Sperry Rand Corporation

Memorex Corporation

Unisys Corporation

Sperry Corporation

Information Storage Systems, Inc.

Frank J Sordello

James Joseph Touchton

Andrew M Rose

Robert L Cloke

John Cuda

Edward R Darrah

A method for measuring bit shift and other characteristics indicative of the performance of a magnetic storage system, particularly for a system employing a thin-film magnetic head. In a preferred embodiment, complementary patterns are written many times around a circular track of a magnetic disk, each pattern including relatively closely spaced magnetic transitions as well as relatively widely spaced magnetic transitions. The relatively widely spaced transitions are chosen so as to be substantially unaffected by any other transitions. Measurements are made with reference to these widely spaced transitions and averaged for the many patterns recorded in the track so as to rapidly provide highly reliable measurements indicative of system performance.

Method for testing components of a magnetic storage system

A method for measuring bit shift, timing asymmetry and other characteristics indicative of the performance of a magnetic storage system, particularly for a system employing a thin-film magnetic head. In a preferred embodiment, complementary patterns are written many times around a circular track of a magnetic disk, each pattern including relatively closely spaced magnetic transitions as well as relatively widely spaced magnetic transitions. The relatively widely spaced transitions are chosen so as to be substantially unaffected by any other transitions. Measurements are made with reference to these widely spaced transitions and averaged for the many patterns recorded in the track so as to rapidly provide highly reliable measurements indicative of system performance.

Method for measuring timing asymmetry in a magnetic storage system

A disk storage system is disclosed comprising a rotatable disk, a cooperating magnetic head, positioning apparatus for positioning the head at different radial positions of the disk for reading and/or writing data on the disk, a baseplate for supporting the above, and control circuitry for preventing oscillation build-up in the baseplate from deleteriously interfering with system performance. The control circuitry is constructed and arranged to control the timing of head positioning operations so as to inhibit the reinforcement of baseplate oscillations.

Disk accessing circuitry

As an aid in counting servo tracks in a position servo system, a position window detector (30) which normally provides coarse and fine pulses to counting logic (53) also provides fine pulses to a reset switch (45) of a tachometer signal integrator means (33), resetting the integrator once for each track. In the event of position signal drop-out wherein coarse pulses are not properly generated, a threshold detection means (43) senses when the output of the integrator reaches a threshold level and produces a threshold reached signal which is transmitted to counting logic means (53) for incrementing a track counter (61).

Method and apparatus for locating a movable servo controlled member

A servo system for accurately positioning a transducer relative to data paths on a recording medium by detecting sync and servo signals from two parallel abutting servo tracks sharing a common longitudinal boundary within circumferentially spaced sectors of the medium. Within each sector of the recording medium, two servo waveforms of different frequencies in two abutting servo tracks are preceded by a sync reference waveform of the same frequency in both servo tracks which is used as a reference for a phase locked oscillator, connected to the transducer, generating a pair of modulation signals that are to be mixed with transducer signals from both servo waveforms. A pair of servo channels are provided for receiving the pair of modulation signals and the servo signals for deriving an imbalance error signal representing deviation of the transducer from the center line of a data path, which is the projection from the sectors of the common longitudinal boundary between servo tracks. The imbalance error signal is used to center the transducer on the data path.

Sectorized data path following servo system

An electronic tachometer comprising an integrator having its output coupled to a variable gain amplifier and responsive to an input signal representative of the acceleration of a moveable load, such as a head assembly of a disk drive, for producing a coarse velocity signal at the output of the variable gain amplifier indicative of the load velocity, a tachometer gain correction circuit including another integrator coupled to receive the coarse velocity signal to produce a coarse distance signal indicative of distance traveled by the load and means for combining the coarse distance signal with a reference distance signal to produce a distance error signal which functions to adjust the gain of the variable gain amplifier so as to vary the coarse velocity signal to make the coarse distance signal equal to the reference distance signal, and accumulative error compensation means coupled to receive a gain indicative signal derived from the distance error signal to produce a signal input to the tachometer integrator which compensates for accumulative error in the tachometer output, whereby the tachometer accurately indicates load velocity.

Self-regulating electronic tachometer

A system for detecting data from and recording data on a recording media whereby a single clocking signal generator is utilized for generating the clocking signal both during the recording of data on and the reading of data from the recording media.

System for recording and reading back data on a recording media

A signal compensator for a position servo loop system to attenuate the position error signal and provide stability at a larger band width by limiting the position actuator current in selected frequency ranges.

Servo system with feedback signal compensation

A closed loop servo system for positioning a head relative to a magnetic recording element wherein track crossings are normally utilized to generate a feedback signal to the servo for positioning the head and wherein for a precise indication of head positioning between track crossings the velocity of movement of the head is integrated and fed into the servo system to provide a fine position signal.

Coarse and fine control for position servo

A sinusoidal oscillator including means for electronically varying the frequency of oscillation by altering the phase angle of the amplifier circuit phase shift.

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Los Gatos, CA, United States of America

Frank J Sordello