Surrogate Based Rapid Design Optimization Of Rotor Blades Used In A Small Unmanned Aerial Vehicle

With the increasing demand for multi-rotor Unmanned Aerial Vehicle(UAVs)in investigation,mapping,transportation,etc.,its performance requirements have also increased accordingly.Load capacity and endurance have become important evaluation criteria in the optimization design of multi-rotor UAVs.In order to improve the performance of multi-rotor drones,the most direct and effective way is to optimize the shape of the rotor blades.Due to the complicated geometry of the rotor and the high sensitivity of the aerodynamic performance to the blade shape,many deficiencies exist in the current design and optimization of three-dimension(3D)rotor blades,such as dimensionality curses and large computational costs.To address these problems,a new optimization framework with a high-fidelity model of rotor blades in a UAV is developed to reduce the computation and simulation costs.The highaccuracy CFD model is built with rotor thrust errors within 5% over all the UAV rotation speed compared with experimental data.A 3D blade model with 22 design variables,including 6 planform variables and 16 section variables,using the Class Function/shape Function Transformation(CST)method is developed.Four surrogate models are constructed for rotor thrust and torque and the Kriging(KRG)model with the highest R-square is selected.Based on the KRG models,the Genetic Algorithm(GA)is used to perform the optimization of the torque at hovering thrust level by taking into account the airfoil thickness and the twist angle of blades.Compared with the E387 baseline rotor,optimization results show that the torque and the mass reduce by 10.71% and 26.78%,respectively,and the Figure of Merit(FM)increases by 4.5%.It is also certified that a better performance of the rotor blade happens in off-design conditions.Then,the one-way fluid-structural interaction are carried out to verify the feasibility of the proposed optimization framework for the rotor blades used in the UAV.In addition,the optimization design of rotor blades under different loads is also considered in this paper as a multi-objective optimization design.