Laser ultrasonic scanning system for basin-type insulator detection

Abstract

The invention discloses a laser ultrasonic scanning system for basin-type insulator detection. The laser ultrasonic scanning system comprises a mechanical arm, a clamping mechanism, a laser excitation module, a laser ultrasonic receiving module and a control and data processing module, the clamping mechanism is installed at the tail end of the mechanical arm and used for clamping and positioning the insulator and cooperating with the mechanical arm to achieve three-dimensional posture adjustment and rotation around the axis of the clamping mechanism. The control and data processing module processes the echo signal, and performs focusing reconstruction on circumferential scanning data by adopting a synthetic aperture delay superposition imaging method to obtain a B scanning image of a corresponding section; after a plurality of B scanning images are obtained at multiple axial positions, projection convergence and axial splicing are carried out by selecting a defect related depth range to form a C scanning image taking an annular position and an axial position as coordinates, so that visual characterization of defect expansion distribution is realized. And on the basis of the B scanning image and the C scanning image, identifying an abnormal reflection region of the defect, and realizing defect positioning, quantitative evaluation and report output in combination with echo features.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and particularly relates to a laser ultrasonic scanning system for testing pot-type insulators, used to detect defects in pot-type insulators. Background Technology

[0002] The basin-type insulators widely used in power systems are typically composed of multiple layers of materials, including epoxy resin and metal connectors, bonded together. The quality of this interfacial bonding directly affects the insulator's mechanical strength and long-term operational reliability. Defects such as debonding, voids, or cracks at the resin-metal interface can easily lead to decreased electrical performance or even serious accidents like insulator bursting or flashover. Therefore, there is an urgent need for highly sensitive non-destructive testing of internal interface defects in insulators.

[0003] In existing projects, insulator quality testing is mainly carried out using methods such as power frequency withstand voltage, sampling destructive testing, and conventional piezoelectric ultrasound and X-ray. However, the former two require power outages or sample destruction, resulting in low efficiency and high cost. Piezoelectric ultrasound testing relies on coupling agents and rigid transducers, which are difficult to adapt to the large curvature surfaces of insulator skirts and basin structures. In multi-layer bonded structures, poor coupling, beam deflection, and energy scattering are also prone to occur, resulting in a limited detection rate for deeply buried small defects.

[0004] Laser ultrasonic technology utilizes high-energy pulsed lasers to non-contactly excite broadband ultrasonic waves on the surface being tested, and then receives the surface vibration signals through optical means, forming a fully optical non-destructive testing system. This technology has advantages such as not requiring coupling agents, high spatial resolution, long-distance deployment, and adaptability to extreme environments such as high temperature, high pressure, and strong corrosion. It has shown higher sensitivity and resolution than traditional ultrasound in the detection of delamination and debonding defects at the interface of multilayer composite materials.

[0005] However, existing laser ultrasonic systems are mostly used in laboratory research on aerospace composite material plates, pipes, and other structures. These systems are large, have limited scanning methods, and lack dedicated testing devices and automated application solutions for axisymmetric curved multilayer bonded components like insulators. This makes it difficult to meet the engineering requirements for batch testing and efficient screening of insulators. Furthermore, existing systems often use translational or two-dimensional scanning platforms to drive the laser and detector movement, which is unsuitable for testing basin-type insulators in arbitrary spatial orientations. Maintaining the stability of the laser ultrasonic signal and the accuracy of interface defect identification under complex conditions such as surface contamination and water stains are also problems that current technology needs to solve. Summary of the Invention

[0006] In view of this, the present invention proposes a laser ultrasonic scanning system for the inspection of basin-type insulators. This system is a robotic arm clamping and laser ultrasonic scanning system designed for the curved surface structure of basin-type insulators, aiming to overcome the following problems existing in the prior art:

[0007] Internal defect detection is difficult: Traditional ultrasonic testing relies on coupling agents and contact probes, which makes it difficult to achieve stable coupling in the complex curved surfaces and narrow gaps of basin insulators. The sensitivity and reliability of detecting hidden defects such as internal debonding and cracks are insufficient.

[0008] Low level of automation: Existing testing methods mostly rely on manual hand-held probes and mechanical adjustments, which are cumbersome, have poor repeatability, and make it difficult to achieve consistent non-destructive testing of large batches of insulators;

[0009] Poor adaptability to complex spatial postures: In actual installation environments, the posture of basin-type insulators is varied and space is limited, making it difficult for traditional fixed or two-dimensional scanning mechanisms to achieve full circumference coverage and multi-angle scanning.

[0010] The curved surface scanning trajectory is difficult to control precisely: the lack of a motion coordinate system unified with the geometric center axis of the insulator and high-precision scanning trajectory planning leads to unstable laser excitation and receiving positions, affecting the accuracy of defect imaging and quantitative analysis.

[0011] The specific technical solution is as follows: This invention provides a laser ultrasonic scanning system for testing pot-type insulators. The system includes a robotic arm, a clamping mechanism, a laser excitation module, a laser ultrasonic receiving module, and a control and data processing module. The modules work together to achieve stable clamping of pot-type insulators, three-dimensional attitude adjustment, rotational scanning around the axis, and defect imaging and quantitative assessment.

[0012] The robotic arm provides multi-degree-of-freedom motion capability to achieve spatial attitude adjustment, scanning position positioning and stable holding of the basin insulator; the robotic arm can achieve attitude adjustment of the end effector in the roll, pitch and yaw directions, and has rotational freedom along the clamping axis, so that the basin insulator under test can rotate continuously or stepwise around its own axis, thereby forming a circumferential scanning path and a multi-circle scanning path.

[0013] The clamping mechanism, located at the end of the robotic arm, is used to clamp and precisely position the basin-type insulator. This mechanism ensures the clamp axis coincides with the geometric center axis of the basin-type insulator, unifying the coordinate system at the end of the robotic arm with the axial coordinate system of the insulator, providing a unified spatial reference for circumferential scanning trajectory planning and imaging positioning. The clamping mechanism can adaptively clamp basin-type insulators of different specifications and provides locking during scanning to prevent slippage or loosening. The laser excitation module includes a pulsed laser, a focusing lens, and a laser-induced acoustic enhancement medium. Under the triggering and energy adjustment of the control and data processing module, the laser excitation module outputs laser pulses and excites ultrasonic waves on the surface of the basin-type insulator. The laser-induced acoustic enhancement medium is placed on a lens or intermediate carrier in the laser optical path to improve light absorption and photothermal conversion efficiency, thereby enhancing the amplitude of the ultrasonic signal generated by the laser excitation. Under the trajectory control of the robotic arm, the laser excitation spot moves circumferentially along the inner or outer surface of the basin-type insulator at a set step distance to cover the target detection area.

[0014] The laser ultrasonic receiving module includes a laser Doppler vibrometer and a synchronous high-speed data acquisition card. The laser Doppler vibrometer is used to convert the micro-vibrations on the surface of the basin insulator into electrical signals for output. The high-speed data acquisition card is used to perform high-speed synchronous sampling of the electrical signals and to achieve time synchronization with the control and data processing module to ensure strict time matching between excitation and reception.

[0015] The control and data processing module includes at least a motion control unit, a laser control unit, a signal processing unit, and an imaging and damage assessment unit.

[0016] (1) The motion control unit is used to control the robotic arm to achieve the rotation and attitude adjustment of the basin insulator around the axis according to the preset scanning trajectory or adaptive planning algorithm, and to generate a circumferential scanning path and a multi-circle scanning path covering the key area of ​​the insulator.

[0017] (2) The laser control unit is used to trigger and control the pulsed laser, and set parameters such as pulse energy and repetition frequency, while synchronizing with the high-speed data acquisition card.

[0018] (3) The signal processing unit is used to perform noise reduction, filtering, envelope extraction, time-frequency analysis and feature extraction on the acquired laser ultrasonic signal to obtain echo features related to internal debonding, voids, cracks and other defects.

[0019] (4) The imaging and defect assessment unit is used to perform the synthetic aperture time delay superposition imaging method to focus and reconstruct the echo data obtained by circumferential scanning and multi-circle scanning, forming the imaging results of internal and interface defects of the basin insulator. Based on the time-space distribution characteristics of the imaging results, the unit outputs the spatial location, equivalent size and reflection amplitude of the defects and other severity indicators, and generates a visual inspection report.

