Research On Kinematic Characteristics Of Flat Flight Of Flapping Wing Aircraft And Small Birds With Single Degree Of Freedom

Birds in nature,based on the complex structure of their wings,can flexibly adopt different flight modes to achieve different goals,while at the same time with high efficiency.Observing and studying different movement and flight efficiency of birds and ornithopters is beneficial to build kinematics simulation model of ornithopters and design flight controller of ornithopters.In this paper,for the first time,the relationship among the Strouhal number,the spatial asymmetry of the flapping trajectory and the Angle of attack of the flapping wing of the single-DOF ornithopter in flat flight is analyzed,and the theoretical models of the three are given,and the experimental results are verified.The optical motion capture system is used to collect the flight trajectories of single-DOF flapping wing aircraft under different positions of horizontal stabilizes.The results show that the actual values of Slauhal number,spatial asymmetry and Angle of attack of flapping wing are in good agreement with the theoretical surface,which proves that the theoretical model is reliable.We also collected the wing movement trajectories of six kinds of small birds,which were homing pigeon,red-eared bulbul,budgerigar,white-headed bulbul,mungbird and myna,during indoor flat flight or subflat flight with small wing deformation and similar movement mode to that of single-freedom ornithopter,and made comparative analysis.The results show that the above model is also applicable to these small birds.When the ornithopter flies flat with a small Angle of attack and the wings flapping space trajectory tends to be symmetrical,the Strouhal values are close to those of real birds.Furthermore,in this paper,the complex movement of the wings of a larger pigeon flying flat is studied experimentally and analyzed kinematically.The motion trajectories of shoulder,elbow,wrist and fingertip of pigeons were collected by motion capture system when flying indoors.Experimental observations show that the rotation of these joints on the wings of a pigeon during indoor flight is consistent with the model of a bionic arm with six degrees of freedom.Based on this assumption,we use an algorithm that can easily inverse solve the rotation transformation of the three joints through space geometric analysis and coordinate transformation,and then solve the rotation transformation of the wing joints of the pigeon when flying indoors flat and make an analysis and explanation.