Abstract: A disc drive head positioning apparatus includes a head, a suspension which supports the head, a piezoelectric microactuator which is operatively coupled to the suspension, and a charge feedback driver which is operatively coupled to the piezoelectric microactuator. A method of positioning the head relative to a storage medium is also provided.

Abstract: The present invention incorporates an add-on adaptive feedforward controller into the existent track-following servomechanism of a dual-actuator disc drive to suppress the disturbance caused by mechanical interaction of the two actuator assemblies to thereby enhance the positioning accuracy at track following. The control signal fed into the power amplifier of one actuator is also used as the input signal of an adaptive controller in the other one. In an illustrative embodiment, the information is fed into an adaptive LMS filter. The output of the adaptive filter is then used as a feedforward signal to coordinate the head position with the desired track position. By matching the unknown disturbance dynamics with a filtered-x LMS (least mean square) adaptation algorithm, the output of the feedforward controller is able to cancel the disturbance from mechanical interaction, and thereby realizes the necessary fast, accurate head positioning.

Abstract: A method and apparatus are provided for positioning a head over a disc in a disc drive while maintaining servo loop stability. The apparatus includes an actuator-head assembly having a large scale actuator and a micro-actuator that are both able to move the head over the disc. An anti-windup compensation component detects when a micro-actuator controller is producing a micro-actuator control value that will saturate the micro-actuator. Using the micro-actuator control value, the anti-windup compensation component generates a saturation tracking error signal. A summing component then combines a position value that the head generates based on its position over the disc with the saturation tracking error signal to form a position error value that masks the saturation of the micro-actuator.

Abstract: A method and system for providing plant variation compensation for a microactuator in a dual-stage servomechanism of a disc drive. The method includes performing indirect adaptive filtering to identify plant variation in the microactuator, and tuning a compensator for the microactuator based on the plant variation. The indirect adaptive filtering can be performed using a two-stage process, including a first stage of adaptive modeling for the dual-stage servomechanism and a second stage of generating an indirect mode-reference inverse for the microactuator. A combined process can alternatively be employed. The microactuator can be a piezoelectric microactuator which forms a PZT system. The dual-stage servomechanism also includes a coarse actuator such as a voice coil motor.

Abstract: A method and apparatus for compensating for repeatable run-out errors in a disc drive is provided in which transfer function values for a servo loop in the disc drive are first determined. A sequence of repeatable run-out values for a portion of the disc drive is then determined. A transform is applied to the sequence of repeatable run-out values to obtain frequency-domain repeatable run-out values. Each frequency-domain repeatable run-out value is divided by a respective transfer function value to produce a sequence of frequency-domain compensation values which are then stored. An inverse transform is applied to the frequency-domain compensation values to obtain a sequence of time-domain compensation values. The sequence of time-domain compensation values is inserted into the servo loop.

Abstract: A method of configuring a discrete-time servo controller in a fixed-point digital signal processor (DSP) for controlling a servo actuator in a disc drive includes obtaining a stable, closed-loop representation of the servo controller and the servo actuator. Bounds on the controller states are derived from the stable closed-loop representation. The controller states are scaled based on the controller state bounds, and the servo controller is configured in the DSP based on the scaled controller states.

Abstract: A method and apparatus are provided for positioning a head based on a control signal and a cancellation signal. In the method and apparatus, a sensor located in the disc drive is capable of generating sensor data samples at a sensor data rate that is different from a servo data rate. A data enlarger inserts additional data samples between the sensor data samples to produce enlarged data that is filtered to produce filtered data, which is decimated to form decimated sensor data at the servo data rate. A cancellation component converts the decimated sensor data into a cancellation signal that may be combined with a control signal to control the actuator. A sensor chip is also provided that includes a sensing element and a sigma-delta circuit that cooperate to generate sensor samples at a sensor data rate and a buffer that stores sensor samples at the sensor data rate.

Abstract: A method and apparatus for compensating for repeatable run-out errors in a disc drive is provided in which transfer function values for a servo loop in the disc drive are first determined. A sequence of repeatable run-out values for a portion of the disc drive is then determined. A transform is applied to the sequence of repeatable run-out values to obtain frequency-domain repeatable run-out values. Each frequency-domain repeatable run-out value is divided by a respective transfer function value to produce a sequence of frequency-domain compensation values which are then stored. An inverse transform is applied to the frequency-domain compensation values to obtain a sequence of time-domain compensation values. The sequence of time-domain compensation values is inserted into the servo loop.

Abstract: A disc drive including a rotatable data track, a dual-stage actuator with a primary actuator motor supporting an actuator arm, a read/write head supported by the actuator arm and communicating with a secondary actuator motor, and steps for controlling range of motion of the secondary actuator motor. The controlling steps include supplying and sustaining a bias signal to a single-sided unipolar device driver that then apply a bias voltage the secondary actuator motor to induce the secondary actuator motor to expand substantially one half of its expansion capabilities. And, confining correction signals provided by a control circuit of the disc drive, used in correcting mechanical position of the secondary actuator motor, to a voltage ranging substantially between a positive “+” and negative “−” voltage substantially equal to the applied bias voltage.

Abstract: A sensor chip is provided that includes a sensing element and a sigma-delta circuit that cooperate to generate sensor samples at a sensor data rate and a buffer that stores sensor samples at the sensor data rate. Although the buffer stores the samples at the sensor data rate, it is capable of providing the samples to an external circuit at a higher data rate. In one embodiment, the sensor chip is able to provide the stored sensor samples to an off-chip component at a rate set by the off-chip component.

