Ray-tracing based ultrasound phased array three-dimensional space imaging method and application thereof

Abstract

The application relates to the field of ultrasonic detection, in particular to a three-dimensional space imaging method of an ultrasonic phased array based on ray tracing and application thereof. On the basis of given two-dimensional ultrasonic array element distribution and a geometric model of an object to be detected, all combinations of transmitting elements and receiving elements are traversed, and each transmitting-receiving element pair is analyzed for possible straight paths and multiple reflection paths; then the paths are classified and screened according to reflection times, path lengths, propagation times and echo energies; finally, the screened paths are used to correct a TFM focusing delay rule, so that the three-dimensional imaging quality of an air-coupled or water-immersed two-dimensional array in a limited space is improved. The scheme of the application converts the interference conditions of multiple reflection echoes in a limited space into multi-dimensional perspective information which is beneficial to improving the imaging quality; and the problems of structural noise, artifacts and resolution reduction in the detection of a traditional three-dimensional ultrasonic scheme in a limited environment are solved.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic testing, and in particular to a three-dimensional spatial imaging method for ultrasonic phased array based on ray tracing, and the corresponding computer program product, data processing module and pipeline ultrasonic testing robot. Background Technology

[0002] Pipeline structures are typically considered as hollow cylindrical structures, open axially and closed radially, thus constrained spaces. For most buried drainage, water supply, gas, oil and gas, and industrial pipelines, the wavelength of high-frequency sound waves, i.e., ultrasound, is much smaller than the geometric dimensions of the pipe diameter, length, interface steps, and blockage size. Therefore, ultrasound propagation within pipelines usually satisfies the ray approximation condition, and its main propagation behavior can be described by sound ray propagation, specular reflection, and path energy attenuation. The ray approximation condition can be expressed as... ,and , , Where λ is the ultrasonic wavelength and c is the sound velocity in the coupling medium. f Where D is the ultrasonic center frequency, D is the inner diameter of the pipe, and L is the characteristic length of the structure to be tested. Let be the radius of curvature of the pipe wall. When this condition is met, ultrasonic propagation can be approximately described using a sound ray propagation and specular reflection model.

[0003] Within such confined spaces, the sound waves emitted by the ultrasonic array not only propagate along a straight path to the target and return to the receiving element, but also undergo one or more reflections at pipe walls, liquid surfaces, interface steps, blockage surfaces, or other boundaries. The multipath echoes formed by these multiple reflections may be similar in time and amplitude to the straight-path echoes, resulting in significant structural noise. For air-coupled or water-immersion-coupled two-dimensional ultrasonic arrays, if the time delay rule of free space or a single straight path is still used for TFM focusing, the effective echoes will be incorrectly delayed and superimposed, and the reflected path echoes will be treated as noise or artifacts, ultimately reducing the quality of the three-dimensional imaging. Summary of the Invention

[0004] To address the issue of structural noise, artifacts, and resolution degradation in conventional straight-path TFM imaging caused by multiple reflected echoes approaching those of a straight path within a confined space, this invention provides a ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method, along with its corresponding computer program, data processing module, and pipeline ultrasonic inspection robot.

[0005] The technical solution provided by this invention is as follows: A three-dimensional spatial imaging method based on ray tracing ultrasonic phased array, comprising the following steps: 1. Obtain the geometric model of the object under test; and establish an acoustic propagation model for detecting the object under test using an ultrasonic phased array based on the state parameters of the object under test.

[0006] 2. Traverse the transceiver pairs in the ultrasonic phased array, track each sound ray emitted and propagated at preset angular intervals; record each candidate path that meets the preset constraints; and generate the path characteristics of each candidate path, including: number of reflections, path length, propagation time, incident angle, reflection angle, boundary intersection, reflection coefficient, and path energy.

[0007] 3. Perform transmit / receive array element matching on each candidate path; and filter the matched candidate paths using the following formula to obtain the set of effective paths. :

[0008] In the above formula, p Indicates the voxel to be imaged; Indicates the transmit and receive array elements Candidate paths k Path energy; Indicates the transmit and receive array elements In voxels p Energy along the straight path at the location; η The preset energy ratio threshold; N k Indicate candidate path k The number of reflections; N max Indicates the preset maximum number of reflections; Indicates belonging to the transmit / receive array element pair Candidate paths k The spread time.

[0009] IV. Performing three-dimensional ultrasound imaging of the object under test by combining the effective path set, including: Path weights and focusing delays for generating valid paths; The A-scan signals acquired by each transceiver array element are sampled with a delay according to the effective path corresponding to each voxel and then superimposed to obtain the image intensity of the specified number of reflections. A three-dimensional ultrasound image of the object under test is obtained by fusing the image intensities of different reflection times or different path families.

[0010] The present invention also includes a computer program product comprising a computer program that, when executed by a processor, implements the aforementioned ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method, thereby performing three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

[0011] The present invention also includes a data processing module, which includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the aforementioned ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method, and then performs three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

[0012] The present invention also includes a pipeline ultrasonic inspection robot, comprising a robot body, an ultrasonic phased array radar, and a data processing module. The ultrasonic phased array radar is mounted on the robot body. The ultrasonic phased array radar includes several sets of transceiver array elements arranged in a ring along the cross-sectional direction of the pipeline under test; and is used to acquire A-scan signals inside the pipeline under test.

