bürkert 8624-2 Bedienungsanleitung Seite 32

I fraction:
Function:
T is the integration or floating time. It is the time that expires until the controller
i
output has run through the entire correcting range.
Characteristic and step response of the P fraction of a PI controller
control range ∆x
Characteristic
Characteristics
A purely I controller completely eliminates the effects of disturbances. It thus has a
favourable static behaviour. Because of its finite correcting speed, it works more
slowly than a P controller and tends to oscillation. It is hence dynamically relatively
unfavourable.
Superimposing the P and I fractions:
With a digital controller with sampling time T
write:
y : controller output
K : amplification factor
p
x : deviation (x
d
T : sampling time
A
T : reset time
N
30 - 8624-2 Standard
1
∫ ∫ ∫ ∫ ∫ x
y = dt
T
d
i
x
d
c
∑ ∑ ∑ ∑ ∑ x
y = K (x + T /T
p d A N
= w - x)
d
x
x
d
y
max
y
min
Floating time T
Step response
and noting that T
A
)
d
i
= K /T one can
i p N,