ANALYSIS AND CONTROL OF THE ACTUATOR ROCKING MODE IN A HARD DISK DRIVE

The recording head in a hard disk drive (HDD) is supported by an actuator assembly which is being controlled by a servo system. Structural resonance modes in the actuator impact the performance of the servo system. The actuator rocking mode has been identified as a major contributor to seek settling and hence, affects the servo stability. This paper presents the effect of actuator structure, skew angle and magnetic flux on the actuator rocking mode. A model to show the effect of the actuator rocking mode on the head motion was constructed to study the interaction with the control plant. The analysis was then verified with experiments. Excellent correlation was established between the experimental result and the theoretical model. Although the rocking mode cannot be eliminated, methods to suppress it are proposed based on the findings.