Accelerometer-assisted servo writing for disk drives
First Claim
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1. In a disk drive having an inertial sensor disposed on the head thereof, a method for writing servo marks on said disk comprising the steps of:
- a. moving said head to a known radial position;
b. writing one or more servo marks or fractional portions of one or more servo marks on said disk while holding said head at a constant radial position and applying a feedback force to said head, based on movements of said head detected by said inertial sensor, to prevent or minimize changes in said radial position;
c. moving said head to a known radial position;
d. determining the position of said head relative to said known position;
e. applying a combination of accelerating and decelerating forces to said head, guided by said inertial sensor, to move said head radially to a radial position offset relative to said known position;
f. repeating steps b through d until all of said servo marks have been written.
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Abstract
This invention discloses a method for facilitating the writing of sector servo marks on disk drives that makes use of an inertial sensor mounted on the positioning arm of the disk drive. In addition, this patent discloses several operating strategies that enhance the accuracy of the inertial sensor when it is used to write sector servo marks.
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Citations
35 Claims
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1. In a disk drive having an inertial sensor disposed on the head thereof, a method for writing servo marks on said disk comprising the steps of:
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a. moving said head to a known radial position;
b. writing one or more servo marks or fractional portions of one or more servo marks on said disk while holding said head at a constant radial position and applying a feedback force to said head, based on movements of said head detected by said inertial sensor, to prevent or minimize changes in said radial position;
c. moving said head to a known radial position;
d. determining the position of said head relative to said known position;
e. applying a combination of accelerating and decelerating forces to said head, guided by said inertial sensor, to move said head radially to a radial position offset relative to said known position;
f. repeating steps b through d until all of said servo marks have been written. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15)
a. moving said head to a first known location; b. applying a measured accelerating force to said head for a precise period of time;
c. applying a measured decelerating force to said head for a precise period of time until a second known position is reached; and
d. repeating steps a through c until said head precisely stops at said second known position.
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7. The method of claim 6 wherein said first and second known positions are selected from a group comprising the inner diameter of said disk, the outer diameter of said disk and previously written servo marks.
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8. The method of claim 1 further comprising the step of initially calibrating the offset error for said inertial sensor.
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9. The method of claim 8 wherein said calibration step comprises the steps of
a. holding said head in a stationary position; -
b. reading said inertial sensor to determine if any acceleration or velocity is erroneously reported; and
c. offsetting subsequent readings of acceleration and velocity to compensate for said erroneous readings.
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11. The method of claim 10 further comprising the steps of
a. moving said head radially inward or outward; -
b. repeating steps b through e of claim 1; and
c. repeating steps a and b until all servo marks are written on said disk.
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12. The method of claim 11 wherein said step of radially moving said head comprises the steps p of:
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a. reading one or more of said servo marks or fractional portion of said servo marks;
b. determining the position of said head relative to said read servo marks or fractional portions of said servo marks;
c. applying one or more forces to said head to move said head radially.
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13. The method of claim 12 wherein the step of determining the position of said head relative to said read servo marks comprises the step of reading a position error signal from said drive.
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14. The method of claim 12 wherein said step of applying one or more forces comprises the steps of:
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a. applying an accelerating force in the direction of movement to said head for a precise period of time; and
b. applying a decelerating force to said head for a precise period of time.
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15. The method of claim 14 wherein said steps of applying said forces includes the step of obtaining feedback from said inertial sensor to gauge the correct application of force.
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10. In a disk drive having an inertial sensor disposed to measure acceleration forces applied to the head thereof, a method for writing servo marks on said disk comprising the steps of
a. moving said head to a known position; -
b. holding said head at a constant radial position by detecting any radial acceleration of said head using said inertial sensor and applying a feedback force to said head to prevent or minimize said acceleration;
c. writing a servo mark or a fractional portion of a servo mark on said disk;
d. waiting until said disk drive rotates to a spot where the next of said servo marks is to be written;
e. repeating steps b though d until all of said servo marks or fractional portions of all of said servo marks at said constant radial position are written. - View Dependent Claims (16, 17, 18, 19, 20, 21)
a. moving said head to a first known position; b. accelerating said head for a precise period of time;
c. decelerating said head for a precise period of time until a second known position is reached; and
d. repeating steps a through c until said head precisely stops at said second known position.
