Method, apparatus, and storage medium for controlling track seek servo in disk drive, and disk drive using same

Abstract

Provided are a method, apparatus, and storage medium for controlling a track seek servo in a disk drive. Thus, a transducer is moved to a target track using a transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory in which an acceleration duration is symmetrical to a deceleration duration in a track seek mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an HDD according to an embodiment of the present invention;

FIG. 2 is a block diagram of an electrical system controlling an HDD according to an embodiment of the present invention;

FIG. 3 is a block diagram of a servo control system of an HDD according to an embodiment of the present invention;

FIG. 4 is a diagram illustrating a PTOS velocity trajectory related to the present invention;

FIG. 5 is a diagram illustrating a PTOS symmetrical velocity trajectory for generating a new velocity trajectory according to an embodiment of the present invention;

FIG. 6 is a diagram showing the PTOS velocity trajectory, the PTOS symmetrical velocity trajectory, and the new velocity trajectory for explaining a method of generating the new velocity trajectory according to an embodiment of the present invention; and

FIG. 7 is a diagram showing the new velocity trajectory according to an embodiment of the present invention.

Claims

1. A method of controlling a track seek servo in a Hard Disk Drive (HDD), comprising: generating a transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory having symmetrical acceleration and deceleration durations during a track seek mode; and,applying the transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory to control the movement of a read/write head from a current track to a target track.

2. The method of claim 1, wherein the transformed PTOS velocity trajectory is characterized by a smoothed velocity curve including a transition point between the acceleration duration and the deceleration duration.

3. The method of claim 2, wherein the smoothed velocity curve is generated using a sine function.

4. The method of claim 1, wherein the transformed PTOS velocity trajectory V_profile is generated by a controller executing code segments to implement the equations: (a) V_profile=symmetrical velocity trajectory of PTOS for intervals where Vcurr<Vth and sk_curr<sk_len/2;(b) V_profile=Vth+V sin for an interval where Vcurr≧Vth; and(c) V_profile=velocity trajectory of PTOS for intervals where Vcurr<Vth and ttg>sk_len/2,where Vcurr denotes a current seek velocity, Vth denotes a threshold velocity for determining a period during which the velocity trajectory is transformed to a smoothed velocity curve, sk_len denotes the total seek distance, sk_curr denotes a current seek point, and V sin denotes a velocity of a sine function.

5. The method of claim 4, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) have a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS velocity trajectory V_ptos subjected to transformation is generated by operation of the controller executing the code segments to implement the equation: V—ptos=α*{β*log(1−ttg/β)+ttg}, where, α=R*Ja/Kt2, β=−I max*R/Kt, and where R denotes resistance of the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the VCM, and ttg denotes a seek distance.

6. The method of claim 4, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) having a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS symmetrical velocity trajectory V_ptos(mir) is generated by operation of the controller executing the code segment to implement the equation: V—ptos(mir)=α*{β*log(1−tta/β)+tta}where, α=R*Ja/Kt2, β=−I max*R/Kt, R denotes resistance for the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the voice coil motor (VCM), and tta denotes a seek distance.

7. The method of claim 4, wherein V sin=V max*sin(n*180/Nsample), where Nsample denotes a sine function interval between 0 and 180°, V max=A*(Vpeak−Vth), A denotes a constant having a value 0<A<1, and Vpeak denotes a peak velocity value.

8. The method of claim 7, wherein the value Nsample is determined in proportion to the seek distance.

9. An apparatus for controlling a track seek servo in a Hard Disk Drive (HDD), comprising: a seek trajectory generator adapted to generate a transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory V_profile having symmetrical acceleration and deceleration durations in a track seek mode, and further adapted to calculate a designated position value and velocity value using the transformed PTOS velocity trajectory;a state estimator adapted to determine a real position value and a real velocity value for a read/write head moving over the surface of a disk in the HDD;a first subtracter adapted to output a value obtained by subtracting the real position value from the designed position value;a position control gain compensator adapted to generate a position compensation value by multiplying the output value of the first subtracter by a predetermined position gain;a second subtracter adapted to output a value obtained by subtracting the real velocity value from a value obtained by adding the position compensation value to the designed velocity value;a velocity control gain compensator adapted to generate a velocity compensation value by multiplying the output value of the second subtracter by a predetermined velocity gain; andan actuator adapted to vary drive current supplied to a voice coil in the HDD in accordance with the velocity compensation value.

10. The apparatus of claim 9, wherein a velocity trajectory is transformed to a smoothed velocity curve over a defined period including a transition point between the acceleration duration and the deceleration duration.

11. The apparatus of claim 10, wherein the velocity trajectory is generated using a sine function.

12. The method of claim 10, wherein the transformed PTOS velocity trajectory V_profile is generated by a controller executing code segments to implement the equations: (a) V_profile=symmetrical velocity trajectory of PTOS for intervals where Vcurr<Vth and sk_curr<sk_len/2;(b) V_profile=Vth+V sin for an interval where Vcurr≧Vth; and(c) V_profile=velocity trajectory of PTOS for intervals where Vcurr<Vth and ttg>sk_len/2,where Vcurr denotes a current seek velocity, Vth denotes a threshold velocity for determining a period during which the velocity trajectory is transformed to a smoothed velocity curve, sk_len denotes the total seek distance, sk_curr denotes a current seek point, and V sin denotes a velocity of a sine function.

13. The method of claim 12, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) have a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS velocity trajectory V_ptos subjected to transformation is generated by operation of the controller executing the code segments to implement the equation: V—ptos=α*{β*log(1−ttg/β)+ttg}, where, α=R*Ja/Kt2, =−I max*R/Kt, and where R denotes resistance of the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the VCM, and ttg denotes a seek distance.

