Electrostatic flapping-wing actuator with improved lift force by the pivot-spar bracket design

Appropriate wing rotational movements in flapping wing flight are essential to generate aerodynamic lift force. This paper presents the usage of a pair of “pivot-spar” brackets to guide rotational movements of an electrostatic flapping-wing actuator for enhanced lift force. The wing rotation pattern is guided by the bracket design with the help of numerical simulations. Wing movements with desired rotation pattern are recorded by a high speed camera and the instantaneous lift force generated by the flapping-wing actuator is measured by a test platform using a lever and a high-precision force sensor. Experimentally, the flapping-wing actuator using the “pivot-spar” brackets with a diverging angle of 40° can achieve a maximum wing rotation angle of 29° and generate an aerodynamic lift force at 79.2 μN. Besides, this work also uses advanced micro fabrication methods based on laser cutting technique and the mass of the flapping-wing actuator can be reduced to 50 mg. With 2.5 times higher lift force at 79.2 μN and 20 times lower overall system mass at 50 mg as compared with the earlier report, 50 times higher efficiency is achieved by calculating the total lift force/weight ratio for the presented electrostatic flapping-wing actuator with “pivot-spar” design. This result advances the field of electrostatic flapping-wing actuator toward its possible takeoff in the future.