Embedded servo track following system and method for writing servo tracks

A method for positioning a read/write transducer relative to a magnetic storage disc to read data stored on said disc, the method comprising the steps of:

• driving said disc to provide relative movement between said disc and said read/write transducer thereby enabling the transfer of data between said disc and said transducer;
• providing a plurality of side-by-side, closely spaced alternately arranged odd and even servo tracks recorded on said disc such that an adjacent pair of said odd and even servo tracks identifies a preselected radial position on said disc therebetween, each of said odd and even servo tracks generating a waveform having a net DC component, said DC components of said odd and even servo tracks being equal in magnitude but opposite in polarity whereby said DC components of said odd and even servo tracks cancel each other when the read/write transducer is disposed therebetween, said servo tracks being provided with a nonuniform, radial density, varying substantially continuously from track to track according to the performance of the read/write transducer common to said tracks used to read said tracks from generally more dense at the periphery of said disc where transducer performance is high to generally less dense at the interior of said disc where transducer performance is low;
• sensing the output of the read/write transducer;
• and
• positioning the read/write transducer to null the output of the transducer thus centering the same between odd and even servo tracks.

A method for writing a clock track on a magnetic storage medium comprising the steps of:

• providing a fixed read/write head;
• providing at least one moving read/write head;
• translating said magnetic storage medium relative to said fixed and said moving heads, whereby information may be written on said medium in the form of magnetic transitions and said magnetic transitions may be read with said fixed and said moving heads;
• writing a single pair of transitions with said fixed head;
• selecting a predetermined number N or transition pairs for a clock track;
• reading said single pair of transitions to create a single initial electrical pulse;
• phase-lock looping said initial electrical pulse to a number of electrical pulses approximately equal to the square root of N;
• writing an intermediate clock track with said moving head, said intermediate clock track having a number of transition pairs equal to the square root of N;
• reading said intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N;
• phase-lock looping said intermediate clock electrical pulses to a number of electrical pulses equal to N;
• and
• writing a clock track with said fixed head having N transition pairs.

A method for establishing a desired track density on a magnetic storage medium comprising the steps of:

• providing at least one moving read/write head;
• translating said magnetic storage medium relative to said read/write head, whereby information may be written on said medium in the form of magnetic transitions and said magnetic transitions may be read with said read/write head;
• providing means for positioning said read/write head at different positions on said storage medium;
• positioning said read/write head at a first limit stop in the range of travel of said means for positioning;
• writing a first reference track with said read/write head;
• choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density;
• reading said first reference track with said read/write head;
• displacing said read/write head away from said first limit stop until the amplitude of said first reference track is reduced to X% of its original amplitude;
• writing a second reference track with said read/write head;
• displacing said read/write head again in the same direction until the amplitude of said second reference track is reduced to X% of its original amplitude;
• continuing to write successive reference tracks and displacing said read/write head across said storage medium by writing a reference track and moving said read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% of its original amplitude;
• counting the number of reference tracks written;
• stopping when a second limit stop in the range of travel of said means for positioning is encountered;
• checking the track density to ensure that it is within a predetermined range of the desired track density;
• if the track density is high, erase said storage medium, lower said X% value and repeat the programming method steps;
• if the track density is low, erase said storage medium, increase said X% value and repeat the aforementioned method steps;
• and
• stopping if the track density is within a predetermined range of the desired track density.

A method for writing embedded servo data on a magnetic storage medium comprising the steps of:

