Head position control method and disk storage device
View Patent ↗A disk device has eccentric misalignment between a plurality of disk surfaces. In order to prevent transient phenomena due to differences in the eccentric trajectories during head switching, a head position control method performs feed forward control for a plurality of disk surfaces by application of the eccentricity correction current of respective heads, and when switching heads, predicts the velocity fluctuation or current step differential between heads from the eccentricity correction current, and thus corrects the control system to eliminate velocity fluctuation and current step differential.
1. A head position control method for driving a plurality of heads by means of a single actuator in order to at least read different disk surfaces, comprising the steps of:
calculating a servo control amount in accordance with a positional error between a target position of a selected one of the plurality of heads and a present position of said selected head;
controlling the actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
calculating, when switching from one of the plurality of heads to another of the plurality of heads, a differential velocity between eccentric trajectories of said respective switched heads before and after switching; and
setting said differential velocity as an initial velocity in said step of calculating said servo control amount.
2. The head position control method according to claim 1 , wherein said step of calculating said differential velocity comprises a step for calculating said differential velocity on the basis of a difference between an eccentricity correction current for said one of the plurality of heads and an eccentricity correction current for said another of said plurality of heads.
3. A head position control method for driving a plurality of heads by means of a single actuator in order to at least read different disk surfaces, comprising the steps of:
calculating a servo control amount in accordance with a positional error between a target position of a selected one of the plurality of heads and a present position of said selected head;
controlling the actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
calculating, when switching from one of the plurality of heads to another of the plurality of heads, a differential velocity between eccentric trajectories of said respective switched heads before and after switching; and
performing feed forward control for reducing said differential velocity.
4. The head position control method according to claim 3 , wherein said feed forward control step comprises the steps of:
generating a position trajectory and current trajectory for reducing said differential velocity, in accordance with said differential velocity;
correcting said present position by means of said position trajectory; and
adding said current trajectory to said eccentricity correction current and supplying said added result to the actuator.
5. A head position control method for driving a plurality of heads by means of a single actuator in order to at least read different disk surfaces, comprising the steps of:
calculating a servo control amount in accordance with a positional error between a target position of a selected one of the plurality of heads and a present position of said selected head;
controlling the actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
calculating, when switching from one of said plurality of heads to another of said plurality of heads, a differential between eccentricity correction currents of said respective switched heads before and after switching; and
performing feed forward control for reducing said differential.
6. The head position control method according to claim 5 , wherein said feed forward control step comprises the steps of:
generating a position trajectory and current trajectory for reducing said current differential, in accordance with said current differential;
correcting said present position by means of said position trajectory; and
adding said current trajectory to said eccentricity correction current and supplying said added result to the actuator.
7. A head position control method for driving a plurality of heads by means of a single actuator in order to at least read different disk surfaces, comprising the steps of:
calculating a servo control amount in accordance with a positional error between a target position of a selected one of the plurality of heads and a present position of said selected head;
controlling said actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
calculating, when switching from one of said plurality of heads to another of said plurality of heads, a differential between eccentricity correction currents of said respective switched heads before and after said switching, and a velocity differential between said respective switched heads; and
performing feed forward control for reducing said current differential and said velocity differential.
8. The head position control method according to claim 7 , wherein said feed forward control step comprises the steps of:
generating a first position trajectory and a first current trajectory for reducing said velocity differential, in accordance with said velocity differential;
generating a second position trajectory and a second current trajectory for reducing said current differential, in accordance with said current differential;
correcting said present position by means of said first and second position trajectories; and
adding said first and second current trajectories to said eccentricity correction current and supplying said added result to the actuator.
9. A disk storage device, comprising:
a plurality of heads for at least reading different disk surfaces;
a single actuator for driving said plurality of heads; and
a controller for performing servo control in accordance with a positional error between a target position of a selected one of said plurality of heads and a present position of said selected head, and controlling said actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount,
wherein, when switching from one of said plurality of heads to another of said plurality of heads, said controller calculates a differential velocity between eccentric trajectories of said respective switched heads before and after switching, and sets said differential velocity as an initial velocity in a calculation of said servo amount.
10. The disk storage device according to claim 9 , wherein said controller calculates said differential velocity on the basis of a difference between an eccentricity correction current for said one of said plurality of heads and an eccentricity correction current for said another of said plurality of heads.
11. A disk storage device comprising:
a plurality of heads for at least reading different disk surfaces;
a single actuator for driving said plurality of heads; and
a controller for performing servo control in accordance with a positional error between a target position of a selected one of said plurality of heads and a present position of said selected head, and controlling said actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
wherein, when switching from one of said plurality of heads to another of said plurality of heads, said controller calculates a differential velocity between eccentric trajectories of said respective switched heads before and after switching and performs feed forward control for reducing said differential velocity.
12. The disk storage device according to claim 11 , wherein said controller generates a position trajectory and current trajectory for reducing said differential velocity, in accordance with said differential velocity, corrects said present position by means of said position trajectory, adds said current trajectory to said eccentricity correction current, and supplies said added result to said actuator.
13. A disk storage device comprising:
a plurality of heads for at least reading different disk surfaces;
a single actuator for driving said plurality of heads; and
a controller for performing servo control in accordance with a positional error between a target position of a selected one of said plurality of heads and a present position of said selected head, and controlling said actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
wherein, when switching from one of said plurality of heads to another of said plurality of heads, said controller calculates a differential between eccentricity correction currents of said respective switched heads before and after switching and performs feed forward control for reducing said differential.
14. The disk storage device according to claim 13 , wherein said controller generates a position trajectory and a current trajectory for reducing said current differential, corrects said present position by means of said position trajectory, adds said current trajectory to said eccentricity correction current, and supplies said added result to said actuator.
15. A disk storage device comprising:
a plurality of heads for at least reading different disk surfaces;
a single actuator for driving said plurality of heads; and
a controller for performing servo control in accordance with a positional error between a target position of a selected one of said plurality of heads and a present position of said selected head, and controlling said actuator by adding an eccentricity correction current corresponding to said selected head to said servo control amount;
wherein, when switching from one of said plurality of heads to another of said plurality of heads, said controller calculates a differential between eccentricity correction currents of said respective switched heads before and after switching, and a velocity differential between said heads, and performs feed forward control for reducing said current differential and said velocity differential.
16. The disk storage device according to claim 15 , wherein said controller generates a first position trajectory and a first current trajectory for reducing said velocity differential in accordance with said velocity differential, generates a second position trajectory and a second current trajectory for reducing said current differential in accordance with said current differential, corrects said present position by means of said first and second position trajectories, and adds said first and second current trajectories to said eccentricity correction current and supplies added result to said actuator.