Rejection of Repeatable Run-Out in HDDS Using Inverse Frequency Dynamics

Abstract

In order to suppress the Repeatable Run-Out (RRO) of a following control system in HDDs is quite effective to increase the disk density. Many approaches were presented in former literatures, e.g. by applying adaptive filters and/or repetitive controllers. These approaches, however, require the complicated design in structures and parameters, preventing the controller design from saving time and labor. This paper presents a novel algorithm to suppress the effects of RRO on following control performance. In the proposed algorithm, the FFT (Fast Fourier Transform) is applied to identify a frequency characteristic of RRO. Based on the identified characteristics, an inverse system in frequency domain can be achieved to reject the effect of RRO. Numerical simulations and experimental results show the effectiveness of the proposed control.