193
Typ EP 501
Additional technical information
35.
PROPERTIES OF PID CONTROLLERS
A PID controller has a proportional, an integral and a differential portion (P, I and D portion).
35.1. P-portion
Function:
Y=Kp . Xd
Kp is the proportional coefficient (proportional gain). It is the ratio of the adjusting range
∆
Y to the proportional
range
∆
Xd.
Characteristic.and.step.response.of.the.P.portion.of.a.PID.controller
Characteristic
Step response
Xd
X
Ymax
Ymin
Y0
Kp
⋅
Xd
t
t
Xd
Y
Proportional range
∆
Xd
Y
Adjustment
range
∆
Y
Figure 111: Characteristic and step response of the P portion of a PID controller
Properties
In theory a pure P-controller functions instantaneously, i.e. it is quick and therefore dynamically favorable. It has a
constant control difference, i.e. it does not fully correct the effects of malfunctions and is therefore statically relatively
unfavorable.
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