Non-linear resonance modeling and system design improvements for underactuated flapping-wing vehicles

Insect-scale flying robots are currently unable to carry the power source and sensor suite required for autonomous operation. To overcome this challenge, we developed and experimentally verified a non-linear damping model of actuation-limited flapping-wing vehicles with passively rotating wing hinges. In agreement with studies on the wing dynamics of honey bees, we found that the optimal angle of the passive wing hinge in mid-stroke is about 70 ° rather than 45–50 ° as previously assumed. We further identified a narrow actuation force window in which the occurrence of a sharp resonance can be used to achieve both higher lift and efficiency. The findings from our model informed design changes to the Harvard Dual-Actuator Robobee, which resulted in a 130% increase in mean lift from ∼140mg to 320mg (with a vehicle mass increase of only 5 – 8%), along with a corresponding expected payload increase of 330 – 470% (30 – 40mg to 170mg). The power consumption only increased by ∼55%, making the new prototype 50% more efficient at lift production. Our model provides a greater understanding of the dynamics of this complex system, and the resulting lift and efficiency improvements are expected to bring insect-scale flying robots closer to autonomy.