Burkert Type 1110 - Handbuch (Seite 17)

1110 - 15
DIGITAL INDUSTRIAL CONTROLLER
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If a control task consists of keeping a quantity (e.g. a temperature) at a fixed setpoint
SP (constant), a fixed setpoint control configuration is used for this purpose. The
control variable PV (temperature) is measured and compared against the setpoint
SP (Figure 5).
Figure 5: Single control loop
If it deviates from the setpoint as the result of a disturbance Z, for example, the
controller generates a manipulated variable CO according to this deviation, which is
referred to as the system deviation PVd = SP-PV, in such a way that the controlled
variable PV is adapted as exactly as possible to the setpoint.
A PID controller can be used for this purpose. With regard to its parameters, it must
be configured so as to arrive at a control response that does justice to the task in
hand (see Annex).
Example:
Let us look at control of a room’s temperature as an example of a fixed setpoint
control configuration in a single control loop. The aim is to compensate all
disturbances that cause the room temperature to deviate from the temperature
setpoint. The room temperature is compared against the setpoint SP. According to
the system deviation PVd, the controller adjusts the fuel supply until the required
room temperature has been reached.
5.2 Controller for single control loop
5.2.1 Single control loop
5.2.2 Standard controller structure
The standard controller structure shown in Figure 6 is obtained by configuring the
overall structure appropriately. It is based on PID controller 2. PID controller 1 is not
used. Input 1 is used for the controlled variable PV1, while input 2 is not used. SP1
is the setpoint that has to be set.
Setpoint
generator
Controller Controlled system
FS
PV
Z
SP PVd
FR
CO