Optimized Handle-Based Device for Continuous Wheelchair Propulsion

Worldwide, more than 131 million people require a wheelchair for enhancing personal mobility and activities of daily life. The push-rim is the most common method for manual wheelchair propulsion, characterized by low mechanical efficiency of around 10%. Long-term wheelchair users often suffer from joint injuries, especially at the wrist and shoulder joints. This causes further limitations in their independent life and may increase expenses in health care systems. To compensate for these disadvantages a novel handle based wheelchair propulsion device with an optimized continuous movement shape was developed by TU Wien. The continuous movement allows applying propulsion forces over the whole rotation cycle, thus increasing mechanical efficiency compared to standard push-rim propulsion. Hence, joint excursions and joint loads are significantly smaller. Especially longtime wheelchair users, who are often suffering from joint injuries, can benefit from the novel handle based propulsion mechanism, which is an attractive alternative to standard push-rim propulsion. The novel propulsion mechanism is mounted on a standard wheelchair on both sides in the same planes as the wheels and is easily adaptable to individual body sizes. The handle is attached to a crank, which is able to change its length to follow the optimized path. The torque generated in the crank center is transferred to the back wheels via timing belts with a gear ratio of 3:2. Its compact design makes the novel propulsion system suitable for daily in- and outdoor use.