Gas Fraction Control System

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• Gas Fraction Control System
• for a
• Gas Evolving Electrochemical Reactor

Craig E. Nelson - Consultant Engineer
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Reactor Controller Functional Diagram
Cathodic (Negative) current
Electric Eyes
Standby
Standby Current Source
Bubble
Set Point
Counter Anode Ec Red

Voltage Controlled Power Supply
Loop Dynamics Circuit
-
Working Cathode Ew Blue-Green
Sensor Support Circuit
Parameter Extraction Circuit
Block Diagram for Bubbleostatic Operating Mode
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Reactor Control System Block Diagram
Current Drivers
Power Supply
Parameter Extraction
Detection
Standby Current Source
I2
Standby
Bubble Detector Support Circuit
Voltage Controlled Current Source
Parameter Extraction Circuit
V2
V3
V4
V5
V1
I1
Signal Smoothing Circuit
Loop Dynamics Circuit
Controller Set point
Iout
Det1
Det2
Photons
PID Loop Dynamics
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Requirements - Loop Dynamics

• Controller should provide at least a second order
  transfer function
• Controller should provide easy adjustability of
  the transfer function dynamics

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Loop Dynamics - The PID Controller
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Concept 1 Absolute Amplitude Feedback
Vout
Integrate
Input scaling and offset
Output scaling and offset
V4
V5
V1
Amplify
Differentiate
Vin
Set point
PID Dynamics
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Parameter Extraction

• Accept signals from one or more concentration
  sensing sources
• Pre-process the sensor signal as required
• Extract various parameters from the concentration
  sensor as required
• 4. Scale and offset the parameter signals as
  required

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Typical Bubbleogram 512 Samples
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Typical Bubbleogram Descriptive Statistics
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Power Spectral Density
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Autocorrelation
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Current Noise Signal Analysis
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Current Noise Signal
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Current Noise Power Spectral Density
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Current Noise PSD
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Current Noise Autocorrelation Functions
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Current Noise Autocorrelation
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Cross Comparison Bubbleogram vs. Current Noise
- Waveforms
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Waveforms
Bubbleogram
Current Noise
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Cross Comparison Bubbleogram vs. Current Noise
Power Spectral Density
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Power Spectral Density
Bubbleogram
Current Noise
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Cross Comparison Bubbleogram vs. Current Noise
Autocorrelation
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Autocorrelation
Bubbleogram
Current Noise
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System Control Parameter Extraction - Amplitude
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Concept 1 Absolute Amplitude Feedback
Input scaling and offset
V2
V1
Signal Smoothing
Absolute Value
Vout
Vin
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Concept 2 Detrended Abs Amplitude Feedback
mean(V2i V2iN)
V2 median(V1i V1iN)
V3
Mean Estimator
BUset
Bubbles In
BLset
Var(V2i V2iN)
V4
V2
V1
V5 1 if (V4 gt BUset)
Variance Estimator LP Filter
Boundary Alarm Generator
Bubble Detector
Detrender
V6 1 if (V4 lt BLset)
V5
V6
V7 Pu if (V5 1)
Integrator Preset
V2
V1
V8 Pl if (V6 1)
V7
V8
Median Filter
V10
V9
Vset
Integrator
Cell Driver
med(V2i V2iN)
Vout
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The Median Filter
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Concept 2 Bubble Rate Feedback
Input scaling and offset
V2
V1
Differentiator and Limiting Amplifier
Pulse Rate to Amplitude Converter
Vout
Vin
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Cell Driver Block Diagram
Standby Mode Select
DC Power
Vin
Cell Driver Power Amplifier
V6
Vout - Iout
V1
V4
V3
Current Sensor
Input scaling
V8
V2
V5
Standby Controller
Cell Driver Feedback Network
V7
Standby Current Set point
Current Monitor
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Summary and Conclusions
A system concept has been developed and
presented A parameter extraction strategy has
been presented These methods can be used to
extract gas fraction information from gas bubble
sensing devices