INSTALLATION
Series 655
44/112
Edition 23.09.2019
979645EA
4.8.3
Learn (adaptive control algorithm)
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.
•
Gasflow calculation according to recommendation below is done automatically
based on inputs
•
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.
