A high liftoff speed insect-scale aerial robot direct-driven with piezoelectric bimorph PZT actuator

Insect-scale flapping wing aerial robots actuated by piezoelectric materials—known for their high power density and rapid frequency response—have recently garnered increasing attention. However, the limited output displacement of piezoelectric actuators results in complex transmission methods that are challenging to assemble. Furthermore, high piezoelectric coefficient materials capable of large displacements for direct wing actuation are fragile, costly, and relatively bulky. This article presents a novel design for minimalist insect-scale aerial robots, where piezoelectric bimorph PZT actuators directly drive two pairs of wings, thus eliminating complex transmission mechanisms and reducing fabrication complexity. These robots demonstrate high liftoff speeds and favorable lift-to-weight ratios, and they can achieve vertical ascent under uncontrolled open-loop conditions. The piezoelectric direct-driven two-wing insect-scale aerial robot, based on this approach, features an 8 cm wingspan and a prototype weight of 140 mg, successfully achieving takeoff under unconstrained conditions with an external power source. To further enhance insect-scale aerial robot performance, we optimized the wing-to-actuator ratio and wing arrangement. We propose a biaxial aerial robot with an X-shaped structure, a 2:1 wing-to-actuator ratio, a 70 mm wingspan, and a total mass of 160 mg. This structure demonstrates a high lift-to-weight ratio of 2.8:1. During free flight, when powered externally, it attains a maximum takeoff speed exceeding 1 m/s and achieves a vertical takeoff height surpassing 80 cm under uncontrolled conditions. Consequently, it ranks among the fastest prototypes in the milligram-scale weight category.