[0013] The data processing module is electrically connected to the ultrasonic phased array radar; the data processing module has a pre-stored geometric model of the pipe to be tested; and it is used to perform three-dimensional spatial imaging of the pipe to be tested using the ray tracing-based ultrasonic phased array three-dimensional spatial imaging method as described above, based on the geometric model of the pipe to be tested and the A-scan signal acquired by the ultrasonic phased array, thereby generating a three-dimensional ultrasonic image inside the pipe.

[0014] As a further improvement of the present invention, the data processing module is also used to perform threshold segmentation, connected component analysis, Radon pipe transformation, cylindrical coordinate projection or three-dimensional point cloud fitting on the three-dimensional ultrasound image, thereby obtaining the location, width, height, circumferential angle, axial distance and confidence information of pipe interface, blockage, deposit, foreign object, local deformation or other defects.

[0015] The beneficial effects of the technical solution provided by this invention are as follows: This invention designs a three-dimensional spatial imaging method for ultrasonic phased arrays based on ray tracing. The method takes a given two-dimensional ultrasonic array element distribution and the structural model of the target to be detected as input, analyzes the possible straight path and multiple reflection path between each pair of transmitting and receiving elements in the confined space, and transforms the selected effective path into the TFM focusing delay rule, and finally generates a three-dimensional ultrasonic image.

[0016] This scheme transforms the multipath effect in pipelines from an unfavorable interference into usable multi-view imaging information, improving the 3D imaging quality of air-coupled or water-immersion-coupled 2D ultrasound arrays in confined pipeline spaces. The scheme automatically analyzes candidate reflection paths for each transceiver element pair through SBR ray tracing, not limited to the three existing preset paths of direct, single-reflection, and double-reflection, but applicable to pipeline structures with more reflections and greater complexity. The scheme categorizes paths according to the number of reflections and generates corresponding TFM delay rules for each type of path, generating images of straight-line paths, single-reflection paths, and multiple-reflection paths respectively, facilitating subsequent fusion and diagnosis. The imaging stage also employs a path energy ratio-based screening mechanism, for example, using 50% of the echo energy of straight-line paths as a threshold to retain strong reflection paths and discard weak reflection paths, thus balancing imaging quality and computational efficiency.

[0017] In practical applications, this invention can improve focusing quality even with a limited number of array elements and a restricted array aperture, making it suitable for installation on pipeline robots or small-sized pipeline inspection platforms. This solution provides a universal imaging rule for confined spaces, exhibiting broad scenario adaptability. It can be used for internal inspection of pipeline structures using two-dimensional air-coupled ultrasonic arrays, water-immersion coupled ultrasonic arrays, or other liquid-coupled ultrasonic arrays, and can also be used in pipeline robots, pipeline detectors, or fixed pipeline inspection devices. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the principle of three-dimensional sound field imaging based on ultrasonic phased array in the pipeline detection scenario of Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the straight acoustic path used in traditional ultrasound imaging.

[0020] Figure 3 This is a schematic diagram of the semi-reflection path and total reflection path further introduced in the ultrasound imaging of the present invention.

[0021] Figure 4 This is a flowchart of the steps of the ultrasonic phased array three-dimensional spatial imaging method based on ray tracing provided in Embodiment 1 of the present invention.

[0022] Figure 5 This is a sample image of the pipeline ultrasonic testing robot provided in Embodiment 3 of the present invention.

[0023] Figure 6 To compare two different ultrasonic phased array products in the test experiment.

[0024] Figure 7 The pipeline testing environment was provided for the test experiment.

[0025] Figure 8The distribution of effective paths under different beam angles is shown in the diagram.

[0026] Figure 9 Comparison of three-dimensional ultrasound images based on acoustic ray tracing algorithm and acoustic propagation simulation of linear time-invariant system. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] Example 1

[0030] Ultrasonic imaging methods have demonstrated proven performance in open environments and are widely used in aerospace and marine exploration. However, existing ultrasonic imaging methods primarily rely on time-of-flight (TFF) focusing based on a single straight path. Therefore, when applied to target detection in confined spaces, these methods often fail to effectively handle complex detection conditions, such as multiple reflection paths, complex spatial structures, and different acoustic propagation media. For example, existing methods cannot automatically analyze multiple reflection paths based on the actual detection environment, ultrasonic array arrangement, and dynamic changes in the coupling medium. With the generation of numerous reflection paths, this approach introduces many invalid weak paths into the calculation, resulting in insufficient signal-to-noise ratio of the acquired ultrasonic echo signal, multipath interference, and ultimately structural noise, artifacts, and reduced resolution in the imaging results; significantly impacting the accuracy of target identification in space.

