A surface positioning method for curved structures based on non-uniform angular plane wave technology

Abstract

This invention relates to a method for locating the upper surface of a curved structure based on non-uniform angle plane wave technology, comprising the following steps: generating a plane wave emission angle sequence based on a non-uniform distribution function according to the maximum deflection angle and the total number of sampling angles; sequentially emitting plane waves to the curved structure through an array transducer according to the angle sequence, and recording the echo signals received by all array elements at each angle; extracting the envelope of the received echo signals to obtain the envelope signal; performing imaging reconstruction on the envelope signal using a time-domain delay superposition algorithm to obtain a composite imaging result; extracting the echo envelope intensity distribution based on the composite imaging result, reconstructing the spatial contour of the upper surface of the curved structure, and realizing the location of the upper surface of the curved structure. Compared with the prior art, this invention significantly enhances the sound field contribution in the direction of large deflection angles under a limited number of angles, improves the reflected signal intensity and imaging clarity of the curved structure region, and is suitable for non-destructive testing of complex curved structures.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, and in particular to a method for locating the upper surface of a curved structure based on non-uniform angular plane wave technology. Background Technology

[0002] Plane wave imaging (PWI) is a highly efficient ultrasound imaging technique that utilizes multi-angle ultrasonic plane wave excitation and acquires wavefield information by receiving echo signals from all array elements. This information is then combined with time-delay superposition to reconstruct structural information. The method involves emitting plane waves at different incident angles to acquire multi-directional reflected signals covering the area under test, and then using time delays to sum and reconstruct the structural information of the target area. Due to its high data acquisition efficiency and imaging frame rate, while maintaining high resolution, plane wave imaging has been widely researched and applied in fields such as medical ultrasound, industrial non-destructive testing, and health monitoring of composite material structures.

[0003] In engineering equipment such as pressure vessels, curved shell structures, wind turbine blades, and aerospace composite components, the objects under inspection generally have complex curved surface shapes. The geometry of the curved surface directly affects the incident mode, reflection direction, and echo propagation path of ultrasonic waves, thus placing higher demands on the accuracy of the upper surface position information of the tested curved surface structure. Precise positioning of the upper surface of the curved surface is the foundation for subsequent beam path calculation, time-delay reconstruction, and quantitative defect depth. Once the surface positioning is inaccurate, the time-delay calculation will also be incorrect, leading to misalignment, blurring, or even artifacts in the reconstructed image, severely affecting the reliability of internal defect identification. Therefore, to achieve high-precision positioning and imaging reconstruction of the upper surface of curved structures, it is essential to more effectively acquire the acoustic information related to the curved surface structure.

[0004] However, existing plane wave imaging techniques typically employ an equal-angle interval (uniform sampling) emission strategy. This strategy exhibits significant limitations in locating complex curved surfaces. Curved surfaces alter reflection characteristics at different incident angles, leading to stronger non-uniformity in the distribution of echo information at different angles. Furthermore, under uniform-angle sampling conditions, large-angle plane waves struggle to capture complete reflection information of the curved surface due to the reduced projection of the array's effective aperture in the deflection direction. Conversely, small-angle plane waves have high signal-to-noise ratios, and the similarity in echo height between adjacent deflection angles results in information redundancy. This imbalance in structural information acquisition caused by the equal-angle interval emission strategy is further amplified when the number of emission angles is limited. This directly leads to increased errors, blurred boundaries, and loss of curvature details in plane wave imaging for locating curved surfaces, thus affecting the accurate reconstruction of complex surface geometry.

[0005] In conventional uniform angle sampling schemes, increasing the number of emission angles is typically necessary to improve resolution at large angles. However, this significantly increases the data volume and computational complexity, hindering the implementation of real-time detection or portable imaging systems. Therefore, to overcome the limitations of uniform sampling on curved surfaces and achieve high-precision positioning and rapid imaging reconstruction of curved surfaces, it is necessary to propose a novel method based on non-uniform angle sampling. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing plane wave imaging techniques in locating the upper surface of complex curved structures, especially the problems of unbalanced structural information acquisition and limited upper surface positioning accuracy caused by uniform angle sampling. Therefore, a plane wave imaging method based on non-uniform angle sampling and time-domain delay superposition is proposed. By reasonably allocating the angle sampling density and weight, the effective information contribution of the sound field at large deflection angles is enhanced, thereby achieving high-precision positioning and imaging reconstruction of the upper surface of curved structures under limited angle sampling conditions.

