Chemical and Biological Engineering
Twin-Screw Food Extruder: A Multivariable Case Study for a Process
Control Course
Joel SchlosburgB. Wayne Bequette
• Process Control Course Overview• Case Studies
• Realistic Industrial Problems• Motivating to Students• Integrate Techniques Learned Throughout Course
BES-0411693
Process Control @ RPI
Four credit hours, Spring Junior yearThree 2-hour sessions/weekStudio: Lectures and SimulationsMajor Case Study Project
Selected from multiple options
Teamwork
Written reports & frequent meetings
Final oral presentation
Link between theory and practice“Feels real”
Multivariable
Noise, constraints
Case Study ProjectsFinal 1/3 of CourseChoice of Projects
Reactive Ion Etcher
Lime Kiln
Fluidized Catalytic Cracking (FCCU)
Anaerobic Sludge Digester
Drug Infusion Control (Critical Care)
Different Advisor (Instructor/TA/RA) for Each ProjectWritten Reports & Final Presentation To Main Column
Feed Oil from Crude Unit
T1CTYC
F s
F a
Heat Exchange
Flue Gas
Air
T rg
Crc
Tcy
T 1
Steam
T 1sp
T cysp
Riser
Reactor (actually a separator)
Regenerator
Spent Catalyst
Regenerated Catalyst
Sensors Controller
Drugs Infused
Infusion pumps
Patient
Measured variables
MAP CO
SNP DPM
setpoints
Flourine MeasurementRF PowerVoltage Bias
Measurement
Computer Control
Power
Throttle
[F]V
bias
Reactive Ion Etcher
Gases In Gases Out
Heater
flow
Flow, % of range
voltage
Voltage, V
fluorine
Fluorine, % of range
throttle, %
power, W
Clock
t
time
power disturbance, W
Etcher
LC
PC
u1
u2
heat input
inlet flowrate
y1
substrate concentration
y2
temperature
Anaerobic Digester
biogas
disgested sludge
MIMO Control
Project Stages
Literature review Week 1Model development Week 2Single input-single output (SISO) controller design Week 3Multiple loop design Week 4Oral presentation Week 5Final written report Week 5
Primary Goals: Learn MIMO Modeling, Analysis and ControlIntegrate basic concepts learned throughout the semester
Twin-Screw Cooking Food Extruder
Common food processing unit, mostly in baking industryFast-speed bioreactor with heating, cooling, compressing, mixing, evaporating, cutting, and aerating in one unitTwin-screw is now becoming more common, as it is easier to manipulate a number of parameters
www.foodprocessing-technology.comScrew Speed manipulated
Moisture content manipulated
Motor torquemeasured
Product temperature measured
Process Simulation (MATLAB/Simulink)
Step Tests to Develop Model
Input 1 Input 2
Output 1 Output 2
Step Tests to Develop ModelNoise and mismatch
Output 1 Output 2
Input 1 Input 2
SS-MT SISO ControlEffect of tuning parameter values
Relative Gain Analysis (RGA) for “Pairing”
Process Gain matrix =
λ11 & λ22 are closer to one, and therefore are the better control loop pairings.
This means the two control loops are:
SS (screw speed) controlling MT (motor torque)
MC (moisture content) controlling PT (product temperature)
⎥⎦
⎤⎢⎣
⎡=
⎥⎥⎦
⎤
⎢⎢⎣
⎡=⎥
⎦
⎤⎢⎣
⎡λλλλ
=Λ−−
−−
−−
88.12.
12.88.
21122211
2211
21122211
2112
21122211
2112
21122211
2211
kkkkkk
kkkkkk
kkkkkk
kkkkkk
2221
1211
⎥⎦
⎤⎢⎣
⎡−−−
=⎥⎦
⎤⎢⎣
⎡4.212.
87.32.
kk
kk
2221
1211
Best “Pairing” based on RGA
Simultaneous Setpoint Changes
Simultaneous Setpoint Changes
Disturbance Rejection(change in barrel temperature)
RGA Validation: Opposite Pairing
Textbook
Chapters1. Introduction 2. Fundamental Models3. Dynamic Behavior 4. Empirical Models5. Introduction to Feedback Control6. PID Controller Tuning7. Frequency-Response Analysis8. Internal Model Control 9. The IMC-Based PID Procedure10. Cascade and Feed-Forward Control11. PID Enhancements12. Ratio, Selective, and Split-Range Control13. Control-Loop Interaction14. Multivariable Control15. Plantwide Control16. Model Predictive Control17. Summary
Modules1. Introduction to MATLAB2. Introduction to Simulink3. Ordinary Differential Equations 4. MATLAB LTI Models 5. Isothermal Chemical Reactor 6. First-Order + Time-Delay Processes7. Biochemical Reactors8. Continuously Stirred Tank Reactor (CSTR)9. Steam Drum Level10. Surge Vessel Level11. Batch Reactor12. Biomedical Systems13. Distillation Control14. Case Study Problems15. Flow Control 16. Digital Control
SummaryLaptop Studio-based Course
Lectures followed by simulation-based reinforcement of theory
Case Study ProjectsChoice of 5 projects, final 1/3 of course
Integrates concepts learned throughout course
Multivariable focus
Twin screw food extruder