Novel repulsive magnetic bearing flywheel system with composite adaptive control

Here, a novel flywheel structure is proposed with passive permanent magnet (PM) bearings in the radial and axial directions and an active magnetic bearing (AMB) in the axial direction. In the proposed structure, passive magnetic bearings do not provide a stable magnetic levitation in all directions, but it is possible to maintain the dynamic stability of the flywheel by using AMB in the axial direction. In the proposed bearing structure, radial repulsive magnetic bearings (RMBs) reduce the power consumption with less complexity in the bearing structure but impose disturbance forces that deteriorate the stability of the actively controlled flywheel system. A complete model of the flywheel system is derived and transformed for a control design. A Lyapunov-based composite adaptive feedback control is designed for maintaining the stability under disturbances and a close convergence to the desired trajectory with fast parameter estimation. The performance of the composite adaptive control was experimentally verified for different cases using the RMB flywheel system. Additionally, a PID control was experimentally verified to demonstrate the usefulness of parameter estimation.