Pacific Scientific OC950 - Advanced Velocity Loop Tuning

Overshoot Setting KVFF equal to 100% can result in position overshoot.
Somewhat lower values may be required if this is a problem.
KVFF set to 70%-80% typically achieves the fastest step response
with no overshoot. However, setting KVFF to less than 100%
will give steady state following error when running at constant
speed.
4.3 Advanced Velocity Loop Tuning
Continuous time
transfer function
approximation
The transfer function for the velocity loop compensation block is
given below:
FVelErr
VelErr
s
s
Q
s
s
zzz
f
()=








++








ωω
ω
2
2
1
1
++
1
1
Q
s
ff
ω
ICmd
VelErr
s
s
Q
s
s
Q
zzz
f
()=








++








+
ωω
ω
2
2
1
1
1
()
()
ff
s
KVP
KVI
s
ω
π
+
+








1
1
2
Definitions for the terms used in the equations above are shown
on the following page.
4-10 MA950