[0020] Based on the above system structure, the system performs the following process when performing non-destructive testing on pot-type insulators: clamping and calibrating the axis; setting the circumferential resolution and planning the scanning trajectory in the control and data processing module according to the insulator's geometric parameters; driving the robotic arm to rotate the insulator around the axis according to the planned trajectory and completing the synchronous acquisition of excitation and reception point by point; preprocessing and extracting features from the acquired signals; and performing focused reconstruction based on the synthetic aperture time-delay superposition imaging method to complete defect identification and quantitative assessment.

[0021] The present invention has the following beneficial effects:

[0022] 1. Non-contact detection, adaptable to complex curved surfaces: Using laser excitation and optical reception, there is no need for contact probes and coupling agents. It can adapt to the complex curved surfaces and narrow gap areas of basin insulators, improving the applicability of internal and interface defect detection.

[0023] 2. High degree of automation and good repeatability: Stable clamping, rotation around the axis and trajectory planning are achieved through robotic arms and clamping mechanisms, reducing the uncertainty caused by manual hand-held probes and mechanical adjustments, improving detection efficiency and consistency, and making it suitable for batch detection.

[0024] 3. Strong posture adaptability and wide coverage: The robotic arm's multi-degree-of-freedom posture adjustment capability can adapt to different installation postures, different installation heights, and space-constrained working conditions; combined with circumferential scanning and multi-circle scanning paths, it can achieve full circumferential coverage and multi-angle scanning of key areas.

[0025] 4. Enhanced signal amplitude and improved signal-to-noise ratio: By setting up a laser-induced acoustic enhancement medium, the efficiency of light absorption and photothermal conversion is improved, thereby enhancing the amplitude of the ultrasonic signal generated by laser excitation and improving the echo signal-to-noise ratio and defect detectability.

[0026] 5. Excellent imaging focusing effect and quantitative assessment of defects: Synthetic aperture time-delay superposition focusing reconstruction is performed on the data obtained by circumferential scanning to improve the contrast and spatial resolution of defect reflection, realize the location of defects such as debonding, voids, and cracks, and quantitatively assess indicators such as equivalent size and reflection amplitude, and can automatically generate a visual report.

[0027] 6. Unified coordinates and more accurate positioning: By calibrating the clamp axis, the clamp axis is aligned with the geometric center axis of the insulator, realizing spatial registration of scanning points. This facilitates the accurate mapping of defect information onto the three-dimensional model of the insulator, improving the accuracy of positioning and evaluation. Attached Figure Description

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0029] Figure 1 A three-dimensional diagram of a laser ultrasonic scanning system for testing basin-type insulators provided in an embodiment of the present invention;

[0030] Figure 2 A three-dimensional view of the clamping mechanism provided in an embodiment of the present invention;

[0031] Figure 3 A flowchart of the robotic arm gripping and laser ultrasonic scanning system provided in an embodiment of the present invention;

[0032] Figure 4 A flowchart of a laser excitation system provided for an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0034] To achieve the above objectives, this invention proposes a laser ultrasonic scanning system for testing basin-type insulators, such as... Figure 1 , Figure 3 As shown, the system includes: a robotic arm 1, a clamping mechanism 2, a laser excitation module 3, a laser ultrasonic receiving module 4, and a control and data processing module 5. The modules work together to complete the three-dimensional attitude adjustment and circumferential laser ultrasonic scanning of the basin insulator.

[0035] Robotic arm 1: The robotic arm 1 is used to provide multi-degree-of-freedom motion, and its joint structure includes:

[0036] Base rotation joint: used to realize the horizontal rotation of the robotic arm 1 relative to the mounting base, so as to adjust the overall working position according to the on-site space environment. Preferably, it is a motor-driven joint that can rotate continuously from 0 to 360°.

[0037] Lower arm pitch joint: Located between the base and the lower arm, it is used to drive the lower arm to pitch around the horizontal axis, thereby changing the extension distance and height range of the robotic arm to adapt to different installation heights and detection radii;

[0038] Upper arm pitch joint: Located between the lower arm and the upper arm, it is used to make fine pitch adjustments to the upper arm posture, while maintaining the stability of the fixture axis direction and improving the uniformity of the scanning path coverage on the curved surface of the basin insulator.

