Patent ID: 8004788
Filing Date: 2011-08-23
Classification: G11B

Abstract:
1. A method for detecting touchdown between a magnetic head and a recording medium, comprising: measuring a baseline position error signal of the magnetic head with the magnetic head at a baseline position; determining a synchronous portion of the baseline position error signal; generating an adjusted baseline position error signal by removing the synchronous portion of the baseline position error signal from the baseline position error signal; measuring additional position error signals of the magnetic head with the magnetic head positioned successively closer to the recording medium with each additional measurement; generating adjusted position error signals by removing the synchronous portion of the baseline position error signal from each of the additional position error signals; converting the adjusted baseline position error signal and each of the adjusted position error signals from a time domain into a frequency domain; and detecting touchdown based on a combined variance value that is computed from variances in the adjusted position error signals with respect to the adjusted baseline position error signal at each of a discrete number of frequencies that are within one or more selected frequency bands in the frequency domain.