Control co-design optimization of nonlinear wave energy converters

• Published in: Ocean engineering 2024-07, Vol.304, p.117827, Article 117827
• Main Authors: Abdulkadir, Habeebullah, Abdelkhalik, Ossama
• Format: Article
• Language: English
• Subjects: Control co-design; Froude–Krylov forces; Nonlinear WEC; Optimal control; Wave energy converter
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2024.117827

This paper presents a study in which both the control and the shape of a Wave Energy Converter (WEC) are optimized simultaneously. A heaving point absorber WEC is assumed. To optimize the shape of the WEC’s buoy, nonlinear hydrodynamics need to be evaluated. One main contribution of this paper is the integration of nonlinear hydrodynamics and nonlinear control during the optimization of the WEC’s buoy shape. This approach is referred to as Control Co-Design (CCD). In this work, we present a control co-designed nonlinear heaving point absorber WEC that leverages the nonlinear dynamic, static Froude–Krylov (FK) forces to maximize power extraction. The nonlinear FK forces are approximated using a variation of the algebraic solution; the hydrodynamic forces of the body are computed using an analytic formulation leveraging the methods of eigenfunction expansion and separation of variables. The nonlinear geometry of the buoy is modeled as a series of inclined panels; the inclination angles are optimized to arrive at the optimal shape. The performance of the optimized shape is compared to that of a nonlinear spherical WEC. It is found that an average of 20% improvement is achieved by the optimized geometry over the spherical device. •The highlight of the research is that, generally, the dynamic equation of WECs are used to formulate innovative control methods to ensure the efficient operation of the devices.•The design of optimal control often comes at the last stage of the design process, after the mechanical, electrical, and other subsystems are completely defined.•During the earlier stages, simplified controls are employed for designing the subsystems, which may not match the final system’s control requirements.•This study introduces an approach to the WEC device design process that integrates the ultimate control method and all other pertinent engineering considerations from the outset.