Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1999-12-02
2001-05-15
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S124010, C360S069000
Reexamination Certificate
active
06233212
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a disk data drive and more precisely to optimizing a disk rotation speed in such a disk data drive.
BACKGROUND OF THE INVENTION
A disk data drive uses a disk shaped data carrier to read and/or write data. Examples of disk data drives may be optical, opto-magnetic or magnetic data drives. Typically such disk data drives allow to remove and insert optical (Compact Disks, Digital Versatile Disks), opto-magnetic and/or magnetic disks. The inserted disk is rotated inside the drive by means of a motor to which a motor current is fed. Once the disk is rotating data may be read from and/or written to the disk using appropriate reading and/or writing means.
A rate of data reading and/or writing, i.e., a quantity of information per unit of time read from and/or written to the disk is dependent on a disk rotation speed. More precisely the greater the disk rotation speed the greater the achievable rate of data reading and/or writing. Due to imperfections of the disk or of the disk data drive a high disk rotation speed may lead to vibrations or other problems which eventually result in data reading and/or writing errors. Therefore the disk rotation speed needs to be adjusted as high as possible but in a way that a tolerable number of reading and/or writing errors occurs.
SUMMARY OF THE INVENTION
The method for monitoring and adjusting a motor current in a disk data drive such to optimise a rotational speed of a disk actuated by a motor with said motor current according to the invention comprises the steps of
a) driving the motor at a certain value of a first property,
b) measuring the value of a certain second property,
c) comparing the measured value of the second property to a nominal value of the second property for said first property,
d) keeping the value of the first property constant if the measured value deviates from the nominal value and
e) else changing the first property and continuing with step b). This method has the advantage, that the optimum rotational speed of a disk can be determined independent of the fact whether the disk can be read by the device or if it is unreadable. That means, directly after inserting the disk into the device the method according to the invention may be performed and delivers the optimum value of the rotational speed for said disk. That means, it is not necessary to adapt certain parameters of the device functions to the properties of the disk before the optimum rotational speed can be determined.
According to a first variant of the invention, it is started with a low value of the first property and the first property is kept constant only if the measured value exceeds the nominal value, else the value of the first property is increased. This has the advantage, that the method is started under safe conditions, that means under conditions, which are most likely below the optimum value of the first property. The device works without problems, e.g. such caused by eccentricity or bad flatness, under these conditions. The value of the first property is increased until the optimum, the maximum acceptable value of the first property is reached.
According to another variant of the invention, the method is started with a maximum value of the first property. This has the advantage, that in case of high quality disks, which exhibit only very small eccentricity, the optimum value might be reached much more quickly, because for these disks, the optimum value of the first property most likely does not deviate much from the maximum value. If, in average, more high quality disks are used than low quality disks, this variant of the inventive method most likely leads quickly to the desired result.
According to still another variant of the invention the method is started with a certain medium value of the first property which is afterwards increased or decreased depending on whether it exceeds or falls below a threshold being the nominal value. The further steps are similar as described above. This variant of the method has the advantage, that the medium value with which the method is started may be chosen to be a value which most likely equals the optimum value. This value might be determined by averaging the maximum acceptable values for a big number of different disks. In this case only very few steps will have to be performed to reach the optimum value. This means that the device, in average, will be available for the user very quickly after being turned on or after a new disk has been inserted.
According to a first solution of the invention the first property is the rotational speed of the motor while the second property is the motor current of the motor. This has the advantage, that usually the motor of such device is controlled to run at a certain rotational speed. In this case it is sufficient to add the possibility to measure the motor current in order to perform the inventive method. No changes of control devices or control strategy is necessary.
According to a second solution of the invention, the first property is the motor current while the second property is the rotational speed of the motor. This has the advantage, that the motor current may not exceed a maximum allowable value because it is regulated according to a predefined strategy. This leads to a limitation of energy consumption as well as to reduced wear of the device and thus to enlarged lifetime. Deviation of actual value and nominal value in this case has the opposite meaning of the one for the first solution.
Advantageously the value of the first property is kept constant if the actual value of the first property equals a maximum allowable value of the first property of the device independent of whether the criteria for the optimum value of the first property are already reached or not. This also has the advantage not to exceed the maximum allowable or desirable motor current or motor speed or disk speed, respectively. In case of a very good disk, exhibiting nearly no eccentricity and having good flatness, and in case of optimum conditions of the device the conditions of the method set for determination of optimum speed might not be reached before the maximum speed of the device is reached. By cutting off the increase of rotational speed or motor current, respectively, wear is reduced and thus lifetime of the device is increased.
Measuring the value of the second property advantageously includes measuring several samples of the second property and generating a mean value therefrom. Using a mean value has the advantage, that errors caused by erroneously detected extremely high or extremely low values do not have negative influence on the method. A further advantage lies in the fact that measurement can be started even before a stable state after switching to a different value of the first property is reached. Otherwise it would be necessary to wait until such stable state is surely reached. A further advantage lies in the fact that if the control characteristic is very fast, which includes that deviations around the mean value may exist for a certain prolonged time, even these deviations or oscillations are filtered out by generating the mean value.
According to a variant of the invention the value of the first property is reduced about a certain amount before being kept constant. This has the advantage, that the criteria for no longer increasing the value of the first property may well lie a little bit above the optimum value, as this value is reduced afterwards about said predefined certain amount. This means that the steps for changing the value of the first property might be taken relatively large because after having reached the criteria for optimum value the actual value is reduced for example about half the value about which the first property it was changed before. The large steps for changing the value of the first property which large steps are possible according this variant of the invention make possible even more quickly reaching the optimum value.
The inventive method is performed each time a different disk is inserted i
Deutsche Thomson-Brandt GmbH
Edun Muhammad
Kiel Paul P.
Tripoli Joseph S.
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