Disk Drive

The most significant trend in magnetic disk drives is that track density and storage capacity are increasing rapidly over years. This trend has led to the need for improved performance of the head-positioning servo system. Dual-stage actuators and instrumented suspensions have thus been proposed as solutions to achieving the objective, in which the first proposal is to increase the servo bandwidth and the second one is to obtain airflow excited suspension vibration information for active control. Intensive researches have been conducted in our research group, which can be classified into three categories: Fabrication of MEMS microactuator, Development of instrumented suspensions, and servo design and vibration control of dual-stage systems.

Servo design part:

1. Active suppression and compensation of airflow excited suspension vibrations . The suspension is instrumented to detect airflow excited suspension vibrations. Adaptive control can be applied to the microactuator to generate additional motion to actively compensate for suspension vibrations and position the read/write head precisely.
2. Multi-objective and multi-rate servo design of multi-sensing dual-stage systems . In the dual-stage system, all other signals can be sampled at a higher rate than that of the position error signal, in order to achieve better performance. In addition to better tracking performance, stability robustness is also desired considering plant uncertain dynamics and parameter variations. Multi-objective and multi-rate servo design is thus a natural way to fully exploit the potential of the multi-sensing dual-stage system.

Students:
Xinghui Huang , Kenn Oldham, Stanley Kon, Sarah Felix, Alain Chahwan, Ryozo Nagamune

Recent Publications:
Oldham K, Kon S, Horowitz R. Fabrication and optimal strain sensor placement in an instrumented disk drive suspension for vibration suppression. Proceedings of the 2004 American Control Conference. IEEE. Part vol.2, 2004, pp.1855-61 vol.2. Piscataway, NJ, USA.

Xinghui Huang, Nagamune R, Horowitz R, Yunfeng Li. Design and analysis of a dual-stage disk drive servo system using an instrumented suspension. Proceedings of the 2004 American Control Conference. IEEE. Part vol.1, 2004, pp.535-40 vol.1. Piscataway, NJ, USA.

Ohno K, Horowitz R. A variable structure multi-rate state estimator and its application to seeking control of HDDs. Transactions of the Society of Instrument and Control Engineers, vol.39, no.7, July 2003, pp.662-9. Publisher: Soc. Instrum. & Control Eng, Japan.

Yunfeng Li, Horowitz R, Evans R. Vibration control of a PZT actuated suspension dual-stage servo system using a PZT sensor. IEEE Transactions on Magnetics, vol.39, no.2, March 2003, pp.932-7. Publisher: IEEE, USA.

Yunfeng Li, Horowitz R. Active vibration control of a PZT actuated suspension in hard disk drives. Proceedings of the 2002 American Control Conference. American Automatic Control Council. Part vol.2, 2002, pp.1366-71 vol.2. Danvers, MA, USA.

Tsung-Lin Chen, Yunfeng Li, Oldham K, Horowitz R. MEMS applications in computer disk drive dual-stage servo systems. Journal of the Society of Instrument & Control Engineers, vol.41, no.6, June 2002, pp.412-20. Publisher: Soc. Instrum. & Control Eng, Japan.