Integration of an EMG-based NMES controller with a passive exoskeleton to support daily upper limb activities

MUNDUS is an assistive framework for recovering interaction capability of severely impaired people based on upper limb motor functions. Within this project, the present work aimed at integrating a commercial passive exoskeleton for weight support with an EMG-controlled neuroprosthesis for hand-to-mouth movements. Being the stimulated muscle the same from which the EMG was measured, first it was necessary to separate the volitional EMG from the stimulation response. Thus, an adaptive filter to remove the M-wave was developed. Then, an EMG integration-based controller was designed: when the volitional EMG exceeded a pre-defined threshold, the pulse width ramped up until the maximal value and was kept constant until the volitional EMG dropped below an inferior threshold. The operation of the control system was tested on one healthy volunteer, who was asked to perform some hand-to-mouth movements, supported by both the exoskeleton and the EMG-controlled neuroprosthesis. Preliminary results showed that the filter was able to discriminate between increasing values of volitional EMG, while the controller operation reflected the subject’s intention. The study demonstrated the feasibility of an EMG-controlled neuroprosthesis for daily upper limb support on healthy subjects, providing a first step forward towards the development of the final MUNDUS platform.