Abstract: An apparatus and method of maintaining stability in a servo loop of a disc drive is provided. A dither signal (a single frequency sine wave or a multi-frequency signal) is injected into the servo loop. A servo loop gain error signal is obtained in response to the injected dither signal. A gain of the servo loop is adjusted as a function of the servo loop gain error signal in real-time.

Abstract: Data storage systems and methods for writing data into a memory component and reading data from the memory component are disclosed. By utilizing a high-speed data controller, the systems and methods transfer data at a fast data transfer rate. In one implementation, the memory component comprises a memory controller for managing data within the memory component. The memory controller comprises the high-speed data controller and a data manager. The data manager comprises a compression/decompression engine that compresses and decompresses data and a storage device interface.

Abstract: Using a “reference” sensor, a reference position is detected in a frame of reference that is moving along a predetermined path relative to the reference sensor. The reference position is used to derive a position-dependent indicator of a position-dependent “longitudinal” offset component (i.e. along the path). An output from the target sensor is monitored using a “target window” that is partially based on the position-dependent indicator.

Abstract: A method to improve drive read performance in a disc drive includes powering-up a disk drive, reading reassigned sectors data from a reassign spare pool, and storing the reassigned sectors data in a reassigned cache segment. This method also includes initiating a read request, detecting a reassigned sector within the read request, and determining whether the requested sector can be located in the reassignment cache. If the reassigned sectors are found in the cache, then the method includes transferring the reassigned sector data from the reassignment cache to the read buffer or directly to the requesting host computer. If the reassigned sectors are not found in the cache, then the method includes seeking to the reassignment spare pool to fetch as much reassigned sectors data as the reassignment cache can hold. In another embodiment, the reassigned sectors data stored in a reassignment cache segment is located in a buffer.

Abstract: An apparatus and method for controlling a dynamic system is provided in which primary position control output signals are generated at a position measurement sampling frequency. Intermediate position control output signals are generated between the primary position control output signals as a function of the primary position control output signals.

Abstract: A method and system is disclosed for calculating the square root of a number using a fixed-point microprocessor. The method includes employing a binary search to obtain the integer portion of the square root, and calculating a fraction of the square root utilizing the integer portion. The method further includes summing the fractional portion together with the integer portion to yield the square root. Also disclosed is a calculator apparatus for employing the method.

Abstract: A method and apparatus for efficiently calculating notch filter coefficients for a disc drive actuator arm control system is disclosed. In a preferred embodiment, filter coefficients for a z-domain notch-filter transfer function are calculated in fixed-point arithmetic from polynomial interpolations of the non-linear functions that define the coefficients in terms of the notch frequency. These non-linear functions may be derived and interpolated a priori by applying the bilinear transform to an s-domain notch transfer function. Since, in a preferred embodiment, the z-domain transfer function can be expressed as a fraction, the numerator and denominator of the transfer function can be scaled so as to allow the coefficients to be expressed as integers, thus making it possible to calculate the filter coefficients from the aforementioned polynomial interpolations using fixed-point math.

Abstract: A data storage device for retrieving data includes a controllably positionable head and a storage medium having servo information comprising a phase pattern having a first frequency and a PES pattern having a second frequency, the second frequency being different from the first frequency.

Abstract: Method and apparatus for accelerating a multi-phase motor having a rotatable rotor is disclosed. A first commutation state in which the rotor resides is identified, a first position of the rotor within the first commutation state is determined (preferably within one to two electrical degrees), and a travel distance for the rotor to advance from the first position to a second position is determined. An optimized activation time is next determined for utilizing substantially all available motor torque, and a first drive pulse is applied for the activation time to advance the rotor to the second position. The process is repeated until an intermediate velocity is reached, after which back electromotive force (bemf) commutation is used for control of the motor. The apparatus includes a controller programmed with routines that utilize speeds and accelerations of the motor in accordance with basic Newtonian laws to determine optimized activation times.

Abstract: A method and apparatus for transducer position detection uses inert contact surfaces to engage an actuator temporarily. The inert contact surfaces are part of an apparatus that also includes an optical sensor such as a retroreflector or diffraction grating. The assembly is thus configured to permit multiple uses while exerting a near-zero net torque about the length of the arm that supports the transducer. This is useful where there is a temporary need for especially precise position control, such as when servowriting a data storage media surface.

Abstract: A shared state controller is provided that optimizes for settle, rotational vibration, and track following. The shared state controller uses the same state update equation with different output equations for settle and track follow. Two or more different track follow output equations may also be used. Switching logic determines which output equation to use in the controller. The shared state controller switches between a settle controller and a track follow controller based on the state of the actuator. In addition, the shared state controller may also switch between two or more track follow controllers based upon other parameters.

