TM Servo Technology for TrueTrack High TPI Disk Drives Authors - - PowerPoint PPT Presentation

▶
tm servo technology for truetrack high tpi disk drives
SMART_READER_LITE
LIVE PREVIEW

TM Servo Technology for TrueTrack High TPI Disk Drives Authors - - PowerPoint PPT Presentation

Nov 02, 2023 156 likes •406 views

TM Servo Technology for TrueTrack High TPI Disk Drives Authors Sri-Jayantha, Dang, Sharma IBM, T. J. Watson Research Center, NY,USA and Yoneda, Kitazaki, and Yamamoto IBM, Fujisawa HDD Development, Japan APMRC, Tokyo, Japan Nov. 7, 2000

slide-1
SLIDE 1

TrueTrack-APMRC-2000

TrueTrack

TM Servo Technology for

High TPI Disk Drives Harmonic Error Sources TrueTrack Servo Algorithm Digital Filter Implementation Autonomous State Propagation Mutiple Harmonics Performance Summary

Authors Sri-Jayantha, Dang, Sharma IBM, T. J. Watson Research Center, NY,USA and Yoneda, Kitazaki, and Yamamoto IBM, Fujisawa HDD Development, Japan APMRC, Tokyo, Japan

  • Nov. 7, 2000
slide-2
SLIDE 2

TrueTrack-APMRC-2000

Spindle Vibration due to Imbalance

Spindle Imbalance

Disk-Shift due to Shock Disk-Warp due to Stress High-TPI Challenges

Figure-1

Harmonic Error Sources at High TPI

slide-3
SLIDE 3

20 ms

Problem

Conventional Digital Servo

1/2 Track Pitch Position Error

Solution

with Novel TrueTrack Servo

1/2 Track Pitch Position Error

US Patent 5,608,586

TrueTrack-APMRC-2000

Impact of TrueTrack

TM Servo Technology

Track Center

slide-4
SLIDE 4

TrueTrack Servo Algorithm

slide-5
SLIDE 5

VCM

Disk Shift due to Shock

PES Digital Servo Controller DAC Head Position Demodulator Track Position +

  • 10

20 30 40 50 60 70 80 Excessive Runout After a 1000-Track Move 1/4

  • 1/8
  • 1/4

PES (Trk) Time (ms) Conventional Digital Servo

ADC

Seek Track-Follow Settle Track-Follow

Figure-2

Conventional Servo with a Disk Shift

TrueTrack-APMRC-2000

slide-6
SLIDE 6

120 Hz dB Frequency

Current

Servo Controller

+

High Gain Digital Filter

PES

30 dB

Runout is Suppressed With a High Gain Digital Filter But has Settleout Penalty

Seek Track-Follow Settle Track-Follow

10 20 30 40 50 60 70 80 Time (ms)

Schematic Output of the filter HDD

Steady State

Figure-3 TrueTrack-APMRC-2000

Effect of a High Gain Filter

slide-7
SLIDE 7

Current

Servo Controller

+ PES

delay delay

(B-E) (C-F)

  • F
  • E

+ +

M(n) M(n-1) M(n-2)

(A-1)

Initial State

High Gain Digital Filter

Runout Suppressed with No Settleout Penalty Time (ms) With Optimally Initialized Filter

10 20 30 40 50 60 70 80

HDD p(n) Y(n)

Figure-4 TrueTrack-APMRC-2000

Optimally Initialized Filter

slide-8
SLIDE 8

Filter Structure

slide-9
SLIDE 9

A p(n) Y(n) delay delay C B p(n-1) p(n-2) delay delay

  • F
  • E

Y(n-1) Y(n-2) + + Q(n) delay delay B C

  • F
  • E

+ + p(n) R(n) Y(n) R(n-1) A R(n-2)

Y(n)=A p(n)+B p(n-1)+C p(n-2) - E Y(n-1) - F Y(n-2) Direct-Form 1 2

Figure-6

delay delay (B-E)/(A-1) (C-F)/(A-1)

  • F
  • E

+ + p(n) M(n) M(n-1) M(n-2) Y(n) + V(n) A-1

Bias Free Form 3

TrueTrack-APMRC-2000

Filter Structure

slide-10
SLIDE 10

10

1

10

2

10

3

  • 60
  • 40
  • 20

20 40 60 80 Hertz OLTF dB Open Loop TF with and without Peak Filter 10

1

10

2

10

3

  • 250
  • 200
  • 150
  • 100

Hertz Degrees

Figure-5 TrueTrack-APMRC-2000

Openloop Transfer Function with a Filter

slide-11
SLIDE 11

Multiple Harmonics

slide-12
SLIDE 12

delay delay B C

  • F
  • E

+ + p(n) R(n) Y(n) R(n-1) A R(n-2)

Track Following Controller Peak Filter #1 VCM VCM current current Notch Filter VCM Driver Seek Controller Gray Burst Decoder Peak Filter #2

VCM

Position Position (Track/Pes) (Track/Pes) Peak Filter #3

Figure-7 TrueTrack-APMRC-2000

Cascade Realization of Multiple Filters

Bias +AC Current

slide-13
SLIDE 13

delay delay B C

  • F
  • E

+ + p(n) R(n) Y(n) R(n-1) A R(n-2)

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Time (sec)

50 100 150 200 250 300

PES (bit)

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Time (sec)

