Magnetically suspended flywheel in gimbal mount – Nonlinear modelling and simulation

Flywheel energy storage systems (FESSs) with active and passive magnetic bearings are generating interest due to their increasing energy-storing potential caused by advances in motor, bearing and fibre-composite technology. Magnetically suspended FESS are used commercially on static foundations while vehicle applications pose challenges due to manoeuvring, impacts, and other outer perturbations and have thus only seen successful experimental application in a few research projects where the FESS has been mounted in a passive gimbal to avoid gyroscopic forces. Although experimentally implemented, a mathematical model is still missing that determines motions and forces when the FESS is suspended in magnetic bearings, gimbal-mounted, and subject to outer perturbations. This work thoroughly describes how to set up a mathematical model that couples the multi-body dynamics of a flywheel rotor, housing, and gimbal-mount with the magnetic forces of the bearings. The model is used to simulate the behaviour of a FESS with and without gimbal and subject to various perturbations. The results demonstrate how the gimbal mount effectively removes gyroscopic forces but introduces other potential challenges such as large rotor and housing displacements due to dynamical interactions between the rotor, active magnetic bearings, housing, and gimbal.