Abstract
Control of assistive devices by voluntary user intention is an underdeveloped topic in the Brain–Machine Interfaces (BMI) literature. In this work, a preliminary real-time BMI for the speed control of an exoskeleton is presented. First, an offline analysis for the selection of the intention patterns based on the optimum features and electrodes is proposed. This is carried out comparing three different classification models: monotonous walk vs. increasing and decreasing change speed intentions, monotonous walk vs. only increasing intention, and monotonous walk vs. only decreasing intention. The results indicate that, among the features tested, the most suitable parameter to represent these models are the Hjorth statistics in alpha and beta frequency bands. The average offline classification accuracy for the offline cross-validation of the three models obtained is 68 ± 11%. This selection is also tested following a pseudo-online analysis, simulating a real-time detection of the subject’s intentions to change speed. The average results indices of the three models during this pseudoanalysis are of a 42% true positive ratio and a false positive rate per minute of 9. Finally, in order to check the viability of the approach with an exoskeleton, a case of study is presented. During the experimental session, the pros and cons of the implementation of a closed-loop control of speed change for the H3 exoskeleton through EEG analysis are commented.
Highlights
Motor disabilities due to stroke impairment or spinal cord injury are an increasing problem in our modern society [1]
Cognitive involvement can be achieved in many ways, including through the recording of brain activity establishing a direct connection between the mental task and the user
Most EEG-based intent studies show an analysis of brain activity without taking into account the implementation part of the Brain–Machine Interfaces (BMI), which requires a closed-loop analysis with visual or auditory feedback [27] or sensitive motor feedback provided by an assistive control devices [13,15]
Summary
Motor disabilities due to stroke impairment or spinal cord injury are an increasing problem in our modern society [1]. The current conventional motor therapies consist of the execution of intensive and repetitive sessions to mobilize the affected limb. These therapies are used to facilitate the recovery and learning postural movement allowing to adapt the disability to the daily life. These procedures are turning the focus on increasing cognitive involvement in order to increase the activation of neural plasticity processes [2]. ERD/ERS is described as a change of power in the alpha (8–12 Hz) and beta (13–30 Hz) bands.
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