Structural Design and Non-linear Modeling of a Highly Stable Multi-Rotor Hovercraft

This paper presents a new design for a Multi-rotor Unmanned Air Vehicle (UAV). The design is based on the requirement of highly stable hover capability other than typical requirements of vertical takeoff and landing (VTOL), forward and sidewise motions etc. Initially a typical Tri-rotor hovercraft is selected for modeling and analysis. Then design modifications are done to improve the hover stability, with special emphasis on compensating air drag moments that exist at steady state hover. The modified structure is modeled and dynamic equations are derived for it. These equations are analyzed to verify that our structural modifications have the intended stability improvement effect during steady state hover. Keywords: Multi-rotor Crafts, T-Copter, Rotational Matrix, Pseudo Inertial Matrix, Coriolis Acceleration, Air drag moment, Swash Plate