• providing a first moving read/write head;
• translating said magnetic storage medium relative to said read/write head, whereby information may be written on said medium in the form of magnetic transitions and said magnetic transitions may be read with said read/write head;
• providing means for positioning said read/write head at different positions on said storage medium;
• positioning said first read/write head at a first limit stop in the range of travel of said means for positioning;
• dividing said magnetic storage medium into servo data sectors and reference data sectors;
• writing a first servo data track with said read/write head in said servo data sectors on said storage medium;
• writing a first reference track with said read/write head in said reference data sectors on said storage medium;
• choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density;
• reading said first reference track with said read/write head;
• displacing said read/write head away from said first limit stop until the amplitude of said first reference track is reduced to X% of its original amplitude;
• writing a second reference track with said read/write head in said reference data sectors;
• displacing said read/write head again in the same direction until the amplitude of said second reference track is reduced to X% of its original amplitude;
• writing a second servo track with said read/write head in said reference data sectors;
• continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth;
• keeping a measure of the number of servo data tracks written;
• stopping when a second limit stop in the range of travel of said means for positioning is encountered;
• checking the servo track density to ensure that it is within a predetermined range of the desired track density;
• if the servo track density if high, erase said storage medium, lower said X% value and repeat the aforementioned method steps;
• if the servo track density is low, erase said storage medium, raise said X% value and repeat the aforementioned method steps;
• stopping if the servo track density is within a predetermined range of the desired servo track density;
• and
• erasing the reference data sectors.

A method for writing embedded servo data on a magnetic storage medium comprising the steps of:

• providing a fixed read/write head;
• providing a first moving read/write head;
• translating said magnetic storage medium relative to said fixed and said moving heads, whereby information may be written on said medium in the form of magnetic transitions and said magnetic transitions may be read with said fixed and said moving heads;
• writing a single pair of transitions with said fixed head;
• selecting a predetermined number N of transition pairs for a clock track;
• reading said single pair of transitions to create a single initial electrical pulse;
• phase-lock looping said initial electrical pulse to a number of electrical pulses approximately equal to the square root of N;
• holding said moving head stationary and writing an intermediate clock track with said moving head, said intermediate clock track having a number of transition pairs equal to the square root of N;
• reading said intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N;
• phase-lock looping said intermediate clock electrical pulses to a number of electrical pulses equal to N;
• writing a clock track with said fixed head having N transition pairs;
• providing means for positioning said first moving read/write head at different positions on said storage medium;
• positioning said first moving read/write head at a first limit stop in the range of travel of said means for positioning;
• writing a first reference track with said first moving read/write head;
• choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density;
• reading said first reference track with said first moving read/write head;
• displacing said first moving read/write head away from said first limit stop until the amplitude of said first reference track is reduced to X% of its original amplitude;
• writing a second reference track with said first moving read/write head;
• displacing said first moving read/write head again in the same direction until the amplitude of said second reference track is reduced to X% of the original amplitude;
• continuing to write successive reference tracks and displacing said first moving read/write head across said storage medium by writing a reference track and moving said first moving read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% if its original amplitude;
• counting the number of reference tracks written;
• stopping when a second limit stop in the range of travel of said means for positioning is encountered;
• erasing said storage medium;
• checking the track density to ensure that it is written a predetermined range of the desired track density;
• if the track density is high, lower said X% value and repeat the programming method steps;
• if the track density is low, increase said X% value and repeat the aforementioned method steps;
• go to the next step of the method if the track density is within a predetermined range of the desired track density;
• positioning said first moving read/write head at a first limit stop in the range of travel of said means for positioning;
• dividing said magnetic storage medium into servo data sectors and reference data sectors;
• writing a first servo data track with said first moving read/write head in said servo data sectors on said storage medium;
• writing a first reference track with said first moving read/write head in said reference data sectors on said storage medium;
• reading said first reference track with said moving read/write head;
• displacing said first moving read/write head away from said first limit stop until the amplitude of said first reference track is reduced to X% of its original amplitude;
• writing a second reference track with said first moving read/write head in said reference data sectors;
• displacing said first moving read/write head again in the same direction until the amplitude of said second reference track is reduced to X% of its original amplitude;
• writing a second servo track with said first moving read/write head in said reference data sectors;
• continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth;
• keeping a measure of the number of servo data tracks written;
• stopping when a second limit step in the range of travel of said means for positioning is encountered;
• checking the servo track density to ensure that it is within a predetermined range of the desired track density;
• if the servo track density is high, erase said storage medium, lower said X% value and repeat the aforementioned method steps;
• if the servo track density is low, erase said storage medium, raise said X% value and repeat the aforementioned method steps;
• stopping if the servo track density is within a predetermined range of the desired servo track density;
• and
• erasing only the reference data sectors.