Aerodynamics Experimental Results of a Bio-Inspired Flapping Wing With SMA Micro-Wire Muscles and Resonant Compliant Joints

Abstract This study introduces the aerodynamic forces measurements of a novel bio-inspired drone design, drawing inspiration from bat flight dynamics while using Shape Memory Alloy (SMA) micro-wires as artificial muscles. Unlike conventional drones powered by motors coupled with gears, this bio-mimetic drone relies on an agonist-antagonist muscle-like system of SMA wires activated by an electrical signal, imitating the animal wing structure. The presented research focuses on lift measurements derived from a flapping wing operating at different frequencies. The combination of SMA micro-wire agonist-antagonist configuration, low-density membrane, and optimized compliant joint led to achieving aerodynamic force production. The results obtained demonstrate a lift force up to 8 grams, first aerodynamic result produced exclusively by SMA micro-wire bundle actuators, which weigh less than a gram. The resonance of the joint unlocked the flapping movement at 8 Hz, with a joint angle span of about 60 degrees, using only a bundle of 4 SMA wires of 50μm diameter. This led also to reduced energy consumption, with 20% duty-cycle pulses of approx. 3 Watts as input power. The experimental data achieved demonstrates the feasibility and advantages of using SMA micro-wires in bio-inspired micro aerial designs, also showing innovative approaches to address the challenges given by using this material as robotic actuators. The presented first aerodynamics experimental results, obtained with no advanced optimization yet to implement, confirm the potential of this design to offer a new and effective route for bio-inspired aerial robotics, considering the implementation of muscle-like smart materials in combination with smart yet simple mechanical solutions.