Abstract
The disabled usually utilize wheelchairs for their daily mobility and locomotion. These motorized vehicles can travel on relatively flat surfaces or tracks without any problems, but moving up and down the stairs is always a challenge for most commercial wheelchairs. In other words, a person with a disability cannot go anywhere inside a multistory building, shopping store, subway, etc. if they are not built according to accessibility codes. A versatile wheelchair with the ability to negotiate stairs not only improves the daily lives of people with disability, but it can also save their lives in the event of an emergency which requiring immediate evacuation of a building. This article proposes two novel designs to facilitate the stair-climbing feature for a motorized wheelchair. One of the design concepts is based on a curved-spoke mechanism with transformation capability from a round wheel to a tri-leg mechanism to facilitate the translation mode as well as the stair-climbing mode of a wheelchair. The next design concept is an enhanced tri-wheel mechanism using a combination of a tri-wheel setup and planetary gears, to provide a unique capability for the climbing mechanism. After analysis and considering the pros and cons of each design concept, the tri-wheel planetary mechanism has been selected for making a scaled-down model and testing the transmission system on the stairs. The scaled-down prototype can successfully move up or down the stairs in the climbing mode and travel on flat or inclined surfaces in the translation mode.
