Feedforward Control - HEIDENHAIN TNC 415 Technical Manual

3.2.2 Feedforward control

Control with feedforward control means that the nominal velocity value for the machine is varied by
a machine parameter (control element of the nominal velocity). Together with the velocity element
which is calculated from the lag (servo-controlled element of the nominal velocity), this gives the
final nominal velocity value.
The lag is very small with this method. Operation with feedforward control has the advantage that
contours can be followed very accurately at a high speed. Normally, work will be carried out using
feedforward control.
MP1390 switches feedforward control on in the "Positioning with manual data input", "Program
run/single block" and "Program run/full sequence" modes. MP1391 has the same effect for the
"Manual" and "Handwheel" modes.
Operation with feedforward control for the X axis can be shown in a simplified form in the following
block diagram. All machine parameters which influence the servo characteristic are shown here.
Position approach speed
Acceleration:
Transient response: MP1520
MP1520
v
t
s=s +v·∆t
0
4-74 TNC 407/TNC 415/TNC 425
MP1060
v
Y
v
X
X
nom. +
s
X
-
s
Y
3 Servo positioning of the NC-axes
k v factor for
feed precontrol
MP1510
v x
+
s
ax
+
s ax
U
t
Integral factor: MP1080
Servo
amplifier
v nom
+
x
+
-
+
01.98