User Manual

CM2N8894E / 10.1999 Siemens Building Technologies
2/4 Landis & Staefa Division
The RGB controller block contains an individual controller with positioning output and
various additional functions.
The following diagram shows a simplified version of the controller block circuit diagram:
COU (y)
SPV (w)
PRV (x)
RGB
PI
D
H
K
KREG KINT
KDIF
external
Algorithm
Selector
internal
8894Z02E
Inverter
Starter
Limiter
The above elements and functions of the controller block are:
Element Function
Algorithm The controller block contains a PID control algorithm. Entering the
associated values in the controller parameters defines the controller type
(P, PI, PID, or PD) and the control response of the closed control loop:
−
KREG for proportional amplification (P)
−
KINT for the integral portion (I)
−
KDIF for the differential portion (D)
If KINT or KDIF are set to 0, the associated portions are inactive, i.e., for
a PI controller, KDIF is set to 0.
Inverter To define the direction of control action: Heating mode (H) or cooling
mode (C)
Selector Used to select the controller status: Controller mode active (automatic
mode = normal status), manual controller mode, controller mode OFF
Limiter Used to define the upper and/or lower limits of the controller output
Starter Defines the start values at which the controller should work on start-up
or changeover operations (internal and external values).
The controller blocks are calculated cyclically for the respective plant on program
execution. This is done using the REG function in the COLBAS program as shown in
the following samples lines:
9100 @RGB2.SPV:=21
9110 @RGB2.PRV:=$020.AI
9120 $053.AO:=REG(RGB2.TA)
9999 WAIT DURING Z-MOD(TIME,Z);GOTO...
Line Interpretation
9100 The setpoint SPV is read by controller block RGB2
9110 The actual value PRV of input $020.AI is read into the controller block
9120 The REG function calculates controller block RGB2 and assigns the resultant
positioning variable directly to output $053.AO.
9999 After completing the entered cycle time Z, the control loop is restarted (general
values are 10 to 30 seconds).
COLBAS =
C
ontrol-
O
riented
L
anguage for
B
uilding
A
utomation
S
ystems
Individual
controller RGB
Block circuit diagram
Elements and
functions
Call-up and
processing