An ultrasonic testing device for carbon fiber reinforced composite skin

Abstract

The present invention belongs to the field of non-destructive testing technology, and specifically discloses an ultrasonic testing device for carbon fiber reinforced composite skin, which is used for ultrasonic data collection and defect detection and identification of CFRP skin. The testing device includes a testing platform, a three-dimensional motion mechanism, a parallel robot, an ultrasonic transducer, an infrared scanner and a CFRP skin fixture. The device of the present invention obtains geometric data by infrared scanning, and constructs a CFRP skin surface model after processing the data points. On the basis of path planning, the ultrasonic transducer clamped at the end of the parallel robot moves with the surface shape of the CFRP skin to be detected, collects ultrasonic signals, and realizes ultrasonic detection of surface and internal defects of the CFRP skin by combining ultrasonic signal processing with machine learning. The device of the present invention can realize non-destructive testing of CFRP skin, thereby meeting the needs of non-destructive testing of carbon fiber reinforced composite materials in the fields of aerospace, automobile industry, medical equipment, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing, and in particular relates to an ultrasonic testing device for a carbon fiber reinforced composite material skin. Background Art

[0002] Carbon fiber reinforced composites (CFRP) have higher specific strength and specific rigidity than other materials. They are currently widely used in launch vehicles, advanced ships, medical equipment and other fields. In recent years, the proportion of aircraft skins made of CFRP has continued to increase. However, defective CFRP skins will fail quickly under the influence of impact during service. Therefore, it is necessary to monitor the integrity of CFRP skins through non-destructive testing technology so that defects can be detected in time during the manufacturing process and the aircraft skins can be replaced.

[0003] However, traditional non-destructive testing methods, such as eddy current and magnetic particle testing, are not suitable for the inspection of CFRP materials because these methods rely on the electromagnetic properties of metal materials, while CFRP is a non-metallic composite material.

[0004] To this end, the present invention proposes an ultrasonic testing experimental device for carbon fiber reinforced composite material skin, which uses ultrasonic waves to penetrate the medium to detect defects inside the material to solve the problem of CFRP non-destructive testing. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrasonic testing device for carbon fiber reinforced composite material skin, so as to solve the problem that there is a lack of efficient and reliable non-destructive testing technology for carbon fiber reinforced composite material skin in the prior art.

[0006] To achieve the above object, the present invention provides the following solution: an ultrasonic testing device for carbon fiber reinforced composite material skin, comprising:

[0007] A detection platform, on which a fixture fixing seat is fixedly connected;

[0008] A three-dimensional motion mechanism, wherein the three-dimensional motion mechanism is fixedly connected above the detection platform;

[0009] A parallel robot, the parallel robot is connected to the three-dimensional motion mechanism; the parallel robot comprises an upper platform detachably connected to the three-dimensional motion mechanism, and a lower platform located below the upper platform, and a plurality of kinematic pairs are movably connected between the upper platform and the lower platform;

[0010] An ultrasonic transducer, the ultrasonic transducer is fixedly connected to the bottom of the lower platform;

[0011] A CFRP skin fixture, used for positioning the tested skin, wherein the CFRP skin fixture is detachably mounted on the fixture fixing seat;

[0012] An infrared scanner is located at one side of the detection platform and faces the detected skin.

[0013] Optionally, the kinematic pair includes a first ball joint, a moving pair, an electric cylinder, a control arm, and a second ball joint connected in sequence from top to bottom, the first ball joint being movably connected to the bottom of the upper platform, and the second ball joint being movably connected to the lower platform.

[0014] Optionally, six of the kinematic pairs are connected between the upper platform and the lower platform.

[0015] Optionally, the upper platform and the lower platform are both unequally symmetrical hexagons, the outer dimensions of the lower platform are smaller than those of the upper platform, and the upper platform and the lower platform are oriented in opposite directions.

[0016] Optionally, the six kinematic pairs are respectively connected to six corners of the upper platform and the lower platform.

[0017] Optionally, the CFRP skin fixture includes a fixture body, a flexible pin elastically connected to the fixture body, and a locking mechanism located on one side of the fixture body, wherein the bottom end of the flexible pin is connected to the fixture body through an elastic element, and the top end extends out of the fixture body to contact the skin to be measured.