[0031] Taking pipeline inspection as an example, a pipeline is a semi-enclosed confined space that is axially open and radially closed. The wavelength of high-frequency ultrasonic waves is much smaller than the geometric dimensions of the pipeline; therefore, its main propagation behavior can be approximated by rays. Ultrasonic phased array radar can be used inside the pipeline for... Figure 1 During the detection process shown, the pipe wall and other boundaries cause the ultrasonic waves to be reflected multiple times. For example... Figure 2 As shown, conventional TFM only uses straight-line path delay, which is equivalent to assuming that the ultrasound only travels along the straight path. (Transmitting element - target - receiving array) propagates in a straight line; however, the actual echo also contains elements such as... Figure 3 The multiple reflection path components shown, if not modeled, will create structural noise and artifacts in the focused image of a straight path.

[0032] To address this issue, this embodiment provides a ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method. This scheme uses the Shooting and Bouncing Rays (SBR) method to trace and analyze the multiple reflection paths of the ultrasonic array's transceiver elements, and optimizes the delay rule of the Total Focusing Method (TFM) to overcome structural noise and artifacts caused by multipath signals. It should be emphasized that while this embodiment primarily designs a solution for ultrasonic inspection inside pipelines, it can be further extended to target detection tasks in other confined spaces, such as indoor ultrasonic imaging.

[0033] In this novel approach, SBR ray tracing, by emitting acoustic rays from the transmitting element and continuing to trace according to the reflection law each time the rays encounter the pipe wall or boundary, can obtain all candidate propagation paths generated by each pair of transmitting and receiving elements in a given environment. The number of reflections, path length, propagation time, and energy attenuation of each path can be recorded. Thus, multipath echoes, originally considered interference, are transformed into computable multi-view imaging information. After obtaining candidate paths, this embodiment uses the energy of the straight-path echo as a reference to filter out reflection paths with sufficiently strong energy. Paths with high signal strength are retained for TFM delay calculation, while weak paths are discarded. This utilizes strong reflection paths within the confined space of the pipe while avoiding artifacts and excessive computational load introduced by numerous weak paths. Based on this, the filtered straight-path and multi-reflection paths together form a focusing rule. Finally, the ultrasound signals are coherently superimposed on the actual propagation path to improve the imaging intensity of the target area and reduce structural noise caused by misfocusing; thereby obtaining a higher-quality three-dimensional ultrasound image within the confined area.

[0034] In detail, such as Figure 4 As shown, the ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method provided in this embodiment includes the following steps: 1. Obtain the geometric model of the object under test; and establish an acoustic propagation model for detecting the object under test using an ultrasonic phased array based on the state parameters of the object under test.

[0035] In this embodiment, when performing ultrasonic testing on any object under test, it is first necessary to obtain the geometric model of the object. This geometric model will be used to model the sound field propagation law of the ultrasonic phased array and realize ray tracing based on SBR ultrasonic signals. Specifically, taking pipeline inspection as an example, the geometric model of the pipeline under test can directly adopt the BIM model from the pipeline engineering design stage. This model can clearly reflect the inner diameter, axis, and wall curvature of each section of the pipeline, and reflect structures such as interface steps and bends, and may even include relevant material information. In this embodiment, in order to reduce the scale and difficulty of data processing while meeting resolution requirements, the geometric model of the object under test can be simplified and networked. For example, for common straight pipe sections, the inner wall of the pipe can be represented as a cylindrical surface; for deformed pipes, interfaces, or bends, segmented surfaces, mesh surfaces, or point cloud surfaces can be used.

[0036] Furthermore, after obtaining the geometric model of the object under test, this embodiment will combine the state parameters of the object under test in the current measurement state to establish an acoustic propagation model that can characterize the propagation law of each ultrasonic signal emitted when the object under test is detected using an ultrasonic phased array. The creation of the acoustic propagation model relies on three types of information: first, the aforementioned geometric model of the object under test; second, various state parameters reflecting the internal environment of the object under test; these state parameters mainly refer to various parameters affecting ultrasonic wave propagation. For example, whether the pipe contains different types of acoustic propagation media, and the distribution state of the media within the pipe. For the detection of the environment inside the pipe, this parameter can be simplified to the liquid level height inside the pipe, the type of liquid medium (such as water, ethanol, crude oil, refined oil, or other liquid chemicals), and may even include data such as humidity reflecting the state information of the air medium. Third, the structural information of the ultrasonic phased array used for ultrasonic detection. In the three-dimensional ultrasonic imaging task of this embodiment, a two-dimensional ultrasonic array is mainly used as the required ultrasonic phased array. The structural information needs to record the arrangement and three-dimensional coordinates of each element in the array. In practical applications, the arrangement of ultrasonic arrays includes circular, random, spiral, rectangular grid, sparse optimized, or other two-dimensional arrangements. Furthermore, the coupling type of the array needs to be determined, such as air-coupled array, water-immersion coupled array, or liquid-coupled array.

[0037] Based on the above information, this embodiment can use methods such as acoustic finite element analysis to analyze the propagation path of acoustic signals emitted by any array element in any direction within the entire object under test when the ultrasonic phased array is located at any position in the object under test; that is, to establish the required acoustic propagation model.

[0038] 2. Traverse the transceiver array pairs in the ultrasonic phased array, track each sound ray emitted and propagated at a preset angular interval; record each candidate path that meets the preset constraints; and generate the path characteristics of each candidate path.

