An iterative learning controller for reduction of repeatable runout in hard disk drives
Graham, M.R.; de Callafon, R.A.; Shrinkle, L.
American Control Conference, 2006
Volume , Issue , 14-16 June 2006 Page(s):6 pp. -
Digital Object Identifier 10.1109/ACC.2006.1655418
Summary:In this study we consider the iterative learning control (ILC) framework to design a reference signal that reduces the periodic component of disturbances in a feedback measurement containing both repeatable and non-repeatable components. Reduction of periodic disturbances is useful in alleviating undesirable repeatable tracking errors in applications such as the two-stage servo track writing process for disk drives. A general problem description is given for a linear discrete time system and convergence robustness results for the learning system are derived. A learning filter is designed with the use of an FIR model approximation for the inverse of the closed-loop sensitivity for fast nominal convergence while robustness to modeling errors and non-repeatable disturbances is achieved through additional filtering. The ILC algorithm is applied to a disk drive system where experimental results demonstrate the effectiveness of the design method in reducing periodic measurement disturbances
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