[0018] Optionally, the infrared scanner is located on one side of the detection platform, and includes a first camera, a second camera and a blue light source facing the tested skin, and the first camera and the second camera are symmetrically arranged on both sides of the blue light source.

[0019] Optionally, a force sensor is also installed below the parallel robot, and the force sensor is in contact with the ultrasonic transducer.

[0020] Optionally, the three-dimensional motion mechanism includes two Y-axis motion mechanisms fixedly connected above the detection platform, an X-axis motion mechanism slidably connected to the two Y-axis motion mechanisms along the Y direction, and a Z-axis motion mechanism slidably connected to the X-axis motion mechanism along the X direction, and a Z-axis moving component is provided on the Z-axis motion mechanism that slides along the Z axis, and the parallel robot is installed at the bottom of the Z-axis moving component.

[0021] Optionally, the ultrasonic testing device for carbon fiber reinforced composite material skin also includes a notebook computer for displaying and processing test data.

[0022] The present invention discloses the following technical effects:

[0023] The present invention discloses an ultrasonic testing device for carbon fiber reinforced composite material skin, which acquires geometric data by infrared scanning, constructs a CFRP skin surface model after processing the data points, thereby realizing non-destructive testing of the CFRP skin, thereby meeting the needs of non-destructive testing of carbon fiber reinforced composite materials used in the fields of aerospace, automobile industry, medical equipment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a front view of an ultrasonic testing device for carbon fiber reinforced composite material skin according to an embodiment of the present invention;

[0026] Figure 2 It is a right side view of the test device according to the embodiment of the present invention;

[0027] Figure 3 A top view of a test device according to an embodiment of the present invention;

[0028] Figure 4 It is an axonometric diagram of a test device according to an embodiment of the present invention;

[0029] Figure 5 It is a schematic diagram of the structure of the detection platform part in the test device of the embodiment of the present invention;

[0030] Figure 6 Schematic diagram of the X-axis motion mechanism in the test device of the embodiment of the present invention;

[0031] Figure 7 Schematic diagram of the Y-axis motion mechanism in the test device of the embodiment of the present invention;

[0032] Figure 8 Schematic diagram of the Z-axis motion mechanism in the test device of the embodiment of the present invention;

[0033] Fig. 9 It is a front view of a six-degree-of-freedom parallel robot in a test device according to an embodiment of the present invention;

[0034] Fig.10 It is a right side view of a six-degree-of-freedom parallel robot in a test device according to an embodiment of the present invention;

[0035] Fig.11 A top view of a six-degree-of-freedom parallel robot in a test device according to an embodiment of the present invention;

[0036] Fig.12 is an axonometric diagram of a six-degree-of-freedom parallel robot in a test device according to an embodiment of the present invention;

[0037] Fig.13 It is a schematic diagram of the structure of the kinematic pair in the test device of the embodiment of the present invention;

[0038] Fig.14 This is a schematic diagram of the structure of an infrared scanner in a test device according to an embodiment of the present invention;

[0039] Fig.15 It is a schematic diagram of the structure of the CFRP skin fixture in the test device of an embodiment of the present invention.

[0040] Among them, 1. detection platform; 2. Y-axis motion mechanism; 20. first motion motor; 3. Y-moving slider; 4. X-axis motion mechanism; 40. second motion motor; 5. X-moving slide; 6. Z-axis motion mechanism; 60. third motion motor; 7. Z-moving component; 8. parallel robot; 81. upper platform; 82. lower platform; 83. kinematic pair; 831. first ball joint; 832. moving pair; 833. electric cylinder; 834. control arm; 835. second ball joint; 9. ultrasonic transducer; 10. second platform; 11. infrared scanner; 111. scanner body; 112. first camera; 113. second camera; 114. blue light source; 12. CFRP skin fixture; 121. fixture body; 122. flexible pin; 123. locking mechanism; 13. fixture fixing seat; 14. notebook computer; 15. tripod. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Reference Figures 1 to 15 As shown, the present invention provides an ultrasonic detection test device for carbon fiber reinforced composite material skin, which is used for ultrasonic data collection and defect detection and identification of CFRP skin. The test device includes a detection platform 1, a three-dimensional motion mechanism, a parallel robot 8, an ultrasonic transducer 9, an infrared scanner 11 and a CFRP skin fixture 12.