[0039] In this embodiment, the ultrasonic phased array includes multiple transmitting array elements arranged in a specified manner. and receiving array elements This embodiment iterates through all available transmitting elements in the array. and receiving array elements Forming a transceiver array element pair In practical applications, this embodiment can adopt different signal acquisition strategies for transmit and receive array element pairs for different application scenarios. For example, for full matrix acquisition FMC, all transmit-receive combinations can be traversed; while for sparse FMC or group acquisition, only the effective combinations that are actually acquired need to be traversed.

[0040] When sampling signals by traversing each transmit / receive array element pair, this embodiment uses any one transmit array element. Starting from the base element, sound rays are emitted at preset angular intervals within the beam angle range of the array element. The sound rays propagate in a straight line through the medium. When they intersect with the pipe wall, liquid surface, defect surface, or other boundaries, the reflection direction is calculated according to the law of reflection, and the system continues to trace the next segment of the path. In practical applications, the sound ray emission angle of the emitting array element is adjusted stepwise according to preset angular intervals until the preset beam angle range is traversed. This angular interval can be a fixed interval of different sizes that can be set as needed; for example, in high-resolution detection scenarios, the angular interval is reduced, and vice versa. Alternatively, the angular interval can be adaptively adjusted according to the detection process, for example, reducing the angular interval in key areas.

[0041] During the tracking process, this embodiment records the path characteristics of each acoustic ray in real time. For example, for each SBR acoustic ray, it records its journey from the transmitting element, through 0, 1, 2 or more reflections, to the imaged voxel p, and its return from voxel p to the receiving element. The propagation path. The transmission path can also be traced separately. to p and receiving-side path p to Recombined to form Complete path. In practical applications, the path characteristics recorded for each path in this embodiment may include: number of reflections k, path length, etc. Dissemination time Angle of incidence, angle of reflection, boundary intersection, reflection coefficient, and path energy All path features constitute the label information for that path. Among the path features mentioned above, path length, propagation time, and path energy need to be calculated during the tracking process based on the theoretical propagation path of the corresponding sound ray.

[0042] Assuming that during ray tracing, the ray segment of any sound ray can be represented as... :

[0043] in, The m-th ray segment is the starting point. The propagation direction vector is the unit.

[0044] When the ray intersects with the wall boundary Γ of the object to be measured... ,and x Located in the ray Above; among them, Satisfy the following formula: , Among them, the intersection point The unit normal vector at point is denoted as Then the direction after reflection from the mirror is : , Taking pipeline inspection as an example, the sound ray can be traced to the next reflection path each time it encounters the inner wall of the pipeline, the liquid surface, the interface step, or the defect surface, based on the state of the sound ray reflection.

[0045] Based on this, the path length of any k-th path Satisfy the following formula:

[0046] In the above formula, Represents the coordinates of the endpoint of any m-th path segment; This represents the starting coordinates of any m-th path segment; m represents the segment index of the path. Indicates the number of propagation segments contained in the path.

[0047] Propagation time of any k-th path Then the following equation is satisfied: ; In the above formula, This indicates the speed at which sound waves propagate.

[0048] Furthermore, when the object under test is filled with a non-uniform medium, the propagation path will pass through different propagation media, and the propagation time of the k-th path will be... Satisfy the following formula: ; In the above formula, Indicates the path trajectory; Indicating the path trajectory s The velocity of sound in the medium corresponding to the point.

[0049] In this embodiment, the path energy of any k-th path The calculation formula is as follows: ; In the above formula, To emit energy; and These are the directional gains of the transmitting and receiving array elements, respectively; d 0 represents the initial propagation direction unit vector when the candidate path exits the transmitting element; d M These represent the unit vectors of the final propagation direction when the candidate path reaches the receiving array element; Indicates the first q The incident angle of the secondary reflection is the angle between the direction of the incident sound ray and the normal vector of the reflection boundary at the reflection point. For the first q The reflection coefficient of secondary reflection; Let the attenuation term be due to propagation distance and medium absorption, and satisfy: ; In the above formula, α The medium absorption coefficient, β This is the diffusion index related to acoustic propagation models.

[0050] In addition, in practical applications, after experimental calibration, the path energy can also be directly estimated from the envelope of the A-scan signal. The estimated path energy value... The calculation formula is: , in, For receiving and transmitting array elements The acquired A-scan signal, This refers to a time window centered on predicting the propagation time.

[0051] In practical applications, continuously tracking all sound paths without restriction would result in enormous computational costs. Considering that the energy of sound signals attenuates continuously during propagation, this embodiment only records candidate paths that meet preset constraints and generates path features for each candidate path, while still meeting imaging accuracy requirements. In practical applications, the preset constraints can be set to any one or more of the following: (1) The number of reflections on the current path is less than the maximum number of reflections. .

[0052] (2) The energy of the current path is greater than the energy of the minimum path. .

[0053] (3) The propagation time of the current path is less than the maximum propagation time. .

[0054] (4) The boundary intersection of the current path is within the boundary of the effective imaging area.

[0055] During the sound ray tracing process, if any traced sound ray path violates the preset constraints during propagation, it will be excluded from the candidate path list.

