A high data transfer rate is constantly demanded for optical disk drives. One of the solutions is to rotate a disk at a high rotational speed. We need a stable rotation of optical disks and a robust servo control to realize high-rotation-speed optical disk drives. It is difficult to rotate conventional polycarbonate optical disks, whose thickness is 1.2 mm, over 15000 rpm without vibrations. We measured and analyzed disk vibrations at high rotational speeds, and found a condition for suppressing the vibrations of the disks. We confirmed the stable rotation without vibrations up to 20000 rpm under this condition. We also conducted an experiment on tracking servo control at high rotational speeds. We used a double-boosted high-gain servo controller to suppress disturbances at high rotational speeds, and confirmed the robust servo control at 21000 rpm with this controller. #

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