This submission includes three peer-reviewed (under review) papers from the researchers at North Carolina State University presenting control-based techniques to maximize effectiveness of a tethered tidal kite. Below are the abstracts of each file included in the submission.

Cobb TCST - Iterative learning for kite path optimization.pdf This paper presents an iterative learning control-based approach for optimizing the flight path geometry of a tethered MHK system. Tethered MHK systems, which replace the tower and turbine of a conventional system with a tether and a lifting body, capture energy by driving a generator with the tension in the tether. By spooling out tether during the high tension portions of cross-current flight and spooling in during low tension portions, net positive energy is generated over one cycle. Because the net energy generation is sensitive to the shape of the flown path, we employ an iterative learning update law to adapt the path shape from one lap to the next. Additionally, we present a realistic system model, along with lower-level path-following and power take-off (PTO) controllers. We then demonstrate the efficacy of our algorithm on this model in both uniform and realistic flow environments.

Siddiqui ACC - Optimal spooling control of kites in variable flow.pdf This work focuses on the development of an adaptive control strategy that fuses Gaussian process modeling and receding horizon control to ideally manage the tradeoff between exploration (i.e., maintaining an adequate map of the resource) and exploitation (i.e., carrying out a mission, which consists in this work of harvesting the resource). The use of a receding horizon formulation aids in the consideration of limited mobility, which is characteristic of dynamical systems. In this work, we focus on an airborne wind energy (AWE) system as a case study, where the system can vary its elevation angle (tether angle relative to the ground, which trades off higher efficiency with higher-altitude operation) and flight path parameters in order to maximize power output in a wind environment that is changing in space and time. We demonstrate the effectiveness of the proposed approach through a data-driven study on a rigid wing-based AWE system.

Reed ACC - Spatial optimization of kite paths.pdf This paper presents a technique for maximizing the power production of a tethered marine energy-harvesting kite performing cross-current figure-eight flight in a 3D spatiotemporally varying flow environment. To generate a net positive power output, the kite employs a cyclic spooling method, where the kite is spooled out while flying in high-tension crosscurrent figure-eight flight, then spooled in radially towards the base-station under low tension.