Dynamics and robust control of a high speed optical pickup

Recently there has been an increasing demand for optical disk drives to hav e higher speed as well as high information density, especially for applicat ions like CD-ROM drives. To this end improvement of their optical pickup st ructure and control is recognized as a very challenging issue. In this pape r, the pickup is first analytically modelled in a plane to describe its cou pled auto-focusing and auto-tracking systems. With its immeasurable paramet ers being estimated based on experimental data, an approximate I-DOF linear model is obtained neglecting the coupling terms. To design the high speed and robust positional servo controller realistic design specifications are addressed, and the H-infinity control method is employed. Finally taking as an example the pickup in a commercial CD-ROM drive, the performance of the designed controller is verified through realtime experiments. (C) 1999 Aca demic Press.