Inferential Control

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Inferential Control

• Control Using a Single Secondary Measurement

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Objectives

• The concept of inferential control(IFC).
• Structure and analysis of control using one
  secondary measurement.
• Inferential control versus classical control
  strategies.
• Application of IFC to a distillation column
  control

3
Applications
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Generic Inferential Control Problem
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Classical Approaches Feedback Control of
Secondary Variable
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Composition control using temperature
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Classical Approaches Cascade Control
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Classical Approaches Feedforward Control
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Classical Approaches Feedback Using an Output
Estimator
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2 DOF Internal Model Control
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Inferential Control Structure
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Disturbance Estimator
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Controller Design
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IFC Structure
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Example
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Step Responses
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Combining Feedback with IFC
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Summary

• Inferential Control is used when a measurement of
  the primary variable is not available.
• Inferential control is similar to a cascade
  control strategy.
• IFC can suppress disturbances detected by the
  secondary measurement.
• IFC can lead to bias if model errors are present
• When ever possible combine IFC with direct
  feedback control of primary variable even if it
  is infrequently measured.