Output feedback sliding mode control for the flying height of a pickup head in near-field optical disk drives

An output sliding mode control method to produce a stable flying height for a pickup head in a near-field optical disk drive is presented. When the optical disks have a large amplitude vibration that makes a stable flying height difficult to attain, a piezoelectric bender is used to complement an air bearing at the head/disk interface. Control simulation for an identified model using measured vibration data of an optical disk is performed to demonstrate the robustness of the proposed method.