A Survey on Static Modeling of Miniaturized Pneumatic Artificial Muscles With New Model and Experimental Results

Pneumatic artificial muscles (PAMs) are linear pneumatic actuators consisting of a flexible bladder with a set of in-extensible fibers woven as a sheath on the outside. Upon application of pressure, the actuators contract or expand based on the angle of winding of the braid. Due to the similarity in properties of the actuators with biological muscles and the advantages thereof, these are increasingly being used in many robotic systems and mechanisms. This necessitates the development of mathematical models describing their mechanics for optimal design as well as for application in control systems. This paper presents a survey on different mathematical models described in the literature for representing the statics of PAM. Since it is observed that the validity of existing static models, based on energy balance methods, is not consistent with changes in parameters when applied to their miniaturized versions of pneumatic artificial muscles (MPAM), a new model has been proposed. The model takes into account material properties of the bladder as well as the end-effects which are prominent for MPAMs. Experiments conducted on fabricated MPAMs, of different diameters and lengths, show that the proposed model predicts the pressure-deformation characteristics of MPAMs with maximum error of less than 7%.