Impedance Reduction Control of a Knee Joint Human Exoskeleton System

W. Huo 1 Samer Mohammed 1 Yacine Amirat 1
1 SIRIUS
LISSI - Laboratoire Images, Signaux et Systèmes Intelligents
Abstract : Reducing human lower limb effort during walking is still a challenge for wearable exoskeletons. From the wearer's viewpoint, joint impedance increases while wearing the exoskeleton due to the fact that the exoskeleton's mass, friction, and gravity are added to those of the human lower limbs. Active impedance is required from the exoskeleton to compensate not only the exoskeleton's mechanical impedance but also that of the human limb. This paper presents a nonlinear impedance reduction control (IRC) approach applied to a knee joint exoskeleton during flexion/extension movements. The IRC approach ensures impedance adaptation of the human-exoskeleton system toward a desired level. The proposed method is an alternative to sensor-based impedance controllers where the human joint torque is estimated using electromyography (EMG) sensors, force/torque sensors, and so on. The performance of the proposed approach and its robustness with respect to modeling uncertainties are theoretically analyzed and discussed. Experiments were conducted with four healthy subjects to verify the effectiveness of human effort reduction. The root mean square of the EMG signals of the muscles involved in the flexion/extension was used as a metric. The experimental results show that EMG signal levels can be efficiently reduced by inertia, damping, and gravity compensation compared with those obtained without wearing the exoskeleton.
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Article dans une revue
IEEE Transactions on Control Systems Technology, Institute of Electrical and Electronics Engineers, 2018, 〈10.1109/TCST.2018.2865768〉
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Soumis le : vendredi 31 août 2018 - 13:16:30
Dernière modification le : dimanche 30 décembre 2018 - 01:04:53

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W. Huo, Samer Mohammed, Yacine Amirat. Impedance Reduction Control of a Knee Joint Human Exoskeleton System. IEEE Transactions on Control Systems Technology, Institute of Electrical and Electronics Engineers, 2018, 〈10.1109/TCST.2018.2865768〉. 〈hal-01865344〉

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