Preliminary experimental assessment of second-order sliding mode control for wave energy conversion systems

Wave energy converters (WECs) inherently necessitate appropriate control technology to operate at optimal efficiency. A particularly well-established family of WEC controllers is based upon a composite structure, where an optimal velocity reference is generated via direct optimal control procedures, followed by a suitable tracking control strategy. Recently, second-order sliding mode (SOSM) control has been shown to be a promising technique for the latter reference tracking problem in WEC systems, being able to achieve robust performance with finite-time convergence. Motivated by the potential of SOSM control within the wave energy field, this paper provides an experimental assessment of SOSM in a tailored hardware-in-the-loop system, located within the facilities of the Centre for Ocean Energy Research, Ireland. We show that the proposed controller is able to achieve robust reference tracking in a variety of wave conditions, consistently maximising energy absorption at virtually the same level of performance obtained in simulation, hence being an ideal candidate for WEC applications.