[0039] Wrist multi-degree-of-freedom rotary joint: Located at the end of the upper arm, it is used to realize multi-degree-of-freedom fine adjustment of the end effector in the roll, pitch and yaw directions, so that the clamping mechanism 2 and the laser optical path can automatically adjust the incident angle and receiving angle according to the local curvature of the insulator, thereby optimizing the coupling conditions between laser excitation and laser ultrasonic reception.

[0040] Through the linkage of the aforementioned joints, the robotic arm can achieve rotation, pitch, and spatial attitude adjustment of the tested basin insulator, enabling the insulator to obtain controllable three-dimensional motion capability in the system coordinate system.

[0041] Furthermore, the robotic arm 1 has rotational freedom along the clamp axis, enabling the insulator under test to rotate continuously or stepwise around its own axis from 0 to 360°. The robotic arm also has pitch and yaw degrees of freedom to adapt to different installation postures, different installation heights and space-constrained working conditions, and to achieve adaptive adjustment to complex on-site testing environments.

[0042] like Figure 2 As shown, clamping mechanism 2: The clamping mechanism 2, located at the end of the robotic arm 1, is used to clamp and precisely position the basin-type insulator. The clamping mechanism includes:

[0043] The gripping base 21, which is rigidly connected to the wrist of the robotic arm, is used to provide overall rigid support for the gripper and serve as a reference for the coordinate system of the robotic arm's end effector.

[0044] Three grippers 22 are evenly distributed along the circumference. Each gripper 22 can open and close synchronously or independently in the radial direction to clamp the metal flange or outer edge of the insulator, thereby achieving adaptive clamping of pot insulators of different specifications.

[0045] The flexible pad 23 is set on the inner surface of the gripper. The flexible pad 23 is made of elastic materials such as rubber and polyurethane. It is used to increase friction, buffer the clamping force and prevent damage to the outer surface coating or enamel of the insulator.

[0046] The locking mechanism 24 is used to self-lock the position of the gripper after clamping to the predetermined clamping force, so as to prevent the insulator from slipping or loosening due to mechanical vibration, inertial force or operating condition disturbance during the scanning process.

[0047] The fixture axis calibration structure 25 is used to make the fixture axis coincide with the geometric center axis of the basin insulator. Through mechanical or optical calibration, the coordinate system of the end of the robotic arm and the axial coordinate system of the insulator are unified, thereby providing a unified spatial reference for subsequent circumferential scanning trajectory planning and defect imaging.

[0048] Through the above structural design, the clamping mechanism 2 can achieve reliable clamping without damaging the insulator and provide a stable geometric reference for laser excitation and reception.

[0049] like Figure 4 As shown, the laser excitation module 3 includes a pulsed laser and a laser acoustic enhancement medium disposed in the optical path. It is electrically connected to the laser control unit and is used to generate laser pulses for exciting ultrasonic waves under the triggering and energy regulation of the control unit.

[0050] The constraint relationship between the energy density and thermal damage threshold generated by pulsed laser on the insulator surface can be expressed as:

[0051] ;

[0052] In the formula, This represents the energy density of a single pulse acting on the surface of the insulator. The energy of a single laser pulse; The equivalent radius of the focused laser spot; The effective area of ​​the laser spot; The thermal damage threshold energy density of the material surface. When This ensures that the laser excitation process will not cause thermal damage to the surface of the insulator.

[0053] The laser-induced acoustic enhancement medium is coated on the lens or intermediate carrier in the laser optical path to improve the light absorption rate and photothermal conversion efficiency, thereby enhancing the amplitude of the ultrasonic signal generated by laser excitation.

[0054] Optionally, the laser-induced acoustic enhancement medium is a two-dimensional layered material of titanium carbide based on Mxene, preferably an Mxene / PDMS composite enhancement medium loaded with gold nanoparticles. Through the synergistic effect of noble metal nanoparticles and two-dimensional materials, efficient absorption and rapid thermal expansion of laser energy are achieved, thereby generating high signal-to-noise ratio laser ultrasound on the surface of the insulator without the need for traditional acoustic coupling agents.

