EP0265138A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Position control system for information storage system
Assignee: Fujitsu Ltd
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Filing: 1987-10-13
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Granted: —
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Expires: 2007-10-13
Abstract
Abstract A position control system for an information storage system, for example, an optical disc system, includes a stepping motor (7) for moving a read-write head (2) and a DC motor (32) for moving a beam reflecting unit (25), such as an object lens mounted on the head, which drives the stepping motor (7) to compensate a positional error of the beam reflecting unit (25) in a tracking mode after a seek without disturbing the movement of the beam reflecting unit (25). The position control system includes a master control unit operatively connected to a host controller, a stepping motor control unit (8), and a track servo control unit (4). The master control unit activates the stepping motor control unit (8) for a seek operation upon receipt of a seek command from the host controller. The stepping motor control unit (8) drives the stepping motor with a large drive current until the head moved by the stepping motor (7) reaches a position adjacent to a target track on the recording medium. In a tracking operation after the seek operation, the master control unit changes a mode of the stepping motor control unit (8) to the tracking operation and activates the track servo control unit (4). The track servo control unit (4) drives the DC motor (32) in response to a positional error of the head at the target track to finely control a position of the head at the target track. The stepping motor control unit (8) drives the stepping motor (7) by a predetermined rotation angle with a small drive current to compensate a position of the access end when the position of the beam reflecting unit (25) exceeds a limit of a controllable range of the beam reflecting unit (15).
Inventors
- 👤 Shigeyoshi C/O Fujitsu Shimonoge-Ryo Tanaka
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 07:29
CPC Classifications
G; G11; G11B; G11B21/00; G11B21/02; G11B21/10; G11B7/00; G11B7/08; G11B7/085; G11B7/08505; G11B7/08517; G11B21/08; G11B21/081; G11B21/083; G11B21/085
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
319 words
A position control system for an information storage system comprising a rotatable recording medium (10) having a plurality of tracks, a read-write head (2) movable across said tracks, and a beam reflecting unit (25) mounted on said head, adjacent to said recording medium, and movable for tracking a plurality of tracks, a DC motor (32) coupled to said beam reflecting unit to drive said beam reflecting unit to track on said tracks, and a stepping motor (7) coupled to said head, comprising: master control means (61) operatively connected to a host controller; stepping motor control means (62, 8) operatively connected to said master control means and said stepping motor; and track servo control means (64, 4) operatively connected to said master control means and said DC motor, said master control means activating said stepping motor control means for a seek operation upon receipt of a seek command from said host controller, and said stepping motor control means driving said stepping motor with a large drive current in response to a drive command from said master control means until said head moved by said stepping motor reaches a position adjacent to a target track on said recording medium, and in a tracking operation after said seek operation, said master control means changing a mode of said stepping motor control means to said tracking operation and activating said track servo control means, said track servo control means driving said DC motor in response to a positional error of said head at said target track to finely control a position of said head at said target track, and said stepping motor control means driving said stepping motor by a predetermined rotation angle with a small drive current to compensate a position of said beam reflecting unit when the position of said beam reflecting unit exceeds a limit of a controllable range of said beam reflecting unit by said track servo control means.
Claim 2
Dependent Claim
319 words
A position control system for an information storage system comprising a rotatable recording medium (10) having a plurality of tracks, a read-write head (2) movable across said tracks, and a beam reflecting unit (25) mounted on said head, adjacent to said recording medium, and movable for tracking a plurality of tracks, a DC motor (32) coupled to said beam reflecting unit to drive said beam reflecting unit to track on said tracks, and a stepping motor (7) coupled to said head, comprising: master control means (61) operatively connected to a host controller; stepping motor control means (62, 8) operatively connected to said master control means and said stepping motor; and track servo control means (64, 4) operatively connected to said master control means and said DC motor, said master control means activating said stepping motor control means for a seek operation upon receipt of a seek command from said host controller, and said stepping motor control means driving said stepping motor with a large drive current in response to a drive command from said master control means until said head moved by said stepping motor reaches a position adjacent to a target track on said recording medium, and in a tracking operation after said seek operation, said master control means changing a mode of said stepping motor control means to said tracking operation and activating said track servo control means, said track servo control means driving said DC motor in response to a positional error of said head at said target track to finely control a position of said head at said target track, and said stepping motor control means driving said stepping motor by a predetermined rotation angle with a small drive current to compensate a position of said beam reflecting unit when the position of said beam reflecting unit exceeds a limit of a controllable range of said beam reflecting unit by said track servo control means.
Claim 3
Dependent Claim
63 words
A position control system according to claim 1, wherein said track servo control means continuously moves said beam reflecting unit through said DC motor to track said beam reflecting unit over a plurality of tracks within said controllable range in response to a continuous read or write command for a plurality of tracks from said host controller and given through said master controller.
Claim 4
Dependent Claim
33 words
A position control system according to claim 1, wherein, in said tracking operation mode, said stepping motor control means and said track servo control means are operable independently and at a same time.
