HEIDENHAIN iTNC 530 Service Manual page 648

The interpolator operates at a prescribed clock rate, the position controller cycle time.
The interpolator
The interpolator calculates a velocity from the programmed feed rate. With the CC 424 (B) this
calculation occurs every 3 ms, and with the CC 422 the frequency of the calculation depends on
the time in MP 7600.x. The value is also dependent on the acceleration curve and the end
position.
If more than one axis is moved simultaneously, the path acceleration a
appropriate axis components. The same applies to rapid traverse in the path.
With the iTNC 530 the user can choose between two types of feedback control:
The position
controller
Following error (also known as servo lag) is a gap that remains between the nominal position
Operation with
commanded by the NC and the actual-position.
following error
Figure: Simplified illustration of feedback control with following error
The nominal position value s
and the resulting difference is the following error s
s
s
s
s
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Feedback control with following error (servo lag)
Feedback control with velocity feedforward
Machine Following
parameter error
MP 1391.0 0
MP 1392 0
Note
The machine should be adjusted for both types of control.
S
Noml
S
Actl
= s – s
a noml actl
= following error
a
= nominal position value
noml
= actual position value
actl
Feed For the operating modes
forward
control
1 Manual and handwheel
1 Positioning with manual data input,
Program Run Single Block
Program Run, Full Sequence
for a given axis is compared with the actual position value s
noml
:
a
is formed from the
path
v
Noml
HEIDENHAIN Service Manual iTNC 530
actl