Abstract: The disclosure is related to an apparatus and methods of suppressing seek repeatable runout. In a particular embodiment, a servo loop is disclosed. The servo loop includes a seek signal generation component that generates a seek trajectory acceleration signal. The servo loop also includes a STRRO suppression component that is coupled to the seek signal generation component. The STRRO suppression component injects STRRO suppression signals into the seek trajectory acceleration signal and outputs an STRRO suppressed seek trajectory acceleration signal.

Abstract: The disclosure is related to an apparatus and methods of suppressing seek repeatable runout. In a particular embodiment, a servo loop is disclosed. The servo loop includes a seek signal generation component that generates a seek trajectory acceleration signal. The servo loop also includes a STRRO suppression component that is coupled to the seek signal generation component. The STRRO suppression component injects STRRO suppression signals into the seek trajectory acceleration signal and outputs an STRRO suppressed seek trajectory acceleration signal.

Abstract: A method and apparatus position a plurality of data heads relative to a plurality of surfaces of at least one disc in a disc drive. One of the plurality of data heads corresponds to each of the plurality of surfaces. The data heads are provided for writing information to the surfaces and reading information from the surfaces. Each of the data heads may be simultaneously positioned relative to the corresponding surfaces using the embedded servo information. Information can be simultaneously transferred relative to the corresponding surfaces using the plurality of data heads. Uninterrupted sequential data transfers may also be executed without servo overhead. Further, an apparatus is provided for accomplishing such servo control, as is a method of accomplishing model-based servo control.

Abstract: An apparatus and method for improved servo control in a disc drive. A rotatable disc has first, second, third and fourth radially staggered servo burst patterns which define a plurality of concentric tracks. An actuator assembly supports a transducing head adjacent the tracks. A servo circuit combines respective at least third order polynomial functions of burst signals from the first and second, and third and fourth, burst patterns to generate a continuous function position error signal (PES) with normalized absolute magnitudes of 0 when the head is positioned at track centers, 0.5 at track boundaries, and 0.25 at quarter-track locations, and with substantially linear slope therebetween. The servo circuit applies current to an actuator motor to position of the head relative to a selected track in relation to the magnitude of the PES.

Abstract: Method and apparatus for evaluating programming used by a programmable processor device in a disc drive to carry out servo control of a head with respect to a rotatable disc. The programming is first generated as a series of instructions executable by the programmable processor device. Processor emulation software is used to simulate execution of the instructions in a computer. A dynamic model of electrical and mechanical portions of the disc drive is generated using plant simulation software. A dynamic linking program is configured to synchronize and transfer data between the processor emulation software and the plant simulation software. All three programs are thereafter simultaneously executed in the computer to evaluate realtime operation of the programming.

Abstract: A multi-task system employs a single interrupt occurring at fixed time intervals to initiate the control functions. The actuator control, servo control and spindle control routines are operated on a priority basis so that if a control function having a high priority is not ready to be executed, the processor immediately performs execution of the next available control function. More particularly, the spindle control process is operated in the foreground with the actuator control and servo control routines operated on an interrupt basis of the spindle control routine. Upon receipt of the interrupt signal, priority is first given to an actuator control routine for execution. Upon completion of the actuator control routine, or if the actuator control is not ready to be executed, access is given to a servo control routine. At the conclusion of the servo control routine, the interrupt exits to the spindle control routine.

Abstract: A method for adapting acceleration and deceleration of a disc drive transducer during movements between initial and target tracks on a disc surface to the maximum current available to drive an actuator whereon the transducer is mounted. During acceleration of the transducer, while the actuator current is substantially a maximum, the current supplied to the actuator coil is measured and a scale factor is determined as the square root of the ratio of the maximum current supplied to the actuator and a nominal current from which a velocity profile, used to effect velocity control of the movement, has been predetermined.

Abstract: Apparatus and method for improving vibration and mechanical shock response of a system through the use of discrete-time sliding mode control with variable parameters are disclosed. A servo circuit for positioning a control object (such as a head of a disc drive) includes a reference generator generating position and velocity references, an observer generating position and velocity estimates, and circuitry for determining position and velocity errors therefrom. Variable position and velocity gains are applied to the position and velocity errors, respectively, the position and velocity gains varying with respect to at least the magnitudes of the position errors.

Abstract: A method for compensating for position and component induced variations in the acceleration and deceleration capabilities of a voice coil actuator in a disc drive, comprising the steps of dividing the discs radially into a plurality of zones, testing the acceleration and deceleration capability of the disc drive in each zone by performing specially controlled seeks in both inward and outward directions in each zone, comparing the result of these specially controlled seeks with a calculated nominal or desired result, and calculating a compensation factor for each zone which is applied by the servo system to all subsequent seek and track following operations.

