HEIDENHAIN TNC 335 Technical Manual - Manual (Page 157)

4-60
TNC 360 3 Servo Positioning of the NC Axes 8/95
3.2.2 Control with feed forward
Feed forward 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 feed forward control has the advantage that
contours can be followed very accurately at a high speed.
Normally, work will be carried out using feed forward control.
In the operating modes "Positioning with manual data input", "Program run, single block" and
"Program run, full sequence" this method of servo control can be selected with the machine
parameter MP1390.
Operation with feed forward 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.
v
X
v
Y
s
Y
s
X
➁
vx
sax
s
ax
X
Noml
v
x
Noml+
Servo
amplifier
Integral factor: MP1080
X
Actl
U
t
➂
➃
v
t MP1530
MP1520
s=s
0
+v·
∆
t
+
-
v
x
Actl
+
+
+
➀
Acceleration: MP1060
Transient response: MP1530
Position approach speed: MP1520
+
-
kv factor for
speed pre-control
MP1510
v=a
·t
v
=
k v
·s a
x