In order to ensure the assembly precision in the digital assembly process of large workpiece and reduce the assembly error caused by the standard point coordinate offset caused by surface deformation, an irregular surface workpiece strain field monitoring system based on FBG sensing array was designed. The system tests the surface deformation of the workpiece with gradient features by means of an FBG array laid on the surface of the workpiece. It can calculate the micro-displacement offset of the standard point of the workpiece. The simulation results show that the strain is related to the position, size and workpiece structure of the force application. The strain field has a significant gradient change on the surface of the workpiece. In the experiment, the FBG array arrangement was completed according to the strain gradient feature distribution. Each FBG can effectively acquire the dependent variable at each point. The relationship between the amount of micro-displacement and the wavelength shift under different applied conditions is obtained. The error distribution of the micro-displacement amount is calculated. It verifies the feasibility of the system.
In this paper, the uncertainty model of laser radar and Metrascan detection is established, combined with the the accessibility of laser radar in the actual measurement, the accuracy of the measured network is simulated and analyzed, and a digital measurement method, which combines the advantages of two advanced measurement techniques, Metrascan and laser radar, is proposed. This method of netted measurement for different digital equipment, uses a high precision laser radar coordinate system as the reference transformation coordinate system, improves the measurement precision of large-size measurement of Metrascan, thus, which realizes the high precision and high efficiency measurement for the digitization of the aircraft shape.
In the process of manufacturing large components, such as aerospace, automobile and shipping industry, some important mold or stamped metal plate requires precise forming on the surface, which usually needs to be verified, if necessary, the surface needs to be corrected and reprocessed. In order to make the correction of the machined surface more convenient, this paper proposes a method based on Laser 3D projection system, this method uses the contour form of terrain contour, directly showing the deviation between the actually measured data and the theoretical mathematical model (CAD) on the measured surface. First, measure the machined surface to get the point cloud data and the formation of triangular mesh; secondly, through coordinate transformation, unify the point cloud data to the theoretical model and calculate the three-dimensional deviation, according to the sign (positive or negative) and size of the deviation, use the color deviation band to denote the deviation of three-dimensional; then, use three-dimensional contour lines to draw and represent every coordinates deviation band, creating the projection files; finally, import the projection files into the laser projector, and make the contour line projected to the processed file with 1:1 in the form of a laser beam, compare the Full-color 3D deviation map with the projection graph, then, locate and make quantitative correction to meet the processing precision requirements. It can display the trend of the machined surface deviation clearly.