Abstract:In this paper, contributions of airborne and structure-borne vibrations to head positioning error of a HDD at high frequencies up to 10 kHz were investigated. The L8 array test was conducted with four two-level factors about vibration isolation between fans and HDDs: A) Removing bracket, B) Attaching foam on backplane, C) Filling foam in the next column, and D) Filling foam in the upper and lower slots. The test results showed there were less interaction between airborne and structure-borne vibration. Then, we… Show more
“…The external vibrations were caused by either server fans or adjacent HDDs in the data server. The vibration of the server rack, shown in Figure 4(c), was measured (Eguchi et al, 2017). The signals of the acceleration sensors were sent through the amplifier to an oscilloscope, and the measured data were recorded by a PC, shown in Figure 4(d).Figure 3.Amplitude spectra of internal vibration and external vibration.Figure 4.Overview of the experimental system.…”
Section: Characteristics Of Control Object In Dual-stage Actuator Systemmentioning
Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.
“…The external vibrations were caused by either server fans or adjacent HDDs in the data server. The vibration of the server rack, shown in Figure 4(c), was measured (Eguchi et al, 2017). The signals of the acceleration sensors were sent through the amplifier to an oscilloscope, and the measured data were recorded by a PC, shown in Figure 4(d).Figure 3.Amplitude spectra of internal vibration and external vibration.Figure 4.Overview of the experimental system.…”
Section: Characteristics Of Control Object In Dual-stage Actuator Systemmentioning
Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.
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