L12: Feedforward + Ratio Control

Prerequisites: L11 | Effort: 60 min | Seborg: Chapter 15

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Learning Objectives

1. ✅ Understand feedforward control (measure disturbance, compensate)
2. ✅ Implement ratio control (maintain 3:1 ratio)
3. ✅ Combine feedforward + feedback (FF+FB)
4. ✅ Compare FF+FB vs feedback-only performance

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Theory Recap: Feedforward (Seborg Ch. 15)

Feedforward Logic: - Measure disturbance before it affects process - Calculate corrective action - Adjust manipulated variable proactively

Example: - Distillation: Measure feed flow, adjust steam proportionally - Ratio control: Maintain reactant A:B = 3:1

FF+FB Structure: - FF handles predictable disturbances - FB handles model mismatch and unknowns

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Odibi Hands-On

Example 1: Ratio Control (3:1)

# ratio_control.yaml
# Maintain Flow_B = 3.0 × Flow_A

Working example: /examples/cheme_course/L12_feedforward/ratio_control.yaml

Example 2: FF+FB Combination

Working example: /examples/cheme_course/L12_feedforward/ff_fb_combined.yaml

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Summary

• ✅ Feedforward measures disturbances, acts proactively
• ✅ Ratio control maintains fixed proportions
• ✅ FF+FB combines best of both

Next: L13: Nonlinearity

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