Insect-scale flapping-wing MAVs with variable transmission ratio and wingspan: achieving payload adaptability, and self-stabilizing hovering

Insect-scale flapping-wing micro aerial vehicles (FWMAVs) possess compact dimensions, exceptional terrain adaptability, and operational stealth, presenting transformative potential for reconnaissance and environmental monitoring applications. However, current insect-scale FWMAVs typically suffer from limited payload capacity, making integrating the necessary electronic components for flight and functionality challenging. This study presents an enhanced structural design for an FWMAV that increases its payload capacity. By adjusting its transmission ratio and wingspan, the size and carrying capacity of the robot can be changed according to the demand. Based on this novel design, we manufactured FWMAVs with a variable wingspan ranging from 28 mm to 45 mm, the robots achieve a lift-to-weight ratio exceeding 2. This represents the insect-scale piezoelectric-driven FWMAV capable of successful takeoff by adjusting only the transmission ratio and wingspan, without altering other components. Notably, the 28 mm configuration is the smallest functional piezoelectric-decoupled FWMAV to achieve sustained lift-off. Additionally, the combined passive damper structure has allowed the robot to maintain stable hover for more than 5 seconds, achieving sustained air stagnation at an insect scale. These advancements provide certain technical support for further promoting the practical application of insect-scale MAVs.