Manual 37615C
SPM-D2-10 - Synchronizing Unit
Page 28/68
© Woodward
Analog Controller Outputs
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The analog PID controller forms a closed-loop control loop together with the controlled system (usually a first-
order lag element). The parameters of the PID controller (proportional-action coefficient K
P
, derivative-action
time T
V
and reset time T
n
) can be modified individually.
Kp
T1
Controlled system (PT1)
PID controller
Kpr
Tn
Tv
Lag element (Tt)
Influenciny
quantity
Tt
Figure 5-1: Control loop
If an abrupt disturbance variable is applied to the control loop, the reaction of the controlled system can be rec-
orded at the output as a function of time (step response).
0
t/s
x
T
T
1
0
T
x
x
d
m
x
d
x
m
T
Rise time
Overshoot
System deviation
rise
rise
Tolerance band
Settling time
sett
sett
Figure 5-2: Step response (example)
Various values can be obtained from the step response; these are required for adjusting the controller to its opti-
mum setting:
Rise time
T
rise
:
Period starting when the value of the control variable leaves a predefined tolerance range for the
control variable following a jump in the disturbance variable or reference input variable and ending the first time
the value re-enters this range.
Setting time
T
sett
:
Period starting when the value of the control variable leaves a predefined tolerance range for
the control variable following a step in the disturbance variable or reference input variable and ending when the
value re-enters this range permanently.
