Micromod Micro-DCI: 53SL5100A Single Loop Controller - Manual (Page 117)

Single Loop Process Controller Instruction Manual
Easy-Tune 109
11.5 Modifications to Tuning Criteria
During EASY-TUNE sequence execution, each of the three algorithm variables: Time Constant (
T P ),
Process Gain (
K P ), and Dead-Time (
W P ), are altered by 10% in the conservative direction, (instrument
operating characteristics would be slower response, but less chance of oscillation and instability) before
the tuning parameters are computed using the ITAE equations listed in
Table 11-4 . ( Figure 11-2 illustrates
the equation variables with respect to the response curve.)
The three variables
T P ,
K P , and
W P can be increased numerically to compute tuning parameters that are
more conservative, or decreased for less conservative tuning parameter calculations (instrument operating
characteristics would be faster response and greater chance of instability or oscillation). Parameters used
to alter the variables are the EASY-TUNE Modifiers, datapoints C382 (
T P Modifier), C383 (
D P Modifier), and
C384 (
W P Modifier). It is recommended that the values entered in C382, C383, and C384 be between -0.5
and 0.5. The effect on the equation variables is as follows:
T P modified = T P (1 - C382)
K P modified = K P (1+ C383)
W P modified =
W P (1+ C384)
Table 11-4. EASY-TUNE Equations
Mode PB in % TR (Minutes) TR* (Minutes)
P 204
K P (
W P /
T P )
1.084
0 0
PI 116.4
K P (
W P /
T P )
0.977
(
T P /40.44)(
W P /
T P )
0.68
0
PID 73.69 K P ( W P / T P )
0.947
( T P /51.02)( W P / T P )
0.738
( T P /157.5)( W P / T P )
0.995
PD** 54.02 K P ( W P / T P )
0.947
0 ( T P /157.5)( W P / T P )
0.995
i** 0
T P [(K P /25)(
W P /
T P )
0.15
] 0
Note: Process characteristics T P , K P , and W P are used to compute the ideal tuning parameters according to the
Minimum Integral of Absolute Error Multiplied by Time Criterion (ITAE) for P, PI, and PID modes.
*If computed to be < B003/50, then T D = 0.
**Empirical estimates, not based on ITAE method.
✎ Note
The approximation of a process step response curve by a first order
time lag plus dead-time model is done by equating their values at
0.2835 and 0.6321 fraction of the total excursion.