Magnetic disc apparatus

Abstract

A magnetic disc apparatus wherein off-track quantities are stored with regard to reference servo tracks formed circularly in divided data areas on a magnetic disc and, at the time of displacing the magnetic head, the head is shifted an extent of the stored off-track quantity after being once positioned by a head position detector. Gradients of the off-track quantities corresponding to tracks at individual temperatures in the apparatus are previously stored and, after the actual temperature is detected by means of a temperature sensor, the off-track quantity relative to the reference servo track is corrected in accordance with the gradient of the off-track quantity to the relevant track at the detected temperature, whereby just tracking is achieved. The magnetic head can be positioned exactly with respect to a desired data track while the head displacement time is shortened. Furthermore, data can be written in the entire length of each circular data track to enhance the efficiency of utilizing the magnetic disc, and high-precision tracking is attainable with the off-track quantity reduced to zero in any data track.

What is claimed is: .[. 
     
       1.  A magnetic disc apparatus comprising: a magnetic disc having a plurality of track groups thereon each of which comprises plural data tracks and at least two reference tracks on which a servo signal is recorded, wherein the reference tracks are recorded in the center of each of the track groups:   transducer means for reading and writing data signals from and on the data tracks and reading the servo signal from a reference track;   actuator means for positioning the transducer means over a desired one of the tracks;   means connected to the transducer means for computing and generating a tracking error signal as a function of the servo signal read from the reference tracks;   memory means for storing the tracking error signal with respect to each of the track groups;   position sensing means for sensing the position of the transducer means relative to the magnetic disc and outputting a corresponding position signal, wherein the position sensing means generates N periodic signals, where N is an integer, which are out of phase with each other and there are N reference tracks within one track group; and   controller means, supplied with the output of the position sensing means, for controlling the actuator means according to the stored tracking error signal corresponding to the track group within which the transducer is to be positioned..]..[.   
     
     
       2.  A magnetic disc apparatus, comprising: a magnetic disc having a plurality of concentric data tracks and a reference region having N concentric servo tracks on which servo signals are prerecorded, wherein N is an integer greater than 2;   transducer means for reading and writing data signals on the data tracks and reading the servo signals from the servo tracks;   actuator means for positioning the transducer means over a desired one of the tracks;   position sensing means for sensing the position of the transducer means relative to the magnetic disc, and for generating N periodic position signals each of which is equally 160°/N out of phase with each other, each of the N servo tracks corresponding to each of the N periodic position signals;   computing means for computing and generating N tracking error signals according to the servo signals read from each of the servo tracks;   memory means for storing the tracking error signals;   controller means for controlling the actuator means according to the periodic position signals and the tracking error signals stored in the memory means;   temperature detecting means for detecting the temperature of the apparatus and generating a corresponding output signal; and   means connected to the temperature detecting means for compensating the tracking error signals according to the output signal of the temperature detecting means and generating N compensated error signals, wherein the controller means controls the actuator means according to the compensated error signals..]..[.   
     
     
       3.  A magnetic disc apparatus comprising: (a) a magnetic disc having plurality of data tracks and at least two concentric reference regions each having four concentric reference tracks on which a servo signal is recorded at angularly spaced apart locations along the servo track;   (b) transducer means for reading and writing data signals from and on the data tracks and reading the servo signals from the reference tracks;   (c) actuator means for positioning the transducer means over a desired one of the tracks;   (d) means connected to the transducer means for computing and generating tracking error signals as a function of the servo signal read at any selected angular location on the reference tracks;   (e) memory means for storing the tracking error signal;   (f) position sensing means for sensing the position of the transducer means relative to the magnetic disc and outputting a corresponding position signal, wherein the position sensing means generates at least N periodic signals which are at least 90° out of phase with each other, where N is an integer equal to or greater than 2; and   (g) controller means, supplied with the output of the position sensing means, for controlling the actuator means according to the stored tracking error signal corresponding to the data track to which the transducer is to be positioned..]..[.   
     
     
       4.  The magnetic disk apparatus as defined in claim 3, further comprising.]. .Iadd.A magnetic disc apparatus, comprising: (a) a magnetic disc having plurality of data tracks and at least two concentric reference regions each having four concentric reference tracks on which a servo signal is recorded at angularly spaced apart locations along the servo track;   (b) transducer means for reading and writing data signals from and on the data tracks and reading the servo signals from the reference tracks;   (c) actuator means for positioning the transducer means over a desired one of the tracks;   (d) means connected to the transducer means for computing and generating tracking error signals as a function of the servo signal read at any selected angular location on the reference tracks;   (e) memory means for storing the tracking error signal;   (f) position sensing means for sensing the position of the transducer means relative to the magnetic disc and outputting a corresponding position signal, wherein the position sensing means generates at least N periodic signals which are at least 90° out of phase with each other, where N is an integer equal to or greater than 2;   (g) controller means, supplied with the output of the position sensing means, for controlling the actuator means according to the stored tracking error signal corresponding to the data track to which the transducer is to be positioned; and   (h) .Iaddend.temperature detecting means for detecting the temperature of the apparatus and generating a corresponding output signal, and wherein the controller means is connected to the temperature detecting means for compensating the tracking error signals according to the output signal of the temperature detecting means and generating N compensated error signals, wherein the controller means controls the actuator means according to the compensated error signals.   
     
