Robust trajectory tracking control of uncertain quadrotors without linear velocity measurements

In this brief, robust trajectory tracking control problem for quadrotors is investigated to improve the tracking performance of the closed-loop control system subject to parametric uncertainties, non-linearity and coupling, unmodelled dynamics, and external disturbances. The vertical, lateral, longitudinal and yaw motions of the vehicle are required to be controlled along desired trajectories simultaneously. The proposed linear-decentralised controller consists of three parts: an observer to estimate the linear velocities, which cannot be measured directly, a position controller to achieve the trajectory tracking and produce the desired references for the pitch and roll angles, and an attitude controller to stabilise the attitude angles. The robustness properties of the whole uncertain closed-loop control system are proven. Experimental results are given to demonstrate the effectiveness of the proposed closed-loop control system.