Robotic wheelchair controlled by thought alone

Paralyzed people could soon navigate around buildings using a robotic wheelchair that can be controlled by thoughts alone.

The wheelchair is designed for people with severe neuromuscular disabilities, and can even be used in crowded or unfamiliar surroundings, says Javier Minguez, head of the team at the University of Zaragoza in Spain that is developing the chair.

To direct the wheelchair, users concentrate on one of several possible destinations in a 3D map of their surroundings, which appears on a screen in front of them. Users wear a skullcap with 16 electrodes positioned around their scalp. These detect millisecond-long fluctuations in brain activity, which happen when the user looks at the point on the screen that coincides with a target destination.

As the user scans the on-screen map a blue spot flashes in sequence over each possible destination. When it flashes over the point the user is looking at, it provokes a fluctuation in their brain activity that is detected by the electrodes. The computer compares the sequence of flashes with the user's brain activity, and when a flash coincides with a fluctuation, it interprets that as indicating where the user wants to go.

To create the 3D map, a laser mounted on the front of the chair constantly scans its surroundings and updates the image. Sensors on the wheels also count the number of rotations, to keep track of the wheelchair's position as it moves. The wheelchair uses this map and its sensors to steer the user to their destination, avoiding any obstacles along the way.

In 2006, the team demonstrated that four children with cerebral palsy could use a touch screen built into an earlier version of their wheelchair to navigate around busy and constantly changing environments during their school day. In a study presented at the International Robotics and Automation Conference in May, they tested how well five healthy volunteers were able to control the wheelchair with their thoughts alone. Since the pattern of electrical activity in the brain of any individual is unique, each volunteer trained the system to detect their responses by concentrating on various points in a series of test images. They then learned how to control the wheelchair by steering it around a virtual circuit.

Once the volunteers had completed this test they were let loose in the real wheelchair, and asked to complete two circuits around the lab - one designed to test how well the chair could negotiate obstacles and one to demonstrate navigation in an open space.

Minguez says the volunteers learned to use the wheelchair confidently in about 45 minutes. "The purpose of this work was to demonstrate the usability of the wheelchair," he says.