ABSTRACT
We developed an instrumented object for quantitative evaluation of functional tasks performed with lateral hand grasp. The device was instrumented with three force transducers based on metal foil strain gauges. The transducers allowed simultaneous monitoring of the grasp force, the perpendicular force at the tip, and the force in the long axis of the instrumented object. The device was used for evaluation of a simulated eating task performed by able-bodied subjects and a tetraplegic subject instrumented with an FES hand grasp system. Use of the instrumented object will allow us to gain a more thorough understanding of the application of forces on a tool during important functional tasks of daily living. This knowledge will be used to improve the control of a closed-loop FES hand grasp system incorporating natural sensory feedback.
Subject(s)
Hand Strength/physiology , Quadriplegia/physiopathology , Biomechanical Phenomena , Biomedical Engineering , Eating , Electric Stimulation Therapy , Equipment Design , Humans , Quadriplegia/rehabilitationABSTRACT
We used signals from tactile mechanoreceptors in the skin of the index finger, recorded with an implanted cuff electrode, to automatically control grasp force in a hand grasp neuroprosthesis. Phasic events in the recorded nerve signal, related to mechanical events on the skin, were used to adjust electrical stimulation of hand muscles without any prior knowledge about muscle strength and properties of a held object. A simulated eating task was used to evaluate the hand grasp neuroprosthesis. When using the neuroprosthesis with feedback from natural sensors, the average grasp force could be reduced in comparison to not using feedback. Reducing grasp force is considered a major factor to decrease muscle fatigue, allowing a prolonged use of the hand grasp neuroprosthesis.
