether the test area meets the non-reflection boundary conditions. By synchronously acquiring these parameters, a precise sound field spatial model can be constructed, eliminating the influence of environmental factors on sound signal propagation, thereby improving the angular resolution and data reliability of directional measurements.

[0034] As a preferred embodiment, the solution of this application is specifically implemented as follows: When acquiring sound field layout information, this includes the zero-position direction of the flexible transmitting array under test, its water immersion depth, coordinate position, and water depth. Specifically, this can be done through the following steps: First, determine the null orientation of the flexible transmitting array under test. This can be done using a compass or other orientation measuring equipment. The null orientation is typically defined as the direction of the main lobe of the acoustic wave emitted by the flexible transmitting array.

[0035] Secondly, the immersion depth of the flexible emission array in the water is measured. This can be achieved using a depth sensor or a pressure sensor. Accurate measurement of the immersion depth is crucial for subsequent acoustic field analysis.

[0036] Next, the coordinates of the flexible array are recorded. This can be done using the Global Positioning System (GPS) or other positioning technologies. The coordinates include longitude, latitude, and altitude information.

[0037] Finally, measure the water depth. This can be done using a sonar depth sounder or other depth measurement equipment. Information about the water depth is crucial for understanding the environment in which sound waves propagate.

[0038] Through the above technical solution, this application can accurately obtain key parameters of the sound field arrangement, providing necessary basic data for subsequent directivity testing of the flexible transmission array. This information helps to correctly set up the test environment, ensuring the accuracy and reliability of the test results. Therefore, testers can better understand the propagation characteristics of sound waves in specific aquatic environments, thereby optimizing the testing process and improving measurement accuracy. This application further proposes using the same computer to synchronize the internal clock of the underwater robot and the self-contained hydrophone.

[0039] The internal clock synchronization is achieved by sending a time calibration signal from a computer to both the underwater robot and the self-contained hydrophone, ensuring that the initial time and time step of their internal clocks are consistent. Parameter settings include planning the underwater path, operating speed, real-time depth and location recording, as well as configuring the sampling rate, sampling duration, and gain. The time calibration signal can be implemented using GPS synchronization or a network time protocol. For example, the NTP protocol can be used to synchronize the computer with a standard time source, and then calibration commands can be sent to the devices via wired or wireless communication interfaces.

[0040] Specifically, the computer sends path planning commands to the underwater robot via a communication interface, and simultaneously sends sampling parameter configuration commands to the self-contained hydrophone. During time synchronization, the computer uses the current system time as a reference and writes it into the underwater robot's control module and the hydrophone's storage module, eliminating accumulated time errors between the devices. As the underwater robot moves along the planned path, its real-time recorded depth and position information, along with the acoustic signals collected by the hydrophone, are all marked with a unified timestamp. Through timestamp matching, the acoustic signals are precisely correlated with the underwater robot's trajectory, avoiding orientation calculation errors caused by clock deviations.

[0041] As a preferred embodiment, the solution of this application is implemented as follows: When synchronizing the underwater robot and the self-contained hydrophone, a high-precision time server is used as the master clock source. This time server maintains synchronization with the National Time Service Center via Network Time Protocol (NTP). The underwater robot and the self-contained hydrophone are connected to this computer via wired or wireless networks. The time server periodically sends time synchronization signals to the underwater robot and the self-contained hydrophone to ensure that their internal clocks are consistent with the master clock. Specifically, the time synchronization process includes the following steps: First, the time server sends a timestamp request to the underwater robot and the self-contained hydrophone; second, the underwater robot and the self-contained hydrophone immediately return their respective current timestamps upon receiving the request; then, the time server calculates the transmission delay and sends correction information; finally, the underwater robot and the self-contained hydrophone adjust their respective internal clocks according to the received correction information. This process is repeated periodically to ensure time synchronization accuracy during long-term testing.

[0042] Through the above technical solution, this application achieves high-precision time synchronization between the underwater robot and the self-contained hydrophone. This ensures that the acoustic signal data and position information collected during the measurement process can accurately correspond, improving the accuracy of the directional measurement of the flexible transmission array. Furthermore, using the same computer for time synchronization simplifies the configuration of the testing equipment and improves testing efficiency. Simultaneously, this method also enhances the reliability of the testing system and reduces measurement errors that may result from time asynchrony between multiple devices. This application further proposes parameter settings for underwater robots, including underwater path planning, running speed, real-time depth and position recording, and parameter settings for self-contained hydrophones, including sampling rate, sampling duration and gain.

