Examination of Biofeedback to Support the Use of Upper-Extremity Exoskeletons Under Proportional Myoelectric Control

Exoskeletons have the potential to assist individuals in completing daily tasks and augment industrial workers in labor-intensive jobs. While previous studies have shown the capability of powered upper limb exoskeletons to reduce muscle effort and maintain task performance in continuous cyclical movements, their effectiveness in natural movements that contain both dynamic and static tasks remains uncertain. This study aimed to investigate the impact of visual and haptic electromyography (EMG) biofeedback on participants $(n=36)$ while they performed a target position matching task with a powered upper limb exoskeleton. Our hypothesis was that users could benefit from the biofeedback to minimize muscle effort and use the exoskeleton more effectively. However, the results indicated that the biofeedback did not reduce muscle effort in participants, but it had a positive impact on the smoothness of participants’ extension movements. The challenge of reducing muscle effort appeared to stem from participants experiencing difficulty in relaxing their muscles, even when the exoskeleton provided support for the task or maintained the desired posture. Nevertheless, participant feedback supported that biofeedback might enhance their satisfaction with exoskeleton usage, which is a crucial factor in promoting long-term acceptance. These findings provide a foundation for future research in user training methods and controller development for exoskeletons.