Problem Statement:
Quadriplegics are restricted from moving their bodies below the neck. These wheelchair-bound individuals cannot be at eye-level with people with whom they are conversing. Also, they are restricted from being at a proper height when seated at the same table as others. As quadriplegics cannot support their bodies, it takes the extraneous effort of caretakers to move these patients from their seats to another place.
Quadriplegics are restricted from moving their bodies below the neck. These wheelchair-bound individuals cannot be at eye-level with people with whom they are conversing. Also, they are restricted from being at a proper height when seated at the same table as others. As quadriplegics cannot support their bodies, it takes the extraneous effort of caretakers to move these patients from their seats to another place.
Design Goal:
This apparatus will minimize the effort needed to shift quadriplegics from chair to chair in order to be at a necessary height. The chair design consists of a system of gears that move in two different axes (vertical and horizontal about the vertical axis). Because the whole system is designed to move in orthogonal directions, the amount of weight this assembly will be able to carry is limited. It is a matter of concern that the gears and the disks of which the assembly is comprised may have too much friction in between each other and hence, may cause the seat to malfunction. When considering an overload, the seat becoming unattached from the wheelchair is not an issue, since it will be connected with a hydraulic piston. Wear and fatigue on the assembly parts may also cause an issue. Therefore, it is likely that this assembly will need maintenance.
Pre-Existing Solutions:
This apparatus will minimize the effort needed to shift quadriplegics from chair to chair in order to be at a necessary height. The chair design consists of a system of gears that move in two different axes (vertical and horizontal about the vertical axis). Because the whole system is designed to move in orthogonal directions, the amount of weight this assembly will be able to carry is limited. It is a matter of concern that the gears and the disks of which the assembly is comprised may have too much friction in between each other and hence, may cause the seat to malfunction. When considering an overload, the seat becoming unattached from the wheelchair is not an issue, since it will be connected with a hydraulic piston. Wear and fatigue on the assembly parts may also cause an issue. Therefore, it is likely that this assembly will need maintenance.
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| Figure 1: Fully elevated power chair [2] |
One of the mechanisms that has already been created is a power wheelchair that uses a method of propulsion and elevation with electric gear motors. The wheelchair is also controlled by a joystick. The specifications are as follows:
Video 1: Joystick-operated power wheelchair [1]
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| Figure 2: Various applications of power chair [2] |
Operational
Method of Propulsion: 2 - 0.44 HP, 24 VDC electric gearmotors
Method of Elevation: electric gearmotor and screw, switch activated
Rate of Elevation: 1 min. 7 sec. to full extension
Power Supply: 2 - 12 V DC rechargeable batteries
Maximum Speed (seat down): approximately 6.0 mph (9.6 kmh)
(seat up): approximately 1.5 mph (2.4 kmh)
Elevation Range: 22.5 in (57.2 cm)
Braking System: electric motor brakes
Maximum Load/Lifting Capacity: 250 lb (115 kg)
Control System: Penny & Giles VSI Series Wheelchair Control System
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| Figure 3: Model of an elevating wheelchair[2] |
Physical
Overall Height (seat down): 30.0 in (76.2 cm)
Overall Width: 24.0 in (60.7 cm)
Overall Length: 31.0 in (78.7 cm)
Weight: approximately 150 lb (68 kg)
[2]
Power chairs have been capable of being controlled by eye-movement using the EOG process and tools. The algorithms shown below have been used to measure ocular muscle contractions and
convert the signals into mechanical outputs that moved the wheelchair.
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| Figure 4: EOG sensing algorithm [3] |
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| Figure 5: Summary of algorithm [3] |
This wheelchair seat design aims to minimize the effort needed to turn or move the patient towards the needed or desired location. The hydraulic system makes is easy for the patient’s seat to turn about its axis while the entire chassis of the wheelchair stays stationary. This system also easily elevates and descends the patient’s seat to a desired height, when the patient needs to be leveled at a desired location. This eliminates the need to move the patient from his/her seat to another position in such cases.
Project Deliverables:
Over the course of the design project, a power chair will be designed, capable of performing elementary functions such as ascending, descending, and rotating its seat, controlled via the movement of ocular muscles. The wheelchair will be connected to a program, such as MATLAB, which will sense muscle contractions around the eye using a Data Acquisition Sensor. When these muscles contract in specific combinations, the program will turn on and provide an output for the wheelchair's functions such as elevating or rotating.
Project Schedule:
Mechanical Goal
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Electrical Goal
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Week 3
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Research motors, physics of movement, hydraulics systems; order parts and materials
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Research MATLAB programming, EOC readings, eye muscles, thresholds, filtering; order parts and materials
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Week 4
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Design arm for up and down motor; create locking shell; design swivel base
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Read eye movements via sensors and MATLAB
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Week 5
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Mount first swivel base and motor
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Filter “noise;” establish threshold; start code
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Week 6
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Mounts second motor on swivel base
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Final code completed for data input and output
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Week 7
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Combine electrical and mechanical components
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Week 8
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Test and refine final design
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Week 9
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Finalize prototype; final analysis of design
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Projected Budget:
| Price | Shipping | Purchased/provided | ||
| MATERIALS | ||||
| 6 electrodes | $0.00 | drexel | ||
| Bolts/screws/washers | $10.53 | home depot | ||
| PCB Board | $0.00 | drexel | ||
| Swivel base | $10.95 | $15.56 | Merit Industries | |
| CONTROLLERS | ||||
| DAQ | $0.00 | drexel | ||
| MATLAB | $0.00 | drexel | ||
| Amplifier | $0.00 | drexel | ||
| MISCELLANEOUS | ||||
| Swivel chair | $29.00 | walmart | ||
| 36v DC motor | $35.00 | $13.50 | Ebay | |
| Linear actuator | $128.99 | $22.78 | Progressiv eAutomotions | |
| 2 pieces of plywood | $15.26 | home depot | ||
| Wood glue | $2.97 | home depot | ||
| Aluminum sheet | $9.88 | home depot | ||
| Bracket | $7.13 | home depot | ||
| Spur gear | $10.00 | $15.00 | Stock Drive Parts | |
| Timing belt | $16.67 | $10.00 | Stock Drive Parts | |
| 276.38 | 76.84 | |||
TOTAL: $353.22
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