Design of Monocoque Quadcopter Structure through Integration of Topology Optimization and Additive Manufacturing

Abstract

vi newlineABSTRACT newlineQuadcopters are one of the categories of Unmanned Aerial newlineVehicles (UAVs), rapidly attaining their eminence in the fields of newlineaerospace and armed forces. The need to operate for a longer duration newlineunder suitable payload is perhaps an exacting task. The flight time and newlineefficiency of Quadcopter typically rely on its weight. Among all the parts newlineof a Quadcopter, frame is the structural member that constitutes up to 30% newlineof total weight. Hence optimization of the Quadcopter frame is highly newlinerecommended. Therefore, it is aimed to design a light-weight structural newlineframe which is capable of lifting all-up weight of 2kg. newlineTo achieve this, the concept of integrating the Topology Optimization and newlineDesign for Additive Manufacturing (DFAM) is proposed for optimizing newlinethe Quadcopter frame. Two off-the-shelf models (open and closed newlineframes) are chosen for preliminary topological optimization studies. The newlinestatic structural analysis results are performed, and it is evident that the newlineclosed model is more suitable for lifting the all-up weight of 2kg. The newlineopen frame fails to lift because of its large deformation. Further, topology newlineoptimization is endeavored for the closed model to reduce its weight by newlineconsidering weight minimization as the objective function and allowable newlinevii newlinemaximum stress as the response constraint. The closed frame optimized newlinemodel has obtained slight reduction in weight of about 33grams. newlineHowever, still there is lot of scope in reducing the weight of closed frame newlinemodel. Besides, it consists of multiple parts and assembly of all the newlinecomponents requires a lot of effort and time. The fasteners add more newlineweight into the entire assembly and increases assembly time. In order to newlinealleviate these issues, redesigning the frame as a monocoque structure is newlinefocused. A unified body that minimizes assembly effort enhances newlinestructural integrity and ease of deployment is greatly facilitated. newlineIn order to do so, optimization studies on different shapes of newlinesolid blocks are considered and topology optimization is performed. The newlineresults suggested that square block has attained minimal weight in newlinecomparison to other blocks. The optimized model is complex in shape newlineand it is further modified by cleaning up its facets to achieve uniformity newlineand validated using static structural analysis. Due to its complexity, it is newlinedifficult to manufacture using traditional methods; Hence Fused newlineDeposition Modelling (FDM), which is one of the Additive newlineManufacturing techniques accounted for manufacturing the frame. To newlinereduce printing time and material, the principle of DFAM is incorporated newlineduring the process of Topology Optimization. The Solid Isotropic newlineviii newlineMicrostructure with Penalization (SIMP) optimization method is newlineintegrated with DFAM and resulted optimal monocoque model yielded a newlineweight reduction of 130grams. newlineFatigue analysis is performed to analyze its operating life and newlinenatural frequencies are determined using modal analysis. In order to newlineunderstand the flow pattern, to ensure stability and airworthiness of newlinemonocoque Quadcopter structure, Computational Fluid Dynamic (CFD) newlinesimulations are carried out for hovering and forward motion. Wind tunnel newlineexperiments are conducted to validate the calculated drag from the CFD newlineanalysis. Furthermore, the strain induced in the structure is analyzed by newlinemounting the strain gauges at the arm tip of Quadcopter structure. Based newlineon the strain gauge data, the simulation results are legitimized. Field trials newlineare conducted to examine the aerodynamic characteristics and estimate newlinethe endurance of the optimized monocoque Quadcopter. newlineThe integration of topology optimization and DFAM is novel newlinemethod of performing optimization studies which resulted substantial newlinereduction in mass of about 130 grams in comparison to standard method newlineof optimization where in 33grams of mass is reduced. newline