Modeling and control of a six degree-of-freedom magnetic/fluidic motion control stage. - Stephen J. Ludwick; David L. Trumper; Michael L. Holmes (IEEE Trans. Control. Syst. Technol., 1996)

Nonlinear Control Algorithm for Improving Settling Time in Systems With Friction. - Brian A. Bucci; Daniel G. Cole; Stephen J. Ludwick; Jeffrey S. Vipperman (IEEE Trans. Control. Syst. Technol., 2013)