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Wayne ChenGavin WuKyuho ChaEdward Chan
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Overview
Background Motivation Our Solution System Overview Future Development Business Case Finances Final Thoughts
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Background
- Estimated annual SCI is approximately 12,000 new cases each year.
Spinal Cord Injury (SCI) Study- In 2007, approximately 225,702 people suffer from SCI
Types of Disability & Proportions- 34.1% incomplete tetraplegic (weak control over upper & lower body muscles)
- 23% are complete paraplegic (no control over lower body movement)- 18.5% are incomplete paraplegic (weak lower body movement)
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Design MotivationAllow Better Blood Flow Circulation
Height Control System
- Beneficial for the muscles and blood flow
- Allow user to have equal eye level communication.
- Increase range of height, ease of access to shelf top, switches… etc.
- Relieve pressure and stress from buttocks area.
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Our SolutionInnovative, Reliable & Cost Effective Device- A system that can be retrofitted on to existing
power wheelchair designs and be able to transfer an user effortlessly from a sitting to a standing position.
Goals- Safe and secure transfer for the user
- Manual button controls for user
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System Overview
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System Overview
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Button ControlsTactile switch buttons
Up
Down
Memory
Stop
-Up, Stop, Down, Memory
-sitting to standing trasistion
-standing to sitting transistion
-stop all transition
-memorizes the current position
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Mainboard
Butterfly
Motor control
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Tilt Sensor/Accelerometer
Bottom of the seatDetects the angle between the frame and the seat.Allows the micro-controller to monitor the position of the seat.
Sensor
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Mechanical DesignLinear Actuators
- Controls the bottom and top frame movement.
Light-weight Aluminum Frame
- Allows minimum change to actual wheelchair.
-Strong and secure foundation for user.
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Trajectory of Motion
- 70 Degrees incline- Users have weak joints that does not allow for max movement
- Movement range changes with the mounting position/size of the actuators
Final Position
Customizable Trajectory
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Safety ComponentsUpper Body Harness/Seat belt
-Prevents user from falling forward.
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Safety ComponentsLeg Supports
- Keeps the leg in place so that the person is kept from sliding forward.
- Cushion for knee area support.
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Future Development
- Control both actuator at the same time.- Put a safety function to detect interference of actuator motion.
- Attach higher quality safety harness to improve comfort and safety.- Improve visual appeal and design of frame and components
- Sip –n-puff (ideal for quadriplegic people).
- Customize frame to fit the needs of various body type. - Use different size actuators to control the trajectory of the frame.
Actuator Control
Enhanced Safety, Comfort & Appeal
User Interface
Customizable
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Project Finances
ITEM Cost
Electronic Components
Total $475.04
Metals
Total $144.87
Bolts/Misc Components
Total $146.79
Fabrication
Total $1780.80
Sub Total $2547.50
Prototype Production Cost Prototype FundingWighton Engineering Development Fund
Cover all prototype costs
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Actual CostsProduct Cost
-Fabrication costs were a major portion of our project budget. If mass production occurs, partnership can be made with fabrication shop and may be able to lower a large portion of the project costs.
Unused Parts- Extra and additional parts were sourced in for quick replacement if parts are damaged along the testing phases.
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Competition
- High Cost $30,000 - $40,000 - Built as all-in-one unit - Able to select the features you want for customization
- No mobility - Separate unit - Large and bulky (Robust)
C500vs Series
EasyStand Ovation Strap Stand
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Business Opportunities
- Assist with standing process for people with weaker leg strength.- Transfer the user to a position suitable for urination
- Not all disabled people have the same needs. - Minimize cost by reuse/upgrade existing wheelchair. - Could become a part of rehabilitation process. - Allow better blood flow to the legs - Decrease work load for nurses/doctors to stand a person up.
Possible Usage
Incentives
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Timeline
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Acknowledgements
GF Strong Rehabilitation Center- Ian Denison (Physiotherapist)
- Charles Martin (Wheelchair Technician)
Peter Borwein
Patrick Leung Jason Lee Jamie Westell Andrew Rawicz Steve Whitmore Carlo Menon
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Conclusion
What We Learned- Mechanical system design and fabrication.- Technical knowledge of different components- Integration techniques of mechanical and electronic components.
- Team environment and management.
Successful Completion of GoalsScheduled Deadline
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Questions?
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Motor ControllerSoftware: Main Function Flow ChartSoftware: Timer ISRMain BoardAVR ButterflyTilt SensorSensor Circuitry – 1Sensor Circuitry -2Max Weight CalculationsAluminumFabricationTechnical Drawings
Technical Information
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Vcc: 12VLogic one from butterfly : 3.3V
β of the npn: 100Ic =xxmA
Ib = Ic/ βR1 = (3.3-0.7)/IbR1 = (3.3-0.7)/Ib
Relay Coil:12V75mA160 ohms
Absolute maximum for transistor:200mA
Motor controller
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Software: Main Function Flow Chart
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Software: Timer ISR
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MainboardComponents- Protection
- Fuses
- Voltage regulators- 3.3V (butter) 5V (sensor)
- Debug- LEDs
- Relay- Actuator control
- Butterfly- Sensor input
- Bottom tilt sensor
Back
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Butterfly
Operating voltage- 2.7V to 5.5V (we chose 3.3V)
Supply current- 2.3mA to 4mA
CPU speed- 8MHz, factory set by software to 2MHz to save button battery life.
ADC- 10-bit (0-3.3V ADC range)
- Changed reference voltage to 1.1 to increase ADC sensitivity
Timer- 16-bit timer counter with 64 prescaler
- Timer interrupt is set to 0.08s Back
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Butterfly I/O- PortB, PortD, JTAG/PortF (ADC)
- PortB used for button control and bottom actuator control
- PortD used for LEDs to output current stage for debugging purposes, PortD also used for controlling back actuator
Temperature range - (-40C to 85C)
LCD- PortD, turned off to avoid conflict between output function and LCD
display
Absolute maximum ratings- Operating voltage, 6.0V
- DC current per I/O pin 40.0mA
- DC current Vcc and GND pins 200.0mA
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Tilt sensor/AccelerometerOperating voltage- 4.75V to 5.25V
Single Axis- Z axis
Sensitivity- 750mV/g
- 2.5g sensing range
Temperature range- (- 40C) to (105C)
Supply current- 1.1 to 3mA
Self protection mechanism- 2kV ESD protection circuitry Back
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Sensor Circuitry-1
Vss
Vss
Vss
Vss
Vdd
Vout
Sensor
Ro
C2
C1
Sensor output
5V
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Sensor Circuitry-2
Rf = 2.2 KohmRa = 1 KohmR1 = 1 KohmS = 1Rs = 2.2 KohmRx = 3.7 KohmRy = 1.3 Kohm
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Max User Weight
Component Weight Position
Battery (x2) 45.89 Kg A
Motor 9.07 Kg A
User X Kg B
Force at Position A = (45.89 Kg + 9.07 Kg)* 9.81m/s^2 = 539.16 NMoment from Weight at Position A = 539.16N * 82 = 44210.92
Limitation Force at Position B = 44210.92/30 = 1473.70Max Weight at Position B = 150.22 Kg
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Aluminum
CheapEasy to machineWeather resistanceLow density compared to other metals- Density, 2.70 g·cm−3
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Fabrication
Out sourced fabricationPrecise fabrication
-CNC, Milling machine, on site welding
Bought own materials-1 1/4 inch square aluminum tubes.
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Technical Drawings Back
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Technical Drawings Back
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Technical Drawings Back
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Technical Drawings Back
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