Tae-yeon Hwang

Life Cycle Assessment Study of Color Computer Monitor

The environmental performance of a color computer monitor is investigated by implementing a Life Cycle Assessment. The goal of this study is to collect LCI data of foreground systems, to identify hot spots, and to introduce life cycle thinking at the product design stage. Secondary data are used in the background system, and site-specific data are collected in the foreground system.Results show that the use phase is the most contributing phase. The operating mode and the energy saving mode during the overall use phase contribute to the total by 59% and by 9.9%, respectively. In the production phase, the cathode ray tube assembly process and the printed circuit board assembly process are the most contributing processes. The sensitivity analysis on the use pattern scenario shows that the contribution ratio of the use phase ranges from 32% to 84%. Even in the home use case, which is the best case scenario, the use phase is one of the most contributing processes to the environmental performance of the color computer monitor. There is no significant difference in the choice of the impact assessment methodologies for identifying the improvement opportunities.For the external use of Life Cycle Assessment in a short-run product for the market, it is recommended that Life Cycle Assessment should be carried out in parallel with the product design stage. It is also necessary to have a pre-existing, in-house database for a product group in order to accelerate life cycle procedures.

VCM design to improve dynamic performance of an actuator in a disk drive

PES design margin of current hard disk drive becomes getting smaller as track density of high-capacity disk drives increases. In the present work, a new actuator design concept is introduced for reducing one of the actuator vibration modes so called a butterfly mode that normally limits expansion of servo bandwidth. The new actuator has single coil with four sections having respective particular directions. By adjusting the length and direction of the sections of the VCM coil, the forces perpendicular to track seeking direction can be balanced with each other, and then the butterfly mode is not excited by the resultant force of VCM. Contribution of the proposed actuator design for the PES management is verified by numerical simulations. As a result, the servo bandwidth is to be increased so that PES can be decreased due to improved dynamics of the proposed method.

The acoustic noise characteristics of HDD due to the structural excitation of spindle motor

HDD structure is excited by the dynamic motion of disk-spindle motor components. Those excitations which are generated from stator, magnet rotor, bearings and disks, are transmitted through motor spindle and flange to HDD cover and base. The operational deflection shape measurement can show the structural elicitation patterns at the most influential frequency of the acoustic noise level. One of those components is the axial excitation along spindle, and the other is the local orbital excitation at the contact area of motor flange and base. In order to make a reduction of those structural transmission excitations, the structure of spindle motor should be modified to the direction of reinforcement at transmission path. Some excitation of spindle motor component carrying out essential function is unavoidable. So it is the efficient may of HDD noise improvement to control the structural transmission of excitation.

Identification of shock characteristics in hard disk drive by using time-frequency signal processing technique

A transient signal processing technique using Wigner distribution (WD) is applied to identify the dynamic characteristics when a disk drive system is subject to external shock vibration. It is shown that the smoothed WD technique essentially reveals the propagating characteristics of shock vibration on the specified position of disk drive system as well as head-slap and lift-off phenomena. A parametric investigation for the shock spectrum of suspension is also presented to provide a useful guideline for the shock-resistant disk drive design.

Noise source identification of hard disk drive using sound intensity and its control

Sound intensity technique and ODS (Operational Deflection Shape) technique are applied to identify the acoustic noise source of a hard disk drive system. The sound intensity is used to visualize the exact locations of noise sources, and the ODS to visualize the vibration pattern and to obtain the dynamic characteristics of the noise sources. Based on the visual information on the noise source location and its dynamic characteristic, the optimum structural modification and sound absorption are designed to modify the dynamics of the acoustic noise and to suppress the acoustic radiation power from the disk drive system.