HEIDENHAIN ITNC 530 - Page 648

1– 648 HEIDENHAIN Service Manual iTNC 530
The interpolator The interpolator operates at a prescribed clock rate, the position controller cycle time.
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
path
is formed from the
appropriate axis components. The same applies to rapid traverse in the path.
The position
controller
With the iTNC 530 the user can choose between two types of feedback control:
 Feedback control with following error (servo lag)
 Feedback control with velocity feedforward
Operation 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.
Figure: Simplified illustration of feedback control with following error
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
Machine
parameter
Following
error
Feed
forward
control
For the operating modes
MP 1391.0 0 1 Manual and handwheel
MP 1392 0 1 Positioning with manual data input,
Program Run Single Block
Program Run, Full Sequence
Note
The machine should be adjusted for both types of control.
v
Noml
S
Noml
S
Actl