project11 presentation

8/12/2019 Project11 Presentation

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ALS Breathing andCommunication Suite

By:Alex Kim

Alex ChirbanDonald Ziems


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Project Overview

Amyotrophic Lateral Sclerosis (ALS)Degenerative Neurological Disease

Affects muscle control, voluntary and involuntary includingmuscles involved in respiration

Effects of ALS:o Loss of breathing control leads to eventual asphyxiationo Inability to communicate verballyo Loss of mobility

Proposed solutions: Motorized vest to assist in breathing Eye-tracking suite to enable communication and mobility

o Text-to-speech by means of on-screen keyboardo Mobility by means of on-screen navigation controls


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Currently Available Medical Solutions

Iron Lung Relies on negative pressure to expand and contract lungs Patient confined to device for duration of "treatment" Bulky and expensive Requires wall power

Hayek Smaller and more portable than Iron Lung Uncomfortable due to intense retching from extreme vacuum Also very expensiveMedical Operations Tracheotomy


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Design RequirementsBreathing VestMobile high efficiency negative pressure respiratory devicewhich is more comfortable than available devicesMonitoring of patient's vital signs in order to automatebreathing control as well as integrate the ability to sigh andcoughEye-trackingNon-intrusive system with accurate controlsInterface for user to communicate via text-to-speech and

control wheelchair


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Original Design

4 - piece vest Motors move pieces Pieces press on chest Based on Hayek


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Original Design - Problems

Airtight seal not feasible Extreme mechanical stress Low margin for motion error Uncomfortable Complex mechanics


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New Design

Central plate generates air pressure Single motor operation One moving part Low mechanical stress 3D printed - custom fit


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What We Contributed

Motor Selectiono Mobilityo Breathing

Motor Driver Safety Eye Tracking Pulse Oximeter Power System


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Motors

Stepper motors Dual H-Bridge driver 12V Lead-Acid Batteries for power Lead screw linear actuation Back-EMF slip detection Controlled by Arduino Speed, direction, and distance control Only one motor needed

o Two used to lessen load 70W power consumed


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Safety

Pressure Monitoring Constantly monitors pressure

o Compares to ambient Warning at 1.0 psi

o Sounds audible alarmo Stops motors

Battery Monitoring Constantly monitors voltage Passive components Warning at 50% depletion

o Calibrated to battery voltage under full loadoAudible alarm soundso Non-essential features shut down


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Pulse Oximeter

Development necessitated by lack of

commercial pulse-oximeter option.Design based on traditional pulseoximetry. Two LEDs (Red and IR) pulsed in

alternation Sensor detects intensity of light

transmitted through deoxygenated andoxygenated blood

Blood-oxygen content dependent onrelative intensities of transmitted light

Heart-rate resolved from calculation oftime period between peaks of IRwaveform


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Pulse Oximeter Build

TSL230A Light Intensity to Frequency Converter IC used as

sensor. 940nm IR and 630nm Red LEDs Repurposed potato chip-clip Atmel ATMega328P Processing.org software for interface


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Pulse Oximeter Testing

Tested for accuracy against commercially

available Masimo pulse oximeter.Initial BPM tests found our oximeter to bewithin 10-12 BPM of the Masimo. Initialblood-oxygen content found to vary from15% to 40% of the Masimo.Sensor initially exposed to ambient lightwhich interfered with our readingsAfter manufacture of clip, sensor wasmore isolated and gave us readings ofBPM within 3-5 BPM and blood oxygenwithin 2-4%.


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Mobility Control(Wheelchair unavailable)

Dependent on eye-tracking for control.

On-screen GUI provides user with options to move Forward orReverse, turn Left or Right, and Stop.Design was never implemented due to lack of actual

wheelchair.However eye-tracking control scheme developed as proof ofconcept.


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Inter-module Communication

Arduino I2C library used to communicate between ATMega

uControllers in a Master-Slave relationship.Data processed on laptop sent through serial over USB tomaster uController.Master acts as relay to the two slaves which control the

breathing vest motor uController and wheelchair motoruController.


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Communication Testing

Communication tested from master to each slave

individually as well as to both slaves simultaneously. Control signals monitored on oscilloscope to both devices. Due to lack of wheelchair, LEDs used to simulate output of

transmitted control signals to the wheelchair uController

Vest pump control (both rate and depth of stroke) successfulwith I2C communication from master uController Failsafe included in message encoding in case of

emergency or due to reception of invalid messages


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Eye TrackingPS3 Eye camera with custom lens and

infrared filter

Proper illumination provided by USBpowered IR LED arrayCan be mounted on laptopOpen source software for calibration,text-to-speech, and cursor controlCustom user interface for navigation ofmotorized wheelchairHardware based on low-cost designavailable at http://www.eyewriter.org

Image credit: www.eyewriter.org


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Challenges Power Budget

o

Battery powered systemo Energy efficient design needed

Timelineo Patient needed device sooner than anticipated

Patient Safetyo Have to ensure patient will be safeo Many points of failure to be considered

Unanticipated changes/additions to designo Pulse Oximetero Changes in Motor Controlo Eye-tracking calibration issueso Limitations of uController (communication)


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Successes and FutureRecommendationsSuccesses Pulse Oximeter developed with no background Eye-tracking calibration issues overcome Communication achieved without extra hardware

Motors made to meet specifications of given designparametersRecommendations Clear concept of design is crucial Specifications for design necessary before selection of

parts. Further research of available options for pulse oximeter,

eye-tracking, and emergency systems recommended


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Experiences with InterdisciplinaryDesign Team

Positive experiences: Exposure to real-world design problems outside of ECE

o Part fabricationo Evolution of design

Inter-group collaborationo Multiple perspectives add to robustness of design

Challenges: Communication between groups and team members Differing levels of involvement and commitment between

different teams Different scheduling for different teams ECE team underrepresented in weekly group meetings Out-of-scope expectations


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Questions?

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