Quadriplegics Can Control Exoskeletons with Their Brain

Artificial limbs help people who have lost a part of their arms or legs to regain partial functionality of their extremities. However, for those who have lost control of a major part of their bodies and thus rendered quadriplegic, artificial limbs are not of much use. For addressing such and other whole-body disabilities, exoskeletons are showing great promise.

Scientists working at the Technische Universitat Berlin and Korea University are creating such lower-limb exoskeletons. The control system here is completely hands-free. Rather, it is a brain-to-computer interface, which controls the exoskeleton, by decoding and making use of signals from the wearer’s brain. According to the researchers, volunteers who were given the exoskeleton to use took only a few minutes for learning to operate the system. Therefore, substantially paralyzed people may hope to walk again with the help of this exoskeleton.

Research on such exoskeleton systems is not new and several types are in development and in limited production in many parts of the world. However, most achieve controls by detecting subtle movements in the upper body of the wearer. However, the difference in the KU/TU Berlin unit is the control is entirely dependent on brain signals. Therefore, this is useable even by a completely paralyzed person.

The human brain generates different signals when the person stares at a specific LED. These signals are detected and interpreted to be used for controlling the hands-free exoskeleton. An EEG brain control interface connects wirelessly to the main computer of the control system.

In actual practice, the wearer stares at any one of five flashing LEDs. This initiates waves in the wearer’s brain and an electroencephalogram or EEG worn as a cap reads the signals. Because each LED flashes at a different rate, focusing on any one at a time produces a specific signal pattern in the brain of the user corresponding to a desired mode of movement. The computer system interprets the readings of these signals sent to it from the EEG cap and converts them to system instructions for operating the exoskeleton.

As this method of control does not require detection of movement from any other body part, it is eminently suitable for even those who have lost the capacity for voluntary body control, except for eye movements. Ordinarily, such people would not be able to use or control a standard exoskeleton. According to the researchers, their system has a much better signal-to noise ratio.

The brain generates signals depending on external signals it receives from its surroundings. This acts like noise to the actual control signal desired for movement. By concentrating on a flashing LED, the researchers are effectively separating the user’s brain control signals from being cluttered with external stimuli. The result is a more accurate exoskeleton operation than what a conventional hard-wired system could have achieved.

Exoskeleton systems are notorious for creating loss of electrical noise, especially affecting the EEG signals. However, the frequency of the flickering LED acts as a filter to separate the EEG signal effectively. This exoskeleton system helps people with high spinal cord injuries or those with motor neuron disease who face difficulties in communicating or using their limbs.