Transcript Safe Sense Technologies - Simon Fraser University

Shadi A.K Shirazi
Jamie Westell
Arash Jamalian
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Background
Motivation
System Overview
Implementation
Results
Future Develpoment
Business Case
Finances
Final thoughts
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Bone
What is pressure sore?
-Also called decubiti, decubitus
ulcer and bedsores.
Subcutaneous
Soft Tissue
Skin Layer
Stage 1
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What causes pressure sores
after spinal cord injury?
Stage 2
o Decrease in blood circulation
o Lower tolerance for pressure
o lack of sensation
Stage 3
Stage 4
Images c/o www.spinal-injury.net
Ian Denison, Physiotherapist
G.F. Strong Rehabilitaion Centre
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Shoulder
Blade
Pressure Relief System
o The fast development of body sores
o Side effects of sudden blood flow
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Tail
Bone
Back of
Knee
Wheelchair Tipping Stability
o Sudden Muscle Spasm
o Navigating Over Sidewalk Curbs
o Meeting an Immovable Obstacle
o Reaching awkwardly for something
Foot
Sitting
Bone
In 2003,65-80% of 100000 wheelchair related injuries in
US were due to tips and fall
Image c/o www.spinal-injury.net
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Solution
◦ A system which moves the upper body of the user
left and right in a controlled manner.
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Goals
1. Provide Pressure Relief to User
2. Increase Stability of Wheelchair
3. Provide Manual Control to the User
Modes of Operation
Pressure
Relief
Wheelchair
Stability
Joystick
Control
AVR Butterfly Microcontroller
Motor Controller
BACK
AVR Butterfly Microcontroller
Motor Controller
BACK
AVR
Butterfly
Motor Controller
BACK
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User Interface
◦ Mode Switches
◦ Emergency Stop
◦ Power LED
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Switching Between Modes
◦ Priorities
1.
2.
3.
4.
Emergency Stop
Joystick
Wheelchair Stability
Pressure Relief
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Lateral supports
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Current limitation: vertical side bar
Placed on the rails
Chosen to fit the sides of each individual
Better Force Transfer
Aesthetically pleasing
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Customizing
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Acceleration control
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Safety improvements
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User interface
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Mechanical structure
◦ Adjustable pressure relief timing
◦ Manual speed control
◦ Centripetal acceleration
◦ Acceleration dependant motor control
◦ Pressure sensors on the harness/lateral
◦ Muscle Spasm detection
◦ Sip-n-puff (ideal for quadriplegic people)
◦ Appropriate casing
Component
Price
AVR Microcontroller 3
38.85
Rack and Pinion/DC Motor
303.62
H Bridge
160.15
Inclinometer
Linear Encoder
65.91
257.41
12V-Battery
50.40
Circuit Components
50.78
Hardware
(Cases/Pulleys/Glue/etc)
55.65
Chest harness
44.1
Rope (Aluminum rope/Kite rope)
38
Total Product Cost
$1064.87
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Additional Cost = 598.54
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Unused parts
Tools and Equipment
Restocking Fee
Long distance calls and Travel
Additional
Cost
Product
Cost
Actual
Cost
598.54
1064.87
1663.41
Proposed Budget
Actual Budget
$1,603
$1,663.41
Funding:
Engineering Science Student Endowment Fund: $890
Whighton Fund: $900
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Funding -Actual Budget =126.59
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Other uses for system
◦ Manual posture adjustments
◦ Correcting bent spine for eating/breathing
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Incentive for insurance companies
◦ Enhanced safety on sidewalks, trails
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Incentive for physiotherapists
◦ Optimizing the pressure relief to fit individual needs
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Alternative products:
◦ Pressure Relief System:
 Pressure Reduction Cushion
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Tipping Stability System:
◦ Tilt Recliner
 Manual. Not for Quadriplegic injuries
 Can not be used throughout the day
◦ Pneumatic actuators to move the seat
 Very expensive
 Requires a lot of power
January
Task Name
February
March
April
6 | 13 | 20 | 27 | 3 | 10 |17 |24 | 2 | 9 | 16 | 23 | 30
Research
Proposal
Functional Specification
Design Specification
Assembly of Modules
Integration
Documentation/website
Post Mortem
Proposed Timeline
Actual Timeline
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Successful Team
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What we learned
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Excellent Project Management
Excellent Communication
High Interest/Enthusiasm
Appropriate /Reliable Information Sources
Sufficient Technical Knowledge
Hard Work
◦ Technical details of each component
◦ Integration
◦ Implementation of our knowledge obtained from
the past 5 years of education
Ian Denison, Physiotherapist
G.F. Strong Rehabilitaion Centre
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GF Strong Rehabilitation Centre
◦ Ian Denison (Physiotherapist and Equipment Evaluator)
◦ Walt Lawrence (Spine Peer Mentor)
◦ Doug Gayton ( Assistive Technology Practitioner)
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Patrick Leung
Steve Whitmore
Andrew Rawicz
Shahram Payandeh
Carlo Menon
Brad Oldham
Jason Lee
ESSEF
Questions?
