Bioinspired pneumatic muscle spring units mimicking the human motion apparatus: benefits for passive motion range and joint stiffness variation in antagonistic setups

Abstract

Pneumatic actuators have become an applicable solution for robotic movement generation in the last decades. Among them, pneumatic actuated muscles (PAMs) which are known as McKibben muscles. They clone the biological operating principle which means, that they can only contract and create tensile force. Mounted in a bioinspired agonistic-antagonistic setup (AAS) of a robotic joint, their benefits lay especially in the adjustable joint torque and stiffness. However, when mounted in an AAS, the PAMs divulge their weakness: The limited passive abilities of the PAMs enforce the AAS to be preloaded. Inspired by nature, Klute investigated a PAM with a serial elastic element and a damper to mimic the muscle tendon unit of the biological system. Based on this approach, we offer calculable AAS models and show design possibilities in this contribution.