[0056] Third, perform transmit / receive array element matching on each candidate path; and filter the matched candidate paths to obtain a set of valid paths.

[0057] In the array element matching stage of this embodiment, for each transmit / receive array element pair Match the paths that can be connected in its corresponding candidate path set. The voxel to be imaged p and The valid path. Matching conditions include whether the path endpoint falls within the effective aperture or reception angle range of the receiving array element, whether the path propagation time falls within the sampling time window, whether the path incident angle satisfies the array element directivity response, and whether the path passes through an invalid region outside the tube wall.

[0058] After completing the above matching, this embodiment can further classify candidate paths according to the number of reflections into 0-reflection paths, 1-reflection paths, 2-reflection paths, and so on. Secondary reflection paths. A zero-reflection path corresponds to a conventional straight path; a first-reflection or higher path corresponds to a multi-view path formed by the pipe wall or other boundaries. This classification allows subsequent imaging to generate images of straight paths, single-reflection paths, and multiple-reflection paths, respectively.

[0059] Finally, this embodiment combines the path energy, reflection count, and propagation time of each candidate path to filter out the required effective paths. Filtering effective paths helps reduce artifacts and computational overhead introduced by weak paths. The resulting set of effective paths is shown below. Satisfy the following formula:

[0060] In the above formula, p Indicates the voxel to be imaged; Indicates the transmit and receive array elements Candidate paths k Path energy; Indicates the transmit and receive array elements In voxels p Energy along the straight path at the location; η The preset energy ratio threshold; N k Indicate candidate path k The number of reflections; N max Indicates the preset maximum number of reflections; Indicates belonging to the transmit / receive array element pair Candidate paths k The spread time.

[0061] For example, in this embodiment, an energy ratio threshold η can be set, which is the path energy of any candidate reflection path. Greater than or equal to When this happens, the path is retained as a valid focus path. Conversely, when... Less than When the path is removed, it is discarded. The threshold η can be flexibly set according to the pipe material, medium, array frequency, noise level, and imaging target. For example, it can be set to 20% to 80%. In this embodiment, the preferred value is η=50%. Similarly, the upper limit setting of the number of reflections and the propagation time of the path is set. When the number of reflections and the propagation time of any sound ray are too large, the energy of the remaining path will be greatly attenuated.

[0062] IV. Perform three-dimensional ultrasound imaging on the object under test by combining the effective path set.

[0063] In this embodiment, the aforementioned set of effective paths includes effective paths with different reflection counts, path energies, and propagation delays. In order to achieve high-quality multi-view imaging, it is necessary to set differentiated path weights and focusing delays for different types of effective paths.

[0064] For example, the path weight of any valid path in this embodiment. Based on the path energy generation of each effective path, the calculation formula is as follows: ; In the above formula, P ( p ) indicates the participating voxels p The effective path categories or viewpoint set for image fusion; ε is a positive constant to prevent the denominator from being zero, which is a very small positive number. The obtained path weights can be used for subsequent TFM focusing or multipath image fusion.

[0065] During the delay rule generation phase, the total propagation time is calculated for each retained valid path. When the sound velocity in the medium is non-uniform, path integral is used. .Will As a receiving and sending array element pair Focusing delay at voxel p. For the case where there are multiple valid paths for the same transceiver array element pair, multiple sets of delay rules are generated respectively.

[0066] Based on this, the focusing delay of any effective path Based on the propagation time of the current path The generation and calculation formula is: ; In the above formula, This refers to the system trigger delay, zero-point acquisition delay, or calibration delay. In actual imaging, for the same voxel p and the same transceiver array pair... There can be k different types of optional paths with corresponding effective delays.

[0067] Next, combining the path weights and delay rules corresponding to different types of paths, this embodiment performs multi-path TFM focusing based on the A-scan signals acquired during the actual detection stage. The process includes: for each voxel p, sampling and superimposing the A-scan signals acquired by each transceiver array element according to the corresponding effective path delay to obtain the image intensity corresponding to different reflection times; then using coherent superposition, envelope superposition, amplitude-weighted superposition, or energy-weighted superposition, and further summing, taking the maximum value, weighting by path energy, or fusing by statistical confidence for multiple reflection times images to obtain the final three-dimensional ultrasound image.

[0068] In detail, during the three-dimensional ultrasound imaging stage of this embodiment, according to the first... k Voxels generated by the effective path of secondary reflection p The image intensity satisfies the following formula: ; In the above formula, and These represent the number of transmitting and receiving elements of the ultrasonic phased array, respectively. This represents the sampled value of the A-scan signal at the predicted propagation time.

[0069] If imaging is performed separately for different reflection counts or different path families, the final three-dimensional image will be... It can be generated by the following formula:

[0070] Wherein, F represents the preset image fusion method. In this embodiment, the fusion method of the three-dimensional ultrasound image of the object under test adopts weighted summation, maximum value, Tippet statistical fusion, Fisher statistical fusion or other confidence fusion methods.

