Direct force control of AMB-rotor system

Abstract

Active magnetic bearing (AMB) is a bearing type that supports a rotor with a magnetic force without any physical contact. AMBs require continuous control as an AMB-rotor system is unstable. Various control principles could be used in the AMB-rotor system: feedback control, cascaded control with different inner control loops, and model-based control. In control of electrical motors, the DTC principle and the flux estimation provide very fast control responses by power switches direct control. In AMB control systems the corresponding principle can be adapted for direct control of forces without a need for cascaded control loops. In this thesis, the feedback control and the cascaded control are studied, the direct force control (DFC) principle is designed. The rotor is considered to be rigid and the 2 degree of freedom AMB is studied. The comparison of the control principles responses is analyzed. The designed DFC principle provides better dynamics than the conventional control principles.