There have doubtless been times when you've had both hands full, and wished that you had a third arm. Well, scientists have discovered that a robotic third arm can in fact be quite easily controlled via movements of the diaphragm muscle.
The study was conducted at Switzerland's EPFL research institute, by a team led by Prof. Silvestro Micera. It was part of the Swiss National Centre of Competence in Research's larger Third Arm project.
For the study, a rig was created in which users sat while grasping handles on two exoskeleton-type arms, and while wearing a sensor-equipped belt that detected movements of their diagram. They also wore a VR headset, through which they viewed a virtual environment.
By moving the exoskeleton arms, it was possible for users to perform tasks with virtual versions of their real arms in the VR world. What's more, by moving their diaphragm in specific manners, they could also control a virtual third arm. Located between their virtual left and right arms, that third arm was designed with a symmetrical six-fingered hand – it had a thumb on either side – so it wouldn't be thought of as belonging to one side or the other.
When tested on 61 volunteers over 150 sessions, the setup proved to be quite easy for most people to master. Importantly, the test subjects were able to control their left and right arms while simultaneously controlling the third arm – sort of like patting your head and rubbing your stomach at the same time.
The participants were also able to take part in conversations, and divert their gaze away from the task, while working the third arm.
In a subsequent phase of the study, volunteers were equipped with a physical robotic arm which was strapped to their chest. The device was really just a rod that extended in and out of a base, but users were still able to move it so that its "hand" hovered over a given target circle as instructed.
All of that being said, the research isn't aimed specifically at the development of a practical third robotic arm.
"The main motivation of this third arm control is to understand the nervous system," said Micera. "If you challenge the brain to do something that is completely new, you can learn if the brain has the capacity to do it and if it’s possible to facilitate this learning. We can then transfer this knowledge to develop, for example, assistive devices for people with disabilities, or rehabilitation protocols after stroke."
A paper on the study was recently published in the journal Science Robotics. You can see the virtual and physical third arms in action, in the video below.
Source: EPFL