Evaluating the effectiveness of an active strap for wearable robot: A Mechanical and Physiological Study

Straps are the most commonly used elements in the wearable robotic field, where it is employed as a physical human robot interface (pHRI) between the wearable robot and wearer's body. The main role of the strap is to transmit power from the robot to the wearer by pressing and attaching onto specific body parts to reduce the relative motion. To maximize the efficiency and performance using the appropriate function, a high stiffness and tension is required in the strap. However, the continuous force applied by the strap on the wearer's body is one of the main factors that reduces the wearing comfort of the wearable robot. In this paper, an active strap applied to a hip orthosis is proposed to restrict the hip joint angle. The active strap was periodically controlled using the hip joint angle of the orthosis and was only tightened when the hip joint angle reached the target hip joint angle. The experimental results were then used to evaluate the performance of the proposed strap from a mechanical and physiological point of view. The results suggest that active strap is capable of effectively performing the tasks of a hip orthosis during periodic movement, demonstrating its potential use in wearable robots. Furthermore, the physiological response observed at the contact area during periodic strap tension can relieve discomfort caused by prolonged tension, thus enhancing the comfort of the wearable robot.