A Portable Exoskeleton Driven by Pneumatic Artificial Muscles for Upper Limb Motion Replication

This paper proposes a portable exoskeleton to assist patients suffering from upper limb dysfunction in their activities of daily livings (ADLs) independently. While therapies assisting patients with bi-manual activities, the exoskeleton is able to record trajectory and replicate motion. It is driven by pneumatic artificial muscles (PAMs) with 4 actuated DOFs (degrees of freedom) including 1 passive DOF. The total weight of the exoskeleton is only 5.6 kilograms, which makes it possible to wear it for a long period. At the medial/lateral rotation of shoulder joint and flexion-extension of the elbow joint, pairs of PAMs are used to imitate antagonistic muscles. Only one PAM is utilized to control each of shoulder flexion-extension and abduction-adduction, whose positions can be adjusted according to patient's weight. A kinematic model is built to simulate the trajectory in 3-D space, which is verified by the comparison of the simulated results with the experimental implementations. We have tested the function of motion replication on a platform and the value of error is within the tolerance. The future improvement of the device involves adding springs to cooperate with the single actuated PAM and modified control strategy to adapt to users' physical conditions.