[0055] The laser-excited spot can be moved circumferentially on the inner or outer surface of the insulator basin by optical focusing and robotic arm trajectory control to form a scanning path covering the entire working area.

[0056] The method of identifying defects such as debonding and voids through interface echo in this invention is as follows:

[0057] For an insulator-interface structure composed of multiple dielectric layers, the acoustic impedance of each layer is defined as:

[0058] ;

[0059] In the formula, For the first Acoustic impedance of the layered medium; For the first The density of the layer medium; For the first The longitudinal wave propagation velocity in the layered medium. Under perpendicular incidence conditions, the first... Layer and First The reflection coefficient of the layer-medium interface can be expressed as:

[0060] ;

[0061] In the formula, For the first The amplitude reflection coefficient of each interface; , These represent the acoustic impedances of the media on either side of the interface. When defects such as debonding or voids exist at the interface, the difference in acoustic impedance between the two sides is... Increase, making The amplitude of the interface echo is significantly increased, which is beneficial for defect detection and identification.

[0062] The laser ultrasound receiving module 4 includes a high-speed data acquisition card that is synchronized with the laser Doppler vibration meter and the control and data processing module 5.

[0063] A laser Doppler vibration meter is used to convert micro-vibrations on the surface of an insulator into light intensity or phase changes and output electrical signals; the receiving spot is set near the excitation point or in an area at a predetermined distance from the excitation point to receive transmitted waves, reflected waves or surface wave signals.

[0064] Furthermore, by adjusting the robotic arm's posture and the coordinates of the end effector, a predetermined angle is formed between the received light beam and the normal to the insulator surface, thereby optimizing the acquisition efficiency and signal-to-noise ratio of the reflected light signal.

[0065] The high-speed data acquisition card and the control unit of the laser excitation module 3 achieve time synchronization, which is used to perform high-speed and synchronous sampling of the ultrasonic echo signal output by the laser Doppler vibrometer, providing high time resolution data for subsequent signal processing and imaging.

[0066] Control and data processing module 5 mainly includes:

[0067] Motion control unit: Based on a preset scanning trajectory or adaptive planning algorithm, controls the robotic arm to achieve rotation and attitude adjustment of the insulator around the axis, and generates circumferential and multi-circle scanning paths covering the key areas of the insulator;

[0068] Laser control unit: Triggers and controls the pulsed laser, sets parameters such as pulse energy and repetition frequency, and synchronizes with the data acquisition card to ensure strict time matching between excitation and reception;

[0069] Signal processing unit: performs noise reduction, filtering, envelope extraction, time-frequency analysis and feature extraction on the acquired laser ultrasonic signals, and identifies echo features related to internal debonding, voids, cracks and other defects;

[0070] Imaging and Flaw Assessment Unit: Based on a time-lapse imaging method using circumferential synthetic aperture, the unit focuses and reconstructs laser-ultrasonic echo data obtained from circumferential and multi-circle scans, and maps the focused intensity results to grayscale to obtain B-scan images of the corresponding cross-sections. Combining the temporal-spatial distribution characteristics of the imaging results, the unit extracts and outputs severity indicators such as the spatial location, equivalent size, and reflection amplitude of defects like debonding, voids, and cracks, and automatically generates a visual inspection report.

[0071] To achieve the "focused reconstruction and generation of B-scan images" function of the aforementioned imaging and defect assessment unit, this invention employs the Synthetic Aperture Time Delay Stacking (SAFT) method to perform time delay correction and stacked focusing on the laser ultrasonic echo data obtained from circumferential and multi-circle scans. The calculation process of the SAFT imaging algorithm is given below, which is used to reconstruct the focused imaging intensity of pixels within the imaging region from the echo signals at each scan position, and then generate a B-scan image of the corresponding cross-section through grayscale mapping.

[0072] With the insulator axis as In the spatial coordinate system of the axes, the robot arm pose at each circumferential scanning position is converted into spatial coordinates. The area to be imaged is discretized into a number of spatial pixels. Then the spatial pixels With the The distance between each scan position can be expressed as:

[0073] ;

[0074] Under the condition that the excitation and reception are approximately co-located, the total propagation time of the ultrasonic wave from the scanning position to the pixel and back can be expressed as:

[0075] ;

[0076] In the formula, Spatial pixels With the The distance between each scan position; The longitudinal wave propagation velocity in the insulator material; This represents the corresponding round-trip propagation time.

