5.5.2
P(ID) controller
The Liquisys M supports the definition of various controller functions. On the basis of the PID
controller, P, PI, PD and PID controllers can be implemented. To obtain the best control
response, use the controller best suited to the application in question.
•
P controller:
Used for simple linear control purposes with small system deviations. Where
major changes are to be controlled, overshooting may occur. A control offset is to be
expected.
•
PI controller:
Used for processes where overshooting is to be avoided and permanent
offsets are not allowed.
•
PD controller:
Used for processes that require quick response and where peaks are to be
corrected.
•
PID controller:
Used for processes for which the type of control provided by a P, PI or PD
controller is inadequate.
Adjustments of P(ID) controller
Three parameters can be adjusted in the case of a PID controller:
• the control gain K
p
(P influence)
• the integral action time T
n
(I influence)
the derivative action time T
v
(D influence)
Start-up
If there are no empirical values available for setting the control parameters, use values that
provide the greatest possible stability of the control loop. To optimise the control loop further:
• Increase the control gain K
p
until the control variable just starts to overswing.
• Decrease K
p
again slightly and shorten the integral action time T
n
to achieve the shortest
possible correction time without overswing.
• In order to shorten the response time of the controller, you also have to set the derivative
action time T
v
.
OM23FE5B.CHP
Liquisys M COM 223 F / 253 F
Instrument configuration
Hauser
35
