Self-Sensing Pneumatic Artificial Muscle with Unilateral Expansion and High Contraction Ratio for Wearable Robotics

Abstract

Pneumatic artificial muscles is widely used in robots and rehabilitation devices, but it is difficult to achieve both high contraction ratio and wearing comfort. In order to solve this problem, we propose a kind of pneumatic artificial muscle with unilateral expansion and high contraction ratio(UEPAM). The UEPAM is composed of a bending layer, several folding balloons, and 3D printed flatbeds, which can be fabricated simply by laser cutting and 3D printing. The static experimental results show that the maximum shrinkage of UEPAM can reach 69% under 15N load. The dynamic experimental results show that the artificial muscle has good position tracking ability for 0.5Hz sinusoidal signal with the maximum displacement error of 1.2 cm when closed-loop control is adopted. More importantly, due to the limitation of 3D printing rigid parts, UEPAM can only expand on one side during inflation, which makes it more suitable to be arranged in soft wearable devices without squeezing the wearer's skin. In addition, we integrate a resistive sensor based on bending measurement to sense shrinkage and displacement by measuring the bending degree of the actuator's bending layer. The experimental results show that the sensor has good accuracy and repeatability.