Modeling torque-angle hysteresis in a pneumatic muscle manipulator

Hysteresis is inherently present in Pneumatic Artificial Muscle (PAM) Actuators. Our new observation shows that the hysteresis in a PAM is characterized by quasirate independency and history dependency, and is completely described by the Maxwell-slip (MS) model. In this paper, we explain how to model the existing hysteresis in an antagonistic PAM configuration, using the models derived for the individual PAMs. Experimental results show that the pneumatic manipulator hysteresis has the same behaviors as those found in a single PAM. The proposed model is used to predict the output torque of the manipulator joint not only for any arbitrary angular displacements but also for any arbitrary pressure difference.