A proximate-time-optimal-control design and its application to a hard disk drive dual-stage actuator system

We propose a compensator-based strategy for design of a track-seeking and track-following control system for a dual-stage servo actuator in hard disk drives. A well-known decoupling structure is employed to disconnect the control of the primary voice coil motor (VCM) actuator from the loop for a sec...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2006-06, Vol.42 (6), p.1708-1715
Main Authors: Hredzak, B., Herrmann, G., Guo, G.
Format: Article
Language:English
Subjects:
Actuators
Bandwidth
Coils
Compensators
Control systems
Cross-disciplinary physics: materials science
rheology
Design engineering
Disk drives
Dual-stage actuator
Exact sciences and technology
Hard disks
magnetic disk drive
Magnetic heads
Magnetism
Materials science
microactuators
motion control
Nonlinearity
Other topics in materials science
Performance enhancement
Physics
Servomechanisms
Servomotors
Strategy
Studies
Tracking loops
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Description
Summary:We propose a compensator-based strategy for design of a track-seeking and track-following control system for a dual-stage servo actuator in hard disk drives. A well-known decoupling structure is employed to disconnect the control of the primary voice coil motor (VCM) actuator from the loop for a secondary high-bandwidth actuator. The compensator is placed in the secondary loop and suitably combined with a saturation nonlinearity in order to obtain actuator signal boundedness. The design procedure consists of four steps: 1) design of an established nonlinear seek-settle-track following controller for the VCM; 2) design of a linear track following controller for the secondary actuator; 3) observer design; and 4) design of a compensator to retain global stability and to improve performance. The proposed control system improves performance of both long-span seeking (proximate-time-optimal controller) and short-span seeking. In addition, it achieves high-bandwidth track following performance. The experimental results show good track-following performance, and short-span/long-span-seeking performance with fast settling time. The overshoot during track seeking can be made negligible for a suitably tuned VCM-actuator control loop.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2006.872003