Optimal arm configuration to reduce arm bending resonance-induced off-track in a hard disk drive

In order to reduce the off-track due to the arm bending mode, whose effect is considerable in a high capacity drive, an arm configuration with maximum arm bending stiffness should be considered. The objective of this work is to find the optimal arm configuration that maximizes the arm bending stiffness subject to the constraint imposed on the moment of inertia of the arm. Herein, the problem of finding the optimal arm configuration maximizing the arm bending stiffness is formulated as a topology optimization for eigenvalue maximization problem. By applying this method, an arm configuration having two balance holes instead of a single balance hole was obtained. Finally, the efficacy of the optimized arm is verified by measuring the position error signal (PES) of actual sample drives; when the optimized arm was used, the PES was reduced by 25%.