Seagate Technology Incorporated

Jeffrey A Heydt

David R Street

Housan Dakroub

Christopher L Hill

Shawn Alan Wakefield

Ghassan M Abdelnour

Stuart Kevin Francis

Alfredo Gay Sam

James W DuLaney, Jr

James Brian Ray

Nicholas Swezey

Method and apparatus for controlling a brushless dc motor, such as the type used in a data storage device to rotate data storage media. A sequence of drive pulses is applied to rotate the motor. The sequence is switched from first to second motor commutation states at a time determined in relation to changes in elapsed time between successive pulses in the sequence. Each drive pulse has a duration established in relation to an inductance of the motor, and is separated from adjacent pulses by an intermediate delay of predetermined value. A peak elapsed time interval between successive pulses is identified, and the next commutation state is switched in at a selected time after the peak time interval. The sequence preferably accelerates the motor from rest to an intermediate velocity, after which back electromotive force (bemf) commutation is used to accelerate the motor to a final operational velocity.

Closed-loop rotational control of a brushless dc motor

Method arid apparatus for accelerating a multi-phase motor having a rotatable rotor are disclosed. The method incorporates use of a motor control circuit to predict a subsequent loss of frequency lock between the motor control circuit and a motor while the motor control circuit and the motor remain frequency locked, and based on the prediction, steps to avert a loss of frequency lock during acceleration. The apparatus includes at least a motor control circuit detecting frequency lock wit a motor when a motor signal falls within a timing window, and while frequency locked, predicting a subsequent loss of frequency lock based on a relative position of the motor signal within the timing window

Predicting loss of frequency lock between a motor control circuit and a motor

Method and apparatus for accelerating a motor from an intermediate velocity to a final operational velocity. The motor is accelerated from rest to the intermediate velocity through application of fixed duration drive pulses to the spindle motor. Once the motor reaches the intermediate velocity, commutation circuitry and back electromotive force (bemf) detection circuitry use detected bemf from the motor to electronically commutate the motor to accelerate to the final operational speed. A phase lock oscillator (PLO) attempts to acquire frequency lock for the motor. A control circuit measures the current in the motor to evaluate the effectiveness of the phase lock. If the measured current is found to be above a threshold value, the motor is restarted.

Monitoring current in a motor during acceleration to verify motor frequency lock

A method for determining whether a data storage device read/write head is a low-flying read/write head or a non low-flying read/write head. A disc attached to a spindle motor is accelerated to an operating rotational velocity, the head is positioned over a portion of the disc non-accessible to customer data and a data pattern of selected frequency is written. A magnetoresistive element of the is biased and the data pattern is read while the disc is decelerated to a predetermined rotational velocity threshold. Occurrence of a read signal landing signature comprising readback signal amplitude modulation prior to reaching the predetermined rotational velocity threshold identifies the head as a low-flying head. Contrawise, non-occurrence of the read signal landing signature prior to reaching the predetermined rotational velocity threshold signifies the head as a non low-flying head.

Low flying head detection using readback signal amplitude modulation

Method and apparatus for detecting head landings on a data zone of a data storage disc. A disc drive includes an actuator which controllably positions a head adjacent a disc and nominally retracts the head to a parked position when the drive is deactivated. The actuator moves in response to current applied to an actuator coil immersed in a magnetic field. During disc drive initialization, the disc is accelerated to a velocity sufficient to allow the head to be aerodynamically supported over the disc, and current is passed through the actuator coil to urge the head toward the parked position. The current is monitored to detect generation of a back electromotive force (bemf) voltage induced by movement of the coil. An error condition is logged indicating that an initial position of the head was over a data zone of the disc when bemf voltage is detected.

Detecting head landings on a data zone of a data storage disc

Apparatus and method for reducing nonlinearities in a position error signal (PES) of a disc drive data handling system. The disc drive data handling system includes a disc recording surface having a number of tracks and a controllably positionable read/write head. A servo circuit generates a sequence of PES samples indicative of head position with respect to a selected track using servo position data samples transduced from the selected track and a first set of compensation values selected to reduce nonlinearities in said PES samples. The PES samples are combined with the first set of compensation values to generate an updated set of compensation values. This process is preferably repeated a number of iterations to converge to a final set of compensation values which provide a substantially linear PES across the radial width of each track.

Reducing position error signal nonlinearity through iterative calibration of a compensation table

Method and apparatus for accelerating a disc drive spindle motor to an operational velocity at which data are transferred between a host device and a disc rotated by the spindle motor. The spindle motor is initially accelerated from rest to an intermediate velocity at which sufficient back electromotive force (bemf) is generated by the rotation of the spindle motor to enable commutation circuitry of the disc drive to time the application of drive pulses to the spindle motor. The spindle motor is subsequently accelerated from the intermediate velocity to the operational velocity by applying a velocity dependent reference profile which establishes a sequence of reference levels to control the flow of current through the spindle motor during acceleration. The sequence of reference levels have different magnitudes at different velocities of the spindle motor between the intermediate velocity and the operational velocity.

Velocity dependent reference profile for spindle motor acceleration control

Method and apparatus for initializing a disc drive to bring a spindle motor to a final, operational velocity after a disc drive processor reset condition. The spindle motor is rotated using electronic commutation and back electromotive force (bemf) detection. Upon initialization of the disc drive, a control circuit checks for the presence or absence of detected bemf. The absence of bemf indicates the spindle motor is either at rest or is rotating at a relatively low velocity. In the absence of bemf, the electrical rotational position of the spindle motor is determined, a short braking pulse is applied to the motor, and rotation of the spindle motor is detected in relation to changes in the electrical rotational position. Further breaking pulses are applied until no apparent change in electrical rotational position is detected, after which the spindle motor is accelerated from rest to the final, operational velocity.

Spindle motor initialization after a control processor reset condition in a disc drive

Method and apparatus for accelerating a disc drive spindle motor from rest to a final operational velocity. During a low gear mode, the spindle motor is accelerated from rest to a first velocity through application of fixed duration drive pulses to the spindle motor. A high gear mode is next employed to accelerate the spindle motor from a first velocity to an intermediate velocity. Variable duration drive pulses are applied to the spindle motor each having a duration selected as a percentage of the duration of the most recently detected commutation period of the spindle motor. Once the spindle motor reaches the medium speed, commutation circuitry and back electromotive force (bemf) detection circuitry use detected bemf from the spindle motor to electronically commutate the motor to accelerate to the final operational speed.

Closed loop spindle motor acceleration control in a disc drive

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. Attached to one end of the actuator assembly is one or more transducers. The disc includes data areas and servo areas written at angular locations on the disc. The disc drive also has a disc drive controller which includes a motor speed controller, a write gate controller, and a device for predicting the disc speed at an upcoming servo and disabling the write gate if the predicted disc speed is outside a selected range of disc speeds. The device for predicting the disc speed may further include an abort signal generator that produces an inhibit write gate signal in response to the predicted disc speed being outside the selected range of disc speeds.

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Oklahoma City, OK, United States of America

Jeffrey A Heydt