RESEARCH PAPER Design and Analysis of a Flapping Wing Mechanism with Asymmetric Frequencies for a Micro Air Vehicle S. Iqbal 1 • H. N. Gilani 2 • R. A. Azim 3 • A. A. Malik 1 • S. M. Zafar 1 Received: 4 September 2014 / Accepted: 16 January 2015 / Published online: 11 April 2016 Ó Shiraz University 2016 Abstract The design and development of flapping wing micro air vehicles is an active research area. In this study, design of a wing flapping mechanism is presented based upon continuously variable transmission systems. This mechanism is capable of generating flapping modes, with different and adjustable frequencies for the two wings of a flapping wing micro air vehicle. 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 sen- sitivity of the frequency change mechanism can be tuned to reduce the motion and power requirements. A shift in the location of the center of gravity also occurs simulta- neously assisting in roll motion control. The simulation of this dynamic system shows that different flapping fre- quencies for two wings of a flapping wing micro air vehicle have been achieved. A remarkable feature of this mechanism is the provision of varying the flapping fre- quency for both the wings with a single actuator during flight which not only reduces the weight of the mecha- nism but also the power requirements. A prototype has been realized to verify the functionality of this new design concept. Computer codes and commercial software’s were used to simulate kinematic and dynamic results. An aerodynamic analysis of wing profile and parametric study of link lengths has been done. Experimental values for power requirements using the prototype developed were compared with those obtained from analysis based on computer software. Results for the kinematic and dynamic simulations and experimental setup for the mechanism are presented. Keywords Flapping wing micro air vehicle Á Asymmetry Á Continuous variable transmission Á Mechanism Á Kinematic analysis Á Dynamic analysis 1 Introduction Small-sized air vehicles with high speeds and good maneuverability have a promising future in search and rescue operations, particularly in the aftermath of a natural disaster, hazardous environment exploration, military surveillance, high-resolution weather, climate mapping, and traffic monitoring, and so on. The micro air vehicles (MAVs) may consist of fixed wing, rotary wing, and flapping wing type systems. The flapping wings MAVs (FMAVs) are further classified into symmetric and asym- metric FMAVs. Asymmetry in flapping is due to asym- metric amplitude or asymmetric frequency. The literature available on asymmetric flapping frequency effects is limited, so there is a need to carry out a study on the effects of asymmetric flapping frequencies and means of correct- ing these during the flight if required. A mechanism is designed and presented in this study, which can continuously and linearly vary relative flapping frequencies. This mechanism can be designed for a par- ticular shift in frequency with a desired sensitivity. Con- versely, a desired asymmetry in flapping frequencies can & S. Iqbal sohail.iqbal@mail.au.edu.pk 1 Department of Mechanical and Aerospace Engineering, IAA, Air University, Islamabad, Pakistan 2 Department of Mechatronics Engineering, Air University, Islamabad, Pakistan 3 Department of Mechanical Engineering, NUST College of Electrical and Mechanical Engineering, Rawalpindi, Pakistan 123 Iran. J. Sci. Technol. Trans. Sci. (2016) 40:75–89 DOI 10.1007/s40995-016-0012-0