[0044] Specifically, the detection platform 1 is a box structure, and the interior can be used to install power and electrical components. Its top surface is a horizontal bearing surface, and two Y-axis motion mechanisms 2 are fixedly connected on the left and right sides above the bearing surface, and the two Y-axis motion mechanisms 2 are spaced apart along the X direction. The two Y-axis motion mechanisms 2 are slidably connected with Y-direction moving sliders 3, and the Y-direction moving sliders 3 are driven to reciprocate along the Y direction by the first motion motor 20. An X-axis motion mechanism 4 is fixedly connected to the two Y-direction moving sliders 3, and an X-direction moving slide 5 is slidably connected to the X-axis motion mechanism 4, and the X-direction moving slide 5 is driven to reciprocate along the X direction by the second motion motor 40. A Z-axis motion mechanism 6 is fixedly connected to the X-direction moving slide 5, and a Z-direction moving component 7 is slidably connected to one side of the Z-axis motion mechanism 6. The Z-direction moving component 7 reciprocates up and down along the Z direction under the drive of the third motion motor 60.

[0045] The Y-axis motion mechanism 2, the X-axis motion mechanism 4 and the Z-axis motion mechanism 6 constitute a three-dimensional motion mechanism. The three-dimensional motion mechanism can realize reciprocating movement in the X-axis, Y-axis and Z-axis directions. A mounting hole is designed on the Z-axis moving component to fix the parallel robot 8.

[0046] The three-dimensional motion mechanism includes respective guiding mechanisms, transmission mechanisms and driving mechanisms in the three directions of X-axis, Y-axis and Z-axis; the bottom surface of the Y-axis motion mechanism 2 is fixed on the detection platform 1, the bottom surface of the X-axis motion mechanism 4 is fixed on two Y-direction moving slide blocks 3 in the Y-axis direction, and the Z-axis motion mechanism 6 is fixed on the X-direction moving slide seat 5. The X-direction moving slide seat 5 is a T-shaped steel plate, one side of which slides on the X-axis motion mechanism 4, and the other side is perpendicular to the bearing surface, and is used to install the Z-axis motion mechanism 6.

[0047] Further optimization scheme, in the above structure, the transmission mechanism can be a ball screw, and the ball screw includes components such as a screw, a nut, a steel ball, a pre-compression plate, a reverser and a dust collector. The control system of the mechanism movement is composed of a motion controller, a drive amplifier, an actuator, a feedback sensor and mechanical components. Each direction is controlled by a motor (a first motion motor 20, a second motion motor 40, and a third motion motor 60) to control the movement of the mechanism, and the control signal is amplified by the drive circuit. In addition, peripheral devices including a power module, a display interface, a serial port connected to a computer, and an output module are added. Through the serial port, the PC as the upper computer communicates with the PC, and the compiled program is downloaded to the memory of the single-chip microcomputer as the lower computer. Then, the entire system is in working state through an external power supply, and the execution data is entered. The single-chip microcomputer outputs a control signal after calculation, and then the electric signal is amplified by the drive circuit to make the motor run.

[0048] To further optimize the solution, in the ball screw system, the ball is installed in the middle of the spiral groove of the screw nut, and the ball is used as the middle transmission mechanism to form a ball screw pair. The ball screw includes components such as screw, nut, steel ball, preload plate, reverser and dust collector. The coupling is used to connect the ball screw and reducer, which plays a role of buffering and shock absorption when the ball screw rotates rapidly, improves the stability of the three-dimensional motion platform, and better guarantees work efficiency.

