An automated cooperative transfer method based on "light-field" for multiple automated guided vehicles (AGVs) is proposed to address the coordinated transfer of large aircraft sections. Utilizing laser measurement and control strategies, the method aims to enhance assembly efficiency and precision in aircraft manufacturing. First, a workspace measuring and positioning system (wMPS) is used to acquire real-time position and orientation data of each AGV, and a kinematic model of the transfer system is established to determine motion error. Next, combining fuzzy control with PID control, a fuzzy PID control algorithm adaptable to complex industrial environments is designed to adjust AGV cooperative motion errors in real-time, ensuring high-precision coordinated transfer. Experimental results indicate that the fuzzy PID control significantly improves the motion accuracy and load balance of the multi-AGV system under both unloaded and loaded conditions. Compared to open-loop control, the closed-loop approach maintains error within ± 10 mm, reduces the average load on positioning actuators by over 30%, and limits the maximum load to within ± 300 N. Additionally, dynamic adjustments of transfer tooling during the entire process effectively prevent potential section damage due to excessive force. This study provides technical support for the construction of flexible assembly lines for domestically produced large aircraft, showcasing substantial application value and potential for broader adoption.

Machine vision technology, characterized by its non-contact, high-precision, and automated features, has been widely applied in aerospace assembly. This paper reviews the current status of machine vision technology in aerospace assembly from the perspectives of visual measurement, visual guidance, and visual inspection. Visual measurement, through the acquisition of image information of components, realizes pose measurement, shape and size inspection, as well as hole position accuracy control, thereby enhancing assembly precision and reducing assembly errors. Visual guidance, through image analysis, accurately determines the relative pose of assembly robots or other equipment, thus improving the level of automation. Visual inspection is used to identify problems such as misfitting, overgrowth, and assembly damage during the assembly process to ensure the quality of the final product. In the future of aerospace assembly, machine vision technology will be integrated with other sensors and artificial intelligence techniques to build digital measurement systems, further enhancing the efficiency and precision of assembly.

This paper proposes a non-destructive method for measuring the thickness of thermal barrier coatings on aero-engine turbine blades, based on three-dimensional point cloud data. Initially, a line laser sensor is employed to acquire 3D point cloud data from the blade surface. Subsequent processes, including point cloud clipping, filtering, and registration, are implemented to mitigate noise and minimize clamping errors. The local normal projection method is then utilized to compute the distance between the point clouds of the coated and polished blades and the point cloud of the initial substrate, thereby enabling the determination of coating thickness. Experimental results indicate that this method exhibits robust feasibility and precision in the non-destructive assessment of thermal barrier coating thickness. Compared to the metallographic microscope measurements, the average relative errors of the coating thickness calculations for three samples after spraying were 2.69%, 2.54%, and 2.07%, respectively, while the average relative errors after polishing were 2.79%, 2.66%, and 3.08%. Furthermore, this study analyzes the sources of systematic errors, including point cloud acquisition errors, registration errors, and thickness calculation errors, and presents corresponding improvement measures. Overall, the findings suggest that this method is suitable for a diverse range of coating materials and has the potential to significantly enhance the detection efficiency and accuracy of aero-engine turbine blades.

Vision 3D measurement is an important non-destructive testing method in pipeline machining and performance monitoring. In order to apply the measurement system to the restricted space in the pipeline and ensure measurement accuracy, the existing 3D measurement methods mainly focus on the study of the measurement principle and the sensor structure, there is a lack of research on pipeline image processing and feature extraction algorithms, and the metal material of pipeline leads to the problem of reflection in the image, which seriously affects the accuracy of feature extraction and pipeline measurement. In order to study the feature extraction of reflective surfaces in vision 3D measurement of the pipeline, a method of reflection removal based on dynamic region segmentation and a method of laser center extraction are proposed. A dynamic annular mask is designed according to the morphological characteristics of the projected laser of the measurement system to eliminate the reflection interference, and an automatic selection method of Gauss kernel and extremum points is designed to overcome the interference of uneven feature width in the laser center extraction. The accuracy of the method is verified by experiments, and the characteristic coordinates are provided for the vision 3D measurement of the pipeline. The diameter and coaxiality of the pipeline are measured, and the measurement accuracy is higher than 0.1 mm.

