Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.