Appeal No. 2002-2027 Page 2
Application No. 09/209,304
Magnets, which form the other portion of the VCM, are attached to the base. A current
driver delivers current to the voice coil to move the actuator assembly. The force
constant is a multiplier applied to an amplifier so that the output current to the voice coil
products a velocity output replicating the desired velocity output. (Spec. at 20.)
In the past, asserts the appellant, a force constant was calibrated during the
deceleration phase of long seeks, e.g., "seeks of 1000 tracks or more." (Id. at 5.) If
only short seeks were requested, he adds, the force calibration could drift out of the
correct calibration, (Appeal Br. at 4), and "[s]eek errors could result." (Id.)
In contrast, the invention determines a force constant during the acceleration
phase of the movement of an actuator assembly. A velocity error signal is produced by
comparing the desired velocity of the actuator assembly to the measured velocity during
a linear mode of the associated current driver. The error signal can be based on one
point in time or over a period of time. (Id. at 20.) By calibrating the force constant
based upon the acceleration phase, explains the appellant, the force constant can be
recalibrated during short seeks, e.g., seeks of as little as 20 tracks, (Appeal Br. at 4),
"to produce real time updates to correct the force constant before the changes in the
parameters that effect the force constant cause the value to drift out of calibration."
(Spec. at 14.)
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