User's Manual

Turbo PMAC User Manual
156 Motor Compensation Tables and Constants
Then compute the filter coefficients:
(
)
z
2
s
T
nzz
2
36Ixx
α
ωζ
+−
=
z
1
37Ixx
α
=
(
)
p
2
s
T
npp
2
38Ixx
α
ωζ
+−
=
p
1
39Ixx
α
=
Finally, modify the proportional-gain term to compensate for the DC-gain change that the filter creates:
p
z
2
nz
2
np
old
30Ixx
new
30Ixx
α
α
ω
ω
=
For example, suppose we have identified a 55 Hz resonance in our mechanical coupling. To compensate
for this, we decide to put a lightly damped band-reject filter (damping ratio 0.2) at 50 Hz natural
frequency, and a heavily damped band-pass filter (damping ratio 0.8) at 80 Hz natural frequency to limit
the high-frequency gain of the filter. The servo update time is the default of 442 microseconds.
sec000442.0
sec
sec
6
10sec*442
s
T =
−
=
µ
µ
secrad2.314Hz50*2
nz
== πω
secrad7.502Hz80*2
np
== πω
2
s
T
2
nz
s
T
nzz
21
z
ωωζα ++=
2
000442.0*
2
2.314000442.0*2.314*2.0*21 ++=
0748.1
=
2
s
T
2
np
s
T
npp
21
p
ωωζα ++=
2
000442.0*
2
7.502000442.0*7.502*8.0*21 ++=
4049.1
=
Next we compute the filter coefficients:
()
(
)
912.1
0748.1
2000442.0*2.314*2.0*2
z
2
s
T
nzz
2
36Ixx −=
+−
=
+−
=
α
ωζ
930.0
0748.1
1
z
1
37Ixx ===
α
(
)
(
)
677.1
4049.1
2000442.0*7.502*8.0*2
p
2
s
T
npp
2
38Ixx −=
+−
=
+−
=
α
ωξ
712.0
4049.1
1
p
1
39Ixx ===
α
Finally, we compute the DC gain adjustment, assuming for the example that our existing proportional
gain term Ixx30 had been 500,000: