SFU mechatronics professor Carolyn Sparrey (left) and graduate student Louise Thomas (right) pose with the Elevation™ model manual wheelchair with test weights that mimic a seated person.

Mechatronics student’s research poised to revolutionize wheelchair design

March 08, 2017

By Caitlin Dawson

Imagine if a manual wheelchair could be adjusted as easily as an office chair.  

This seemingly simple idea could have a radical impact on the future of wheelchair design—and SFU mechatronics student Louise Thomas’ research is key to making it a reality.        

“You only sit at your desk for part of the day, so you would expect a wheelchair, which a person spends their entire waking day in, to be adaptable,” says Thomas, a master’s student specializing in biomechanics.

But this hasn’t been the case in traditional wheelchair design—until now.

For the last two years, Thomas has been working with SFU mechatronics professor Carolyn Sparrey and BCIT professor Jaimie Borisoff, a wheelchair user himself, to research the impact of an adjustable backrest and seat on wheelchair usability.

The inspiration for the Elevation™ wheelchair, designed and created by Borisoff, stemmed from the most complex machine on earth: the human body.

“That burn you feel in your calves when you’re hiking? That’s because your body is naturally tilting forward to account for the slope,” says Thomas, who completed her undergraduate degree in sports engineering at The University of Adelaide in Australia before joining SFU.

“These kinds of subconscious micro-adjustments allow you to be stable on different kinds of slopes.”

“Wheelchair users also deal with a lot of terrains in their daily lives, but they can’t make these adjustments because solid wheelchair frames are not adaptable.”

Wheelchair ergonomics present a unique challenge because stability is a double-edged sword: the more stable the wheelchair, the harder it is to push.

By distributing a user’s weight between the front and rear wheels, traditional wheelchair design favours maximum stability, at the cost of maneuverability. As a result, wheelchair users can suffer overuse injuries such as repetitive shoulder strains, Carpal Tunnel Syndrome, and more.

But a dynamic seat and backrest allows the user to change the wheelchair’s stability as needed throughout the day, simulating the adaptability of the human body.

“It’s all about finding that sweet spot between stability and maneuverability, depending on the terrain,” says Thomas.

To test this solution, Thomas created a virtual version of the wheelchair based on real-life data from motion-capture lab tests, using a manual wheelchair and crash test dummy. She then ran more than 3,000 simulations of the wheelchair in various positions, taking into account variables such as backrest position, user weight, wheel position and more.

The results are promising.

“By changing the backrest from a reclined to a fully upright position, uphill stability could be improved by over 15 degrees, allowing wheelchair users to wheel on steeper slopes than previously possible,” says Thomas.

“When the user is on level ground, decreasing stability by changing the backrest to a more reclined position makes it easier to wheel, reducing arm strain.”

The adjustments could also increase independence for wheelchair users.

“By changing the seat height, they can see eye-to-eye with people, and reach things that they couldn’t have before.”

Thomas will present her research at the SFU finals of the Three Minute Thesis competition on March 27.  She hopes to graduate in June and combine her passion for communication and technology in a job in technical sales for the biomechanics industry.

“I really hope this research gets out to the manufacturers of wheelchairs, and that in the future we’ll see manual wheelchairs with adjustable seats and backrests become standard,” says Thomas. “I believe it has the potential to make a real difference in people’s lives.”