[0007] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for locating the upper surface of a curved structure based on non-uniform angular plane wave technology, comprising the following steps: S1. Design a non-uniform angle sampling strategy: Based on the maximum deflection angle and the total number of sampling angles, generate a plane wave emission angle sequence based on a non-uniform distribution function; S2. Plane wave excitation and signal acquisition: Plane waves are sequentially emitted to the curved structure through the array transducer in an angular sequence, and the echo signals received by all array elements at each angle are recorded. S3. Envelope signal extraction: Extract the envelope of the echo signal to obtain the envelope signal; S4. Delayed superposition imaging: The envelope signal is reconstructed by a time-domain delay superposition algorithm to obtain composite imaging results; S5. Surface localization on curved surfaces: Extract the echo envelope intensity distribution based on the composite imaging results, reconstruct the spatial contour of the surface on the curved surface, and realize the localization of the surface on the curved structure.

[0008] Furthermore, in step S1, the angle sequence is used to control the emission direction distribution of the plane wave, and its distribution form includes, but is not limited to, symmetrical and asymmetrical distribution modes.

[0009] Furthermore, in step S1, the sampling angles are symmetrical about the vertical direction, and the negative angles are obtained by mirroring the positive angles, with the total number of sampling angles... = 2 – 1, of which This represents the number of sampling angles in the positive half-zone.

[0010] Further, in step S1, the angle sequence is determined according to the following formula: ; In the formula, For the first The emission angle of a plane wave, For the maximum deflection angle, ; r For non-uniform sampling adjustment parameters, 0 < r <1.

[0011] Furthermore, the non-uniform sampling adjustment parameter r The typical value range is 0.2 to 0.8. This can be achieved by adjusting the parameters. r Controlling the sampling density at different deflection angles, when r When <1, sampling is more dense in the large deflection angle region. r When the value is 0.5, the sampling density and imaging accuracy in the large deflection angle region are balanced, which is suitable for most common curved surface structures.

[0012] Further, in step S2, the array transducer, through a control system, sequentially excites plane waves towards the curved structure in directions corresponding to the angle sequence, and receives echo signals from each angle through all array elements. The number, arrangement, and spacing of the array elements of the transducer are flexibly selected according to the size and frequency characteristics of the object being detected.

[0013] Further, in step S3, the envelope signal is obtained by any one of the following extraction methods or other equivalent methods: Hilbert transform (analytic signal method), envelope detection (Rectification + Low-pass filter), RMS envelope, wavelet envelope, etc., preferably Hilbert transform.

[0014] Furthermore, in step S3, the envelope signal is further processed by any one of normalization, bandpass filtering, time-domain smoothing, or logarithmic compression to eliminate amplitude differences and improve the signal-to-noise ratio.

[0015] Furthermore, in step S4, for any imaging point in space... The envelope signal is processed according to the following formula. Perform time-delay overlay: ; In the formula, in the formula, For the first i The first angle, the second j The envelope signal is obtained by extracting the envelope of the original echo signal received by each array element. For the intensity of the imaging result, This represents the total number of array transducer elements. This represents the total number of ultrasonic plane wave emission angles. d tx ( x , z , θ i ) represents the acoustic path distance (i.e., the launch path length) from the transmitting element to the target point. d rx ( x,z,j ) represents the acoustic path distance (i.e., the receiving path length) from the target point to the receiving array element. c The speed of sound.

[0016] Furthermore, in step S5, the echo envelope intensity distribution is extracted along the vertical direction, and the position of the upper surface is determined by analyzing the envelope peak value, local extrema, or energy threshold distribution.

[0017] Furthermore, the localization algorithm used in the localization is any one of envelope peak detection, gradient change detection, threshold segmentation, and gradient search.

[0018] Furthermore, the curved surface structure can be classified as a non-planar geometric surface of metal or composite materials, including typical weld transition areas, pressure vessel outer walls, and composite structure blade surfaces, etc., and is suitable for ultrasonic imaging and upper surface positioning of target objects with complex curved surface features.

[0019] Furthermore, the method can operate in real-time or offline mode and is applicable to portable ultrasound testing systems, laboratory scanning imaging systems, and automated online monitoring equipment.