[0077] For the The time-domain ultrasound signals acquired at each scanning location are filtered and envelope extracted to obtain the envelope signal. For the pixels in the imaging space The imaging intensity function is constructed using the Synthetic Aperture Delay Stacking (SAFT) method:

[0078] ;

[0079] In the formula, Spatial pixels The intensity of the focused imaging; The number of circumferential scan positions involved in imaging; For the first The envelope signal at each scan position; Spatial pixels The corresponding theoretical propagation time; For the first The weighting coefficients for each scanning position can be set according to factors such as the incident angle and signal-to-noise ratio to balance the contributions of different viewing angles. By delaying and superimposing echoes from multiple angles, the focusing contrast and spatial resolution of defect reflections can be significantly improved.

[0080] To facilitate the generation of grayscale images, the focused imaging intensity is normalized and logarithmically compressed to obtain pixel grayscale values:

[0081] ;

[0082] ;

[0083] In the formula, , These are the minimum and maximum focusing intensities within the current imaging region, respectively. The normalized intensity of the spatial pixel; To prevent small positive numbers with odd logarithms; For mapping to The range of grayscale values.

[0084] The synthetic aperture time-delay stacking (SAFT) imaging method is used to perform time-delay correction and stacking on the echo data obtained from the circumferential scan to obtain the focused imaging intensity of the pixels. ;right Normalization and grayscale mapping are performed to construct a B-scan image.

[0085] Based on B-scan images, the imaging unit can further combine normalized amplitude, energy index and threshold criteria to mark areas with significantly abnormal focusing intensity, so as to realize automatic identification and quantitative assessment of defects such as debonding, voids and cracks inside and at the interface of insulators.

[0086] Furthermore, the control and data processing module can combine the robot arm's pose data with the insulator's axial coordinate system to spatially register the excitation and reception positions of each scanning point, thereby achieving accurate mapping of defect information onto the insulator's three-dimensional model and improving the accuracy of defect location and quantitative assessment.

[0087] Based on the above system structure, the robotic arm gripping and laser ultrasonic scanning system of the present invention can be implemented in the following steps when performing non-destructive testing on basin-type insulators:

[0088] Clamping and calibration stage: The pot-type insulator to be tested is placed between the three grippers 22. The clamping mechanism 2 is activated to make the grippers close synchronously in the radial direction until the flexible gasket 23 makes reliable contact with the outer edge of the insulator flange and reaches the predetermined clamping force. The self-locking mechanism 24 locks the gripper position. Subsequently, the posture of the robotic arm is adjusted by the axis calibration structure 25 and the vision system to make the geometric center axis of the insulator coincide with the axis of the clamp, and the upper flange plane parallel to the horizontal reference plane, thus completing the unification of the insulator coordinate system and the robotic arm end coordinate system.

[0089] Scanning path planning stage: In the control and data processing module 5, based on the insulator's outer diameter, basin height, and target detection area, the circumferential resolution (e.g., a step size of 1° or 2°) and the number of longitudinal scanning layers are set, automatically generating a three-dimensional scanning trajectory that links the insulator's rotation around the axis with the robot arm's pitch. During trajectory planning, the fixture axis is defined as the Z-axis, and the circumferential angle is θ, facilitating the mapping of defect imaging results back to the insulator's three-dimensional model.

[0090] Laser excitation and signal acquisition stage: Following the planned trajectory, the robotic arm 1 is driven to rotate the insulator around its axis at a set step distance to the first measuring point angle. Once the robotic arm 1 is in position and its posture is stable, the control unit sends an external trigger signal to the pulsed laser A1. The laser is focused through lens A2 onto the laser-induced acoustic enhancement medium A3, exciting ultrasonic waves on the surface of the insulator sample A4. Simultaneously, the data acquisition control module sends sampling commands to the high-speed data acquisition card to sample the vibration signal output by the laser Doppler vibration meter at high speed. This process is repeated at each circumferential angle until one or more scans are completed.

