Dual transducer underwater mapping sonar device and method

Abstract

The application relates to the underwater surveying and mapping technical field, in particular to a double-transducer underwater surveying and mapping sonar device and a method thereof. The device comprises a horizontally rotatable Z axis and a vertically swingable X axis, and two transducers are installed at the two ends of the X axis at a 90-degree included angle. The method comprises the following steps: controlling the Z axis to be positioned by step rotation, controlling the X axis to drive the two transducers to swing and scan at each Z axis angle; collecting sonar echo data and combining attitude information to correct a scanning track; determining a main transducer and a sub-transducer through frequency analysis and constructing a compensation angle control sequence; performing spatial position correction and redundant structure correction on the double-transducer collected data to generate continuous and complete underwater three-dimensional surveying and mapping results; and the application can improve surveying and mapping precision and structural stability in a disturbed environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the underwater surveying technology field, and particularly relates to a double-transducer underwater surveying sonar device and a method thereof. BACKGROUND

[0002] In the underwater surveying technology field, sonar equipment is widely used to obtain information such as underwater terrain, structure contour and target spatial position. Traditional systems mostly use a single transducer combined with a rotating mechanism for scanning, which can realize sonar imaging within a certain range, but in actual application, especially in the presence of water flow disturbance, attitude change or structure obstruction, problems such as scanning blind area, discontinuous structure reconstruction or data overlap error are prone to occur, which limits the surveying accuracy and efficiency. To solve the above problems, the present application designs a double-transducer underwater surveying sonar device and a method thereof. SUMMARY

[0003] The present application solves the technical problems of the prior art and provides a double-transducer underwater surveying sonar device and a method thereof. The device comprises a horizontally rotatable Z-axis and a vertically swingable X-axis, and two transducers are installed at the two ends of the X-axis at an angle of 90°. The method comprises: controlling the Z-axis to be positioned step by step in rotation, controlling the X-axis to drive the two transducers to swing and scan at each Z-axis positioning angle; collecting sonar echo data and correcting the scanning track in combination with attitude information; determining the main and auxiliary transducers through frequency analysis and constructing a compensation angle control sequence; performing spatial position correction and redundant structure correction on the data collected by the double transducers to generate continuous and complete underwater three-dimensional surveying results. The present application can improve the surveying accuracy and structural stability in a disturbed environment.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] A double-transducer underwater surveying method is used for a double-transducer underwater surveying sonar device, wherein the sonar device is installed with a first transducer and a second transducer at a right angle on a vertical rotating mechanism, the vertical rotating mechanism comprises a horizontally rotatable Z-axis and a vertically swingable X-axis, and the underwater surveying method comprises the following steps:

[0006] controlling the Z-axis to be positioned in rotation in the horizontal direction according to a preset step angle;

[0007] controlling the X-axis to drive the first transducer and the second transducer to scan in the vertical direction within a preset swing angle range at each Z-axis positioning angle, so as to collect sonar echo data;

[0008] performing spatial position correction on the sonar echo data according to the rotation position information of the Z-axis and the X-axis, so as to generate corresponding underwater three-dimensional surveying results.

[0009] controlling the X-axis to drive the first transducer and the second transducer to perform vertical scanning within a preset swing angle range, comprising:

[0010] synchronously collecting real-time attitude information during the scanning process, wherein the real-time attitude information comprises a pitch angle, a roll angle and a yaw angle;

[0011] correcting the preset swing angle range according to the real-time attitude information.

[0012] correcting the preset swing angle range according to the real-time attitude information, comprising:

[0013] performing Fourier transform on the real-time attitude information to analyze a dominant frequency and an amplitude of attitude disturbance;

[0014] constructing a resonance compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance according to the dominant frequency and the amplitude, wherein the resonance compensation angle control sequence is a swing angle correction sequence continuously changing with scanning time;

[0015] superimposing the resonance compensation angle control sequence during the swing scanning process of the X-axis driving the first transducer or the second transducer.

[0016] constructing a resonance compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance according to the dominant frequency and the amplitude, comprising:

[0017] extracting the corresponding dominant frequency and amplitude of the first transducer and the second transducer during the X-axis swing scanning process, respectively;

[0018] performing local point cloud construction and grid reconstruction on sonar echo data collected by the first transducer and the second transducer within their scanning periods to form corresponding local spatial structure surfaces;

[0019] in the local spatial structure surface, assigning each grid element with the dominant frequency and the dominant amplitude value of its source beam segment to construct a frequency-amplitude embedded grid;

[0020] calculating the frequency-amplitude distribution stability and the structure surface morphological continuity of the frequency-amplitude embedded grid;

[0021] determining a main transducer and a secondary transducer according to the frequency-amplitude distribution stability and the structure surface morphological continuity, and constructing a resonance compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance according to the scanning trajectory of the main transducer;

[0022] applying the resonance compensation angle control sequence to the swing control of the secondary transducer during the next Z-axis rotation positioning.

[0023] The resonant compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance is constructed according to the main frequency and amplitude, and further comprises:

[0024] Before the sub transducer executes the resonant compensation angle control sequence, the offset amplitude and coverage missing interval of the actual swing trajectory caused by the resonant compensation angle control sequence relative to the preset swing angle range are predicted;

[0025] According to the offset amplitude and coverage missing interval, the scanning angle amplitude of the main transducer is adjusted.

[0026] The spatial position correction of the sonar echo data according to the rotation position information of the Z axis and the X axis comprises:

[0027] The spatial direction projection relationship between the scanning beams is established by using the structure installation mode that the first transducer and the second transducer are fixed at an angle of 90° on the device;

[0028] The sonar echo data obtained by the first transducer and the second transducer at the same Z-axis positioning angle are respectively constructed into local spatial point clouds, and the boundary region and the geometric structure intersection area are extracted;

[0029] Based on the spatial direction projection relationship, the directionality conflict analysis is performed on the boundary region and the geometric structure intersection area, and a redundant reconstruction segment is obtained;

[0030] The structure correction processing is performed on the redundant reconstruction segment to generate single structure information;

[0031] The single structure information and the local spatial point cloud are fused to generate a corresponding underwater three-dimensional surveying result.

