Robust identification and control for sea wave energy conversion

This thesis aims at designing a control-oriented model for the Inertial Sea Wave Energy Converter (ISWEC) system. The ISWEC system consists of a floating device composed by a hull which hosts a gyroscope system whose motion is induced by the pitching oscillations of the hull floating on the sea surface. Energy extraction is obtained by damping the gyroscope precession motion through an electrical Power Take Off (PTO) unit, which is implemented by an electric motor able to exert the torque intended for damping such a motion. The shaft, about which the precession motion takes place, is mechanically connected to the PTO shaft. In this thesis, a procedure based on set-membership identification techniques is proposed for building a multi-inputs linear model of the system from input-output experimental data. Since set-membership techniques allow the user to quantify the uncertainty of the identified model, the obtained system description can be profitably exploited to design a robust controller aimed at maximizing the energy conversion. Based on the identified control-oriented model, a preliminary study has been conducted in order to investigate the possibility of formulating the problem of maximizing the energy conversion in terms of robust closed loop control.