Bionic arm: We have the technology! Thursday, 05 May 2016

Canadian engineers have developed a control system for a bionic arm that allows users better control over the hand.

The system consists of an armband of pressure sensors embedded in the prosthetic socket. These track movements in the user's remaining muscles as she or he performs intuitive actions, such as grasping a bottle. Computer algorithms then map the sensor data to decode the user's intentions and move the prosthesis.   

“The more data you give it, the more it will learn,” said Lukas-Karim Merhi from Simon Fraser University in Vancouver. The system takes incoming data and makes predictions in real time. It also generates computer models to improve future performance.

The system is being trialled by paralympic skier Danny Letain, a former train driver who lost his left arm below the elbow 35 years ago. He has since used a body-powered prosthesis with a pincer-like split hook, which uses a series of straps that mechanically manoeuvre the artificial limb but it’s a tiring process.

“The hook is durable and quick to respond, but controlling it with straps is not natural,” Letain said.   

With the new control system, he has developed a variety of different grip patterns that he says work “well beyond” what he could achieve with prosthetic devices.

“With this new system, it feels like I’m opening and closing my hand," he said.

"The most exciting moment for me was feeling my left index finger and the little finger for the first time since my accident. With the hook you don’t use those muscles at all. This system puts my mind to work in a whole new way.”

He will put the arm to the test in October at the inaugural Cybathlon event, an international competition in Zurich for people with disabilities using robotic technology.

He will use the technology in an obstacle course for people with powered arm prostheses to perform everyday tasks such as slicing bread and opening jars. The team tested the prototype at the Cybathlon trial held last July and is working to optimise the system for the competition.

[Athlete Danny Letain (centre) with the bionic arm, flanked by Lukas-Karim Merhi (left) and Professor Carlo Menon. Photo: Simon Fraser University]

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