[0032] The structure correction processing performed on the redundant reconstruction segment comprises:

[0033] The boundary structure surfaces respectively formed by the first transducer and the second transducer in the redundant reconstruction segment are constructed, and the edge lines thereof in space are extracted;

[0034] The spatial trend difference and geometric offset relationship of the two edge lines in the redundant reconstruction segment are compared;

[0035] Based on the spatial trend difference and offset relationship, an intermediate geometric surface is fitted as a structure reference surface of the redundant reconstruction segment;

[0036] The boundary structure surfaces are respectively subjected to remapping operation to the structure reference surface to obtain single structure information after spatial reconstruction.

[0037] A dual transducer underwater surveying sonar device, the sonar device comprises:

[0038] The vertical rotation mechanism comprises a Z-axis capable of rotating in a horizontal direction and an X-axis capable of vertically swinging relative to the Z-axis, and the Z-axis and the X-axis are connected with each other to form a two-dimensional rotation structure.

[0039] The first transducer and the second transducer are respectively arranged at two sides of the X-axis at a right angle and swing together with the X-axis, and the Z-axis drives the X-axis to rotate step by step around a vertical direction;

[0040] The control module is used for controlling the Z-axis to rotate and position in a horizontal direction according to a preset step angle, and controlling the X-axis to drive the first transducer and the second transducer to scan in a preset swing angle range.

[0041] The data acquisition and processing module is used for acquiring sonar echo data of the first transducer and the second transducer in each rotation posture, and correcting the sonar echo data based on rotation position information of the Z-axis and the X-axis to generate corresponding underwater three-dimensional mapping results.

[0042] The control module is used for synchronously acquiring real-time posture information when the first transducer and the second transducer vertically swing and scan, and dynamically correcting a swing angle range of the X-axis based on the real-time posture information.

[0043] The data acquisition and processing module is used for:

[0044] Analyzing boundary structure deviation of data acquired by the first transducer and the second transducer in a spatial overlapping area at a same Z-axis positioning angle;

[0045] Generating an intermediate fitting surface based on the boundary structure deviation, and mapping data from the two transducers to the intermediate fitting surface to perform structure consistency correction.

[0046] Compared with the prior art, the beneficial effects of the present application are:

[0047] The present application adopts a double-transducer structure arranged at a 90° angle, combines a horizontally rotatable Z-axis and a vertically swingable X-axis, realizes complementary coverage in a vertical scanning direction, and effectively improves spatial integrity of underwater scanning. By acquiring real-time posture information and constructing a resonance compensation angle control sequence based on a dominant frequency and amplitude, a scanning track can be dynamically corrected, and anti-disturbance capability is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0048] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0049] Figure 1 An exemplary application scenario of an embodiment of the present application is shown in the following figure:

[0050] Figure 2 A flowchart of a double transducer underwater mapping method is provided in an embodiment of the present application.

[0051] Figure 3 A schematic diagram of a double transducer arrangement principle is provided in an embodiment of the present application.

[0052] Figure 4 A schematic diagram of a double transducer rotation principle is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be apparently and completely described in conjunction with 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.

[0054] The phrase "embodiment" mentioned in this document means that the specific features, structures or characteristics described in conjunction with the embodiment can be contained in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. The skilled in the art can explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0055] The embodiments of the present application provide a double transducer underwater mapping sonar device and method, which can realize high-resolution and high-coverage underwater three-dimensional mapping in a dynamic environment. Specifically, the device orthogonally installs two transducers on a vertical rotation mechanism, combines a double-axis cooperative control mechanism and echo data fusion processing method, and improves the scanning coverage angle and the spatial consistency of mapping data without increasing the structural complexity.

[0056] Please refer to Figure 1 , which is a schematic diagram of an exemplary application scenario provided in an embodiment of the present application.

[0057] As Figure 1 shown, the double transducer underwater mapping sonar device is applied to underwater mapping, wherein:

[0058] The double transducer underwater mapping sonar device includes a vertical rotation mechanism, which is connected to a horizontally rotatable Z-axis and a vertically swingable X-axis. A first transducer and a second transducer are respectively installed at two ends of the X-axis, and a 90° included angle is formed between the two transducers for covering the detection areas in different directions underwater.

[0059] In the working process, the Z-axis drives the whole X-axis to rotate step by step in the horizontal plane, and the X-axis drives the two transducers to swing reciprocatingly around the axis of the X-axis, so as to realize scanning in a three-dimensional angle range. Since the two transducers are fixedly installed and the directions thereof are perpendicular to each other, complementary detection of the vertical scanning area can be realized without changing the complexity of the structure, and the integrity of the spatial perception coverage is improved.

[0060] Figure 1 The underwater environment medium background is schematically shown in a streamline manner, and the working state of the device is in the water body. The first transducer and the second transducer are arranged at two ends of the X-axis and move around the vertical rotating mechanism, and are used for implementing a three-dimensional direction sonar mapping task, Figure 1 The arrow direction represents the rotating direction.

[0061] Next, a double-transducer underwater mapping method provided by the embodiment of the application will be introduced in combination with the drawings.

[0062] Please refer to Figure 2 The figure is a flowchart of a double-transducer underwater mapping method provided by the embodiment of the application. Figure 2 The method shown in the figure can be applied to a double-transducer underwater mapping sonar device, Figure 2 The method shown in the figure includes the following S1-S3, and the specific steps are as follows:

[0063] S1: Control the Z-axis to rotate and position in the horizontal direction according to a preset step angle;

[0064] In the embodiment, the Z-axis is used for driving the rotating mechanism provided with the X-axis to position step by step, and the step angle can be set according to the mapping resolution and the target area coverage requirement, for example, 10°, 20° or other equal-interval angles. Through step-by-step rotating positioning of the Z-axis, the whole device can complete 360° full coverage or equal-interval scanning preparation of a set area in the horizontal direction. It is ensured that the transducers can accurately sample at each horizontal angle, and a stable scanning reference is provided for subsequent three-dimensional reconstruction.