In the aviation field, the detection of surface defects on aircraft skin is crucial for ensuring flight safety. In response to the shortcomings of existing aircraft skin defect detection algorithms in small object detection, this paper proposes an aircraft skin defect detection algorithm based on an improved EfficientDet model. First, the convolutional block attention machine (CBAM) was integrated into the backbone EfficientNet to enhance the model's attention to defect areas. Second, the hierarchical structure and feature fusion strategy of bidirectional feature pyramid network (BiFPN) were optimized and adjusted to further enhance the ability of feature extraction and multi-scale feature fusion for small target defects. Finally, a scale aware loss function was adopted to enhance the robustness of the model in defect detection at different scales. The experimental results on the self built aircraft skin defect image dataset show that the improved algorithm achieves an average detection accuracy of 91.32%, which is 3.69 percentage points and 2.05 percentage points higher than EfficientDet-D0 and YOLOv5s, respectively. It has significantly improved the detection accuracy and performance for aircraft skin defect types such as paint peeling, scratches, and dents.

In order to quickly inspect hole position and normal vector of mounting holes on aircraft part, an onmachine inspection system based on machine vision was developed in this paper. The developed visual device, mounted to machine tool spindle, acquired image of mounting hole and laser spots along measuring path. The kinematic model for hole inspection was established. And method for calibration of system parameter was proposed, too. Special image processing method was designed for calculation of 2D coordinate of mounting hole position and laser spot. The verification experiment was carried out on test piece, and the result shows that the inspection accuracy of hole position and normal vector on aircraft part can reach 0.05 mm and 0.5° respectively, and the system can measure 15 holes per minute, which realizes the effective on-machine inspection of mounting holes on aircraft part.

To address the need for 3D digital quality inspection of spatially distributed circular holes in aerospace manufacturing, this paper systematically investigates methods for spatial positioning and 3D reconstruction of machined circular holes based on vision measurement technology. To mitigate the influence of surface quality and texture of machined circular holes, an image extraction method for circular holes based on arc-segment grouping technology is adopted, along with a proposed effective screening mechanism. A dual-cone reconstruction and intersection algorithm is introduced to preliminarily position the circular holes in space, providing initial values for the spatial circle pose. An error equation for optimizing the spatial circle pose is established, and the Levenberg-Marquardt (LM) algorithm is used to refine the pose solution, leveraging intrinsic and extrinsic camera parameters obtained through multi-view geometry. Circular hole arrays with diameters ranging 2 – 8 mm were machined on three samples in spatial distributions. The proposed method achieved precise identification and reconstruction of circular hole edges and positions, with an average deviation of reconstructed circles from CAD models within 0.112/– 0.100 mm and a maximum deviation not exceeding 0.200/– 0.200 mm.

After curing and molding, the large curvature carbon fiber skin will produce a large curing deformation, resulting in a gap between the skin and the skeleton, and the composite skin will bear a certain assembly load when riveting assembly. In order to control the assembly load in the assembly process of large curvature carbon fiber skin riveting assembly, a numerical calculation model of the riveting process of composite skin was constructed, and a riveting sequence optimization model was established with the maximum strain of the skin during the riveting process being the smallest, and the loading point and constraint point support reaction force being less than the critical value as the constraint conditions, and the optimization model was solved by genetic algorithm and ABAQUS secondary development. The results show that the maximum strain of the composite skin under the preferred riveting order is significantly smaller than the strain during riveting according to the process experience order, which proves that the method is effective and feasible.

