A Soft Wearable Exosuit Reduces the Fatigue of Biceps Brachii Muscle

In this paper, we propose a new soft wearable exosuit for shoulder complex, which is developed to provide assistance force and reduce the muscular fatigue effectively to arms when human holds heavy loads with arms for a long time. The innovations of our work are as followings. First, the actuator of exosuit is installed on the back where is close to the center of mass of the human body, effectively limiting the additional metabolic cost caused by system weight. Second, rigid linkages are installed on the shoulder to provide stronger assistance torque. Third, it is snore convenient and practical to recognize the movement intension of wearer by using IMU instead of 14:MG. Finally, the system is controlled using a hierarchical strategy, where the high level control is responsible for recognizing the wearers intension and processing the data obtained from load cells and the low level control is used to control the output of motor. To evaluate the effectiveness of the exosuit on the wearer objectively, two sets of experiments are conducted. One is used to investigate the change of EMGs, the other is utilized to monitor the change of angle of arm in the sagittal plane when subjects hold different loads.The result of first experiment shows that the EMGs with exosuit varies mostly between -0.4mv and 0.8mv and without exosuit varies mostly between -1.3mv and 1.3mv when holding no load. Meanwhile the exosuit assistances the EMGs standard deviations are reduced from 0.512mv to 0.175mv, 1.555mv to 0.701mv, 2.214mv to 1.837mv, 2.852mv to 2.703mv and x-axis angle standard deviations decrease from 1.523 degrees to 0.947 degrees, 2.741 degrees to 0.268 degrees, 7.761 degrees to 0.542 degrees, 3.515 degrees to 0.960 degrees when holding the weight of 0g, 500g, 1000g and 2000g with hands. Therefore we conclude that the exosuit can provide effective assistance.