Claim 5
Dependent Claim
50 words
A position control system according to claim 3, said small drive current supplied to said stepping motor is defined so that an acceleration applied to said head by driving said stepping motor substantially permits a continuous servo control of said track servo means to follow the movement of said head.
Claim 6
Dependent Claim
36 words
A position control system according to claim 1, wherein said predetermined rotation angle of said stepping motor is defined by a number of phases of said stepping motor and a drive method for said stepping motor.
Claim 7
Dependent Claim
32 words
A position control system according to claim 5, wherein said stepping motor comprises a two-phase stepping motor, said drive method is a 1-2 phase excitation method, and said rotation angle is 45°.
Claim 8
Dependent Claim
36 words
A position control system according to claim 5, wherein said stepping motor comprises an n -phase stepping motor, said drive method is a microstep drive method m , and said rotation angle is (90°/m) × (2/n).
Claim 9
Dependent Claim
43 words
A position control system according to claim 1, wherein said large drive current supplied to said stepping motor in the seek operation has a maximum amplitude to be supplied to said stepping motor and is defined so that said seek time is minimized.
Claim 10
Dependent Claim
25 words
A position control system according to claim 8, wherein said large drive current is further defined so that the movement of said head is smooth.
Claim 11
Dependent Claim
46 words
A position control system according to claim 9, wherein said stepping motor comprises a multi-phase stepping motor and said stepping motor control means drives said stepping motor by a microstep drive method, so that said stepping motor is smoothly driven and said seek time is minimized.
Claim 12
Dependent Claim
51 words
A position control system according to claim 1, wherein said information storage system is an optical disc system comprising a rotatable optical disc, an optical read-write head, an object lens mounted on said optical disc, a DC motor coupled to said object lens, and a stepping motor coupled to said head.
Claim 13
Dependent Claim
17 words
A position control system according to claim 11, wherein said DC motor comprises a voice coil motor.
Claim 14
Dependent Claim
62 words
A position control system according to claim 11, wherein said optical disc system further comprises first position sensor means (25, 24, 23, 26, 29, 14) for optically sensing a position of said focused light beam from said object lens to the track and changing the optically sensed signal to an electrical signal which is fed back to said track servo control means.
Claim 15
Dependent Claim
67 words
A position control system according to claim 13, wherein said optical disc system further comprises second position sensor means (5) for detecting a status over said controllable range of said track servo control means, and wherein said stepping motor control means drives said stepping motor at the low speed by said predetermined rotation angle in a direction for entering said beam reflecting unit into said controllable range.
Claim 16
Dependent Claim
97 words
A position control system according to claim 14, wherein said track servo control means comprises a DC motor controller (64) and a track servo unit (4), said DC motor controller operating in said tracking mode and giving said target track, which can be changed in response to said continuous read or write for the plurality of tracks, to said track servo unit, and said track servo unit carrying out control of a position of said object lens through said DC motor at said target track in response to said position signal from said first position sensor means.
Claim 17
Dependent Claim
30 words
A position control system according to claim 15, wherein said second position sensor means detects said status from a control signal from said track servo unit to said DC motor.
Claim 18
Dependent Claim
130 words
A position control system according to claim 14, wherein said stepping motor control means comprises first control means, second control means, and a drive circuit unit having at least one drive circuit connected to a coil(s) of said stepping motor, said first control means driving said stepping motor with a large drive current output from said drive unit in said seek mode, to move said head to a portion adjacent to said target track, said second control means driving said stepping motor with a small drive current by said predetermined rotation angle in said direction, and said drive circuit unit outputting said large drive current or said small drive current in response to a control signal from said first control means or another control signal from said second control means.
Claim 19
Dependent Claim
171 words
A position control system comprising: a first controlled object (100); a second controlled object (200) mounted on said first controlled object; a DC motor (300) coupled to said second controlled object for moving said second controlled object; a stepping motor (500) coupled to said first controlled object; long distance control means (600) operatively connected to said stepping motor for driving said stepping motor for moving said first controlled object for a long distance at a high speed, in a first operation mode; servo control means (400) operatively connected to said DC motor and controlling a position of said second controlled object in a second operation mode; and short distance control means (700), operatively connected to said stepping motor being operative independently to said servo control means and at a same time, for driving said stepping motor by a predetermined rotation angle at a low speed in said second operation mode, when a controllable range of said servo control means is exceeded, to compensate a positional error of the servo control means.
Claim 20
Dependent Claim
171 words
A position control system comprising: a first controlled object (100); a second controlled object (200) mounted on said first controlled object; a DC motor (300) coupled to said second controlled object for moving said second controlled object; a stepping motor (500) coupled to said first controlled object; long distance control means (600) operatively connected to said stepping motor for driving said stepping motor for moving said first controlled object for a long distance at a high speed, in a first operation mode; servo control means (400) operatively connected to said DC motor and controlling a position of said second controlled object in a second operation mode; and short distance control means (700), operatively connected to said stepping motor being operative independently to said servo control means and at a same time, for driving said stepping motor by a predetermined rotation angle at a low speed in said second operation mode, when a controllable range of said servo control means is exceeded, to compensate a positional error of the servo control means.
References Cited (Backward Citations)
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