July 2013 6.8 The control loop 833
Feedback control
with following error
Following error (also known as servo lag) is a gap that remains between the
nominal position commanded by the NC and the actual position.
Simplified representation:
The nominal position value s
noml
for a given axis is compared with the actual
position value s
actl
and the resulting difference is the following error s
a
:
s
a
=s
noml
– s
actl
s
a
= following error
s
noml
= nominal position value
s
actl
= actual position value
The following error is multiplied by the k
v
factor and passed on as nominal
velocity value:
v
noml
=k
v
· s
a
v
noml
= nominal velocity value
Analog axes (control via CMA-H):
For stationary axes, the integral factor has an additional effect (MP1080.x). It
produces an offset adjustment.
Digital axes:
There is no offset. MP1080.x has no function.
v
Noml
S
Noml
S
Actl
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