Modeling, Control Design, and Combined Plant/Controller Optimization for an Energy-Harvesting Tethered Wing

Abstract

This paper presents a combined plant and controller performance analysis and optimization for a tethered rigid wing with on-board rotors, flying in crosswind patterns. Specifically, we use a 3-D model of the tethered wing to assess the influence of critical design parameters on both quality of flight and energy-generation performance, as quantified by the “Loyd Factor,” which compares energy-generation performance to a theoretical upper bound. Recognizing that the optimal performance occurs when the system is on the verge of closed-loop instability, we demonstrate how a combined optimization of the plant and controller can aid in further pushing the boundaries of the system. The results of this combined optimization show a critical tradeoff between robustness and energy-generation performance. We demonstrate that attaining maximum energy-generation performance requires operating on the verge of closed-loop instability and also results in a reduced set of parameters for which the system is stable.