Precise feedback linearization in EMS systems based on a disturbance observer

Electromagnetic suspension(EMS)systems are unstable open-loop,strongly nonlinear systems.The suspension accuracy of EMS systems for machine tools is improved by integrating the feedback linearization method with a disturbance observer(DOB)to precisely linearize the EMS system.The feedback linearization error is analyzed and modeled in this paper.The DOB is then designed to compensate for the feedback linearization error.This study indicates that the DOB effectively compensates for the feedback linearization error to give precise linearization of EMS systems.Tests illustrate that the EMS feed system gives precise linearization and the platform suspension accuracy is greatly improved to micron scale accuracy.