Sliding mode control of a point absorber wave energy converter*

This paper presents a novel control strategy for the Coerbuoy1 point absorber wave energy converter (PAWEC) using a sliding mode controller (SMC) designed to maximize energy extraction while ensuring robustness against system uncertainties, including variations in model parameters and extreme sea states. The controller operates on a simplified second-order model that avoids the need for explicitly modeling complex radiation forces, distinguishing it from conventional approaches. Instead, radiation, viscous, and excitation forces are lumped into a single unknown input, estimated online using an observer. This reduction in model complexity enables efficient control design while maintaining performance and robustness. Simulation results in MATLAB/Simulink demonstrate that the proposed SMC significantly enhances energy extraction compared to baseline resistive loading and reactive controllers. Furthermore, the SMC proves robust under model uncertainties, consistently achieving positive energy extraction, unlike other non-robust methods that may lead to negative energy yields. The proposed approach is scalable to more complex wave energy converters and offers a practical solution for real-world applications