Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-03-31
2002-08-06
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06429997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a disk device, and more particularly, to a disk device for recording and playing data to and from a desired track on a disk.
2. Description of the Related Art
As data capacity has increased in recent years a high-capacity recording medium for providing data has become more desirable. A high-capacity floppy disk, for example, has already been developed as one such high-capacity recording medium. The high-capacity floppy disk can be recorded and played using magnetism alone and can therefore be used together with ordinary floppy disks, making the high-capacity floppy disk a popular choice for a recording medium.
A disk drive used to record and play data to and from these types of high-capacity floppy disks comprises a head carriage for which a mode of seeking a particular track on the disk is controlled in such a way that a graphical depiction of the speed with which the carriage moves when seeking a particular track assumes the shape of a table or plateau. Examples of such a seek mode speed profile, hereinafter referred to as a speed profile, are shown in FIG.
7
and FIG.
8
. The speed profile is generally such that the head carriage accelerates until it attains a maximum speed Vmax, at which point the head carriage thereafter maintains this maximum speed Vmax until decelerating upon approach to the target track.
However, the speed profile of the head carriage differs depending on the distance from a current track, that is, a current address, to a target track, that is, a target address.
Assuming, for the sake of illustration, that a distance from a current track to a target track is a relatively long distance, then the speed profile of the head carriage as it moves from the current track to the target track is such that at a time t
0
to a time t
2
the head carriage accelerates until it attains a maximum speed Vmax, at a time t
2
to t
4
the head carriage moves at this constant maximum speed Vmax and at a time t
4
to t
5
the head carriage decelerates, forming the roughly plateau-like speed profile shown in FIG.
7
and FIG.
8
.
However, if the distance from a current track to a target track is a relatively short distance, then the speed profile of the head carriage as it moves from the current track to the target track is such that at a time t
0
to a time t
1
the head carriage accelerates and from a time t
1
to t
3
the head carriage decelerates, without attaining a maximum speed Vmax. Accordingly, the speed profile resembles a triangle as shown in FIG.
7
.
A description will now be given of a formula for obtaining the speed profile shown in FIG.
7
.
If the target speed during acceleration is Va, the head carriage acceleration time determined from the propulsive force of an actuator that moves the head carriage and the mass of the head carriage is &agr;a and the head carriage movement distance is x, then
Va
={square root over ((2
·&agr;a·x
+L ))} (1)
Additionally, if the target speed during deceleration is Vd, the speed of the head carriage when deceleration commences is Vd
0
, the acceleration at deceleration as determined from the propulsive force of an actuator for moving the head carriage and the mass of the head carriage is &agr;d, the movement distance of the head carriage from the current track to the target track is x and the position at which deceleration commences is xd, then the target speed at deceleration can be determined by
Vd=Vd
0
−{square root over ({(2
·&agr;d·
+L (
x−xd
+L )})} (2)
A speed profile like that shown in
FIG. 7
is produced from formulas (1) and (2) as described above.
It should be noted that the above-described speed profile can be disrupted, that is, errors in the movement of the head carriage can occur, due to disturbance of the head carriage. As can be appreciated, such movement errors can affect the accuracy with which data is written to and read from a disk.
As methods for correcting movement errors due to disturbance of the head carriage, Japanese Laid-Open Patent Application Nos. 1-220233, 1-296434 and 6-60394 have been proposed.
Japanese Laid-Open Patent Application No. 1-220233 describes a device for recording and playing optical data that detects an inclination angle of the head carriage by an inclination angle detector and applies an offset electric current to a voice coil of a voice coil-type linear motor according to the results of that detection.
Further, Japanese Laid-Open Patent Application No. 1-296434 describes a device for recording and playing optical data by determining an acceleration caused by the inclination of the head and adding an offset current that imparts a propulsive force in a direction that negates that acceleration to a drive current of a voice coil.
Japanese Laid-Open Patent Application No. 6-60394 describes an optical disk drive device that provides means for detecting an angle of inclination in a direction of movement of a carriage and switches a carriage control system gain according to an angle of inclination shown by an output signal from the inclination angle detection means.
However, with the conventional disk device, the disk device is set horizontally and, without taking into account the effects of friction, the acceleration &agr; can be obtained by
&agr;=
F/M
(3)
where F is the propulsive force of the actuator and M is the mass of the head carriage.
However, when the disk device is set at an incline, the force of gravity is dispersed horizontally and affects the movement of the head carriage.
FIG. 9
describes a component of force in the horizontal direction when the disk device is set at an incline. As shown in
FIG. 9
, when the drive unit is inclined in the direction of the seek the effect of gravity is exerted in the seek direction. If gravitational acceleration is g, head carriage mass M, the inclination angle &thgr; and the actuator propulsive force F, then the acceleration &agr;d can be found by
&agr;
d
=(
F−M·g
·sin &thgr;)/
M
(4)
As can be readily appreciated, acceleration &agr;d is smaller than an acceleration &agr; set when creating the target speed profile. As a result, an acceleration at deceleration, that is, a negative acceleration, is inadequate when seeking an appropriate track at a speed profile determined according to formula (2). Thus the actual head carriage speed at deceleration as indicated by the dotted line shown in
FIG. 8
is unable to trace the target speed profile and, as a result, the head carriage arrives at the target track without being able to fully decelerate.
It should be noted that a switch is made from a speed control mode to a position control mode when the head carriage arrives at the target track. If this switch to position control mode is made without the head carriage having fully decelerated, then the initial speed of the head carriage in the position control mode will be high and, as a result, the head carriage will greatly overshoot the target track, leading to poor settling and perhaps causing a seek error.
On the other hand, if the acceleration &agr; is set to a smaller value when creating the target speed profile in consideration of formula (4) in order to prevent the occurrence of the above-described problem, then a gently accelerating and decelerating speed profile will occur even during normal use, when a force is not normally exerted on the head carriage in the seek direction, causing the seek time to increase. Additionally, similar problems occur due to changes caused by the temperature of the reaction force of the flexible substrate that connects the control substrate and the head carriage.
Further, the inventions of Application No. 1-220233, Application No. 1-296434 and Application No. 6-60394 have an inclination detector for detecting an inclination of the head carriage, thus complicating the structure of the disk device. Additionally, a further problem arises in that, depending on the manner in which the inclination detector is mounted
Anderson Kill & Olick P.C.
Hudspeth David
Lieberstein Eugene
TEAC Corporation
Wong K
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