Abstract: A method of implementing a model based servo controller in a digital signal processor in a disc drive includes obtaining matrices for a discrete-time state-space realization of the servo controller. Controller states of the controller are scaled to reduce a worst case bound on the controller states. The controller states are transformed to a desired format which reduces a number of required mathematical operations. Further, the matrices are converted to fixed point format.

Abstract: The invention relates to a copolyester, having (a) a repeat unit of a dicarboxylic acid component, having from 80 to 100 mole % terephthalic acid or the corresponding ester thereof, and from 0 to 20 mole % of a modifying aromatic dicarboxylic acid having less than or equal to 20 carbon atoms or the corresponding ester thereof, wherein the total mole % of dicarboxylic acid component is equal to 100 mole %; and (b) a repeat unit of a glycol component, having from 5 to 85 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol, ethylene glycol of from 15 to 95 mole %, and at least 1 mole % of a modifying glycol having from 3 to 16 carbon atoms, wherein the total mole % of glycol component is equal to 100 mole %. The invention also relates to a method of making the copolyester described above. The invention also relates to articles made from the copolyesters described above. The invention further relates to a method of determining the melt strength and sag of a polyester.

Abstract: A blend of polycarbonates of dihydroxydiphenyl cycloalkanes and optionally 4,4'-isopropylidenediphenol with polyesters from terephthalic acid, isophthalic acid, 1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, having the advantage of being colorless and providing an unexpected amount of impact strength, hardness and heat resistance. The polymer blends are especially suitable for the manufacture of clear molded articles, fibers, sheeting, and film.

Abstract: A blend of polycarbonates of dihydroxydiphenyl cycloalkanes and optionally 4,4'-isopropylidenediphenol with polyesters from terephthalic acid, isophthalic acid, ethylene glycol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, having the advantage of being colorless and providing an unexpected amount of impact strength, hardness and heat resistence. The polymer blends are especially suitable for the manufacture of clear molded articles, fibers, sheeting, and film.

Abstract: Disclosed are clear blends comprising:(A) from 1 to 99 percent by weight of a polycarbonate comprising a diol component comprising from 90 to 100 mol percent 4,4'-isopropylidenediphenol units and from 0 to 10 mol percent modifying diol units having 2 to 16 carbons, wherein the total mol percent of diol units is equal to 100 mol percent; and(B) from 1 to 99 percent by weight of a polyester comprising(a) a dicarboxylic acid component comprising from 80 to 100 mol percent dicarboxylic acid units selected from the group consisting of terephthalic acid units, isophthalic acid units, and mixtures thereof; and from 0 to 20 mol percent modifying dicarboxylic acid units having about 2 to 20 carbons, wherein the total mol percent of dicarboxylic acid units is equal to 100 mol percent; and(b) a glycol component comprising from 30 to 99 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units, from 1 to 70 mol percent ethylene glycol units, and from 0 to 10 mol percent modifying glycol units having from 3 to 16 carbons,

Abstract: A blend of polycarbonates of dihydroxydiphenyl cycloalkanes and optionally 4,4'-isopropylidenediphenol with polyesters from terephthalic acid, isophthalic acid, neopentyl glycol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, having the advantage of being colorless and providing an unexpected amount of impact strength, hardness and heat resistance. The polymer blends are especially suitable for the manufacture of clear molded articles, fibers, sheeting, and film.

Abstract: The invention relates to a copolyester, having (a) a repeat unit of a dicarboxylic acid component, having from 80 to 100 mole % terephthalic acid or the corresponding ester thereof, and from 0 to 20 mole % of a modifying aromatic dicarboxylic acid having less than or equal to 20 carbon atoms or the corresponding ester thereof, wherein the total mole % of dicarboxylic acid component is equal to 100 mole %; and (b) a repeat unit of a glycol component, having from 5 to 85 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol, ethylene glycol of from 15 to 95 mole %, and at least 1 mole % of a modifying glycol having from 3 to 16 carbon atoms, wherein the total mole % of glycol component is equal to 100 mole %. The invention also relates to a method of making the copolyester described above. The invention also relates to articles made from the copolyesters described above. The invention further relates to a method of determining the melt strength and sag of a polyester.

Abstract: A system and method validate a model used in implementing a model-based servo controller in a disc drive. A nominal model is first constructed. The nominal model is augmented with an uncertainty description to characterize variations in drives to be manufactured. The model is constrained by performance objectives. Weights corresponding to the uncertainty description and performance objectives are adjusted based on a comparison between a .mu. matrix function and a .mu..sub.g matrix function until a desired performance level is achieved while maintaining stability in a desired frequency range.

Abstract: The invention relates to a method for preparing a polycarbonate, by mixing a compound having the structure I: ##STR1## and a basic catalyst, and heating the mixture to produce the polycarbonate. The invention also relates to poly(2,2,4,4-tetramethyl-1,3-cyclobutylene carbonate) with an inherent viscosity of at least 0.7 dL/g. The invention also relates to an article made from the polycarbonate and a blend containing poly(2,2,4,4-tetramethyl-1,3-cyclobutylene carbonate).

Abstract: The invention relates to a copolyester containing (a) a dicarboxylic acid component having from about 80 to 100 mole % terephthalic acid or the ester thereof; less than or equal to 20 mole % of an aromatic dicarboxylic acid having up to 20 carbon atoms or the ester thereof; and less than or equal to 10 mole % of an aliphatic dicarboxylic acid or an ester thereof having up to 16 carbon atoms; and (b) a glycol component having from about 25 to 85 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol, from about 15 to 75 mole % ethylene glycol; and less than or equal to 10 mole % of a diol having 3 to 16 carbon atoms, wherein the total mole % of the dicarboxylic acid component is 100 mole % and the total mole % of the glycol component is 100 mole %. The invention further relates to a process for preparing the above-identified copolyester.