Abstract: The influence of Center of Gravity (CG) location on longitudinal dynamic stability of hovering KUBeetle, a tailless Flapping-Wing Micro Air Vehicle (FW-MAV), is reported in this paper. The rigid-body approximation was assumed, allowing application of the standard equations of motion used for fixed-wing aircraft. For each considered location of CG, stability derivatives were obtained using the computational fluid dynamics method via the commercial software of ANSYS Fluent. The dynamic stability was studied using technique of eigenvalue analysis. There exists a narrow stable region for CG between 23% – 24% of mean chord above the wing pivot point, where the longitudinal hovering of KUBeetle is passively stable. When CG is located below the stable region, the analysis identifies two subsidence modes and one unstable oscillatory mode, which makes the hovering of KUBeetle unstable. However, it can be stabilized using pitching rate feedback. When CG is located above the stable region, the system yields one stable oscillatory mode, one subsidence mode, and one divergence mode. Because of the divergence mode, the system remains unstable even with the angular rate feedback. These results share similar characteristics to another FW-MAV and insects. This study may provide a reference for FW-MAV developers.

Key words: center of gravity, hovering, longitudinal dynamic stability, computational fluid dynamics, flapping wings, bioinspired flight