Seagate Technology Incorporated

Miniscribe Corporation

John Jay Freeman

James Joseph Touchton

John P Squires

Louis John Fioravanti

Alan Thomas Nagl

Alan D Kronisch

A method of detecting a leak of low-density gas from an enclosure containing a rotating storage disc includes monitoring a signal which varies in response to variations in the concentration of the low-density gas in the enclosure. Additional quantities of the low-density gas are added to the enclosure when the monitored signal indicates that the concentration has dropped below a predetermined level. Monitoring the concentration of the low-density gas may include monitoring actual concentration levels of the gas using a pressure sensor located within the enclosure or monitoring disc mode vibration amplitudes using an accelerometer attached to the enclosure. Indirect monitoring of the vibration amplitudes may also be accomplished using sensors such as a laser Doppler vibrometer, a capacitance probe or the servo head position feedback circuitry found within a disc drive or a dedicated servo track writer.

Disc drive servo track writer gas leak detector and method

A method and system for driving a phase of an electrical motor are disclosed. The method and system detect the back electromotive force being generated by a coil. The back electromotive force is amplified or attenuated to a level necessary to drive the motor at a desired speed and is fed back into the coil. The detected back electromotive force signal that drives the motor is proportional to, in phase with, and at the same frequency as the back electromotive force signal being generated by the coil. Using the back electromotive force to produce the drive signal permits autosynchronization of the drive signal without use of position sensors and reduces acoustic noise and velocity modulation associated with sudden torque shifts.

Self-synchronizing AC synchronous driver for DC brushless motors

An apparatus for subjecting a disc drive to rotational vibration test profiles includes a mounting base, a disc drive mounting plate, and a rotary vibration motor assembly mounted between the mounting plate and the base in which the disc drive mounting plate may be vibrationally rotated about an axis through the base and plate. The motor assembly preferably includes a plurality of voice coil motors mounted and radially spaced about a tubular shaft supporting the disc drive mounting plate. The voice coil motors are connected and driven in series to impart the rotational vibrational profile to the disc drive mounted on the mounting plate. The method involves providing a support structure, a rotatable shaft carried by the support structure, a voice coil motor connected to the shaft for reciprocally rotating the shaft, mounting a device to be tested on the shaft, and applying a current to the voice coil motor to reciprocally rotate the shaft to vibrate the device.

Method and apparatus for subjecting a device to rotational vibration

An n-phase, m-pole (wherein n and m are integers) brushless motor is driven without use of physical rotary position detectors, such as Hall elements or the like. An harmonic component of back emf induced in the phases of the motor is detected and used to generate phase energizing signals (such as in response to zero crossings of the detected harmonic component) which, in turn, energize selected phases of the motor. Drive current is supplied to those phases which are energized by the phase energizing signal in predetermined sequence.

Method and apparatus for driving a brushless motor

An n-phase DC motor is controlled by converting a motor speed command signal generated from a programmed CPU to a motor drive signal and using this motor drive signal to apply DC power to a selected phase of the motor, the amount of applied DC power being a function of the value of the motor speed command signal. Signals representing the position and/or speed of the motor are supplied to the CPU from which the CPU detects speed errors. The speed command signal then is modified to speed up or slow down the motor so as to reduce the detected errors.

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Longmont, CO, United States of America

John Jay Freeman