Evaluating the Applicability of Analytical Models for Silicone Tube Mckibben Actuators through Soft Computing

Pneumatic artificial muscles are highly compliant actuators closely resembling the human muscles and are mainly used in bio-mimicking applications nowadays due to their high power to weight ratio. Although most of the biomimetic systems have utilized commercially available Mckibben type pneumatic artificial muscle actuators, customized actuators are necessary to specifically meet the force-contraction-actuation pressure demands. This article discusses such an actuator built of hyperelastic silicone material to reduce the actuation pressure, necessary for untethered systems. Although several analytical models have been validated for the commercial actuators, it is important to investigate their applications to the ones developed in-house. Starting off by equating the force-contraction output work with the pressure-volume input energy, the analysis slowly takes into consideration the strain energy stored in the hyperelastic silicone tube material. The material model for silicone has been chosen carefully through uniaxial tensile tests conducted in laboratory. The article discusses the development as well as static performance characterization of a set of total nine such actuators having three levels of length and diameter each. Finally, appropriate correction factors have been introduced, optimized through a soft-computing technique along with the discussion of their dependencies on design parameters as well as operating pressures. Finally, a modified formulation specifically for such grades of customizable actuators has been presented.