People confined to a wheelchair are still confronted with insurmountable obstacles in everyday life — even in today’s more wheelchair-accessible society. There are often no elevators in a building — or if so, they’re often out of order. And while there are already wheelchairs that can climb stairs, persons with physical disabilities still require assistance to prevent them from tipping over. Researchers at the Technical University of Munich (TUM) have now developed a stairclimbing wheelchair with the ability to stabilize itself. It is part of a larger mobility concept that enables wheelchair users to move independently for short and medium distances.

Scientists at TUM developed a wheelchair that can climb stairs. (Credit: Uli Benz/TUM)

Whether visiting friends, going shopping, or participating in events outside the home, mobility is the prerequisite for a self-determined life. People who are mobile also do not need to be looked after or attended to. However, something as simple as leaving their home without assistance can be a major hurdle for some people with disabilities.

It quickly became clear to the scientists: A wheelchair must be developed that can climb stairs. It should also be agile and narrow. The researchers thus limited the chassis to one axis. In contrast to a two-axle wheelchair chassis, this wheelchair can move forward and backward and rotate around its own axis almost simultaneously. The wheelchair holds itself up according to the inverted pendulum principle. “Each small positional change is recognized and immediately compensated by the drive system,” says Prof. Bernhard Wolf of the Heinz Nixdorf Chair for Medical Electronics at TUM.

Navigating Narrow Staircases

So how exactly does the new wheelchair conquer staircases? Previous concepts have utilized crawler chassis or castor configurations. “But those wheelchairs have to be monitored during the process,” explains Wolf. In other words, another person has to be on hand to ensure that the chair does not topple over. In addition, such wheelchairs have a large turning circle — making them unsuitable for use on narrow staircases.

Powered by an electric motor, the legs push the wheelchair to the next higher step. (Credit: Uli Benz/TUM)

The scientists decided on a bionic concept for their new chair. Two feet that have a similar configuration to human legs — with an upper and lower leg — are attached to the wheelchair. If the chair’s ultrasonic sensors detect stairs in the path of travel, the wheelchair reverses itself with its back to the stairs until the two wheels have physical contact with the first stair. Then the feet are extended, and the wheelchair lifts itself up the step. Powered by an electric motor, the legs push the wheelchair to the next higher step. Meanwhile, a camera system monitors the “staircase topography” to ensure that the wheelchair is firmly on a step and not, for example, on the edge.

This technology also makes it possible to manage very narrow staircases — with the exception of spiral staircases. When the chair is done ascending the stairs, it retracts its legs and swings back into forward motion in drive mode. The wheelchair can thus also go down the stairs again.

Comprehensive Mobility Concept

Using a prototype, engineers were able to show that their principle works. The concept goes beyond the climbing of stairs, however. “We want to give people a truly viable mobility alternative with this wheelchair,” says Wolf. The chair could also be used as a car seat in the future, for example, dispensing with the need to fold and stow the wheelchair prior to departure. It would also not be necessary for the user to be lifted from the car seat back into the wheelchair upon arrival. Since it has an internal drive, it is narrower than a standard wheelchair.

Potential industrial partners are still reluctant, however. “I think it is because the principle is technically a little complex, and of course, there are already standardized wheelchairs,” says Wolf. He is convinced that the demand for the bionic wheelchair would definitely be high. Although it costs more than a standard wheelchair, it offers its users the possibility to move around more freely.

Cooperation partners in the project are CoKeTT Zentrum at Kempten University (Prof. Petra Friedrich) and the Chair of Ergonomics at TUM (Professor Klaus Bengler).

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