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Brain Machine Interface Enabled Wheelchair

Researchers at the University of South Florida have developed a wheelchair-mounted robotic arm, which is capable of interfacing with the wheelchair user's thoughts via a non-invasive neural interface.

The interface system makes use of P-300 brain waves. P-300 is a specialised type of brain wave, that operates out of the frontal lobe. Really two different waves, it is called P-300, because it is triggered about 300 miliseconds after the brain receives sensory stimulus which it deems relevant to the task it is currently focussed on.

In this example, the BMI system is connected to an external monitor, which is used solely to give a visual reference for arm commands - single digits for the user to focus their mind on. The system, working from the P-300 brain response, only functions from brain response to visually aquired sensory data, not from purely internal thought, so the display is required. It can of course, be attached to the chair itself, and far smaller than the one used for initial experiments.

The system was developed by psychology professor Emanuel Donchin and colleagues. It was previously used as the basis for the virtual keyboard, which allowed a user to type with a virtual keyboard, using the same P-300 response. In that work, the user looked at a letter and concentrated on it. About 300ms later, the P-300 was emitted, studied by the computer system, and the letter was typed.

P-300 is too slow for subconscious use, and requires conscious focus to use, but it makes sense to utilise it at our current level of understanding of brain interfacing, because it is extremely reliable, and not subject to excessive noise, as it is concentration based.

The wheelchair uses this same need for concentration, but has a greatly reduced control-set from the keyboard.

Early testing by human users has shown that the WMRA can be controlled "without the user moving a muscle." The WMRA does not use any pre-programmed movements unless chosen by the user.

"We modified the BCI system to display a matrix of several options that include actions or directions that the user would like to have the WMRA perform," said Redwan Alqasemi, a researcher in the USF Department of Mechanical Engineering's Center for Rehabilitation Engineering and Technology. "The user wears a head cap fitted with electrodes to measure P-300 electroencephalogram (EEG) activities in the brain. While the movement options intensify on a screen and flash at certain frequencies, the user concentrates on the option desired to trigger the desired P-300 brain signal. The electrodes detect the signal, relate it to the desired action, then, the WMRA [wheelchair motorised robotic arm] control system translates the brain signal to the robotic arm, which carries out the desired movements."

All of the considerable computing power necessary is integrated into the chair itself, wired into a specially designed form factor, which fits under the seat of the wheelchair. For practicality reasons, the system is only compatible with powered wheelchairs due to space and weight requirements.


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