Mathematical Modelling and Control of an Unmanned Aerial Vehicle with Moving Mass Control Concept

In this paper we present a novel concept of attitude control for a multi-rotor unmanned aerial vehicle by actively controlling its center of gravity. This research is a part of our efforts to build a heavy lift multi-rotor platform capable of carrying over 50 kg of payload. To that end, we propose using miniature two-stroke combustion engines to supply the necessary lift and combine them with moving masses used to control the vehicle attitude. In this paper we present a complete nonlinear dynamical model of such a vehicle and use it to derive the transfer functions of roll and pitch dynamics. Furthermore, we formulate a detailed root-locus based stability and sensitivity analysis of the proposed control scheme and discuss its underlining effect on the mechanical parameter design. We present the experimental testbed, consisted of the vehicle mounted on a 2 degrees of freedom gimbal, and derive necessary conditions for testbed parameters in order to match the testbed and free-flight quadrotor dynamics. Finally, we present simulation results from a Gazebo based simulator and experimental results of the testbed. Both results confirm the findings of our mathematical analysis.