14. The method of claim 12, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) having a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS symmetrical velocity trajectory V_ptos(mir) is generated by operation of the controller executing the code segment to implement the equation: V—ptos(mir)=α*{β*log(1−tta/β)+tta}where, α=R*Ja/Kt2, β=−I max*R/Kt, R denotes resistance for the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the voice coil motor (VCM), and tta denotes a seek distance.

15. The method of claim 12, wherein V sin=V max*sin(n*180/Nsample), where Nsample denotes a sine function interval between 0 and 180°, V max=A*(Vpeak−Vth), A denotes a constant having a value 0<A<1, and Vpeak denotes a peak velocity value.

16. The method of claim 15, wherein the value Nsample is determined in proportion to the seek distance.

17. A disk drive comprising: a disk adapted to store data;a spindle motor rotating the disk;a read/write head adapted to read data from and/or write data to the disk;an actuator adapted to move the transducer over the surface of the disk; anda controller adapted to control movement of the read/write head from a current track to a target track in relation to a transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory having symmetrical acceleration and deceleration durations in a track seek mode.

18. The disk drive of claim 17, wherein a velocity trajectory is transformed to a smoothed velocity curve over a defined period including a transition point between the acceleration duration and the deceleration duration.

19. The apparatus of claim 17, wherein the velocity trajectory is generated using a sine function.

20. The method of claim 17, wherein the transformed PTOS velocity trajectory V_profile is generated by a controller executing code segments to implement the equations: (a) V_profile=symmetrical velocity trajectory of PTOS for intervals where Vcurr<Vth and sk_curr<sk_len/2;(b) V_profile=Vth+V sin for an interval where Vcurr≧Vth; and(c) V_profile=velocity trajectory of PTOS for intervals where Vcurr<Vth and ttg>sk_len/2,where Vcurr denotes a current seek velocity, Vth denotes a threshold velocity for determining a period during which the velocity trajectory is transformed to a smoothed velocity curve, sk_len denotes the total seek distance, sk_curr denotes a current seek point, and V sin denotes a velocity of a sine function.

21. The method of claim 20, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) have a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS velocity trajectory V_ptos subjected to transformation is generated by operation of the controller executing the code segments to implement the equation: V—ptos=α*{β*log(1−ttg/β)+ttg}, where, α=R*Ja/Kt2, β=−I max*R/Kt, and where R denotes resistance of the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the VCM, and ttg denotes a seek distance.

22. The method of claim 20, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) having a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS symmetrical velocity trajectory V_ptos(mir) is generated by operation of the controller executing the code segment to implement the equation: V—ptos(mir)=α*{β*log(1−tta/β)+tta}where, α=R*Ja/Kt2, β=−I max*R/Kt, R denotes resistance for the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the voice coil motor (VCM), and tta denotes a seek distance.

23. The method of claim 20, wherein V sin=V max*sin(n*180/Nsample), where Nsample denotes a sine function interval between 0 and 180°, V max=A*(Vpeak−Vth), A denotes a constant having a value 0<A<1, and Vpeak denotes a peak velocity value.

24. Recording medium storing code segments executable on a controller to implement a method of controlling a track seek servo in a Hard Disk Drive (HDD), the method comprising: generating a transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory having symmetrical acceleration and deceleration durations during a track seek mode; and,applying the transformed Proximate-Time Optimal Servo (PTOS) velocity trajectory to control the movement of a read/write head from a current track to a target track.

25. The method of claim 24, wherein the transformed PTOS velocity trajectory is characterized by a smoothed velocity curve including a transition point between the acceleration duration and the deceleration duration.

26. The method of claim 25, wherein the smoothed velocity curve is generated using a sine function.

27. The method of claim 24, wherein the transformed PTOS velocity trajectory V_profile is generated by a controller executing code segments to implement the equations: (a) V_profile=symmetrical velocity trajectory of PTOS for intervals where Vcurr<Vth and sk_curr<sk_len/2;(b) V_profile=Vth+V sin for an interval where Vcurr≧Vth; and(c) V_profile=velocity trajectory of PTOS for intervals where Vcurr<Vth and ttg>sk_len/2,where Vcurr denotes a current seek velocity, Vth denotes a threshold velocity for determining a period during which the velocity trajectory is transformed to a smoothed velocity curve, sk_len denotes the total seek distance, sk_curr denotes a current seek point, and V sin denotes a velocity of a sine function.

28. The method of claim 27, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) have a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS velocity trajectory V_ptos subjected to transformation is generated by operation of the controller executing the code segments to implement the equation: V—ptos=α*{β*log(1−ttg/β)+ttg}, where, α=R*Ja/Kt2, β=−I max*R/Kt, and where R denotes resistance of the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the VCM, and ttg denotes a seek distance.

29. The method of claim 27, wherein the HDD comprises a voice coil associated with a voice coil motor (VCM) having a torque constant and adapted to move an actuator on which the read/write head is mounted; and wherein a PTOS symmetrical velocity trajectory V_ptos(mir) is generated by operation of the controller executing the code segment to implement the equation: V—ptos(mir)=α*{β*log(1−tta/β)+tta}where, α=R*Ja/Kt2, β=−I max*R/Kt, R denotes resistance for the voice coil, Ja denotes an inertia value for the actuator, Kt denotes the torque constant, I max denotes a maximum current value applied to the voice coil motor (VCM), and tta denotes a seek distance.

30. The method of claim 27, wherein V sin=V max*sin(n*180/Nsample), where Nsample denotes a sine function interval between 0 and 180°, V max=A*(Vpeak−Vth), A denotes a constant having a value 0<A<1, and Vpeak denotes a peak velocity value.