Abstract: Method and apparatus for accelerating a motor to an operational velocity using a continuous sequence of current limit values derived from a plurality of discrete current limit values. Each discrete current limit value establishes a maximum current magnitude for the motor over a plurality of intermediate velocities less than the operational velocity. Each current limit value in the continuous sequence of current limit values has a different magnitude for each different one of the plurality of intermediate velocities. The continuous sequence of current limit values are preferably derived by generating coefficients of a multi-order polynomial curve in relation to the discrete current limit values, and obtaining the continuous sequence of current limit values in relation to said coefficients. Faster acceleration, reduced current spiking and less acoustic noise during motor acceleration are thereby obtained.

Abstract: A disc drive with a control processor programmed with an execution time dependent command schedule optimization method to effect data throughput with a host device. The disc drive includes a head disc assembly executing commands scheduled by the control processor. The control processor selects and schedules a next optimum command from among commands analyzed by the control processor during a time the head disc assembly is executing a current command. The steps utilized by the control processor to select and schedule the next optimum command include executing a first command with the head disc assembly, determining a computation time for a second command, storing the computation time as a computation time estimate, and using the stored computation time estimate to determine the number of commands in a command queue for analysis to provide a level of command schedule optimization commensurate with the available time.

Abstract: The present invention provides a method of describing defects that requires less memory space than conventional methods. Entries of a first defect table are sorted according to the type of track layout, or zones. They are then grouped into clusters. Each cluster is characterized by a set of new parameters, including a starting sector, a scratch parameter, a span parameter, and an angle parameter. The new parameters are stored in a second table, replacing the corresponding entries in the first table. In this manner, a single entry in the second table replaces one or more entries in the first table with one entry in the first table.

Abstract: A compensation element (317) in a feedforward line in a dual stage control system for a data storage system compensates for the undesired transient motion of a first positioning element (i.e., a coarse actuator). The compensation element is a transfer function that is applied from the first positioning element's control signal (Uv) to a second positioning elements's (306) (i.e., microactuator's) input. The transfer function is defined as formula (I) where ^Vnom (z) is a transfer function model of the nominial portion of the first positioning element, ^Vres (z) is a transfer function model of the resonance portion of the first positioning element, and ^M(z) is a transfer function model of the dynamics of the second positioning element. This feedforward transfer function effectively cancels the resonances of the first positioning element without requiring the inversion of the resonance transfer function.

Abstract: Systems and methods are provided through which the current to a spindle motor of the recording medium of a mass storage device is modulated to avoid anomalies in the operation of mass storage device and reduce power consumption. In the example of a disc drive, the current is modulated to prevent expected or predicted disturbances in the air bearing between a read/write head and the recording medium, and to reduce the power consumption when no disturbances are predicted or expected.

Abstract: A multi-chip package for a computer disc drive. In a preferred embodiment, the multi-chip package (MCP) includes a first die having a buffer function thereon, such as an SDRAM device, and a second die including a channel function and a controller function thereon. The two die are packaged in a single package for placement on a printed circuit board of the disc drive.

Abstract: An equalization filter for counteracting the effects of unwanted resonance modes and noise in the VCM plant. The filter comprises a transfer function derived from a function of the actual VCM plant response and an ideal response, for which the servo controller is designed. The response of the combined equalization filter and the actual VCM plant response substantially adheres to the ideal response. The disc drive includes firmware operable to generate one or more equalization filters for each of one or more heads.

Abstract: An apparatus and method for selecting physical cylinders (cylinders accessible for read/write operations) in a disc drive is provided. The disc drive includes at least one rotatable disc. The disc drive also includes a first head, which is positionable adjacent a first disc surface, and a second head, which is positionable adjacent a second disc surface. The first disc surface has a first plurality of greycode tracks and the second disc surface has a second plurality of greycode tracks. Each greycode track of the second plurality of greycode tracks corresponds to a different greycode track of the first plurality of greycode tracks, thereby forming a plurality of greycode cylinders, with each greycode cylinder of the plurality of greycode cylinders including a pair of corresponding greycode tracks. The physical cylinders are a subset (less than all) of the plurality of the greycode cylinders.

Abstract: An apparatus and method for tracking radially-dependent repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The disc includes multiple tracks. Radially-dependent repeatable run-out control components for at least a subset of the multiple tracks are first determined. The subset of the multiple tracks being boundary tracks of established zones of a disc. Data representative of the radially-dependent repeatable run-out control components for the subset of the multiple tracks is then stored in a table. The stored data representative of the radially-dependent repeatable run-out control components is utilized to interpolate or extrapolate the radially-dependent repeatable run-out control components for tracks within a zone or outside of the zones for which data is known.