Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
2000-12-28
2003-04-29
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S077040, C360S077080, C360S078140
Reexamination Certificate
active
06556367
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a storage apparatus and a position sensitivity setting method, ensuring constant position sensitivities by adjusting into a predefined level the intersection level of two position signals demodulated from two-phase servo information buried and recorded in a medium, and more particularly to a storage apparatus and a position sensitivity setting method correcting nonlinear position sensitivities possessed by the position signals into linear ones.
BACKGROUND ART
With the recent demands for larger capacities and smaller dimensions of the magnetic disk units, the track density (TPI) becomes even higher, making improvement of the servo signal based position accuracy for realizing this more significant. As opposed to the conventional servo-surface servo needing dedicated servo surface and servo head, a more cost-effective sector servo, so-called data-surface servo ensuring increased recording capacities has been adopted in which servo information is buried in the data surface at its sector leading position. In case of recording two-phase servo information in the servo-surface servo or sector servo, two position signals N and Q having different phases by 90 degrees (½ track pitch) are demodulated from servo signals read from the disk medium, and on the basis of these position signals N and Q the seeking operations by the head coarse control and the positioning operations by the fine control are carried out. The two position signals N and Q demodulated from the two-phase servo information indicate the head position by their respective signal levels, and therefore, irrespective of any variances in the read signals as a result of dispersions of the core width, the two finally demodulated position signals N and Q must always have unvarying amplitudes at the head position at the intersection level where the two coincide with each other. To this end, upon the apparatus setup for example, a position sensitivity adjustment is carried out which includes moving the head at a low speed, detecting and storing an intersection level where the two position signals N and Q coincide with each other, and setting into an AGC amplifier the gain which has the intersection level as a predefined theoretical value, to thereby keep constant the sensitivities of the two position signals N and Q relative to the head position.
FIG. 1
shows a conventional position sensitivity adjustment circuit directed to the servo-surface servo. Referring to
FIG. 1
, upon the position sensitivity adjustment, two position signals N and Q having 90-degrees shifted phases are demodulated from the read signal of the two-phase servo information on the servo surface with the VCM being driven at a low speed, and then amplified by AGC amplifiers
102
and
104
, after which they are converted into absolute position signals |N| and |Q| by absolute value circuits
106
and
108
for the impartment to an intersection level detection circuit
110
.
FIG. 2A
shows the position signals N and Q output from the AGC amplifiers
102
and
104
with the axis of abscissas representative of the actual track position X. The position signals N and Q from the AGC amplifiers
102
and
104
are converted into the absolute position signals |N| and |Q| by the absolute value circuits
106
and
108
. The intersection level detection circuit
110
compares the absolute value signals |N| and |Q| of
FIG. 2B
to detect the signal levels at the intersections
114
,
116
,
118
,
120
, etc., and stores the average value thereof as the intersection value in a storage
112
. The gains of the AGC amplifiers
102
and
104
of
FIG. 1
are adjusted such that the intersection value stored in the storage
112
coincides with a certain value (theoretical value). Such a position sensitivity adjustment is carried out for each head and on a disk medium zone basis, and the position signals N and Q are amplified by the AGC amplifiers
102
and
104
so that the intersection level of the position signals N and Q coincides with the certain value (theoretical value) to acquire constantly unvarying position sensitivities. This is the position sensitivity correction or the head core width correction in the state of the art, which allows adjustment for constantly unvarying position sensitivity and high-precision position detection to be made in spite of the core width dispersions on a head-to-head basis.
By the way, a higher medium track density TPI attendant on the increased capacity and reduced dimensions necessitates more precise position sensitivities. However, the position signals N and Q demodulated from the two-phase servo information shown in
FIG. 2A
are merely ideal signals lacking the consideration for, e.g., the leakage flux to the head cores and are regarded as having a linear characteristic that the position signals N and Q relative to the actual track position X are linear within the range below the intersection level, with the position sensitivities keeping constantly unvarying values. More strictly, however, the position signals are under the influence of the leakage flux so that the positions signals are not precisely linear relative to the actual track position X even in the range below the intersection level, thus presenting the nonlinear position sensitivities. Nevertheless, the position sensitivity is regarded as constant within the range below the intersection level to correct the intersection level to a certain level (theoretical value), i.e., to make one-point correction. This does not mean the adjustment of the nonlinear position sensitivities into constant sensitivities. Thus, there lies an error between the intersection level based one-point linear corrected position sensitivities and the actual nonlinear position sensitivities. This position sensitivity error may impede the acquisition of high-precision signals required for the higher track density TPI.
DISCLOSURE OF THE INVENTION
According to the present invention there are provided a storage apparatus and a position sensitivity setting method therefor, capable of acquiring high-precision position signals by further correcting nonlinear position sensitivities once corrected on the basis of the intersection of two position signals demodulated from two-phase servo information, into linear ones.
The storage apparatus of the present invention comprises a position sensitivity adjusting unit and a sensitivity correcting unit. The position sensitivity adjusting unit detects the signal level at the intersection of position signals N and Q having different phases Ø by a predetermined track pitch (TP
), e.g., TP/2 which are demodulated from read signals of two-phase servo information buried and recorded in a disk medium, the position sensitivity adjusting unit making an adjustment of the gain of an AGC amplifier so that the intersection signal level coincides with a predetermined level. Herein, n represents any arbitrary integers including 1, 2, 3, 4, etc. The sensitivity correcting unit corrects nonlinear position sensitivities relative to the actual track position X of two position signals N and Q output from the AGC amplifier, into linear position sensitivities. In this manner, the present invention feeds by no means the position signals N and Q having nonlinear position sensitivities intactly to the control circuit, but instead creates position signals Na and Qa whose nonlinear position sensitivities have been corrected into linear position sensitivities by the correction circuit, previous to the feed to the control circuit, thereby making it possible to provide a precise head position control irrespective of the nonlinear head detection characteristics whereby a high-precision head position control can be provided especially in the event of the increased track densities of the disk medium.
Herein, the sensitivity correcting unit corrects nonlinear position sensitivities of the position signals N and Q, into linear position sensitivities having certai
Davidson Dan I.
Fujitsu Limited
Greer Burns & Crain Ltd.
Hudspeth David
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