Feasibility of Using Ipsilateral Electromyographic Signals to Control an Air-Muscle-Actuated Grasping Orthosis

Feasibility of Using Ipsilateral Electromyographic Signals to Control an Air-Muscle-Actuated Grasping Orthosis

&nbsp;&nbsp;In this work, we investigate the potential of using an air-muscle actuated orthosis controlled by an electromyographic (EMG) signal to reliably augment the grasping force of the hand, thereby allowing the user to reduce the muscle activation required for a power-grasping task. In particular, we tested the hypotheses that subjects could stably handle objects and learn to reduce both their grip force and muscle activation levels with force supplementation. In this study, a surface-mounted EMG sensor on the flexor digitorum provides the input to a proportional-integral-derivative controller governing the force generated by the orthosis. Nine subjects performed a sequence of unassisted and assisted lifts of a weighted and instrumented cylinder. When using the orthotic system to lift the cylinder, subjects reliably reduced their mean grip force and mean contraction level (measured as % Maximum Voluntary Contraction, or %MVC) (p＜0.01).<BR>&nbsp;&nbsp;The grip force applied to the cylinder dropped for seven of the nine subjects (p＜0.01) and the %MVC dropped for eight of the nine subjects (p＜0.01). None of the subjects exhibited any instability or reported any difficulties when using the orthosis. On average, the subjects reduced their %MVC and grasp force by 31% and 56% respectively, so using an air-muscle-powered orthosis controlled by an ipsilateral EMG signal appears to be a feasible concept.