Research On The Dynamics Of Flapping-Wing Mechanism With Spring And Bearing Clearance

For its extensive applications in military and civilian, bionic flapping wing micro air vehicle (FMAV) has captured special attention of many researchers in recent years. Flapping wing mechanism is the key component of FMAV and the dynamic characteristics of the mechanism affect directly the performance of FMAV. The dynamics of a flapping wing mechanism is studied in this thesis.A flapping wing mechanism is designed to mimic the motion of bones and joints of flying animal and animal chest muscles. So a flapping wing mechanism with spring is taken as the model of this study. The aerodynamic force on the mechanism is computed using the method based on the simplified strip theory. The results show that the aerodynamic forces during up stroke and down stroke are greatly different, which causes the load on the motor fluctuation. To reduce such shock on the motor, the spring should be designed carefully. In this thesis, the optimization design of spring's parameters is presented, and the method to find the relationship between the stiffness of spring and the frequency of flapping is proposed.Bearing clearances is inevitable in a mechanism. In this thesis, the dynamic equation of the mechanism with bearing clearance and spring under the load of aerodynamic force is established using Dubowsky's impact pair model. The largest Lyapunov exponents and Poincare maps of the motion of the mechanism reveal that chaos exists under some circumstance of clearance magnitude, stiffness of the spring, and the frequency of flapping.Aerodynamic force is coupled with wing's angular velocity. When the motion of mechanism is chaotic, the aerodynamic force may fluctuate remarkably, which is unfavorable to flying. In order to overcome such disadvantage, the dynamic synthesis of flapping wing mechanism is discussed tentatively.The dynamic modeling, optimization and simulations in this thesis are conducted utilizing Matlab.