Hybrid nonlinear model of McKibben pneumatic artificial muscle systems incorporating a pressure-dependent Coulomb friction coefficient

This study presents a more precise hybrid nonlinear model of pneumatic artificial muscle (PAM) systems actuated by a proportional directional control valve and confirms the validity of the presented model using various commercial PAMs. To enhance the precision, the Coulomb friction coefficient was incorporated as a function of the PAM inner-pressure. To evaluate the contribution of the modification to the modeling of PAM behavior, the authors determine whether the parameters are effectively observed, whether precision of the model is improved, and whether the model is applicable to various commercial PAM products from ActiveLink and FESTO. Furthermore, this study investigates the impacts on time responses and parameters when the temperature increases from 293 to 313 K. In addition to investigations concerning the validity, the authors show that the achievement of this study is an extension of the previously proposed nonlinear PAM model.