The paper discusses flight-test-based system identification of a compact, re-configurable, rotary-wing micro air vehicle capable of sustained hover and could potentially be launched from a 40-mm grenade launcher. The objective was to extract a linear time-invariant model of the system to gain an understanding of a novel coaxial helicopter. The vehicle design features a cylindrical fuselage, coaxial rotors with foldable/deployable blades, thrust-vectoring mechanism for pitch/roll control, and differential rotational speed for yaw control. Flight experiments were conducted to excite the vehicle’s longitudinal, lateral, directional, and heave modes from a hovering state. A linearized state-space model was extracted from the flight test data. The model showed that the lateral and longitudinal dynamic modes were decoupled from each other and from the other modes. Due to the axisymmetric vehicle design, the longitudinal and lateral stability and control coefficients and their eigenvalues were nearly identical. All the aerodynamic damping terms were negative and stabilizing except for the pitch and roll acceleration modes, which necessitated the need for pitch and roll feedback control.
Denton et al. (Tue,) studied this question.