Adaptive inverse control for the pickup head flying height of near-field optical disk drives

Near-field optical disk drives represent a promising technique for optical data recording to achieve an even larger storage density and capacity than DVD-ROM and Blu-ray disk drives. To realize near-field optics, unlike conventional optical disk drives, a flying pickup head is required. In this study, the pickup head consists of a suspension arm, a slider and a bimorph piezoelectric bender between the suspension arm and the slider. The dynamic model of the pickup head is identified using measurement, but the whole dynamics including both pickup head and interface dynamics between the disk and slider is unmodeled. Adaptive inverse control of robustness is developed to track the vibratory deformation of rotating optical disks, so that the flying height of a pickup head can remain stable in the presence of modeling error. Experimental results demonstrate that using the proposed method the pickup head can not only track disk deformation but also maintain the flying height.