abstract of thesis design of an intelligent optical...

ABSTRACT OF THESIS

DESIGN OF AN INTELLIGENT OPTICAL SENSING PLATFORM

Optical sensors have been developed to measure fluid properties, characterize gel formation in milk for cheese production, and monitor fluid flow in a pipe for transition detection. These analytical devices require real-time computation to analyze data as it is sampled. Use of these sensors in food processing plants currently requires programmable logic controllers to perform the signal analysis. This approach has proven costly as the software solution must be tailored to each plant and trained technical personnel must be onsite for extended periods during the installation. A versatile embedded processor platform was developed to remove the need for the programmable logic controller by fulfilling all the computational requirements for these optical sensors. The capabilities of the developed hardware and software were proven by implementing the transition detection algorithm because of its high processing requirements. Tests of the completed platform were conducted in a pilot plant by presenting the system with transitions between water and 10% sugar in water, 0.5% milk solids in water, and whole milk (3.2% milk fat). The embedded processor platform was able to identify the transitions in 100% of the tests without requiring any adjustments. Results proved that the device is capable of detecting a change in optical density over a range of 0.008 to 3.647 orders of magnitude. KEYWORDS: Embedded System, Microcontroller Applications, Process Control,

Optical Sensing, Fluid Measurement

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By

Garrett David Chandler

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Director of Thesis

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RULES FOR THE USE OF THESES

Unpublished theses submitted for the Master’s degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the thesis in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this thesis for use by its patrons is expected to secure the signature of each user. Name Date ________________________________________________________________________

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THESIS

Garrett Chandler

The Graduate School

University of Kentucky

2006


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THESIS ____________________________

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the College of Engineering at the University of Kentucky

By

Garrett David Chandler

Lexington, Kentucky

Director: Dr. Frederick A. Payne, Professor of Biosystems and Agricultural Engineering

Lexington, Kentucky

2006

Copyright © Garrett D. Chandler

MASTER’S THESIS RELEASE

I authorize the University of Kentucky Libraries to reproduce this thesis in

whole or in part for purposes of research.

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Dedicated to the memory of

Kimbra Leigh Cates

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ACKNOWLEDGEMENTS

There are several individuals I would like to acknowledge and thank for their

contributions to my graduate program.

To begin, many thanks are due to my graduate advisor Dr. Fred Payne. It has been

fantastic to be able to work with you over the past two and a half years in such a

synergistic relationship. You allowed me great freedoms in this project, my graduate

studies, and in the schedule to complete both. Such a grand experience would not have

been possible without your support, cooperation, and encouragement.

It wouldn't be prudent to not also acknowledge Dr. Ronald Lacey of Texas A&M

University. Were it not for you, the chances that I would have continued my studies at the

University of Kentucky after finishing at Texas A&M are likely small. Thank you for

refraining from trying to convince me to stay with you at A&M, for sending me in the

direction of Lexington, and for the opportunity to get my first taste of embedded systems

while working for you.

My "extra-curricular" committee at the University of Kentucky is due many kind

thanks as well; Drs. James Lumpp, Suzanne Smith, Bill Smith, and Jamey Jacob. It was

the opportunity to work for you and with you during the BIG BLUE projects that allowed

my exceptional graduate experience to be elevated to the level of extraordinary. I

multiplied the amount of education that I take away from UK many times over by being

able to work on this grand project.

Friends carried over from my days in Texas and those found here in Kentucky

provided the support and entertainment structure that I needed to make my time here as

enjoyable as it was educational. Devin, the list of things I thank you for is a thesis in

itself. Know that I appreciate you and think that you are the best friend a guy could ever

ask for. Melanie, your list is long as well but above all, thanks for being there during the

lows and highs that life has thrown us over the years. The contributions that you have

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made to my life are both indescribable and immeasurable. Chris, I will never be able to

thank you enough for coming by during my first week at UK and asking me out to happy

hour with you and your crew. You've been my primary source for a social outlet for all

these years and I thank you. And finally, Mike, thanks so much for sharing an office with

me during the time that you have spent here. I will sorely miss the great discussions that

we had on an almost daily basis.

As for my number one fans, no amount of text will ever allow me to acknowledge

my family in a way that comes close to relaying my feelings of indebtedness to them.