[0065] S2: At each Z-axis positioning angle, control the X-axis to drive the first transducer and the second transducer to scan in the vertical direction in a preset swing angle range, so as to collect sonar echo data;

[0066] In the embodiment, the X-axis drives the first transducer and the second transducer to reciprocally swing around the center thereof within a preset angle range after each Z-axis positioning is completed. The two transducers are arranged at an angle of 90°, so that the scanning beams thereof are orthogonal to each other, and a larger vertical cross-sectional area can be complementarily covered within one swing cycle. The vertical mapping coverage efficiency at a unit Z-axis angle is improved, and the structural information in different angle directions can be synchronously acquired, which helps to reduce the blind area and enhance the integrity of the mapping structure.

[0067] S3: performing spatial position correction on the sonar echo data according to the rotation position information of the Z-axis and the X-axis, to generate corresponding underwater three-dimensional mapping results;

[0068] In the embodiment, the spatial position correction is performed on the collected sonar echo data according to the real-time position information of each transducer on the Z-axis and the X-axis. Specifically, the projection parameters of the scanning directions of the transducers in the three-dimensional space are constructed in combination with the installation angle relationship of the transducers, and the boundary analysis and spatial conflict identification are performed on the local point clouds collected by the two transducers. For the redundant structural fragments in the intersection area, the intermediate geometric surface fitting and mapping reconstruction processing are performed, to generate a unified structural expression result. This way can effectively solve the inconsistency problem of the structure caused by the direction difference and repeated coverage of the transducers, and improve the boundary continuity and structural consistency of the three-dimensional model.

[0069] For example, the double-transducer arrangement can be understood with reference to Figure 3 and Figure 4 Figure 3 a double-transducer arrangement principle diagram provided by the embodiment of the application, Figure 4 a double-transducer rotation principle diagram provided by the embodiment of the application.

[0070] Figure 3 A double-transducer arrangement structure in the X-axis is shown, in which the two transducers are symmetrically installed at the two ends of the X-axis at an angle of 90°.

[0071] Figure 4 The rotation movement principle of the double-transducer arrangement structure in underwater operation is shown, which specifically includes:

[0072] Step-by-step horizontal rotation of the Z-axis: realizing coverage in different directions;

[0073] Reciprocating vertical swing of the X-axis: driving the two transducers to perform upward and downward angle scanning;

[0074] X-axis scanning is performed once at each Z-axis angle, and the overall space scanning coverage is formed in the form of sectors, rings and solid angles.

[0075] ​Although there are single-transducer rotating scanning structures or multi-transducer collaborative sonar systems in the prior art, there are still great application limitations in complex underwater environments, especially in the presence of water flow disturbance, platform attitude change, equipment sway, etc. The existing structure is prone to problems such as scanning trajectory deviation, data overlap confusion or inaccurate spatial positioning. Taking the traditional single-transducer scheme as an example, when the transducer is omnidirectionally surveyed by a rotating mechanism, if disturbance occurs, the actual swing angle of the transducer beam will deviate from the preset trajectory, resulting in distortion of the projection of sonar data in three-dimensional space. In this case, even if the amount of data collected is sufficient, it is difficult to form a continuous and real spatial structure, especially in large-scale terrain modeling, structure analysis or spatial docking tasks, which will greatly weaken the practicality and accuracy of the system.

[0076] The double-transducer orthogonal arrangement structure adopted in the embodiment effectively avoids the above problems. Two transducers are installed at the two ends of the same vertical swing axis at a 90° angle, and cover the vertical space orthogonally. This structure avoids the formation of scanning blind areas on the one hand, so that the angle region that one transducer may miss can be supplemented by the other transducer; on the other hand, in the disturbance scene, the two groups of data are different in disturbance deviation characteristics due to the difference in beam direction. The embodiment can perform error balancing processing based on the complementarity of the main and auxiliary transducers by comparing, fusing and dynamically adjusting the local structures collected by the two transducers. This geometric structure compensation mechanism is relatively rare in the prior art, and is an innovative design that resists disturbance errors through the structure layout itself.

[0077] Further, in the embodiment, the dominant frequency and amplitude variation trend of the disturbance are extracted through frequency analysis and Fourier modeling means, and combined with the directionality difference of the double transducers. When the scanning range of one transducer deviates due to disturbance, the data collected by the transducer with higher direction stability is used for structure compensation, and a resonance compensation angle control sequence is generated for angle correction in the next scan. So that the double transducers are no longer a simple redundant configuration, but participate in the surveying decision as a collaborative structure with complementary adaptive ability.

[0078] The specific steps of S2 are as follows:

[0079] S2.1: synchronously collecting real-time attitude information in the scanning process, wherein the real-time attitude information includes pitch angle, roll angle and yaw angle;

[0080] Specifically, in order to ensure that the transducer can continuously maintain the spatial accuracy of its beam pointing during the swing scanning process in a dynamic underwater environment, it is necessary to obtain the spatial attitude information of the device platform in real time during the scanning synchronization stage. Due to unpredictable factors such as disturbances, water flow impacts, or slight shifts of the device body in the underwater operation environment, the transducer may produce attitude deviations in pitch angle, roll angle, and yaw angle relative to the reference reference (such as the device installation direction or the world coordinate system), thereby directly affecting the projection accuracy of the sonar data collected by the transducer in the spatial coordinate system. Therefore, in order to avoid geometric distortion or misalignment of data space mapping, the current attitude angle information must be recorded synchronously in each swing scanning action to support the subsequent dynamic angle correction and echo space correction process.

[0081] In the present embodiment, the real-time attitude information is obtained by an inertial measurement unit (IMU) integrated in the transducer carrier body, which is composed of a gyroscope and an accelerometer, and outputs spatial attitude data in three dimensions of pitch angle (Pitch), roll angle (Roll), and yaw angle (Yaw) in real time through a six-axis sensor fusion algorithm. The IMU and the X-axis drive control module establish a synchronous clock mechanism to ensure that the attitude recording process is started before each swing scanning starts, and the attitude trajectory information of the corresponding scanning segment is sealed after the scanning action is completed. In this way, a one-to-one correspondence between the transducer beam trajectory and the attitude change curve can be formed, and a complete time-space mapping chain is established for subsequent dynamic compensation processing.

