This paper is to document major research results from the authors' recent experimental and numerical studies of spindle motor vibration of 0.85-in. hard disk drives (HDD). Experimental studies indicate that spindle vibration of 0.85-in. HDD is very sensitive to its supporting fixture design. A poorly designed fixture can lead to spurious modes that do not reflect true vibration characteristics of the HDD. Experimental measurements also indicate that vibration of 0.85-in. HDD primarily consists of base plate vibration as opposed to rocking motion of the spinning disk pack, also known as (0,1) unbalanced modes, which dominates vibration of 3.5-in. HDD. For the numerical studies, simulation results from a component modes synthesis agree very well with the experimental measurements. Moreover, the dominance of the base plate vibration observed in the experimental studies results from the fact that the lowest natural frequency of the base plate is significantly smaller than that of the spinning disk in 0.85-in. HDD. Finally, a parametric study is conducted to identify critical parameters that significantly affect the spindle vibration of 0.85-in. HDD. Results of the parametric study indicate that rigidity of the base plate and locations of the radial bearing are the most critical parameters.
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