PI Sliding Mode Control for Active Magnetic Bearings in Flywheel

Abstract

This paper proposes the PI sliding mode control approach in order to control the nonlinear multiple-input-multiple-output active magnetic bearing system in flywheel. A nonlinear model of a one degree of freedom (DOF) active magnetic bearing system in flywheel obtained using Lagrange’s equation is proposed. In this model, the current in each coil is treated as a state variable and the control input is the voltage applied to each coil, this approach offers more advantages than current control input approach. The proportional and integral switching surface is constructed for active magnetic bearing system to improve system dynamic performance in reaching intervals. The robust controller is proposed by the reaching law method to assure that the rotor stays close at the desired displacement even when disturbance and dynamic effect of rotating are taken into considering.