[0043] The underwater path planning ensures coverage of the designated azimuth range of the flexible transmission array under test through a preset robot motion trajectory; the operating speed is set to a constant motion mode to maintain a constant data acquisition time interval; real-time depth and position recording achieves continuous updates of three-dimensional spatial coordinates through pressure sensors and an inertial navigation unit. The sampling rate of the self-contained hydrophone is set to be more than twice the highest frequency of the transmitted signal, the sampling duration covers the complete working cycle of the flexible transmission array, and the gain is set to a middle level to avoid signal saturation.

[0044] Specifically, when the underwater robot moves at a constant speed along a preset path, its onboard depth sensor records the diving depth at a preset time frequency, and the inertial navigation unit simultaneously records the latitude and longitude coordinates, forming a time-space position mapping table. The self-contained hydrophone continuously collects acoustic signals at a set sampling rate, ensuring complete recording of the full waveform data of the periodic signals. Through timestamp alignment, a synchronization relationship is established between the robot's position data and the hydrophone's acoustic data, enabling each acoustic signal sample to be associated with precise azimuth and distance information, providing a high-precision spatial reference for subsequent directional calculations.

[0045] Through the above technical solutions, this application achieves precise parameter control of the underwater robot and the self-contained hydrophone, ensuring the accuracy and consistency of data acquisition during testing. This improves the reliability and repeatability of the directional testing of the flexible transmitter array. Furthermore, by rationally setting the operating path and speed, more comprehensive spatial sampling data can be obtained, thereby improving the angular resolution and accuracy of directional measurement. Simultaneously, appropriate sampling rate and sampling duration settings ensure complete acquisition of the acoustic signal, providing a sufficient information foundation for subsequent data analysis. This application further proposes that the underwater robot is a tethered underwater robot or an autonomous underwater robot.

[0046] Among them, the tethered underwater robot is connected to the surface control terminal via a cable, and its movement trajectory is monitored and adjusted in real time, making it suitable for short-distance, high-precision path tracking scenarios; the autonomous underwater robot has a built-in navigation and propulsion system, enabling it to execute preset path planning and independently complete long-distance movements, suitable for testing needs in large-scale, complex water conditions. Both types of underwater robots are matched with the path, running speed, and position recording parameters planned in the preceding claims, where the path planning parameters are set to the motion mode corresponding to the robot type, for example, the tethered underwater robot uses a segmented polyline path, and the autonomous underwater robot uses a spiral expansion path.

[0047] Specifically, when obstacles exist in the test waters or a fan-shaped area needs to be covered, the autonomous underwater vehicle (AUV) achieves multi-angle azimuth coverage through a pre-programmed sequence, and its movement trajectory is recorded as continuous azimuth data. When the test area is limited and real-time path adjustments are required, the tethered underwater vehicle transmits control commands via cable to achieve millimeter-level position correction. The selection of the two robot types is determined based on the water depth, test range, and measurement accuracy requirements, and their operating speed parameters are set to constant values ​​that match the robot's dynamic characteristics. By matching the robot type with the path planning parameters, the density of azimuth data acquisition and measurement efficiency are improved, while avoiding azimuth loss or trajectory deviation caused by insufficient robot mobility.

[0048] As a preferred embodiment, the solution of this application is implemented as follows: the underwater robot can be either a tethered underwater robot or an autonomous underwater robot (AUV). The tethered underwater robot is connected to the surface control station via a cable, enabling real-time data transmission and command reception. The AUV, on the other hand, relies entirely on pre-programmed procedures and onboard sensors for underwater navigation and task execution. For example, an AUV equipped with an acoustic positioning system, depth sensors, and an inertial navigation system can be used, allowing it to autonomously navigate along a predetermined path and record its location information.

[0049] Through the above technical solution, this application enables flexible selection of underwater robot types suitable for the testing environment. Tethered underwater robots are suitable for scenarios requiring real-time monitoring and adjustment, while autonomous underwater robots are suitable for long-term independent operation in complex underwater environments. This flexibility improves the adaptability and practicality of the testing method, allowing the selection of the most suitable underwater robot type based on specific testing needs and environmental conditions, thereby improving testing efficiency and data quality. This application further proposes a flexible transmitting array that continuously transmits periodic or continuous signals in a fixed mode, an underwater robot that moves at a constant speed along a planned path, a self-contained hydrophone that is fixedly arranged on the underwater robot body to record the received acoustic signals, and an underwater robot that records its underwater position information through its built-in sensors.

