A 1-DOF assistive exoskeleton with virtual negative damping: effects on the kinematic response of the lower limbs

Abstract

Abstract-We propose a novel control method for lowerlimb assist that produces a virtual modification of the mechanical impedance of the human limbs. This effect is accomplished through the use of an exoskeleton that displays active impedance. The proposed method is aimed at improving the dynamic response of the human limbs, while preserving the user's control authority. Our goal is to use active-impedance exoskeleton control to improve the user's agility of motion, for example by reducing the average time needed to complete a movement.Our control method has been implemented in a 1-DOF exoskeleton designed to assist human subjects performing knee flexions and extensions. In this paper we discuss an initial study on the effect of negative exoskeleton damping (a particular case of active-impedance control) on the subject's time to complete a target-reaching motion. Experimental results show this effect to be statistically significant. On average, subjects were able to reduce the time to complete the motion by 16%.

Survey of On-line Control Strategies of Human-Powered Augmentation Exoskeleton Systems

“…Force impulse and instantaneous end-effector oscillations are perfect system inputs to estimate VAC parameters [43]. The Cartesian space intended position depends on the stair height in this case can be transformed to the joint space as the mean value of the difference between the desired and the actual trajectories.…”

Inertia Compensation Control of a One-Degree-of-Freedom Exoskeleton for Lower-Limb Assistance: Initial Experiments

“…The same controller can turn the exoskeleton into an assistive device by making its virtual admittance active. In an earlier study, the authors tested the use of negative damping in order to make the exoskeleton perform net work on the legs [14], [16].…”

Desenvolvimento de controle de impedância aplicado a exoesqueleto biomecatrônico atuado por liga de memória de forma.

“…A partir dos conhecimentos adquiridos durante a revisão bibliográfica, um algoritmo de controle de impedância foi desenvolvido, baseando-se principalmente nos trabalhos de Aguirre-Ollinger et al (2007, 2009). Os fios de SMA também foram estudados, resultando num modelo matemático para realização de simulações e projeto do controlador deste atuador.…”

“…Note que, apesar desta definição contrastar com a de alguns autores, por exemplo, Aguirre-Ollinger et al (2007, 2009 Resultados experimentais indicaram bons resultados no seguimento de referências de pressão e posição, além da previsibilidade das forças de contato.…”

“…A realização dos ensaios no protótipo foi baseada no método utilizado por Aguirre-Ollinger et al (2007, 2009 …”