Wear reduction of a disc surface using an adaptive dither process
View Patent ↗Method and apparatus for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process. The disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use. The method includes determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc. A dither current is subsequently applied to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.
1. A method for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process, wherein the disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use, the method comprising:
determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc; and
subsequently applying a dither current to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.
2. The method of claim 1 , wherein the actuator assembly includes a data transducing head and the rotatable disc includes a landing zone and wherein the subsequently applying step comprises applying the dither current to the actuator assembly while the head is in contact with the landing zone.
3. The method of claim 2 in which the head includes padded sliders.
4. The method of claim 2 in which the landing zone includes a textured surface.
5. The method of claim 1 , wherein the subsequently applying step takes place while the disc is decelerated to rest.
6. The method of claim 1 , wherein the subsequently applying step takes place while the disc is accelerated from rest to a nominal operational speed.
7. The method of claim 1 , wherein the actuator assembly includes a contact arm that engages the latch during the subsequently applying step.
8. The method of claim 1 , wherein the subsequently applying step further comprises determining a threshold current as a selected percentage of the open latch current and wherein the maximum amplitude of the dither current is selected to be less than the threshold current.
9. The method of claim 1 , wherein the dither current follows a saw tooth profile.
10. A disc drive data storage device comprising:
a rotatable disc having a circumferential landing zone and a data storage portion;
an actuator assembly comprising a data transducing head and an actuator coil;
a latch configured to capture and retain the actuator assembly in a parked position when the head is moved to the landing zone, wherein application of an open latch current to the actuator coil causes the latch to toggle to an open position and permit movement of the head away from the landing zone and to a position adjacent the data storage portion; and
a servo control circuit configured to determine the open latch current and to apply a dither current to the actuator coil to induce a reciprocating lateral displacement of the actuator assembly, wherein a maximum amplitude of the dither current is selected to be less than the amplitude of the open latch current.
11. The apparatus of claim 10 , wherein the latch comprises a forward arm and a trailing arm.
12. The apparatus of claim 11 , wherein the disc drive further comprises a magnet assembly that produces a magnetic field and wherein the latch comprises ferromagnetic members respectively supported by the forward and trailing arms and configured for immersion into the magnetic field.
13. The apparatus of claim 10 , wherein the actuator assembly includes a contact arm that engages the latch during the application of the dither current to the actuator coil.
14. The apparatus of claim 10 , wherein the landing zone is textured.
15. A disc drive storage device comprising:
a rotatable disc comprising a landing zone and a data storage portion;
an actuator assembly comprising a data transducing head and an actuator coil;
a latch configured to capture the actuator assembly in a parked position when the head is in proximity with the landing zone and to toggle to an open position to permit movement of the head to a position adjacent the data storage portion when an open latch current is applied to the actuator coil; and
first means for determining the open latch current and for inducing a reciprocating lateral displacement of the actuator assembly while the actuator assembly is in the parked position by applying a dither current to the actuator coil having a maximum magnitude less than a magnitude of the open latch current.
16. The disc drive data storage device of claim 15 , wherein the first means comprises a servo circuit configured to position the head with respect to the disc.
17. The disc drive data storage device of claim 16 , wherein the servo circuit comprises a programmable processor with associated programs to determine the open latch current and induce the reciprocating lateral displacement.