Control of an airborne wind energy system using an aircraft dynamics model

We consider the modeling aspects of an airborne wind energy (AWE) system which consists of a kite (or glider aircraft) with a tether connected between the kite center of mass and a generator (load) on the ground. Kites in AWE systems move in high-speed crosswind motion at several times the wind velocity to efficiently harness wind energy. Central to the controller design for maximum power generation is the accurate modeling of the kite and tether dynamics. In this work we use aircraft dynamics models that incorporate rotational pitch, roll, and yaw dynamics in the equations of motion. Additionally, we assume a variable length, straight-line, inelastic, uniform density tether and model aerodynamic forces on the tether and kite. The resulting dynamical system which includes both translational and rotational motion results in an under-actuated mechanical system for the translational motion. Using Lyapunov-based controller design, the controllers for the translational and rotational motions are designed independently and which take the form of D and PD type controllers. A baseline simulation that achieves successive power-retraction cycles with net power generation is studied.