Takehiko Eguchi

Simulation of Position Error Signal Degradation Due to Operational Vibration for Hard Disk Drives in a Storage Server Box

A method for simulating position error signal (PES) degradation due to operational vibration of hard disk drives in a storage server box is presented. The drive model used was based on the component mode synthesis method; the model of the operational vibration of the box based on the frequency transfer function method was newly added. The results of simulations and experiments using a network attached storage box with six SCSI drives showed close agreement. Moreover, component analysis of the computed PES degradation indicated that the rocking vibration of the disk/spindle assembly was the dominant cause of the PES degradation.

Aerodynamic Damping on Vibration of Rotating Disks and Effects of Shroud and Top Cover

Aerodynamic damping on vibration of rotating disks surrounded by a shroud was experimentally investigated. Hammer tests were conducted in a vacuum and in air, and a curve-fit technique was used to estimate natural frequencies and modal damping ratios of disk modes precisely from measured frequency responses. The experimental results revealed that aerodynamic damping is dominant rather than structural damping and independent of the amplitude of the disk vibration. The relationships of aerodynamic damping with disk-to-shroud and disk-to-cover gaps were also investigated. When the disk-to-shroud gap is narrower than 0.3 mm, the damping ratios increase rapidly as the disk-to-shroud gap narrows and the rate of increase depends on the disk mode. For the (0, 0) mode, the damping ratio is inversely proportional to the cube of the disk-to-shroud gap, which agrees with our previous theoretical prediction. In contrast, when the disk-to-shroud gap is wider than 1 mm, the rate of increase is slow and varies insignificantly with disk mode.

A Novel HDD “Component-Level” Operational-Shock Measurement Method

This paper describes and validates a novel experimental method for measuring the operational-shock performance of hard-disk drives, which allows for easy replacement of mechanical components. By nonintrusively instrumenting the hard-disk drive with the ability to measure the dynamic capacitance change between the slider and disk, we are able to obtain slider air-bearing dynamics, slider lift-off, and slider-disk contact during operational-shock events and ultimately failure. We also discuss a complex nonlinear model for accurate simulation of operational-shock events. The experimental data is compared to drive-level data and modeling results for various combinations of mechanical components showing excellent correlation. From this method, we are able to quickly evaluate operational-shock performance of various components on a hard-disk drive level

Simulation of PES degradation due to operational vibration for hard disk drives in storage server box

This paper presents a method to simulate position error signal (PES) degradation due to operational vibration of hard disk drives in a storage server box. The drive model is based on a component-mode synthesis method and the operational vibration model is newly added in the model. Comparison between simulations and experiments using a network attached storage (NAS) box with six SCSI drives showed good agreement. Moreover, component analysis of the computed PES degradation indicated that the rocking vibration of the rotating part caused by the rotational vibration about the axis along the short side of the drive was dominant.