Your encouragement, guidance, and love have allowed me to dream and achieve far

beyond the typical limits of life. Thank you and I love you.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS............................................................................................... iii

LIST OF TABLES ........................................................................................................... viii

LIST OF FIGURES............................................................................................................ ix

CHAPTER ONE: INTRODUCTION............................................................................................ 1

OPTICAL SENSOR TECHNOLOGY ...................................................................................... 1

Coagulation Sensor ..................................................................................................... 1 Transition Sensor ........................................................................................................ 2 Composition Sensor .................................................................................................... 3 Spectrum Sensor ......................................................................................................... 3

PROPOSAL........................................................................................................................ 4

JUSTIFICATION ................................................................................................................. 4

Simplicity .................................................................................................................... 4 Digital Measurements ................................................................................................. 5 Dynamic Range........................................................................................................... 5 Multiple Emitters and Detectors ................................................................................. 5 Reprogrammable Processor ........................................................................................ 6 Data Collection ........................................................................................................... 6

OBJECTIVES ..................................................................................................................... 6

CHAPTER TWO: SYSTEM REQUIREMENTS ............................................................................ 7

SYSTEM OVERVIEW ......................................................................................................... 8

PROCESSING CORE......................................................................................................... 10

OPERATOR INTERFACE................................................................................................... 11

TECHNICIAN INTERFACE ................................................................................................ 12

CHAPTER THREE: INTERFACE SELECTION.......................................................................... 13

PLC INTERFACE............................................................................................................. 13

Analog....................................................................................................................... 14 Digital ....................................................................................................................... 16

SERIAL COMMUNICATION.............................................................................................. 17

Data Links................................................................................................................. 18 Transmission Protocol .............................................................................................. 19

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CHAPTER FOUR: EMBEDDED HARDWARE DESIGN ............................................................. 21

PROCESSOR SELECTION ................................................................................................. 21

Processor Setup......................................................................................................... 23 CIRCUIT DESIGN ............................................................................................................ 25

Discrete Components ................................................................................................ 26 Photon Emission ....................................................................................................... 28 Photon Detection....................................................................................................... 32 Event Log.................................................................................................................. 33 Digital Communication............................................................................................. 36 Analog Output........................................................................................................... 38 Digital Input/Output.................................................................................................. 41 Microcontroller ......................................................................................................... 42 Power ........................................................................................................................ 45

CHAPTER FIVE: PROTOTYPE CONSTRUCTION..................................................................... 49

CIRCUIT REVIEW............................................................................................................ 49

CIRCUIT PARTITIONING.................................................................................................. 51

CIRCUIT BOARD LAYOUT .............................................................................................. 54

MANUFACTURING.......................................................................................................... 56

CHAPTER SIX: SOFTWARE SYSTEM .................................................................................... 57

DRIVERS ........................................................................................................................ 58

System Initialization ................................................................................................. 58 Analog to Digital Conversion ................................................................................... 60 Serial Communications ............................................................................................. 61 Digital to Analog Conversion ................................................................................... 64 External Interrupts .................................................................................................... 65 FLASH Memory Access........................................................................................... 65 Peripheral Counter Array .......................................................................................... 67 System Management Bus.......................................................................................... 69 Serial Peripheral Interface......................................................................................... 71 System Timers .......................................................................................................... 72

LIBRARIES...................................................................................................................... 74

System Management ................................................................................................. 74 Time .......................................................................................................................... 75

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Text Display.............................................................................................................. 76 Event Log.................................................................................................................. 76 Transition Algorithm ................................................................................................ 78 Data Storage.............................................................................................................. 79 File Transfer.............................................................................................................. 81

TASKS............................................................................................................................ 82

CHAPTER SEVEN: PLATFORM VERIFICATION ..................................................................... 85

TEST DESIGN ................................................................................................................. 85

TEST RESULTS ............................................................................................................... 87

CHAPTER EIGHT: FUTURE WORK....................................................................................... 91

POWER SUPPLY.............................................................................................................. 91

INTERNAL OSCILLATOR ................................................................................................. 91

MANUFACTURING.......................................................................................................... 92

CIRCUITRY..................................................................................................................... 93

CODE REVIEW................................................................................................................ 94

