This paper applies the half-power method to identify damping of a gyroscopic system. At first, the underlying principle of the half-power method for damped, gyroscopic systems is explained. Then the method is demonstrated on a rotating disk/spindle system often used in computer hard disk drives. The disk/spindle system consists of multiple elastic disks mounted on a rigid spindle supported by ball bearings. The flexibility of the bearings allows the spindle to undergo rigid-body translation and rocking. Calibrated experiments were conducted in vacuum to obtain frequency response functions at different rotational speed. Application of the half-power method shows that the disk and bearing dampings are independent of rotational speed and can be modeled adequately as viscous damping. Moreover, the damping of the ball bearings is two orders of magnitude smaller than that of a fluid-film bearing of similar size.

1.
Bittner, H., 1998, “The Effects of Air on Disk/Spindle Dynamics and the Taming of Disk Drive Vibration,” Master Thesis, University of Washington.
2.
Burrows
C. R.
, and
Sahinkaya
M. N.
,
1982
, “
Frequency-Domain Estimation of Linearized Oil-Film Coefficients
,”
ASME Journal of Lubrication Technology
, Vol.
104
, pp.
210
215
.
3.
Childs, D., 1993, Turbomachinery Rotordynamics: Phenomena, Modeling, and Analysis, pp. 23–35, John Wiley & Sons, Inc., New York.
4.
Jei
Yang-Gyu
, and
Kim
Young-Ju
,
1993
, “
Modal Testing Theory of Rotor-Bearing Systems
,”
ASME JOURNAL OF VIBRATION AND ACOUSTICS
, Vol.
115
, pp.
165
176
.
5.
Joh
Y.-D.
, and
Lee
C.-W.
,
1993
, “
Excitation Methods and Modal Parameter Identification in Complex Modal Testing of Rotating Machinery
,”
The International Journal of Analytical and Experimental Modal Analysis
, Vol.
8
, No.
3
, pp.
179
203
.
6.
Kraus
J.
,
Blech
J. J.
, and
Braun
S. G.
,
1987
, “
In Situ Determination of Rolling Bearing Stiffness and Damping by Modal Analysis
,”
ASME JOURNAL OF VIBRATION, ACOUSTICS, STRESS, AND RELIABILITY IN DESIGN
, Vol.
109
, pp.
235
240
.
7.
Lee
C. W.
,
1991
, “
A Complex Modal Testing Theory for Rotating Machinery
,”
Journal of Mechanical Systems and Signal Processing
, Vol.
5
, pp.
119
137
.
8.
Nordmann
R.
,
1984
, “
Identification of Modal Parameters of an Elastic Rotor with Oil Film Bearings
,”
ASME JOURNAL OF VIBRATION, ACOUSTICS, STRESS, AND RELIABILITY IN DESIGN
, Vol.
106
, pp.
107
112
.
9.
Sahinkaya
M. N.
,
Turkay
O. S.
, and
Burrows
C. R.
,
1984
, “
Minimization of the Variance in Oil-Film Damping Coefficient Estimates
,”
ASME Journal of Dynamic Systems, Measurement, and Control
, Vol.
106
, pp.
342
349
.
10.
Shen
I. Y.
,
1997
, “
Closed-Form Forced Response of a Damped, Rotating, Multiple Disk/Spindle System
,”
ASME Journal of Applied Mechanics
, Vol.
64
, pp.
343
352
.
11.
Shen
I. Y.
, and
Ku
C.-P
,
Roger
,
1997
, “
A Non-Classical Vibration Analysis of Multiple Rotating Disk/Spindle Assembly
,”
ASME Journal of Applied Mechanics
, Vol.
64
, pp.
165
174
.
12.
Shumway, M. L., 1997, “An Experimental Study of Damping in a Rotating Disk and Spindle System,” Master Thesis, University of Washington.
13.
Stanway
R.
,
1984
, “
Journal Bearing Identification Under Operating Conditions
,”
ASME Journal of Dynamic Systems, Measurement, and Control
, Vol.
106
, pp.
178
182
.
14.
Zang, Y., and Hatch, M. R., 1996, “On the Whirl Dynamics of Hydrodynamic Bearing Spindle in Information Storage Systems,” Proceedings of the 7th Annual Information Storage and Processing Systems Symposium, ASME ISPS-Vol. 2, pp. 73–84.
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