[0049] A fixture fixing seat 13 is also fixed to the bearing surface of the detection platform 1, and a plurality of mounting holes are opened on the fixture fixing seat 13 for installing the CFRP skin fixture 12. The CFRP skin fixture 12 adopts a flexible positioning fixture, including a fixture body 121, a flexible pin 122 elastically connected to the fixture body 121 through an elastic element, and a locking mechanism 123 located on one side of the fixture body 121. The CFRP skin fixture 12 can adapt to workpieces with complex shapes or irregular sizes, and has a flexible positioning function. It contains elastic elements inside, which can adapt well to different shapes and sizes of workpieces and has appropriate fixing force. The positioning method is multi-point positioning, and fixing force is applied at multiple positions of the workpiece to ensure the stability of the position and posture of the workpiece in the fixture, thereby providing a better positioning effect. According to the shape and size of different workpieces, the position of the fixture can be adjusted to adapt to a variety of different workpieces, and it has strong adaptability. The fixture body 121 is provided with a plurality of flexible pins 122 that can be extended and locked, and can well adapt to the curved surface of the CFRP skin. When the flexible pins 122 are locked, there is no axial or radial displacement of the contact points between the pins and the parts.

[0050] In this embodiment, two CFRP skin clamps 12 are installed on the clamp fixing seat 13 .

[0051] The Z-moving component 7 is an L-shaped steel plate, the vertical surface of which slides on the Z-axis motion mechanism 6 , and a plurality of mounting holes are opened on the horizontal surface. The parallel robot 8 is fixedly mounted on the bottom of the water surface of the Z-moving component 7 .

[0052] Since ultrasonic propagation has very strong directionality, in order to ensure the accuracy of the scanning test results, during the automatic detection process, the position of the ultrasonic transducer 9 must always maintain good consistency with the normal direction of the skin surface being tested. Therefore, the parallel robot 8 in this embodiment adopts a parallel robot 8 with six degrees of freedom. The parallel robot 8 includes an upper platform 81 and a lower platform 82 spaced apart from each other. The upper platform 81 and the lower platform 82 are connected by six kinematic pairs 83 with the same structure and adjustable length. The upper platform 81 and the lower platform 82 are both unequally symmetrical hexagons. The upper platform 81 can perform six-degree-of-freedom motion in space, and the lower platform 82 is fixed. The six middle kinematic pairs 83 with the same structure and length have the effect of swinging within a certain angle. The structure of the parallel robot 8 is as follows: Figures 9 to 12 shown.

[0053] like Fig.13 As shown, the kinematic pair 83 includes an electric cylinder 833, a mobile pair 832, a control arm 834, a first ball joint 831 and a second ball joint 835. The first ball joint 831 is movably connected to the upper platform 81, and the second ball joint 835 is movably connected to the lower platform 82. One end of the control arm 834 is connected to the second ball joint 835, and the other end is connected to the electric cylinder 833. One end of the mobile pair 832 is connected to the first ball joint 831, and the other end is connected to the electric cylinder 833. The control arm 834 swings at a certain angle under the driving action of the motor. The other end of the control arm 834 is connected to the lower platform 82 through the second ball joint 835 chain. The lower platform 82 is connected to the ultrasonic transducer 9. With the cooperation of the kinematic pair 83, the probe is moved in three coordinate directions, and the trajectory of the ultrasonic transducer 9 on the surface of the measured skin is formed according to the principle of parallel kinematics.

[0054] The calculation formula for the 8 degrees of freedom of the parallel robot is:

[0055]

[0056] In the formula, M represents the number of degrees of freedom of the mechanism, n represents the number of unconstrained components of the mechanism in space, g represents the number of kinematic pairs in the mechanism, and f i Represents the number of degrees of freedom of the i-th kinematic pair 83. The upper platform 81 and the lower platform 82 are connected by 6 branches, each of which has two ball joints at both ends and a moving pair 832 in the middle. The displacement of the control arm 834 is used as the input variable to control the spatial displacement and posture of the moving platform. The electric cylinder 833 pushes the moving pair 832 to move relative to each other, changing the length of each rod, so that the position and posture of the upper platform 81 in space change. The moving coordinate system p-X2Y2Z2 is established on the upper platform 81 and moves with the upper platform 81. The origin P is located at the geometric center of the upper platform 81; the coordinate system O-X1Y1Z1 is fixed on the lower platform 82, and the origin O is located at the geometric center of the lower platform 82, and its Z axis is perpendicular to the plane of the lower platform 82. Given the short side angle α2 of the upper platform 81, the short side angle α1 of the lower platform 82, the circumscribed circle radius r of the upper platform 81, and the circumscribed circle radius R of the lower platform 82, the coordinates p of each hinge point of the upper platform 81 in the moving coordinate system can be calculated. i (x i ,y i ,z i ) and the coordinates b of the hinge points of the lower platform 82 in the static coordinate system i (x i ,y i ,z i). If the position and posture of the upper platform 81 in space are given, the length of each rod, that is, the displacement of each moving pair 832, is calculated, which is the inverse solution of the position.