[0091] Signal preprocessing and feature extraction stage: The acquired time-domain laser ultrasound signal is input into the signal processing unit, where bandpass filtering, denoising, envelope extraction, and time-frequency analysis are performed sequentially. Features such as first wave arrival time, echo amplitude, and energy index are extracted in the time domain, and spectral peak value and bandwidth are extracted in the frequency domain. These features are then associated with and stored with the corresponding scanning angle and radial position to provide basic data for subsequent imaging and damage assessment.

[0092] Imaging and Defect Assessment Stage: The imaging and defect assessment unit spatially registers the excitation / receiving points at each scanning position in the insulator's axial coordinate system, and associates the feature values ​​extracted from the acquired signals with the scanning pose, mapping them onto the insulator's three-dimensional geometric model for subsequent defect localization and visualization. For a circumferential scan echo data acquired at each axial position, the imaging and defect assessment unit uses a synthetic aperture time-delay superposition imaging method for focused reconstruction to obtain a B-scan image of the corresponding cross-section. The B-scan image is used to characterize the echo reflection intensity distribution at different depths within the cross-section, thereby achieving layered imaging of internal and interface reflectors.

[0093] Furthermore, to obtain the overall distribution of defects on the insulator surface in the unfolded coordinate system, this invention generates a C-scan image based on multiple B-scan images. Specifically, the detection area is scanned layer by layer (or circle by circle) along the insulator axis. Circumferential scan data is repeatedly acquired at different axial positions, and multiple B-scan images are reconstructed accordingly. Subsequently, a depth range related to defect detection is selected in each B-scan image, and the grayscale information within this range is projected and converged to obtain the representative intensity distribution of that axial position at each circumferential position. The representative intensity distributions at different axial positions are then stitched together in axial order and normalized and mapped to grayscale, thus forming a C-scan image with "circumferential position - axial position" as the coordinate system. The C-scan image can intuitively reflect the distribution range and continuity of defects in the circumferential and axial unfolded planes, facilitating rapid location of abnormal areas.

[0094] Based on the aforementioned B-scan and / or C-scan images, the imaging and defect assessment unit identifies abnormally high / low reflection areas related to defects such as debonding, voids, and cracks. Combining the time delay and amplitude attenuation information of the defect echo, it estimates the depth and size of the defect and outputs a visualized detection result and text report containing the defect location, type, and severity. Simultaneously, the spatial coordinates and range of the defect can be further mapped onto the three-dimensional geometric model of the insulator to improve the accuracy of defect location and quantitative assessment.

[0095] Imaging and Defect Assessment Stage: The imaging and defect assessment unit maps the feature values ​​of each measuring point onto the three-dimensional geometric model of the insulator based on the insulator's axial coordinate system. It reconstructs the reflection image of the insulator's internal interface using B-scan or C-scan methods, identifying abnormally high / low reflection areas related to defects such as debonding, voids, and cracks. Combining the time delay and amplitude attenuation information of the defect echo, it estimates the depth and size of the defect, outputting a visual inspection result and text report containing the defect's location, type, and severity.

[0096] It is understood that the above implementation process is only a preferred embodiment of the present invention. In different application scenarios, parameters such as circumferential step angle, number of scanning layers, laser energy and data sampling rate can be adjusted according to the insulator specifications and detection accuracy requirements. As long as a robotic arm is used to achieve stable clamping and axial rotation of the basin insulator, combined with laser ultrasonic excitation and optical reception, and automated scanning and defect imaging are completed through control and data processing modules, the technical solution falls within the protection scope of the present invention.

Claims

1. A laser ultrasonic scanning system for testing basin-type insulators, characterized in that, The system includes a robotic arm, a gripping mechanism, a laser excitation module, a laser ultrasonic receiving module, and a control and data processing module. The gripping mechanism is located at the end of the robotic arm and is used to grip and position a basin-type insulator. The laser excitation module is used to non-contactly excite ultrasonic waves on the surface of the insulator. The laser ultrasonic receiving module is used to receive ultrasonic echo signals from the surface of the insulator. The control and data processing module is electrically connected to the robotic arm, the laser excitation module, and the laser ultrasonic receiving module, respectively. It is used to control the robotic arm to achieve three-dimensional posture adjustment and rotation of the basin-type insulator around its own axis, control the triggering and parameter setting of the laser excitation module, control the synchronous acquisition of the laser ultrasonic receiving module, and process and image the acquired ultrasonic signals to form a circumferential scanning path on the surface of the insulator.

