A method of, and an apparatus for, controlling the position of a data transducer head

Claim 1

A method of controlling the position of a data transducer head so that it follows a predetermined track on a record disk, the method comprising:- applying a driving current of set value to a driving means for positioning the head; using the head to sample servo position information in a sector on a disk record medium to detect the position of the head at a present sampling instant; detecting the velocity of the head at the present sampling instant; and deriving a new basic value for the driving current from the position and velocity of the head detected at the present sampling instant; the method being characterised by setting a new value for the driving current by modifying the new basic value in dependence on the difference between the set acceleration of the head based on the value of the driving current set after the previous sampling instant and the actual acceleration of the head calculated from the difference in velocity of the head at the previous and the present sampling instants.

Claim 2

A method of controlling the position of a data transducer head so that it follows a predetermined track on a record disk, the method comprising:- applying a driving current of set value to a driving means for positioning the head; using the head to sample servo position information in a sector on a disk record medium to detect the position of the head at a present sampling instant; detecting the velocity of the head at the present sampling instant; and deriving a new basic value for the driving current from the position and velocity of the head detected at the present sampling instant; the method being characterised by setting a new value for the driving current by modifying the new basic value in dependence on the difference between the set acceleration of the head based on the value of the driving current set after the previous sampling instant and the actual acceleration of the head calculated from the difference in velocity of the head at the previous and the present sampling instants.

Claim 5

An apparatus for controlling the position of a data transducer head so that it follows a predetermined track on a record disk, the apparatus comprising:- a head driving means (20);- a velocity detector (8) for detecting the velocity of the head; a position detector (9) for detecting the position of the head; a velocity value storage means (7) for storing the values of head velocity detected by the velocity detector; a current value storage means (6) for storing the current value set to be applied to the head driving means; a basic current value deriving means (2) for deriving a basic current value from the head position and velocity detected by the position and velocity detectors, respectively; an actual acceleration deriving means (5) for deriving the actual acceleration of the head from the difference between the velocity at a present sampling instant and the velocity at the previous sampling instant, the latter velocity being obtained from the velocity value storage means; a set acceleration calculator (4) for calculating a set acceleration from the set current value stored in the current value storage means, that current value having been set after the previous sampling instant; a corrected current value calculator (3) for calculating a corrected current value corresponding to the difference between the actual acceleration and the set acceleration; a new current value setting means (1) for setting a new current value determined by the basic current value and the corrected current value; and means for reading the new current value into the current value storage means.

Claim 6

An apparatus for controlling the position of a data transducer head so that it follows a predetermined track on a record disk, the apparatus comprising:- a head driving means (20);- a velocity detector (8) for detecting the velocity of the head; a position detector (9) for detecting the position of the head; a velocity value storage means (7) for storing the values of head velocity detected by the velocity detector; a current value storage means (6) for storing the current value set to be applied to the head driving means; a basic current value deriving means (2) for deriving a basic current value from the head position and velocity detected by the position and velocity detectors, respectively; an actual acceleration deriving means (5) for deriving the actual acceleration of the head from the difference between the velocity at a present sampling instant and the velocity at the previous sampling instant, the latter velocity being obtained from the velocity value storage means; a set acceleration calculator (4) for calculating a set acceleration from the set current value stored in the current value storage means, that current value having been set after the previous sampling instant; a corrected current value calculator (3) for calculating a corrected current value corresponding to the difference between the actual acceleration and the set acceleration; a new current value setting means (1) for setting a new current value determined by the basic current value and the corrected current value; and means for reading the new current value into the current value storage means.