Dynamic information storage or retrieval – Specific detail of information handling portion of system – Mechanical modification or sensing of storage medium
Patent
1986-12-22
1989-02-07
McElheny, Jr., Donald
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Mechanical modification or sensing of storage medium
G11B 1920, G11B 2110
Patent
active
048036765
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns for an audio or video disk player.
Carrying out the requisite servo track readjustment by means of coarse-drive and precision-drive mechanisms, whereby the coarse-drive mechanism always carries out a motion once a prescribed threshold attained by integration of a radial error signal has been attained, is known for a track-guidance system for players for playing back audio and/or video disks. The function of the precision-drive mechanism is to rapidly control radial fluctuations in the track up to specific amplitudes.
The drawback to this known system is that the coarse-drive mechanism rotates irregularly once the response voltage for the coarse-drive mechanism has been attained. This is due to the more or less extensive and random energy consumption of the coarse-drive mechanism and its differing start-up action.
SUMMARY OF THE INVENTION
The object of the invention is to provide a circuit for a track-readjustment system that will ensure unobjectionable collaboration between the precision-drive and coarse-drive mechanisms.
The invention will now be specified with reference to the drawings.
p BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a known radial servo circuit with coarse-drive and precision-drive mechanisms,
FIG. 2 illustrates a threshold component in the form of a comparator,
FIG. 3 illustrates a threshold component with three comparators, and
FIG. 4 illustrates a threshold component for the weighted deactivation of the coarse-drive mechanism by means of an a/d (analog to digital) converter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a known radial servo circuit with coarse-drive (coarse positioning actuator) and precision-drive mechanisms (fine tracking actuator). A radial-error signal U.sub.R is supplied to the servo circuit. A radial control circuit 1 processes error signal 8 and supplies on the one hand a control signal U.sub.F for precision-drive mechanism 2 and also a control signal that assumes starting up of coarse-drive mechanism 3 through an integrator 4 and 5. For SEARCH, a SEARCH-control signal 9 changes a switch 6 to SEARCH signal 7 and starts coarse-drive mechanism 3 moving.
The known devices derive an electric signal from the servo circuit for precision-drive mechanism 2 that is supplied to coarse-drive mechanism 3 through integrator 4 and 5. The particular error signals U.sub.R, which provide for the control of precision-drive mechanism 2, are all integrated up until the voltage at the output terminal of integrator 4 and 5 is high enough for coarse-drive mechanism 3 to carry out a rotation. This makes the precision-drive mechanism skip back until coarse-drive mechanism 3 comes into play again as the result of integration.
The drawback to this known system is that, once the response voltage for coarse-drive mechanism 3 has been attained, the mechanism executes a rotation of varying extent. This is due to the more or less extensive and random energy consumption of the coarse-drive mechanism and to its variable start-up action as the result of friction and manufacturing tolerances.
The back-skip of precision-drive mechanism 2 is accordingly variable in extent, so that the optimum operating range for precision-drive mechanism 2 can be exceeded. Unobjectionable scanning can then no longer be ensured. In order to ensure unobjectionable scanning in spite of this, coarse-drive mechanism 3 must be employed with high precision. Variations in the friction or pole sensitivity of the coarse-drive mechanism for example can occasion variations in the angle of rotation when the response voltage is attained. Furthermore, the response voltage can vary in strength depending on the position of the driveshaft. The consequence is also undesirable and indefinite rotations on the part of the coarse-drive mechanism.
In the SEARCH mode, the scanner will execute a long radial skip. When the servo loop for precision-drive mechanism 2 is closed and the motion of coarse-drive mechanism 3 is not yet completely concluded, the prescr
REFERENCES:
patent: 4037252 (1977-07-01), Janssen
patent: 4234837 (1980-11-01), Winslow
patent: 4330880 (1982-05-01), Van Dijk
patent: 4494154 (1986-01-01), Akiyama
patent: 4498158 (1985-02-01), Akiyama
patent: 4567533 (1986-01-01), Assink
Deutsche Thomson-Brandt GmbH
Fogiel Max
McElheny Jr. Donald
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