Controller-characteristic changing apparatus, storage device, controller-characteristic changing method, and computer product

1. A controller-characteristic changing apparatus that changes a controller characteristic of a controller that controls positioning of a head that performs at least one of data writing and data reading with respect to a storage medium, the controller-characteristic changing apparatus comprising:

an vibration detector that detects whether the head is subjected to external vibration due to an external factor;

a first changing unit that, when the vibration detector detects the external vibration while the controller is controlling the positioning of the head according to a positioning-oriented controller characteristic that takes an accuracy of positioning the head into account, changes the positioning-oriented controller characteristic to a vibration-reducing controller characteristic that improves a reduction effect of vibration of a first frequency band; and

a second changing unit that, when the vibration detector detects absence of the external vibration while the controller is controlling the positioning of the head according to the vibration-reducing controller characteristic, changes the vibration-reducing controller characteristic to the positioning-oriented controller characteristic, wherein

a reduction rate of the vibration of the head for the vibration-reducing controller characteristic is higher than a reduction rate of the vibration of the head for the positioning-oriented controller characteristic in the first frequency band, and

the reduction rate of the vibration of the head for vibration-reducing controller characteristic is lower than the reduction rate of the vibration of the head for positioning-oriented controller characteristic in a second frequency band that is higher than the first frequency band.

2. The controller-characteristic changing apparatus according to claim 1 , wherein the vibration detector acquires a position signal indicating a position of the head in the storage medium, and detects whether the head is subjected to the external vibration based on a magnitude of acquired position signal.

3. The controller-characteristic changing apparatus according to claim 1 , wherein the vibration detector acquires a position signal indicating a position of the head in the storage medium and filters acquired position signal, and detects whether the head is subjected to the external vibration based on a magnitude of filtered acquired position signal.

4. The controller-characteristic changing apparatus according to claim 1 , wherein the vibration detector detects whether the head is subjected to the external vibration based on whether a detection signal from a shock sensor that is set to a predetermined sensitivity is acquired.

5. The controller-characteristic changing apparatus according to claim 1 , wherein the vibration detector acquires number of write failures of the head in writing on the storage medium, and detects whether the head is subjected to the external vibration based acquired number of write failures.

6. The controller-characteristic changing apparatus according to claim 5 , wherein in at least one of a case that a detection signal from a shock sensor that is set to a predetermined sensitivity is acquired and a case that a position signal indicating a position of the head in the storage medium is acquired and a value of the acquired position signal exceeds a predetermined threshold, the vibration detector determines that the head has failed to write on the storage medium, and acquires the number of write failures of the head.

7. The controller-characteristic changing apparatus according to claim 1 , wherein the vibration detector acquires an amount of change in an eccentricity correction value to correct eccentricity of the storage medium, and detects whether the head is subjected to the external vibration based on the acquired amount of the change.

8. A storage device including a controller that controls positioning of a head that performs at least one of data writing and data reading with respect to a storage medium, based on a controller characteristic, the storage device comprising:

an vibration detector that detects whether the head is subjected to external vibration due to an external factor;

a first changing unit that, when the vibration detector detects the external vibration while the controller is controlling the positioning of the head according to a positioning-oriented controller characteristic that takes an accuracy of positioning the head into account, changes the positioning-oriented controller characteristic to a vibration-reducing controller characteristic that improves a reduction effect of vibration of a first frequency band; and

a second changing unit that, when the vibration detector detects absence of the external vibration while the controller is controlling the positioning of the head according to the vibration-reducing controller characteristic, changes the vibration-reducing controller characteristic to the positioning-oriented controller characteristic, wherein

a reduction rate of the vibration of the head for the vibration-reducing controller characteristic is higher than a reduction rate of the vibration of the head for the positioning-oriented controller characteristic in the first frequency band, and

the reduction rate of the vibration of the head for vibration-reducing controller characteristic is lower than the reduction rate of the vibration of the head for positioning-oriented controller characteristic in a second frequency band that is higher than the first frequency band.

9. The storage device according to claim 8 , wherein the vibration detector acquires a position signal indicating a position of the head in the storage medium, and detects whether the head is subjected to the external vibration based on a magnitude of acquired position signal.

10. The storage device according to claim 8 , wherein the vibration detector acquires a position signal indicating a position of the head in the storage medium and filters acquired position signal, and detects whether the head is subjected to the external vibration based on a magnitude of filtered acquired position signal.

11. The storage device according to claim 8 , wherein the vibration detector detects whether the head is subjected to the external vibration based on whether a detection signal from a shock sensor that is set to a predetermined sensitivity is acquired.

12. The storage device according to claim 8 , wherein the vibration detector acquires number of write failures of the head in writing on the storage medium, and detects whether the head is subjected to the external vibration based acquired number of write failures.

13. The storage device according to claim 12 , wherein in at least one of a case that a detection signal from a shock sensor that is set to a predetermined sensitivity is acquired and a case that a position signal indicating a position of the head in the storage medium is acquired and a value of the acquired position signal exceeds a predetermined threshold, the vibration detector determines that the head has failed to write on the storage medium, and acquires the number of write failures of the head.

14. The storage device according to claim 8 , wherein the vibration detector acquires an amount of change in an eccentricity correction value to correct eccentricity of the storage medium, and detects whether the head is subjected to the external vibration based on the acquired amount of the change.

15. A method of changing a controller characteristic of a controller that controls positioning of a head that performs at least one of data writing and data reading with respect to a storage medium, the method comprising:

detecting whether the head is subjected to external vibration due to an external factor;

changing, when the vibration detector detects the external vibration while the controller is controlling the positioning of the head according to a positioning-oriented controller characteristic that takes an accuracy of positioning the head into account, the positioning-oriented controller characteristic to a vibration-reducing controller characteristic that improves a reduction effect of vibration of a first frequency band; and

changing, when the vibration detector detects absence of the external vibration while the controller is controlling the positioning of the head according to the vibration-reducing controller characteristic, the vibration-reducing controller characteristic to the positioning-oriented controller characteristic, wherein

a reduction rate of the vibration of the head for the vibration-reducing controller characteristic is higher than a reduction rate of the vibration of the head for the positioning-oriented controller characteristic in the first frequency band, and

the reduction rate of the vibration of the head for vibration-reducing controller characteristic is lower than the reduction rate of the vibration of the head for positioning-oriented controller characteristic in a second frequency band that is higher than the first frequency band.

16. A computer-readable recording medium that stores therein a computer program that causes a computer execute a method of changing a controller characteristic of a controller that controls positioning of a head that performs at least one of data writing and data reading with respect to a storage medium, the computer program causes the computer to execute:

detecting whether the head is subjected to external vibration due to an external factor;

changing, when the vibration detector detects the external vibration while the controller is controlling the positioning of the head according to a positioning-oriented controller characteristic that takes an accuracy of positioning the head into account, the positioning-oriented controller characteristic to a vibration-reducing controller characteristic that improves a reduction effect of vibration of a first frequency band; and

changing, when the vibration detector detects absence of the external vibration while the controller is controlling the positioning of the head according to the vibration-reducing controller characteristic, the vibration-reducing controller characteristic to the positioning-oriented controller characteristic, wherein

a reduction rate of the vibration of the head for the vibration-reducing controller characteristic is higher than a reduction rate of the vibration of the head for the positioning-oriented controller characteristic in the first frequency band, and

the reduction rate of the vibration of the head for vibration-reducing controller characteristic is lower than the reduction rate of the vibration of the head for positioning-oriented controller characteristic in a second frequency band that is higher than the first frequency band.