Sit back and move forward with ease

• Human movement sciences
• Innovation & Industry

In brief

• Steering a conventional wheelchair requires constant braking and you need both hands. This is inefficient, takes a lot of energy and places a strain on the joints.
• Two research assistants at ETH Zurich have developed a wheelchair that can be steered with the backrest.
• This enables wheelchair users to move forward more efficiently and with fewer health problems.

What do a wheelchair and a shopping trolley have in common? The small front wheels on both of them are freely moveable in order to make the vehicle as agile as possible. However, the freely rotatable wheels have a drawback: if, for example, the ground inclines sideways, it is difficult to steer straight on. If you've ever pushed a full shopping trolley along a pavement, you'll know how arduous this is: the trolley pulls away to the side and you're constantly having to use your strength to steer it back again.

It's exactly the same for people travelling in a manual wheelchair: they're constantly having to correct their direction on the pavement in order to be able to move straight on and not end up in the road. While one hand is used to accelerate the vehicle, the other has to brake and steer in the opposite direction. Not only is this exhausting but it also places a strain on the joints.

Backrest as steering wheel

It doesn't have to be like that, thought Reto Togni and Stefan Villiger, both research assistants at ETH Zurich's Laboratory for Movement Biomechanics. They developed a wheelchair with a moveable backrest. This is directly connected with the front wheels and thus steers the entire vehicle. The entire process is purely mechanical: when the user leans to the right, the wheelchair moves to the right, and when he or she leans to the left, it moves to the left. "This saves a lot of energy and renders braking on pavements and at bends unnecessary," says Togni.

Faster with less energy

The tests in the underground car park on the Hönggerberg campus that Togni carried out as part of his doctoral project at ETH Zurich show how much less energy is needed for steering with the backrest. To this end, 29 test participants completed an obstacle course six times in succession: a straight path with a sideways inclination of five degrees, 180-degree bends and a slalom course. The test participants started off with a conventional wheelchair and then tried out the prototype with the moveable backrest. With both models, sensors in the large drive wheels recorded how much energy the test participants used to steer and navigate.

"It was already clear in the first round that the test participants needed much less energy to steer with the backrest," says Togni. Co-developer Villiger took part himself and confirms: "When travelling with the prototype along the straight incline, I didn't have to correct the steering with my hand once. And it was also much easier to move forward round the bend. With the conventional wheelchair I was constantly braking and propelling at the same time." This is also shown in the evaluations (see diagram).

Although the test participants required less energy to move forward with backrest-steered wheelchairs, they travelled faster than when in conventional wheelchairs. This astonished even the researchers: "You normally need more energy the faster you travel," says Togni.

Relief for the joints

Steering with the backrest not only reduces the energy outlay but also spares the shoulders, arms and hands of wheelchair users, who frequently develop shoulder problems over the years.

And according to the two researchers, there are also further health benefits: the gentle body movements needed for steering are also likely to stimulate the blood flow and can provide relief against backache and indigestion. Moreover, the weight shift relieves the bottom and could help to prevent pressure marks.

Another advantage is that you can navigate with one hand and have the second hand free to transport things from one place to another - be it an umbrella, mobile phone or a coffee.

However, this new kind of steering also has a disadvantage: rotating on the spot and moving in small spaces is not as easy as with a conventional wheelchair. It is for this reason that the prototype has a lever at the side that switches steering via the backrest on and off. The wheelchair can then be steered in the familiar way via the large drive wheels.

Inspired by the skateboard

Togni hit on the idea of backrest steering in 2017 during his Masters in Innovation Design Engineering. "I talked to people with disabilities about their assistive products and heard the desire for better functioning analogue equipment," says Togni. A lady, for instance, mentioned how nice it would be if as a wheelchair user she could sit back and enjoy the ride. Another person explained how frustrating it was to be overtaken by a skateboarder. "Surely it must also be possible to steer a wheelchair by shifting one's weight," thought Togni and began to tinker.

