Burkert 8630 Operating Instructions Manual page 129

8.2 Characteristics of PID controllers
A PID controller has a proportional, an integral and a differential component (P, I and D components).
P component:
Function: Y = Kp · Xd
Kp is the proportional action coefficient. It results from the ratio of the manipulating range ∆Y to the proportional range ∆Xd.
Fig. 8.1: Characteristics and step response of the P component of a PID controller
Characteristics:
Theoretically, a pure P controller operates without delay, i. e. it is fast and therefore dinamically favorable. It has a lasting system
deviation, i. e. it does not balance out the effects of disturbances completely and is therefore relatively unfavorable from the static
point of view.
I component:
Function: Y =
Ti is the integration or manipulating time. This is the time that elapses before the manipulated variable has passed through the
complete manipulating range.
Fig. 8.2: Characteristics and step response of the I component of a PID controller
Top Control Positioner
Proportional range ∆ Xd
Characteristic
1
∫ ∫ ∫ ∫ ∫ Xd dt
Ti
Control range ∆Xc
Characteristics
Step response
Manipulating time Ti
Step response
129