Design and Evaluation of State and Disturbance Observers for a Multivariable Magnetic Levitation System

For inherently unstable magnetic levitation (maglev) systems, state observation is required for feedback control, and disturbance estimation is needed to compensate for unknown disturbances. Previous designs for simultaneously observing state and disturbance can lead to aggressive disturbance compensation and an unstable levitation. Aiming at these problems, this paper presents a state and disturbance observer that has a cascade structure for a maglev system. The proposed design allows the dynamics of disturbance observation to be separately tuned from those of state observation, avoiding aggressive disturbance compensation and enabling a stable levitation of a maglev system. In this paper, the proposed and previous state and disturbance observers are designed and realized for a maglev system that features wide ranges of translation and rotation motions in five directions. Comparative studies are reported in this paper, and experimental results show feasibility and efficiency of the proposed scheme.