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Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Gas Fraction Control System
for a
Gas Evolving Electrochemical Reactor
Craig E. Nelson - Consultant Engineer
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Reactor Controller Functional Diagram
Block Diagram for “Bubbleostatic” Operating Mode
-LoopDynamicsCircuit
StandbyCurrentSource
Set Point
+Counter – Anode – Ec – Red
Working – Cathode – EwBlue-Green
Cathodic (“Negative”) current
Bubble
Electric“Eyes”
SensorSupportCircuit
ParameterExtractionCircuit
VoltageControlledPowerSupply
Standby
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Reactor Control System Block Diagram
BubbleDetectorSupportCircuit
Signal SmoothingCircuit
ParameterExtractionCircuit
LoopDynamicsCircuit
VoltageControlledCurrentSource
“PID” Loop DynamicsPhotons
V2 V3 V4 V5
Iout
ControllerSet point
V1
Parameter ExtractionDetection StandbyCurrentSource
I1
I2Standby
Det1 Det2
Current DriversPowerSupply
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
1. Controller should provide at least a second order transfer function
2. Controller should provide easy adjustability of the transfer function dynamics
Requirements - Loop Dynamics
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Loop Dynamics - The PID Controller
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Concept 1 – Absolute Amplitude Feedback
Input scaling andoffset
Amplify
Integrate
Differentiate
Output scaling andoffset
“PID” Dynamics
Vin
V4 V5
Vout
Set point
V1
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Parameter Extraction
1. Accept signals from one or more concentration sensing sources
2. Pre-process the sensor signal as required
3. Extract various parameters from the concentration sensor as required
4. Scale and offset the parameter signals as required
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Typical Bubbleogram 512 Samples
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Typical Bubbleogram Descriptive Statistics
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Power Spectral Density
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Autocorrelation
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current Noise Signal Analysis
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current “Noise” Signal
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current “Noise” Power Spectral Density
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current “Noise” PSD
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current “Noise” Autocorrelation Functions
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Current “Noise” Autocorrelation
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Cross Comparison – Bubbleogram vs. Current Noise - Waveforms
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Waveforms
Bubbleogram Current Noise
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Cross Comparison – Bubbleogram vs. Current Noise – Power Spectral Density
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Power Spectral Density
Bubbleogram Current Noise
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Cross Comparison – Bubbleogram vs. Current Noise – Autocorrelation
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Autocorrelation
Bubbleogram Current Noise
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
System Control Parameter Extraction - Amplitude
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Concept 1 – Absolute Amplitude Feedback
Input scaling andoffset
Signal Smoothing
Absolute Value
Vin
V2
Vout
V1
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Concept 2 – Detrended Abs Amplitude Feedback
Bubble Detector
VarianceEstimator + LP Filter
Detrender
BubblesIn
V2
Vout
V1 BoundaryAlarmGenerator
IntegratorV10V9
Integrator Preset
Mean Estimator
Cell Driver
Vset
V4
V3
V7
V5
V2
Median Filter
V1
V2 = median(V1i … V1i+N)mean(V2i …V2i+N)
Var(V2i …V2i+N)
V6
BUsetBLset
V8
V5 = 1 if (V4 > BUset)
V6 = 1 if (V4 < BLset)
V7 = Pu if (V5 =1)
V8 = Pl if (V6 =1)
med(V2i …V2i+N)
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
The “Median” Filter
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Concept 2 – Bubble Rate Feedback
Input scaling andoffset
Pulse Rate to Amplitude Converter
Differentiator and Limiting Amplifier
Vin
V2Vout
V1
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
Cell Driver – Block Diagram
Input scaling
Cell DriverPower Amplifier
StandbyController
Vin V6 Vout - Iout
Standby Current Set point
V1 CurrentSensor
V4V3
V2
V8
V7
Cell DriverFeedbackNetwork
DC Power
V5
Standby Mode Select
Current Monitor
Nelson Research, Inc. 2142 – N. 88th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com
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