Seagate Technology Incorporated

Travis Eugene Ell

John Christopher Morris

Roger Alan Resh

Arnold George Slezak

Virat Thantrakul

David Christopher Pruett

Robert T Bradbury

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.

PQ enhanced dual stage servo controller

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.

Minimizing milli-actuator reactive impulse and excessive power current

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.

Digital division device and method using a reduced-sized lookup table

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.

Observer based dual stage servo controller with gain boost to accomodate rotational vibration

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.

PQ enhanced observer based dual stage servo controller

Piezoelectric elements or similar microactuators perform fine positioning in a system including at least two masses bendably coupled to a larger body. A servo controller receives a position signal from a sensor on the first mass, from which it generates a signal to control microactuators coupling other masses to the body. The movement of the other masses thereby exerts a controlled reactive force upon the body and upon the first mass. Examples include disc drive systems in which the reactive forces are used to counteract one or more unwanted excitations in an actuator body or actuator arm.

Microactuator-induced reactive forces for fine positioning a sensor

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.

Microactuator assisted seek and hysteresis correction method and apparatus for a disk drive

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.

Accelerated servo control calculations method and apparatus for a disc drive

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.

Adaptive h-infinity hardware controller for disc drive actuator control

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.

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Oklahoma City, OK, United States of America

Travis Eugene Ell