Near Contact Thermal Flying Height Control in Hard Disk Drives

• Published in: IEEE transactions on control systems technology Vol. 25; no. 1; pp. 39 - 46
• Main Authors: Matthes, Liane M., Knigge, Bernhard E., de Callafon, Raymond A., Talke, Frank E.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-01-2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Computational geometry; Convex functions; Convexity; Disk drives; Feedforward control; feedforward systems; Flight; Hard disks; Heuristic algorithms; Magnetoacoustic effects; microactuators; modeling; Modelling; nanopositioning; Optimization; Optimization techniques; perpendicular magnetic recording; Resistance heating; Sliders; Voltage measurement
• ISSN: 1063-6536; 1558-0865
• DOI: 10.1109/TCST.2016.2542040

A modeling and optimization approach is proposed and implemented for minimizing variations in flying height of thermal flying height control (TFC) sliders. The method utilizes the resistive heater element of TFC sliders for adjustment of spacing and the embedded thermal contact sensor (TCS) as a relative measurement for changes in flying height. In the modeling approach, the static and dynamic behavior of the TCS as a function of heater power is characterized. A model of the system is identified from experimental step excitation data using a realization algorithm. In the optimization approach, the optimal feedforward heater input profile is calculated via convex optimization techniques based on the static and dynamic behavior of the system. The modeling and optimization approach was verified experimentally, showing that the proposed approach reduces the difference between the maximum and the minimum value of the TCS measurements by a factor of two, indication a twofold reduction of flying height variations.