Hydrodynamic Control of Wave Energy Devices [Bookshelf]

• Published in: IEEE Control Systems 2018-02, Vol.38 (1), p.135-137
• Main Author: Scruggs, Jeff T.
• Format: Magazinearticle
• Language: English
• Subjects: Control systems; Control theory; Energy conversion; Energy harvesting; Energy technology; Hydrodynamics; Impedance matching; Lower bounds; Objectives; Ocean waves; Real-time systems; Sea measurements; Tracking; Wave power
• ISSN: 1066-033X; 1941-000X
• DOI: 10.1109/MCS.2017.2766324

A control system can be optimized for various fundamentally distinct performance objectives, leading to various canonical design problems such as disturbance rejection and tracking. Most of these can be recast as design problems, where it is desired to make some aspect of the closed-loop system (such as the norm of an input/output channel or mean-square tracking error) as close to zero as possible. However, not all control design objectives fit neatly into this paradigm, and one of the notable exceptions is the problem of harvesting maximal energy from dynamic phenomena. For certain classes of problems (characterized by the passivity of the mapping u " v and the boundedness of the disturbance), such objectives can be shown to have a finite lower bound, resulting in a finite maximum available energy. This fact has been known to control and system theorists for decades and is of particular importance in robustness analysis. However, beyond the obvious connections to the classical concept of “impedance matching,” the idea that this objective is useful as the primary measure of a control system’s performance—a thing to be optimized in closed loop and balanced against other objectives—is a concept that has received considerably less attention. It may, therefore, be surprising to learn that this problem has a rich and decades-long history in the area of ocean wave energy conversion. This book begins with a brief but fascinating overview of this still-evolving history, from its early beginnings in Japan in the 1950s, through its surge of activity in Europe and America during the oil crisis of the 1970s, the rally of global industrial activity in the 1990s, and into the present. The text succeeds at illustrating these various aspects, while also giving the reader a strong appreciation for the history and evolution of the field. One is left with an accurate and compelling snapshot of where the research community is headed and an appreciation for the central role that control theory will play in its future. Although this is not the first text written on wave energy technology, it does focuses primarily on advanced control techniques.