COUPLING-ENHANCED CONTROL FOR OPTICAL DISK-DRIVES

The positioning system of optical disk drives is becoming more and mor e important with the increase in the track density and rotation speed. Dual-stage actuators are used in the positioning servo system of opti cal disk drives. A coupling-enhanced design is intrudued for the track ing servo systems without a position sensor to detect the relative dis placement between the two stages. By enhancing the coupling between th e two stages, the first stage can obtain equivalent feedback informati on from the second stage. The tracking servo system can be designed as one servo loop, and only one controller is needed to control a dual-s tage actuator The multivariable problem can be treated as a single-var iable problem and the design is simpler.