[0020] Compared with the prior art, the present invention has the following technical advantages: (1) This invention innovatively introduces a non-uniform angle sampling mechanism into ultrasonic plane wave imaging, which improves the density of acoustic field information acquisition in the large deflection angle region, enhances the intensity of reflected signals and imaging clarity in the large angle deflection region, and effectively improves the problem of poor ability to acquire structural information in large angle plane waves under traditional uniform angle sampling.

[0021] (2) Under the condition of a limited number of emission angles, the present invention achieves high-precision positioning of the upper surface of the curved structure. Compared with the traditional uniform angle sampling method, the present invention significantly reduces the imaging blur in the large deflection angle direction, significantly reduces the imaging blur, unclear boundaries and positioning error in the curved area, and improves the ability to identify the geometric features of complex surfaces.

[0022] (3) The present invention adopts a time-domain delay superposition algorithm based on envelope signal, which avoids the artifact problem caused by phase interference and improves the contrast and stability of imaging.

[0023] (4) The algorithm proposed in this invention has a simple structure and adjustable parameters, and is suitable for non-destructive testing of various curved materials and complex curved structures as well as portable ultrasonic imaging systems.

[0024] (5) The method of the present invention ensures imaging accuracy while taking into account real-time performance, with low data volume and computational complexity, and is suitable for rapid application in engineering field testing and portable ultrasound imaging systems.

[0025] (6) Without significantly increasing the number of emission angles, the present invention achieves balanced acquisition of sound field information and high-precision positioning of the surface of curved surfaces. It has the advantages of high resolution, strong robustness, high computational efficiency and easy engineering implementation, and can significantly improve the ultrasonic imaging performance of complex curved surface structures. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the basic process of the surface positioning method for curved structures of the present invention.

[0027] Figure 2 This is a schematic diagram of the overall process of the surface positioning method for curved structures in Embodiment 1 of the present invention.

[0028] Figure 3 This is a schematic diagram illustrating the generation of the non-uniform angular distribution of the present invention, showing the situation under a set maximum deflection angle. =80° and control parameters r Under the condition of 0.5, each angle Distribution of [something].

[0029] Figure 4 For different adjustment parameters r The following diagram illustrates the angular distribution of the parameters. r The impact on angle sampling density and distribution characteristics.

[0030] Figure 5 This is a schematic diagram of the signal acquisition process of the present invention, including an ultrasonic linear array transducer, coupling conditions, signal acquisition process, the acquired raw signal and its envelope; the figure indicates the first... i The launch angle, from the first j The envelope signal received by each element .

[0031] Figure 6 This is a schematic diagram of a carbon fiber composite curved surface specimen used for experimental verification of the present invention. The specimen includes a curvature transition region (R region) to verify the positioning capability of the present method on curved surface structures.

[0032] Figure 7 This is the plane wave imaging result based on traditional uniform angle sampling.

[0033] Figure 8 This is the imaging result based on non-uniform angle sampling in this invention.

[0034] Figure 9 This is a schematic diagram of the surface positioning results on the curved surface of the present invention. The red dots represent the positioning results obtained by non-uniform angular plane wave imaging.

[0035] Figure 10 This is a schematic diagram comparing the surface positioning results of curved surfaces in plane wave imaging results with uniform and non-uniform angles according to the present invention. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0037] To overcome the problems of unbalanced structural information, insufficient utilization of curved surface reflection information, and limited upper surface positioning accuracy in traditional uniform angle plane wave imaging methods under limited array size conditions, this invention proposes a method for locating the upper surface of curved structures based on non-uniform angle plane wave technology. This method combines a non-uniform angle sampling strategy with a time-domain delay superposition algorithm based on envelope signals within the framework of traditional ultrasonic plane wave imaging. The method generates a set of plane wave emission angles through non-uniform angle sampling. Within a set maximum deflection angle range, it samples the large deflection angle region with higher density and the small angle region with lower density, achieving optimized allocation of acoustic field information for a limited array of transducers. The echo envelope signals of the entire array elements excited by plane waves at various angles are then delayed and superimposed to obtain the echo intensity distribution map of the upper surface of the curved surface. Precise positioning of the upper surface of the curved surface is achieved by comparing the peak positions of the echo envelope.

[0038] First, this invention introduces a non-uniform angle sampling strategy during the plane wave excitation stage to adjust the sampling density distribution in different deflection angle directions. In order to always retain the signal from the vertically excited plane wave, the plane wave deflection angle distribution is generated symmetrically about zero degrees. Only the positive half-region angle needs to be generated, and the negative half-region can directly take its symmetrical angle.

