Saturation-Induced Instability and Its Avoidance in Adaptive Control of Hard Disk Drives

• Published in: IEEE transactions on control systems technology Vol. 18; no. 2; pp. 368 - 382
• Main Authors: Perez-Arancibia, N.O., Tsu-Chin Tsao, Gibson, J.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptative systems; Adaptive control; Adaptive control systems; Adaptive filters; Applied sciences; Broadband; Computer science; control theory; systems; Control system synthesis; Control theory. Systems; Control-signal saturation; Controllers; Disk drives; Electronics; Exact sciences and technology; Finite impulse response filter; Frequency; frequency weighting; Gain; hard disk drive (HDD); Hard disks; iterative adaptive tuning; minimum-variance adaptive control; Miscellaneous; Optical control; Programmable control; Signal processing algorithms; Stability; Storage and reproduction of information; Tracking; Tuning; Saturation; Control synthesis; hard disk drive (HDD); Iterative method; Control-signal saturation; Adaptive control; Frequency weighting; Frequency control; minimum-variance adaptive control; Minimal variance; Wide band; Filter; Instability; Hard disk; High frequency; iterative adaptive tuning
• ISSN: 1063-6536; 1558-0865
• DOI: 10.1109/TCST.2009.2018298

This paper presents an investigation of the design and implementation of minimum-variance adaptive controllers for computer hard disk drive (HDD) read-write track following. A common characteristic of minimum-variance controllers, adaptive or not, is that they rely on prediction filters with large high-frequency gains to predict broadband disturbances, and this often produces control-signal saturation and eventual loss of stability. Two methods are introduced here to address this issue. The first method, suitable for online adaptive control, uses frequency weighting to constrain the high-frequency gain of the prediction filter. The second method, suitable for tuning fixed-gain controllers, employs an adaptive scheme iteratively over a finite duration. Both methods were implemented on a commercial hard disk drive, and experimental results demonstrate their effectiveness.