[0082] Further, the attitude information not only includes angle values at discrete time points, but also records the angular velocity change trend within the continuous sampling time, so that it can be judged whether the current attitude change has periodic disturbance, instantaneous deviation, or structural oscillation. This feature has a basic supporting role in subsequent Fourier analysis and dominant frequency extraction, which helps to identify the functional relationship between the disturbance source and the scanning deviation, and accordingly establishes an active compensation control mechanism. The time stamp of the attitude information acquisition is synchronized and aligned with the sonar sampling, which can be used as an accurate reference variable in the subsequent data fusion process.

[0083] S2.2: correcting the preset swing angle range according to the real-time attitude information;

[0084] Specifically, the theoretical swing angle range of the transducer in performing X-axis swing is set by the control instruction for scanning a certain fixed sector area. However, in actual operation, due to the pitch offset or attitude dynamic change of the device, the actual path of the beam of the transducer in space will deviate from the ideal sector trajectory. If this deviation is not dynamically corrected, it will result in inconsistency between the scanning result and the expected area, which is manifested as echo data projection position error, sparse overlap of point clouds, and missing of local area scanning, etc. Therefore, it is necessary to correct the theoretical swing angle range in advance based on the attitude change trend collected in the previous period before the transducer performs the swing action, so as to guide the actual swing scanning of the beam along the angle trajectory closer to the target space.

[0085] In the embodiment, after receiving the attitude information, the control module first performs fast Fourier transform (FFT) according to the time sequence thereof, extracts the main disturbance frequency component and the corresponding amplitude characteristic in the current period, and constructs a dominant disturbance model based on the spectrum distribution. The model reflects the disturbance trend of the current platform in the pitch and roll directions, and can be used to predict the direction and amplitude of the beam offset that may occur in the next round of scanning. Then, according to the extracted dominant disturbance frequency and angle influence range, a continuously changing resonance compensation angle control sequence is generated, which will be dynamically superimposed into the original control signal in the next round of X-axis swing, thereby forming a "corrected swing angle trajectory". In other words, the transducer does not swing up and down along the preset fixed angle, but introduces a disturbance cancellation term in the control driving, so that the actual swing path is more consistent with the theoretical expectation, thereby offsetting the structural offset caused by environmental disturbance.

[0086] Further, to ensure that the correction effect is controllable, the compensation amplitude and waveform form in the control sequence are fed back and evaluated by the data quality analysis module of the main transducer. If the attitude disturbance is severe, the control trajectory of the auxiliary transducer can perform larger amplitude correction; and when the main transducer scanning is stable and the disturbance influence is small, the compensation range can be correspondingly reduced to avoid introducing additional interference. Through this strategy, a dynamic control strategy based on real-time attitude perception, disturbance trend judgment and transducer state difference can be realized, which can guarantee the spatial coverage range while improving the consistency and structural continuity of the data, forming a scanning mechanism of structure perception-attitude synchronization-angle self-adaptation, which has strong actual realizability and engineering application value.

[0087] The specific steps of S2.2 are as follows:

[0088] S2.2.1: Fourier transform is performed on the real-time attitude information to analyze the dominant frequency and amplitude of the attitude disturbance;

[0089] Specifically, due to the influence of environmental factors such as water flow pulsation, mechanical rebound, wave disturbance and the like during the operation of the underwater platform, the equipment will produce persistent dynamic deviation in the pitch, roll and yaw directions. These disturbances may not necessarily cause severe deviation immediately, but they will accumulate periodically, affecting the correspondence between the actual beam path of the transducer and the theoretical angle. The traditional attitude correction method is mostly based on the instantaneous angle value of the current frame for static correction, which is difficult to capture the frequency structure of the periodic disturbance, resulting in a lagging and local compensation behavior, making it difficult to effectively predict the future attitude trend. Therefore, the present embodiment introduces Fourier transform analysis, aiming to extract the frequency domain structure from the attitude angle sequence in the time domain, identify the dominant disturbance frequency and periodic response amplitude, and thus provide a quantitative basis for subsequent establishment of a dynamic resonance compensation model.

[0090] In the present embodiment, by performing fast Fourier transform on the attitude angle sequence collected by the transducer mounting platform within a period before scanning, the frequency spectrum energy distribution is calculated, and the frequency energy peak point in the frequency spectrum is searched as the dominant disturbance frequency. Combined with the energy amplitude corresponding to the frequency, the amplitude estimation of the disturbance influence in the angle domain is further determined. This analysis process not only extracts the main frequency and sub-frequency of the disturbance behavior, but also quantifies the periodic influence degree. The Fourier analysis process is periodically updated in a sliding window manner, ensuring that the dominant frequency always reflects the current disturbance state, with real-time and dynamic response capability.

[0091] As a preferred, in order to suppress the influence of high-frequency interference introduced by sensor noise, the Fourier transform process adopts windowing preprocessing, and the window function can be Hamming window or Blackman window, which is used to improve the clarity of the spectrum boundary response and avoid false frequency peaks caused by short-term disturbance. In addition, by selecting 3-5 order main frequency components for synthesis modeling, the modeling capability for complex disturbance structure can be improved, providing multi-dimensional support for constructing more stable control curves.

[0092] S2.2.2: constructing a resonance compensation angle control sequence with the same frequency or inverse frequency as the attitude disturbance according to the dominant frequency and amplitude, wherein the resonance compensation angle control sequence is a continuously changing swing angle correction sequence with respect to scanning time;

[0093] Specifically, after obtaining the dominant frequency and periodic amplitude of the attitude disturbance, it cannot be directly used for transducer control compensation, because the influence mode of the disturbance has a time lag and structural nonlinearity, and needs to be combined with the actual dynamic response law of the platform to construct an adaptive control sequence. In order to convert this frequency response into a control signal that can be used for angle correction, the present embodiment designs a resonance compensation control method with the same frequency or inverse frequency as the dominant disturbance frequency. This method generates a time-continuous angle correction trajectory, so that the actual swing path of the transducer is offset in real time during the entire scanning process, to counteract the attitude deviation caused by external disturbance.

