Research On Three-dimensional Surface Measurement Of Large-scale Aviation Components Based On Dynamic Coded Targets

As core components of large aircraft, bearing-load composite components with large size should meet requirements of long service life and high reliability. In order to ensure security and load-carrying performances of large bearing-load components in service processes of airplanes, the core components must realize high quality assembly with low stress. The connections between components need to achieve high reliability and low damage. While using the 3D (three-dimensional) reconstruction of surfaces of components to guide assembly process, the assembling gap and stress can be effectively controlled. Therefore, high-precision 3D measurement of the free-form surface of components is very important to guarantee assembly quality of bearing-load composite components with large size. Binocular vision measuring method has advantages of high efficiency, high precision and flexibility. This method has been widely used in aerospace field. Thus, based on the binocular vision measuring principle and the current industrial camera performance of dynamic acquisition, the research of non-contact dynamic global measurement method has been carried out. The main research content is as follows:(1) According to the measuring efficiency and surface quality requirements in the assembly process of large aircraft bearing-load components, a coding and decoding method of the dynamic projection code point based on flicker frequency coding is proposed, which is used in the image matching and global data registration of binocular cameras dynamic measurement. Through the experiment of extraction and matching of dynamic coding points, the reliability of this method is verified and the detection rate of the dynamic coding point is 100%(2) According to the global measurement requirements of the matching surfaces in the assembly process of large bearing-load components, a measurement method combining the local scan with the global control based on the dynamic coding point is proposed. In this method, two sets of binocular vision system are used to realize the local scanning measurement under the global control with high precision. The matching of point matrix is used to realize the solution and optimization of the coordinate transformation matrix. Eventually, the data of multiple local scanning measurement will be reconstructed in the global coordinate system to finish the global measurement of the components.(3) In order to realize the high precision matching of binocular cameras in dynamic measurement, and ensure the accuracy of feature matching and reconstruction, a binocular camera synchronous acquisition system based on Lab VIEW and high speed data acquisition and storage scheme for image data are designed, which can achieve dynamic and continuous acquisition of binocular camera. Synchronous acquisition experiment shows that the synchronization error of binocular camera acquisition is less than 0.01s;(4) According to the requirement of global measurement for large bearing-load components, the global measurement system for large component is built based on the above research. Then the global measurement system is calibrated, and the accuracy of the local and global measurement is verified by using standard parts with different specifications. The experiment results show that the average reconstruction error of the global measurement system is 0.2611mm, which meets the requirements of the global measurement for large aircraft components.