Track following control design for ODDs by employing repetitive two-degree-of-freedom control scheme

Radial track following of an optical disk drive (ODD) servomechanism is severely exposed to periodic disturbances induced by eccentric rotation of the disc. Such disturbances cause the tracking errors of a periodic nature and can be effectively rejected by employing a repetitive controller. In this paper, we propose a repetitive 2DOF control scheme for an ODD track-following servo system with uncertain plant parameters. The proposed repetitive controller is designed on the basis of the frequency domain analysis of the linear interval system and installed as a plug-in module in an existing track following servo system whose feedback compensator is designed independently of the repetitive controller. Simulative and experimental results showed that the proposed control scheme enables a significant improvement of the tracking accuracy of the radial servomechanism.