Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-03-06
2001-07-03
Nguyen, Hoa T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078040, C360S078060
Reexamination Certificate
active
06256163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to methods and apparatus for use in disk drives for computer systems. More particularly, the present invention relates to methods and apparatus for reducing the vibration of high frequency resonance modes associated with seeking acoustics in disk drives for computer systems.
2. Description of the Relevant Art
The reduction of noise, or vibrations, in disk drives is crucial to ensure that performance issues associated with a disk drive may be minimized. When the performance of a disk drive is not at an acceptable level, customer dissatisfaction regarding the disk drive may be significant, and the integrity of data stored on the disk drive may be compromised. By way of example, when a disk drive experiences excessive vibration, a customer may perceive the disk drive to be operating in a faulty manner. Therefore, the magnitude of the vibrations experienced on a disk drive must generally be reduced to acceptable levels.
FIG. 1
is a diagrammatic representation of a disk drive assembly suitable for use in a computer system. A disk drive assembly
102
, which may also be known as a head-disk assembly (HDA), includes a platter assembly
104
that is situated on a base plate
103
. Platter assembly, as shown, includes a platter
105
and a spindle mechanism
106
. Spindle mechanism
106
typically includes a spindle bearing
107
which is coupled to platter
105
, or a disk. Data is stored, or otherwise encoded, on platter
104
. Platter
104
may contain multiple spokes
108
, each of which includes encoded position information. That is, each spoke
108
contains track numbers and patterns to determine fractional positions which relate to the location of a disk drive, or read/write, head
120
with respect to platter
104
.
Disk drive assembly
102
also includes an actuator assembly
114
. Actuator assembly
114
includes an actuator
118
which supports disk drive head
120
. Actuator assembly
114
is arranged to move disk drive head
120
to different positions over platter
105
such that data may be retrieved from or stored to different data-carrying sectors of platter
105
. In general, when disk drive head
120
is to be moved, torque is generated to pivot or otherwise move actuator assembly
114
by a motor assembly
122
. Motor assembly
122
is generally mechanically coupled to actuator assembly
114
through an actuator bearing
124
.
Actuator motor assembly
122
often includes a coil structure and a magnetic field which surrounds the coil structure, as will be appreciated by those skilled in the art. In other words, actuator motor assembly
122
typically includes a voice coil motor (VCM). By passing current through the coil structure in a particular direction and for a specified length of time, actuator assembly
114
may be moved, e.g., pivoted, such that disk drive head
120
is positioned over a specific portion of the platter
105
. The pivoting of actuator assembly
114
to position disk drive head
120
in a desired position is generally known as a “seek.”
A spindle bearing
107
, which is coupled to a spindle motor (not shown), allows platter
105
to spin with respect to base plate
103
. Typically, noise is associated with the rotation of platter
105
. Specifically, motor noise associated with a spindle motor, i.e., “spindle noise,” contributes to idle acoustics, or acoustics which are present while platter
105
is spinning. The amount of idle acoustics increases as the spinning speed of platter
105
increases. Further, if spindle bearing
107
is not perfectly circular, spindle bearing
107
may further contribute to idle acoustics.
Although the level of idle acoustics in a disk drive assembly may vary, e.g., the level of idle acoustics may depend upon the mechanical design of the disk drive assembly, idle acoustics are typically in the range of approximately 35 decibels (dB) to approximately 40 decibels when the platter spinning speed is approximately 4000 revolutions per minute (RPM). By way of example, idle acoustics in the range of approximately 37 dB to approximately 38 dB are typically the market requirement for 5.25 inch disk drives which have a spindle speed of approximately 4000 RPM.
Acoustics associated with seeking processes, referred to herein as “additional seeking acoustics,” are additive with respect to idle acoustics. In other words, acoustics are affected by both idle acoustics and additional seeking acoustics. Generally, the “sum” of idle acoustics, which are caused by the spinning of platter
105
, and additional seeking acoustics, which result from the performance of a seek, is considered to be the overall seeking acoustics.
Additional seeking acoustics are typically the result of disk drive structural vibration induced by the seek current. Current is sent through the VCM, i.e., the VCM that is a part of motor assembly
122
, to create a torque which is applied to actuator assembly
114
in order to move actuator assembly
114
.
FIG. 2
a
is a block diagram which illustrates a conventional system used to generate a torque starting with a current command that is provided by a seek program. A current command
204
is sent to a digital-to-analog (D/A) converter
206
, or a pulse width modulator (PWM) to produce a control voltage
207
which is proportional to current command
204
, numerically. Current command
204
is sent to D/A converter
206
which, in turn, feeds control voltage
207
into a power amplifier
208
, in response to a seek command, or a request to move an actuator assembly in order to position a disk drive head. Power amplifier
208
processes, e.g., amplifies, current command
204
to generate a motor input current
212
, or a seek current.
Motor input current
212
is effectively arranged to produce a torque
220
that causes an actuator to move. Specifically, motor input current
212
causes an actuator motor
216
to create torque
220
that moves an actuator to a desired location. Torque
220
may cause the actuator to accelerate, decelerate, or move at a constant velocity. In other words, motor input current
212
is arranged to generate torque
220
that causes an actuator to rotate to a desired position for the actuator as required by a seek command. The profile of motor input current
212
is dependent upon the profile of current command
204
.
In order to move an actuator, e.g., actuator assembly
118
of
FIG. 1
, efficiently to a desired position, the amount of current sent to the VCM is often adjusted substantially instantaneously, as will be described in more detail below with respect to
FIGS. 2
b
and
2
c.
While the level of noise associated with the VCM during a seek may be widely varied, the level of noise, i.e., the additional seeking acoustic, is typically in the range of approximately 5 dB to approximately 10 dB in sound power, as for example approximately 7 dB.
In general, acceptable levels of overall seeking acoustics in disk drive assemblies are determined based upon what is considered to be tolerable by customers who use the disk drive assemblies. For 5.25 inch disk drives, an overall seeking acoustic which is no more than approximately 45 dB is generally considered to be acceptable, although an overall seeking acoustic which is less than approximately 40 dB is preferred. However, as overall seeking acoustics are often in the range of approximately 45 dB to approximately 50 dB, many disk drives fail to meet acceptable levels of noise during seek operations. Failure to meet acceptable levels for overall seeking acoustics may lead to disqualification of disk drives by customers, as well as performance issues related to the disk drives.
Additional seeking acoustics result from large changes of amplitude in a motor input current which is used to create a torque on an actuator motor. As will be appreciated by those skilled in the art, changes in seek current are correlated to the amount of noise associated with a seek command. Specifically, a higher level of noise is generally attributed to a more rapid change
Schmidt Thorsten
Wang Jwo-Min
Davidson Dan I.
Nguyen Hoa T.
Quantum Corporation
LandOfFree
Method and apparatus for performing current shaping for... 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 and apparatus for performing current shaping for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for performing current shaping for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2481342