Transducer positioning system for providing coarse positioning

Claim 2

A servo system for positioning a transducer means relative to a group of at least three tracks provided on a relatively moving recording medium, said system comprising: controllable positioning means for moving said transducer means transversely relative to said tracks; a plurality of servo data manifestations recorded in each track constituting a plurality of adjacent cells, each cell having a manifestation at either a first or a second location of the cell indicative of either a first or a second value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of the group, the cells being encoded so as to provide: (a) a different identifying representation for each track of the group so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence chosen for the group of tracks so that the value of only one cell is different on adjacent tracks; and detecting means responsive to the detection by said transducer means of the differently encoded servo data manifestations provided in each track of said group of tracks for controlling said positioning means relative to said group of tracks.

Claim 3

The invention in accordance with claim 1, wherein said detecting means includes: first means providing an output indicative of the distance between the current track position of said transducer means and a target track; and second means for updating said first means in accordance with the detected radial movement of said transducer means.

Claim 4

The invention in accordance with claim 1, wherein said recording medium is magnetic, wherein said transducer means is a magnetic head, wherein said servo data manifestations are provided as magnetic transitions, and wherein a common reference transition is provided for each track with respect to which the respective cells in the tracks are precisely located.

Claim 5

The invention in accordance with claim 3, wherein said detecting means includes means responsive to the reading of said magnetic transitions by said magnetic head for producing for each cell traversed by said head: (a) a single electrical signal at a time corresponding to either said first or second location of a cell when said transducer means is approximately centered over a track, and (b) two electrical signals at times respectively corresponding to both of said first and second locations of a cell when said transducer means is between two adjacent tracks and is reading a cell whose value is different for the two adjacent tracks.

Claim 6

The invention in accordance with claim 3, wherein said recording means includes a rotatable disc in transducing relationship to said magnetic head, wherein said tracks are concentrically located on said disc, and wherein said positioning means is adapted to provide for radial movement of said head.

Claim 7

The invention in accordance with claim 5, wherein said servo data manifestations are provided in servo data tracks located in predetermined spaced servo data sectors of said disc.

Claim 8

The invention in accordance with claim 6, wherein work data is recorded on and reproduced from work data tracks in work data sectors located between said servo data sectors on said disc.

Claim 9

The invention in accordance with claim 7, wherein a plurality of like encoded groups of tracks are provided on said disc at successive radial locations, and wherein the number of servo data tracks provided in each group is chosen to be greater than the maximum radial movement of said magnetic head between servo sectors.

Claim 10

The invention in accordance with claim 8, wherein said detecting means includes: counting means providing a count indicative of the radial distance between the current track position of said magnetic head and a target track; and means responsive to said electrical signals for determining current track position of said head relative to its respective group and for changing the count of said counting means in accordance with the radial distance that the head has moved since the previous servo sector.

Claim 11

The invention in accordance with claim 9, wherein said detecting means includes means responsive to the servo data manifestations detected by said magnetic head for controlling said positioning means to return said magnetic head to said target track in response to said counting means indicating that said head has moved a predetermined radial distance from the target track after having arrived at the target track.

Claim 12

A recording and reproducing medium for use in a servo system for positioning a relatively moving transducer means tranversely with respect to a plurality of groups of tracks provided on said medium, each group containing at least three tracks, said medium containing servo data manifestations recorded in each track so as to constitute a plurality of adjacent cells each having a manifestation at either a first or a second location of the cell indicative of either a first or a second value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells of the tracks in each group being encoded so as to provide: (a) a different identifying representation for each track of a group so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group of tracks chosen so that the value of only one cell is different on adjacent tracks.

Claim 13

A recording and reproducing medium for use in a servo system for positioning a relatively moving transducer means tranversely with respect to a plurality of groups of tracks provided on said medium, each group containing at least three tracks, said medium containing servo data manifestations recorded in each track so as to constitute a plurality of adjacent cells each having a manifestation at either a first or a second location of the cell indicative of either a first or a second value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells of the tracks in each group being encoded so as to provide: (a) a different identifying representation for each track of a group so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group of tracks chosen so that the value of only one cell is different on adjacent tracks.

Claim 14

The invention in accordance with claim 11, wherein said encoding sequence employs a Gray code.

Claim 15

The invention in accordance with claim 11, wherein said recording medium is a magnetic disc, wherein said tracks are concentrically located on said disc, and wherein each of said servo data manifestations is provided as a magnetic transition.

Claim 16

The invention in accordance with claim 13, wherein each track includes a reference transition aligned with the reference transitions of the other tracks in each group, and wherein respective cells in said tracks and said first and second locations thereof are spaced like predetermined distances from said reference transition.

Claim 17

The invention in accordance with claim 14, wherein said recording medium is magnetic, and wherein said servo data manifestations are recorded in said medium as magnetic transitions.

