Biosystems Control Design
Chapter 23 addresses a variety of synthesis problems in the field of biosystems:
Pharmaceutical Operations
Bioreactors
Crystallizers
Granulation
Drug Delivery
Type 1 Diabetes
Blood Pressure Control
Cancer Treatment
Controlled Treatment for HIV/AIDS
Cardiac Assist Devices
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Figure 23.1 Schematic of a typical industrial fermentor.
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Figure 23.2 Step response of fermentor model to symmetric changes in dilution of magnitude 10% from the nominal value of D=0.202 h-1.
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Figure 23.3 Step response of fermentor model to symmetric changes in dilution of magnitude 10% from the nominal value of D=0.0389 h-1.
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Figure 23.4 Flowsheet of a typical industrial crystallizer showing concentration and temperature controllers, including cascade control for temperature.
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Hierarchy of Process Information
Need relationships between levels to deliver product which consistently meets the customers needs
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Specific Challenges in Agglomeration Control
Various process operations
polymerization
spray drying
Common characteristics
complex heat/mass/momentum transfer problems
multiple attributes of interest (size, shape, concentration, etc.)
high dimension, stiff models
underactuated
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Granulation Control – Challenges
Multivariable interactions (5th and 90th percentiles)
No target (setpoint) for 5th and 90th percentiles
Data acquisition is difficult.Suggested Operating Objectives:
Minimize control effort if PSD within limits
Strong action if PSD out of limits
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Figure 23.5 Process flowsheet for granulation circuit with recycle.
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Case Study
[Pottman, Ogunnaike, Adetayo, and Ennis, Powder Tech., 1999]
Correlated Process Variables
Manipulated Variables
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Figure 23.6 Simplified process flowsheet for granulator example. Here u1, u2, u3 are, respectively, nozzles 1,2, and 3, and y1, y2, y3 are, respectively, bulk density, d5 and d90.
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Figure 23.7 Closed-loop response of granulator to +10 step change in set point for y1 – left plot is outputs, right plot is inputs (dashed line, y1 and u1; dotted line, y2 and u2; dash-dot line, y3 and u3).
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Figure 23.8 Closed-loop response of granulator to +50 step change in set point for y1 with constraints enforced on the inputs. The left plot is outputs, right plot is inputs (dashed line, y1 and u1; dotted line, y2 and u2; dash-dot line, y3 and u3).
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Diabetes Mellitus
World’s most common and costly disease
About one in every 400 to 600 children and adolescents has type 1 diabetes mellitus (T1DM)
National Diabetes Fact Sheet, 2005, Centers for Disease Control and Prevention
Complications of T1DM reduce life expectancy by ~15 years through micro- and macro-vascular disease
Blindness
Kidney disease
Nervous system disease
Evidence that intensive insulin therapy (IIT) reduces complications
Increased hypoglycemic events with IIT
Diabetes Control and Complications Trial Research Group, 1993
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Model-Based Control Approach for Diabetes
[Parker, Peppas, Doyle III, IEEE Trans Biomed. Eng. 1999]
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Figure 23.9 Block diagram for artificial β-cell, illustrating the meal as the most common disturbance. G denotes the blood sugar of the patient, Gm is the output of the glucose sensor, and Gsp is the glucose setpoint.
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Figure 23.10 Open-loop response of patient’s blood glucose when the insulin pump is turned off.
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Figure 23.11 Open-loop response of the patient’s blood glucose to a constant infusion rate of 15 mU/min from her insulin pump.
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Figure 23.12 Open-loop response of patient’s blood glucose to a constant infusion rate of 25 mU/min from her insulin pump.
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Figure 23.13 Closed-loop response of patient’s mean arterial blood pressure and cardiac output to a -10 mmHg change in the MAP set point.