Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2002-02-25
2004-06-29
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077020, C360S061000, C318S599000, C318S590000
Reexamination Certificate
active
06757129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a control technique of a magnetic disk storage apparatus. More specifically, the present invention is directed to a control technique of a voice coil motor capable of moving a magnetic head for reading/writing information with respect to a storage track formed on a magnetic storage disk to be rotatably driven.
2. Description of the Related Art
A magnetic disk storage apparatus is provided with a magnetic head, a voice coil motor, and a voice coil motor drive control circuit. The magnetic head reads/writes information with respect to storage tracks formed on a magnetic storage disk which is rotatably driven in a high speed. The voice coil motor moves this magnetic head on the magnetic storage disk in both a seek move manner and a tracking move manner. The voice coil motor drive control circuit controls a drive current of the voice coil motor, while monitoring a read condition of the magnetic head, in order to perform a positioning operation of the magnetic head.
While information storage density of magnetic disk storage apparatus is increased year after year, highly precise positioning control operations of magnetic heads are required in connection with this high storage density requirement. Under such a circumstance, the positioning system of the magnetic head has been employed in which the drive current of the above-described voice coil motor is feedback-controlled based upon the detected value of this drive current. Then, generally speaking, in order to drive the voice coil motor for moving this magnetic head, such a liner drive system has been employed in which the drive current amount of the voice coil motor is changed in the continuous manner.
The above-described conventional techniques own the below-mentioned problems which could be revealed by the Inventors of the present invention.
That is, in a magnetic disk storage apparatus, high density storage operation is required and also, highspeed across operation is required. In order to realize such highspeed access operation, time during which a magnetic head is moved to a predetermined storage track of a magnetic disk, namely, so-called “seek time” should be shortened. To reduce the seek time, a drive current of a voice coil motor should be increased. However, when the drive current of the voice coil motor is increased, power loss required to control this motor drive current in the linear manner is increased, resulting in an increase of a heat generation amount. This heat generation occurred during the seek operation may give adverse influences to operations and characteristics of the magnetic head and the magnetic storage disk. As a result, for instance, there is such a problem that read/write errors may be easily produced.
To reduce the above-explained heat generation, the Inventors of the present invention have studied that the above-described drive current of the voice coil motor is controlled in the pulse width modulation control manner (will be referred to as a “PWM control” hereinafter). In other words, the Inventors of the present invention have investigated such a pulse drive system. That is, while the drive current amount of the voice coil motor is not continuously changed, a ratio of turn-ON time to turn-OFF time of this drive current (namely, so-called “duty ratio”) is changed to execute the drive control of the voice coil motor. In this case, the drive control operation of the voice coil motor is carried out in such a manner that while the drive current amount of the voice coil motor is fixed to a value approximated to the maximum value, this ratio of the turn-ON to the turn-OFF of the drive current is changed. This drive system corresponds to one sort of switching control operation, and can achieve a very large effect as to the reduction of the power loss.
However, although this pulse drive system can have a merit as to the suppression of the heat generation amount by reducing the power loss, this pulse drive system can hardly realize high control precision, as compared with that of the above-explained linear drive system. In particular, this pulse drive system can hardly secure sufficiently high positioning precision of the magnetic head during the tracking operation in which the move amount of the magnetic head is small.
Under such a circumstance, the Inventors of the present invention has considered that when the large drive current of the voice coil motor is required so as to move the magnetic head in the seek mode and in highspeeds, the drive operation by the PWM control manner (namely, pulse drive mode) is carried out, whereas when the high precision drive control is required so as to perform the tracking control while the amplitude of the drive current is small, the drive operation by the linear control (namely, linear drive mode) is carried out. In this case, when the pulse drive operation and the linear drive operation are carried out by separately employing output amplifiers, the arrangement of the magnetic disk storage apparatus becomes complex and is manufactured in a large scale. In particular, the switching operation between the voice coil motor and the output amplifiers becomes very complex and very cumbersome. In order that the arrangement is not made complex, or in the large scale, the following manner is rational, namely, both the pulse drive operation and the linear drive operation may be commonly executed by the same output circuit.
In other words, the output amplifier which supplies the drive current to the voice coil motor is commonly used during both the pulse drive operation and the linear drive operation. To this end, the output amplifier is arranged in such a manner that the input of this output amplifier is used to switch the pulse drive mode and the linear drive mode in response to a magnitude of a control amount. When the pulse drive operation is carried out, the PWM-controlled pulse signal is entered to the output amplifier. In this case, this PWM-controlled pulse signal owns a sufficiently large amplitude in such a manner that the output amplifier may be fully operated over the dynamic range thereof. As a consequence, while the output amplifier is operated over the full dynamic range under which the output signal of this output amplifier becomes saturated, this output amplifier may supply the pulse drive current to the voice coil motor.
When the linear drive operation is carried out, since such an input signal whose level is changed in a linear mode in response to a change contained in control amounts is entered into the above-explained output amplifier, the voice coil motor is driven in the linear drive mode. In this case, this input signal corresponds to such a signal having a small amplitude which can be fully stored within the dynamic range of the output amplifier. More specifically, when the tracking operation is carried out during which the position of the magnetic head is controlled in the very precise manner, the output amplifier supplies a drive current to the voice coil motor under such a condition approximated to a zero level output.
As explained above, the output amplifier may be commonly used during both the pulse drive operation and the linear drive operation. As a consequence, while the construction of the magnetic disk storage apparatus is not made complex and in the large scale, the voice coil motor can be driven in accordance with such a drive system (namely, either pulse drive system or linear drive system) which is suitably selected during either the seek operation or the tracking operation.
However, it can be recognized that the above-described hybrid drive system of the pulse/linear drive modes own the following problems.
That is, in order that the PWM drive operation is effectively carried out, such an output amplifier operable with a large amplitude and in a high slew rate is necessarily required. In the pulse drive system, the electric power loss can be reduced by controlling the drive current in the high speed by way of the switching control manner. However
Kokami Yasuhiko
Kuroiwa Hiroshi
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Reed Smith LLP
Renesas Technology Corporation
Sniezek Andrew L.
LandOfFree
Magnetic disk storage apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic disk storage apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic disk storage apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3302340