Manual 37615C
SPM-D2-10 - Synchronizing Unit
Page 30/68
© Woodward
1.
Controller operated as a P-only controller
(where T
n
=
[screen setting: T
n
=0], T
V
= 0).
2.
Increase gain K
P
(P gain) until the control loop oscillates continuously at K
P
= K
Pcrit
.
CAUTION
If the unit starts to oscillate uncontrollably, perform an emergency shutdown and change the screen
setting accordingly.
3.
Measuring of the cycle duration T
crit
4.
Set the parameters:
PID controller
PI controller
K
P
= 0.6
× K
Pcrit
K
P
= 0.45 × K
Pcrit
T
n
= 0.5
× T
crit
T
n
= 0.83 × T
crit
T
V
= 0.125 × T
crit
Step response
Controller setting
Optimum (x
m
10 %)
Controller setting
T
crit
Controller setting
Incorrect
0
1
x
0
t / s
0
0
1
x
t / s
0
1
x
0
t / s
Figure 5-3: Step response - controller set-up
Pr.-sensitivity
Kp=000
P gain
(K
PR
) Proportional-action coefficient
1 to 240
The proportional-action coefficient K
PR
indicates the closed-loop control system
gain. By increasing the gain, the response is increased to permit larger corrections to
the variable to be controlled. The farther out of tolerance the process is the larger the
response action is to return the process to the tolerance band. If the gain is configured
too high, the result is excessive overshoot/undershoot of the desired value.
Reset time
Tn = 00,0s
Reset time
(T
n
)
0.2 to 60.0 s
The reset time T
n
represents the I-component of the PID controller. The reset time
corrects for any offset (between set point and process variable) automatically over
time by shifting the proportioning band. Reset automatically changes the output re-
quirements until the process variable and the set point are the same. This parameter
permits the user to adjust how quickly the reset attempts to correct for any offset. The
reset time constant must be greater than the derivative time constant. If the reset time
constant is too small, the engine will continually oscillate. If the reset time constant is
too large, the engine will take to long to settle at a steady state.
Derivative act.
time Tv=0.00s
Derivative-action time
(T
V
)
0.00 to 6.00 s
The derivative-action time T
V
represents the D-component of the PID controller. By
increasing this parameter, the stability of the system is increased. The controller will
attempt to slow down the action of the throttle in an attempt to prevent excessive
overshoot
or undershoot. Essentially this is the brake for the process. This portion of
the PID loop operates anywhere within the range of the process unlike reset.
