"All Terrain Wheelchair mechanism"
IIT - Madras, Machine Design Section (May'16 - July'16)

Rehabilitation Research and Device Development Lab (R2D2)
Advisor - Prof. Dr. Sujatha Srinivasan

It is known from geometry that, any three points can form a plane. In a conventional wheelchair, which is 4-wheeled, it can be seen that there are four points of contact with the ground surface. When such a wheelchair is driven on an irregular terrain, all the four wheels rarely make contact with the surface. Since three points make a plane, three wheels of such a wheelchair always remain in contact and the fourth wheel dangling in the air. This causes loss of traction and power and leads to instability in such terrains. This difficulty is overcome by providing only three wheels viz. two large rear wheels and a single front larger castor wheel. Also, to ensure that the Center of Gravity of the user-wheelchair system always lies inside the base area, the wheelbase of the wheelchair is made longer. This ensures high amounts of stability in off-road conditions.

Fabrication Process

Final Prototype

Conclusion

The design was able to achieve the objectives that were set. An initial prototype of the same was made and tested. The wheelchair is unique in the sense that it uses both the front and the rear stroke of the lever to propel the chair thus allowing the user to operate the wheelchair in two ways- either push-pull both levers at the same time(synchronously) or push-pull in alternate fashion(asynchronously). The whole prototype was built within a budget of 2000 INR making it affordable for people in developing countries.

Feel free to reach out to me to discuss about the in-detail ADAMS simulation, MATLAB optimization that was involved.