Siemens Sinumerik 840D Series Function Manual page 248

A Hydraulics
A.1 Servo solenoid valves
Valve amplifier
+U B
+15 V
DC
-15 V
DC
Logic
+
PID
-
S
U
Fig. A-14 Valve amplifier block diagram for directly-controlled servo solenoid valves, sizes 6 and 10 (Rexroth)
A-248
The functions of the integral valve amplifier are implemented with analog cir-
cuits, and are illustrated in the block diagram (see Fig. A-14).
The main amplifier functions are:
S
Supply and evaluation of the position sensor (AC/DC converter)
S
Comparison of setpoint input signal with spool actual value
S
Formation of manipulated variable via a PID controller for the output stage
S
Timing output stage with pulse length modulation
The amplifier is calibrated to match the valve at the factory. The zero-point is
adjusted via the NC during start-up.
+U B
SINUMERIK 840D/SIMODRIVE 611 digital, HLA Module (FBHLA) - 10.03 Edition
2.5 AF
+24 V=
O
B
C
D
100k
I
100k
F
10k
 Siemens AG, 2003. All rights reserved
10.03
Supply
0 V
0 V Reference point
Actual valve spool
value
+ - 10 V
Setpoint 0...
Sign.
Actual valve spool
value
Protective
conductor
Shield