A cylindrical inner wall surface defect automatic measuring device and identification evaluation method

Abstract

The application discloses a kind of cylindrical inner wall surface defect automatic measuring device and identification evaluation method, device includes measurement unit, support platform, motion platform, lengthening shaft and control system;Measurement unit includes one or more sets of laser profile sensor, is carried in the end of lengthening shaft, for measuring the topographic data of the inner wall surface of measured workpiece, measurement unit is connected with motion platform by lengthening shaft, support platform is V-shaped support platform, for placing measured workpiece;Motion platform includes X-axis linear motion platform, Z-axis linear motion platform and rotary shaft motion platform, measurement unit can be realized horizontal scanning measurement and rotary scanning measurement and the adjustment of measurement range by the movement of motion platform;Control system is used to carry out closed-loop feedback control to X-axis linear motion platform, Z-axis linear motion platform and rotary shaft motion platform.The application can be realized with high precision and high efficiency the automatic measurement, identification and evaluation of cylindrical inner wall surface defect.

Description

Technical Field

[0001] This invention belongs to the field of geometric precision measurement, specifically relating to an automatic measurement device and identification and evaluation method for defects on the inner wall surface of a cylindrical object. Background Technology

[0002] Large cylindrical parts, such as rocket launchers, are widely used in defense industries, aerospace, and other fields, and their inner walls are mostly made of black composite materials. Due to specific application requirements, large rocket launcher components are characterized by narrow openings on one or both sides, large inner diameters, and black inner walls, making three-dimensional measurement of their aperture and other dimensions, as well as inner surface defects, very difficult.

[0003] Currently, the inspection of deep hole dimensions and inner wall surface morphology can be mainly divided into two directions: contact measurement and non-contact measurement. For contact measurements, represented by inside micrometers and coordinate measuring machines, the measurement data is discrete, resulting in limited data volume and low measurement efficiency, and the measuring head cannot penetrate deeply into the cylinder. In terms of non-contact measurements, non-optical methods such as eddy current methods and ultrasonic methods have certain requirements on the material and thickness of the measured object, and cannot meet the measurement needs of the inner wall surface morphology of cylinders. Camera-based measurement methods are affected by the dim environment inside the cylinder, resulting in unclear measurement images, and cannot complete depth information measurement. Therefore, there is currently a lack of effective devices for measuring inner wall surface defects in large shells with narrow openings, typically represented by cylindrical parts. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic measurement device and identification and evaluation method for surface defects on the inner wall of a cylindrical structure, which can achieve automatic measurement, identification and evaluation of surface defects on the inner wall of a cylindrical structure with high precision and high efficiency.

[0005] To achieve the above objectives, one aspect of the present invention provides an automatic measuring device for surface defects on the inner wall of a cylindrical structure, comprising a measuring unit, a support platform, a motion platform, an extension shaft, and a control system;

[0006] The measuring unit includes one or more sets of laser profile sensors mounted on the end of the extended shaft, used to measure the topographic data of the inner wall surface of the workpiece being measured. The measuring unit is connected to the motion platform through the extended shaft. The support platform is a V-shaped support platform used to place the workpiece being measured.

[0007] The motion platform includes an X-axis linear motion platform, a Z-axis linear motion platform, and a rotary axis motion platform. The measurement unit can achieve horizontal scanning measurement through the horizontal movement of the X-axis linear motion platform, achieve rotary scanning measurement through the rotation of the rotary axis motion platform, and adjust the measurement range through the vertical movement of the Z-axis linear motion platform.

[0008] The control system is used for closed-loop feedback control of the X-axis linear motion platform, the Z-axis linear motion platform, and the rotary axis motion platform.

[0009] Preferably, the extended shaft has a hollow structure, and an extended shaft deflection monitoring system is provided on the central axis of the extended shaft. The extended shaft deflection monitoring system is used to collect the deformation of the extended shaft and feed it back to the Z-axis linear motion platform, thereby compensating for the error caused by the change in the deflection of the extended shaft in real time.

[0010] Preferably, the motion platform further includes a linear grating, a grating code disk, and a three-way photoelectric detection axial positioner. Two linear gratings are respectively installed on the X-axis linear motion platform and the Z-axis linear motion platform for measuring linear displacement. The grating code disk is installed on the rotary axis motion platform for measuring rotational angular position. The three-way photoelectric detection axial positioner is used to achieve alignment and zeroing of the X-axis, Z-axis, and rotary axis of the motion platform.

