Bio-inspired buckling joints improve post-collision stability in flapping wings: a structural dynamics perspective

Abstract

Flapping wing micro air vehicles (FWMAVs) have received significant attention in recent years for their size, maneuverability, and potential use in dangerous or congested environments. However, FWMAVs are susceptible to destabilization following in-flight wing collisions, which are inevitable. In recent work, bio-inspired buckling mechanisms have been introduced into FWMAV wings to improve collision robustness by passively mitigating destabilizing effects. However, the physical mechanisms by which these joints influence vehicle stability remain poorly understood. To better understand the role of buckling joints in stability, we designed a test beam comprised of two flexible segments interconnected by a buckling joint. The test beam was subjected to a series of quasi-static torque-displacement and dynamic disturbance tests. Results of the test beam were compared against a homogeneous control beam. In quasi-static torque-displacement tests, the test beam dissipated 3 times more energy compared to the control beam as indicated by hysteresis loops. In dynamic disturbance tests, the test beam exhibited reduced path disturbance as described by the Integral of Squared Error (ISE), which quantifies the cumulative deviation of a signal from a reference trajectory over time. Specifically, the test beam reduced average ISE by over 90% from the control averages for 6 out of 9 input conditions tested. The improved trajectory recovery in the test beam results from lower angular impulse and work imparted by the disturbance. Overall, angular work done by the disturbance was 3 times higher for the control beam than the test beam and the maximal average impulse imparted by the disturbance was approximately 5 times higher for the control beam than the test beam at the same input setting. This study advances the understanding of how bio-inspired buckling joints can improve FWMAV stability following collisions.