A lower limb exoskeleton control system based on steady state visual evoked potentials.
OBJECTIVE
We have developed an asynchronous brain-machine interface (BMI)-based lower limb exoskeleton control system based on steady-state visual evoked potentials (SSVEPs).


METHODS
By decoding electroencephalography signals in real-time, users are able to walk forward, turn right, turn left, sit, and stand while wearing the exoskeleton. SSVEP stimulation is implemented with a visual stimulation unit, consisting of five light emitting diodes fixed to the exoskeleton. A canonical correlation analysis (CCA) method for the extraction of frequency information associated with the SSVEP was used in combination with k-nearest neighbors.


RESULTS
Overall, 11 healthy subjects participated in the experiment to evaluate performance. To achieve the best classification, CCA was first calibrated in an offline experiment. In the subsequent online experiment, our results exhibit accuracies of 91.3 ± 5.73%, a response time of 3.28 ± 1.82 s, an information transfer rate of 32.9 ± 9.13 bits/min, and a completion time of 1100 ± 154.92 s for the experimental parcour studied.


CONCLUSIONS
The ability to achieve such high quality BMI control indicates that an SSVEP-based lower limb exoskeleton for gait assistance is becoming feasible.
Department of Brain and Cognitive Engineering, Korea University, Anam-dong, Seongbuk-ku, Seoul, Korea.
No-Sang
NS
Kwak
Klaus-Robert
KR
Müller
Seong-Whan
SW
Lee
D000328:Adult; D001186:Artificial Limbs; D062207:Brain-Computer Interfaces; D004569:Electroencephalography / Q000295:instrumentation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005074:Evoked Potentials, Visual; D000067190:Exoskeleton Device; D005246:Feedback; D020233:Gait Disorders, Neurologic / Q000503:physiopathology* / Q000534:rehabilitation*; D006801:Humans; D035002:Lower Extremity; D008297:Male; D012371:Robotics / Q000295:instrumentation; D014796:Visual Perception