Publicité
8/14
Bosch Rexroth AG Hydraulics
Function
The combination of basic card and daughter card is shown
in the block diagrams on page 3 and 4. Details of the daugh-
ter card, i.e. the pressure control, result from a detailed
block diagram on page 9.
The command value p (z12) is specified by the user by
a voltage 0...+10 V, e.g. by means of a potentiometer which
can be supplied from z32/b12 (z10 to 0 V).
The actual value p is supplied by a pressure sensor. Option-
ally, sensors with current signal interface 4...20 mA or volt-
age signal interface 1...6 V and/or 0...10 V can be used.
Zero point and sensitivity of the sensor can be set at the
front plate. Cable break of the pressure sensor is signalized
(LEDs flash) if the sensor is supplied at z6.
Command and actual value are compared in the summing
point which is moreover affected by a differentiated actu-
al value.
Principle of the control loop
Actual value p
Basic card
Pressure sensor connection versions
U
sup
P
I
sig
I
Command value p
+
D element
T
V
Pressure increase
U
z6
sup
P
0 V/
U
z14
U
sig
b18
b12
VT-VARAP1-...-2X/... RE 30058/06.12
The control deviation is amplified by a PID controller and
reaches a limiter superimposing the command value Q with
the pressure controller signal if p
As long as p
> p
or if the command value Q rang-
command
actual
es between 0...–10 V, the limiter and thus the pressure con-
trol do not take effect and there is simple flow control.
The characteristic of the PID controller and the D ele-
ment can be roughly set by means of the DIL switch on the
daughter card and finely by means of the HEXCODE switch
on the front plate. If the pressure is regulated, this condition
is displayed on the front plate (LED) and can be used for
switching purposes via an acknowledgement output (z24).
However, the pressure control can also be switched off so
that there is only flow control, independent of p
P element
K
P
T
I
I element
Limiter
z6
P
b18
b16
U
b18
b12
≦ p
.
command
actual
.
actual
Command
value Q
U
z6
sup
0 V/
b12
U
b16
sig
0 V
b18
sig
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