CHAPTER NINE: CONCLUSION............................................................................................ 95

APPENDIX A: BILL OF MATERIALS..................................................................................... 96

APPENDIX B: POWER BUDGET ......................................................................................... 101

APPENDIX C: CIRCUIT SCHEMATICS ................................................................................ 107

SECTION C1: FULL CIRCUIT......................................................................................... 108

SECTION C2: CIRCUIT ON BOARD 1 ............................................................................. 121



APPENDIX D: CIRCUIT BOARD LAYOUT........................................................................... 143

SECTION D1: CIRCUIT BOARD 1................................................................................... 144



APPENDIX E: TEST RESULTS ............................................................................................ 161

APPENDIX F: SYSTEM IMAGES ......................................................................................... 168

REFERENCES ............................................................................................................... 178

VITA............................................................................................................................... 179

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LIST OF TABLES

Table 1: Photometric specifications for optical sensing algorithms ................................... 7

Table 2: Data storage, input and output requirements for optical sensing algorithms ....... 8

Table 3: Pinout for Silicon Laboratories C8051F123 activated on-chip peripherals ....... 43

Table 4: Pinout for Silicon Laboratories C8051F123 general purpose I/Os .................... 43

Table 5: Summary of statistically generated power requirements.................................... 46

Table 6: Summary of detection results for 18 tests........................................................... 89

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LIST OF FIGURES

Figure 1: Intelligent Optical Sensing Platform block diagram ........................................... 9

Figure 2: Three options for connecting a current loop ..................................................... 15

Figure 3: Typical current mode receiver........................................................................... 16

Figure 4: Representative digital signal receiver................................................................ 17

Figure 5: Photon emitter current driver ............................................................................ 30

Figure 6: Photon detection circuit..................................................................................... 33

Figure 7: Event log circuit ................................................................................................ 36

Figure 8: Serial communication circuit............................................................................. 38

Figure 9: Programmable logic controller analog output circuit........................................ 40

Figure 10: High voltage digital input and output circuit................................................... 42

Figure 11: Processor and supporting circuit ..................................................................... 44

Figure 12: Power supply circuit........................................................................................ 47

Figure 13: Usable surface area given number of boards and board diameter................... 52

Figure 14: Configuration of pilot plant used to test sensor platform................................ 87

Figure 15: Signal and response of 10% sugar in water flowing at 4.5 fps ....................... 88

Figure 16: Signal and response of whole milk flowing at 4.5 fps .................................... 88

CHAPTER ONE

INTRODUCTION

Automation of food processing operations results in decreased waste, increased

food safety, and more homogenous products but requires sensors capable of making real-

time in-situ measurements of the materials during processing. The availability of digital

computational devices in small form factors presents an opportunity to add intelligence to

sensors. This improvement can reduce or eliminate the shortcomings of current systems

as well as open up the possibilities for development of sensors for new applications.

Optical Sensor Technology

The development of optical sensors for food process control has been the focus of

research efforts in the Department of Biosystems and Agricultural Engineering at the

University of Kentucky. Multiple sensors have been designed, all of which require

analytical computations to produce valuable information. The technologies developed

include a coagulation sensor for determining the appropriate cutting time of coagulum in

the cheese making process (Payne et al, 1993), a transition sensor to detect the interface

between two fluids flowing in a pipe (Danao et al, 2003), and a composition sensor that

measures the amount of fat in cream (Payne et al, 2003a). In addition to the developed

technologies, a spectrum sensor has also been envisioned. These four sensors have

similar optical designs and output requirements, thus the development of a single

processing platform to fulfill the computational needs of all sensors is feasible.

Coagulation Sensor

During the process of making hard cheese, cottage cheese, and yogurt products,

enzymes or a microbial culture are added to milk to cause the casein to coagulate and

form larger aggregates. The result of coagulation is the conversion of the liquid milk into

a gel. In the case of hard cheese and cottage cheese the gel is ready to be cut into small

pieces when it has sufficient textural strength. Upon cutting, the coagulum shrinks to

form curd pieces as whey is expressed from the coagulum in the syneresis process. The

time between the addition of the enzyme and the appropriate time for the cut varies

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significantly between batches. There is an optimum time to cut the curd that minimizes

loss and maximizes product quality. A similar optimum time between the addition of the

culture and the point at which the temperature is reduced to stop microbial growth exists

for yogurt products.

Research has found that the aggregation of casein during the coagulation process

can be followed by measuring light backscatter at 880 nm (Payne et al, 1993). The

consistent backscatter response pattern can be analyzed by taking first and second

derivatives to determine time events that, with a regression based model, can be used to

predict cutting time. This prediction method is the same for hard cheese, cottage cheese,

and yogurt.