2. The laser ultrasonic scanning system according to claim 1, characterized in that, The joint structure of the robotic arm includes: a base rotation joint for horizontal rotation of the robotic arm relative to the mounting base; a lower arm pitch joint, located between the base and the lower arm, for driving the lower arm to pitch around a horizontal axis; an upper arm pitch joint, located between the lower arm and the upper arm, for pitch adjustment of the upper arm's posture; and a wrist multi-degree-of-freedom rotation joint, located at the end of the upper arm, for fine-tuning of the end effector in roll, pitch, and yaw directions.

3. The laser ultrasonic scanning system according to claim 2, characterized in that, The robotic arm has rotational freedom along the clamp axis, enabling the insulator under test to rotate continuously or in steps around its own axis from 0 to 360°, and has pitch and yaw degrees of freedom to adapt to different installation postures and space-constrained working conditions.

4. The laser ultrasonic scanning system according to claim 1, characterized in that, The clamping mechanism includes: a clamping base rigidly connected to the wrist of the robotic arm; three grippers evenly distributed along the circumference, each gripper capable of opening and closing synchronously or independently in the radial direction; a flexible pad disposed on the inner surface of the grippers; a locking mechanism for self-locking the gripper position after clamping; and a clamp axis calibration structure for aligning the clamp axis with the geometric center axis of the basin insulator.

5. The laser ultrasonic scanning system according to claim 4, characterized in that, The grippers are used to clamp the metal flange or outer edge of the insulator, enabling adaptive clamping of insulators of different specifications; the flexible gasket is made of rubber or polyurethane elastic material.

6. The laser ultrasonic scanning system according to claim 1, characterized in that, The laser excitation module includes a pulsed laser and a laser-induced acoustic enhancement medium disposed in the optical path. The laser-induced acoustic enhancement medium is coated on a lens or intermediate carrier in the laser optical path.

7. The laser ultrasonic scanning system according to claim 6, characterized in that, The laser-induced acoustic enhancement medium is a two-dimensional layered titanium carbide material based on MXene, preferably an Mxene / PDMS composite enhancement medium loaded with gold nanoparticles.

8. The laser ultrasonic scanning system according to claim 1, characterized in that, The laser ultrasonic receiving module includes a laser Doppler vibrometer and a high-speed data acquisition card. The receiving spot of the receiving module is set near the excitation point or in an area with a predetermined distance from the excitation point. By adjusting the posture of the robotic arm, the receiving beam forms a predetermined angle with the normal of the insulator surface to optimize signal acquisition.

9. The laser ultrasonic scanning system according to claim 1, characterized in that, The control and data processing module includes: a motion control unit for controlling the robotic arm to achieve rotation and attitude adjustment of the insulator around the axis; a laser control unit for triggering and setting parameters of the pulsed laser; a signal processing unit for denoising, filtering, envelope extraction, and time-frequency analysis of the ultrasonic signal; and an imaging and defect detection unit for focusing and reconstructing the echo data using a circumferential synthetic aperture time-delay superposition imaging method to form an ultrasonic tomographic image of the insulator's interior and its interface, and to identify defects.

10. The laser ultrasonic scanning system according to any one of claims 1-9, characterized in that, The control and data processing module processes the echo signal and uses the synthetic aperture time-delay superposition imaging method to focus and reconstruct the circumferential scan data to obtain the B-scan image of the corresponding cross section. After acquiring multiple B-scan images at multiple axial positions, the module projects and converges the images by selecting the defect-related depth range and stitches them together axially to form a C-scan image with the circumferential position versus the axial position as the coordinates. This provides an intuitive representation of the defect distribution. Based on the B-scan and C-scan images, the module identifies the abnormal reflection areas of various defects such as debonding, voids, and cracks. Combined with echo characteristics, the module enables defect localization, quantitative assessment, and report output.

Images