He constructed his first prototype in 2017 while studying for his Master's degree in London. Togni developed his technology further during his subsequent doctoral studies at the Laboratory for Movement Biomechanics at ETH Zurich and demonstrated in laboratory studies how his steering works from a biomechanical perspective and for whom it is suited.

Stefan Villiger studied mechanical engineering at ETH Zurich. He learned about the wheelchair project at an internal presentation. "I was fascinated by this simple and yet very elegant solution," says Villiger. He contacted Togni for his Master's thesis. They have since developed several prototypes together.

Supported by an ETH Pioneer Fellowship, the two ETH employees now have time to optimise their technology and bring it to market. To this end they will soon be founding the start-up Versive.

Why only now?

So far more than 50 wheelchair users have tested the backrest steering and many are impressed by it. "One test participant said it was the greatest improvement for wheelchair users since the invention of the wheel," says Togni. Paraplegic Ursula Memmishofer, who can be seen external page in this video as a test participant a few of years ago, has been using a Versive wheelchair for six months and no longer wishes to part with it.

Whether car, ship or go-kart: almost every means of transportation has a steering wheel, underlines Togni. "If we also think of a wheelchair as a means of transportation, then it makes obvious sense that this should also have one."

Why did no-one come up with the idea before the two of them of using the backrest for steering? "That's also something we've been wondering," says Togni. Togni suspects that the reason why wheelchairs have barely developed further is that they have not removed themselves sufficiently from their original purpose. "The wheelchair has from the year dot served nursing and care home staff as a device for transporting sick and disabled people and has until now been viewed too little from the user's perspective."

Simple idea, difficult implementation

The steering technology is well advanced and works - and the patent has been secured. The challenge now is to produce and distribute entire wheelchairs.

This is not so much due to the components, as these comprise "simple and inexpensive parts of the sort also required, for instance, for bicycles". The challenge is the adjustment to individual users. "For Swiss invalidity insurance to fund a wheelchair, it is necessary to ensure that it is highly adjustable to individual users," adds Togni: "A mid-range wheelchair can be assembled in hundreds of thousands of different ways. The spare parts catalogue of a wheelchair manufacturer therefore by itself contains more than 100 pages." And Villiger adds: "We need to find out how we can make adjusting the wheelchairs as efficient as possible but at the same time highly customisable."

Before they can bring their product to market, they need to clarify some fundamental issues with insurance providers such as Swiss invalidity insurance and Suva. "At present we are only able to produce wheelchairs for self-payers," says Togni.

The two ETH employees also considered offering their backrest technology to other manufacturers as an accessory. But this would have been too complicated. "The introduction of a new accessory item would have entailed a separate compatibility certificate for each individual wheelchair manufacturer," says Togni.

"Sell it as a toy"

Togni and Villiger wish to be on the Swiss market with their wheelchairs and recognised by the insurance providers by mid-2027.

They are currently in the process of procuring funds to bring their technology to market. They then wish to enlarge their team. In the longer term the start-up is seeking access to hospitals and somebody who is able to adjust the wheelchairs individually to the users and knows their way around regulations, tests and refunds.

The two refuse to be deterred by the scepticism they encounter in the sector. Togni: "We have figures to prove that our solution is many times more efficient. And we have sufficient test participants who say they prefer steering via the backrest."

One test participant even gave them the following tip: "If Swiss invalidity insurance doesn't want to pay, just sell it as a toy. Your vehicle is definitely fun to use."

Reto Togni and Stefan Villiger will give an insight into their research at the ETH Entrepreneurship stand during the ETH Industry Day @ Open-i at the Zurich Convention Center on 21 November 2024.

Experience CYBATHLON 2024!

The third edition of the one-of-a-kind championship initiated by ETH Zurich takes place in the SWISS Arena in Kloten from 25 to 27 October 2024. Cybathlon is a competition in which people with disabilities compete to carry out everyday tasks with the aid of state-of-the-art assistive technology. You can look forward to watching teams from across the world compete in exciting competitions in eight disciplines - as well as an interactive supporting programme. Get your tickets external page online or at the box office on site or watch the livestream on the Cybathlon website, available from 25 October.

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