The determination of the cutting time of these products is currently performed by

subjective human observation. Automation of this phase of the coagulation process will

increase product quality and decrease losses.

Transition Sensor

A transition sensor determines a change from one product to another in a food

piping system. Transition sensors can be used to detect product-to-water or product-to-

product interfaces for a variety of different liquid food products (Danao et al, 2003). For

either product-to-product or product-to-water transitions, the information can be used to

inform the plant operators of a change in pipe flow contents or to automatically sequence

valves.

There are optical sensors available commercially that can determine the

transitions by means of simple reflectance or transmission measurements. However, all of

these require calibration and provide limited performance for applications where multiple

products are processed, such as dairy products, fruit juices, and vegetable juices. A novel

sensor has been developed at the University of Kentucky that eliminates the need for

plant calibration and determines the transition between any two products having as little

as a 5% difference in an optical measurement.

Product losses in continuous processing operations can be reduced by using a

transition sensor to detect the interface region between differing fluids. A reduction in

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wasted product is achieved though higher temporal switching resolution and a decreased

opportunity for accidental product contamination.

Composition Sensor

Light is diffused by scattering as it interacts with a particle within a fluid. The

intensity of backscattered light decreases as distance from the point source increases

according to absorption and scattering principles. Two optical fibers placed at different

radial distances can be used to measure this light intensity difference. The ratio of these

signals is proportional to the light extinction coefficient.

It has been shown that the relationship between the light intensity ratio between

the two collection radii and the milkfat content can be approximated using a linear

equation (Payne et al, 2001). The fat composition in cream, when between 20% and 40%,

can be accurately measured using light with a wavelength of 470 nm or 528 nm. Light

with a wavelength of 470 nm has been shown to be more responsive because the

extinction coefficient for this wavelength is greater than that for 528 nm (Payne et al,

2003a).

The composition sensor may have several applications in the dairy,

pharmaceutical, and biotechnology industries where a sensor is required to monitor and

control composition. One application for the composition sensor is the control of the

separator in the milk processing. An inline sensor capable of measuring the milkfat

content of creams would allow the cream separation process to be automated.

Spectrum Sensor

A proposed sensor concept to analyze multiple light frequency bands in unison is

currently under development. The realization of such a spectrum sensor will only be

made possible through the use of an embedded processor. By sequentially activating each

of four photon emitters with different emission wavelengths and then sampling the

transmission, backscatter and side scatter for each, the ability to create a fluid fingerprint

may be achieved. Accomplishment of this proposed concept will only be possible with an

intelligent system that can control the emitters, collect the response, and process the large

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amounts of data rapidly. Such a system would have nearly universal applicability for food

processing.

Proposal

The advancement of the aforementioned optical sensing technologies into viable

products would be enhanced through the use of an embedded processor. The size and

computational power of reprogrammable electronics available commercially enable the

creation of a custom computing machine that is both small enough to be included in the

sensor housing and feature-rich enough to fulfill the requirements of the previously

detailed applications. The development of an Intelligent Optical Sensing Platform (IOSP)

to meet the computational needs of these sensors is therefore proposed.

Justification

Optical sensing methods developed at the University of Kentucky have been

previously implemented and proven in designs that use only analog components. As a

digital system, the IOSP will remove all dependence on outside computing resources

(programmable logic controllers or personal computers), increase the fidelity of the

sensor system in comparison to the analog version, and allow a single electrical system to

be employed in many sensing scenarios. These improvements will greatly enhance both

the research and commercial potential of the technologies.

Simplicity

Placing computing resources within the sensor housing will eliminate all

dependence on external computing. Previously, the coagulation and composition sensors

yielded an analog output and required either a personal computer (PC) or programmable

logic controller (PLC) to perform the signal analysis. The use of a PLC limits and

complicates data collection and requires algorithms coded and tested in a function-based

language to be converted into ladder logic, a time consuming task. Additionally, the tools

and language used for PLC programming differs between manufacturers and thus

customized software solutions are required for each sensor installation. Overall, the

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technical overhead required to install and maintain the sensing algorithms on these PLC

systems is very costly.

Digital Measurements

Optical sensors previously developed in the laboratory used the TSL250R analog

detector (TAOS, 800 North Jupiter Road, Suite 205, Plano, TX 75074). A digital version

of this detector is available that creates a frequency modulated output. The TSL245R

emits a 50% duty cycle pulse train with a frequency proportional to the light intensity.

