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.
I will have more information on the controller design and experimental
results here shortly.