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Theory of Operation
Volume Compensation
The PrecisionFlo module compensates for changes in
material viscosity by:
1.
Comparing actual flow rate with the flow rate
commanded by the robot.
2.
Increasing or decreasing material pressure until
the required flow rate is achieved.
The PrecisionFlo module performs this comparison
and correction after a fixed number of pulses from the
flow meter (Fig. 38). Automatic mode automatically
determines the interval, Manual mode permits the user
to set the interval.
Choice: Number of Flow
Meter Pulses
Determined By:
PrecisionFlo Module
Automatically:
Auto
PrecisionFlo
module
1. Calculates current
flow rate.
2. Compares current
flow rate to re-
quested flow rate
Manual
User
quested flow rate.
3. Compensates for
changes in flow
rate.
Off
N/A
Turns off volume com-
pensation
Volume Compensation Algorithm
The algorithm for controlling flow:
1.
Find the pressure from commanded flow and flow
calibration curve.
2.
Multiply the pressure by the flow correction gain.
Send the corrected pressure as a command to the
metering valve.
3.
If the flow meter has registered the correct number
of pulses (i.e. the flow correction interval of volume
has been dispensed):
a.
Calculate the actual flow from the number of
pulses
b.
Compare the commanded flow to actual flow.
If the actual flow is greater than the comman-
ded flow, decrease the flow correction gain
by 1%.
If the actual flow is less than the commanded
flow, increase the flow correction gain by 1%.
Fig. 38
0
1
2
3
4
Constant = N
Flow meter
pulses
Command
Integral of
command =
commanded
volume
V
c
Reset and
start over
V
c
can
vary
0
1
0
0
0
N = number of pulses
V
c
= Volume Commanded