Disk level servo write

• US 6,611,396 B1
• Filed: 04/24/2000
• Issued: 08/26/2003
• Est. Priority Date: 04/24/2000
• Status: Expired due to Fees

• Current Assignee: Mobile Storage Technology (WillScot Mobile Mini Holdings Corp.)
• Original Assignee: Mobile Storage Technology (WillScot Mobile Mini Holdings Corp.)
• Inventors: Kermiche, Noureddine, Emo, Bruce D., Squires, John P.
• Primary Examiner(s): Hudspeth, David
• Assistant Examiner(s): TZENG, FRED
• Application Number:
  US09/557,401
• Time in Patent Office: 1,219 Days
• Field of Search: 360/77.04, 360/77.05, 360/75, 360/97.01, 711/162
• US Class Current: 360/77.04
• CPC Class Codes: G11B 5/59633 Servo formatting G11B5/59627, G11B5/59677, G11B5/59683, G11B5/59688 take precedence

Abstract

A method for assembling and operating a fixed media hard disk drive using a disk or a stack of disks on which servo information is pre-written off the drive spindle. The disks are subsequently mounted on the drive spindle and a set of rotationally concentric “virtual tracks” for seeking and following in terms of said pre-written servo tracks are defined. The use of the concentric virtual tracks assures minimal actuator motion during drive operation and increases acceptable offtrack tolerances. The off-spindle, pre-writing of the servo information increases the efficiency of the assembly operation and reduces the clean room burden.

Claims

1. A method for assembling and operating a fixed media hard disk drive using disks on which servo information is pre-written while off the drive spindle of said hard disk drive, which disks are subsequently mounted on said drive spindle and on which are then defined a set of rotationally concentric “

virtual tracks”

for seeking and following in terms of said pre-written servo tracks comprising;

providing a fixed media hard disk;

mounting said disk in a servo track writing assembly dedicated to the writing of servo tracks;

writing said servo tracks on said disk;

transferring said servo-written disk to a disk drive assembly comprising a spindle, a read/write head, a head actuator assembly, and a runout compensator;

mounting said disk on said spindle of said drive assembly;

closing said disk drive assembly and mounting it on a PCB;

testing said disk drive assembly;

defining, during said testing process, a set of virtual tracks on said disk in terms of intersections between said pre-written servo tracks and circular paths of said read/write head, said intersections being obtained by means of a process comprising;

choosing a set of n different radial positions on said disk;

locking onto the written servo track at one of said radial positions;

turning on the runout compensator;

obtaining a position error signal with runout compensation included as a sum of harmonics multiplied by harmonic coefficients k₁ and k₂;

choosing a transition rate, ε

, to provide a smooth and stable transition from the physical track domain to the virtual track domain;

recording harmonic coefficients k₁ and k₂;

defining the position error signal for the virtual track in the virtual track domain;

repeating the previous six steps for each of the remaining radial positions;

creating a table in which all other virtual tracks are defined;

storing said table as a non-volatile memory array;

transitioning the disk drive to the virtual domain.

2. The method of claim 1 wherein the set of n radial positions on the disk is the set of three radial positions consisting of an inside diameter, a middle diameter and an outside diameter of the disk.

3. The method of claim 1 wherein the table is created by linear interpolation between the harmonic coefficients obtained from the n radial positions of the disk.

4. The method of claim 1 wherein higher order harmonics are obtained from the runout compensator and used to define the virtual tracks to a higher order of harmonic accuracy.

5. The method of claim 1 further including a seek mode in the virtual domain, wherein said mode locates a virtual track being sought, the target track, from a present virtual track position and computes a distance between the position of said virtual target track being -sought and a virtual present track position.

6. A fixed media hard disk drive using disks on which servo information has been pre-written off the drive spindle and on which virtual tracks are defined, comprising:

a drive spindle;

a read/write head;

a head actuator assembly;

a runout compensator

a disk mounted on said drive spindle on which has been pre-written a set of servo tracks and on which is now defined a set of rotationally concentric “

virtual tracks;

”

an array stored in non-volatile flash memory defining said “

virtual tracks”

in terms of said pre-written physical servo tracks, said virtual tracks being circular tracks defined by an array of intersections of said read/write head with servo positions on said pre-written tracks and said array of intersections being obtained by an analysis of the harmonic runout components of the pre-written servo tracks using said runout compensator;

a printed circuit board on which the drive assembly is mounted.