Architectures of soft pneumatic actuators inspired by muscle fiber arrangements

Architectures or networks are prevalent in both engineered and nature's material systems, where a single unit cell is topologically combined in a repeatable fashion to attain extremal global properties. In this paper, we work towards understanding one such architecture inspired by pennation, which is commonly found in skeletal muscles to tailor its stroke and force properties. To mimic muscle fibers, we use soft compliant pneumatic actuators called Fiber Reinforced Elastomeric Enclosures (FREEs) to generate force and stroke. The FREEs are combined in a dyadic configuration to create an engineered equivalent of pennate muscles called a pennate building block (PBB). The study of the PBB reveals critical pennate angles that produce high stroke and force values respectively. The PBB thus acts as an equivalent of a gear and other transmission elements in soft robotics. Lastly, two variant of the pennate architecture are analyzed for their force deformation capabilities and the results are used to design and experimentally validate two prototypes geared towards different applications thereby highlighting the benefits of leveraging architectures for tuning global properties.