Controlling seeks using non-linear switching curves
Controlling seeking of a transducer includes accelerating the transducer to a seek velocity, generating a linearized switching curve defining a position and velocity of the transducer at which deceleration should begin, and controlling the velocity of the transducer in response to the current position and seek velocity of the transducer relative to the linearized switching curve. The linearized switching curve has a slope and an offset that are determined in response to the seek velocity and a current position of the transducer relative to a nonlinear switching curve.
1. A method of controlling seeking of a transducer, comprising:
accelerating the transducer to a seek velocity;
generating a linearized switching curve defining a position and velocity of the transducer at which deceleration should begin using a nonlinear switching curve; and
controlling the velocity of the transducer in response to the current position and seek velocity of the transducer relative to the linearized switching curve.
2. The method of claim 1 , wherein the linearized switching curve has a slope and an offset that are determined relative to a nonlinear switching curve in response to the seek velocity and a current position of the transducer.
3. The method of claim 2 , wherein the linearized switching curve is generated to have a slope that increases as the transducer approaches a destination track.
4. The method of claim 2 , wherein the slope of the linearized switching curve is selected from a lookup table based on the seek velocity and based on the current position of the transducer.
5. The method of claim 2 , wherein the nonlinear switching curve corresponds to a saturated current deceleration curve.
6. The method of claim 2 , wherein the linearized switching curve is generated to have a slope that corresponds to the slope of the nonlinear switching curve at the current position of the transducer.
7. The method of claim 2 , wherein the offset of the linearized switching curve is determined in response to the slope of the linearized switching curve and a value of the nonlinear switching curve at the seek velocity.
8. The method of claim 2 , wherein the nonlinear switching curve has a shape given by the equation:
V NL =CX n
and wherein the linearized switching curve is generated to have a shape given by the equation:
V LIN =MX+B
where X represents distance from a target track, C and n are constants that define the shape of the nonlinear switching curve, M is the slope of the linearized switching curve and B is the offset of the linearized switching curve.
9. The method of claim 8 , wherein the linearized switching curve is generated to have a slope given by the equation:
M=nCX 0 n-1
wherein X 0 represents the current position of the transducer.
10. The method of claim 9 , wherein the linearized switching curve is generated to have an offset given by the equation:
B=V 0 −M·V 0 1/n C −1/n
wherein V 0 represents the seek velocity.
11. The method of claim 10 , wherein the estimated time before a current trajectory of the transducers will cross the linearized switching curve is given by the equation:
Est_spokes
_until
_crossing
=
MX
0
-
V
0
+
B
MV
0
+
A
0
wherein A 0 represents a current acceleration of the transducer.
12. A method of controlling seeking of a transducer that is adjacent to a rotatable disk in a disk drive, comprising:
accelerating the transducer radially across the rotatable disk from an initial track toward a destination track by applying an acceleration current to an actuator associated with the transducer; and
changing the acceleration of the transducer relative to a linearized switching curve generated in response to a nonlinear switching curve and a current velocity and current position of the transducer.
13. The method of claim 12 , further comprising estimating a time before a current trajectory of the transducers will cross a linearized switching curve having a slope and an offset that are determined relative to a nonlinear switching curve in response to a current velocity and a current position of the transducer.
14. The method of claim 13 , further comprising reducing the acceleration current as the transducer approaches the linearized switching curve.
15. The method of claim 13 , further comprising applying a deceleration current to the actuator when the transducer reaches the linearized switching curve.
16. An apparatus, comprising:
an actuator configured to move a load from an initial location to a target location; and
a servo controller that controls the velocity of the load relative to a linearized switching curve defining a position and velocity of the load at which deceleration should begin, wherein the linearized switching curve is generated using a nonlinear switching curve.
17. The apparatus of claim 16 , wherein the servo controller accelerates the load to a seek velocity in response to a seek command, generates the linearized switching curve, wherein the linearized switching curve has a slope and an offset that are determined in response to the seek velocity and a current position of the load relative to a nonlinear switching curve, and controls the velocity of the load in response to the current position and seek velocity of the load relative to the linearized switching curve.
18. The apparatus of claim 17 , wherein the servo controller selects the slope of the linearized switching curve from a lookup table based on the seek velocity and based on the current position of the load.
19. The apparatus of claim 17 , wherein the nonlinear switching curve corresponds to a saturated current deceleration curve.
20. The apparatus of claim 17 , wherein the slope of the linearized switching curve corresponds to the slope of the nonlinear switching curve at the current position of the load.
21. The apparatus of claim 16 , wherein the servo controller determines the offset of the linearized switching curve in response to the slope of the linearized switching curve and a value of the nonlinear switching curve at the seek velocity.
22. The apparatus of claim 16 , wherein the nonlinear switching curve has a shape given by the equation:
V NL =CX n
wherein the linearized switching curve has a shape given by the equation:
V LIN =MX+B
wherein the slope of the linearized switching curve is given by the equation:
M=nCX 0 n-1
wherein the offset of the linearized switching curve is given by the equation:
B
=
V
0
-
M
·
V
0
1
n
C
-
1
n
where X represents distance from the target location, C and n are constants that define the shape of the nonlinear switching curve, M is the slope of the linearized switching curve, B is the offset of the linearized switching curve, X 0 represents the current position of the load, and V 0 represents the seek velocity.
23. The apparatus of claim 22 , wherein the estimated time before a current trajectory of the loads will cross the linearized switching curve is given by the equation:
Est_spokes
_until
_crossing
=
MX
0
-
V
0
+
B
MV
0
+
A
0
wherein A 0 represents a current acceleration of the load.