Measurements And Quantitative Analysis Of Geometrical Configurations Of Beetles Facing Biomimetic Applications

The geometrical configurations and body morphologies of insects have beenresulted from their evolution through upon millions years for adapting thesurroundings. For the biomimetic research based on the biological configurationsand surface morphologies, it has very important basic and biomimetica applicationvalues to conduct the quantitative analyses of geometrical configurations andcuticle morphologies and to find their interactive mechanisms with thesurroundings. Four beetles (dung beetle (Copris ochus Motschulsky), RhinocerosBeetle(Oryctes rhinoceros Linnaeus), Cetoniidae beetle (protaetia orentalis Goryor Perchron) and Dytiscid beetle (Cybister bengalensis Aube)) were taken as themain research animals. The body surfaces of their clypeus, pronotum and elytrawere measured quantitatively, the CAD surface models were reconstructured andthe surface profiles were analyzed quantitatively using the reversing engineeringmethod and a rapid prototyping method.The digital measurements of body surfaces of the four beetle animals werecarried out using a 3D laser scanner. White coating was sprayed on the bodysurfaces of the four beetle animals before measurement in order to conduct thedigital measurements. Three small balls with a radius of 1±0.01mm were utilizedduring the measurement to ensure that the data obtained by different scanning angleand at different time can be unified. The comparative analysis was conducted forthe different data point clouds with varied scanning steps and the scanningdirection. It was found that the data point clouds of the geometric surface of fourbeetle animals can be obtained by selecting the appropriate scanning step andscanning angle.By using special software of reverse engineering, The scanning data pointclouds were processed which included deleting error points manually, smoothingthe scanning data by Gaussian filter, averaging filter and median filter, samplingcharacteristic points from the scanning point clouds by Chordal Deviation method,Sample Uniform method and so on. Based on the reconstruction model of threesmall balls, the scanning data obtained from different angle and different directionwere registered and merged. Two methods, i.e. based-edge and based-surface, wereapplied to partition the scanning data to build up foundation for surfacereconstructed models of for four beetle animals.Two methods, i.e. point-curve-surface and point-surface, were used toreconstruct the geometrical configuration of four beetle animals. In thepoint-cueves-surface method, the accuracy and smoothness of reconstructingsurface were directly effected by the accuracy and amount of loft curves. Generally,the numbers of the loft curves were chosen from 16 to 32. the curves should havesame direction and equal nodes distribution. All of the curves must bere-parameterized so that the curves could keep compatible. When the point-surfacemethod was used to reconstruct biological surface, the curvature contour lines mustpass through the region where the curvature had a maximum. Creating the optimalcontour line layout was important to ensure the final surface includes necessarydetail. Other the final surface could lose model's topological detail.Some specific methods were used to evaluate the quality of the reconstructedgeometrical surface, which included the difference between the original pointclouds and the reconstructed surfaces, the surface smoothness and the multisurfacecontinuity. The difference between the geometrical reconstruction surfaces and theoriginal points were presented by rainbow plot, gray scale plot and tolerance basedplot. Based on analysis of the difference between the scanning points andreconstructed surface, it was confirmed that the point-surface method was betterthan the point-curve-surface method for the biological surface reconstruction. Thesmoothness of reconstructed surface was checked by various methods,such ascurvature technologies, the illumination analysis skill, and other ways. A visualfigure for displaying changes of surface smoothness was obtained. The surfacereconstruction continuity was measured and analyzed.A rapid prototyping printer (FDM-Dimension made by stratasys company)was used to fabricate a body with the reconstructiong surface.the data of reconstruction surface model were input to the software of therapid prototyping printer, the models data were processed by orienting the models,data slicing, generating support, writing boundary curves, generating tool paths andfinally writing CMB file to the printer. The biological surface moulding of theclypeus, pronotum and elytra of four beetle animals were made by The rapidprototyping printer.Several cross-section data points were extracted from the scanning pointclouds of the four beetle animals. The cross-section data points of elytra wereextracted along length direction and width direction. The Least Square fittingmethod was used to analyze the cross-section data for fitting mathematical modelsand the fitted curves were expressed by Gaussian equations. The errors werecalculated between the original data points and the fitting curves.The values of curvature and second derivative of the fitted contour curves offour beetles were calculated. By analysesing the changes in the curvature andsecond derivative values of the fitted curves, the geometrical characteristics of thefitted contour curves were summed up and the concavo-convex change of thebiological surfaces was deduced.Different cuticle morphologies structures and their functions of the four beetleanimals were compared and analyzed. The non-smooth structures on the clypeusand pronotum of dung beetle, such as the convex domes and small waves, couldprevent a continuous water films forming between their body surface and soil andreduce the frictional resistance. The middle-raised depressions on the elytra ofRhinoceros Beetle distributed with certain specific regulations. The depressionmight help the elytra weaken the air turbulent, reduce the air frictional resistanceand increase the flight impetus when the Rhinoceros Beetle flew. There were nonon-smooth structures on the head and pronotum of Dytiscd beetles. But the wavestructures on the elytra are very obvious and they are almost parallel to theswimming direction of Dytiscd beetles. The wave structures intersected each other.Such wave distribution might boost up the water flow stability and reduceswimming resistance by controlling the turbulent boundary layer when the Dytiscdbeetles were capturing fishes.The geometric surface configurations of the four beetles were analyzed basedon the equations, curvature, second derivative of the fitted curves. The analysisresults shown that the biological surface characteristics discribered by the functionsof fitted curves were same with the actual characteristics on the biological surfaceof the four beetles.The clypeus surface of dung beetle was simplified to a triquetrous wedge.When the triquetrous wedge moved along the wedge tip direction,the resistanceswere less than that when the wedge moved along the direction vertical to thecutting edge. The reason was that the cutting edge used different cutting modeswhen the moving direction changed. If the wedge moved along the wedge tipdirection, the cutting edge would use gliding cutting mode. The wedge used theimpact cutting mode while the wedge moved along the direction vertical to thecutting edge. The fan-shaped clypeus used mainly the gliding cutting when thebeetles moved along any directions. At the same time, the triquetrous wedge modelof the clypeus has the changable digging angle α, turning soil angle β, bulldozingsoil angle θ and breaking up soil angle γ. These changable angles give the clypeusexcellent functions for digging, pushing sidewise and breaking up the soil.By analysis, the mainly reason of the elytra producing the flight lift force wastheir configurations during the beetles flying. The size and orientation of the liftforce was changed by adjust the angle between the elytra and air flow. Theinteraction of the elytra and underwing could ensure the right steering and keepingbanlance.