nelson research, inc. 2142 – n. 88 th 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

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