A Study on an Application of Disturbance Observer Controller to Nonlinear Electro-magnetic Suspension Systems

Abstract

Disturbance observer (DOB) controllers have been widely employed since they have the powerful ability of disturbance attenuation and uncertainty compensation. However, it is difficult to design a nonlinear DOB controller for nonlinear plants. This paper studies the robust stability of nonlinear plants controlled by linear DOB controllers. Using the case study of an electro-magnetic suspension (EMS) system, we studied the effects of nominal model selection on the robust stability of the linear DOB controller. We discuss two effects on robust stability: 1) The high-frequency gain of the nominal model and 2) The pole location of the nominal model.