Disk initialization method

DETAILED DESCRIPTION The initialization of a disk file with sector servo information involves several complex operations including placement, file control (motor) and clock writing, offset measurement, surface quality measurement, head and amplifier measurement and track writing testing and qualification.
Referring to FIG.
1 the file assembly 10 which is to be initialized is mounted on the base 11 of the servo writer assembly with the product actuator 13 positioning the product heads 14 at the outer crash stop.
The precision servo writer accessing mechanism 15 causes the servo writer head 16 to access the disk surfaces 12 along a precisely aligned radial track.
Although neither product heads 14 nor precision servo writing heads 16 are exactly radial, the product heads can be misaligned by as much as a few degrees whereas the servo writer precision access radially aligns the servo writer head along a track within a few minutes of the exact radial path.
The servo writer heads 16 are positioned by the servo writer head position control 19 and the servo control unit 20 at the expected outer crash stop position.
The clock heads which include clock head 22 and speed heads 23 and 24 are positioned at the clock head band which is radially inward of the disk area accessible by the product heads 14.
The disk file drive motor 26 (FIG.
2) is energized and driven to a nominal angular velocity by motor control circuit 28 and product motor drive 29, wherein the speed is regulated by a signal on line 27 originating from a sensor or shaft encoder.
A single clock track is written which is initiated by clock write control 30 and clock read/write circuits 31 and written by the clock head 22, and the output of this track is used to develop an index.
Using this index speed head 23 starts to write continuously; the other speed head 24 being aligned to the same track position starts to read.
A zero error between the two speed heads is used as a reference to correct the angular velocity to an exact angular velocity to product the required number of transitions on the clock track and to provide the clock reference with a closure error of no more than 10 nanoseconds