[0071] The expression for weighted summation and fusion is as follows:

[0072] In the above formula, This represents the image intensity at voxel p generated based on weighted fusion; P ( p ) indicates the participating voxels p Effective path categories or viewpoint sets for image fusion; Indicates the first k Class path image in voxels p The weighted summation and fusion weights are calculated based on the weighted summation and fusion weights at the specified points. k The path energy, signal-to-noise ratio, background noise variance, or path confidence of the path are determined.

[0073] The expression for Tippet fusion is: ; In the above formula, Indicates voxels generated based on weighted fusion p Image intensity at that location; Indicates the first k Class path image in voxels p Tippet fusion weights at the location.

[0074] The expression for Fisher fusion is: ; In the above formula, This indicates voxels generated based on Fisher fusion. p Image intensity at that location; Indicates the first k Class path image in voxels p Fisher fusion weights at the location.

[0075] Example 2

[0076] The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method provided in Example 1 is essentially a data processing method. In order to better apply this scheme, this example further provides a computer program product and its corresponding data processing module.

[0077] The computer program product provided in this embodiment includes a computer program that, when executed by a processor, implements the ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in Embodiment 1, and then performs three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

[0078] The data processing module provided in this embodiment includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the ray tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in Embodiment 1, and then performs three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

[0079] In practical applications, the data processing module provided in this embodiment is a computer device. This computer device can be an embedded computing module or chip; it can also be a computing terminal capable of executing programs. Examples include: smartphones, tablets, laptops, desktop computers, rack servers, blade servers, tower servers, or cabinet servers (including standalone servers or server clusters composed of multiple servers), etc.

[0080] The computer device in this embodiment includes, but is not limited to, a memory and a processor that can be interconnected via a system bus. In this embodiment, the memory (i.e., the readable storage medium) includes flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, etc. In some embodiments, the memory can be an internal storage unit of the computer device, such as the hard disk or RAM of the computer device. In other embodiments, the memory can also be an external storage device of the computer device, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc. Of course, the memory can also include both internal storage units and external storage devices of the computer device. In this embodiment, the memory is typically used to store the operating system and various application software installed on the computer device. Furthermore, the memory can also be used to temporarily store various types of data that have been output or will be output. In some embodiments, the processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. The processor is typically used to control the overall operation of a computer device.

[0081] Example 3

[0082] Based on the solutions in Embodiments 1 and 2, this embodiment further provides a pipeline ultrasonic inspection robot, which includes a robot body, an ultrasonic phased array radar, and a data processing module. The ultrasonic phased array radar is mounted on the robot body. The ultrasonic phased array radar is used to acquire the A-scan signal inside the pipeline to be inspected. Considering that in pipeline inspection, the target object is mainly attached to the inner wall of the pipeline, corresponding to the outer edge of the space to be inspected, therefore, as... Figure 5 As shown, the ultrasonic phased array radar of this embodiment includes several sets of transceiver array elements arranged in a ring along the cross-section of the pipe to be tested. In the ring-structured radar, the sampling signal is more concentrated in the outer cylindrical region within the cylindrical detectable range, which is the key detection area, while the sampling signal in the central cylindrical region is relatively sparse.

[0083] The data processing module is electrically connected to the ultrasonic phased array radar; the data processing module has a pre-stored geometric model of the pipe to be tested; and it is used to perform three-dimensional spatial imaging of the pipe to be tested according to the ray tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in Example 1, based on the geometric model of the pipe to be tested and the A-scan signal acquired by the ultrasonic phased array, thereby generating a three-dimensional ultrasonic image inside the pipe.

[0084] In this embodiment, for the application scenario of pipeline inspection, the data processing module is also used to perform threshold segmentation, connected component analysis, Radon pipe transformation, cylindrical coordinate projection or 3D point cloud fitting on the 3D ultrasonic image, thereby obtaining the location, width, height, circumferential angle, axial distance and confidence information of pipeline interface, blockage, deposit, foreign object, local deformation or other defects.

[0085] Test Experiment

[0086] To verify the performance of the ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method provided by this invention, technicians manufactured corresponding samples and conducted simulations and tests on them.

[0087] I. Design of Ultrasonic Phased Array Radar

[0088] Different types of ultrasonic phased array radars can affect the final imaging quality. This experiment first tested the performance differences when the probe uses different structures and beam angles.

[0089] 1.1 Probe Structure

[0090] When testing in a pipeline environment, this embodiment sets the probe base in a disc shape that matches the inner diameter of the pipeline, and then sets up transceiver array pairs on it. The distribution of the transceiver array pairs for testing includes, for example: Figure 6The two arrays shown are, firstly, the Ring24 array, which contains 24 groups of array elements arranged in a ring shape, and secondly, the Rand64 array, which contains 64 groups of array elements arranged in a disk shape. This experiment was conducted in... Figure 7 Performance tests were conducted on related products in a scenario where irregularly shaped wooden blocks blocked the sample inside a pipe. The test employed a two-dimensional air-coupled array mode, and FMC data was acquired using the same acquisition controller for multiplexing. The performance of the two arrays under different fusion methods is shown in the table below. Table 1: Performance Comparison of Different Arrays and Fusion Methods in the Verification Experiment

[0091] In practical imaging of pipeline environments, the ring-shaped Ring24 array reduces data acquisition compared to the Rand64 array; sparse arrays help shorten data acquisition time. The two probes show little difference in their ability to resolve various defects on the pipeline wall; while the latter (Rand64 array) is stronger at resolving blockages in the center of the pipeline, the former's imaging results still reflect the morphology of the blockage. Considering the latter has more transceiver array pairs, resulting in higher data processing volume and power consumption, and longer data acquisition time, the increased cost and power consumption are not worthwhile compared to the improved imaging quality. In conclusion, for pipeline inspection applications, a ring-shaped ultrasonic phased array should still be preferred.

