Hardware Reference
In-Depth Information
y
ref
=8
µ
in, linear control
15
10
5
0
−5
−10
0
0.5
1
1.5
2
2.5
3
x 10
−3
time is sec
Figure 3.93: Response to 8 µin step input. Solid line: combined output, dashed
line: microactuator output, dash-dot line: microactuator input.
y
ref
=16
µ
in
30
25
20
15
10
5
0
−5
−10
−15
0
0.5
1
1.5
2
2.5
x 10
−3
time is sec
Figure 3.94: Response to 16 µin step input. Solid line: combined output,
dashed line: microactuator output, dash-dot line: microactuator input.
is required to account for the numerical error due to sampling etc. We can see
from the simulation results that the maximum allowable stable step change
(MASSC) is close to 10
(GM−1)/20
× 8. Table 3.8 summarizes the MASSC
estimated using 10
(GM−1)/20
×8 versus the actual MASSC obtained from sim-
ulations. We see from this table that the MASSC can be predicted fairly well
from the knowledge of the gain margin of C
V
P
V
.
Although increasing the gain margin of the VCM loop can increase the
MASCC, this may require the VCM loop gain to be decreased and therefore,
a relatively higher displacement range for the secondary stage actuator.
