Shadi A.K Shirazi Jamie Westell Arash Jamalian Background Motivation System Overview Implementation Results Future Develpoment Business Case Finances
Final thoughts Bone What is pressure sore? -Also called decubiti, decubitus ulcer and bedsores. Subcutaneous
Soft Tissue Skin Layer Stage 1 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
Pressure Relief System Shoulder Blade o The fast development of body sores o Side effects of sudden blood flow Tail Back of Knee
Bone 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 Solution A system which moves the upper body of the user left and right in a controlled manner.
Goals 1.Provide Pressure Relief to User 2.Increase Stability of Wheelchair 3.Provide Manual Control to the User Modes of Operation Pressure Relief
Wheelch air Stability Joystick Control AVR Butterfly Microcontroller Motor Controller BACK
AVR Butterfly Microcontroller Motor Controller BACK AVR Butterfly Motor Controller
BACK User Interface Mode Switches Emergency Stop Power LED Switching Between Modes
Priorities 1. 2. 3. 4. Emergency Stop Joystick Wheelchair Stability Pressure Relief
Lateral supports Current limitation: vertical side bar Placed on the rails Chosen to fit the sides of each individual Better Force Transfer Aesthetically pleasing Customizing
Adjustable pressure relief timing Manual speed control Acceleration control Centripetal acceleration Acceleration dependant motor control
Safety improvements Pressure sensors on the harness/lateral Muscle Spasm detection User interface Sip-n-puff (ideal for quadriplegic people)
Mechanical structure Appropriate casing Component AVR Microcontroller 3 Price 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 Rope (Aluminum rope/Kite rope) Total Product Cost 44.1 38 $1064.87
Additional Cost = 598.54 Unused parts Tools and Equipment Restocking Fee Long distance calls and Travel Proposed Budget Actual Budget $1,603 $1,663.41
Funding: Engineering Science Student Endowment Fund: $890 Whighton Fund: $900 Funding -Actual Budget =126.59 Other uses for system
Manual posture adjustments Correcting bent spine for eating/breathing Incentive for insurance companies Enhanced safety on sidewalks, trails Incentive for physiotherapists Optimizing the pressure relief to fit individual needs
Alternative products: Pressure Relief System: Pressure Reduction Cushion 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 Successful Team Excellent Project Management Excellent Communication High Interest/Enthusiasm
Appropriate /Reliable Information Sources Sufficient Technical Knowledge Hard Work What we learned 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 GF Strong Rehabilitation Centre Ian Denison (Physiotherapist and Equipment Evaluator) Walt Lawrence (Spine Peer Mentor) Doug Gayton ( Assistive Technology Practitioner)
Patrick Leung Steve Whitmore Andrew Rawicz Shahram Payandeh
Carlo Menon Brad Oldham Jason Lee ESSEF Questions? PI Controller 12V DC Motor Output Linear Force
Pressure Relief Operating Parameters Stability Operating Parameters Stability Sample Calculations AVR Butterfly Inclinometer String Potentiometer H Bridge Power
Challenges Integral Wind Up Proportionality Constants for WSM A/D Converter Signal Filtering (Images and Data c/o amequipment.com)
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 The maximum output force:
limit on the controllable tipping accelerations depending on the weight of the user Maximum Speed of the motor at 5 Amps : 85 RPM Maximum Speed of the rack Atmel AVR Microcontroller
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)
VTI Technologies SCA-61T Single Axis Analog Output (Images and Data c/o vti.fi) Celesco SP1-25 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)
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 35 Amp-Hour Sealed Lead-Acid Battery Used for prototype purposes Supplied by Brunette Battery (Image and Data c/o batterymart.com)
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 Speed resolution 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
