Contents
The presentation is organized as follows:
PROCESS OVERVIEW
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In a first step a general survey of the vapour pressure controlled
Czochralski crystal growth process (VCz) is given. This process was originally
developed by the Institute of Crystal Growth, Berlin. It is based on research
results achieved in the 70's. More ...
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CONTROL TASKS
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Then the main problems in control design for this process are presented.
It will be seen that an appropriate selection of the variable to be controlled
is a major issue. With a good choice simple mathematical models can be
used for control design. More ...! |
OBSERVERS
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Unfortunately, it is not possible to measure all variables to be controlled.
However, nonlinear observers are used for estimating unmeasured quantities,
the crystal radius for instance. Ideas which are helpful for designing
such observers are sketched. More .... |
PULLING VELOCITY CONTROL
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Estimated values are used in an exactly linearizing feedback controller
which controls the pulling velocity. This control system can be used for
compensating high frequency disturbances. More
.... |
TEMPERATURE CONTROL
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Temperature is controlled by an outer loop using the heater power as
control input. More .... |
JOBS, STUDENT'S JOBS, ETC.
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If you are interested in advanced control strategies there may be some
research positions available. Students should never hesitate asking for
students and diploma thesis subjects.More ....
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