Quasi mixed /spl Hscr//sub 2///spl Hscr//sub /spl infin// controller for a high precision positioning device

A new design method of robust controllers, named quasi mixed /spl Hscr//sub 2///spl Hscr//sub /spl infin// (QM/spl Hscr//sub 2///spl Hscr//sub /spl infin//) controller is proposed. The QM/spl Hscr//sub 2///spl Hscr//sub /spl infin// controller is designed using the linear matrix inequality approach based on a combination between the /spl Hscr//sub 2/-norm and /spl Hscr//sub /spl infin//-norm criteria. The term quasi implies that it does not require total separation between the /spl Hscr//sub 2/-norm of a certain transfer function matrix and the /spl Hscr//sub /spl infin//-norm of the other transfer function matrix under consideration. This makes the method simpler compared to other approaches. In this study, the design method is applied to a high precision positioning device. Its good points and performance limitation are analyzed through computer simulation.