International Business Machines Corporation

Michael L Workman

Charles R Nielsen

Gordon James Smith

Klaas Berend Klaassen

David A Thompson

Christopher H Bajorek

Thomas W Glaser

George R Santana

Stephen A Jove

Thomas C Christensen

Mantle M Yu

Calvin Shizuo Nomura

Eun K Row

Stephen F Edel

Michael R Hatchett

Matthew W Rooke

Kenneth G Yamamoto

Harold C Stephens

John S Heath

Hubert C Lee

Roger D Spencer

A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Adaptive system for optimizing disk drive power consumption

A multiple disk drive system having two disk-head assemblies (HDA) internally mounted on a rigid frame and accessible via a common industry-standard interface connector is provided. Each HDA is enclosed in a separate housing which is mounted on the disk drive system frame. A vibration damper mounted on the disk drive system frame physically contacts each HDA housing providing a spring force which minimizes the effects of shock and vibration on the operation of the HDAs. The vibration damper is coated with a low-wear, electrically insulating material to provide electrical isolation between the vibration damper and the HDAs housings. The coating material is chosen to also provide a desired coefficient of friction between the vibration damper and the HDA housings. A single electronic controller board is shared by both HDAs and is mounted on the bottom side of the frame underlying the HDAs. The controller board may implement SCSI or IPI interfaces in either differential or single-ended versions. The assembly is fully enclosed with metal top and bottom covers to provide separate enclosures for the HDAs, controller board cooling and EMC and RFI protection.

Vibration damper for a multiple disk drive unit

The present invention demonstrates a rotating media storage system which quickly measures and accurately compensates for thermal and mechanical errors in the position of the data detector with respect to the written data. This is accomplished by measuring the error rate of the written data as a function of the read offset of the detector. Error rates become increasingly large as the sensed noise to signal ratio becomes large. The present invention counts the number of errors detected in reading written data for various read offsets when the data storage system is initially activated. When the number of errors reaches a target rate, the read offset required to produce the target rate is saved. This procedure is performed on either side of the data track. The detector is then centered between the two offsets. During the operation of the storage system, thermal and mechanical errors are introduced into the detector position compensation means. The present invention compensates for this by periodically determining a new offset for each side of the data track. The new offset which corresponds to the target error rate is found by interpolating between measured offsets for error rates which are higher and lower respectively than the target error rate. The new measured read offsets are obtained by reading back written data in a similar manner as was used to obtain the initial read offsets. The detector is then recentered with respect to the write transducer position between the new offsets on either side of the data track.

Functional measurement of data head misregistration

A circuit for concurrently producing low noise electrical output signals which are amplified representations of signals produced by a magnetoresistive (MR) element and protecting said element from electrical short circuits which can occur between said element and its environment. A first feedback loop comprises (a) an input amplifier for amplifying a signal current from the MR element and (b) a source of bias current for biasing the MR element with a bias voltage. An input amplifier is concurrently biased by said current and amplifies a signal current from the MR element for producing a circuit output signal corresponding to dRh/RhRh and in which any differential direct current (dc) output offset error is minimized. (RhRh is the square of the time-averaged resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element.) A second feedback loop, electrically in series with the first feedback loop, biases the MR element toward a preselected reference potential and concurrently prevents flow of a current sufficient to damage the MR element in the event of a short circuit occurring between the MR element and its environment (e.g. the recording surface of a magnetic recording disk).

Low noise voltage-biasing amplifier for magnetoresistive element

A data recording disk file with a voice coil motor (VCM) actuator and a digital servo control system for positioning the read/write heads to selected concentric data tracks includes means for calculating the factor relating acceleration of the heads to VCM input current. This permits each disk file to compensate for any variation in the nominal VCM physical parameters, thus enabling VCMs to be manufactured to less demanding tolerances. The disk file also calculates a unique acceleration factor for each head position during movement of the heads from one track to another, thereby improving the arrival time of the heads to the target track. During an initialization procedure, the disk file performs a track seek, during which VCM current and head velocity information are acquired and used by the microprocessor in the digital servo control system to calculate a value representing an average actual acceleration factor unique to that disk file. This value, together with predetermined constants representing the characteristic relationship of acceleration factor to head position in a disk file with a nominal VCM, are used by the microprocessor to calculate the actual acceleration factor for each head position during a track seek.

Disk file digital servo control system with compensation for variation

A digital servo control system for a data recording disk file receives as input a digital head position error signal (PES) and a digital signal corresponding to the head actuator input signal, and outputs a digital control signal. The control signal is integrated and amplified to provide the input signal to the actuator. The control signal is calculated from estimated values of absolute head position, head velocity and the equivalent actuator input signal required to compensate for constant or very low frequency bias forces. The estimated values are functions of respective predicted values, which in turn are functions of, among other things, constants representing the digital sampling time and physical parameters of the actuator. The updating of the estimated values from the respective predicted values is made with the use of an error term, which is the error between the measured absolute head position and the predicted absolute head position. The predicted absolute head position is made sufficiently accurate that the error term is always less than a selected number of tracks. This permits the digital servo control system to operate during track seeking without counting track crossings so that the system is operable with servo information recorded either in sectors on a data disk or in continuous tracks on a dedicated servo disk.

Digital servo control system for a data recording disk file

An improvement to a disk file servo control system removes repeatable error from the read/write head position error signal (PES) during track following. The disk file includes a microprocessor 60 and associated memory devices 62, 64. A table of values of a sine function having a frequency equal to the disk rotational frequency is stored in a memory device. The microprocessor 60 receives each sample of PES from the servo control system and values from the sine function table in the memory device and computes a group of tap weights, each tap weight being a function of the PES sample, the value of a sine or cosine function with a frequency at one of the harmonics of the disk rotational frequency, a learning rate factor and the corresponding value of the tap weight for the previous PES sample. For each PES sample, the tap weights in a group are added to generate a repeatable error correction signal U.sub.c which is summed with the control signal U to the head actuator, thereby generating a modified control signal U.sub.m which causes the head to follow the true track centerline. The repeatable error components are thus removed from the PES.

Disk file servo control system with fast reduction of repeatable head

A servo system for a magnetic disk file having a voice coil motor (VCM) actuator generates a position error signal (PES) from servo information recorded on one of the disks. An electrical model of the VCM is employed through which a measure of the VCM electrical current is passed to generate a simulated PES signal which is continuous even if the regular PES is sampled or intermittent.

Magnetic recording disk file servo control system including an actuator

A servo system generates a velocity profile for moving a load from one position to another by dividing the time during which the load is moving into a plurality of segments, each segment being one half as long as the preceding segment. For each segment a fixed number of desired velocity values are stored and used to control the velocity of the moving load. This results in increasing resolution of the velocity wave as the load approaches its desired position, while not requiring excessive storage capacity for storing the desired velocity values.

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San Jose, CA, United States of America

Michael L Workman