Making a wheelchair that can deal with steps and other obstacles has puzzled engineers for decades, with everything from tank treads to spokes tried and found not quite practical. Now a team of engineers from the Chiba Institute of Technology, led by associate professor Shuro Nakajima, have applied a bit of lateral thinking. They have developed a robotic wheelchair that isn't sure what it is. Normally, it operates on wheels like a conventional wheelchair, but when it meets an obstacle, the wheels turn into legs.
Wheels are the most efficient way for the disabled to get around, but they have one important limitation. For wheels, seemingly trivial obstacles like a curb or even a door sill can be as insurmountable as a brick wall. The Chiba robotic wheelchair gets around this problem by equipping the chair with four independently powered wheels mounted on five axes. These axes act as a suspension for the wheels, but when the wheels meet an obstacle, a transformation takes place.
The wheels have sensors next to them that scan the obstacle. If rolling over it isn't an option, the axes shift and turn into legs while the wheels act like feet. However, there’s more to it than that, in order to keep the chair from unceremoniously dumping its passenger on the ground.
The chair’s on-board computer assesses the obstacle and determines whether or not the leg can negotiate the step. Meanwhile, the other legs realign themselves to keep the chair stable. If the size and distance of the obstacle are right, the chair steps on or over it. If it makes a mistake, the variable wheel torque acts as a backup to power the chair over the obstruction.
As far as the passenger is concerned, none of this requires any attention. The chair has a joystick for steering, and all the passenger has to do is tell it where to go. The chair does the rest automatically, and the stability systems keeps the passenger comfortably level when negotiating obstacles or going down a ramp. Even tight spaces are easier to deal with because the chair can line up its wheels, extend a pair of stabilizers and turn a circle inside its own radius.
The robotic wheelchair is still in the concept stage, with the engineers figuring out the mechanics of the system. Once satisfied, the team’s next goal will be to have users test the chair so the team can fine tune its operation.