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.

Modeling of Resistive Forces and Buckling Behavior in Variable Recruitment Fluidic Artificial Muscle Bundles

“…where denotes the volume of the bladder. Other models take a force balance approach to model the elastic forces by analyzing the stresses developed in the bladder in the hoop and axial directions [22,23]. The mesh force derived from this approach matches the results from the virtual work balance method, as expected.…”

“…Therefore, to further improve the model to match the force from experiments, a method of force correction was developed. There are models in the literature that account for advanced effects such as the tapering effect at the ends of the FAM and the hyperelasticity of the bladder on the tensile force generation of the FAM [19,[21][22][23]. However, it is often the case that the blocked force and free strain is overpredicted even when calculated with these advanced models, due to uncertainty in the material properties or imperfections in the components used to build the bladder.…”

The Effects of Manufacturing Parameters on Static Characteristics of Water Hydraulic Artificial Muscles

“…From the model analysis, the bladder's thickness significantly influences the free contraction of PAM. Furthermore, the experimental results show that the bladder's force was positive at small contractions and increased with the working pressure [24]. The theoretical contraction force expression of ideal cylindrical artificial muscle is…”

Design, analysis, and validation of an orderly recruitment valve for bio-inspired fluidic artificial muscles

“…However, discrepancies between the experiment and simulation do exist which can be mostly attributed to the FAM model used. Although the ideal FAM model used in the study is widely used in literature due to its simplicity, it overpredicts strain values and does not take into account pressure-dependent free strain behavior Although recent models have built upon the ideal model using advanced modeling methods and empirical tuning to account for such behavior [1,15,[21][22][23][24][25], the FAM model used in this study is appropriate for the purpose of demonstrating the functionality of the ORV, as qualitative trends show a good match between the experiment and simulation as seen from figure 4.…”

“…The first stage is the required pressure estimation from equation ( 21) and second stage is the required valve input estimation. After estimating the required pressure as shown in equation ( 21), the next step is to estimate the required spool position, x v,req based on the estimated pressure and required flow rate, Q m,req as shown in equation ( 24): , (24) where Q m,req is the required flow rate from the valve and P s (t) is the supply pressure. Q m,req is estimated based on the required FAM contraction as shown in equation (25) and P s (t) is a function of hydraulic subsystem's initial states and the reference trajectory.…”