No abstract

In head-positioning systems of hard disk drives, the negative effects of a primary resonant mode are serious problems for positioning accuracy. In order to improve positioning accuracy, the primary resonant frequency should be increased because the effects of the primary resonant mode limit the servo bandwidth. An integrated design of a controller and structure for the head positioning system was developed to solve this problem. We showed that the servo bandwidth is limited not only by the peak frequency of the primary resonance but are also its residue. The proposed method decreases the negative impact of the primary resonant mode through a newly designed modal shape, and increases the servo bandwidth without the addition of any sensors or actuators. The effectiveness of this method was verified by designing an actual servo control system and experimentally measuring its bandwidth, demonstrating that the method increases the servo bandwidth without increasing the production cost.

No abstract

To reduce the flow-induced vibration (FIV) of the head stack assembly (HSA) in the hard disk drive (HDD), we experimentally studied the spoiler, which is put between disks. This study was carried out using a laser doppler vibrometer (LDV) to measure the amplitude of the head slider vibration. We also measured the power consumption of the spindle motor.As parameters of the spoiler shape, the thickness and the length were selected. From the experimental result, these parameters effect significantly both the head's vibration and the power consumption. This result suggests that the flow rate reduction with the spoiler causes a reduction of the HSA's FIV, and the energy loss with the spoiler causes an increase of the power consumption.We defined the spoiler's FIV-reducing efficiency as a ratio of the amplitude reduction to the power consumption increase. The length change makes the peak value. This is caused by the fact that the FIV reduction becomes almost constant when the spoiler is longer than the carriage arm length inside disk region, although the spoiler length makes power consumption monotonically large.Index Terms-Flow-induced vibration, hard disk, head stack assembly, spoiler.

With the ,aim of increasing, the track density in a hard disk drive by widening servo bandwidth, the authors have devgleped a new design concept base'd on lowering the major resonance gain in the transfer fundtion of the actuato: A head actuator based on this design concept was constructed and fitted in an actual disk-drive assembly and evaluated. The test results show that the measured servo bandwidth is .wider by rnore 300Hz than that of a typical.ly designed actuaton