Topology optimization of actuator arms in hard disk drives for reducing bending resonance-induced off-tracks

Abstract

The objective of this work is to find an optimal actuator arm configuration in hard disk drives (HDD's) for sufficiently small arm bending-induced off-track error by maximizing the fundamental eigenfrequency of arm bending modes subject to a constraint on the mass moment of inertia of arms. By applying the topology optimization method for the purpose, an arm configuration having two balancing holes instead of a single balancing hole in conventional designs was obtained. It is numerically shown that an optimized arm configuration substantially increases the arm bending resonant frequency with little change in the mass moment of inertia of arms in comparison with conventional designs having a single balancing hole. Finally, the performance of an optimized actuator arm is verified by showing that the eigenfrequencies associated with arm bending modes are increased by about 100 Hz and the off-track error by measuring the position error signal (PES) from actual sample drives can be reduced by as much as 25%.