Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
1999-09-03
2001-09-25
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
C360S077030, C360S077040, C360S078090, C360S078130
Reexamination Certificate
active
06295507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a calibration method for an acceleration sensor in a storage device and a storage device, for correcting a position of an actuator by detecting an acceleration of an enclosure in the storage device for reading or reading/writing data by a head from and to a storage medium.
2. Description of the Related Art
A storage disk device such as a magnetic disk device etc is widely utilized as a storage device for a computer etc. a high density record and a speed-up are requested of this type of storage disk device.
FIG. 10
is a diagram showing a construction of a magnetic disk device in the prior art.
FIG. 11
is an explanatory diagram showing residual vibrations of an enclosure.
As shown in
FIG. 10
, the magnetic disk device includes a magnetic disk
91
and a magnetic head
92
. The magnetic head
92
reads and writes data from and to the magnetic disk
91
. An actuator
93
supports the magnetic head
92
. A VCM (voice coil motor)
94
drives the actuator
93
. An enclosure
90
holds those components inside.
In the thus constructed magnetic disk device, the actuator
93
mounted with the magnetic head
92
seeks the head
92
from a certain track to another target track. This is called a seek operation. A high-speed respondency is obtained reducing this seek time.
The acceleration and deceleration of the actuator
93
are intensified for reduce the seek time. At this time, a force acts upon the whole enclosure
90
of the disk device due to reaction of the actuator
93
. The enclosure
90
is normally fixed, and therefore it does not mean that the enclosure
90
is vibrated by the reaction as it is. A mechanical transfer function thereof, however, has a point of resonance at a given frequency. Therefore, as shown in
FIG. 11
, when the enclosure
90
is excited by the seek reaction, a vibration of the enclosure
90
remains after the seek operation.
This vibration is applied to a head position signal as a relative deviation between the head
92
and the disk medium
91
, and hence appears as a residual vibration in the position signal after the seek. Consequently, the seek time elongates. One of the basic countermeasures is to enhance a capability of restraining an error signal by improving a servo control characteristic. When a track pitch on the disk is narrowed, however, it can not cope with this simply by a servo gain enhancement. Further, the vibration of the enclosure is on the order of several hundreds Hz which can not be essentially compressed by a normal servo system of the magnetic disk.
In a prior system, as shown in
FIG. 10
, acceleration sensors
95
,
96
for detecting an acceleration of the enclosure
90
are provided for directly measuring the acceleration of the enclosure
90
. Then, there is proposed a feed forward system for correcting the servo control signal by the measured signal. This type of system is disclosed in, e.g., Japanese Patent Application Laid-Open Publication No.9-45024, U.S. Pat. No. 5,299,075, U.S. Pat. No. 5,426,545 and U.S. Pat. No. 5,663,847.
There arise, however, the following problems inherent in the prior art.
(1) It is required that a sensitivity of the acceleration sensor be obtained in order to use the acceleration sensor and utilize this sensor for the position control. There is, however, the sensitivity of the acceleration sensor is different in each sensor. For example, in piezoelectric sensors, there is ±20% difference in the sensitivity. Accordingly, a problem is that a preferable output can not be obtained even by setting a fixed sensitivity.
(2) There is a method of selecting parts which have been calibrated beforehand. However, a problem is that the cost increases. Further, the sensitivity on a state of being loaded into the device might differ from the detected sensitivity on a state of the parts. Therefore, there arises such a problem that a calibrated value on the state of the parts can not be used as it is.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a calibration method for an acceleration sensor in a storage device and a storage device, which is capable of calibrating the acceleration sensor in a state of being loaded into a device.
It is another object of the present invention to provide a calibration method for an acceleration sensor in a storage disk device and a storage device, which is capable of precisely calibrating the acceleration sensor.
To accomplish the above objects, according to a first aspect of the present invention, there is provided a calibration method for an acceleration sensor in a storage device comprising a storage medium, a head for reading data from the storage medium, an actuator for positioning the head with respect to the storage medium, an enclosure for accommodating said storage medium, said head and said actuator, an acceleration sensor for detecting an acceleration of the enclosure, and a control circuit for calculating a first command value from an output of said acceleration sensor and a sensitivity of said acceleration sensor and then calculating a drive current value of said actuator from said first command value and a second command value for servo control. The calibration method comprises a step of exciting said actuator by flowing a drive current having a predetermined value, a step of calculating the acceleration of the enclosure from the predetermined current value and a mechanical transfer function of the storage device, a step of detecting a measured value of the acceleration sensor, and a step of calculating the sensitivity of the acceleration sensor from the calculated acceleration and from the detected measured value.
And a storage device comprises a storage medium, a head for reading data from said storage medium, an actuator for positioning said head with respect to said storage medium, an enclosure for accommodating said storage medium, said head and said actuator, an acceleration sensor for detecting an acceleration of said enclosure, and a control circuit having a seek process mode for calculating a first command value from an output of said acceleration sensor and a sensitivity of said acceleration sensor and then calculating a drive current value of said actuator from said first command value and a second command value for servo control, and a calibration process mode for calculating the sensitivity of said acceleration sensor from the output of said acceleration sensor when exciting said actuator and a drive current value of said actuator when exciting said actuator.
The present invention involves the use of a fiducial frame construction of which a mechanical transfer function is known. The fiducial frame construction is configured that an enclosure encasing the respective components of the storage device is fixed to a frame of a personal computer etc by a method of fixing the actual enclosure. This fiducial frame construction has the mechanical transfer function based on the enclosure and the fixing method.
The acceleration sensor is mounted on the enclosure fixed to the frame having the above known transfer function. Then, the actuator performs a seek operation, and an output of the acceleration sensor is measured. A value of the acceleration with this seek operation can be, with the mechanical transfer function being known, calculated from an electric current flowed and the mechanical transfer function. A sensitivity of the acceleration sensor can be obtained by comparing the thus calculated acceleration value of the enclosure with the measured value.
According to a second aspect of the invention, the exciting step comprises a step of flowing a seek current for accelerating and decelerating the actuator.
According to a third aspect of the invention, the exciting step includes a step of flowing a drive current for seeking the actuator in a forward direction, and a step of flowing a drive current for seeking the actuator in a reverse direction.
According to a fourth aspect of the invention, the exciting step includes a step of flowi
Aikawa Koichi
Jinzenji Akihide
Sasamoto Tatsuro
Yoshida Susumu
Bui Bryan
Fujitsu Limited
Greer Burns & Crain Ltd.
Hoff Marc S.
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