Control System For Constrained Wave-Powered Oceanographic Buoys

Shangyan Zou,Ossama Abdelkhalik

doi:10.36688/imej.2.51-61

Abstract

Wave energy can be used to power oceanographic buoys. A new switching control strategy is developed in this paper for a two-body heaving wave energy converter that is composed of a floating cylinder and two rigidly connected submerged hemispheres. This control strategy is designed to prevent excessive displacement of the floating buoy that may occur due to the actuator force. This control strategy switches the control between a multi-resonant controller and a nonlinear damping controller, depending on the state of the system, to account for displacement constraints. This control strategy is developed using a one-degree-of-freedom dynamic model for the relative motion of the two bodies. Estimation of the relative motion, needed for feedback control, is carried out using a Kalman filter. Numerical simulations are conducted to select the proper mooring stiffness. The controller is tested with stochastic models of irregular waves in this paper. The performance of the controller with different sea states is discussed. Annual power production using this control strategy is presented based on real data in 2015 published by Martha's Vineyard Coastal Observatory.

Highlights

Ocean waves contain abundant energy and it is considered to be reliable and have high power density [1]
As indicated in the figure, the power extraction of the two-body system is stable around 150W when the mooring stiffness is greater than 3 × 104N/m
The maximum relative motion shows a decreasing trend when the mooring stiffness is increasing from 3×104N/m to 3.63×106N/m

Summary

Introduction

Ocean waves contain abundant energy and it is considered to be reliable and have high power density [1]. Wave energy converters can be categorized as: oscillating water column [5], overtopping converters [1], and point absorbers which are adopted in this paper. Research on two-body systems (a buoy and a moving reference) received a great deal of interest over the past decades. Since the shape of the submerged body has a significant impact on the performance of Manuscript received 10 Oct 2019; revised 13 May; accepted 24 Aug; published 7 Sep, 2020.

Results

Discussion

Conclusion