Abstract: A system for balancing devices having motors and rotating masses to be coupled to the motors utilizes a momentum transfer mechanism to shift the rotating mass based on sensed imbalance. In this manner the mass is shifted to a position which accounts for the inherent imbalance in both the motor and the mass. A controller receives imbalance information from a velocity sensor and controls a solenoid to strike a base coupled to the motor to shift a lightly clamped mass relative to the motor. In one embodiment, a disk drive has disks initially biased by the system against a hub, and then shifted during rotation to create a disk drive having concentrically aligned disks offsetting imbalance inherent in a motor used to rotate the disks. In one embodiment, the disks are held to the hub by a clamp having screws. The screws are driven simultaneously through the same angle of rotation to ensure that the axial clamping force of each one is substantially equal.

Abstract: A disk drive includes a power driver chip, a microprocessor chip and a single reset line coupled to respective pins of the power driver and the microprocessor chip. The power driver chip includes a control circuit for inhibiting the power driver chip from de-asserting a reset signal on a reset line while the microprocessor chip is asserting the reset signal on the reset line.

Abstract: A partial-response maximum-likelihood (PRML) sequence detector with decision feedback equalization (DFE) for a disk drive read channel. The symbol recovery method for a disk drive read channel produces a sequence of samples X.sub.n of a magnetic readback signal with amplitudes representing the readback signal during corresponding sample intervals n=1-N. A DFE circuit generates a sequence of equalized samples y.sub.n and includes a feed-forward filter that removes precursor ISI from the sequence of sample signals x.sub.n to produce a sequence of feed-forward equalized samples w.sub.n, detection logic that translates the sequence of equalized samples y.sub.n into a sequence of detected symbols y.sub.n, and a feedback filter that filters the sequence of detected symbols y.sub.n to produce a sequence of equalization feedback values e.sub.n to offset postcursor ISI remaining in the sequence of feed-forward equalized samples w.sub.n. A combinational circuit receives the feed-forward equalized samples w.sub.

Abstract: A disk drive includes a disk having a plurality of tracks. The disk is formatted so that the tracks are grouped into zones. Each of the tracks within a zone on a particular surface of the disk is written with the same data rate. The disk is formatted with sectors having no sector ID fields. The disk also includes groupings of tracks called sparing partitions. Sparing partitions generally contain less tracks than the number of tracks within a zone. A desired number of spare sectors are placed in each sparing partition and some of the spare sectors are used at manufacture while at least one of the spare sectors in sparing partition is reserved for future use. The disk also includes spare tracks and the disk drive has the capability of identifying bad tracks or defects in the servo areas of a track which make it difficult for the transducer to track follow. Bad tracks are skipped and a spare track is used.

Abstract: A start-up controller is programmed to reduce current to a motor during a coast phase of an alignment state of the motor. The alignment state is divided into a plurality of phases based on time elapsed from the start of the alignment phase and the controller reduces the current when the elapsed time is substantially between a start and end time that define the coast phase. Because reduced current is provided to the motor during the coast phase, the total power and thus the thermal load on control components for the motor is decreased while the time the motor requires to "settle" into alignment is only slightly increased.

Abstract: A magnetic latch assembly for immobilizing a read/write head of a disk drive is provided which magnetically couples to an actuator assembly housing the read/write head with enhanced force. A disk drive which includes the magnetic latch assembly is also provided. The magnetic latch assembly includes a magnet and a magnet holder including ferromagnetic material which at least partially surrounds the magnet and provides a medium through which flux produced by one pole of the magnet travels to an opposing pole of the magnet. The latch assembly magnetically couples the actuator assembly by contacting the actuator assembly in an area adjacent one of the poles of the magnet. In one embodiment, the magnet holder includes ferromagnetic material which surrounds the magnet. In another embodiment, the magnet holder includes a plurality of ferromagnetic flanges which at least partially surround the magnet.

