In my Capstone Design project, I let a team of six Mechanical Engineers to create a Manual Wheelchair pushoff assist. We saw a gap in the market for people who needed to be in a wheelchair due to medical issues but could not afford an automatic wheelchair. I was responsible for creating a mechatronic system that allowed for a motor assisted initial pushoff, controlling two motors with an Arduino.
As we designed our device, we conducted a house of quality analysis to come up with the final four criteria our wheelchair had to provide the user.
1. Sufficient and safe energy release to motor
It was important to choose the right components that would store energy safely, and release enough energy to the motors to operate, while interfacing with a controller to respond to user direction.
The tradeoff to consider was how much energy density would be sufficient, but at the same time not unsafe in that components would not heat up and be a safety hazard. We tested our selected design would generate the desired motion in Prototype 1, and throughout all our iterations we have kept a close check on temperature of the components, especially after extensive use. We ended up choosing a lithium battery, paired with a motor shield/Arduino controller.
2. Minimum space and interference
To provide value to the customer, our design had to use as little space as possible and not interfere with regular operation of the wheelchair, which includes its folding and storage capabilities.
3. Minimum input from user
One of our goals was to require minimum control input from the user to operate our device. The touch sensor can be brushed against on the way down to grasping the wheels of the wheelchair, which then triggers the drive wheels to power up and give a push assist to the user.
4. Forward, reverse, turning assist
Success of the torque assist also depended on what functionalities of the wheelchair it could implement, thus assisting users when they want to go in the forward or reverse direction, or need help turning the wheelchair.
In providing a torque assist, it was important to consider that the assist would not be excessive and give more motion than desired in forward and reverse directions, and turning the wheelchair more than the user intended. Testing the user’s satisfaction with the torque assist was done by taking feedback from users of our product. According to results, our product helped them in moving from rest to motion comfortably. In reality, it would be easy to edit the controller to change the force given to the motor, and so our product could be sold at different levels of assistance.
For more information, please review the final poster: