INSTALLATION Series
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Edition 2018-08-20 605262EE
4.6.7 LEARN (adaptive)
LEARN adapts the PID controller of the valve to the vacuum system and its operating conditions. LEARN
must be executed only once during system setup. The LEARN routine determines the characteristic of
the vacuum system. Based on this, the PID controller is able to run fast and accurate pressure control
cycles.
This characteristic depends on various parameters such as chamber volume, conductance and flow
regime. Therefore it must be performed with a specific gas flow according to instruction below.
The result of LEARN is a pressure versus valve position data table. This table is used to adapt the PID
parameters. The data table is stored in the device memory which is power fail save. The data table can
be up-/downloaded via ‘Control Performance Analyzer’ software or remote interface. Due to encoding the
data may not be interpreted directly.
By an OPEN VALVE, CLOSE VALVE, POSITION CONTROL or PRESSURE CONTROL command the
routine will be interrupted.
Local operation:
(‘Control Performance Analyzer’ or ‘Service Box 2‘)
Remote operation:
With CPA:
• Do the LEARN in menu ‘Pressure Control
/ Learn’.
With SB2:
• Go to ‘LOCAL / LEARN’ and follow
instructions.
Gasflow calculation according to recommendation
below is done automatically based on inputs.
1. Set specific gas flow according to
calculation below and wait until flow is
stable. Autolearn does not need to be
performed with the process gas. Instead N
2
or Ar may be used.
2. Set the “Learn pressure limit”
3. Go to «EtherCAT object – Index 2118h» >
«MAXIMUM LEARN PRESSURE» and set
valid value
4. Read back the «EtherCAT object – Index
2118h» > «MAXIMUM LEARN
PRESSURE» and verify the correct setting
5. Go to «OUTPUT Buffer» > «CONTROL
MODE SETPOINT»
6. Set «Learn» (value = 7) and Learn
procedure is started
7. Wait until learn procedure is finshed and
«LEARN TERMINATED BY PROGRAM»
at «EtherCAT object – Index 2119h» >
«LEARN STATE» is set.
Sensor signal must not shift during LEARN. Wait until sensor signal is stable before
LEARN is performed. Learn may take several minutes. Do not interrupt the routine as
a single full run is required to ensure fast and accurate pressure control. The
PID controller covers 5% to 5000% of the gas flow which was used for learn.
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