[0092] 1.2 Beam Angle

[0093] In the path energy screening stage, this experiment measured the distribution of effective paths for the transceiver elements of the ring structure in a pipeline environment under different beam angles. Figure 8 Part (a) and Figure 8 Part (b) shows the possible acoustic path diagrams of a set of ultrasonic transceiver pairs in a rough pipe when the beam angle of the excitation and receiving transducers is 20 degrees. Figure 8 Part (c) and Figure 8 Section (d) shows the possible acoustic path rays of a set of ultrasonic transducer transceivers in a rough pipe when the beam angles of the excitation and receiving transducers are 80 degrees. Cyan represents acoustic path rays with low reflection energy, and reddish-purple represents acoustic path rays with high reflection energy, displayed using MATLAB's COOL colorimetry. Based on the results in the figure, in actual products, the beam angles of each element in probes with different structures can be flexibly set to avoid interference.

[0094] Visualization of 2D and 3D ultrasound imaging results

[0095] Furthermore, based on the acoustic ray tracing algorithm and a linear time-invariant system model, this experiment simulated and analyzed the multipath propagation effect of acoustic rays in a hollow annular ultrasonic array within a typical pipe structure and the corresponding ultrasonic imaging results. The simulation and test results were then compared and verified. The obtained simulation and test results are as follows: Figure 9 As shown in the figure. The red dashed circle in the inner circle indicates the arrangement of the array on the pipe cross-section, and the gray area represents the spatial distribution of reflectors obtained through imaging reconstruction.

[0096] During the simulation, multipath propagation information calculated using the ray tracing algorithm is combined with a linear time-invariant system to model the echo signal, thus obtaining the three-dimensional ultrasonic reflection distribution of the corresponding structure. The simulated ultrasonic imaging results for the pipe interface structure and the low-sediment scenario are shown below. Figure 9 Part (a) in Figure 9 As shown in part (b) of the figure, the interface structure forms a relatively obvious annular reflection distribution near the pipe cross-section, reflecting the strong reflection effect of the interface boundary on the sound waves; while the sediment scene forms a non-uniformly distributed local reflection area at the bottom of the pipe, corresponding to the geometric shape of the sediment accumulation at the bottom of the pipe.

[0097] Correspondingly, the ultrasonic imaging results of the interface structure and deposit structure obtained under actual experimental conditions are as follows: Figure 9 Part (c) and Figure 9 As shown in section (d) of the model, the actual experimental imaging results show good consistency with the simulation results in terms of overall spatial distribution. For example, the interface structure also exhibits a reflective area distributed along the pipe cross-section, while the sediment scene is mainly concentrated in the bottom region of the pipe, forming a discrete reflective distribution. Although the reflective area in the experimental image shows a certain degree of diffusion compared to the simulation results due to factors such as experimental environment noise, limited array aperture, and multipath propagation superposition, its main spatial characteristics still remain consistent with the simulation prediction. Therefore, the imaging results have met the requirements for detection accuracy in actual pipe inspection, and these imaging results can provide effective auxiliary information for non-destructive testing of large-scale buried pipes.

[0098] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A three-dimensional spatial imaging method based on ray tracing ultrasonic phased array, characterized in that, It includes:

1. Obtain the geometric model of the object under test; and establish an acoustic propagation model for ultrasonic phased array detection of the object under test based on the state parameters of the object under test.

2. Traverse the transceiver pairs in the ultrasonic phased array and track each sound ray emitted and propagated at a preset angular interval; Record each candidate path that meets the preset constraints; It also generates path features for candidate paths, including: number of reflections, path length, propagation time, incident angle, reflection angle, boundary intersection, reflection coefficient, and path energy; 3. Perform transmit / receive array element matching on each candidate path; and filter the matched candidate paths using the following formula to obtain the set of effective paths. : ； In the above formula, p Indicates the voxel to be imaged; Indicates the transmit and receive array elements Candidate paths k Path energy; Indicates the transmit and receive array elements In voxels p Energy along the straight path at the location; η The preset energy ratio threshold; N k Indicate candidate path k The number of reflections; N max This indicates the preset maximum number of reflections; Indicates belonging to the transmit / receive array element pair Candidate paths k The duration of transmission; t max Indicates the preset maximum propagation time; IV. Performing three-dimensional ultrasound imaging of the object under test by combining the effective path set, including: The path weights and focusing delays of the effective paths are generated; the A-scan signals acquired by each transceiver array element are sampled and superimposed according to the effective path corresponding to each voxel to obtain the image intensity of the specified number of reflections; the image intensities of different number of reflections or different path families are fused to obtain the three-dimensional ultrasound image of the object under test.

