Control of vertical take off, dynamic flight and landing of hybrid drones for airborne wind energy systems

A control design approach for a hybrid multi-copter/box-wing drone is presented. The drone is designed to be used in an airborne wind energy system, where tethered aircrafts are used to convert wind energy into electricity. It features four propellers and multiple aerodynamic control surfaces, and can operate either as multi-copter or as airplane. The goal is to achieve fully autonomous take-off, transition to dynamic flight, and landing. A model-based, hierarchical feedback controller is proposed, with linear inner control loops to stabilize the drone's attitude, and an outer nonlinear loop to obtain the desired flight trajectory. A switching strategy is employed to transition from hovering mode (i.e. multi-copter) to dynamic flight mode (i.e. airplane), and vice-versa. Simulation results with a realistic model indicate good performance and robustness in all flight conditions, notwithstanding the controller simplicity.