Development of a Straight Fibers Pneumatic Muscle

This paper presents the development and implementation of a pneumatic muscle actuator based on an idea proposed by a research group at the University of Warsaw. The muscle comprises a silicone rubber tube with plugs at the ends. The tube wall contains high-rigidity wires arranged parallel to the tube axis. Circular rings are present on the exterior of the tube. When air is introduced into the tube, the actuator becomes bulky and contracts. In order to establish a prediction model of muscle behavior, a finite element model was developed, and in this model, the Mooney-Rivlin formulation was implemented with two coefficients for rubber simulation and truss elements for the wires. Several prototypes were developed, and a test bench for the experimental characterization of muscle performance was set up. The results of comparison between prototype behavior and model prediction are presented. The finite element model can be used to design the actuator with different dimensions; hence, it was used to conduct a simulated test campaign to develop a quick actuator sizing procedure. Using dimensional analysis, few project parameters were identified on which the performance of the actuator depends. Through a complete simulation campaign using the finite element model, an abacus was constructed. It allows sizing the actuator as required based on the desired performances according to an established procedure.