Numerical modelling and experimental validation of a McKibben pneumatic muscle actuator

The McKibben muscle belongs to the type of muscles known as braided muscles. It is made of an inner hyper-elastic tube, surrounded by a braided shell made of inextensible threads; both ends provide mechanical and pneumatic seal. A finite element model of a McKibben pneumatic muscle was built and experimentally validated. The model is based on characteristic parameters of McKibben muscles. It takes into account the non-linearity of the constitutive material of the inner tube. It does not simulate backslashes between the tube and the shell at rest condition, but it models threads and rubber that are always connected. However, it does not consider friction among threads. In order to build and to validate the proposed numerical model, an experimental prototype of the muscle was designed and built. Both isotonic and isometric tests were carried out. Same tests were simulated in the finite element environment. The model validation was performed by comparison between experimental and numerical results.