50 100 150 200 250 300

PES (bit)

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Time (sec)

(20,000) (15,000) (10,000) (5,000) 5,000

Filter State

Filter State PES with Peak Filter ON with Optimum Initial Condition PES with no Peak Filter Self-Vibration/Thermal Disk-Shift

Figure-8 TrueTrack-APMRC-2000

Effect of Cascade Implementation

slide-14
SLIDE 14

Track Following Controller Notch Filter Seek Controller Position Position (Track/Pes) (Track/Pes)

Peak Filter #1 Peak Filter #2 Peak Filter #3

+

Bias Free Form

Figure-9

delay delay (B-E)/(A-1) (C-F)/(A-1)

  • F
  • E

+ + p(n) M(n) M(n-1) M(n-2) V(n) A-1 p(n) V(n)

TrueTrack-APMRC-2000

Parallel Realization

slide-15
SLIDE 15

Cross Vibration Example

slide-16
SLIDE 16

+

Bay # B For Cross Vibration For Self Vibration Drive #A 75 Hz Bay # A Drive #B 90 Hz Filter # A Filter # B

dB Frequency dB Frequency

75 Hz 90 Hz

Track Following Controller

Cross Vibration

Figure-10 TrueTrack-APMRC-2000

An Experiment in Spindle Vibration

slide-17
SLIDE 17
  • 10

10 20 30 40 50 60 Time (ms)

  • 40
  • 20

20 40 PES (bit)

PES with filters

  • 10

10 20 30 40 50 60 Time (ms)

  • 10
  • 5

5 10 Filter State (bit)

Self-Vibration Filter#A

  • 10

10 20 30 40 50 60 Time (ms)

  • 10
  • 5

5 10 Filter State (bit)

Cross-Vibration Filter#B

Learning Phase (b) (c) (d)

  • 10

10 20 30 40 50 60 Time (ms)

  • 40
  • 20

20 40 PES (bit)

PES Without Filters

(a) Inactive Inactive

dB Frequency

90 Hz

dB Frequency

75 Hz

Figure-11 TrueTrack-APMRC-2000

Parallel Implementation

slide-18
SLIDE 18

Autonomous State Propagation

slide-19
SLIDE 19
  • 10

10 20 30 40 50 60 Time (ms)

  • 40
  • 20

20 40 PES (bit)

PES Without Filters

(a)

delay delay (B-E) (C-F)

  • F
  • E

+ + PES(n) M(n) M(n-1) M(n-2) + V(n) (A-1)

Track-Follow Controller Track-Follow Controller Switch-B Switch-A

Null-PES

  • 10

10 20 30 40 50 60 Time (ms)

  • 40
  • 20

20 40 PES (bit)

PES with Autonomous Filters

  • 10

10 20 30 40 50 60 Time (ms)

  • 10
  • 5

5 10 Filter State (bit)

Self-Vibration Filter

  • 10

10 20 30 40 50 60 Time (ms)

  • 10
  • 5

5 10 Filter State (bit)

Cross-Vibration Filter

(b) (c) (d)

Autonomous Autonomous

Figure-12 TrueTrack-APMRC-2000

Autonomous Filter State Propagation

slide-20
SLIDE 20
  • 60

60 120 180 servo sector Filter State 3rd 2nd 1st

  • 128
  • 64

64 128 PES (bit) PES

Track Following Seek Track Following

  • 60

60 120 180 servo sector Filter State 3rd 2nd 1st

  • 128
  • 64

64 128 PES (bit) PES

Track Following Seek Track Following (Learning Phase) Track Following

Figure-13

Algorithm-1 Algorithm-2

TrueTrack-APMRC-2000

Effect of Higher Harmonic Filters

slide-21
SLIDE 21

5 10 15 20 25 30 Disk Shift (peak-to-peak) [um] 0.0 1.0 2.0 3.0 4.0 average 1 track seek time for write [msec]

Algorithm-1 Algorithm-2 (Autonomous Mode)

Figure-14 TrueTrack-APMRC-2000

Effect on Single Track Seek

slide-22
SLIDE 22

5 10 15 20 25 30 Disk Shift (peak-to-peak) [um] 100% 150% 200% 250% Format Unit Time Ratio

4um 4um 28um 28um

Performance degradation = 15%

Algorithm-1 Algorithm-2 (Autonomous Mode)

Figure-15 TrueTrack-APMRC-2000

Effective Time to Format a Drive

slide-23
SLIDE 23

1.0" Microdrive TrueTrack

Servo Algorithm

3.5" Deskstar & Ultrastar 2.5" Travelstar HDC-Based Servo Architecture Custom LSI Allows DSP-Free Implementation => Low-Cost Drives with High Performance Specification

Figure-17 TrueTrack-APMRC-2000

TrueTrack

TM Algorithm Embedded in an LSI Module

slide-24
SLIDE 24

TrueTrack-APMRC-2000

Summary Presented an Algorithmic Solution to a Harmonic Error Source. Continuation of Filter State Following a Seek is the Key. Discussed Parallel vs. Cascade Implementation. Problem of PES with Multiple Harmonics can be Resolved. A Silicon Implementation of the TrueTrack Servo has been Realized. Acknowledgment

  • Y. Nakagawa, N. Kagami, T. Ueda, A. Tokizono, T. Sakai, M. Kisaka, and Y. Ozawa

IBM, Fujisawa HDD Development, Japan