System Identification of a Thrust-vectoring, Coaxial-rotor-based Gun-launched Micro Air Vehicle in Hover

Abstract

This paper discusses the flight testing and system identification of a compact, re-configurable, rotary-wing micro air vehicle concept capable of sustained hover and could potentially be launched from a 40mm grenade launcher. By launching these energy-constrained platforms to a target area, the mission range could be significantly improved. The vehicles used in the paper has a mass of 345 grams. The vehicle design features coaxial rotors with foldable blades, and a thrust-vectoring mechanism for pitch and roll control. Yaw control was accomplished with a specialized counterrotating motor system composed of two independently controlled motors. A comprehensive set of flight experiments were performed to excite the longitudinal, lateral, directional, and heave modes of the vehicle. A linearized statespace model was derived from the flight test data. The model showed that lateral and longitudinal dynamic modes were decoupled from each other and from the other modes of the vehicle. Due to the axisymmetric nature the vehicle design, the longitudinal and lateral stability and control coefficients and their eigenvalues were nearly identical. All of the aerodynamic damping terms were negative and stabilizing except for the pitch and roll acceleration modes. These two unstable modes necessitated the need for pitch and roll feedback control. The final flight dynamics model was compared against flight test data for each state, and the model shown good agreement with the experimental data.