Multiphysical Modeling of Energy Dynamics for Multirotor Unmanned Aerial Vehicles

Abstract

Energy performance, e.g. flight time and range, is currently a major challenge limiting the electric multirotor unmanned aerial vehicle (UAV). Improving UAV energy performance through design, control, and planning has received increasing attention lately. The basis for these efforts is an in-depth understanding of the underlying governing dynamics, which involves the aerodynamics of the rotor-propeller assembly, electro-mechanical dynamics of the motor and motor controller, electrical dynamics of the battery, and the rigid body dynamics of UAV. A system-level model incorporating all these dynamics, and more importantly, their coupling is missing in current literature. The goal of this paper is to fill this critical gap in the state of art. We first develop sub-models for each sub-system dynamics based on first principles, and then integrate them based on input-output coupling to formulate a system-level model. The model is capable of predicting the response of critical system variables and their mutual impact during the UAV flight operation. One key observation is that battery voltage can drop by 16% due to the energy consumed by propulsion, which in turn causes 14% decrease in rotor speed and 24% decline in torque and thrust (under the same actuation command) over the course of flight.