Assisting with Fingertip Force Control by Active Bio-Acoustic Sensing and Electrical Muscle Stimulation

Fingertip force control plays an important role in learning motor skills. Exoskeleton gloves have been developed to assist with fingertip force control, but having the equipment on the fingers interferes with finger motion control and tactile sensation. Thus, we present a system for assisting with voluntary fingertip force control that does not require any devices to be worn on the fingers. In this study, we focused particularly on lateral pinch force, which is grip force achieved with the pad of the thumb and the lateral surface of the index finger to grasp objects. We use active bio-acoustic sensing to estimate voluntary pinch force with piezo elements attached to the back of the hand and electrical muscle stimulation (EMS) to the forearm to control involuntary pinch force in a closed-loop system. We developed three prototypes and conducted user studies to investigate whether our system can assist with pinch force control under several target forces, from weak to strong. Our user studies showed that the combination of active bio-acoustic sensing and EMS can assist users in maintaining the pinch force closer to the target force.