DESIGN AND STUDY OF FLAPPING MECHANISM WITH ASYMMETRIC FREQUENCIES

Abstract

Micro air vehicle (MAV) is defined as unmanned air vehicles with wing to wing span of 150 mm and weight not more than 100 grams, specifications defined by American Defense Advanced Research Projects Agency (DARPA). MAV finds its applications in surveillance, rescues and other strategic military purposes. The major impediment in its adoption is range. This requires efficient aerodynamics with light weight mechanisms and least possible actuators. In this work a wing flapping mechanism is proposed. A single actuator drives both wings making the design compact. There is a provision for introducing or correcting asymmetry in flapping frequency of the two wings while keeping the amplitude fixed. Continuously varying transmission utilizing friction is used to achieve a linear change in asymmetry. The sensitivity of the frequency change mechanism can be tuned to reduce the motion and power requirements. A scaled physical prototype has been realized to verify the functionality. Loop closure and Denavit-Hartenberg approach is used to simulate the kinematics of the system. Commercial codes are used for validation and final design. A parametric study was done to establish the effect of changing parameters of this proposed mechanism. Power requirements for the scaled prototype were compared with values from software analysis. The results are in close agreement. The prototype mechanism can be used for experimental study of aerodynamics of single flapping wing or two wings flapping at different frequencies.