Abstract: The fly height of read/write heads in multiple disk drives is dynamically adjusted to optimum fly height by a servo loop. The fly height is sensed in real time with a harmonic ratio fly height detector and compared to an optimum or reference fly height. The suspension system of each head is adjusted in accordance with the departure of the fly height of that head from the optimum fly height. The adjustment of the suspension system is accomplished by bonding a piezoelectric film to the flexible suspension arm carrying each head. The fly height is corrected for both radial and circumferential error as the head changes radial and circumferential position relative to the disk surface. The reference fly height, to which each head is moved by the servo loop, may be selectively changed in the fly height servo operation. This can be done to lift the heads away from the disk surface during track seek mode or disk drive sleep mode.

Abstract: In a storage device, such as a magnetic rigid disk drive, data is stored at varying linear densities in the user data storage portions to increase the effective storage capacity of the device as a function of the differences in soft error rate tolerance associated with the various types of data being stored and the ability of non-alphanumeric data to be enhanced by reconstruction or smoothing rather than by an error correction code. A data type signal included with incoming data dictates the recording frequency and a control signal associated with the recorded data block is read when data is addressed to appropriately adjust the clock frequency for reading such addressed stored data.

Abstract: Apparatus and method of even harmonic distortion compensation are provided for digital data detection in a disk file. The disk file includes a magneto-resistive (MR) head or other magnetic transducer head and an analog-to-digital converter (ADC) for providing a sampled readback signal. An even harmonic filter is coupled to the ADC for providing a filtered readback signal having only even harmonic components. An adder subtracts the filtered readback signal from the sampled readback signal for providing a compensated output signal. The compensated output signal is applied to a digital channel of the disk file.

Abstract: A method and apparatus for minimizing the effects of non-stationary high-energy noise sources in magnetic data storage channel through the use of an oversampling and post-sampling filtering anti-aliasing procedure. The initial analog data is sampled at a rate sufficiently above the Nyquist rate to avoid aliasing. The high-frequency sampling stream is then digitally filtered to produce a lower-rate digital data stream having a reduced Nyquist rate introduced by the post-sampling digital filter. Because the anti-aliasing post-sampling filter is digital, no phase distortion is introduced in the readback data signal. Because the post-sampling digital filter lowers the Nyquist rate, late digital processing and decoding is accomplished without aliasing at a data rate below the initial Nyquist rate. High-energy noise pulses are preserved without smearing and can be simply removed by the usual error-correction method.

Abstract: A bias current servo loop for a magneto-resistive recording head detects distortion in the read signal from the MR head, and adjusts the operating point for the head to minimize the distortion. The distortion is detected by monitoring the second harmonic of a digitized sample of the read signal. A running average of the digitized amplitude of the second harmonic is generated by a digital bandpass filter. The root mean square of the running average of the digitized amplitude of the second harmonic is estimated. The estimated RMS value is compared against a reference value indicative of minimum distortion and the difference between the estimated RMS value and the reference value is used to adjust the bias current.

Abstract: A method for predicting and avoiding data errors by predicting disk drive read-write inhibit requirements in response to at least two parameters including a head position error and velocity with respect to the track centerline. A write or read inhibit signal is generated in response to selected combinations of these parameters to minimize soft read errors arising from track misregistration and to avoid hard errors arising from overwriting data recorded in an adjacent track. The read and write inhibit strategy is described as a pair of linguistic control rules suitable for implementation in a Fuzzy Logic Controller.

Abstract: A rotary actuator head driver for a direct access storage device includes a transducer head moving in a radial direction across a disk surface for reading and/or writing data on a plurality of tracks for storing data. A support arm supports the transducer head relative to the disk surface. The support arm is connected to a pivot defining an axis of rotation spaced from the transducer head. A head driver positions the transducer head over one track in a track following mode or moves the transducer head from one track to another track in a seek mode. The head driver generates oppositely directed forces to produce a net torque applied to the support arm through the pivot. The oppositely directed forces have a line of action orthogonal a dominant motion of the transducer head. As a result, any parasitic force is orthogonal to the dominant motion and does not contribute to track misregistration errors.