[0039] Specifically, let the maximum deflection angle be... The number of sampling angles in the positive half-region is (including) and Then, the set of positive angles can be generated by the following formula: ; in, For the first The emission angle of a plane wave, , . For non-uniform sampling adjustment parameters, ,when When uniform sampling is used, when Sampling is more concentrated at large deflection angles. The negative half-region can directly take the symmetrical angle of the positive half-region, forming a complete set of emission angles as follows: .

[0040] This angular distribution results in a larger sampling interval in small-angle regions and a denser interval in large-angle regions, thereby enhancing the ability to collect sound field information in the direction of large deflection angles.

[0041] During the data acquisition phase, the array transducers sequentially excite plane waves according to the aforementioned angle sequence and receive echo signals from each angle through all array elements. For the first... i The first angle, the second j Envelope extraction is performed on the echo signals of each array element to obtain the envelope signal. It is used for time-domain overlay processing.

[0042] During the imaging phase, a time-domain delay-and-sum algorithm is used for multi-angle sound field composite. The delay-and-sum algorithm employs a point-by-point delay-summation method in the time domain, eliminating the need for frequency domain computation and making it suitable for real-time ultrasound imaging systems. For any imaging point in space... Its reconstructed signal is represented as: ; in, For the intensity of the imaging result, This represents the total number of array transducer elements. This represents the total number of ultrasonic plane wave emission angles. For the first Each element at the launch angle Down to the imaging point The total propagation delay. By superimposing the delays of signals at different emission angles, coherent synthesis of sound fields at multiple angles can be achieved.

[0043] Compared to traditional uniform sampling methods, the non-uniform angular sampling distribution designed in this invention significantly improves the utilization rate of acoustic field information in large-angle deflection directions under a limited number of angles, thereby enhancing the positioning accuracy and imaging clarity of curved surface structures. This invention is applicable to ultrasonic non-destructive testing and imaging positioning of curved structures or complex geometric surfaces, and is particularly suitable for the surface inspection and geometric reconstruction of composite material components, curved metal parts, pressure vessels, and complex aerospace structures. Furthermore, the parameters can be adjusted according to specific application scenarios. Flexible adjustments can be made to balance data volume and imaging accuracy without increasing the number of emission angles, thus achieving efficient and reliable positioning of the upper surface of curved structures.

[0044] The following examples illustrate the entire process from initialization preparation to output results.

[0045] Example 1: This embodiment provides a method for locating the upper surface of a curved structure based on non-uniform angular plane wave technology. For example... Figure 2 As shown, the complete process from data acquisition, non-uniform angle generation, plane wave excitation, echo envelope acquisition, time delay superposition to upper surface positioning is demonstrated.

[0046] The method for locating the upper surface of the curved structure in this embodiment specifically includes the following steps: Step 1: Initialization preparation.

[0047] Set the basic parameters of the array ultrasound signal acquisition system, such as array parameters, signal sampling rate, and detection tasks.

[0048] Step 2: Establishing acoustic coupling.

[0049] Under water immersion or water spray coupling conditions, the array ultrasonic transducer maintains appropriate acoustic coupling with the surface structure being tested.

[0050] Step 3: Rough alignment and distance adjustment of the array.

[0051] By adjusting the position and orientation of the transducer, it is roughly aligned with the curved surface area to be inspected, ensuring that the emitted beam covers the upper surface. The array ultrasonic transducer is fixed to the scanning device or positioning platform, and the sound path and echo time range are determined by real-time echo signal monitoring. Near-field interference may occur when the distance is too close, while signal attenuation is severe when the distance is too far; therefore, the transducer needs to be adjusted to the optimal working distance range.

[0052] Precise positioning is not required at this stage; it is only necessary to ensure effective sound energy transmission and a sufficient signal-to-noise ratio for the echo signal. After rough alignment is completed, the angle excitation stage begins.

[0053] Step 4: Generate non-uniform angle sampling distribution.

[0054] Set maximum deflection angle The number of sampling angles in the positive half-region is (including) and ) and total number of plane wave emissions To ensure wavefield symmetry, this invention employs ± The symmetrical emission strategy ensures balanced coverage of the sound field along the incident direction. The plane wave deflection angle distribution is generated symmetrically about zero degrees, requiring only the positive half-region angle to be generated; the negative half-region angle can be directly taken as its symmetrical angle.