[0050] The flexible transmitter array can transmit either periodic pulse signals or continuously frequency-modulated signals in its fixed mode, with the frequency range of the transmitted signal preset according to the directional requirements of the target. Uniform motion of the underwater robot is achieved through a path planning algorithm, with speed error controlled within a preset threshold. The self-contained hydrophone is fixed to the robot's shell surface using mechanical clamps or embedded mounting slots, with the installation position avoiding the thrusters or moving parts to prevent interference from water flow noise. Underwater position information recording utilizes a combined sensor system, including a depth gauge, a Doppler log, and an inertial navigation unit, with the sampling interval maintaining an integer multiple relationship to the acoustic signal sampling rate.

[0051] Specifically, the flexible transmission array maintains continuous operation during testing, ensuring sound source stability through a fixed transmission mode. An underwater robot moves at a constant speed along a preset trajectory, covering a designated azimuth range of the array under test. Due to the robot's uniform motion, its position information is linearly related to time, facilitating subsequent azimuth calculation. A self-contained hydrophone is rigidly connected to the robot, maintaining synchronized movement to avoid phase errors caused by relative displacement. The acoustic signals collected by the hydrophone are matched with the depth and distance data recorded by the robot using a unified time reference, ensuring that each acoustic signal sample corresponds to precise spatial coordinates. This implementation method enables high-density azimuth sampling, improving the angular resolution and data integrity of directional measurements while avoiding the mechanical lag problems inherent in traditional rotary mechanisms.

[0052] Through the above technical solution, this application achieves efficient measurement of the directivity of a flexible transmitter array. This eliminates the need for complex rotation operations on the flexible transmitter array, avoiding errors that might be introduced during rotation. Simultaneously, the uniform motion and continuous recording of the underwater robot ensure the continuity and integrity of the measurement data. Furthermore, the self-contained hydrophone fixed to the underwater robot simplifies the arrangement of measurement equipment and improves measurement efficiency. The real-time position recording by the underwater robot's built-in sensors provides accurate spatial information support for subsequent data processing and directivity calculation. This application further proposes to calculate the directivity of a flexible transmitter array through the following steps: converting the depth and distance information recorded by the underwater robot at different times into the orientation of the flexible transmitter array under test; using time as a reference, matching the sound signal recorded by the self-contained hydrophone with the calculated orientation; calculating the sound signal amplitude and correcting it to a distance of 1m; and normalizing the amplitude of the transmitted signal under different orientations to obtain the directivity measurement result of the flexible transmitter array.

[0053] Among them, the orientation transformation is achieved through a coordinate transformation algorithm, which maps the three-dimensional coordinates in the underwater robot's motion trajectory to a polar coordinate system with the sound center of the measured flexible transmitting array as the origin, and then calculates the azimuth angle; the time reference synchronization adopts the timestamp after time synchronization to ensure that the recording time of the sound signal strictly corresponds to the underwater robot's position information; the amplitude correction is based on the sound wave propagation attenuation model, which uniformly converts the sound pressure level at different distances to a 1m reference distance; the normalization processing selects the amplitude of the direction of maximum response as the reference and performs proportional conversion on the amplitude of each orientation.

[0054] Specifically, the depth and distance data recorded in real time during the underwater robot's movement are converted into azimuth angles relative to the acoustic center of the measured flexible transmitting array using a coordinate transformation algorithm. This algorithm considers the spatial geometric relationships of the transmitting array's zero-position direction, water depth, and the robot's trajectory. The acoustic signals recorded by the self-contained hydrophone are matched with the azimuth angle data using timestamps to ensure that each acoustic signal sample corresponds to unique azimuth information. After the acoustic signal amplitude is corrected using an attenuation model, the influence of propagation distance differences on the measurement results is eliminated, making data from different azimuths comparable. Normalization processing uses the amplitude of the maximum response direction as a benchmark, converting the amplitude values ​​of each azimuth into relative proportions, ultimately forming a directional pattern. Through these steps, the measurement error problem caused by the inaccurate correspondence between azimuth information and acoustic signals in traditional methods is effectively solved, improving angular resolution and measurement efficiency.

[0055] Through the above technical solution, this application effectively solves the problem of angular resolution being limited by mechanical rotation accuracy in traditional measurement modes. It achieves continuous azimuth data acquisition through dynamic position acquisition and acoustic signal time synchronization technology, avoiding the loss of angular information caused by static discrete sampling. Simultaneously, the azimuth calculation method based on motion trajectory eliminates the influence of equipment installation errors on the measurement results, and distance correction and normalization processes eliminate the interference of propagation attenuation on the directional pattern, significantly improving the measurement accuracy of key parameters such as beamwidth and sidelobe level of the flexible transmission array. This application further proposes to convert the depth and distance information recorded by the underwater robot at different times into the orientation of the flexible transmitting array under test. Using time as a reference, the acoustic signal recorded by the self-contained hydrophone is correlated with the calculated orientation. The amplitude of the acoustic signal is calculated and corrected to a distance of 1m. The amplitude of the transmitted signal under different orientations is normalized to obtain the directional measurement result of the flexible transmitting array.

