A hybrid BMI-based exoskeleton for paresis: EMG control for assisting arm movements.

J Neural Eng

Systems Neuroscience Section, Department of Rehabilitation for Brain Functions, Research Institute of National Rehabilitation Center for Persons with Disabilities, 4-1 Namiki, Tokorozawa, Saitama 359-8555, Japan. Biointerfaces Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503, Japan.

Published: February 2017

AI Article Synopsis

  • This study developed a brain-machine interface (BMI) exoskeleton that combines EEG and EMG signals to allow real-time control for individuals with paralysis, enabling them to move their arms and hands.
  • Using a derived formula based on a musculoskeletal model, researchers estimated joint angles from EMG signals in both able-bodied subjects and patients with spinal cord injuries, achieving high correlation with actual measured angles.
  • The results demonstrated that the exoskeleton enabled effective arm positioning and movement, as one patient successfully completed tasks such as carrying a ball, showcasing the potential of this technology for improving mobility in paralyzed individuals.

Article Abstract

Objective: Brain-machine interface (BMI) technologies have succeeded in controlling robotic exoskeletons, enabling some paralyzed people to control their own arms and hands. We have developed an exoskeleton asynchronously controlled by EEG signals. In this study, to enable real-time control of the exoskeleton for paresis, we developed a hybrid system with EEG and EMG signals, and the EMG signals were used to estimate its joint angles.

Approach: Eleven able-bodied subjects and two patients with upper cervical spinal cord injuries (SCIs) performed hand and arm movements, and the angles of the metacarpophalangeal (MP) joint of the index finger, wrist, and elbow were estimated from EMG signals using a formula that we derived to calculate joint angles from EMG signals, based on a musculoskeletal model. The formula was exploited to control the elbow of the exoskeleton after automatic adjustments. Four able-bodied subjects and a patient with upper cervical SCI wore an exoskeleton controlled using EMG signals and were required to perform hand and arm movements to carry and release a ball.

Main Results: Estimated angles of the MP joints of index fingers, wrists, and elbows were correlated well with the measured angles in 11 able-bodied subjects (correlation coefficients were 0.81  ±  0.09, 0.85  ±  0.09, and 0.76  ±  0.13, respectively) and the patients (e.g. 0.91  ±  0.01 in the elbow of a patient). Four able-bodied subjects successfully positioned their arms to adequate angles by extending their elbows and a joint of the exoskeleton, with root-mean-square errors  <6°. An upper cervical SCI patient, empowered by the exoskeleton, successfully carried a ball to a goal in all 10 trials.

Significance: A BMI-based exoskeleton for paralyzed arms and hands using real-time control was realized by designing a new method to estimate joint angles based on EMG signals, and these may be useful for practical rehabilitation and the support of daily actions.

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Source
http://dx.doi.org/10.1088/1741-2552/aa525fDOI Listing

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