Flight Control Methods for Multirotor UAS

This paper presents several control methodologies for multirotor aircraft. It details simple control laws for body-axis rate or quaternion attitude tracking and provides an interpretation of control gains in terms of natural frequency and damping of the closed-loop system. Additionally, it describes a method for tuning the control gains via LQR. Control laws for translational dynamics, based on a nonlinear path-following control architecture, are also presented. Vertical and horizontal tracking are partially decoupled by dynamically scaling the thrust command, and an attitude protection method is added to prevent commands that would result in undesirable vehicle attitudes. The path-following input and error definition are modified to achieve position tracking, velocity tracking, or path-following control.