     
       5. The magnetic disc apparatus as defined in claim 4, wherein the controller means computes gradients of the error signals with respect to the tracks at individual temperatures and stores the gradients in the memory means and, after the actual temperature of the apparatus is detected by the detecting means, the error signal for a selected track is corrected in accordance with the stored gradient of the error signal at the detected temperature to produce the compensated error signal. .[.6. A magnetic disc apparatus comprising: (a) a magnetic disc having a plurality of concentric data tracks and at least two reference regions each having at least four concentric reference tracks on which servo signals are circumferentially prerecorded;   (b) transducer means for reading and writing data signals on the data tracks and reading the servo signals from the servo tracks;   (c) actuator means for positioning the transducer means over a desired one of the tracks;   (d) position sensor means for sensing the position of the transducer means relative to the magnetic disc, and for generating N periodic position signals each of which is at least 90° out of phase with each other, wherein N is an integer equal to or larger than 2, the period of the periodic position signals corresponding to the reference tracks;   (e) computing means for computing and generating tracking error signals according to the servo signals read from each of the servo tracks;   (f) memory means for storing the tracking error signals; and   (g) controller means for controlling the actuator means according to the periodic position signals and the tracking error signals stored in the memory means..]..[.7. A magnetic disc apparatus according to claim 6, wherein the magnetic disc has an additional reference region having N additional concentric servo tracks on which servo signals are   
     
     
        circumferentially prerecorded..]..Iadd.8.  The magnetic disc apparatus as defined in claim 4, wherein at least some of the data tracks are located on the disc at a position radially between the two reference regions. 
     
     
        .Iaddend..Iadd.9.  The magnetic disc apparatus as defined in claim 4, wherein data is stored separately for each of the plural reference tracks, and there is one reference track within each of the reference regions for each one of the N periodic signals of the position sensing means. .Iaddend..Iadd.10. The magnetic disc apparatus as defined in claim 9, wherein the controller means controls the actuator means in accordance with data stored for a selected reference track corresponding to one of the N periodic signals. .Iaddend..Iadd.11. The magnetic disc apparatus as defined in claim 4, wherein the position sensing means is a multiple-phase optical sensor, and each phase of the optical sensor identifies the nominal center of one of the data tracks by an output signal which crosses a zero reference value in a right ascending manner at the position corresponding to said center. .Iaddend..Iadd.12. The magnetic disc apparatus as described in claim 4, wherein the controller means includes means for controlling the actuator means in accordance with one of the periodic signals, shifted by an amount corresponding to the product of a gradient and the distance of any selected track from a reference track. 
     
     
        .Iaddend..Iadd.13.  A magnetic disc apparatus comprising: (a) a magnetic disc having a plurality of concentric data tracks and at least two reference regions each having at least four concentric reference tracks on which servo signals are circumferentially prerecorded;   (b) transducer means for reading and writing data signals on the data tracks and reading the servo signals from the reference tracks;   (c) actuator means for positioning the transducer means over a desired one of the tracks;   (d) position sensing means for sensing the position of the transducer means relative to the magnetic disc, and for generating N periodic position signals each of which is at least 90° out of phase with each other, wherein N is an integer equal to or larger than 2, the period of the periodic position signals corresponding to the reference tracks;   (e) computing means for computing and generating tracking error signals according to the servo signals read from each of the reference tracks;   (f) memory means for storing the tracking error signals; and   (g) controller means for controlling the actuator means according to the periodic position signals and the tracking error signals stored in the memory means, wherein the controller means controls the actuator means in accordance with one of the periodic position signals, shifted by an amount corresponding to the product of a gradient and the distance of any   
     
     
        selected track from a reference track. .Iaddend..Iadd.14.  A magnetic disc apparatus comprising: a magnetic disc having a plurality of concentric data tracks and a reference region having N concentric servo tracks on which servo signals are prerecorded, wherein N is an integer larger than 2;   transducer means for reading and writing data signals on the data tracks and reading the servo signals from the servo tracks;   actuator means for positioning the transducer means over a desired one of the tracks;   position sensor means for sensing the position of the transducer means relative to the magnetic disc, and for generating N periodic position signals each of which is equally 360°/N out of phase with each other, each of the N servo tracks corresponding to each of the N periodic position signals;   computing means for computing and generating N tracking error signals according to the servo signals read from each of the servo tracks;   memory means for storing the tracking error signals;   controller means for controlling the actuator means according to the periodic position signals and the tracking error signals stored in the memory means;   temperature detecting means for detecting the temperature of the apparatus and generating a corresponding output signal; and   means connected to the temperature detecting means for compensating the tracking error signals according to the output signal of the temperature detecting means and generating N compensated error signals, wherein the controller means controls the actuator means according to the compensated error signals. .Iaddend.