Abstract: A method for following a selected data track on a selected data surface of a disc drive of the type having a dedicated servo system in which guiding of data heads to follow data tracks on data surfaces is effected by positioning an actuator upon which the data heads are mounted in relation to the location of a servo head, also mounted on the actuator, with respect to servo tracks on a dedicated servo surface. The data tracks are organized into cylinders, each containing a servo track, and a selected data track is accessed by seeking to an optimum servo track displaced from the servo track in the cylinder containing the data track by an integral number of track spacings selected to compensate for misalignments greater than a track spacing between the data and servo heads. Data track following is then effected by offsetting the servo head from the optimum servo track to compensate for misalignments of less than a track spacing between the data and servo heads and tracks.

Abstract: Method and apparatus for dynamically compensating for servo burst measurement offsets in a disc drive. A first type of servo position error signal is used during a compensation routine to position a head adjacent a selected track on a disc, the first type of servo position error signal determined from servo burst signals read by the head from servo position fields on the disc. A second type of servo position error signal is also generated from the servo burst signals and the difference between selected values of the second type of servo position error signal is compared to an acceptance limit. Compensation terms are incrementally added to the servo burst signals used to generate the second type of servo position error signal until the difference is below the acceptance limits. Thereafter, the compensation terms are stored and retrieved during normal track following operations to generate a compensated servo position error signal.

Abstract: A method and apparatus for testing for mechanical defects in a disc drive during manufacturing test is disclosed. Resonances in the disc drive are excited by injecting a sinusoidal test signal of known magnitude and frequency into an incoming servo position error (SPE) signal in the servo loop to provide a modified SPE. While the test signal is injected, the modified SPE is sampled and filtered to characterize the test frequency in the modified SPE which is compared to a resultant frequency characterized in the incoming SPE. The presence of resonances in the disc drive structure will result in an increase in the gain of the loop as indicated by the characterized resonant frequencies from the incoming and modified SPE. When the gain exceeds predetermined criteria, an error flag is set indicative of a failure condition for the disc drive, enabling the disc drive to be removed from test for subsequent remedial actions.

Abstract: A method for effecting seeks of a transducer head across a data storage disk wherein the head is accelerated over a first sequence of time intervals and decelerated over a second sequence of time intervals. In each time interval of the first sequence, the head is accelerated in relation to the difference between the actual head velocity and a current demand velocity that is determined by incrementing the demand velocity for the previous interval by an amount that is a fraction of the difference between the previous demand velocity and a stored profile velocity selected in accordance with the current location of the head. In each time interval of the second sequence, the head is decelerated in relation to the difference between the actual head velocity and a stored profile velocity selected in accordance with the current location of the head.

Abstract: A process is provided for compensating for offset in the actuator current of the servo system of a disc drive. A typical disc drive includes a power amplifier providing actuator current to the actuator coil of the drive. A sensing resistor is responsive to the actuator current to provide a feedback signal representative of the magnitude of the actuator current, the feedback signal being provided to the power mechanism to derive the actual actuator current. By the present technique, offset in the actuator current is compensated by operating the transducer to move at predetermined constant velocities (for example, the maximum velocities) in first and second opposite directions across the surface of the disc and by measuring the resulting actual velocities. The feedback signal is adjusted based upon any difference between the actual velocities measured in the first and second directions.

Abstract: A multi-task system employs a single interrupt occurring at fixed time intervals to initiate the control functions. The actuator control, servo control and spindle control routines are operated on a priority basis so that if a control function having a high priority is not ready to be executed, the processor immediately performs execution of the next available control function. More particularly, the spindle control process is operated in the foreground with the actuator control and servo control routines operated on an interrupt basis of the spindle control routine. Upon receipt of the interrupt signal, priority is first given to an actuator control routine for execution. Upon completion of the actuator control routine, or if the actuator control is not ready to be executed, access is given to a servo control routine. At the conclusion of the servo control routine, the interrupt exits to the spindle control routine.

Abstract: A method for compensating for position and component induced variations in the acceleration and deceleration capabilities of a voice coil actuator in a disc drive, comprising the steps of dividing the discs radially into a plurality of zones, testing the acceleration and deceleration capability of the disc drive in each zone by performing specially controlled seeks in both inward and outward directions in each zone, comparing the result of these specially controlled seeks with a calculated nominal or desired result, and calculating a compensation factor for each zone which is applied by the servo system to all subsequent seek and track following operations.