Method and apparatus for the enhancement of embedded runout correction in a disk drive

A method of generating and using compensation values for a disk drive, comprising:

• providing a data storage disk in the disk drive, the disk having at least a first track addressable by a first head, said at least a first track having an ideal shape and an actual written shape, and having a plurality of hard sectors;
• determining a position error of said actual written shape of said at least a first track at each of said plurality of hard sectors associated with said at least a first track;
• measuring a time domain impulse response of a servo control system associated with said first transducer head;
• transforming said time domain impulse response to an error transfer function;
• taking the reciprocal of said error transfer function;
• transforming said reciprocal error transfer function to an inverse impulse response for said servo control system associated with said first transducer head;
• convolving said inverse impulse response and said position error of said actual written shape of said track at each of said plurality of hard sectors associated with said track to obtain a repeatable runout correction value for each of said plurality of hard sectors;
• and
• writing said repeatable runout correction values to said plurality of hard sectors, wherein said embedded runout correction values cause said head to follow said ideal shape of said track.

A hard disk drive having embedded runout correction values determined from a numerical model of an impulse response of each of said hard disk drive's heads, comprising:

• a base;
• a disk comprising a plurality of data tracks arranged concentrically about said spindle, wherein each of said data tracks is segmented into a plurality of data sectors by servo sectors, wherein said disks may be rotated at a constant velocity with respect to said base, and wherein each of said tracks has an ideal shape and an actual written shape;
• a transducer head for reading information from said data tracks and for writing information to said data tracks, wherein said transducer head is movable in a radial direction with respect to said disk to address a selected one of said plurality of data tracks;
• a voice coil motor, interconnected to said transducer head, for moving said transducer head with respect to said data tracks;
• a channel for receiving signals, including position error signals and embedded correction values, derived from said disk by said transducer head;
• a controller, interconnected to said voice coil motor, for controlling a position of said transducer head with respect to said data tracks, wherein each of said servo sectors in at least a first track contains a plurality of embedded runout correction values, wherein said embedded runout correction values are calculated from the convolution of a numerical model of an impulse response describing the motion of said transducer head in response to an input with a position error of said at least a first track due to repeatable runout, wherein said numerical model is obtained by introducing an impulse function to said channel and measuring a response to obtain an impulse response, transforming said impulse response to a frequency domain response, taking the reciprocal of said frequency domain response, and inverse transforming said reciprocal frequency domain response.