[0011] Preferably, the device further includes an auxiliary support structure for providing auxiliary support and protection for the extended shaft.

[0012] Another aspect of the present invention provides a method for identifying and evaluating surface defects on the inner wall of a cylindrical structure, comprising: measuring surface defects on the inner wall of the cylindrical structure using the aforementioned apparatus, and identifying and evaluating surface defects on the inner wall of the cylindrical structure based on the measurement data, including:

[0013] The measurement step involves using the measuring device to measure surface defects on the inner wall of the cylindrical shape and obtaining measurement data.

[0014] The measurement data preprocessing step uses collaborative filtering to remove spike-shaped point cloud noise from the measurement data;

[0015] The data stitching step involves using the motion distance and direction of the motion platform to perform coarse registration of the point cloud, and then using the ICP registration algorithm to perform fine registration of the point cloud to obtain complete measurement data of the inner wall surface.

[0016] The defect identification steps involve segmenting the point cloud data into super voxels based on the angle between the normal vectors and the spatial distance of the measured data; determining the angle between the line vector connecting the centers of adjacent super voxels and the normal vector, and the cross product of the normal vectors of adjacent super voxels, as the basis for concavity / convexity discrimination, and recording the super voxel adjacency graph; performing coarse segmentation based on Gaussian curvature and average curvature to obtain the point cloud of preliminary concavity / convex defects; generating multiple initial seed points with the centroid of each defect point cloud; and using a region growing algorithm to cluster regions with the same concavity / convexity to complete the identification, localization, and segmentation of defects.

[0017] The defect evaluation steps involve calculating the directed bounding box of the defect point cloud to obtain the length and width parameters of the defect, reconstructing the surface of the defect point cloud, and using the difference between the ideal surface point and the actual surface point after reconstruction as the depth value of the defect.

[0018] According to the above-described automatic measurement device and identification and evaluation method for cylindrical inner wall surface defects of the present invention, the automatic measurement, identification and evaluation of cylindrical inner wall surface defects can be achieved with high precision and high efficiency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0020] Figure 1 This is a schematic diagram of the structure of an automatic measurement device for surface defects on the inner wall of a cylindrical tube according to one embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Embodiments of the present invention provide an automatic measurement device for surface defects on the inner wall of a cylindrical structure. Figure 1 This is a schematic diagram of the structure of an automatic measurement device for surface defects on the inner wall of a cylindrical tube according to one embodiment of the present invention. Figure 1 As shown, the automatic measurement device for surface defects of cylindrical inner wall in this embodiment of the invention includes a measurement unit 2, a support platform 3, a motion platform, an extension shaft 7, an auxiliary support structure 8, and a control system 10.

[0023] The measuring unit 2 includes one or more sets of laser profile sensors mounted on the end of the extended shaft 7, used to measure the morphological data of the inner wall surface of the workpiece 1. The laser profile sensors are point, line, or surface laser profile sensors. The support platform 3 is a V-shaped support platform used to place the workpiece 1, ensuring accurate positioning of the large housing measurement position and stable and reliable measurement operation. The motion platform includes an X-axis linear motion platform 4, a Z-axis linear motion platform 6, and a rotary axis motion platform 5. The X-axis linear motion platform 4 is a horizontal motion platform, and the Z-axis linear motion platform 6 is a vertical motion platform. The auxiliary support structure 8 is used to provide auxiliary support and protection for the extended shaft. The control system 10 is used for closed-loop feedback control of the X-axis linear motion platform 4, the Z-axis linear motion platform 6, and the rotary axis motion platform 5. The control system 10 is, for example, a computer.

[0024] The measuring unit 2 is connected to the motion platform via the extended shaft 7. The measuring unit 2 can be spatially optimized by adding multiple sets of different types of point, line, or surface laser profile sensors to meet the measurement requirements of different diameter ranges. The Z-axis linear motion platform 6 drives the extended shaft 7 to move along the normal direction of the axis of the workpiece 1 being measured, thereby increasing the measurement range of the device.

[0025] The extended shaft 7 has a hollow structure. A deflection monitoring system, data cables, and power cables are installed along the central axis of the extended shaft 7. By routing all cables through the hollow center of the extended shaft 7, cable clutter and tangling during rotational measurements are prevented, while also saving space. The extended shaft 7 deflection monitoring system can collect the deformation of the extended shaft 7 and feed it back to the Z-axis linear motion platform 6, compensating for errors caused by changes in the extended shaft deflection in real time.