[0057] In this embodiment, a second platform 10 is also included, and the second platform 10 is located on one side of the detection platform 1. A notebook computer 14 is placed on the second platform 10 for displaying the detection data. In this embodiment, the grating projection and reflected light of the detected skin are captured to obtain the three-dimensional data of the surface of the detected skin, and then the collected data coordinates are input into the notebook computer 14 for analysis and processing.

[0058] In this embodiment, an infrared scanner 11 is also included and is placed on one side of the detection platform 1 via a tripod 15. The infrared scanner 11 includes a scanner body 111. The side of the scanner body 111 facing the detection platform 1 has two inclined left and right cameras and a light source in the middle, specifically a first camera 112, a second camera 113 and a blue light source 114.

[0059] The working principle of the infrared scanner 11 is: according to the principle of three-dimensional scanning, an accurate stripe pattern is projected onto the surface of the object through a light source system. The scanner uses thin strips of blue light for image acquisition, which can effectively filter out the interference of ambient light, and this energy-rich light source is also conducive to reducing the measurement time. The measuring system monitors itself, and the measuring head makes corresponding compensation according to the changes in environmental conditions during the recognition work. When scanning the CFRP skin, it is necessary to manually set the positioning mark, obtain its spatial position by scanning the positioning mark on the skin, and then collect the grating projected onto the CFRP surface through the camera. During the acquisition process, the software will automatically track the positioning mark to complete the acquisition of point cloud data.

[0060] The collected data has distortion points, which need to be processed. The least square method is used to obtain a high-order fitting curve through the first and last data points of the CFRP skin. The point is judged to be a distortion point based on whether the distance from each data point to the curve is greater than the set tolerance, so as to retain or eliminate the point.

[0061] According to the acquired data points, the curve of the CFRP skin is constructed in the 3D software. In the process of constructing the curve, available points are selected according to the shape and characteristics of the CFRP skin to make the curve as simple as possible, meet the principle of smooth continuity, and no sharp corners, intersections and overlaps. When the data is blank, it will cause gaps in the surface. Select the extension method to extend the curve through the area that needs to be interpolated, and then discretize the curve to form a point series to supplement the feature boundary.

[0062] Construct a linear triangular mesh of patches interpolated at the sampling points. Calculate curvature information and minimize the curvature derivative between the original surface and the reconstructed mesh surface by changing the local topology of the triangular mesh. Compare the directional curvature of each mesh edge and the adjacent vertices in the same direction. Based on the curvature information, the mesh edges at or near the boundary are identified as boundaries, and the multi-domain data is divided into disconnected subgroups.

[0063] The curve is established by interpolation, an allowable error value is specified, and the number of curve control points is set. Based on all the measured data points, a curve is obtained by the least square method, and the distance from the measured point to the curve is calculated. If the maximum distance is greater than the set error value, the number of control points is increased and the curve is refitted until the error meets the condition. The curve editing function of the software is used to modify the CFRP skin curve, and the CFRP skin surface model is reconstructed through the surface modeling method.

[0064] The key to ultrasonic scanning inspection path planning for the CFRP skin under test is to generate a continuous trajectory on the surface. The method adopted is to use a series of planes parallel to the XOY plane of the workpiece coordinate system to intercept the surface of the CFRP skin under test, obtain a series of cross-section lines, and then sort, remove redundancy and connect these cross-section lines to obtain the inspection trajectory. The intersection of the cutting plane and the combined surface is decomposed into the intersection of the cutting plane and each surface block, so as to obtain each curve segment of the CFRP skin. All the edge lines of the CFRP skin surface block are parsed, and the curve segments are intercepted with the edge lines, and the parts outside the surface are cut off to remove redundancy. After obtaining all the curve segments of the CFRP skin, according to the requirements of scanning accuracy, the curve segments of the CFRP skin are discretized into points according to the maximum chord height error principle and the maximum step length principle. The complete information of the points is saved with a structure. Finally, the discrete points are arranged in order and fitted into the inspection trajectory line of the CFRP skin.