[0055] To enhance the sound field sampling density in the large deflection angle region, this invention employs a non-uniform angle sampling strategy based on a power function distribution, with the emission angle... The calculation formula is: ; in, r This is a non-uniform sampling adjustment parameter used to control the concentration of the angle distribution. When r When > 1, the sampling density is higher in the small-angle region; when 0 < r When 0 < 1, the sampling density increases in large-angle regions. This invention is mainly used to improve the imaging and positioning of the upper surface of curved structures, therefore, 0 < 1 is used. r < 1. Increase the sampling density in large-angle regions. This can be achieved by adjusting the number of sampling angles. With parameters r It can achieve imaging resolution comparable to or higher than uniform sampling while maintaining fewer emission counts.

[0056] Figure 3 Maximum deflection angle = 80°, =8, r Under the condition of 0.5, each angle The distribution of . When r When = 0.5, the sampling interval is larger in the small-angle region of plane wave deflection near 0°, and the sampling is more dense in the large-angle region.

[0057] Figure 4 For different r A schematic diagram of the angular distribution of generated values ​​is shown in the figure. r The selection of the sampling angle can effectively adjust the distribution density of the sampling angle in each region.

[0058] Step 5: Plane wave excitation and signal acquisition.

[0059] like Figure 5 As shown, the linear array transducer is fixed above the curved surface structure under test, and the control system is used to... Plane waves are emitted sequentially in the corresponding directions. During each emission, all receiving elements in the array record time-series echo signals, forming multi-angle, multi-channel wavefield data.

[0060] When the emission angle is large, the effective aperture of the array decreases in the incident direction, and the array elements cannot receive sufficient structural reflection signals. To compensate for this effect, this invention increases the sampling density in the large-angle region, making the overall sound field coverage more uniform and ensuring the integrity of reflection information during imaging.

[0061] Step 6: Envelope extraction and time-lapse imaging.

[0062] Envelope extraction is performed on the raw echo signal obtained in step 5 to eliminate the influence of phase fluctuations on the imaging results.

[0063] For the i The first angle, the second j The envelope signal received by each array element Imaging reconstruction is performed using a time-delay stacking algorithm. For any point in the imaging region... Its imaging intensity Represented as: ; in, d tx ( x , z , θ i )and d rx ( x,z,j These represent the acoustic path distances from the transmitting element to the target point and from the target point to the receiving element, respectively. c The speed of sound in water. By delaying and aligning the envelope signal and accumulating it, high signal-to-noise ratio composite imaging results can be obtained.

[0064] Figure 6 This is a schematic diagram of a carbon fiber composite curved surface specimen used to verify the present invention. The specimen contains a curvature transition region (R region) to evaluate the accuracy of the surface positioning on the curved surface.

[0065] Figure 7 The results of traditional plane wave imaging based on uniform angle sampling show that the curvature transition region is significantly blurred in the area illuminated by large-angle plane waves.

[0066] Figure 8 The imaging results based on non-uniform angle sampling of this invention can clearly display the continuous contour of the surface of a curved surface, and the positioning accuracy is significantly improved.

[0067] Step 7: Surface positioning and contour extraction on the curved surface.

[0068] In the obtained composite imaging results, envelope intensity analysis is performed on each imaging column perpendicular to the array direction, and the depth position corresponding to the maximum envelope value is extracted as the localization result of the surface point on the curved surface. The localization algorithm includes, but is not limited to, peak detection, threshold segmentation, or gradient search methods. By connecting the localization points of all columns, the spatial contour of the surface of the curved surface can be reconstructed.

[0069] This method eliminates energy loss at large deflection angles through multi-angle synthesis, significantly improving the continuity and positioning accuracy of the surface boundary.

[0070] Figure 9This is a schematic diagram of the surface positioning results on the curved surface of the present invention. The red dots represent the positioning results obtained by non-uniform angle plane wave imaging, and the surface contour of the large angle region is effectively extracted.

[0071] Figure 10 This diagram illustrates a comparison of surface localization results on curved surfaces obtained using the uniform-angle and non-uniform-angle plane wave imaging methods of the present invention. Red dots represent surface localization results obtained using the non-uniform-angle plane wave imaging method proposed in this invention, while blue dots represent localization results obtained using the traditional uniform-angle plane wave imaging method.

[0072] As can be clearly seen from the figure, the uniform angle method exhibits significant offset and larger positioning errors in areas with large curvature; while the contour obtained by the method of the present invention fits the real surface more closely. This indicates that the non-uniform angle sampling strategy of the present invention can improve the signal utilization rate in the large deflection angle incident area while ensuring balanced coverage of the overall wave field, thereby significantly improving the accuracy and stability of surface positioning on curved surfaces.