[0094] In this embodiment, according to the dominant frequency and disturbance amplitude obtained in the S2.2.1 stage, the control module generates a continuous compensation angle control sequence consistent (in phase) or opposite (out of phase) with the main frequency. This control sequence has a time step frequency consistent with the scan step, and is constructed by a cosine waveform modulation model, the phase, period and initial delay of which can be adjusted to align with the actual swing time axis of the transducer. According to the directionality of the disturbance effect, if the disturbance shows a periodic deviation from the center angle, a same frequency and same phase control strategy can be used; if the disturbance shows a symmetric bending deviation or a structural swing type, a same frequency and opposite phase strategy can be used to achieve the control effect of mutual cancellation of wave peaks and troughs.

[0095] S2.2.3: superimposedly executing the resonance compensation angle control sequence in the process of swinging and scanning of the X-axis driven first transducer or second transducer;

[0096] Specifically, the constructed resonance compensation angle control sequence is not executed as an independent driving signal, but is superimposed with the basic swing control instruction of the X-axis to form a dynamically modified angle trajectory for actually driving the swing action of the first transducer or the second transducer. This angle modification action does not change the total scanning range of the transducer, but only applies a disturbance compensation amount to each instantaneous angle value in the swing process, thereby forming a disturbance cancellation curve substantially different from the original trajectory. The compensation behavior modifies the angle path with minimal instruction changes, while maintaining the original system structure and scanning rhythm unchanged, facilitating control integration and platform adaptation.

[0097] In this embodiment, the X-axis drive motor is driven by a servo control unit, and the input angle signal source is the weighted combination of the original preset swing angle trajectory and the resonance compensation control sequence. The system calculates the current target angle in real time according to the set angle output frequency (such as 20Hz~100Hz) in each micro time step, and transmits the value to the servo controller to achieve precise positioning control. During the swing scanning process of the transducer, its actual trajectory will form a small deviation compared to the uncompensated state, but these deviations will be offset through the interference cancellation principle to counteract external disturbances, and finally the pointing path of the transducer beam in space will be more consistent with the theoretical scanning sector, effectively eliminating the problem of trajectory drift caused by disturbance.

[0098] The specific steps of S2.2.2 are as follows:

[0099] S2.2.2.1: Extract the corresponding dominant frequency and amplitude of the first transducer and the second transducer in the X-axis swing scanning process, respectively;

[0100] Specifically, in order to realize effective primary and secondary transducer division and build differentiated resonance compensation strategy, the actual response of the two transducers to the attitude disturbance in the scanning process needs to be mastered respectively. Due to the fixed 90° angle between the transducers, the propagation paths of their beams in space are different, and the perceived disturbance effects will have spatial projection differences. Even under the same platform, the attitude disturbance may also be different. Therefore, the dominant disturbance frequency and its amplitude characteristics of the two transducers in the actual scanning process should be extracted respectively, thereby providing a basis for subsequent personalized modeling and structure judgment.

[0101] In the present embodiment, for the angle control record and attitude sensor output information of the first transducer and the second transducer in their respective scanning periods, independent frequency domain analysis paths are adopted to perform fast Fourier transform processing to obtain the respective dominant frequency peak and its amplitude characteristics. The frequency and amplitude extraction process is based on the attitude change time sequence, and the extracted results are respectively aligned with the sonar scanning track time axis to establish a data mapping corresponding to the transducer beam-disturbance response. The disturbed stability of different transducers under the current environmental disturbance can be revealed, thereby laying a parameter foundation for subsequent judgment of primary and secondary transducers based on structural stability.

[0102] Further, in order to avoid spectrum shift caused by short-time high-frequency noise or underwater transient wave, a three-window resampling verification mechanism is adopted to verify the time period stability of the spectral main component of each transducer, and only the disturbance components with interference persistence exceeding three consecutive scanning periods are retained, so as to ensure that the extracted results have engineering stability and can support adaptive update of the dynamic control system.

[0103] S2.2.2.2: Local point cloud construction and mesh reconstruction are performed on the sonar echo data collected by the first transducer and the second transducer in their scanning periods to form corresponding local spatial structure surfaces;

[0104] Specifically, in order to realize structure reference in geometric dimension in the judgment process of primary and secondary transducers, the original sonar data collected by the transducers need to be restored to an identifiable spatial structure surface representation. The sonar scanning result is essentially a distance echo sequence, which must be processed through coordinate conversion, spatial interpolation and point cloud splicing, so as to form a point cloud shape in three-dimensional space for structure analysis. Therefore, this step reconstructs the scanning echo obtained by the transducer in a single swing period to construct a local spatial point cloud, and further performs triangular mesh reconstruction to form a local structure surface with topological structure.

[0105] In this embodiment, the collected sonar data is first converted into a scanning sector point set in polar coordinate system according to the X-axis swing angle and Z-axis positioning angle, and then mapped to the Cartesian coordinate system through a conversion function to form a discrete point cloud. Subsequently, a triangulation method based on normal vector orientation is used to reconstruct the grid of the point cloud, generating a local grid structure with spatial topology. The structure surface will serve as a geometric carrier for subsequent frequency-amplitude embedding and continuity analysis. Each transducer generates a local structure surface under its own scanning trajectory, and retains its point cloud density distribution, surface normal trend and other geometric statistical characteristics to support subsequent structure comparison.

[0106] Further, to improve the accuracy of the edge area, an adaptive patch expansion mechanism is used in the grid reconstruction process to weight the fitting of the slope change curvature of the scanning sector boundary, so that the boundary area can still maintain spatial continuity in the presence of interference data, laying a structural foundation for subsequent directional analysis and overlap judgment.

