Nelson Research, Inc. 2142 – N. 88 th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com Gas Fraction Control System for a Gas Evolving Electrochemical.

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


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


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


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


Loop Dynamics - The PID Controller


Concept 1 – Absolute Amplitude Feedback

Input scaling andoffset

Amplify

Integrate

Differentiate

Output scaling andoffset

“PID” Dynamics

Vin

V4 V5

Vout

Set point

V1


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


Typical Bubbleogram 512 Samples


Typical Bubbleogram Descriptive Statistics


Power Spectral Density



Autocorrelation



Current Noise Signal Analysis


Current “Noise” Signal


Current “Noise” Power Spectral Density


Current “Noise” PSD


Current “Noise” Autocorrelation Functions


Current “Noise” Autocorrelation


Cross Comparison – Bubbleogram vs. Current Noise - Waveforms


Waveforms

Bubbleogram Current Noise


Cross Comparison – Bubbleogram vs. Current Noise – Power Spectral Density


Power Spectral Density



Cross Comparison – Bubbleogram vs. Current Noise – Autocorrelation


Autocorrelation



System Control Parameter Extraction - Amplitude


Concept 1 – Absolute Amplitude Feedback


Signal Smoothing

Absolute Value

Vin

V2

Vout

V1


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)


The “Median” Filter


Concept 2 – Bubble Rate Feedback


Pulse Rate to Amplitude Converter

Differentiator and Limiting Amplifier

Vin

V2Vout

V1


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


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

Nelson Research, Inc. 2142 – N. 88 th St. Seattle, WA. 98103 USA 206-498-9447 Craigmail @ aol.com Gas Fraction Control System for a Gas Evolving Electrochemical.

Documents

nelson research

required slide

current noise signal

current noise psd slide

pid controller slide

current noise waveforms

current source set point

mode loop dynamics circuit