Project - Control Techniques for a Single Degree-of-Freedom Magnetic Suspension

Control Techniques for a Single Degree-of-Freedom Magnetic Suspension


Pradeep Subrahmanyan


Integrated Solutions Inc.

This project involves the design and implementation of various linear and nonlinear control schemes for a single DOF magnetic suspension. Plant uncertainty is introduced on purpose and countered using Robust and Adaptive techniques. Robust adaptive control is found to give the best results.

Control techniques for a single DOF magnetic suspension

Research in the precision motion control lab is targetted towards obtaining very rapid and precise positioning such as those required in stepper stages for Photolithography during semiconductor manufacture. A six dof stage has been built by Mark Williams for this very purpose. We use magnetic bearings to levitate the stage and allow for fine positioning and linear motors to provide the long axes of travel. The current approach to controlling the stage position is using feedback linearization. The six dof stage is a multi-variable control problem with coupling in between the various axes of motion. So, a simple single dof stage was built where a mass is levitated in between two E-core actuators which are standard in our lab. 

My goal is to obtain faster responses and very rapid settling times. I am also studying the effects of parameters uncertainty. Control techniques that I have implemented on the single DOF stage include sliding mode control, robust adaptive control. Both techniques lead to higher bandwidths than those currently obtained. I am currently studying stiffness properties of the various control techniques. 

Simple single DOF stage.Single DOF stage.