Class 20 Enhanced SingleLoop Control Systems

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Class 20 Enhanced Single-Loop Control Systems

• Chapter 16

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How Do ExxonMobil Control Film Thickness?
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Cascade Control
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Cascade Control Block Diagram
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Cascade Control Analysis
D2
GD2

Y2
YSP2
GC2
Gv
GP2
GM2
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Cascade Control Analysis
D2
GD2

Y2
YSP2
GC2
Gv
GP2
GM2
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Cascade Control Block Diagram
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Cascade Control Block Diagram
D2
D1
GD1
Y1
YSP1
Km1
GP1
GC1
GM1
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Cascade Control Algebra
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Cascade Control Algebra
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Cascade Control Stability
Characteristic equation for the cascade loop
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Cascade Control Stability
What happens of GC2 and GM2 when the inner loop
is open?
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Cascade Control Stability
Characteristic equation for the closed cascade
loop
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Example
Determine the stability limit for a conventional
proportional controller when a cascade scheme is
implemented with
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Example
For this same system determine the stability
limit for a conventional proportional controller
when a cascade scheme is implemented with the
inner loop off-line
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Example
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Example
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Example
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Example
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Selective Control (Override)
For every controlled variable, there must be at
least one manipulated variable
In some applications
of manipulated variables
of controlled variables

• High selector

• Low selector

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Selective Control (Override)
multiple measurements one controller one final
control element
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Selective Control Example