Abstract
The fineβseeking control, one of the radial positioning servo functions on the optical disk drives, seeks a limited number of tracks forward or backward. Two properties, noted as controllable seeking velocity and achievable settling, are important issues for fineβseeking performance. Unless these performances are satisfied, the settling down track cannot be guaranteed to be the desired track; hence, additional seeking is required to come forward to the destination track. Owing to the periodic runout effects, the conventional feedback approaches are difficult to achieve stable velocity control and satisfactory settling performance for high spindle speed operation. This paper proposes the extended usage of frequency adaptive control technique (FACT) for active runout suppression on fine seeking. It is shown that the runout effects can be isolated from the servo systems as long as the FACT is applied. A mode switching control approach is then introduced to switch the adaptation between the trackβfollowing and fineβseeking processes. This leads to an efficient compensation for periodic runout, thereby eliminating the direction hysteresis in fine seeking. Experimental results are shown to be effective for the performance on both velocity control and settling behavior after seeking. Copyright Β© 2007 John Wiley & Sons, Ltd.