A Study on a Reduced-Order Disturbance Observer Controller for Nonlinear Electro-magnetic Suspension systems

In this paper, we study on a reduced-order disturbance observer (DOB) controller for nonlinear Electro-magnetic suspension (EMS) systems with mass uncertainty. Since it is rather complicated to design a nonlinear DOB controller for nonlinear systems, this paper aims to design a linear DOB controller for nonlinear systems. Since noise suppression of reduced-order DOB controller is superior to that of standard DOB controller, this paper focuses on the reduced-order DOB controller. Using the case study of nonlinear EMS systems, it is found that the followings should be carefully chosen for the design of reduced-order DOB controller: High-frequency gain of the nominal model, pole and zero location of the nominal model, selection of Q-filter, and the choice of primary controller. © 2022 Korean Institute of Electrical Engineers. All rights reserved.