Influence of Center of Gravity Location on Flight Dynamic Stability in a Hovering Tailless FW-MAV: Longitudinal Motion

Abstract

This paper reports the effect of the Center of Gravity (CG) position on lateral flight dynamic stability of hovering KUBeetle, a tailless FW-MAV, providing further insights on the effects of asymmetries in body mass distribution and wing kinematics. For the current study, the standard linearized equations of motion were applied as in the previous work on longitudinal dynamic stability. The stability derivatives were acquired using the computational fluid dynamic methods via the commercial software of ANSYS Fluent. There exists a stable region for CG between 2.6% and 3.5% of the mean chord below the wing pivot point, in which the lateral motion of hovering KUBeetle is passively stable. For CG below the stable region, because of an unstable oscillatory mode, the lateral motion of the FW-MAV is unstable but can be stabilized using rolling rate feedback. For CG above the stable region, because of a divergence mode, the system remains unstable even with the rolling rate feedback. Comparison with other works on an FW-MAV based on a quasi-steady aerodynamic model and on insect showed similar characteristics for flapping flight. It is also interesting to note that the asymmetries in body mass and wing kinematics can enlarge the stable region of the system by a non-zero Ixz which approaches the root square of √IxI2, a negative LrNp, and a positive Ixz(Ir+Np). Combining the current result with that of the previous work on longitudinal motion, the most beneficial region of the CG for full 6-DOF flight dynamic stability of hovering KUBeetle was suggested.