[0107] S2.2.2.3: In the local spatial structure surface, assign each grid cell its dominant frequency and dominant amplitude value from the source beam segment to construct a frequency-amplitude embedded grid;

[0108] Specifically, after obtaining the local structure surface, in order to introduce the disturbance effect into the structure analysis process in a parametric manner, it is necessary to associate the frequency characteristics with the spatial structure data, thereby constructing a structure frequency-amplitude joint model with beam source disturbance information. Traditional grid data only reflects the geometric shape and cannot reflect the degree of influence of the transducer during the collection process, so this step embeds the frequency and amplitude information as additional attributes into the grid cells to form a frequency-amplitude embedded grid.

[0109] In this embodiment, each structure surface grid cell locates back to its source transducer and scanning time interval according to the beam number of its forming point in the scanning sequence, and then extracts the dominant disturbance frequency and amplitude analyzed from the scanning path of this segment, and embeds the pair of parameters as disturbance metadata of the grid cell. In this way, a visual frequency-amplitude distribution layer is formed on the entire structure surface, revealing the disturbance degree and pattern of each region in the structure scanning process. This joint embedded structure will provide a key reference dimension for subsequent stability analysis and primary and secondary transducer selection.

[0110] S2.2.2.4: Calculate the frequency-amplitude distribution stability and structure surface morphology continuity of the frequency-amplitude embedded grid;

[0111] Specifically, to realize the quantitative judgment of the reliability of the two transducer structures, the stability of the frequency amplitude perturbation response and the continuity of the grid structure in the geometric shape are calculated respectively, and a set of structure-frequency composite evaluation index is constructed. The frequency amplitude stability is used to describe the consistency of the perturbation in the sampling process of the transducer, that is, whether the fluctuation is violent and random; and the structure surface continuity is used to evaluate whether the point cloud grid has problems such as folding, boundary discontinuity, and slope mutation.

[0112] In this embodiment, the frequency amplitude stability is constructed by statistically analyzing the frequency change gradient, standard deviation and fluctuation trend in the grid area to construct a frequency amplitude consistency scoring model; the structure surface continuity is based on the normal vector change trend, boundary closure degree, and internal angle continuity between the grid segments to establish a shape consistency matrix. After comprehensive calculation, the comprehensive structure quality evaluation result of each transducer under the current period is obtained.

[0113] S2.2.2.5: determining the main transducer and the auxiliary transducer according to the frequency amplitude distribution stability and the structure surface continuity, and constructing a resonant compensation angle control sequence according to the main transducer scanning track and the attitude disturbance;

[0114] Specifically, since the two transducers may have different stability and data quality when scanning the same area due to different directivity, the main and auxiliary roles need to be divided based on the evaluation results to make the reference source of compensation control more reliable. The main transducer is used to provide a structure standard, and the auxiliary transducer is used for directional compensation. Under the premise that the transducer structure is fixed and the scanning angle is synchronized, this division allows a larger angle correction to be performed on the auxiliary transducer, while the main transducer remains unchanged as a stable reference to maintain the original scanning track, thereby realizing asymmetric optimization in the control strategy.

[0115] In this embodiment, the control module compares the scores of the frequency amplitude embedded grids of the two transducers, and selects the one with a higher score as the main transducer. Based on the scanning track and attitude response of the main transducer, a resonant compensation angle control sequence is constructed. This sequence can be combined with the dominant frequency modeling method described above to further enhance the adaptability of the compensation sequence in the spatial direction and realize a higher quality disturbance hedging mechanism.

[0116] S2.2.2.6: applying the resonant compensation angle control sequence to the swing control of the auxiliary transducer in the next Z-axis rotation positioning;

[0117] The specific steps of S3 are as follows:

[0118] S3.1: using the structure installation method of fixing the first transducer and the second transducer on the device at an angle of 90° to establish the spatial direction projection relationship between the scanning beams;

[0119] Specifically, the structure design of two transducers installed at a 90° angle is one of the key innovations of the embodiment. Traditional multi-transducer solutions generally use the same direction or parallel arrangement, which can easily cause strong beam direction overlap and poor spatial region complementarity, resulting in shielding blind areas or structural overlap in complex scenarios. In this structure, the first transducer and the second transducer are installed in opposite directions through the X-axis, and their respective main axes intersect in the vertical plane, forming an orthogonal structure that ensures that the two transducers can complementarily scan the same measurement area from two directions at the same Z-axis positioning angle, providing a dual-view data source. In order to realize subsequent spatial point cloud alignment and conflict area identification, a directional geometric model of the transducer beam in space, i.e., a projection relationship, needs to be established.

[0120] In this embodiment, according to the known structural parameters of the device, such as the relative arrangement angle of the transducers, the installation position, the swing angle limit range, etc., the spatial scanning cone axis direction and its angular range of the two transducers at a given Z-axis attitude are calculated to form a theoretical beam intersection spatial model. This model defines the position, angular overlap area and its extension boundary between the two beams in three-dimensional space, which is used for subsequent positioning and identification of redundant scanning data. The directional projection relationship model takes the transducer center position as the origin and the angle between the swing axis and the Z-axis as the projection variable to construct its propagation cone orientation representation in the three-dimensional Cartesian coordinate system.

[0121] S3.2: Construct local spatial point clouds for the sonar echo data acquired by the first transducer and the second transducer at the same Z-axis positioning angle, and extract the boundary region and the geometric structure intersection area;

[0122] Specifically, since the spatial directions of the two transducers are different at the same Z-axis positioning angle, the data collected by them have spatial perspective differences, but there is still a part of the area that is repeatedly scanned in the intersection area of the two transducer beams, which is defined as the geometric structure intersection area. In order to accurately identify these areas and prepare for subsequent redundancy stripping and reconstruction, the data of the two transducers need to be converted into spatial point clouds, and the intersection boundary region needs to be extracted.

[0123] In this embodiment, the original echo data of the first transducer and the second transducer are converted into local point cloud sets after time stamp analysis and distance-angle conversion. The point clouds are converted using the transducer spatial coordinate system and the projection model to project them into a unified world coordinate system. After the point clouds are generated, the edge region of the point cloud is identified based on the boundary density analysis algorithm, i.e., the region where the gradient changes sharply at the boundary of each point cloud. By comparing the degree of coincidence and the normal angle of the edge regions of the two transducers in three-dimensional space, the intersection sections are determined. These intersection sections are the key areas for subsequent spatial conflict judgment and structure fusion.

