Nonlinear mid-frequency disturbance compensation in hard disk drives

Authors:	Li Ying, Nanyang Technological University, Singapore Guo Guoxiao, Data Storage Institute, Singapore Wang Youyi, Nanyang Technological University, Singapore
Topic:	4.2 Mechatronic Systems
Session:	Mechatronics for Data Storage Devices II
Keywords:	Disk drives, Disturbance rejection, narrow band, nonlinear control

Abstract

In single-stage hard disk drives (HDDs), it is difficult to suppress mid-frequency narrow band disturbances caused by disk flutter or windage due to phase stabilization. This article presents a nonlinear compensation scheme to deal with mid-frequency disturbance. The nonlinear compensator can provide additional phase lead without degrading the magnitude characteristic. This can be used to compensate for phase loss due to narrow band filter and make mid-frequency disturbance suppression more effective. Settling performance is improved by diverting the compensator pole to lessen adverse effect of harmonics. The efficacy of nonlinear disturbance compensation is demonstrated via simulationthat it is more powerful to reject mid-frequency disturbance. Our results show that the power spectra of NRRO due to disk vibration are decreased by 99% and TMR value is improved 68%.