[0026] The measuring unit 2 can perform horizontal, vertical, and rotary movements via the motion platform. The X-axis linear motion platform 4, Z-axis linear motion platform 6, and rotary axis motion platform 5 form a closed-loop feedback motion platform. The motion platform also includes components such as linear gratings, grating encoders, and three-way photoelectric axial positioners 9, enabling precise motion positioning. The linear gratings are respectively installed on the X-axis linear motion platform 4 and the Z-axis linear motion platform 6 for accurately measuring linear displacement; the grating encoder is installed on the rotary axis motion platform 5 for accurately measuring rotational angular position; and the three-way photoelectric axial positioners 9 are installed near the three axis gratings for axial zeroing. Before each measurement, the X-axis, Z-axis, and rotary axis of the motion platform are aligned and zeroed using the three-way photoelectric axial positioners 9, thereby calibrating the initial position of the measuring unit 2 and unifying the measurement coordinate system.

[0027] The present invention also provides a method for identifying and evaluating surface defects on the inner wall of a cylindrical structure. This method utilizes the aforementioned measuring device to measure surface defects on the inner wall of the cylindrical structure, and identifies and evaluates these defects based on the measurement data. The method includes a measurement step, a measurement data preprocessing step, a data stitching step, a defect identification step, and a defect evaluation step.

[0028] In the measurement step, the measuring device is used to measure surface defects on the inner wall of the cylinder, obtaining measurement data. The measurement methods include horizontal scanning measurement, rotary scanning measurement, or a hybrid measurement. Specifically, vertical movement along the Z-axis allows the measuring unit to meet a suitable measurement range, while horizontal movement (X-axis) measurement completes a single horizontal scan within the cylinder. Because the cylinder has a large internal area, a single horizontal movement measurement cannot measure the entire surface morphology of the cylinder wall, and the cylindrical object is heavy and cannot be rotated, a hybrid measurement can be performed: first a horizontal scanning measurement followed by a rotary scanning measurement, or a horizontal scanning measurement can be performed simultaneously with a rotary scanning measurement.

[0029] In the measurement data preprocessing step, the measurement data of the inner wall surface is read and stored in real time, and the spike-shaped point cloud noise in the measurement data is removed by collaborative filtering.

[0030] In the data stitching step, measurement data acquired through multiple scans are stitched together. Coarse point cloud registration is performed by recording the motion distance and direction of the motion platform, followed by fine point cloud registration using a fast and robust ICP (Iterative ClosestPoint) registration algorithm. This completes the registration of multi-view point clouds and yields complete measurement data of the inner wall surface.

[0031] In the defect identification step, the point cloud data is first segmented into super voxels based on the angle between the normal vectors and the spatial distance of the measured data. The angle between the line vector connecting the centers of adjacent super voxels and the normal vector, and the cross product of the normal vectors of adjacent super voxels are determined as the basis for concavity / convexity discrimination, and the super voxel adjacency graph is recorded. The point cloud is coarsely segmented based on Gaussian curvature and mean curvature to obtain the point cloud of preliminary concavity / convex defects. Multiple initial seed points are generated with the centroid of each defect point cloud. The region growing algorithm is used to cluster regions with the same concavity / convexity to complete the identification, location and segmentation of defects such as slits, cracks, grooves, steps, and blind holes. Different defect types are displayed with color differences to help determine the defect location and size, and the defect data is stored in sequence.

[0032] In the defect evaluation step, the geometric parameters such as the length, width and depth of the defect are quantified. The length and width of the defect are obtained by segmenting the defect point cloud. The directed bounding box of the point cloud is calculated to obtain the length and width parameters of the defect. Then, the defect is quantified by surface reconstruction. The depth value of the defect is the difference between the ideal surface point and the actual surface point after defect reconstruction.

[0033] In summary, the automatic measurement device and identification and evaluation method for cylindrical inner wall surface defects of the present invention utilizes a line laser profile sensor to measure in the horizontal, vertical and rotational directions, and obtains measurement data of the inner wall surface of a large shell through real-time closed-loop feedback compensation. Then, the measurement data is preprocessed, stitched together, and segmented and evaluated for defect identification, thereby completing the automatic identification and evaluation of defects on the inner wall surface of the workpiece.

