Abstract
Modelling the behaviour of Pneumatic Artificial Muscle (PAM) has proven difficult due to its highly complicated structure, nonlinear nature of rubbery material, and air compressibility. To overcome these limitations, a FEM (Finite Element Method) model using Abaqus and CATIA is derived for the quantitative analysis on the impact of different factors on the pulling force of PAM. In the Abaqus a two parameter Mooney–Rivlin model is utilized to consider the hyper-elastic nature of flexible material. Then both Abaqus and CATIA are used in the parametric design of a 3-Dimensional model of PAM. Furthermore, the FEM model is employed to predict the static force exerted by PAM and the results show that the model is promising. The FEM model produces closer results to the test data for the typical PAM. Nonlinear behaviour of PAM is found to be obvious with an increase in both the contraction and the air pressure, different from the linear curves obtained by the fundamental geometrical model. Nonlinear changes in the PAM force are also observed in the numerical study on the effect of structural factors including initial braid angle, initial diameter, initial wall thickness, and flexible material. Besides, these phenomena can be explained by a connection between mechanical and morphological behaviour of PAMs with the FEM model. Generally, this modelling approach is more accurate compared to the fundamental theoretical model and more cost competitive compared to the empirical methods.
Highlights
Introduction e Pneumatic Arti cialMuscle (PAM), sometimes termed as the McKibben Pneumatic Arti cial Muscle, has been widely applied in wearable robots and rehabilitation exoskeletons for its compact structure, inherent compliance, and low price [1,2,3]
The simulation results show that the deviation from the experimental results remains almost the same with an average deviation rate at −9.9%. ese results indicate that the Finite Element Model (FEM) model is more accurate and robust since the complicated structure and the nonlinear material of rubber are taken into account. erefore, it can be employed to predict the e ect of di erent factors on the behaviour of PAM
In order to understand the effect of different impact factors on the characteristics of PAMs required in the optimal design and usage of PAMs, we propose a FEM model with the combination of Abaqus and CATIA considering how the braided threads are embedded in the rubber tube as well as the hyper-elastic model for the rubber tube. e FEM model is employed to analyze the effect of air pressure and contraction ratio on the actuator force of a typical PAM and the simulation results are compared with the theoretical results and experimental results
Summary
Muscle (PAM), sometimes termed as the McKibben Pneumatic Arti cial Muscle, has been widely applied in wearable robots and rehabilitation exoskeletons for its compact structure, inherent compliance, and low price [1,2,3]. It consists of a cylindrical exible tube, braided mesh shell, and two end caps [4, 5]. The study on the impact factors for the force exerted by PAM is rarely addressed, which encumbers the optimal design of it. A systematic survey on the impact factors for the exerted force is vital for the optimal design of PAMs
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