Research On Design And Dynamic Characteristics Of Eagle-like Flapping-wing Aircraft With Multiple Flight Modes

Since ancient times,human beings have dreamed of flying like birds.Bionic flapping-wing aircrafts imitate many advantages of flying creatures,and have good concealability,high flight efficiency,low noise and good maneuver performance.Therefore,it has become an important direction of unmanned aerial vehicle development to develop a mobile and flexible aircraft like birds or insects,the bionic flapping wing aircraftresearch has become a research hot spot gradually.The research objective of this subject was to realize the complex and diversified flight modes of flapping-wing aircraft.The multi-mode space flapping-wing mechanism isdesigned based on bionics research,with dynamic characteristics analysis as the core,with the design and optimization of multi-flight mode flapping-wing aircraft as the ultimate goal.The combination movement of flapping,twisting and folding is realized,and then its kinematics,dynamics and aerodynamic characteristics are studied.The main research contents of this paper are as follows:(1)According to the body structure characteristics of birds,the characteristics and aerodynamic mechanism of flapping-wing flight of birds were analyzed.The design objective was determined by the scaling law analysis and bionic dimension parameter calculation.Through the aerodynamic estimation of eagle-like flapping-wings,the flight parameters under three typical flight modes of takeoff,cruise and landing were defined,and the theory and bionics basis were provided for the design of multi-flight model eagle-like flapping-wing aircraft.(2)According to the functional requirements of aircraft and considering the principles of economy,functional diversity and simple structure,the structure scheme of eagle-like flapping-wing aircraft and the switching principle of the motion mechanism were determined.At the same time,the whole structure of the aircraft was modeled by virtual prototyping technology,and its kinematics feasibility was comprehensively analyzed,which theoretically verifies the feasibility of the scheme.(3)The kinematics and dynamics mathematical models of the multi-flightmode imitated eagle-like flapping-wing mechanism were established.The kinematics characteristics of the eagle-like flapping-wing mechanism under different flight modes were analyzed,and the dynamic equation was established based on the Lagrange equation.The dynamic parameters such as crank balance torque and the force on the hinge point of the inner and outer sections of the wing were preliminarily calculated,which lay the foundation for aircraft structure optimization,flight stability and flexibility analysis.(4)The aerodynamic calculation model of eagle-like wings with multiple flight modes were established,and the aerodynamic forces generated by flapping and twisting of flapping-wing aircraft were synthesized and superimposed.Through the XFlow software,the structure and aerodynamic characteristics of the movement flow field of the multi-flight mode eagle-like flapping-wing were analyzed,and the effects of inlet velocity,flapping frequency,flapping angle and torsion angle on aerodynamic characteristics of composite flapping-wings in cruise flight mode were studied.(5)The parameter optimization model was established with the minimum output power during cruise flight as the optimization target.Based on the principle of particle swarm optimization algorithm,MATLAB software was used to simulate and optimize the motion parameters.At the same time,the 3d model of the bionic flapping-wing aircraft was improved according to the optimized motion parameters.