A geometric formulation of multirotor aerial vehicle dynamics

A geometric dynamic modeling framework for generic multirotor aerial vehicles (MAV), based on a modern Lie group formulation of classical screw theory, is presented. Our framework allows for a broad range of rotor-wing configurations: any number of rotors can be attached in arbitrary configurations to either the body or wings, with the rotors and wings also tiltable. Our framework takes into account all masses and inertias of the MAV body and rotors, and accounts for both rotor thrust forces and moments as well as external aerodynamic and other forces. Compared to existing methods, our Lie group framework possesses several practical advantages useful for applications ranging from design optimization to model identification and trajectory optimization: (1) the dynamic equations can be easily transformed to coordinates of any reference frame; (2) kinematic and mass–inertial parameters can be easily factored from the dynamic equations; (3) exact, closed-form analytic derivatives of the dynamics with respect to the configuration variables are easily derived. We demonstrate our systematic modeling procedure on examples of fixed-tilt, variable-tilt and hybrid MAVs with wings.