A Review and Comparison of Linear Pneumatic Artificial Muscles

For mechanical systems where a human-machine interface or interaction is necessary, it is important to consider physical safety. In cases where robots and humans must coexist, these robots must have actuation that is inherently compliant to absorb physical impacts. However, these compliant actuators must possess high performance that is comparable with electro-mechanical actuators. Pneumatic artificial muscles (PAMs) are biologically inspired actuators that possess inherent compliance and are a prime candidate for implementation in future robotic applications. This article reviews several designs of contractile PAMs made from various materials and where the actuator may need to be pressurized, depressurized, or vacuumed to produce mechanical work. Although these PAMs are all physically compliant due to the inherent compressibility of air, their performance varies significantly from one design to the other such that it may be hard to identify a suitable actuator for a given application. This paper covers a broad range of contractile PAM designs and compares their performance based on a few metrics in order to help users determine which actuators have the most potential for future implementations. The paper also identifies a few areas where significant challenges will have to be solved for these new actuators to help pave the way for a world where robots can operate in close proximity to humans.