Analysis of Open-loop Characteristics beyond the Nyquist Frequency in Magnetic-Head-Positioning System of HDDs

Abstract

In a magnetic-head-positioning system of hard disk drives (HDDs), it is hard to analyze an effect of mechanical resonances beyond the Nyquist frequency after the HDDs were assembled. However, unexpected variations of the mechanical resonances often happen in actual HDDs because HDDs are mass-produced products. To solve such a problem, this paper introduces an analysis method of open-loop characteristics beyond the Nyquist frequency for the magnetic-head-positioning system of HDDs. This method enables us to analyze characteristics of the magnetic-head-positioning-control system including intersampling oscillations by using measurable open-loop characteristics. To show a validity of the proposed method, this study demonstrated simulation analyses on the magnetic-headpositioning-control system of the HDD. Simulation results show that proposed open-loop characteristics are good approximated solutions.