Scott Daigle, a graduate engineering student at the University of Illinois, looked at the wheelchair, then at the bicycle, and then back at the wheelchair and asked "Why not a gear system on a wheelchair?" Then he built one.
Called IntelliWheels AGS, this wheelchair shifting system brings the convenience that cyclists have enjoyed for many, many years and applies it to the venerable 1:1 speed ratio found on a manually operated wheelchair.
Unlike the 10-speed bicycle, however, IntelliWheels is an automated system that responds to how the wheelchair is being pushed by the user and responds by shifting to maximize performance:
Sensors on the bottom of the wheelchair analyse torque, speed and tilt to detect how hard the wheelchair user is pushing, how fast they are going and what kind of slope they are on to select the best gear for the job.
The system is designed especially for hill climbing, but the best feature is perhaps the fact that it is automatic: Users need not learn any new tricks or modify their behaviour in any way.
A working, real-world prototype could be in use by September 2012. In the meantime, Daigle and his team are using testing units to simulate three years of use and gauge endurance in the lab. [Futurity via Gizmag]