[0073] Step 8: Result display and data output.

[0074] The positioning data can be output in a standard format for subsequent high-precision non-destructive testing automatic scanning or CNC machining path generation.

[0075] In summary, this invention discloses a method for locating the upper surface of curved structures based on non-uniform angle plane wave technology, belonging to the field of ultrasonic non-destructive testing and imaging technology. This method generates a set of plane wave emission angles through non-uniform angle sampling. Within a set maximum deflection angle range, it samples the large deflection angle region with higher density and the small angle region with lower density, achieving optimized allocation of acoustic field information for a finite array transducer. The echo envelope signals of the entire array elements excited by plane waves at various angles are then delayed and superimposed to obtain the echo intensity distribution map of the upper surface of the curved surface. Precise location of the upper surface is achieved by extracting the peak position of the echo envelope. Under a finite number of angles, this invention significantly enhances the acoustic field contribution in the large deflection angle direction, improving the reflected signal intensity and imaging clarity of the curved structure region in the large deflection angle direction. Compared with traditional uniform angle sampling methods, this invention significantly reduces imaging blur in the large deflection angle direction region and significantly improves the upper surface positioning accuracy. This method has a simple structure, adjustable parameters, and is suitable for non-destructive testing of complex curved structures and portable ultrasonic imaging systems.

[0076] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for surface positioning on a curved structure based on non-uniform angle plane wave technique, characterized in that, Includes the following steps: S1. Design a non-uniform angle sampling strategy: Based on the maximum deflection angle and the total number of sampling angles, generate a plane wave emission angle sequence based on a non-uniform distribution function; The sampling angles are symmetrical about the vertical direction, and the total number of sampling angles = 2 - 1, wherein is the number of positive half-zone sampling angles; The angle sequence is determined according to the following formula: ； In the formula, For the first The emission angle of a plane wave, For the maximum deflection angle, ; r For non-uniform sampling adjustment parameters, 0 < r <1; S2. Plane wave excitation and signal acquisition: Plane waves are sequentially emitted to the curved structure through the array transducer in an angular sequence, and the echo signals received by all array elements at each angle are recorded. S3. Envelope signal extraction: Extract the envelope of the echo signal to obtain the envelope signal; S4. Delayed superposition imaging: The envelope signal is reconstructed by a time-domain delay superposition algorithm to obtain composite imaging results; S5. Surface localization on curved surfaces: Extract the echo envelope intensity distribution based on the composite imaging results, reconstruct the spatial contour of the surface on the curved surface, and realize the localization of the surface on the curved structure.

2. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, The non-uniform sampling adjustment parameter r The value range is 0.2 to 0.

8.

3. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, In step S2, the array transducer sequentially excites plane waves toward the curved structure in the direction corresponding to the angle sequence through the control system, and receives the echo signals at each angle through all array elements.

4. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, In step S3, the envelope signal is obtained by any one of the following extraction methods: Hilbert transform, envelope detection, square envelope, and wavelet envelope. The envelope signal is further processed by normalization, bandpass filtering, time-domain smoothing, or logarithmic compression to eliminate amplitude differences and improve the signal-to-noise ratio.

5. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, In step S4, for any imaging point in space The envelope signal is processed according to the following formula. Perform time-delay overlay: ； In the formula, For the first i The first angle, the second j The envelope signal is obtained by extracting the envelope of the original echo signal received by each array element. For the intensity of the imaging result, This represents the total number of array transducer elements. Total number of ultrasonic plane wave emission angles d tx ( x , z , θ i () represents the acoustic path distance from the transmitting element to the target point. d rx ( x,z,j () represents the acoustic path distance from the target point to the receiving array element. c The speed of sound.

6. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, In step S5, the echo envelope intensity distribution is extracted along the direction perpendicular to the surface normal.

7. The surface positioning method for a curved structure based on non-uniform angular plane wave technology according to claim 6, characterized in that, The localization algorithm used is any one of envelope peak detection, gradient change detection, threshold segmentation, and gradient search.

8. The method for locating the upper surface of a curved structure based on non-uniform angular plane wave technology according to claim 1, characterized in that, The curved surface structure can be any one of the following: metal curved surface, composite material curved surface, weld transition zone, pressure vessel inner wall, or composite structure blade.

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