Abstract: Disclosed is a disk drive having a disk, a masked read-only memory (ROM) device, a reprogrammable nonvolatile memory device, and a microprocessor for executing program code. The disk has a magnetic data storage surface with embedded servo wedges for defining data storage tracks including reserve tracks. The masked ROM device stores program code for implementing a spindle motor controller, program code for implementing a portion of a servo controller for track following along a data storage track, and program code for implementing a portion of a disk controller for controlling writing disk data to and reading disk data from the reserve tracks. The reprogrammable nonvolatile memory device stores data parameters relating to the disk drive's configuration. The reserve tracks store program code for implementing a cache control system for controlling caching of disk data in a cache memory.

Abstract: Disclosed is a control system for processing sampled servo data in a disk drive. The control system includes a microprocessor and a servo processing accelerator circuit for performing operations on the sampled servo data while the microprocessor is executing firmware code. The accelerator circuit supports the use of a higher servo bandwidth thus allowing a higher track density resulting a greater storage capacity for the disk drive. Also, the accelerator circuit relieves the microprocessor of the ordinary servo processing function. Thus, the microprocessor's limited processing capacity to be directed to other controller and interface functions of the disk drive. Only under unusual conditions, such as a write-unsafe (WUS) limit exception, does the microprocessor need to direct processing capacity to the servo processing function. Further, the accelerator circuit may be a decreased response time after reading the servo data from the disk.

Abstract: A servo controller controls the servo system in a disc drive. A proportional integrator component receives the target track signal indicative of a target track and a measured track signal indicative of actual or measured data head position. During seek mode, the proportional integrator provides an output signal based on the measured track signal and the target track signal. A profile generator component provides a profile signal based on the output signal from the proportional integrator. A coarse actuator is driven based on the profile signal. A filter component is coupled to the profile generator and filters the profile signal to provide a filtered profile signal. The fine actuator is driven based on the filtered profile signal.

Abstract: An information handling system, such as a disc drive, includes a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base, with multiple movable mill-actuator arms mounted on one portion of the actuator assembly. Attached to an end of the actuator is a voice coil which forms a portion of a voice coil motor. Magnets attached to the base form the other portion of the voice coil motor. A current driver for the voice coil delivers an amount of current to the voice coil to move the actuator assembly. Attached to another end of the actuator assembly is one or more transducers. In order to minimize the disturbance of a seeking milli-actuator, the operation to be executed is to cause the first milli-actuator to return slowly to its rest or zero position. A rate of return control circuit is implemented to drive a milli-actuator such that a milli-actuator at a non-zero or non-rest position will be returned to a rest position at a rate slower than a seeking milli-actuator.

Abstract: Devices and methods are provided for estimating a high-precision quotient using a smaller-than-conventional lookup table. The devices include a numerator register feeding a numerator value (as a succession of bits or words) into a forward signal path. The forward path includes a partial quotient generator, an accumulator, and a latch. The devices further include a feedback signal path emerging from the latch output, undergoing division by bit-shifting, and terminating as an input to the accumulator. A multiple divide implementation for use in a particular servo control system is also presented.

Abstract: The present invention includes a servo control system for controlling a dual stage actuator in a disc drive. The disc drive includes a data head for accessing information on a disc surface, and the dual stage actuator includes a coarse actuator and at least one fine actuator. The control system includes a fine actuator driver and a coarse actuator driver for driving the fine and coarse actuators, respectively. The control system also includes an observer which receives the coarse and fine actuator input signals and estimates a response of the coarse and fine actuators. A gain boost circuit is coupled to the fine and coarse actuator drivers and introduces a gain boost to reduce track following error in a desired frequency range.

Abstract: The present invention includes a servo control system for controlling a dual stage actuator in a disc drive. The disc drive includes a data head for accessing information on a disc surface, and the dual stage actuator includes a coarse actuator and at least one fine actuator. The control system includes a fine actuator driver and a coarse actuator driver for driving the fine and coarse actuators, respectively. The control system also includes an observer which receives the coarse and fine actuator input signals and estimates a response of the coarse and fine actuators.

Abstract: Apparatus and method for positioning a head in a disc drive using a dual stage actuator having a primary actuator motor for coarse head positional control and a microactuator motor for fine head positional control. The microactuator motor includes a strain gauge affixed to a piezoelectric transducer measuring actual dimensional change of the microactuator motor resulting from response by the piezoelectric transducer to a request for head repositioning. A closed loop servo control circuit generates control inputs for the dual stage actuator to carry out track following and seek operations while adjusting head position by correcting piezoelectric transducer hysteresis and reducing seek and settle times.

Abstract: Apparatus and method for generating control inputs for a disc drive dual stage actuator having primary and secondary actuator motors used to maintain a head adjacent a rotatable disc surface. An h-infinity hardware controller generates the control inputs in relation to an actual position signal, a desired position signal and a unique set of coefficients for each selected head. The coefficients are selected by obtaining an output response for each head, selecting the coefficients in relation to the output response for each head, and storing the coefficients in a nonvolatile memory location of the disc drive. The appropriate set of coefficients are thereafter loaded as each head is selected in turn during normal drive operation.

Abstract: Apparatus and method which provide accelerated servo control value calculations for a control processor controlling an actuator maintaining a head adjacent a rotatable disc f a disc drive. A dedicated multiply-accumulate hardware core of a servo micro engine calculates sum-of-products terms common in servo control loops. The multiply-accumulate hardware core uses a pipeline with stages for fetch, read, multiply, accumulate, and write-back as an arithmetic core to fully utilize all of the hardware during every servo interval. Feeding this arithmetic core is a dedicated state memory, from which a first signed servo state and a second signed servo state are read and where calculation results may be optionally written. Another, independent, coefficient memory provides predetermined coefficients used in resolving servo control loop algorithms. A final dedicated instruction memory provides shifter control values and the addresses of the states and coefficients.

Abstract: Apparatus and method for improved servo control in a disc drive. The disc drive includes a rotatable disc, a moveable actuator which supports a head adjacent the disc, and a stationary active magnetic bearing assembly which uses bearing coils to levitate the actuator. An active magnetic bearing control circuit applies currents to the bearing coils, and a servo control circuit applies current to an actuator motor to position the head with respect to the disc. The active magnetic bearing control circuit outputs a disturbance signal when a disturbance affects the relative positioning of the actuator and the bearing assembly, and this disturbance signal is fed forward into the servo control circuit. Conversely, the servo control circuit provides a seek expectancy signal to the bearing control circuit to enable the bearing control circuit to compensate for torque forces applied by the actuator motor.

Abstract: A velocity estimator for a voice coil motor driven actuator is implemented by integrating coil current to generate the estimated velocity and integrating the estimated velocity signal to produce an estimated position signal. The estimated position signal and a measured position signal are compared and the derived error signal is applied as negative feedback to the summing junctions at the inputs of each of the integrators. The use of an integrated signal results in reduced noise influence on the position error signal which, in the environment of a data disk drive, results in more reliable recording of track crossings and the ability to meet rigid product specifications using simple servo patterns.