with success. A previous study and comparison of the
existing methods in the same field was made by Sievers
and von Flotow (1992), which included two of the control
laws considered also herein. The approach of this
study is different from the previous one, with the
emphasis being in the robustness and frequency
domain performance analysis of the methods. These
are important properties for any industrial application
of a control law today. The study also covers some of
the recent advances in the field. It should be emphasized
that the number of existing methods is vast and it
is impossible to cover anything but a rather narrow part