VAT 613 Series

OPERATION Series
613
108/149 Edition 12.08.2022 984360EC
6.3.4.3 Soft Pump/Vent algorithm
This control algorithm may be used to control pressure ramps during pump down or venting the
chamber. This is a modified PI controller that has been optimized to start up very gently when the
valve is opened.
6.3.4.4 Control Parameter
Location: CPA/Navigation/Parameters: Pressure Control.Controller x,Control Settings
Parameter Description
P
-
Gain
The
P
-
Gain
is the proportional factor of the fixed control algorithm. A
higher P-Gain results in faster response, higher over- / undershoot of
pressure.
I
-
Gain
The
I
-
Gain
is the integral factor. The
I
-
Gain
helps to reach the target
pressure exactly.
Pressure
Scale
Linear
Logarithmic Recommended if the pressure control extends over
several decades. In most cases, the sensor used is
a logarithmic sensor anyway.
Direction
The
Control Direction
defines the type of application, if the valve is
mounted in downstream or upstream. Downstream means the valve
is after the chamber and before the pump. Upstream, valve is
mounted before chamber and pump.
Ramp
Only the ramp makes the soft pump or soft vent…
See chapter «Pressure Ramp»
6.3.4.5 Tuning
Optimizing P-Gain
Start optimization with P-Gain set to 0.1 and I-Gain set to 0.0.
The control routine has to be controlled as follows:
• Move control valve into close position
• Start pump down by opening the pump isolation valve or starting the pump
• Send the pressure set point to the valve controller.
While pumping/venting the chamber pressure and valve position should be data logged to compare
the actual curve with the ideal straight pump/venting line.
If the pressure follows the ideal pump/venting line with significant delay, the P-Gain is too low.
If the pressure oscillates around the ideal pump/venting line or if the valve position oscillates, P-Gain
is too high.
P-Gain is optimized if the pressure follows the ideal pump down line closely and the valve position is
not oscillating at all.