Servo detection control system, servo detection control method and hard disk drive

1. A servo detection control system comprising:

a head change learning means including:

a means for measuring a servo sector interval, which occurs at the time of head change;

a means for calculating a head-change time difference from a value measured by the servo sector interval measuring means; and

a means for storing a result of calculation by the calculating means;

a means for compensating a start timing of servo detection after head change using a stored value of the storing means;

wherein the head change learning means further comprises a means for measuring the amount of head skew in a disk radius direction using a writing signal in a servo sector after the head change;

a means for storing the amount of head skew; and

a means for controlling feed-forward positioning of the head using the amount of head skew.

2. A servo detection control system according to claim 1 , wherein:

the means for storing a result of calculation is the same means as the means for storing the amount of head skew.

3. A servo detection control system comprising:

a head change learning means including:

a means for measuring a servo sector interval, which occurs at the time of head change;

a means for calculating a head-change time difference from a value measured by the servo sector interval measuring means; and

a means for storing a result of calculation by the calculating means; and

a means for compensating start timing of servo detection after head change using a stored value of the storing means;

wherein the head change learning means further comprises a means for measuring the amount of head skew in a disk radius direction using a writing signal in a servo sector after the head change; and

wherein the head change learning means further comprises a means for measuring the amount of servo sector skew using a servo sector address after the head change.

4. A servo detection control system according to claim 3 , further cormprising:

a means for storing the amount of servo sector skew; and

a means for compensating and controlling a servo sector address using the amount of servo sector skew.

5. A servo detection control system according to claim 4 , wherein:

the means for storing a result of calculation is the same means as the means for storing the amount of servo sector skew.

6. A servo detection control method comprising:

measuring a servo sector interval, which occurs at the time of head change among a plurality of heads;

calculating a head-change time difference form the measured value; and

compensating a head-change time difference from the measured value;

compensating a start timing of servo detection after head change using the result of calculation;

measuring an amount of head skew in a disk radius direction using a writing signal in a servo sector after the head change; and

controlling feed-forward positioning of a head using the amount of head skew and the time difference.

7. A servo detection control method comprising:

measuring a servo sector interval, which occurs at the time of head change among a plurality of heads;

calculating head-change time difference from the measured value;

measuring the amount of servo sector skew using a servo sector address after the head change; and

compensating and controlling the servo sector address using the amount of servo sector skew and the time difference.

8. A hard disk drive comprising:

a rotary storage medium storing user data and a servo signal;

a head reading the user data and the servo signal, which have been written by the medium;

an actuator driving the head;

a controller learning driving of the actuator, said controller including:

a circuit measuring a servo sector interval, which occurs in a change of the head;

a calculator which calculates a head-change time difference from a value measured by the interval measuring circuit; and

a memory for storing a result of calculation of the calculator;

a circuit compensating start timing of servo detection after changing the head using a stored value of the memory;

a sensor detecting a shock from outside; and

a circuit for judging whether or not a result of learning by the controller is adopted, using an output of the sensor.

9. A hard disk drive according to claim 8 , wherein:

the controller further comprises a circuit measuring the amount of head skew in a radius direction of the medium using a writing signal in a servo sector after changing the head.

10. A hard disk drive according to claim 8 , further comprising:

a memory storing the amount of head skew; and

a second controller positioning of feed-forward of the head using the amount of head skew.

11. A hard disk drive according to claim 10 , wherein:

the memory storing a result of calculation is the same memory as the memory storing the amount of head skew.

12. A hard disk drive according to claim 8 , wherein:

the controller further comprises a circuit measuring the amount of servo sector skew using a servo sector address after changing the head.

13. A hard disk drive according to claim 12 , further comprising:

a memory storing the amount of servo sector skew; and

a second controller compensating and controlling a servo sector address using the amount of servo sector skew.

14. A hard disk drive according to claim 13 , wherein:

the memory storing a result of calculation is the same memory as the memory storing the amount of servo sector skew.

15. A hard disk drive according to claim 8 , wherein:

a continuous search mode is applied during learning operation of the controller.

16. A hard disk drive according to claim 8 , wherein:

a continuous search mode is applied during compensation and control operation of the circuit compensating start timing.