Titanium alloy was widely used in the machining of aviation parts. In the deep cavity milling process of titanium alloy parts, the tool rod with large aspect ratio will vibrate. Aiming at the vibration problem of the cutter with large draw ratio, the dynamic model of the designed milling cutter was established based on the Euler-Bernoulli beam theory, and the parameters affecting the dynamic performance of the cutter were analyzed. Based on the analysis of parameters, design of four core shaft models, through the analysis it was concluded that the best core shaft. Then the toolholder model was established, and the static stiffness, natural frequency and dynamic stiffness of the traditional metal toolholder and damping toolholder were compared by finite element analysis. The results show that the static stiffness of the damping toolholder is increased by 62%, the first natural frequency is increased by 21%, and the dynamic stiffness is increased by 135%. The roughness of the machined surface with two kinds of toolholders was tested, and the roughness of the designed composite damping cutter bar is reduced by 45.3%. The designed compound damping cutter bar has certain engineering significance and academic value, and provides certain guidance for the design of machining tools with large length diameter ratio.

Aiming at the phenomenon that feed rate affects the error of machine tool, the influence of feed rate on the compensation effect of CNC machine tool under error compensation is studied. Taking the X and Y working planes of CNC machine tools as an example, firstly, the positioning errors of X and Y axes are measured and compensated by a laser interferometer. Secondly, the X and Y axes of the machine tool are controlled to move in a circular trajectory at different feed rates, and the double ball bar is used to measure the contour error of the circular trajectory. The results show that the contour error of CNC machine tools increases with the increase of feed rate, which verifies that the contour error is proportional to the square of feed rate. At the same time, by comparing the error compensation effect under static state and different feed rates, it is found that the latter has a poor compensation effect, only reducing the roundness error by 26.6 %, indicating that the feed rate seriously affects the error compensation effect. Therefore, considering the influence of feed rate when compensating the error of machine tool can better reflect the actual error of machine tool, improve the compensation effect, and provide a theoretical basis for the comprehensive error modeling of machine tool.

TA32 titanium alloy has better creep resistance than TC4 titanium alloy at high-temperatures, which is widely applied in the hypersonic aircraft. It is challenging to meet the dimensional requirements for the complex components of TA32 titanium alloy due to the springback after hot forming. The stress relaxation behavior of TA32 titanium alloy was studied at different temperatures (650 ℃, 700 ℃, 750 ℃, 800 ℃) and pre-strains (2%, 4%, 8%). With the increasing temperature, the stress relaxation rate at the first stage increases, and the limit of stress relaxation decreases. Based on the experimental data, the explicit constitutive equation of stress relaxation was fitted with the quintic delay function, and the Arrhenius type creep constitutive model was established. Considering the effect of high-temperature stress relaxation, the hot forming simulation model of a TA32 titanium alloy reinforced frame was established, and hot forming and springback test verified the reliability of the simulation model. The results show that the springback can be effectively reduced due to holding process. With the holding time increasing from 10 s to 1800 s, the springback decreases from 3.15 mm to 2.55 mm. When the holding time reaches 300 s, the stress reaches to the relaxation limit, and the springback is almost unchanged.

Film hole cooling technology is an effective means to improve the temperature bearing capacity of turbine blades, while the recast layer on the hole wall caused by EDM processing of film holes is a serious threat to the service performance of film holes. In order to eliminate the recast layer, this paper puts forward a process method to eliminate the recast layer on the wall of EDM hole by secondary heat treatment. Experimentally, it was found that the recast layer of the hole wall obtained by EDM was γ single-phase organization, with internal holes and microcracks, and the phenomenon of compositional segregation existed. Subsequently, the heat treatment process of solid solution and aging of the film holes revealed that the original recast layer region formed a two-phase organization consistent with the matrix, with uniform composition distribution. At the same time, the original recast layer region was oriented in the same direction as the matrix, ensuring the overall single-crystal characteristics of the blade. The high-temperature tensile experiments show that the elimination of the recast layer avoids the hazards of the hole wall defects and changes the fracture mechanism, which improves the tensile strength and elongation of the film holes. Therefore, the proposed process of removing recast layer by EDM based on secondary heat treatment provides a reliable means for the manufacture of high-quality film holes.