Decoupled robust velocity control for uncertain quadrotors

In this paper, a decoupled robust velocity control method is investigated for a quadrotor. Although the quadrotor dynamics involves inter-axis coupling and nonlinearity, the quadrotor system is divided into four single-input single-output (SISO) subsystems. For each subsystem, a linear time-invariant robust controller is proposed, which uses its own states and consists of a nominal controller and a robust compensator. The nominal controller is designed by the proportional-integral-derivative (PID) control method to achieve the desired tracking for the nominal system. A robust compensator is added to restrain the influence of the parametric uncertainties, nonlinear dynamics, coupling, and external disturbances. The tracking error of each subsystem is proven to converge into an a priori set in the neighborhood of the origin in a finite time. Experimental results on the quadrotor demonstrate the effectiveness of the proposed control method.