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PI Controller
12V DC Motor
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Output Linear Force
Pressure Relief Operating Parameters
Stability Operating Parameters
Stability Sample Calculations
AVR Butterfly
Inclinometer
String Potentiometer
H Bridge
Power
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Challenges
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Integral Wind Up
Proportionality Constants for WSM
A/D Converter
Signal Filtering
(Images and Data c/o amequipment.com)
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Recommended current rating from the supplier: 15 Amps
Radius of the pinion = 0.45 inches = 0.01143 m
Output torque at 15 Amps: 5.7 Nm
Linear output force required (neglecting internal resistance):
Maximum speed of the rack with no load is 11cm/sec (91.9
RPM)
Internal torque 0.5 Nm
Desired Speed = 1 cm/sec
Maximum linear force required : 100 lbs= 444.82 N
Required operating current 13 Amps
The maximum current available for the motor 20 Amps (H-Bridge limitation)
Output torque at 10 Amps : 7.8 Nm
Maximum speed at 7.8 Nm : 40 RPM
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The maximum output force:
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limit on the controllable tipping accelerations depending on the weight of the user
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Maximum Speed of the motor at 5 Amps : 85 RPM
Maximum Speed of the rack
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Atmel AVR Microcontroller
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Very Cheap (~$30)
Helpful Sample Code
RS-232 connection for data
Many peculiarities
 Multiple use pins
 Different versions
 Startup Pin Levels
(Images and Data c/o atmel.com)
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VTI Technologies SCA-61T
◦ Single Axis
◦ Analog Output
(Images and Data c/o vti.fi)
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Celesco SP1-25
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Absolute Encoder
Max. Extension 25in. (62.5 cm)
Analog Ratiometric Output
0 to 5V Output
Application
◦ Only used 12cm of extension
◦ Output range 0 to 1V
◦ ADC 1.1V internal reference
(Images and Data c/o celesco.com)
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Devantech MD03 H Bridge (50V, 20A)
Features:
o Built in charge pump
o Supplying up to 20A of Current to the motor
o Rapid motor current switching which allows PWM control
o Over Temperature protection
o Over current shut down
Supply Voltages
o 5v for the control logic
o 12V motor voltage
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35 Amp-Hour Sealed Lead-Acid Battery
◦ Used for prototype purposes
◦ Supplied by Brunette Battery
(Image and Data c/o batterymart.com)
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Response time
◦ With 62.5 ms: Response time 0.25sec (loaded)
◦ With 15.625 ms: Response time 0.15 sec
◦ At 15.625 ms resolution drops by factor of 4, not
enough memory to compensate for that
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Speed resolution
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Calculating speed by skipping 7 samples
Increases accuracy in the calculation
Better estimate of how fast the speed is changing
Slower velocity control
Rise Time
Overshoot
Settling
Time
Steady State
Error
Kp
Decrease
Increase
Small
Change
Decrease
Ki
Decrease
Increase
Increase
Eliminate
Kd
Small
Change
Decrease
Decrease
Small
Change
Wheelchair Stability & Pressure Relief System