Ransburg DynaFlow User Manual - Manual (Page 63)

LN-9400-00.9
DynaFlow TM User Manual - Operation
59
pressure. This is due to the Integral term of the
PID control. If the restriction causing the low
flow condition is removed suddenly while a large
control output signal exist, then a relatively long
amount of time is required for the Integral term
of the PID to reduce the control output back to a
normal range since the Integral term is proportional
to time and also due to the inherent response of
the system. If fluid flow response has changed
significantly with the same setup that previously
produced good response, then inspect the system
for component failure, blockages, and check the
fluid type and viscosity.
Alternate PID Equation
The normal PID equation is based on the error
between the desired set point and the actual flow
rate for the CHANNEL. If the set point is varied
dynamically by a PLC via RIO or by a robot via
Analog Input, it may be desirable to implement
an alternate form of the equation. The alternate
form of the equation uses the set point for the
proportional term of the equation. The Integral
and Derivative terms are the same, but slightly
different scale factors are used.
To enable the alternate PID equation, turn on DIP
SW1-4 (or SW1-8) on the Channel Module for
each CHANNEL of the GUN.
PID Tuning Methods - Standard
PID
1. Select the nominal flow rate for the GUN.
2. Set Kp and Kd parameters to zero. Do this
for both CHANNELS if this is a two-component
GUN.
3. Set Ki for the Slave CHANNEL to zero (as-
suming this is a two-component GUN).
4. Set Ki for the Master CHANNEL to the de-
fault value shown in "Default Control Parameters"
chart and "Typical Ranges for Control Parameters"
chart in this section.
5. Cycle the GUN from READY to RUN so the
new parameters are sent to the Channel
Module(s).
6. Trigger the GUN. If the flow rate does not
oscillate, or the oscillations decrease in amplitude
in a few seconds, increase Ki by 100 and repeat
from step 5. If the flow rate oscillates with increas-
ing amplitude, decrease Ki by 50 and repeat from
step 5. 8If the flow rate oscillates with a constant
amplitude, proceed to step 7.
7. Set Ki to one-half the present value.
8. Set Kp to the default value shown in the "Default
Control Parameters chart" and Typical Ranges for
Control Parameters chart" in this section.
9. Cycle the GUN from READY to RUN so the
new parameters are sent to the Channel Mod-
ule(s).
10. Trigger the GUN. If the flow rate does not
oscillate, or the oscillations decrease in amplitude
in a few seconds, increase Kp by 30 and repeat
from step 9. If the flow rate oscillates with increas-
ing amplitude, decrease Kp by 15 and repeat from
step 9. If the flow rate oscillates with a constant
amplitude, proceed to step 11.
11. Set Kp to one-third the present value.
12. Cycle the GUN from READY to RUN so the
new parameters are sent to the Channel
Module(s).
13. Trigger the GUN. If the flow rate does not
oscillate, proceed to step 14. If the flow rate is
oscillating, reduce Ki by 50 and/or reduce Kp by
15 and repeat from step 12.
14. At this point, the tuning procedure is completed
for most flow control applications. However, if
there is a great amount of lag time from
the point of sensing the flow rate to where the
material volume regulator is located, the derivative
term of the PID equation may be required. In that
case, set Kd to the default value shown in "Default
Control Parameters" chart and "Typical Ranges
for Control Parameters" chart in this section.
15. Cycle the GUN from READY to RUN so the
new parameters are sent to the Channel
Module(s).