Hyperelastic analysis of pneumatic artificial muscle with filament-wound sleeve and coated outer layer

Abstract

This paper presents the configuration and manufacturing process of a pneumatic artificial muscle (PAM) with a filament-wound sleeve and co-cured silicone outer layer. The two-parameter Mooney—Rivlin model for the bladder and outer layer is introduced into the force balance model to analyze the nonlinear behavior of this PAM. The effect of the bladder and the outer layer on the force balance model are investigated, separately. The model accuracy may be decreased by the initial contraction due to the loosing of the threads and the change of winding angle during the fabrication. A method to calibrate the initial contraction and actual winding angle is also introduced in this paper. The material properties are calculated with respect to the experimental behavior of the soft material. Five PAMs with different braiding angles (15°, 20°, and 25°) and sleeve thicknesses (0.72 and 1.28 mm) are fabricated and tested under air pressures ranging from 138 to 483 kPa. The load lines of five PAMs simulated based on the proposed method are found to be in good agreement with the experimental results. As the winding angle is a design variable of the presented PAMs, specific application Requirements can be easily achieved by assigning an appropriate value to it during the design. The force balance model is governed by several parameters, and it models the nonlinear behaviors of the PAMs with two silicone layers, over large ranges of pressures and contractions, well. The PAM can be utilized and controlled accurately using a feedback control strategy.