[0065] To further optimize the solution, a force sensor is installed under the parallel robot 8. The force sensor is installed under the parallel robot 8 and connected to the ultrasonic transducer 9. The contact force between the ultrasonic transducer 9 and the skin sample can be measured through the force sensor. The force generated by the contact between the skin and the ultrasonic transducer 9 during the detection is set as a target value. When the measured contact force is significantly smaller or larger than the ideal contact force of the corresponding object as required, the force sensor will feed back the contact force to the parallel robot 8, and the parallel robot 8 will adjust the electric cylinder 833 through the motor control according to the difference between the actual force and the ideal force.

[0066] The detection test process and principle of the embodiment of the present invention are as follows:

[0067] The geometric data is acquired by infrared scanning, and imported into the notebook computer 14 for analysis and processing. The data processing flow can be divided into acquisition of point cloud data, preprocessing of point cloud data, and construction of the model. After processing the data points, the CFRP skin surface model is constructed.

[0068] After the point cloud data is preprocessed, the 3D model is constructed. After generating continuous trajectories on the surface, a series of planes parallel to the XOY plane of the workpiece coordinate system are used to intercept the surface of the measured CFRP skin to obtain a series of cross-sectional lines, which are then sorted, de-redundanted, and connected. After obtaining all the curve segments of the CFRP skin, each curve segment is discretized into points. After saving the complete information of the points, the discrete points are arranged in order and fitted into the detection trajectory line of the CFRP skin.

[0069] To ensure good signal transmission, a coupling agent needs to be applied between the transducer and the CFRP skin to reduce signal loss. The three-dimensional motion platform moves along the detection trajectory. In order to ensure the quality of detection, the scanning direction is set along the direction with small curvature change, so that the scanning head swings with a small amplitude and the scanning is smooth. When scanning the boundary, it needs to extend an additional distance outward. The spacing of the trajectory lines must meet the requirements of economy and coverage. The transducer of the ultrasonic testing experimental device generates a transmitting pulse, which is transmitted to the ultrasonic probe after passing through the wire, exciting the probe to generate ultrasonic vibration, and the ultrasonic wave is emitted into the tested skin. When the ultrasonic wave inside the tested skin reaches the bottom surface of the tested skin, a reflection phenomenon occurs. The reflected wave carrying the internal information of the tested workpiece is received by the receiving device and converted into a voltage signal after being converted by the conversion circuit. The voltage signal after signal processing is sent to the oscilloscope for real-time display and storage.

[0070] The original signal is processed by framing to obtain the time domain features of each frame signal, such as amplitude, arrival time, mean, standard deviation, variance, short-time energy and autocorrelation coefficient. Then, the main frequency and amplitude of each frame signal, the frequency domain features such as the spectrum curve area are extracted by fast Fourier transform. Finally, wavelet packet analysis is carried out to reflect the time and frequency domain features such as the frequency and energy proportion of each frame signal. The feature selection method is used to screen out important, representative and classification-friendly features, and the classification accuracy is used to evaluate the effectiveness of the feature subset.

[0071] The support vector machine with radial basis function as kernel function is used as the classification algorithm, and the swarm intelligence optimization algorithm is used as the feature search algorithm to construct the best feature subset. When optimizing feature selection, each individual represents a solution, and its position information X iAs the design variable of the optimization problem, it represents the selection of features. The position X of the population is randomly initialized, and the conversion function can be used to compare with the threshold T for binary assignment, that is, if it is greater than T, the feature is used, otherwise it is not used. During the algorithm iteration process, the fitness function is used to evaluate the quality of each solution, and the fitness function is used to determine whether the position of the individual needs to be updated. When the classification accuracy in the classification result is high and the number of selected feature subsets is small, it means that the classification effect is better. According to the classification accuracy obtained by the classifier and the number of selected feature subsets for feature selection.

