The feasibility of a ramp load controller using a conventional disk drive actuator is investigated. The controller eliminates the necessity of increased material requirements common in ramp load disk drives. Therefore, disk drives with lower cost, higher performance actuators can realize the linear shock protection benefits of ramp loading. A disk drive designed with a conventional actuator is outfitted with a ramp and optimized for ramp load operation. While on the ramp, there exists a set in the state space where the actuator dynamics are uncontrollable. An input commutation is required within the uncontrollable region to sustain the direction of actuator motion. Additionally, the motor torque factor, magnetic restoration bias, and friction torque are nonlinear and can be represented by functions that are Lipschitz within the actuator ramp angle. A state trajectory is generated that, when tracked, moves the actuator through the uncontrollable set for a successful load onto the disk at the desired load velocity. Because position and velocity information are not available during a load maneuver, an output feedback controller is necessary. A stable, output feedback tracking controller is designed to track the trajectory and handle the nonlinear effects. A unique disk drive is manufactured and experiments are performed to verify the complete ramp loading design strategy.

1.
Jeong
,
T. G.
, and
Bogy
,
D. B.
, 1992, “
An Experimental Study of the Parameters that Determine Slider-Disk Contacts During Dynamic Load-Unload
,”
ASME J. Tribol.
0742-4787,
114
, pp.
507
514
.
2.
Zeng
,
Q. H.
, and
Bogy
,
D. B.
, 2000, “
Effects of Certain Design Parameters on Load/Unload Performance
,”
IEEE Trans. Magn.
0018-9464,
36
, pp.
140
147
.
3.
Levi
,
P. G.
, and
Talke
,
F. E.
, 1992, “
Load/Unload Investigations on a Rotary Actuator Disk Drive
,”
IEEE Trans. Magn.
0018-9464,
28
(
5
), pp.
2877
2879
.
4.
Ratliff
,
R. T.
, 2000, “
Extending Actuator Range Through Magnetic Flux Reversal Detection
,” U.S. Patent No. 6,157,509.
5.
Ratliff
,
R. T.
, and
Trammell
,
C. A.
, 2003, “
Passive Actuator for Assisting Commutational Ramp Loading
,” U.S. Patent No. 6,621,651 B1.
6.
Tomlin
,
C. J.
, and
Sastry
,
S. S.
, 1998, “
Switching Through Singularities
,”
Syst. Control Lett.
0167-6911,
35
, pp.
145
154
.
7.
Chen
,
W. H.
, and
Ballance
,
D. J.
, 2002, “
On a Switching Control Scheme for Nonlinear Systems With Ill-Defined Relative Degree
,”
Syst. Control Lett.
0167-6911,
47
, pp.
159
166
.
8.
Aboky
,
C.
,
Sallet
,
G.
, and
Vivalda
,
J.
, 2002, “
Observers for Lipschitz Non-Linear Systems
,”
Int. J. Control
0020-7179,
75
(
3
), pp.
204
212
.
9.
Arcak
,
M.
, and
Kokotovic
,
P.
, 2002, “
Observer-Based Control of Systems With Slope-Restricted Nonlinearities
,”
IEEE Trans. Autom. Control
0018-9286,
46
(
7
), pp.
1146
1150
.
10.
Pagilla
,
P. R.
, and
Zhu
,
Y.
, 2004, “
Controller and Observer Design for Lipschitz Nonlinear Systems
,”
Proceedings of the IEEE American Control Conference
.
11.
Ratliff
,
R. T.
, and
Pagilla
,
P. R.
, 2006, “
Commutational Ramp Load Control for Disc Drive Actuators
,”
IEEE Trans. Control Syst. Technol.
1063-6536,
14
(
3
), pp.
436
442
.
12.
Byers
,
R.
, 1988, “
A Bisection Method for Measuring the Distance of a Stable Matrix to the Unstable Matrices
,”
SIAM (Soc. Ind. Appl. Math.) J. Sci. Stat. Comput.
0196-5204,
9
, pp.
875
881
.
You do not currently have access to this content.