Claim 18

In a method for positioning a transducer means transversely relative to a group of at least three tracks provided on a relatively moving recording medium, the improvement comprising: recording servo data manifestations so as to provide a reference manifestation and a plurality of adjacent cells in each track, each cell having a manifestation at either a first or a second location of the cell indicative of either a first or a second value for the cell, said reference manifestation and said cells and said first and second locations thereof being respectively aligned for all tracks of the group, the cells being encoded so as to provide: (a) a different identifying representation for each track of the group so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for the group of tracks chosen so that the value of only one cell is different on adjacent tracks.

Claim 19

In a method for positioning a transducer means transversely relative to a group of at least three tracks provided on a relatively moving recording medium, the improvement comprising: recording servo data manifestations so as to provide a reference manifestation and a plurality of adjacent cells in each track, each cell having a manifestation at either a first or a second location of the cell indicative of either a first or a second value for the cell, said reference manifestation and said cells and said first and second locations thereof being respectively aligned for all tracks of the group, the cells being encoded so as to provide: (a) a different identifying representation for each track of the group so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for the group of tracks chosen so that the value of only one cell is different on adjacent tracks.

Claim 20

In a method for positioning a magnetic transducer means transversely relative to a plurality of concentric tracks provided on a rotatable magnetic disc, the improvement comprising: recording work data and servo data in alternative sectors of a magnetic disc, said servo data being recorded in each servo sector as a plurality of repeating groups of servo tracks, each servo track containing recorded magnetic transitions constituting a plurality of adjacent cells, each cell having a transition at either a first or a second location of the cell indicative of either a first or second binary value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells being encoded so as to provide: (a) a different binary representation for each track of a group of servo tracks so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group chosen so that the value of only one cell is different on adjacent servo tracks.

Claim 21

In a method for positioning a magnetic transducer means transversely relative to a plurality of concentric tracks provided on a rotatable magnetic disc, the improvement comprising: recording work data and servo data in alternative sectors of a magnetic disc, said servo data being recorded in each servo sector as a plurality of repeating groups of servo tracks, each servo track containing recorded magnetic transitions constituting a plurality of adjacent cells, each cell having a transition at either a first or a second location of the cell indicative of either a first or second binary value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells being encoded so as to provide: (a) a different binary representation for each track of a group of servo tracks so that each track of the group is identifiable from the coding provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group chosen so that the value of only one cell is different on adjacent servo tracks.

Claim 22

In a method for positioning magnetic transducer means transversely relative to a group of tracks provided on a rotatable magnetic disc, the improvement comprising: recording servo data in spaced sectors of a magnetic disc, said servo data being recorded in each servo sector as a plurality of repeating groups of servo tracks, each servo track containing recorded magnetic transitions constituting a plurality of adjacent cells, each cell having a transition at either a first or a second location of the cell indicative of either a first or second binary value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells being encoded so as to provide: (a) a different binary representation for each track of a group of servo tracks so that each track of the group is identifiable from the binary representation provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group chosen so that the value of only one cell is different on adjacent servo tracks, the number of servo tracks provided in each group being chosen greater than the maximum radial movement of said transducer means between servo sectors; providing an indication of the number of tracks and direction that said transducer means is to be moved from its current track position to a target track; moving said transducer means in said direction towards said target track; detecting during said moving the current track position of said transducer means by detecting the magnetic transitions traversed thereby during a servo sector; and updating said indication during each sector based on the difference between the current detected position of said transducer means and that detected during the previous servo sector.

Claim 23

In a method for positioning magnetic transducer means transversely relative to a group of tracks provided on a rotatable magnetic disc, the improvement comprising: recording servo data in spaced sectors of a magnetic disc, said servo data being recorded in each servo sector as a plurality of repeating groups of servo tracks, each servo track containing recorded magnetic transitions constituting a plurality of adjacent cells, each cell having a transition at either a first or a second location of the cell indicative of either a first or second binary value for the cell, the cells and said first and second locations thereof being respectively aligned for all tracks of each group, the cells being encoded so as to provide: (a) a different binary representation for each track of a group of servo tracks so that each track of the group is identifiable from the binary representation provided for its respective plurality of adjacent cells, and (b) an encoding sequence for each group chosen so that the value of only one cell is different on adjacent servo tracks, the number of servo tracks provided in each group being chosen greater than the maximum radial movement of said transducer means between servo sectors; providing an indication of the number of tracks and direction that said transducer means is to be moved from its current track position to a target track; moving said transducer means in said direction towards said target track; detecting during said moving the current track position of said transducer means by detecting the magnetic transitions traversed thereby during a servo sector; and updating said indication during each sector based on the difference between the current detected position of said transducer means and that detected during the previous servo sector.