Rejection of Unknown Periodic Disturbances in Magnetic Hard Disk Drives

The magnetic hard disk drive (HDD) has become a cost-effective means to meet the expanding demands for large data storage capacities in portable electronic devices. A particular problem an HDD faces in such applications is periodic disturbances caused by different kinds of external forces. In this paper, an adaptive controller based on an algorithm proposed by Brown has been developed and applied to identify and reject unknown periodic disturbances in a mobile HDD. Numerical simulations and experiments are conducted and superior convergence properties of the proposed method are shown compared with a method taken from the literature called frequency chasing peak filter. It is found that the convergence rate of the proposed method is less susceptive to the error in the initial frequency estimate in the frequency range of interest. The effect of unaddressed frequency components on the convergence and performance of the controller is also discussed.