2. The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method according to claim 1, characterized in that: During ray tracking, the preset angle intervals of the transmitting array elements can be either fixed or adaptive. Furthermore, the constraints satisfied by the recorded candidate paths include any one of the following: (1) The number of reflections on the current path is less than the maximum number of reflections. ; (2) The energy of the current path is greater than the energy of the minimum path. ; (3) The propagation time of the current path is less than the maximum propagation time. ; (4) The boundary intersection of the current path is within the boundary of the effective imaging area; If any path being tracked violates the preset constraints during propagation, it will be excluded from the candidate paths.

3. The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method according to claim 1, characterized in that: Path length of any k-th path Satisfy the following formula: ； In the above formula, Represents the coordinates of the endpoint of any m-th path segment; This represents the starting coordinates of any m-th path segment; m represents the segment index of the path. Indicates the number of propagation segments contained in the path; Propagation time of any k-th path Satisfy the following formula: ； In the above formula, Indicates the speed at which sound waves propagate; If the path passes through different propagation media, then the propagation time of the k-th path is... Satisfy the following formula: ； In the above formula, Indicates the path trajectory; Indicating the path trajectory s The velocity of sound in the medium corresponding to the point.

4. The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method according to claim 3, characterized in that: Path energy of any k-th path The calculation formula is as follows: ； In the above formula, To emit energy; and These are the directional gains of the transmitting and receiving array elements, respectively; d 0 represents the initial propagation direction unit vector when the candidate path exits the transmitting element; d M These represent the unit vectors of the final propagation direction when the candidate path reaches the receiving array element; Indicates the first q The angle of incidence for the secondary reflection; For the first q The reflection coefficient of secondary reflection; Let the attenuation term be due to propagation distance and medium absorption, and satisfy: ； In the above formula, α The medium absorption coefficient, β This is the diffusion index related to acoustic propagation models.

5. The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method according to claim 4, characterized in that: Path weight of any valid path Based on the path energy generation of each effective path, the calculation formula is as follows: ； In the above formula, ε is a positive constant to prevent the denominator from being zero; P ( p ) indicates the participating voxels p Effective path categories or viewpoint sets for image fusion; Focusing delay of any valid path Based on the propagation time of the current path The generation and calculation formula is: ； In the above formula, This refers to the system trigger delay, zero-point acquisition delay, or calibration delay.

6. The ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method according to claim 5, characterized in that: In the three-dimensional ultrasound imaging stage, according to the first k Voxels generated by the effective path of secondary reflection p The image intensity satisfies the following formula: ； In the above formula, and These represent the number of transmitting and receiving elements of the ultrasonic phased array, respectively. This represents the sampled value of the A-scan signal at the predicted propagation time. And / or, the fusion method for the three-dimensional ultrasound images of the object under test adopts weighted summation fusion, Tippett statistical fusion, Fisher statistical fusion or other confidence fusion methods; And / or, the expression for weighted summation fusion is: ； in, This represents the image intensity at voxel p generated based on weighted fusion; Indicates the first k Class path image in voxels p Weighted summation and fusion weights at each location; And / or, the expression for Tippet fusion is: ； In the above formula, This represents the image intensity at voxel p generated based on weighted fusion; This represents the Tippet fusion weight at voxel p for the k-th type of path image; And / or, the expression for Fisher fusion is: ； In the above formula, This represents the image intensity at voxel p generated based on Fisher fusion; This represents the Fisher fusion weight of the k-th path image at voxel p.

7. A computer program product comprising a computer program, characterized in that: When the computer program is executed by the processor, it implements the ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in any one of claims 1-6, and then performs three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

8. A data processing module comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, it implements the ray-tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in any one of claims 1-6, and then performs three-dimensional spatial imaging of the object under test based on the geometric model of the object under test and the A-scan signal acquired by the ultrasonic phased array.

9. A pipeline ultrasonic inspection robot, comprising: The robot itself, An ultrasonic phased array radar, mounted on the robot body, includes several sets of transceiver array elements arranged in a ring along the cross-section of the pipe to be tested, and is used to acquire the A-scan signal inside the pipe to be tested. A data processing module is electrically connected to an ultrasonic phased array radar; the data processing module pre-stores a geometric model of the pipe to be tested; and is used to perform three-dimensional spatial imaging of the pipe to be tested using the ray tracing-based ultrasonic phased array three-dimensional spatial imaging method as described in any one of claims 1-6, based on the geometric model of the pipe to be tested and the A-scan signal acquired by the ultrasonic phased array, to generate a three-dimensional ultrasonic image inside the pipe.

10. The pipeline ultrasonic inspection robot according to claim 9, characterized in that: The data processing module is also used to perform threshold segmentation, connected component analysis, Radon pipe transformation, cylindrical coordinate projection, or 3D point cloud fitting on the three-dimensional ultrasound images, thereby obtaining the location, width, height, circumferential angle, axial distance, and confidence information of pipe interfaces, blockages, deposits, foreign objects, local deformations, or other defects.

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