Disk apparatus and track following control method

A disk apparatus, comprising:

• a head for moving to an arbitrary track position of a disk medium;
• a positional signal detection unit for detecting a positional signal according to the dislocation amount of said head from a predetermined reference position of the track on the medium;
• a feedback control unit for computing a control signal for moving said head from said positional signal so that said dislocation amount is controlled to zero;
• a drive unit for driving said head based on said control signal;
• and
• a learning control unit for generating and storing an unknown function for one disk rotation that includes a periodic disturbance in memory which is comprised of N number of memory cells by a learning algorithm as an approximate function which is approximated by the height allocated to each time block when the time required for one rotation of said disk medium is divided by N;
• wherein said learning control unit
• samples a signal which follows said positional signal according to said learning algorithm at a sampling period which is less than the time obtained by dividing the time required for one rotation of said medium by N,
• updates said one or more memory cells corresponding to said sampling time synchronizing with said sampling period according to said signal value,
• reads the values of two memory cells located at the cell positions corresponding to said output time at an output period which is less than the time obtained by dividing the time required for one rotation of said medium by N, and
• interpolates the values of said both memory cells based on said output time to generate a periodic disturbance compensation signal.