Abstract: A rotating disk memory apparatus includes an actuator assembly electrical interconnect. Flex circuit tape retainers are provided to substantially reduce and ideally eliminate torque forces on the actuator due to flex circuit bending. The retainers includes a tape guide having an inner wall to conform those portions of the flex circuit proximate both an actuator body member and a base plate connector member to predetermined configurations, such as loops providing a design specific exit angle for the flex circuit at each retainer. The looped portion of the flex circuit is held in the guide by a selectively detachable guide post device. The predetermined configuration is designed to minimize the torque on the actuator from inherent spring forces generated due to bending of the flex circuit during actuator motion relative to the rotating disk.

Abstract: A head disk assembly for a disk drive comprises a base, a bearing cartridge, a head stack assembly, and an elongated member. The bearing cartridge includes an inner shaft and an outer sleeve, the shaft being attached to the base and defining a pivot axis and the outer sleeve being rotatable relative to the pivot axis. The outer sleeve has a cylindrical sleeve surface. The head stack assembly includes an actuator body. The actuator body has a bore and a slot located adjacent to the bore such that the slot opens into the bore. The bore has a bore surface that defines a pair of ridges extending parallel to the length of the bore. The bearing cartridge is disposed within the bore.

Abstract: A head disk assembly (HDA) for a hard disk drive includes vibration damping structure. The HDA also includes an enclosure, a disk, a pivot bearing cartridge, and a head stack assembly (HSA). The enclosure includes a base that preferably includes integral side walls. The disk has a recording surface that has an annular landing zone. The pivot bearing cartridge includes a shaft fixed to the enclosure, and the head stack assembly is connected to the pivot bearing cartridge for rotation relative to the shaft. The HSA includes a head supported to be moved radially relative to the recording surface and to be brought to rest at a position in the landing zone. The base has a plurality of interior-facing surfaces including a major interior-facing surface parallel to the recording surface. Significantly, one of the interior-facing surfaces of the base serves as a bearing surface against which the vibration damping structure is compressed.

Abstract: A disk drive having error detection and correction capability includes a dedicated finite field processor for performing corrections and for generating software syndromes for miscorrection detection. The processor operates over a finite field under program control and performs parallel finite field multiplication and addition operations in a single execution cycle.

Abstract: Commutation is the process of driving current through the windings to produce a rotating magnetic field that the rotor attempts to catch. Typically, four to six commutation cycles occur for each rotation of the rotor of the motor. Unlike traditional commutation methods where only six phases are commutated during one commutation cycle, the hybrid commutation cycle includes 12 phases. The particular method for commutation switches between current driving modes where one driving mode drives current through all three windings and an other driving mode drives current through less than all three windings of the motor. More particularly, in the second driving mode current is driven through two windings of the motor. During a commutation cycle, these driving modes are alternated.

Abstract: A memory system includes an array of solid-state memory devices which are in communication with and under the control of a controller module via a device bus with very few lines. This forms an integrated-circuit mass storage system which is contemplated to replace a mass storage system such as a disk drive memory in a computer system. Command, address and data information are serialized into component strings and multiplexed before being transferred between the controller module and the array of memory devices. The serialized information is accompanied by a control signal to help sort out the multiplexed components. Each memory device in the array is mounted on a multi-bit mount and assigned an array address by it. A memory device is selected by an appropriate address broadcast over the device bus, without requiring the usual dedicated select signal. A particular multi-bit mount configuration is used to unconditionally select the device mounted thereon.

Abstract: A swing type structure for a head stack assembly of a disk drive includes a body portion, a coil portion, and at least one actuator arm structure. The actuator arm structure includes at least one elongated column, and a pair of wires in tension. The body portion has a bore defining a longitudinal axis, and the coil portion is cantilevered from the body portion. The elongated column is cantilevered from the body portion in an opposite direction from the coil portion and has a distal end. Each wire is positioned on an opposite side of the elongated column and converges on the distal end such that the elongated column is in compression as a result of the pair of wires.

Abstract: The invention resides in a load beam assembly forming part of a head stack assembly in a magnetic disk drive, the load beam assembly biasing a transducer head against a rotating magnetic disk. The load beam assembly normally has spring and hinge functions combined in a single "spring/hinge" portion of a load beam stamped from a stainless steel sheet. Here, however, the spring and hinge functions are uniquely separated from one another in separate spring and hinge members. The preferred load beam assembly has a base portion, a load beam, and a hinge member joining them so that the load beam pivots relative to the base portion. The load beam is further provided with a bearing surface that cooperates with a preferred spring member, one end of the spring member being fixed relative to the base portion and the other end contacting the bearing surface of the load beam.