[0124] S3.3: based on the spatial direction projection relationship, performing direction conflict analysis on the boundary region and the intersection region of the geometric structure to obtain a redundant reconstruction segment;

[0125] Specifically, although the point cloud data of the two transducers at the intersection region has complementarity, if not distinguished and directly combined, it is easy to cause redundancy, reconstruction error or even structure folding. Especially in the case of disturbance in underwater environment and inconsistent scanning direction, the boundary structures constructed by the two transducers may have inconsistent spatial trends or relative offsets in the intersection section, resulting in error accumulation. Therefore, it is necessary to perform direction conflict analysis on the point cloud boundary in the intersection region, identify the data region that causes geometric contradiction or repeated definition in the spatial structure, and process it as a redundant segment.

[0126] In the embodiment, a conflict identification algorithm based on the included angle of the spatial projection direction is used to calculate the included angle difference and the spatial distance error of the normal vectors of the point cloud boundaries corresponding to the two transducers. The regions exceeding the preset tolerance (such as an included angle of 10° or a distance of 0.3 m) are marked as direction conflict segments. Then, whether they constitute a redundant reconstruction segment is further determined based on the data density variation and boundary continuity in the region. All conflict regions are marked and stored in the “redundant point set” data pool for subsequent processing by the structure reconstruction module. The operation is essentially to separate the error segments caused by the inconsistency of the two direction structures from the main structure, which is a key link to ensure the geometric consistency of the surveying and mapping model.

[0127] S3.4: performing structure correction processing on the redundant reconstruction segment to generate single structure information;

[0128] Specifically, the redundant reconstruction segment is essentially a structural ghost caused by the difference between two perspectives. If it is directly removed or simply fused, it will cause problems such as boundary loss and structure fracture. In order to maximize the use of data and maintain the stability of the structure, it is necessary to geometrically correct the redundant segment to remap it to a unified structure expression, that is, to construct an “intermediate structure surface” for fusion expression.

[0129] In the embodiment, boundary surfaces are constructed from the redundant segments of the first transducer and the second transducer, respectively, and their spatial edge lines are extracted. An intermediate geometric surface is fitted in the conflict interval as a reference surface for structure merging. Then, the point cloud data on the two structure surfaces is projected onto the intermediate curved surface to eliminate the spatial difference caused by the included angle, and its position is adjusted based on the nearest normal mapping principle, so that the projected data is unified in shape in space. After structure correction, the point cloud is marked as a fusion surface patch, replacing the original two-way conflict segment, and is re-included in the structure synthesis process.

[0130] S3.5: fusing the single structure information and the local spatial point cloud to generate a corresponding underwater three-dimensional surveying and mapping result;

[0131] Specifically, after completing the structure correction and generating the unified patch, it is still necessary to merge it with the original local point cloud data in the non-intersection area to form a complete spatial structure expression. The fusion process needs to handle the splicing of the structure interface, the selection priority of the point cloud overlapping area, and the calibration consistency of the global coordinates, to ensure that the final constructed three-dimensional model has spatial continuity, geometric consistency and structural visibility.

[0132] In this embodiment, the fused patch after structure correction is boundary stitched with the local point cloud data in the non-intersection area of each transducer in the unified coordinate system, a patch priority strategy is adopted, the main transducer boundary data is preferentially retained, and the secondary transducer data is used to complete the structure hollow area. A spatial weighted average mechanism is added in the point cloud fusion process to smooth the transition point density difference and eliminate the structure gap. The fused model is verified by curvature consistency and topological closure to confirm the completeness of the overall structure, and finally output as a three-dimensional mapping model file in a standard format for subsequent analysis or visualization platform.

[0133] The specific steps of S3.4 are as follows:

[0134] S3.4.1: Construct the boundary structure surface formed by the first transducer and the second transducer in the redundant reconstruction segment, and extract its edge line in space;

[0135] S3.4.2: Compare the spatial trend difference and geometric offset relationship of the two edge lines in the redundant reconstruction segment;

[0136] S3.4.3: Fit an intermediate geometric surface based on the spatial trend difference and offset relationship as the structure reference surface of the redundant reconstruction segment;

[0137] S3.4.4: Perform remapping operation of the boundary structure surface to the structure reference surface respectively to obtain single structure information after spatial reconstruction.

[0138] A dual transducer underwater mapping sonar device, the sonar device comprising:

[0139] A vertical rotation mechanism, comprising a Z-axis that can rotate in the horizontal direction and an X-axis that can swing vertically relative to the Z-axis, the Z-axis and the X-axis being connected to each other to form a two-dimensional rotation structure;

[0140] A first transducer and a second transducer are installed at a right angle on both sides of the X-axis respectively, and swing vertically together with the X-axis, and the Z-axis drives the X-axis to rotate step by step around the vertical direction;

[0141] A control module for controlling the Z-axis to rotate and position in the horizontal direction according to a preset step angle, and controlling the X-axis to drive the first transducer and the second transducer to scan within a preset swing angle range.

[0142] a data acquisition and processing module configured to acquire sonar echo data of the first transducer and the second transducer at each rotating posture, and correct the sonar echo data based on the rotating position information of the Z-axis and the X-axis to generate corresponding underwater three-dimensional mapping results.

[0143] The control module is further configured to acquire real-time posture information synchronously when the first transducer and the second transducer perform vertical swing scanning, and dynamically correct the swing angle range of the X-axis based on the real-time posture information.

[0144] The data acquisition and processing module is further configured to:

[0145] analyze boundary structure deviation of data acquired by the first transducer and the second transducer at the same Z-axis positioning angle in the spatial overlapping region;

[0146] generate an intermediate fitting surface based on the boundary structure deviation, and map data from the two transducers to the intermediate fitting surface to perform structure consistency correction.

