DISC DRIVE APPARATUS WITH NON-LINEAR OBSERVER

摘要

An optical disc drive apparatus (1) comprises: a read/write element (34) to be positioned with respect to the disc (2), and a detector (35) for generating a read signal (SR); actuator means (50) for controlling the positioning of said read/write element. A control circuit (90) receives said read signal and generates an actuator control signal (SCR), the control circuit having at least one variable gain (?). Said control circuit, actuator means, read/write element, and detector define a control loop (100) having a critical frequency (cocp). A non- linear state estimator (350) is used to selectively set said gain (?) to a first value for signal components having a frequency in a predefined range corresponding to said critical frequency (COCP) and to a second value for signal components having a frequency outside said range, said first value being lower than said second value.