Trajectory Tracking Flight Control of a Tethered Kite Using a Passive Sliding Mode Approach

Airborne Wind Energy (AWE) systems take advantage of high altitude wind in order to generate electrical energy. One of the challenges when harvesting energy with an AWE system is to deal with strong disturbances such as changes in the wind velocity. This paper proposes a robust trajectory tracking controller for an AWE system, namely a tethered kite, when it operates in the energy generation phase. The controller design is based on an approximate model of the kite and makes use of feedback passivation together with sliding mode techniques. The trajectory tracking error of the closed loop system in the presence of parameter variations and external disturbances is formally studied using Lyapunov stability theory. The performance of the controller is verified trough numerical simulations using a complete model of the kite.