Evaluation of elbow power assistive system using sEMG signals for individuals with muscle weakness: Influence of assistive gain for variation of payload

The change of the assistive gain (AG), the ratio of the assistance to the human torque, can lead to unstable movement of the user. We investigated the influence of variation of the AG in developing a power assistive system. The elbow joint torque in the sagittal plane was estimated using sEMG signals from upper limb muscles, and a one-degree-of-freedom (1DOF) assistive system was provided the power that was proportional to the estimated torque. A disabled as well as healthy participants performed elbow flexion/extension with the assistance gave variety to the AG and payload. The results indicated that the sEMG-driven assistance reduced the muscle activities for the movement while the AG was increased for all participants, although the difficulty of manipulating the system was increased with the gain being applied rather than with no assistance for healthy participants only. This study will allow the finding of efficient AG for a given payload condition.