Adaptive compensation of contact-induced vibration in high density HDD servo systems using peak filter method

Abstract

In this paper, a phase lead peak filter (PLPF) design method is adopted to adaptively compensate contact-induced vibration (CIV) in high density hard disk drive (HDD) servo systems. Such kind of vibration is a new vibration source due to continuous contact of the read/write head with the media in HDDs, and its main characteristics are the time-varying phase and magnitude and the narrow-band frequency spectrum. In the PLPF based controller, a baseline feedback controller is first employed to stabilize the servo loop and add-on peak filters are then connected in parallel with the baseline controller to further suppress the specific vibrations. Meanwhile, a frequency identification algorithm is plugged-in simultaneously to meet the variation of central frequency of CIV. The proposed CIV compensation scheme has simple control structure, is capable of dealing with multiple vibration modes that may not be within the bandwidth of open-loop transfer function, and possesses remarkable robustness to CIV change. In the end, the performance of the proposed method in CIV compensation is validated by simulation and experiment.

An Intuitive Design Method for Disturbance-Rejecting Peak Filters

“…Note that the bulges from the peak filters are oriented quite different, showing the advantage with an automatic design procedure. 6 Variations of the DC supply voltage also affects the amplitude of the output, but to a much smaller extent [12]. The transfer function from disturbances to control errors for a DTL and different controllers are shown in Fig.…”

“…where ∆ supp (t) is the relative voltage variation of the DC supply, the factor K g relates relative variations of the RF drive to relative variations on the cavity field [10], and ξ is the phase-pushing factor of the RF amplifier 6 . Typically 1 ≤ K g ≤ 2, and the RF amplifiers that will drive the considered cavities have ξ ≈ 10 • /%.…”

“…The filter can be seen as a model of the narrowband disturbance; see [2] for an insightful interpretation. Peak filters have been used for improved disturbance rejection in hard-disk-drive track following [3]- [6], and several other real-world applications [7]- [9].…”