[0072] After obtaining the best feature subset, the classification model is trained again, and the performance evaluation index is used to evaluate the performance of the classification model. The number of positive samples in the test sample judged as positive samples by the classifier is recorded as TP, and the number of samples judged as negative samples is recorded as FN; the number of negative samples judged as negative samples by the classifier is recorded as TN, and the number of samples judged as positive samples is recorded as FP. Performance evaluation indicators include accuracy, precision, recall, and F value. Accuracy P is used as the main performance evaluation indicator to measure the overall classification accuracy of the model, which is defined as In the case of positive class prediction, accuracy Acc is used to evaluate the correctness of the classification model and is defined as Recall R is an indicator used to evaluate the model's ability to detect all positive examples. The F-measure is the harmonic mean of precision and recall, which is used to combine the precision and recall of the model and is defined as

[0073] The details not described in detail in the present invention are all conventional technical means known to those skilled in the art.

[0074] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0075] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An ultrasonic testing device for carbon fiber reinforced composite material skin, characterized in that: include: A detection platform (1), wherein a fixture fixing seat (13) is fixedly connected to the detection platform (1); A three-dimensional motion mechanism, the three-dimensional motion mechanism being fixedly connected above the detection platform (1); A parallel robot (8), wherein the parallel robot (8) is connected to the three-dimensional motion mechanism; the parallel robot (8) comprises an upper platform (81) detachably connected to the three-dimensional motion mechanism, and a lower platform (82) located below the upper platform (81); six kinematic pairs (83) are movably connected between the upper platform (81) and the lower platform (82); the kinematic pairs (83) comprise a first ball joint (831), a moving pair (832), an electric cylinder (833), a control arm (834), and a second ball joint (835) which are connected in sequence from top to bottom; the first ball joint (831) is movably connected to the bottom of the upper platform (81), and the second ball joint (835) is movably connected to the lower platform (82); An ultrasonic transducer (9), the ultrasonic transducer (9) being fixedly connected to the bottom of the lower platform (82); A CFRP skin fixture (12) is used for positioning the skin to be tested, and the CFRP skin fixture (12) is detachably mounted on the fixture fixing seat (13); An infrared scanner (11), wherein the infrared scanner (11) is located on one side of the detection platform (1) and faces the detected skin.

2. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: The upper platform (81) and the lower platform (82) are both unequally symmetrical hexagons, the outer dimensions of the lower platform (82) are smaller than those of the upper platform (81), and the upper platform (81) and the lower platform (82) are oriented in opposite directions.

3. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 2, characterized in that: The six kinematic pairs (83) are respectively connected to six corners of the upper platform (81) and the lower platform (82).

4. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: The CFRP skin fixture (12) comprises a fixture body (121), a flexible pin (122) elastically connected to the fixture body (121), and a locking mechanism (123) located on one side of the fixture body (121); the bottom end of the flexible pin (122) is connected to the fixture body (121) through an elastic element, and the top end extends out of the fixture body (121) to contact the measured skin.

5. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: The infrared scanner (11) is located on one side of the detection platform (1), and comprises a first camera (112), a second camera (113) and a blue light source (114) facing the skin to be detected, wherein the first camera (112) and the second camera (113) are symmetrically arranged on both sides of the blue light source (114).

6. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: A force sensor is also installed below the parallel robot (8), and the force sensor is in contact with the ultrasonic transducer (9).

7. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: The three-dimensional motion mechanism comprises two Y-axis motion mechanisms (2) fixedly connected above the detection platform (1), an X-axis motion mechanism (4) slidably connected above the two Y-axis motion mechanisms (2) along the Y direction, and a Z-axis motion mechanism (6) slidably connected to the X-axis motion mechanism (4) along the X direction, wherein a Z-axis moving component (7) is provided on the Z-axis motion mechanism (6) and slides along the Z axis, and the parallel robot (8) is installed at the bottom of the Z-axis moving component (7).

8. The ultrasonic testing device for carbon fiber reinforced composite material skin according to claim 1, characterized in that: A notebook computer (14) for displaying and processing the detection data is also included.

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