Investigation of dielectric elastomer human energy harvesting to reduce knee joint torque deviation due to bracing

J Rehabil Assist Technol Eng. 2019 Oct 15;6:???. doi: 10.1177/2055668319862140. eCollection 2019 Jan-Dec.

Abstract

Introduction: The use of a smart electromechanical material, dielectric elastomer, is investigated for the development of an active bracing technique, which modifies the stiffness and damping of the knee brace during energy harvesting so as to reduce knee joint torque deviation during late swing in braced walking.

Methods: The bracing technique considered involves a dielectric elastomer energy harvesting cycle, which activates only when the knee flexor muscles are contracting eccentrically during late swing. The brace reduces the leg extension deviation during late swing in braced walking by transforming a portion of the mechanical stored energy into electrical energy, reducing the required internal work performed within the body.

Results: Simulated behavior of the dielectric elastomer brace worn across the knee joint demonstrates that when properly activated, the dielectric elastomer brace's reduction in stiffness and increase in damping minimize the added energy expenditure of knee joint bracing during late swing.

Conclusions: The modeling results demonstrate the effective application of a soft, circumferential, dielectric elastomer energy harvesting knee brace, which utilizes the changes in the dynamic behavior of the knee joint occurring during energy harvesting in order to reduce the added demand placed on the knee joint under braced conditions.

Keywords: Energy harvesting; active bracing; knee joint bracing; smart materials.