[0147] Although the embodiments of the present application have been shown and described above, it should be understood that the above-described embodiments are exemplary, and should not be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for underwater surveying by means of a dual transducer underwater surveying sonar device, said sonar device having a first transducer and a second transducer mounted at right angles to each other on a vertical rotating mechanism comprising a horizontally rotatable Z-axis and a vertically oscillating X-axis, characterized in that, The underwater mapping method comprises: controlling the Z-axis to rotate and position in the horizontal direction according to a preset step angle; at each Z-axis positioning angle, controlling the X-axis to drive the first transducer and the second transducer to scan in the vertical direction within a preset swing angle range, so as to collect sonar echo data; according to the rotation position information of the Z-axis and the X-axis, correcting the spatial position of the sonar echo data to generate a corresponding underwater three-dimensional mapping result; the method according to the rotation position information of the Z-axis and the X-axis, the spatial position of the sonar echo data is corrected, comprising: using the structure installation mode that the first transducer and the second transducer are fixed at an angle of 90 degrees on the device to establish the spatial direction projection relationship between the scanning beams; constructing local spatial point clouds by using the sonar echo data collected by the first transducer and the second transducer at the same Z-axis positioning angle, and extracting the boundary region and the geometric structure intersection area; based on the spatial direction projection relationship, the directionality conflict analysis is performed on the boundary region and the geometric structure intersection area, and a redundant reconstruction segment is obtained; performing structure correction processing on the redundant reconstruction segment to generate single structure information; fuse the single structure information and the local spatial point cloud to generate a corresponding underwater three-dimensional mapping result; the structure correction processing of the redundant reconstruction segment, comprising: constructing the boundary structure surface formed by the first transducer and the second transducer in the redundant reconstruction segment, and extracting the edge lines in space; comparing the spatial trend difference and geometric offset relationship of the two edge lines in the redundant reconstruction segment; fitting an intermediate geometric surface based on the spatial trend difference and offset relationship as a structure reference surface of the redundant reconstruction segment; performing remapping operation on the boundary structure surface to the structure reference surface respectively to obtain the single structure information after spatial reconstruction.

2. The dual transducer underwater mapping method of claim 1, wherein, controlling the X-axis to drive the first transducer and the second transducer to scan in the vertical direction within a preset swing angle range, comprising: synchronously collecting real-time attitude information during the scanning process, wherein the real-time attitude information includes pitch angle, roll angle and yaw angle; correcting the preset swing angle range according to the real-time attitude information.

3. The dual transducer underwater mapping method of claim 2, wherein, correcting the preset swing angle range according to the real-time attitude information, comprising: performing Fourier transform on the real-time attitude information to analyze the dominant frequency and amplitude of the attitude disturbance; constructing a resonance compensation angle control sequence with the same frequency or inverse frequency as the attitude disturbance according to the dominant frequency and amplitude, wherein the resonance compensation angle control sequence is a swing angle correction sequence that changes continuously with the scanning time; in the process of driving the first transducer or the second transducer to swing and scan on the X-axis, the resonance compensation angle control sequence is superimposed and executed.

4. The dual transducer underwater mapping method of claim 3, wherein, constructing a resonance compensation angle control sequence with the same frequency or inverse frequency as the attitude disturbance according to the dominant frequency and amplitude, comprising: extracting the corresponding dominant frequency and amplitude of the first transducer and the second transducer in the X-axis swing scanning process respectively; performing local point cloud construction and grid reconstruction on the sonar echo data collected by the first transducer and the second transducer within their scanning period to form corresponding local spatial structure surfaces; In the local spatial structure surface, dominant frequency and dominant amplitude value of the source beam segment are given to each grid cell to construct a frequency-amplitude embedded grid; Frequency-amplitude distribution stability and structure surface morphology continuity of the frequency-amplitude embedded grid are calculated; A main transducer and a secondary transducer are determined according to the frequency-amplitude distribution stability and structure surface morphology continuity, and a resonant compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance is constructed according to the main transducer scanning track; The resonant compensation angle control sequence is applied to the swing control of the secondary transducer in the next Z-axis rotation positioning.

5. The dual transducer underwater mapping method of claim 4, wherein, According to the dominant frequency and amplitude, a resonant compensation angle control sequence with the same frequency or opposite frequency as the attitude disturbance is constructed, and the resonant compensation angle control sequence further comprises: Before the secondary transducer executes the resonant compensation angle control sequence, the offset amplitude and coverage missing interval of the actual swing track caused by the resonant compensation angle control sequence relative to the preset swing angle range are predicted; According to the offset amplitude and coverage missing interval, the scanning angle amplitude value of the main transducer is adjusted.

6. A dual transducer underwater mapping sonar apparatus for implementing a dual transducer underwater mapping method as claimed in any one of claims 1 to 5, characterised in that, The sonar device comprises: A vertical rotation mechanism comprising a Z-axis capable of rotating in a horizontal direction and an X-axis capable of swinging vertically relative to the Z-axis, the Z-axis and the X-axis being connected to each other to form a two-dimensional rotation structure; A first transducer and a second transducer are installed at two sides of the X-axis at a right angle, and swing vertically together with the X-axis, and the Z-axis drives the X-axis to rotate step by step around the vertical direction; A control module is configured to control the Z-axis to rotate and position in the horizontal direction according to a preset step angle, and control the X-axis to drive the first transducer and the second transducer to scan within a preset swing angle range; A data acquisition and processing module is configured to acquire sonar echo data of the first transducer and the second transducer at each rotation attitude, and correct the sonar echo data based on rotation position information of the Z-axis and the X-axis to generate corresponding underwater three-dimensional mapping results.

7. The dual transducer underwater mapping sonar system of claim 6, wherein, The control module is configured to synchronously acquire real-time attitude information when the first transducer and the second transducer vertically swing and scan, and dynamically correct the swing angle range of the X-axis based on the real-time attitude information.

8. The dual transducer underwater mapping sonar system of claim 6, wherein, The data acquisition and processing module is configured to: Analyze boundary structure deviation of data acquired by the first transducer and the second transducer in the same Z-axis positioning angle in a spatial overlapping area; Generate an intermediate fitting surface based on the boundary structure deviation, and map data from the two transducers to the intermediate fitting surface to perform structure consistency correction.

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