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19. The method of claim 18 wherein said first and second known positions are selected from a group comprising the inner diameter of said disk, the outer diameter of said disk and previously written servo marks.
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20. The method of claim 10 further comprising the step of initially calibrating the offset error for said inertial sensor.
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21. The method of claim 20 wherein said calibration step comprises the steps of
a. holding said head in a stationary position; -
b. reading said inertial sensor to determine if any acceleration or velocity is erroneously reported; and
c. offsetting subsequent readings of acceleration and velocity to compensate for said erroneous readings.
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22. A self-servo writing disk drive adapted to write its own sector servo patterns, the disk drive comprising:
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a. a magnetic head for writing one or more servo tracks onto a recording medium;
b. an arm for positioning said magnetic head over said recording medium;
c. an inertial sensor for detecting any radial motion of said head relative to one or more reference structures, and for providing a sensor signal indicative of said motion;
d. a motion controller for controlling the motion of said arm so that said arm can move said magnetic head onto one or more known radial positions on said recording medium, and so that at each radial position, said head can maintain said head substantially motionless during a time interval sufficient to allow said head to write one or more servo marks or fractional portions thereof onto said recording medium;
wherein said motion controller includes actuator means for applying, in response to receipt of said sensor signal, a feedback force to said arm so as to compensate for any detected motion of said head as indicated by said sensor signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
a. a stopping mechanism; and
b. a head lifting mechanism.
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25. A disc drive in accordance with claim 24, wherein said stopping mechanism comprises a crash stop.
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26. A disc drive in accordance with claim 22, wherein each of said servo tracks have a radius ranging from an innermost radius to an outermost radius, and wherein said one or more reference structures comprise at least one of:
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a. a crash stop located on said recording medium at said innermost radius;
b. a crash stop located on said recording medium at said outermost radius; and
c. a head lifting mechanism located on said recording medium at said outermost radius.
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27. A disc drive in accordance with claim 22, wherein said one or more servo tracks have substantially annular configurations, and are concentrically disposed relative to each other.
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28. A disk drive in accordance with claim 22, wherein said inertial sensor comprises:
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a. a frame structure;
b. a proof mass suspended with respect to said frame structure;
c. sensing means for sensing a displacement of said proof mass with respect to an equilibrium position of said proof mass relative to said frame structure;
d. force feedback means for applying, in response to the sensed displacement, a feedback force to said proof mass so as to restore said proof mass to said equilibrium position.
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29. A disc drive in accordance with claim 28, further comprising means for calibrating and removing offset error in said inertial sensor, including:
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a. means for maintaining said head substantially motionless with respect to at least one position reference item until any vibrations of said head and said arm are substantially eliminated and said head and said arm reach a substantially stationary state characterized by substantially zero velocity and substantially zero acceleration; and
b. measurement means for measuring at least one of the velocity, and acceleration of said proof mass of the inertial sensor while said head is in said substantially stationary state; and
c. means for subtracting from subsequent readings of said inertial sensor any non-zero values of said velocity and said acceleration measured by said measurement means.
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30. A disc drive in accordance with claim 29, wherein said offset error is an offset error in at least one of the acceleration, velocity, and position of said proof mass relative to said frame structure.
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31. A disc drive in accordance with claim 29, wherein said position reference item comprises at least one of:
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a. a crash stop; and
b. a sector servo mark written on said recording medium.
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32. A disc drive in accordance with claim 28, further comprising calibration means for calibrating a scale factor error in said inertial sensor, said calibration means including;
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b. means for moving said head to a first predetermined location;
c. means for applying a known accelerating force to said head during a first time interval;
d. means for applying an equal and opposite decelerating force to said head during a second time interval until said head contacts a second predetermined location, said second time interval being less than said first time interval;
e. means for computing said scale factor error by determining the time point at which said head contacts said second predetermined location, and comparing said time point with a predicted time point; and
f. means for adjusting the scale factor of said inertial sensor to compensate for said computed scale factor error.
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33. A disc drive in accordance with claim 22, wherein said arm is rotatably and pivotably mounted about a pivot point.
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34. A disc drive in accordance with claim 22, wherein said magnetic head is affixed onto a distal end of said arm.
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35. A disc drive in accordance with claim 22, wherein said inertial sensor is mounted on at least one of said arm and said head.
Specification