ISWEC control tuning: lessons learned

ISWEC (Inertial Sea Wave Energy Converter) is a floating device that exploits the gyroscopic reactions provided by a spinning flywheel to extract power from sea waves. The first sea demonstrator has been deployed in August 2015 at the Island of Pantelleria, Italy. Starting from experience gained working in the real sea environment, some observations about the control are presented. The control of the device aims to exploit all the available control parameters in order to maximize power generation. At first the tuning of PTO control law is analysed and then the additional control degree provided by the gyro speed is considered too. A new developed control technique is briefly introduced. It consists of an application of a standard linear quadratic regulator coupled with a properly designed nonlinear static term. A comparison of previous and new control techniques is presented, proving that the new control is able to insure almost the same power absorption performances while reducing the number of control parameters to be tuned.