Study Of Flapping Wing Micro Aerial Vehicle Based On Crank Rocker Mechanism

Since the conception of micro aerial vehicle (MAV) is put forth, the study of MAV has become the frontier research and attracted many researchers around the world for the great advantages in the field of military and civil applications. At present, the flapping wing MAV has become the hot point in the field of MAV research. Many problems need to be solved and related disciplines and fields are wide-ranging in the study of flapping wing MAV. The careful research work of flapping wing MAV, which is based on crank rocker mechanism, has been done. The main research contents are focused on design, fabrication and optimization of flapping wing mechanism, experiments in wind tunnel and study of vein. The main research contents and results of this thesis are as follows:The restrictive conditions of flapping wing mechanism are given. The parameters of flapping wing mechanism are determined by calculation and preliminary optimization. All parts are established and assembled to form a virtual flapping wing mechanism in UG, and the validity of the mechanism is verified by kinematical simulation. In fact, the real mechanism also works perfectly.To improve performance of the flapping wing mechanism, a co-simulation model is established by using ADAMS and MATLAB. Using the model, the effect of the parameters of motor vs. flapping frequency or the structure of the flapping wing mechanism (gear ratio and parameters of crank rocker mechanism) vs. flapping frequency have been studied. The select principle of DC micro-motor used in flapping wing mechanism is point out, a relatively optimal structural parameter is acquired and it is confirmed that the important factor of crank rocker mechanism in the flapping wing mechanism is L₃/L₁(length ratio of rocker to crank). Subsequently, the constraint force of fixed pedestal of the flapping wing mechanism is studies carefully, and the results suggest that the method of obtaining a bigger L₃/L₁ by shortening L1 is prior to by increasing L3 due to a less constraint force.The influences of rigid veins with different shapes, materials or initial setting angles on flapping frequency are studied and analyzed by means of the ADAMS and MATLAB co-simulation model. (1) The simulation results suggest that, comparing to the chord length, angle between beams and initial setting angle, wingspan or spanwise sectional area has an obvious effect on performance. And the influence derived from material of veins depends on variation of density. (2) Careful contrast of the change trends of physical quantities of veins and the performance shows up the common factor of veins is the moment of inertia Izz. Moreover, regardless of changes of veins, a reverse change trend always exists between moment of inertia Izz and flapping frequency. The relation of both is nolinear, despite it is approximately linear. Therefore, the moment of inertia Izz of veins is the controlling quantity and the common reason induced similar results. In addition,the inertial force on veins is abnormal, when initial setting angle is not equal to zero. The reason is that the x and y component of the force are appended a variable dependant on the direction of motion, respectively. (3) The effects of various changes of veins in wings are discussed, and some conclusions are drawn. The accurate method of eliminating inertial force in experiment is that the measuring object and its substitute have the same mass, center of mass, angular velocity and angular acceleration. When the angle between beams of veins is slightly adjusted, the change of inertial force is very little, but the performance may be obviously improved. So, when a researcher designs a wing, he should utilize those characteristics as much as possible. That is say; the target is to seek out the wing with the optimal aerodynamic performance from all veins with minimal moment of inertia. Lastly, in order to verify these simulations for various veins, some experiments have been done and the results of related literatures are quoted.For the purpose of understanding the aerodynamic performance, a flapping wing MAV is manufactured and the corresponding PIV(Particle Image Velocimetry)experiment is conducted in wind tunnel. The leading edge vortex is observed during a cycle by delayed photography. Using the external trigger photography, the changing flow field of flapping-wing MAV is studied under different flapping frequencies, inlet velocities and sections. The results show their respective infulences to the flow field.