Slider-Tendon Linear Actuator With Under-Actuation and Fast-Connection for Soft Wearable Robots

Tendon-driven soft wearable robots should be simple, compact, and safe because they are worn on the human body and interact directly with the human. Here, unlike rigid robots, wire pre-tension should be removed at the end-effector due to the inherent characteristics of the soft robot. In this article, for a stable and compact actuation system without pretension, a linear actuator called a slider-tendon linear actuator is proposed. The proposed actuator is designed to make a linear motion using a tendon, as compared to other linear transmissions, such as ball screw or lead screw transmissions. By using the proposed design method that uses a tendon, the actuator size was reduced to 23.6% of the size of an actuator that uses a ball screw; this is because the tendon can endure high tensile force with a small cross-section area. Furthermore, this article proposes a robot design methodology to locate the robot mechanism in the actuator, rather than in the end-effector. The proposed actuator is designed to contain a fast-connection and stroke-amplified under-actuation mechanism. In the proposed method, not only is the complexity and size of the worn part reduced, but its performance is also improved. Finally, by applying this actuator to a specific wearable robot, this paper verifies that the proposed actuator sufficiently satisfies the requirements of the wearable robot.