The use of an embedded processor in conjunction with this sensor will enable optical

response to be measured with much greater acuity than is currently possible with the

analog sensor. By using the digital optical detector, the signal distance and transmission

stages through which the optical response must pass as an analog signal are eliminated,

removing opportunities for noise to become coupled into the signal. Additionally, greater

resolution than nominal PLC or PC analog receivers provide can be achieved by using

hardware to measure the pulse-width of the detector output at extremely high speed.

Dynamic Range

The range in which analog components can operate optimally is relatively narrow.

Although the center point of this range can be shifted to detect light at low levels or to

detect intense light, the nature of silicon amplifiers restricts the total width of the static

response considerably. The use of a digital system greatly expands the dynamic range

through the improved capture capabilities of hardware. The detection range of the sensor

system can also be improved though the automatic alteration of the light intensity

radiating from the emitter as the sensor is in use, thus increasing the flexibility of the

sensor.

Multiple Emitters and Detectors

The ability to discretely control multiple emitters creates many opportunities for

the development of advanced optical sensing algorithms. Photon emitters that create

different wavelengths of light can be used simultaneously in a single sensor, emitters

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producing the same wavelength of light can enter the fluid at different angles, or a

mixture of these two options can be achieved.

Similar to the opportunities that multiple angles of photon emission offer, the use

of a microprocessor will allow for simultaneous sampling of multiple detectors. When

arranged to sense the backscatter, side scatter, and transmission in unison, more advanced

sensing algorithms can be developed and employed.

Reprogrammable Processor

Unlike the analog circuits it proposes to replace, the reprogrammable nature of the

IOSP enables this single system to be used to serve any optical sensing need. With this

asset algorithms for any number of sensing strategies can then be created, developed,

tested, and deployed on a single hardware setup. It is the use of reprogrammable

electronics that will enable a single hardware design to be used in multiple sensing

scenarios.

Data Collection

The analog sensors previously developed do not provide a means for collecting

data. The calibration of cutting time prediction models requires data from at least 10 and

preferably 30 runs. This data is difficult to obtain from a PLC as was discussed

previously. The ability to store this data within the sensor system would provide a simple

and uniform means for obtaining the information to calibrate the sensors once installed as

well to diagnose any problems that should occur in the plant.

Objectives

The purpose of this research is to develop an Intelligent Optical Sensing Platform

(IOSP) with sufficient computational power, data storage, and programming flexibility to

meet the needs of the aforementioned sensor technologies and provide sufficient

flexibility that it may be applied to future similar sensor technologies. To achieve the

goal of proving this concept the system requirements must be defined, the computing

system designed, a prototype constructed, the firmware architecture developed, the code

created, and an intensive test of the system conducted.

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CHAPTER NINE

CONCLUSION

The sensing platform designed and constructed is an extremely capable device.

Formal tests show that the detection of as little as a 0.05% difference in optical density is

possible. That ability paired with a dynamic sensing range of four and a half orders of

magnitude will allow the system to be used in many scenarios out of the reach of current

sensors on the market today. Processing power and storage space are ample as well. The

software system developed leaves room to store more than 25,000 detector samples

within the device. Even with a processing intensive algorithm using unoptomized code

and floating point math inserted into the system less than 15% of the available processor

time is consumed.

The creation of such a system was achieved by first meeting each of the

objectives of this research project. Great care was taken to properly define the system

requirements so that the system built to these specifications would be capable of

addressing current optical sensing needs and likely be able to handle future applications.

Integrated circuits and discrete electronic devices were selected and composed into a

unified circuit to meet the specifications set forth in the system requirements

documentation. This circuit was laid onto three circuit boards and populated to construct

a prototype. Hardware in hand, three layers of interoperating firmware and software were

created to drive the input and output devices, carry out the prescribed algorithm, and

facilitate the testing of the entire IOSP system. Finally, a test was conducted using the

most intensive algorithm currently developed to prove the functionality of the system.

Throughout testing and evaluation the Intelligent Optical Sensing Platform proved

to be extremely capable. The finding that the system can handle many more computations

per unit time than are currently required of it bolsters the opinion that the platform shows

great promise in furthering optical sensing research and as a commercially viable

product.

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APPENDIX F

System Images

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REFERENCES

ANSI/IEEE Standard IEEE-1149.1-1990. Test Access Port and Boundary-Scan

Architecture Description. IEEE. Piscataway, NJ. 1990.

