Characterisation of a phenomenological model for commercial pneumatic muscle actuators

Abstract

This study focuses on the parameter characterisation of a three-element phenomenological model for commercially available pneumatic muscle actuators (PMAs). This model consists of a spring, damping and contractile element arranged in parallel. Data collected from static loading, contraction and relaxation experiments were fitted to theoretical solutions of the governing equation for the three-element model resulting in prediction profiles for the spring, damping and contractile force coefficient. For the spring coefficient, K N/mm, the following relationships were found: K = 32.7 − 0.0321P for 150 ≤ P ≤ 314 kPa and K = 17 + 0.0179P for 314 ≤ P ≤ 550 kPa. For the damping coefficient, B Ns/mm, the following relationship was found during contraction: B = 2.90 for 150 ≤ P ≤ 550 kPa. During relaxation, B = 1.57 for 150 ≤ P ≤ 372 kPa and B = 0.311 + 0.00338P for 372 ≤ P ≤ 550. The following relationship for the contractile force coefficient, F _ce N, was also determined: F _ce = 2.91P+44.6 for 150 ≤ P ≤ 550 kPa. The model was then validated by reasonably predicting the response of the PMA to a triangular wave input in pressure under a constant load on a dynamic test station.

Keywords:

• parameter characterisation
• biomimetic
• commercial
• pneumatic muscle
• actuator
• dynamic model

Acknowledgements

Research was funded in part by NSF Grant no. DGE-0504438; IGERT: An Interdisciplinary Initiative on Technology-based Learning with Disability.