Measurements And Analysis Of The Elytron Cuticle Surfaces Of Several Coleopterous Insects By Reversing Engineering Method

The geometrical configurations of insects'body have been resulted from their evolution through upon millions of years for adapting their surroundings. For the biomimetic research based on the biological configurations and surface morphologies, the understanding of the quantitative geometry of the insects' configurations is important to develop biomimetica techniques. Four beetles (dung beetle (Copris ochus Motschulsky), Cetoniidae beetle (protaetia orentalis Gory or Perchron), Glabrous spotted willow borer (Anoplophora glaripennis), Harmonia axyridis (Harmonia axyridis(Pallas))) were taken as the main research animals. The body surfaces of their elytra were measured quantitatively, the CAD surface models were reconstructured and the surface profiles were analyzed quantitatively using reversing engineering method.The digital measurements of body surfaces of the four beetle insects' elytra were carried out using a 3D laser scanner. The comparative analysis was conducted for the different data point clouds with varied scanning steps and the scanning direction. It was found that the data point clouds of the geometric surface of four beetle insects' can be obtained by selecting the appropriate scanning step and scanning angle.By using special software of reverse engineering, the scanning data point clouds were processed including deleting error points manually, smoothing the scanning data by Gaussian filter, averaging filter and median filter, sampling characteristic points from the scanning point clouds by chordal deviation method, sample uniform method and others. Two methods, i.e. based-edge and based-surface, were applied to partition the scanning data to build up foundation for surface reconstructed models of for four beetle insects' elytra.Two methods, i.e. point-curve-surface and point-surface, were used to reconstruct the geometrical configuration of four beetle insects' elytra. In the point-curves-surface method, the accuracy and smoothness of reconstructing surface were directly affected by the accuracy and amount of loft curves. All of thecurves must be re-parameterized so that the curves could keep compatible. When the point-surface method was used to reconstruct the biological surface, the curvature contour lines must pass through the region where the curvature had a maximum. Creating the optimal contour line layout was important to ensure the final surface including necessary detail. Otherwise, the model's topological detail of the final surface could lose.Some specific methods were used to evaluate the quality of the reconstructed geometrical surface, which included the difference between the original point clouds and the reconstructed surfaces, the surface smoothness and the multi-surface continuity. The smoothness of reconstructed surface was checked by various methods, such as curvature technologies, the illumination analysis skill, and others. A visual figure for displaying changes of surface smoothness was obtained. The surface reconstruction continuity was measured and analyzed.Several cross-section contour data points were extracted from the scanning point clouds of the four beetle insects' elytra. The cross-section contour data points of the elytra were extracted as characteristics subarea along longitudental direction and transvers direction. The least square fitting method was used to analyze the cross-section contour data for fitting mathematical models and the fitted curves were expressed by Gaussian equations. The errors between the original data points and the fitting curves were calculated.The curvature and second derivative of the fitted contour curves of four beetles'elytra were calculated. The geometrical characteristics of the fitted contour curves were summed up and the concavo-convex features of the biological surfaces was deduced through analysis the changes of the curvature and the second derivative of the fitted curves.