Barnes, John R. 2004. Robust Electronic Design Reference Book Volume 1. Kluwer

Academic Publishers.

C&D Technologies. 2004. Application Note 51. DC-DC Converters.

http://www.ratelco.com/products/appnotes/dcan51.pdf

Danao, M.C. and F.A. Payne. 2003. Determining product transitions in a liquid piping

system using a transmission sensor. Transactions of the ASAE. 46(2):415-421.

Intel Corporation. System Management Bus Specification.

http://www.smbus.org/specs/smb10.pdf. 1995 [cited 2005 Dec 16].

Payne, F.A., C.L. Hicks, and S. Pao-Sheng. 1993. Predicting optimal cutting time of

coagulating milk using diffuse reflectance. pp76:48-61.

Payne, F.A., K. Gillette, C.L. Crofcheck. 2001. Milk fat determination by measurement

of light backscatter distribution using fiber optics. 2001 ASAE International

Meeting. Paper No. 016030. ASAE, St. Joseph, MI 49085.

Payne, F.A. and G. Danao. 2003. Measuring Particulate Concentration with a Fiber Optic

Light Extinction Sensor. 2003 ASAE International Meeting. Paper No. 036163.

ASAE, St. Joseph, MI 49085.

Payne, F.A. and G. Danao. 2003. Method for the Detection of Product Transitions in

Liquid Piping Systems. U.S. Patent Application S.N. 10/440,383. Filed July 28,

2003.

Payne, F.A. 2005. Personal communications with F.A. Payne, Biosystems Engineer.

Biosystems and Agricultural Engineering Department, University of Kentucky,

Lexington, KY.

TIA/EIA Standard TIA/EIA-232-F. Interface Between Data Terminal Equipment and

Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange.

Electronic Industries Association. Washington, DC. 1997.

TIA/EIA Standard TIA/EIA-422-B. Electrical Characteristics of Balanced Digital

Interface Circuits. Electronic Industries Association. Washington, DC. 1994.

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VITA

Vital Information

Name: Garrett David Chandler Birthplace: Tyler, Texas Birthdate: April 1, 1980 Professional Preparation B.S.A.E. Texas A&M University Agricultural Engineering 2003 Appointments Summer 2005. Norges Teknisk-Naturvitenskapelige University. Trondheim, Norway. 2002 – 2003. Texas A&M University/NASA. College Station, Texas. Summer 2001. New Holland Inc. New Holland, Pennsylvania. Summer 2000. CASE Corporation. Burr Ridge, Illinois. Major Professional Accomplishments Graduated Cum Laude from Texas A&M University, 2003. Awarded the College of Agriculture Senior Merit Award, 2003. Awarded Gamma Sigma Delta Outstanding Senior in Agricultural Engineering, 2003. Inducted into Alpha Zeta Honor Fraternity, 2003. Inducted into Alpha Epsilon Agricultural Engineering Honor Society, 2003. Inducted into Golden Key Honor Society, 2002. Served as ASAE International Preprofessional 2nd Vice President, 2002 – 2003. Served as ASAE Southern Region President, 2001 – 2002. Served as ASAE Texas A&M Preprofessional Branch President, 2001 – 2002. Served as Texas A&M Preprofessional Branch Philanthropy Chair, 2000 – 2001.

Publications Chandler, G.D., et al. “Wireless Extension of an Avionics Bus for Prototyping and Testing Reconfigurable UAVs.” AIAA Infotech@Aerospace Conference. Arlington, Virginia. September 2005. Rawashdeh, O.A., Chandler, G.D., et al. “A Dynamically Reconfiguring Avionics Architecture for UAVs.” AIAA Infotech@Aerospace Conference. Arlington, Virginia. September 2005. Jackson, D.K., Chandler, G.D., et al. “Evolution of an Avionics System for a High-Altitude UAV.” AIAA Infotech@Aerospace Conference. Arlington, Virginia. September 2005. Rawashdeh, O.A., Chandler, G.D., and Lumpp, Jr., J.E., “A UAV test and Development Environment Based on Dynamic System Reconfiguration,” Workshop on Architecting Dependable Systems. St. Louis, Missouri. May 2005. Chandler, G.D., et al. "A Low-Cost Control System for a High-Altitude UAV." IEEE Aerospace Conference. Big Sky, Montana. March 2005.

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