A bio-inspired bistable flapping thrust mechanism with flexible suspension

The nonlinear oscillating wing stroke of diptera has been attributed to a pre-compressed flight motor anatomy. To date, biological evidence has demonstrated the nonlinearity and mathematical evaluations of simplified mechanical wing motor models link empirical observations to characteristic bistable oscillator dynamics. It was concluded that the fast switching between two stable wing orientations leads to high velocity movements, capable of large aerodynamic force generation which is more efficient than sinusoidal motions. While interesting and informative, the investigations have yet to address why the pre-compressed motor anatomy is well-suited to produce flapping aerodynamic forces for various flight conditions. This research seeks to explore the benefits of the dipteran wing motor through a representative structural model to uncover motor components and configurations important for flapping force generation. With such a study, improved design solutions for flapping mechanisms may be proposed that could find application in micro air vehicles. Analytical and experimental investigations suggest that the combination of adjustable axial suspension of the motor and its degree of pre-compression critically regulate the wing motor motions. While bistable motor configurations are shown to produce the most energetic dynamics, the vast range of velocity amplitudes obtained from a variably pre-compressed and stiffened motor exemplify a substantial versatility of flapping force generation is available for advanced flight control. The results suggest that micro air vehicles adopting a pre-compressed wing motor with axial flexure may greatly benefit in incorporating control over axial pre-load and suspension characteristics to enhance the range of flapping forces achievable.