Burkert 8205 Notice D'utilisation page 96

APPENDIX
On the basis of Kcrit and Tcrit, the controller parameters can then be calculated in accordance with
the following table:
Parameter settings according to Ziegler und Nichols :
Controller type
P controller
P controller
P controller
The Ziegler and Nichols adjustment rules were determined for P systems with a time delay of the
first order and a dead time. However, they apply only to controllers with a disturbance response,
but not to controllers with a command response.
Adjustment rules according to Chien, Hrones and Reswick (manipulated variable methode):
When using this method, the controller parameters are adjusted on the basis of the control
system's transition response. A 100% change in the manipulated variable is output. The time Tu
and Tg are derived from the progression of the actual value of the control variable (following
figure). Ks is the proportional action coeffficient of the control system.
Actual value
Figure : Progression of the controlled variable after a manipulated variable change ∆Y
Method :
- Set the controller to MANUAL mode.
- Output a manipulated variable change and record the controlled variable with a recorder.
- Switch off in good time if you encounter critical progressions (e. g. a risk of overheating) (Pay
attention to the fact that, in thermally inert systems, the actual value of the controlled variable
may increase further switching off).
Parameter settings
Kp = 0,5 Kcrit
Kp = 0,45 Kcrit
Kp = 0,6 Kcrit
Y
100%
X
KS.
X
Tu
E-46-
PH CONTROLLER 8205
Tn = 0,85 Tcrit
Tn = 0,5 Tcrit
Y
X
Tg
Tv = 0,12 Tcrit
t
t