Stabilization and Path Tracking of a Mini Quadrotor Helicopter: Experimental Results

Quadrotor helicopters are gaining notoriety as research platform of unmanned aerial vehicle (UAV), due to its mechanical simplicity and high maneuverability, as well as the ability to hover and perform vertical take-off and landing (VTOL). However, the development of control systems for such vehicles is not trivial. Quadrotors have a nonlinear and open-loop unstable behavior and they are constantly affected by aerodynamic disturbances and unmodeled dynamics. In this article, a cascade PID control strategy designed for stabilization and path tracking of an unmanned quadrotor is presented. The dynamic motion equations are obtained by the Lagrange-Euler formalism. The proposed control structure consists of an outer loop for the translational movements, followed by an inner loop for the stabilization of the quadrotor’s attitude motions. Simulations and experimental results check the performance achieved with the proposed control strategy. The aircraft used is the Crazyflie 2.0 and the state estimation is accomplished through an extended Kalman filter, where information from the inertial measurement unit is fused with positional information from an ultra-wideband system.