Abstract: An apparatus and method useful in a servo-track writer (STW) system for simultaneous servowriting of tracks on disk surfaces in a plurality of disk drive head assemblies (HDAs). The STW system includes a motor disposed to turn a drive shaft on a shaft axis. The drive shaft is supported in a base air bearing and coupled to a rotatable elongated push-tower apparatus such that shaft rotation causes rotation of the push-tower apparatus on a STW bearing axis disposed coaxially with the shaft axis. The push-tower apparatus includes an externally-fixed retroreflector displacement sensor and a plurality of fixed HDA actuator arm engaging pins each disposed to engage one of a plurality of HDAs mounted in alignment in a stationary HDA positioning apparatus. Push-tower rotation moves each engaging pin into contact with a respective HDA actuator arm, moving the actuator arm to a position that is determined by processing position information feedback from the push-tower retroreflector displacement sensor.

Abstract: A method and system for a disk drive that estimates demand DAC saturation current by performing a first slew with the demand DAC in saturation, and then iteratively refining the estimate in response to a sequence of slews with the demand DAC not in saturation. Each successive slew is performed with the demand DAC preloaded with an acceleration value calculated in the previous iteration. To perform each slew, the disk drive microcontroller loads the demand DAC with an acceleration value, waits a predetermined time interval, and reads servo signals to identify the track to which the head has slewed at the end of the time interval. The microcontroller then calculates the distance traveled by the actuator during the present slew and uses the ratio of this head travel distance to the head travel distance of the first (saturated) slew to refine the saturated acceleration value estimated in the previous iteration. These estimates converge over successive iterations toward the desired demand DAC saturation current.

Abstract: A disk clamp for holding a recording disk in a disk drive. The clamp is ring-shaped and includes stiffened inner and outer regions with a softened middle region located in between. The inner region is stiffened by bending the inner edge. The outer region is stiffened by involuting the outer edge back on itself A disk contact zone is included in this outer region. The clamps may be made of sheet metal, such as stainless steel.

Abstract: A disk drive includes an enclosure having a base, a spindle motor fixed to the base, a disk mounted on the spindle motor, a pivot bearing cartridge, and a head stack assembly. The pivot bearing cartridge includes a shaft fixed to the enclosure, and the head stack assembly is connected to the pivot bearing cartridge for rotation relative to the shaft. The head stack assembly includes a body portion having a bore which surrounds the pivot bearing cartridge, a plurality of actuator arms with each arm cantilevered from the body portion, and a coil portion. The coil portion is cantilevered from the body portion in an opposite direction from the plurality of arms and provides damping of vibrations induced in the head stack assembly. The coil portion includes a plastic portion having a thickness, and a coil embedded in the plastic portion. The plastic portion includes a plurality of openings where each opening extends through the entire thickness of the plastic portion.

Abstract: The invention relates to a magnetic disk drive having a head stack assembly including a rotary actuator body having a flex circuit mounting site for mounting a main actuator flex circuit and an arm extending therefrom which supports a head gimbal assembly (HGA). The invention provides for molding the conductors into the arm and the actuator body so that the conductors are strategically exposed along the flex circuit mounting side of the actuator body and along an end of the arm body which mates with the HGA.

Abstract: A noise suppression system for use in a disk drive. The system isolates the interface between the disk drive cover and the moving parts of the disk drive to attenuate acoustic energy introduced by the moving parts and also dissipates some of the unwanted acoustic energy in viscoelastic damping layers. An outer plate made of a rigid layer covered with a viscoelastic damping layer is disposed over an inner cover in which is provided an open region surrounding the pivot axis of the head-stack assembly (HSA) or, alternatively, surrounding both the pivot axis and the spindle axis of the disk assembly. A rigid interface member is fixed to the pivot journal or, alternatively, to both the pivot journal and the spindle journal within the open region. The outer plate is fitted to the periphery of the inner cover so that the viscoelastic damping layer abuts a flexible sealing member fitted over the interface member and inner cover around the open region.