Mechanical & Aerospace Engineering_33

171 Pages·2006·4.91 MB·English

DISK DRIVE ACTUATOR DESIGN AND CONTROL FOR
ROBUST NON-OPERATIONAL SHOCK PERFORMANCE
By
RYAN TODD RATLIFF
Bachelor of Science
University of Oklahoma
Norman, Oklahoma, USA
1992
Master of Science
University of Oklahoma
Norman, Oklahoma, USA
1997
Submitted to the Faculty of the
Graduate College of
Oklahoma State University
in partial fulfillment of
the requirements for
the Degree of
DOCTOR OF PHILOSOPHY
December, 2005
COPYRIGHT c
(cid:13)
By
RYAN TODD RATLIFF
December, 2005
DISK DRIVE ACTUATOR DESIGN AND CONTROL FOR
ROBUST NON-OPERATIONAL SHOCK PERFORMANCE
Dissertation Approved:
Prabhakar R. Pagilla
Dissertation Advisor
Rafael Fierro
Eduardo A. Misawa
Gary E. Young
Dean of the Graduate College
iii
TABLE OF CONTENTS
Chapter Page
1 INTRODUCTION 1
2 ACTUATOR DESIGN WITH NONLINEAR MAGNETIC BIAS 18
2.1 Design Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Design Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.1 Lumped Parameter Design . . . . . . . . . . . . . . . . . . . . 20
2.2.2 Distributed Parameter Design . . . . . . . . . . . . . . . . . . 25
2.2.3 Magnetic Bias Design . . . . . . . . . . . . . . . . . . . . . . . 28
2.3 Dynamic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3 SEEK CONTROL WITH NONLINEAR BIAS EFFECTS 34
3.1 Trajectory Generation . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 Linear State-Feedback Control Design . . . . . . . . . . . . . . . . . . 36
3.3 Adaptive Controller Design . . . . . . . . . . . . . . . . . . . . . . . 37
3.3.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 41
3.3.2 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 47
3.4 Modeling Accuracy and Sample Rate Effects . . . . . . . . . . . . . . 53
3.5 Output Feedback Design . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.5.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.5.2 Full State Feedback Controller Design . . . . . . . . . . . . . 58
3.5.3 Observer Design . . . . . . . . . . . . . . . . . . . . . . . . . . 61
iv
3.5.4 Output Feedback . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.5.5 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 63
3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4 THE COMMUTATIONAL RAMP LOAD ACTUATOR 73
4.1 Actuator Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1.1 Design Constraints/Requirements . . . . . . . . . . . . . . . . 74
4.1.2 Voice Coil Motor . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.1.3 Magnetic Bias Design . . . . . . . . . . . . . . . . . . . . . . . 77
4.1.4 Ramp Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.2 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.3 Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.3.1 Non-operational Shock Performance . . . . . . . . . . . . . . . 83
4.3.2 Move-time Performance . . . . . . . . . . . . . . . . . . . . . 84
4.4 Experimental Validation . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.4.1 Actuator Physical Parameters . . . . . . . . . . . . . . . . . . 87
4.4.2 Rotational Shock Performance . . . . . . . . . . . . . . . . . . 91
4.4.3 Open-Loop Analysis . . . . . . . . . . . . . . . . . . . . . . . 92
4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5 DYNAMIC ANALYSIS OF THE COMMUTATIONAL
RAMP LOAD ACTUATOR 95
5.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.2 Approximate Input/Output Linearization of Nonregular Systems . . . 98
5.3 The Ball and Beam System . . . . . . . . . . . . . . . . . . . . . . . 101
5.4 The Disk Drive Commutational L/UL Actuator . . . . . . . . . . . . 105
5.5 Commutational Ramp Load Actuator Dynamic Analysis . . . . . . . 111
5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
v
6 DISK DRIVE COMMUTATIONAL RAMP LOAD CONTROL 119
6.1 Performance Requirements . . . . . . . . . . . . . . . . . . . . . . . . 119
6.2 Trajectory Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
6.3 Robust State-Feedback Control . . . . . . . . . . . . . . . . . . . . . 124
6.3.1 Controller Design . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.3.2 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 129
6.4 Output Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . 131
6.4.1 Controller Design . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.4.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 136
6.4.3 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 142
6.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
7 SUMMARY AND FUTURE WORK 148
BIBLIOGRAPHY 153
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LIST OF TABLES
Table Page
2.1 Actuator performance requirements . . . . . . . . . . . . . . . . . . . 19
2.2 Coil design parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.3 Lumped parameter magnetic circuit design . . . . . . . . . . . . . . . 24
2.4 Dynamic model parameter comparison . . . . . . . . . . . . . . . . . 27
3.1 Simulated controller performance summary . . . . . . . . . . . . . . . 47
3.2 Controller experimental performance summary . . . . . . . . . . . . . 52
