Disk drive optimizing spindle motor torque by adjusting leading phase angle during spin-up
View Patent ↗A disk drive is disclosed comprising a head actuated over a disk, and a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings. During a spin-up operation a sinusoidal driving voltage is applied to each winding of the spindle motor. A back electromotive force (BEMF) voltage generated by at least one of the windings is measured, and a rotation speed of the spindle motor is measured. The sinusoidal driving voltage is adjusted in order to optimize a lead angle relative to the rotation speed, wherein the lead angle represents a degree the sinusoidal driving voltage leads the BEMF voltage.
1. A disk drive comprising:
a disk;
a head actuated over the disk;
a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings; and
control circuitry operable to spin-up the disk by:
applying a sinusoidal driving voltage to each winding of the spindle motor;
measuring a back electromotive force (BEMF) voltage generated by at least one of the windings;
measuring a rotation speed of the spindle motor; and
adjusting the sinusoidal driving voltage in order to optimize a lead angle relative to the rotation speed and a target maximum current applied to at least one of the windings, wherein the lead angle represents a degree the sinusoidal driving voltage leads the BEMF voltage,
wherein the control circuitry is operable to adjust the sinusoidal driving voltage so that the lead angle is approximately equal to:
arctan
(
ω
e
L
w
×
I
max
K
e
ω
+
R
w
×
I
max
)
where:
ω represents the rotation speed of the spindle motor;
ω e represents an electrical rotation speed of the spindle motor;
I max represents the maximum current;
K e represents a voltage constant of the spindle motor;
L w represents an inductance of at least one of the windings; and
R w represents a resistance of at least one of the windings.
2. The disk drive as recited in claim 1 , wherein the control circuitry is operable to adjust the sinusoidal driving voltage so that the lead angle is approximately equal to:
arctan
(
ω
e
L
w
×
I
max
K
e
ω
+
R
w
×
I
max
)
when
√{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}≦ V max
where V max represents a target maximum magnitude of the sinusoidal driving voltage.
3. The disk drive as recited in claim 2 , wherein when
√{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}> V max
the control circuitry is operable to adjust the sinusoidal driving voltage so that the lead angle is approximately equal to the lesser of:
arctan
(
ω
e
L
w
R
w
)
and
arccos
(
V
max
2
+
(
K
e
ω
)
2
-
I
max
2
[
R
w
2
+
(
ω
e
L
w
)
2
]
2
×
V
max
×
K
e
ω
)
.
4. A method of operating a disk drive, the disk drive comprising a head actuated over a disk, and a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings, the method comprising:
applying a sinusoidal driving voltage to each winding of the spindle motor;
measuring a back electromotive force (BEMF) voltage generated by at least one of the windings;
measuring a rotation speed of the spindle motor;
adjusting the sinusoidal driving voltage in order to optimize a lead angle relative to the rotation speed and a target maximum current applied to at least one of the windings, wherein the lead angle represents a degree the sinusoidal driving voltage leads the BEMF voltage; and
adjusting the sinusoidal driving voltage so that the lead angle is approximately equal to:
arctan
(
ω
e
L
w
×
I
max
K
e
ω
+
R
w
×
I
max
)
where:
ω represents the rotation speed of the spindle motor;
ω e represents an electrical rotation speed of the spindle motor;
I max represents the maximum current;
K e represents a voltage constant of the spindle motor;
L w represents an inductance of at least one of the windings; and
R w represents a resistance of at least one of the windings.
5. The method as recited in claim 4 , further comprising adjusting the sinusoidal driving voltage so that the lead angle is approximately equal to:
arctan
(
ω
e
L
w
×
I
max
K
e
ω
+
R
w
×
I
max
)
when
√{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}≦ V max
where V max represents a target maximum magnitude of the sinusoidal driving voltage.
6. The method as recited in claim 5 , wherein when
√{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}{square root over (( K e ω+R w I max ) 2 +(ω e L w ) 2 )}> V max
further comprising adjusting the sinusoidal driving voltage so that the lead angle is approximately equal to the lesser of:
arctan
(
ω
e
L
w
R
w
)
and
arccos
(
V
max
2
+
(
K
e
ω
)
2
-
I
max
2
[
R
w
2
+
(
ω
e
L
w
)
2
]
2
×
V
max
×
K
e
ω
)
.