Mohammadreza Chamanbaz — Research — Hard Disk Drive Servo Design

Hard Disk Drive Servo Design

Servo system in Hard Disk Drives (HDD) plays a crucial role in increasing the storage capacity by providing a more accurate positioning algorithm. The goal in this application is to achieve the storage density of 10 Tera bit per square inch (10 Tb/in^2). It requires the variance of the deviation of read/write head from the center of a data track to be less than 1.16 nanometer. Such a high performance has to be achieved in a robust manner, that is, for all drives produced in a mass production line. On the other hand, some imperfections in the production line such as manufacturing tolerances and slightly different materials or environmental conditions lead to slightly different dynamics over a batch of products. We formulated the problem of servo controller design of hard disk drive as uncertain {cal H}_2 and {cal H}_infty dynamic output feedback controller and solved the problems using various randomized algorithms.

The sensitivity transfer function for the designed robust H-infinity output feedback controller using a randomized method. The graph is generated by extracting 500 random samples from the set of uncertainty and forming the sensitivity transfer functions. As it is clear, all the sensitivity transfer functions are uniform as compared to the next Figure.

The sensitivity transfer function for a nominal H-infinity output feedback controller using Matlab hinfsyn command. The graph is generated by extracting 500 random samples from the set of uncertainty and forming the sensitivity transfer functions. The sensitivity transfer functions have some spike for some of the random samples indicating instability of the nominal controller for fairly a large portion of random samples. This shows the necessity of using robust controller in hard disk drives.

Publications

  • M. Chamanbaz, E. Keikha, V. Venkataramanan, A. Al Mamun and W. Qing-Guo, “Design of a Probabilistic Robust Track-Following Controller for Hard Disk Drive Servo Systems”, Mechatronics, Volume 24, Issue 6, September 2014, Pages 582-589, DIO, PDF.

  • M. Chamanbaz, V. Venkataramanan, and Q.-G. Wang, "Probabilistic Analytic Center Cutting Plane Method in Robust {cal H}_2 Track Following Control, Journal of Microsystems Technology, Volume 19, 2013, Pages 1407-1413, DOI, PDF.

  • M. Chamanbaz, V. Venkataramanan, and Q.-G. Wang, “Robust {cal H}_2 Track Following Controller Based on Probabilistic Analytic Center Cutting Plane Method,” in Proc. 2012 ASME-ISPS / JSME-IIP Joint International Conference on Micromechatronics for Information and Precision Equipment (MIPE2012), California, USA.

  • M. Chamanbaz, F. Dabbene, R. Tempo, V. Venkataramanan, and Q.-G. Wang, “A robust stability methodology for track following servo systems,” in Proc. APMRC, 2012 Digest, Pages 1–2, PDF.

  • M. Chamanbaz, E. Keikha, V. Venkataramanan, Q.-G. Wang, and A. Al Mamun, “Probabilistic Robust Approach for Discrete Multi-objective Control of Track-Following Servo Systems in Hard Disk Drives,” in Proc. 7th IFAC Symposium on Robust Control Design, Denmark, 2012, Pages 653-658, DOI, PDF.

  • E. Keikha, M. Chamanbaz, A. Al-Mamun, C.S. Bhatia “Design of track following controller of dual actuated HDD servo for 10 Tb/in2 magnetic recording,” in Proc. 2nd International Conference on Control, Instrumentation and Automation (ICCIA), 2011, Pages 264-269, DOI, PDF.

  • M. Chamanbaz, E. Keikha, V. Venkataramanan, A. Al Mamun, W. Qing-Guo, and T. Liew, “{cal H}_infty probabilistic robust control of Hard Disk Drive,” in Proc. IECON 2011 – 37th Annual Conference on IEEE Industrial Electronics Society, Pages 3394 –3399, DOI, PDF.