title: Equilibrium-point control of human elbow-joint movement under isometric environment by using multichannel functional electrical stimulation.
abstract: Functional electrical stimulation (FES) is considered an effective technique for aiding quadriplegic persons. However, the human musculoskeletal system has highly non-linearity and redundancy. It is thus difficult to stably and accurately control limbs using FES. In this paper, we propose a simple FES method that is consistent with the motion-control mechanism observed in humans. We focus on joint motion by a pair of agonist-antagonist muscles of the musculoskeletal system, and define the "electrical agonist-antagonist muscle ratio (EAA ratio)" and "electrical agonist-antagonist muscle activity (EAA activity)" in light of the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, respectively, to extract the equilibrium point and joint stiffness from electromyography (EMG) signals. These notions, the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, are based on the hypothesis that the equilibrium point and stiffness of the agonist-antagonist motion system are controlled by the central nervous system. We derived the transfer function between the input EAA ratio and force output of the end-point. We performed some experiments in an isometric environment using six subjects. This transfer-function model is expressed as a cascade-coupled dead time element and a second-order system. High-speed, high-precision, smooth control of the hand force were achieved through the agonist-antagonist muscle stimulation pattern determined by this transfer function model.
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Matsui
authors.affiliation: Fujitsu Limited Kanagawa, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Hishii
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Maegaki
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Yuto
authors.initials: Y
authors.lastname: Yamashita
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Uemura
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hirai
authors.affiliation: Department of Systems Science, Faculty of Engineering Science, Osaka University Osaka, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Miyazaki
keywords: EAA activity; EAA ratio; equilibrium-point control; functional electrical stimulation (FES); muscle synergy