Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the record
Reexamination Certificate
2000-01-28
2003-07-01
Holder, Regina N. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the record
C360S075000, C318S254100
Reexamination Certificate
active
06587299
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magnetic storage devices and, more particularly, to a method for overcoming a stiction condition in a disk drive.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates a perspective view of a conventional disk drive
10
. The disk drive
10
includes at least one disk
12
that is rotated by a spin motor
14
. The spin motor
14
is mounted to a base plate
16
. An actuator arm assembly
18
is also mounted to a base plate
16
.
The actuator arm assembly
18
includes a head
20
mounted to a flexure arm
22
which is attached to an actuator arm
24
that can rotate about a bearing assembly
26
. The actuator arm assembly
18
also contains a voice coil motor
28
which moves the head
20
relative to the disk
12
. The spin motor
14
, voice coil motor
28
and head
20
are coupled to a number of electronic circuits
30
mounted to a printed circuit board
32
. The electronic circuits
30
typically include a read channel chip, a microprocessor-based controller and a memory device (e.g., a random access memory (RAM) device and a read only memory (ROM) device). It should be understood that typical disk drives (like disk drive
10
) normally include a plurality of disks
12
and, therefore, a plurality of corresponding actuator arm assemblies
18
.
FIG. 2
is a simplified diagrammatic representation of perspective view of a head
20
showing its air-bearing surface, wherein the air-bearing surface is comprised of three pads
21
a
,
21
b
and
21
c
. As shown in
FIG. 2
, the head
20
includes an air-bearing slider
34
and a transducer
36
.
When the spin motor
14
rotates the disk
12
, the head
20
floats above (or below) the disk
12
on a small cushion of air due to the aerodynamic characteristics of the air-bearing slider
34
. When the disk
12
is brought to a stopped condition, there is no aerodynamic cushion available to float the head
20
above the disk
12
and, therefore, the head
20
lands on the disk
12
. Consequently, to prevent damage to disk
12
, each disk surface
38
(see
FIG. 3
) includes a landing zone
40
onto which the head
20
is usually parked. The landing zone
40
is usually a textured area of the disk surface
38
where data is not normally stored. In contrast, the disk surface
38
also includes a data zone
42
, which is designed to be extremely smooth for a number of reasons which are not of particular significance for this application. Once the head
20
has been parked in landing zone
40
, a latch (not shown) is used to lock the head
20
over the landing zone
40
to prevent undesired movement of the head
20
from the landing zone
40
onto the data zone
42
due to shocks to the drive (e.g., dropping or bumping the drive). In some instances, shocks experienced by the disk drive
10
are such that the latch fails. In these instances, the head
20
may still be in the landing zone
40
without the latch in place or the head
20
may be displaced into the data zone
42
.
Typically, once a head
20
has been parked in the landing zone
40
, the spin motor
14
is activated which has a torque which is generally sufficient to lift the head
20
into a flying condition over the disk surface
38
. In certain instances, however, the head
20
adheres to the disk surface
38
in such a manner that the torque of the spin motor
14
is insufficient to lift the head
20
into a flying condition. This phenomenon is known as stiction.
Stiction may occur when the head
20
is either at rest in the landing zone
40
(whether latched or unlatched) or when the head
20
is at rest in the data zone
42
. Generally, stiction is a greater problem when the head
20
is at rest in the data zone
42
since the data zone
42
is smooth and, therefore, the contact area between the head
20
and the data zone
42
is large (as compared to the textured landing zone
40
). It must be noted, however, that stiction may also occur in the landing zone
40
, for example, when lubricants normally found on the disk surface
38
have migrated to the interface between the head
20
and the disk surface
38
causing a meniscus effect. Other reasons for stiction are well-known in the art.
Because stiction is a significant problem and may render a disk drive inoperable, a number of techniques have been devised in an attempt to overcome stiction conditions. For example, U.S. Pat. No. 4,530,021 entitled “Micromotion Release of Heads from Lubricated Magnetic Disks” discloses a generally triangular waveform of relatively short duration that is supplied to the coils of the voice-coil motor prior to supplying power to rotate the disks. According to FIG. 1 of U.S. Pat. No. 4,530,021, the generally triangular waveform may also be applied while power is supplied to rotate the disks.
Another example is found in U.S. Pat. No. 5,397,971 entitled “Bi-Polar Disk Torquing System for a Disk Drive to Free Stuck Transducers.” U.S. Pat. No. 5,397,971 discloses a method of exciting the spin motor with bi-polar pulses of direct current at substantially the resonant frequency of the rotating assembly to free stuck transducers. The back EMF is sensed from the spin motor to detect rotation.
Another example is found in U.S. Pat. No. 5,384,675 entitled “Disk Drive With Controlled Actuator Oscillation for Release of Head Carriers.” U.S. Pat. No. 5,384,675 discloses applying a series of alternating current pulses to an actuator to dither head carriers at an initial frequency that is generally equal to or above the resonant frequency of the actuator systems with stuck carriers. The frequency and amplitude of the pulses are swept downward from the initial frequency and amplitude, and is repeated until the drive motor rotates at its operating speed.
Yet another example is found in U.S. Pat. No. 5,530,602 entitled “Disk Drive Micromotion Starting Apparatus and Method.” U.S. Pat. No. 5,530,602 discloses a method of applying a series of alternating current bursts to the voice coil motor, beginning with a lowest amplitude burst. Each succeeding current burst is of increased amplitude. During each burst, the pulse frequency is varied progressively through a range of values, wherein the range of selected frequencies are selected to enable the frequency of some of the burst pulses to approach the resonant frequency of one or more modes of disk vibration. A sensor connected to the spindle motor coils responds to the presence of a back EMF, indicating that the heads are no longer adhered to the disk surfaces and that rotation has begun.
Yet a further example is found in U.S. Pat. No. 5,801,505 entitled “Disk Drive Stiction Release System.” U.S. Pat. No. 5,801,505 discloses a method of pulsing the spindle motor and/or the actuator motor if stiction occurs during start-up. Because the resonant frequency of the spindle motor varies depending upon the number of heads that are stuck, pulses are applied over a varying range of frequencies, including the various resonant frequencies of the spindle motor corresponding to various numbers of heads stuck.
It should be understood that the above discussion of the aforementioned patents is only intended to be a brief discussion of each of the patents. To obtain a full understanding of the entire disclosure of such patents and the information contained therein, reference should be made to the patents themselves.
While the above patents provide a number of different alternatives for overcoming stiction conditions, it would be beneficial to provide a relatively simple yet effective technique for overcoming stiction conditions. In addition, it would be beneficial to provide a technique which reduces occurrences of re-stiction.
SUMMARY OF THE INVENTION
The present invention is designed to overcome the aforementioned problems and meet the aforementioned, and other, needs.
A method for overcoming a stiction condition in a disk drive is disclosed. In one embodiment, once a stiction condition is sensed due to non-movement of the spin motor, a microprocessor controls the application of a first oscillation current to a voice coil moto
Albert Glenn
Chen Dennis
Hiller Bernhard
Hansra Tejpal S.
Maxtor Corporation
LandOfFree
Method for overcoming a stiction condition in disk drive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for overcoming a stiction condition in disk drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for overcoming a stiction condition in disk drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3082997