3.6 Setting the Configuration Chapter 3: Configuration
148 493-0736-11 (6-2)
By determining the four key parameters L, T, ∆ y and ∆u from a step response,
the three process parameters static gain K
p
, dominant time constant T
p
and dead-
time L
p
can be determined according to the expressions below:
T
p
= T
L
p
= L
Knowing these, the pPI’s parameters can easily be calculated:
T
p
= T
L
p
= L
Example
If the four key parameters are found to have the following values:
∆ y = y1 – y0 = 80 – 20 = 60%
∆ u = u1– u0 = 20 – 10 = 10%
T = t2 – t1 = 60 – 40 = 20 s
L = t1 – t0 = 40 – 20 = 20 s
... then we get ...
T
p
= T = 20 s
L
p
= L = 20 s
... and the controller should be set up according to ...
TI = T
p
= 20 s
K
p
=
∆ y
∆ u
K =
1
K
p
K
p
=
∆ y
∆ u
=
60
10
= 6
K =
1
K
p
=
1
6
≈ 0.17
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