Bidirectional Double-Spring Pneumatic Artificial Muscle With Inductive Self-Sensing

This study proposes a bidirectional double-spring pneumatic artificial muscle (PAM) with inductive self-sensing for wearable robotic devices. The actuator structure, composed of commercially available latex and springs, enables a low-cost and consistent manufacturing process. Springs, which serve as the skeleton of the actuator, were used to increase the stability and stiffness of the structure, as well as to embed a self-sensing ability using the inductance of the spring. The actuator design parameters were selected through simulations to prevent buckling while achieving a notable actuation performance. The bidirectional force characteristics of the actuator were evaluated through quasi-static experiments, and the inductance-based length-sensing performance was validated during both contraction and elongation. The need for self-sensing in bidirectional actuation was emphasized through closed-loop length control. The proposed actuator can potentially enable the development of lightweight and efficient wearable robotic devices with improved sensing and actuation capabilities.