[0056] Among them, orientation conversion calculates the horizontal and pitch angles of the underwater robot's real-time position relative to the acoustic center of the measured flexible transmitter array through geometric relationships; time reference synchronization ensures that the time axis of the acoustic signal recording and the position information are strictly aligned; distance correction uses an acoustic propagation loss model to compensate the measured amplitude to a 1m reference distance; normalization processing uses the maximum amplitude as the reference to convert the amplitude of each orientation into a relative value.

[0057] Specifically, as the underwater robot carrying a self-contained hydrophone moves along a planned path, its depth sensor and positioning device continuously record three-dimensional coordinate data. Through a coordinate transformation algorithm, the robot's position is converted to a polar coordinate system with the sound center of the measured flexible transmitting array as the origin, and the azimuth parameters are calculated. The time synchronization module precisely matches the position data with the sound signal sampling timestamps, establishing an azimuth-sound pressure correspondence. Subsequently, based on the sound wave propagation attenuation law, the measured sound pressure values ​​in each direction are inversely corrected to a 1m equivalent distance, eliminating the influence of propagation path differences on amplitude. Finally, the maximum sound pressure value is selected as the normalization benchmark, and the relative amplitude values ​​in each direction are calculated and a directivity diagram is plotted. Thus, the azimuth resolution is determined by the robot's motion trajectory density, distance correction ensures amplitude comparability, and normalization improves the consistency of measurement results.

[0058] Through the above technical solution, this application achieves high-resolution dynamic measurement of the directivity characteristics of a flexible transmitting array. By precisely matching the motion trajectory with the acoustic signal in time and space, it effectively solves the problems of large angle sampling intervals and discontinuous azimuth data in traditional rigid rotary mechanisms. The sound field correction method based on real-time position compensation eliminates the influence of propagation distance changes on directivity calculation during motion measurement, significantly improving the accuracy of directivity measurement under complex working conditions.

[0059] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for testing the directivity of a flexible transmitter array on a lake based on an underwater robot and a self-contained hydrophone, characterized in that: The steps are as follows: S1. Obtain relevant information about the flexible transmitting array under test and the acoustic field layout information; S2. Perform time synchronization and parameter settings for the underwater robot and self-contained hydrophone; S3. Acquire information recorded by the underwater robot and self-contained hydrophone within a specified azimuth range when the flexible transmission array is continuously working; S4. Based on the acoustic signal received by the self-contained hydrophone and the corresponding underwater position information, calculate the directivity of the flexible transmitting array at the measurement frequency.

2. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 1, is characterized in that: In step S1, the information obtained about the flexible transmitting array under test includes its geometric dimensions, acoustic center, and transmitted signal type.

3. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 2, is characterized in that: In step S1, the acquired acoustic field arrangement information includes the zero-position direction of the flexible transmitting array under test, the water depth, the coordinate position, and the water depth.

4. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 1 or 3, is characterized in that: In step S2, the same computer is used to synchronize the internal clock of the underwater robot and the self-contained hydrophone.

5. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 4, is characterized in that: The parameter settings for underwater robots include planning underwater paths, operating speed, real-time depth, and location recording. The parameter settings for self-contained hydrophones include sampling rate, sampling duration, and gain.

6. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 5, is characterized in that: The underwater robot mentioned is either a tethered underwater robot or an autonomous underwater robot.

7. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 6, is characterized in that: In step S3, the flexible transmitter array continuously transmits periodic or continuous signals in a fixed pattern. The underwater robot moves at a constant speed along the planned path. The self-contained hydrophone is fixedly arranged on the underwater robot body to record the received sound signals. The underwater robot records its underwater position information through its built-in sensors.

8. The method for testing the directivity of a flexible transmitting array on a lake based on the integration of an underwater robot and a self-contained hydrophone, as described in claim 7, is characterized in that: In step S4, the depth and distance information recorded by the underwater robot at different times is converted into the orientation of the flexible transmitting array under test. Based on time, the acoustic signal recorded by the self-contained hydrophone is correlated with the calculated orientation. The amplitude of the acoustic signal is calculated and corrected to a distance of 1m. The amplitude of the transmitted signal under different orientations is normalized to obtain the directional measurement result of the flexible transmitting array.

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