Bringing airborne wind energy offshore: A hardware-in-the-loop framework for closed-loop wave tank testing

The first documented wave tank testing setup of a floating platform for Airborne Wind Energy Systems (AWES) is presented, featuring a novel hardware-in-the-loop (HIL) experimental methodology for the controlled reproduction of aerodynamic and hydrodynamic interactions. The proposed setup combines a real-time kite simulation with a physical spar platform, subjected to both wave excitation and three-dimensional kite-induced force. The latter is applied by four actuators linked to the platform by tethers. The design of the actuation system and of its control logic is described. The hierarchical control approach includes a real-time, optimization-based allocation technique of the force setpoints to the actuators, to cope with the nonlinearity of the tethers’ geometry, and a force feedback loop at each actuator to track the corresponding setpoint. The experimental results showcase the performance of the actuation system in reproducing at scale the kite forces computed by the real-time simulator coupled to the physical platform. The setup establishes a framework for future experimental investigations of floating AWE systems, supporting numerical model validation, control design, and performance assessment for offshore deployment.