The main goal of the design is to assist wheelchair users on inclines and declines. As stated above in the motivation section of the report, the goal of the attachment is to allow wheelchair users to gain independence and struggle less when ascending and descending steep slopes. Specific design objectives have been generated that will assist in achieving this overall goal. The most important functions of the device are to measure the effort/input of the wheelchair user, apply both positive and negative torque, control the direction of the wheelchair, and allow for folding/interfacing with common wheelchairs. Table 2 is a morphology chart that lists various options of how these important functions can be achieved.
Table 2 Morphology Chart
| Eliminate Jerk | Measure Effort/Input | Apply Positive Torque | Apply Negative Torque | Control Direction | Allow folding/interfacing with common wheelchairs |
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The device should be able to apply both positive and negative torque in order to control both speeding up and slowing down the wheelchair. Measuring the effort of the user is one of the main goals of the design process. As stated above, many users struggle with inclines and declines and using their wheelchair for prolonged periods. By utilizing the effort of the user as an input, this creates the ability to reduce the strain wheelchair users face. The torque and effort inputs from the user are both significant measurements for the device. As seen in Table 2, the add-on will include a knob to enable the user to control the speed of assistance outputted from the device. Additionally, there will be a joystick to enable the user to control the direction of the wheelchair.
Conceptual designs, which were generated by individual members of the team, were created by considering the design objectives (See Images and Videos). Some concepts are full designs, while others focus on the placement of various sensors and components of the system. Many of the designs came from considering the design objectives listed above; however, not all objectives were satisfied with each design. For example, a couple of designs did not allow for the wheelchair to fold with the attachment on the wheelchair. The importance of this feature will be determined through survey and interview feedback the team obtains. Designs also came from researching the prior art. This large compilation of ideas has allowed the team to narrow the scope and identify the most effective motor assistive device while taking into consideration cost, weight, and other considerations. After examining the initial conceptual designs, the team identified that the project will be composed of three decoupled subsystems: the motors and transmission, the controls, and effort sensing. The subsystems will be integrated, but designed separately due to the fact there is a weak coupling between the different subsystems. The major subsystem identified is the motor and transmission, so the team further considered how they could achieve this subsystem. These considerations can be found in Table 3.
Table 3 Drivetrain function/means and other considerations
| Motor Types | Transmission | Apply Negative Torque |
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More About the Planned Approach: