Head positioning control system design based on dynamic characteristic of rolling friction in HDDs

This paper describe a head positioning controller in HDDs based on a dynamic characteristic of rolling friction. In the control system in HDDs, the head assembly was influenced the effect of several disturbances, e.g, RRO, flutter vibration, force disturbance, and so on. At the force disturbance, it caused by wind force, external shock, tension force of Flexible Printed Circuit, and rolling friction around pivot bearing. In these force disturbance, the influence of the rolling friction is large at positioning in minute area. Therefore, controlling the rolling friction is important at short span seeking motion for the high performance trajectory. In this paper, we present a measuring method for the dynamic rolling friction that considering the inertia force of magnetic head. And we propose a 2 DOF controller design to suppress the effect of the dynamic rolling friction. The effects of the proposal method and controller performance are verified by experimental results.