A new strategy is proposed in order to effectively design the components of actuation mechanisms for flapping wing micro air vehicles. To this end, the merits and drawbacks of some existing types of conventional flapping actuation mechanisms are first discussed qualitatively. Second, the relationships between the design of flapping wing actuation mechanism and the entrance requirements including the upstroke and downstroke angles and flapping frequency are determined. The effects of the components of the actuation mechanism on the kinematic and kinetic parameters are investigated. It is shown that there are optimum values for different parameters in order to design an efficient mechanism. Considering the optimized features for an actuation mechanism, the design, analysis, and fabrication of a new hybrid actuation mechanism for FWMAV named "Thunder I" with fourteen components consisting of two six-bar mechanisms are performed. The results show that this designed hybrid actuation mechanism has high symmetrical flapping motion with hinged connections for all components. The proposed methodology for the modeling and fabrication of Thunder I's actuation mechanism can be utilized as guidelines to design efficient FWMAVs actuation mechanisms.Drones 2019, 3, 73 2 of 21 amplification. This mechanism could provide the hovering capability for a small size flapping wing NAV. As for flapping wing at PAV scale, Wood et al. [22] have developed modern flapping wings which use piezoelectric actuators to generate flapping motion. Selecting the appropriate actuator is considered as an important part for designing effective flapping wing. Depending on the type of the system, different actuators can be used to perform the mission including electric motors, piezoelectric elements, solenoids, and Shape Memory Alloys (SMA) wires [23][24][25][26][27].Research on flapping wing MAVs has led to a variety of actuation mechanisms which are designed for flapping motion. These actuation mechanisms are four-bar, five-bar, and six-bar mechanisms. As for the four-bar actuation mechanism, five types have been used, as shown in Figure 1 [28-30].Drones 2019, 3, x FOR PEER REVIEW 2 of 20 mechanism for motion amplification. This mechanism could provide the hovering capability for a small size flapping wing NAV. As for flapping wing at PAV scale, Wood et al. [22] have developed modern flapping wings which use piezoelectric actuators to generate flapping motion. Selecting the appropriate actuator is considered as an important part for designing effective flapping wing. Depending on the type of the system, different actuators can be used to perform the mission including electric motors, piezoelectric elements, solenoids, and Shape Memory Alloys (SMA) wires [23][24][25][26][27].Research on flapping wing MAVs has led to a variety of actuation mechanisms which are designed for flapping motion. These actuation mechanisms are four-bar, five-bar, and six-bar mechanisms. As for the four-bar actuation mechanism, five types have been used, as shown in Figure 1 [2...