Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2001-10-22
2004-08-31
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C360S073030, C369S053190
Reexamination Certificate
active
06785199
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a drive device that has a feed mechanism that causes a control object to move in order to control the positioning of said control object, a motor that serves as the drive source of the feed mechanism, and a control means that controls the motor by open-loop control; and can be used, for example, as a drive device to position an optical pickup in an optical disk device.
BACKGROUND OF THE INVENTION
An optical disk device that records and plays information on an optical disk such as a CD, DVD, CD-ROM, DVD-ROM, CD-R, DVD-R, etc. has an optical pickup that shines a laser light or other optical spot onto the optical disk and detects information or records information, and a drive device that adjusts the relative position between the optical disk and the optical pickup. Specifically, a drive mechanism will have a spindle servo mechanism, a tracking servo mechanism, a focusing servo mechanism, a slide feed mechanism, and a tilt servo mechanism; among these mechanisms, a stepping motor is adopted as the drive source for the slide feed mechanism and the tilt servo mechanism, and the stepping motor will have a driver IC [integrated circuit] for driving and a control means that outputs control commands to this driver IC.
With such a drive mechanism, by giving control commands to each stepping motor from the pulse step, the stepping motors can be precisely operated in accordance with the steps included in the control commands, which provides the advantage of being able to control the relative positioning of the two with high precision In such positioning control by stepping motors, when a stepping motor is operated continuously for a long time, the driver IC that drives this motor overheats, so a composition is adopted in which this driver IC is provided with a thermal shutdown circuit that includes a temperature detection unit. When the temperature detected by the temperature detection unit reaches or exceeds a fixed temperature, the motor drive is stopped.
However, stopping the motor drive by thermal shutdown in this way is an operation that is unforeseen by the control commands by the control means, so a difference will arise between the software feed amount based on the control commands and the actual feed amount In the case of open-loop control in particular, because there is no feedback of the actual feed position, there is the problem that such a difference in the feed amount cannot be solved, and accurate positioning control cannot be achieved. Such problems do not only arise in optical disk devices but are common problems in devices that include drive devices that control stepping motors, especially with open-loop control.
It is an object of the present invention to provide, in a drive device that has a feed mechanism that causes a control object to move in order to control the positioning of said control object, a motor that serves as the drive source of this feed mechanism, and a control means that controls this motor, a drive device that can perform accurate positioning control while avoiding the thermal shutdown that is associated with overheating of the driver IC that drives the motor.
SUMMARY OF THE INVENTION
The drive device of the present invention has a feed mechanism that causes a control object to move in order to control the positioning of said control object, a motor that serves as the drive source of the feed mechanism, and a control means that controls the motor. The control means has an operation history memory unit that stores the operation history of said motor, and a command selection unit that selects control commands and outputs them to said motor based on information stored in this operation history memory unit. Information about what state the motor is in immediately before outputting control commands is stored in the operation history memory unit, such as, for example, information stored on whether the control commands by the control means are due to the drive device being restarted. The command selection unit selects control commands with reference to the information stored in the operation history memory unit. For example, if the command selection unit judges, based on the information it references, that the drive device has restarted, it is thought that the motor is in operation prior to restarting, so the command selection unit selects a control command to cause the motor to operate intermittently.
Having an operation history memory unit and a command selection unit makes it possible to select the appropriate control commands according to the state of operation of the motors prior to generating and outputting the control commands. Accordingly, one can, while avoiding any thermal shutdown by the driver ICs that drive the motors, prevent the occurrence of any difference between the feed amount due to the control commands from the control means and the actual feed amount, and do accurate positioning control. In the case of an optical disk device restart command in particular, if the motor is made to operate intermittently, then the motor can be operated below the thermal shutdown temperature, and more accurate positioning control can be achieved. If the feed mechanism causes the control object to execute repetitive operation within a prescribed range, it is desirable that the control command to cause the motor to operate intermittently include a command to stop the motor at the turnback points of the repetitive operation. By thus including a command to stop the motor at the turnback points of the repetitive operation, at the turnback points the control object will be in the stopped state, so there is no possibility, even if the motor is stopped at this time, of the control object causing stop position displacement, etc. due to inertia, etc. Therefore, positioning control of the control object can be achieved even if it is a control system that does not feed back the position of the control object after control, such as open-loop control.
Furthermore, if said control object is an optical pickup that shines laser light or another optical spot onto an optical disk and records and/or plays information on said optical disk, it is desirable to adopt the present invention if one is to adjust the tilt position between the optical disk and the optical pickup. As stated above, the optical pickup of an optical disk device must execute various types of positioning control with respect to the optical disk, such as the tracking position, the focusing position, the slide feed position, and the tilt position, so adoption of the device of the present invention will be very significant In the case of tilt position control, because open-loop control is usually adopted in operation at the time of startup, it is possible to do high-precision positioning without any feedback of the actual feed amount
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US2001/0038743A!, Murata, DVD Video Player, Nov. 8, 2001, entire document 386/82.
Amemiya Hironobu
Ohtsu Hiroshi
Sugiyama Masaki
Katten Muchin Zavis & Rosenman
Psitos Aristotelis M.
Sony Computer Entertainment Inc.
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