Dynamic Characterization and Phenomenological Modelling of Customizable Pneumatic Artificial Muscle

Pneumatic Artificial Muscles (PAMs) are gaining popularity over traditional actuators in applications where the requirement are high force density, low mass, biological muscle like characteristics, etc,. Especially in applications related to Human Robot Interactions and wearable active devices, these actuators are considered much safe due to their light weight when compared to their commercial counterparts. However their usage are limited, due to their inherent nonlinearities, which poses challenges in their accurate force and position control. The article focuses on dynamic characterization of an in-house fabricated PAM using a three-element lumped phenomenological model. The model consists of a spring element, contractile force element and a damper element arranged in parallel. Pressure perturbation experiments have been conducted to identify the parameters in the governing equations for the spring coefficient, damping coefficient and the contractile element force. Finally, the developed model has been validated by reasonably predicting the displacement response of the PAM to a triangular pressure input pulse when subjected to a constant load on a dynamic test rig.