Adjustment Rules For Pid Controllers; Adjustment Rules According To Ziegler And Nichols (Oscillation Method) - Burkert 8792 Operating Instructions Manual

Type 8792, 8793 Type 8792, 8793

Adjustment rules for PID Controllers

35 ADJUSTMENT RULES FOR PID CONTROLLERS
The control system Type 8793 features a self-optimization function for the structure and parameters of the
integrated process controller. The determined PID parameters can be seen via the operating menu and re-
optimized at will for an empirical path.
The regulatory literature includes a series of adjustment rules which can be used in experimental ways to
determine a favorable setting for the controller parameters. To avoid incorrect settings, always observe the
conditions under which the particular adjustment rules have been drawn up. Apart from the properties of the
control process and the controller itself, the aspect whether a change in the disturbance variable or command
variable is to be corrected plays a role.
35.1 Adjustment rules according to Ziegler and Nichols
(oscillation method)
With this method the controller parameters are adjusted on the basis of the behavior of the control circuit at
the stability limit. The controller parameters are first adjusted so that the control circuit starts to oscillate. The
occurring critical characteristic values suggest a favorable adjustment of the controller parameters. A prereq-
uisite for the application of this method of course is that the control circuit is oscillated.
Procedure
→
Set controller as P-controller (i.e. Tn = 999, Tv = 0), first select a low value for Kp
→
Set required set-point value
→
Increase Kp until the control variable initiates an undamped continuous oscillation.
The proportionality coefficient (proportional gain) set at the stability limit is designated as K
oscillation duration is designated as T
Progress of the control variable at the stability limit
Fig. 129: Progress of the control variable PID
.
krit
Actual value
X
Tkrit t
. The resulting
krit
Time
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