Dynamic analysis of a wave energy storage gyroscope on active magnetic bearings

ISWEC (Inertial Sea Wave Energy Converter) is a device which converts wave energy into electricity exploiting the gyroscopic moment of a spinning flywheel. This thesis is part of the design of a gyroscopic unit in which the rotor levitates on a magnetic suspension to reduce the friction losses and hence improve the system efficiency. The work analyzes how to ensure the system mechanical integrity not only in normal operating conditions but also in case of magnetic suspension failure or overload. To achieve this aim, rotor natural frequencies and the corresponding vibration modes are obtained by FEM numerical simulations. It is verified that the rotor does not reach any critical speeds during normal operating conditions. In order to avoid mechanical components damage in case of magnetic suspension malfunction, the gyroscope touches a set of back-up bearings. The flywheel drop is studied using FEM time-domain analysis for different operating conditions (rotor subjected to weight force, to spinning, to gyroscopic torque, to radial force, to precession motion and to dynamic unbalance). On the basis of the computed results, the rolling bearings, which are the main components of the back-up system, are properly dimensioned. Finally, a possible mounting solution is developed for the designed bearings.