Scientists have developed a brain-computer interface for controlling a lower limb exoskeleton.
As recent experiments have shown, exoskeletons hold great promise in assisting those who have lost the use of their legs to walk again. However, for those who are quadriplegic, diagnosed with a motor neuron disease or have suffered a spinal cord injuries, hand control is not an option. To overcome this barrier, researchers at Korea University and TU Berlin have developed a brain-computer interface that can command a lower limb exoskeleton by decoding specific signals from within the user’s mind.
This is achieved by wearing electroencephalogram (EEG) cap, which enables a user to move forwards, turn left and right, sit and stand simply by staring at one of five flickering LEDs, each representing a different action. Each of the lights flicker at a different frequency, and when the user focuses their attention on a specific LED, this frequency is reflected within the EEG readout. This signal is then identified and used to control the exoskeleton.
The exoskeleton control system consists of a few parts: the exoskeleton, an ATmega128 MCU powered visual stimuli generator and a signal processing unit. As the team notes, a PC receives EEG data from the wireless EEG interface, analyzes the frequency information, and provides the instructions to the robotic exoskeleton.
This method is suitable for even those with no capacity for voluntary body control, apart from eye movements, who otherwise would not be able to control a standard exoskeleton. The researchers believe that their system offers a much better signal-to-noise ratio by separating the brain control signals from the surrounding noise of ordinary brain signals for more accurate exoskeleton operation.
“Exoskeletons create lots of electrical ‘noise,’” explains Professor Klaus Muller, an author on the paper that has been published in the Journal of Neural Engineering. “The EEG signal gets buried under all this noise — but our system is able to separate not only the EEG signal, but the frequency of the flickering LED within this signal.”
The control system could serve as a technically simple and feasible add-on to other devices, with EEG caps and hardware now emerging on the consumer market. According to the researchers, it only took volunteers a few minutes to get the hang of using the exoskeleton. Because of the flickering LEDs, participants were carefully screened and those suffering from epilepsy were excluded from the study. The team is now working to reduce the ‘visual fatigue’ associated with long-term use.
“We were driven to assist disabled people, and our study shows that this brain control interface can easily and intuitively control an exoskeleton system — despite the highly challenging artefacts from the exoskeleton itself,” Muller concludes.
Those wishing to learn more can read the entire paper here, or watch the brain-controlled exoskeleton in action below.
[Images: Korea University / TU Berlin]