Swann AMI Phosphate-II Operator's Manual page 76

AMI Phosphate-II
Program List and Explanations
As control out-
put
74
Signal outputs can be used for driving control units. We distinguish
different kinds of controls:
 P-controller: The controller action is proportional to the devi-
ation from the setpoint. The controller is characterized by
the P-Band. In the steady-state, the setpoint will never be
reached. The deviation is called steady-state error.
Parameters: setpoint, P-Band
 PI-controller: The combination of a P-controller with an
I-controller will minimize the steady-state error. If the reset
time is set to zero, the I-controller is switched off.
Parameters: setpoint, P-Band, reset time.
 PD-controller: The combination of a P-controller with a
D-controller will minimize the response time to a fast change
of the process value. If the derivative time is set to zero, the
D-controller is switched off.
Parameters: setpoint, P-Band, derivative time.
 PID-controller: The combination of a P-, an I - and a D-con-
troller allows a proper control of the process.
Parameters: setpoint, P-Band, reset time, derivative time.
Ziegler-Nichols method for the optimization of a PID controller:
Parameters: Setpoint, P-Band, Reset time, Derivative time
Y
a
L
A Response to maximum control output
B Tangent on the inflection point
X Time
The intersection point of the tangent with the respective axis will re-
sult in the parameters a and L.
Consult the manual of the control unit for connecting and program-
ming details. Choose control upwards or downwards.
B
A
X
Xp
Tn
Tv
= 1.2/a
= 2L
= L/2
A-96.250.641 / 290312