Patent ID: 8582231

Claim:
A disk drive comprising: a disk; a head actuated over the disk; a dynamic fly height (DFH) actuator operable to control a fly height of the head over the disk in response to a DFH setting; a touchdown (TD) sensor operable to generate an analog TD signal; and control circuitry operable to: compare the analog TD signal to a TD threshold in order to generate a calibrated TD threshold for a plurality of different DFH settings; curve fit the calibrated TD thresholds and corresponding DFH settings to an estimated curve; adjust at least one of the TD threshold and the DFH setting and predict a corresponding next point in the estimated curve; determine an actual next point corresponding to the adjustment; generate a prediction error based on a difference between the predicted next point and the actual next point; and detect a touchdown of the head on the disk when the prediction error exceeds a prediction threshold.