A novel solution methodology for longitudinal flight characterization of a Flying-Wing Micro Aerial Vehicle

Abstract

A longitudinal flight dynamic study of a low mass moment of inertia vehicle is presented. Aerodynamic and stability derivatives of a flying-wing microaerial vehicle (FWMAV) were obtained through detailed subsonic wind tunnel tests at a Reynolds Number of 1.87 x 10(5). Rate and acceleration derivatives were obtained using the potential flow solver, Tornado (R). A novel methodology for the estimation of dimensional derivatives is proposed, and results are compared with the conventional linear time-invariant systems (LTI) approach. Free response for natural frequency, damping coefficient, and time constant as well as forced response upon a unit step and a unit impulse elevon input has been calculated and analyzed. The proposed methodology predicted two pairs of complex conjugates for the longitudinal flight up to a pitch angle of 89 degrees whereas the conventional methodology predicted the same up to 57 degrees. Longitudinal modes sensitivity in terms of stability with the variation of mass, velocity, and pitch angle has also been analyzed. The flying-wing microaerial vehicle was able to sustain straight and level flight during flight trials; however, higher frequencies of phugoid and short period modes were observed. These high frequencies were the consequence of large magnitude of Z(alpha)/U-o (ratio of Z-force derivative with the angle of attack and cruise velocity) and Z(u)/U-o (ratio of Z-force derivative with the axial velocity and cruise velocity). It is concluded that the proposed methodology presented a more realistic representation of longitudinal flight modes since classical flight modes are captured till 89 degrees which conventional LTI methodology failed to do so.