Fully flexible wearable pouch pneumatic artificial muscle based on asymmetric expansion

Abstract

Pneumatic artificial muscle (PAM) is the core actuating component in wearable devices and soft robots. It typically incorporates rigid elements to enhance actuation performance, leading to reduced wear comfort and even additional energy metabolism. Additionally, the significant radial expansion of the PAM can lead to it compressing against the human body. This paper introduces a fully flexible wearable pouch pneumatic artificial muscle based on asymmetric expansion (AEPAM). Using a weaving structure, the expansion center of the airbag is offset from the traction axis, resulting in the AEPAM exhibiting radial asymmetric expansion. At a low air pressure of 70 kPa, it achieves a contraction rate of 51.09% and a contraction force of 243.94 N. When the load is increased to 5 kg, the contraction rate of AEPAM can still reach 29.69%. The AEPAM unit is exceptionally lightweight, weighing only 9.04 g, with a contraction force-to-weight ratio of approximately 27,100 N/kg. In the extrusion force experiment, AEPAM maintains the wear-side extrusion force within 10 N, effectively avoiding additional compression produced when the wearable actuator operates, achieving an 89.61% reduction compared to the rectangular pouch PAM. Finally, preliminary testing confirms that the muscle activation of the biceps can be reduced by 41.82% during unloaded elbow flexion movements. When carrying a 3 kg load, the muscle activation is reduced by 33.64%.