3.3 Magnetic bias polynomial coefficients . . . . . . . . . . . . . . . . . . 53
3.4 Magnetic bias controller adaptation gains . . . . . . . . . . . . . . . . 54
3.5 Bias modeling accuracy-sample rate study (L norm) . . . . . . . . . 54
2
3.6 Error norms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.1 Actuator design constraints . . . . . . . . . . . . . . . . . . . . . . . 74
4.2 Lumped parameter coil design. . . . . . . . . . . . . . . . . . . . . . 76
4.3 Magnetic circuit design comparison . . . . . . . . . . . . . . . . . . . 77
4.4 Ramp design parameters . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.5 System physical parameters for shock robustness . . . . . . . . . . . . 84
4.6 Dynamic model parameter comparison . . . . . . . . . . . . . . . . . 86
4.7 Polynomial coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.1 Performance requirements . . . . . . . . . . . . . . . . . . . . . . . . 120
6.2 State-feedback control gains . . . . . . . . . . . . . . . . . . . . . . . 130
6.3 Controller performance . . . . . . . . . . . . . . . . . . . . . . . . . . 131
vii
6.4 Simulation controller gains . . . . . . . . . . . . . . . . . . . . . . . . 140
6.5 Experimental controller gains . . . . . . . . . . . . . . . . . . . . . . 143
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LIST OF FIGURES
Figure Page
1.1 Inertial latch concept (Courtesy of Fujitsu Corp). . . . . . . . . . . . 2
1.2 Air latch concept (Courtesy of Quantum Corp). . . . . . . . . . . . . 3
1.3 Bi-stable latch concept (Courtesy of Seagate Technology). . . . . . . 4
1.4 Laser zone texture at inner radius . . . . . . . . . . . . . . . . . . . . 8
1.5 Disk damage resulting from linear shock HDI. . . . . . . . . . . . . . 8
1.6 Ramp load concept (Courtesy of Fujitsu Corp) . . . . . . . . . . . . . 9
1.7 Disk damage resulting from ramp loading HDI . . . . . . . . . . . . . 10
1.8 Conventional actuator illustrating uncontrollability. . . . . . . . . . . 11
1.9 Left of the red line depicts additional magnet material required specif-
ically to provide actuation while maneuvering on the ramp. . . . . . . 12
1.10 Actuator after traveling through MT. Current polarity is reversed. . . 14
2.1 Lumped actuator profile showing bottom half with coil . . . . . . . . 20
2.2 Lumped parameter coil profile . . . . . . . . . . . . . . . . . . . . . . 21
2.3 General tandem C-core actuator configuration . . . . . . . . . . . . . 23
2.4 Distributed actuator geometry showing bottom half with coil . . . . . 25
2.5 FEM coil geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.6 Magnetic circuit leakage at PCB (FEM results) . . . . . . . . . . . . 26
2.7 Magnetic circuit air gap flux density (FEM results) . . . . . . . . . . 27
2.8 Torque factor profile . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.9 Bias feature design on actuator arm . . . . . . . . . . . . . . . . . . . 30
2.10 Measured magnetic bias torque . . . . . . . . . . . . . . . . . . . . . 31
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2.11 Experimental drive magnetic bias concept . . . . . . . . . . . . . . . 32
3.1 Bias torque boundary with tolerance variation . . . . . . . . . . . . . 41
3.2 Statefeedback simulated outwardmove performanceoptimized forsat-
uration in S ; actual (solid), reference (dashed). . . . . . . . . . . . . 43
2
3.3 State feedback simulated inward move performance optimized for sat-
uration in S ; actual (solid), reference (dashed). . . . . . . . . . . . . 43
2
3.4 Adaptive control simulated inward move performance in S . Bias coef-
2
ficientsinitially7%lowerthannominal; actual(solid),reference(dashed). 45
3.5 Adaptive control simulated outward move performance in S . Bias
2
coefficients initially 7% lower than nominal; actual (solid), reference
(dashed). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.6 Adaptive control simulated bias coefficient ratio for an inward move
in S . Bias coefficients initially 7% lower than nominal; actual (solid),
2
reference (dashed). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.7 Adaptive control simulated bias coefficient ratio for an outward move
in S . Bias coefficients initially 7% lower than nominal; actual (solid),
2
reference (dashed). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.8 Experimental setup for full state feedback magnetic bias seek control 48
3.9 Experimental disk drive for full state feedback magnetic bias seek control 48
3.10 State feedback performance (10 seek sample) . . . . . . . . . . . . . . 49
3.11 Adaptive controller performance (10 seek sample) . . . . . . . . . . . 50
3.12 Estimated coefficient dynamics . . . . . . . . . . . . . . . . . . . . . 51
3.13 Adaptive controller performance with projection (10 seek sample) . . 51
3.14 Estimated coefficient dynamics with projection . . . . . . . . . . . . . 52
3.15 Bias modeling accuracy-sample rate study (L norm) . . . . . . . . . 55
2
3.16 Simulation error results (0.1745 rad) . . . . . . . . . . . . . . . . . . 65
3.17 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
x