Abstract: A method of controlling track seeking and track following of a head in a disk file having servo information recorded thereon to provide a track number and a position error signal (PES). The physical parameters of the disk file are modeled by at least three sets of constants associated with selected numbers of tracks. An actuator is connected to the head by a support arm assembly and is responsive to a control signal for positioning the head. The method comprises, for each servo information sample, the steps of predicting a relative position, velocity, and bias of a data head. It is determined whether the predicted relative data head position corresponds to the selected number of tracks, if not, at least the predicted relative data head position is rescaled to form the predicted relative data head position to correspond to the selected number of tracks of the predicted data head position prior to rescaling.