[0034] The automatic measurement device and identification and evaluation method for surface defects on the inner wall of a cylindrical structure according to the embodiments of the present invention have the following beneficial effects:

[0035] 1. This invention addresses the problem of narrow openings in cylindrical components by utilizing a two-dimensional movement and rotation mechanism. Leveraging the precision and spatial volume advantages of a line laser profile sensor, it achieves high-precision and high-efficiency scanning measurement, solving the problems of difficulty in deep measurement of the black surface of the inner wall of narrow-opening cylindrical components, difficulty in morphological measurement due to light absorption by black surfaces, and difficulty in locating and quantifying the position of surface defects.

[0036] 2. This invention addresses the problem that it is difficult to identify and locate defects in measured point clouds, and that the performance of region growing algorithms depends on seed points. First, the measured point cloud is initially segmented based on Gaussian curvature and average curvature. Then, the centroids of the obtained concave and convex regions are used as seed points for region growing. This allows the defect segmentation algorithm to maintain good boundary properties and region connectivity, and reduces the difficulty of parameter adjustment.

[0037] 3. Compared with the prior art, the non-contact measurement method based on line laser measurement of the present invention has high accuracy, high efficiency, and is less affected by the environment, making it easy to process and evaluate data.

[0038] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for identifying and evaluating surface defects on the inner wall of a cylindrical object, characterized in that, An automatic measuring device for surface defects of a cylindrical inner wall is used to measure surface defects of a cylindrical inner wall, and the surface defects of the cylindrical inner wall are identified and evaluated based on the measurement data. The cylindrical inner wall has a narrow opening and a black surface. The automatic measuring device for surface defects of a cylindrical inner wall includes a measuring unit, a support platform, a motion platform, an extension shaft, and a control system. The measuring unit includes one or more sets of laser profile sensors mounted on the end of the extended shaft, used to measure the topographic data of the inner wall surface of the workpiece being measured. The measuring unit is connected to the motion platform through the extended shaft. The support platform is a V-shaped support platform used to place the workpiece being measured. The motion platform includes an X-axis linear motion platform, a Z-axis linear motion platform, and a rotary axis motion platform. The measurement unit can achieve horizontal scanning measurement through the horizontal movement of the X-axis linear motion platform, achieve rotary scanning measurement through the rotation of the rotary axis motion platform, and adjust the measurement range through the vertical movement of the Z-axis linear motion platform. The control system is used to perform closed-loop feedback control of the X-axis linear motion platform, the Z-axis linear motion platform, and the rotary axis motion platform. The extended shaft has a hollow structure, and a deflection monitoring system is installed on the central axis of the extended shaft. This system collects the deformation of the extended shaft and feeds it back to the [other relevant entity / organization]. Z A linear motion platform for the shaft, thereby compensating for errors caused by changes in the deflection of the extended shaft in real time; The method includes: The measurement step involves using the measuring device to measure surface defects on the inner wall of the cylindrical shape and obtaining measurement data. The measurement data preprocessing step uses collaborative filtering to remove spike-shaped point cloud noise from the measurement data; The data stitching step involves using the motion distance and direction of the motion platform to perform coarse registration of the point cloud, and then using the ICP registration algorithm to perform fine registration of the point cloud to obtain complete measurement data of the inner wall surface. The defect identification steps involve segmenting the point cloud data into super voxels based on the angle between the normal vectors and the spatial distance of the measured data; determining the angle between the line vector connecting the centers of adjacent super voxels and the normal vector, and the cross product of the normal vectors of adjacent super voxels, as the basis for concavity / convexity discrimination, and recording the super voxel adjacency graph; performing coarse segmentation based on Gaussian curvature and average curvature to obtain the point cloud of preliminary concavity / convex defects; generating multiple initial seed points with the centroid of each defect point cloud; and using a region growing algorithm to cluster regions with the same concavity / convexity to complete the identification, localization, and segmentation of defects. The defect evaluation steps involve calculating the directed bounding box of the defect point cloud to obtain the length and width parameters of the defect, reconstructing the surface of the defect point cloud, and using the difference between the ideal surface point and the actual surface point after reconstruction as the depth value of the defect.

2. The method according to claim 1, characterized in that, The motion platform also includes a linear grating, a grating code disk, and a three-way photoelectric detection axial positioner. Two linear gratings are configured, each located in... X Axis linear motion platform and Z On the linear motion platform, linear displacement is measured; on the rotary motion platform, an optical encoder is used to measure rotational angular position; and a three-way photoelectric detection axial positioner is used to align and zero the X-axis, Z-axis, and rotary axis of the motion platform.

3. The method according to claim 1 or 2, characterized in that, It also includes an auxiliary support structure, which is used to provide auxiliary support and protection for the extended shaft.

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