Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Patent
1992-07-07
1997-07-08
Young, W. R.
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
360 7708, 360 7809, G11B 5596
Patent
active
056467974
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to servo control systems which may be used in controlling the head positioning actuators in storage devices such as disk drives. More specifically, the invention relates to digital servo control systems involving efficient implementations of tracking and seeking servo control methods.
BACKGROUND ART AND BACKGROUND OF THE INVENTION
Various servo control systems are known in the art. U.S. Pat. No. 3,458,785 (Sordello) discloses an early example of a servo control system employing quadrature signals for providing position and velocity information, the system having fine and coarse positioning control algorithms. U.S. Pat. No. 4,135,217 (Jacques et al.) discloses a system which compensates for repeatable errors such as wobble of a disk, with stored "run-out" information being used to compensate for the errors. U.S. Pat. No. 4,412,161 (Cornaby) generally discloses a digitally implemented recursive servo control system. U.S. Pat. No. 4,486,797 (Workman) discloses a servo control system in which a preprogrammed velocity profile is used. U.S. Pat. No. 4,783,705 (Moon et al.) discloses an embedded sector servo system divided into separate track and seek control systems, the system including an automatic gain control function. U.S. Pat. No. 4,788,608 (Tsujisawa) discloses a control system for positioning read/write heads over a non-circular track, by using harmonics of the rotation period of the disk. U.S. Pat. No. 4,835,632 (Shih et al.) discloses a servo control system having different sampling and control frequencies for tracking and seek operations, the system apparently scaling or normalizing certain values during operation. U.S. Pat. No. 4,835,633 (Edel et al.) discloses a servo control system involving values calibrated for voice coil motor acceleration as a function of radial position using a polynomial curve fit.
U.S. Pat. No. 4,879,612 (Freeze et al.) discloses a servo control system claiming a purely digital seek mode but a hybrid tracking mode, the system using track identity information and sample testing to reduce errors. U.S. Pat. No. 4,890,172 (Watt et al.) discloses an automatic gain calibration system for a disk drive servo system. U.S. Pat. No. 4,907,107 (Sakurai) discloses a low level circuit for generating signals corresponding to sampled magnetic pulses. U.S. Pat. No. 4,914,644 (Chen et al.) discloses a servo control system including a model of coil current involving comparison of a velocity error to a predetermined value during long seeks, when the power amplifier is saturated. U.S. Pat. No. 4,914,725 (Belser et al.) discloses a servo control system including a "piggy-back" construction including a fine positioner carried by a coarse positioner, the dynamic range of the fine positioner being increased momentarily at the time of track capture, this patent naming a common inventor with an inventor of the present patent application. U.S. Pat. No. 4,942,564 (Hofer et al.) discloses a gain compensation system in which a test signal is introduced to determine the system's response for comparison to a previously stored value. U.S. Pat. No. 4,954,909 (Sengoku) discloses a system for determining movement of a recording head, especially for determining when it has hit a disk surface. U.S. Pat. No. 5,038,333 (Chow et al.) discloses a track-seeking apparatus having a track crossing detector for providing position information, this patent naming an inventor who is also a named inventor in the present patent application.
European Patent Application 0,390,467 (Ogino) discloses a digital servo control system in which certain variables are not calculated when an error value is substantially zero. Japanese Patent Document 63-316380 discloses a control system having a plurality of servo bit sample periods.
These patents, as well as any documents cited in this patent application, are incorporated herein by reference in their entirety.
In the field of magnetic disk drives, servo systems are required to accurately position read/write heads over a given substantially
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Frederick Thomas James
Kadlec Ronald James
Kelley Paul Henry
Weilbacher Philip Saxton
Habermehl James L.
Rodime PLC
Young W. R.
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