Edgar D. Sheh

Optimal H ∞ control for hard disk drives with an irregular sampling rate

This paper discusses the optimal H∞ control syn thesis via discrete Riccati equations for hard disk drives (HDDs) with an irregular sampling rate. A HDD servo system with an irregular sampling rate, caused by missing position error signal sampling data, is modeled as a linear periodically time varying (LPTV) system. An optimal H∞ track-following control algorithm for HDD servo systems with irregular sampling rates is proposed, which is based on the previous H∞ synthesis results for LPTV systems developed by some of the authors. A simulation and implementation study demonstrates that the proposed control synthesis technique is able to handle the irregular sampling rate and can be used to conveniently design a loop-shaping track-following servo that achieves the robust performance of a desired error rejection function for disturbance attenuation. Implementation results on an actual hard disk drive validate the simulation results.

Track-Following Control Design and Implementation for Hard Disk Drives with Missing Samples

Abstract Missing position-error-signal sampling data in hard disk drives (HDDs) results in their servo systems having irregular sampling rates. Due to the natural periodicity of HDDs, which is related to the disk rotation, HDD servo systems with missing samples can be modeled as linear periodically time-varying (LPTV) systems. Based on previous H ∞ control synthesis results for general LPTV systems developed by some of the authors, an optimal H ∞ track-following control algorithm for HDD servo systems with missing samples is proposed. A simulation and implementation study, which has been carried out on a set of hard disk drives, demonstrates that the proposed control synthesis algorithm is able to handle missing samples and can be used to achieve the robust performance of a desired error rejection function for disturbance attenuation. Implementation results on multiple real hard disk drives validate the predicted robust performance.