Dynamic Characterization and Phenomenological Modeling of Sleeve Pneumatic Artificial Muscles

Abstract

Pneumatic artificial muscles (PAMs) are a compelling actuator for physical human–robot interaction (pHRI) due to their low mass, high-force capacity, and muscle-like characteristics. However, their low efficiency and bandwidth have forced mobile robotics researchers to examine alternative actuators for performing dynamic tasks like walking and grasping. Recently, the sleeve PAM, has been proposed and shown to improve the efficiency and force capacity when compared with traditional PAM designs. However, the increase in the dynamic performance of sleeve PAMs has not yet been studied. The aim of this research is to compare the dynamic performance of sleeve and traditional PAMS, and to develop a phenomenological model of their dynamic performance. Testing found that the isometric bandwidth of sleeve muscles can be 100% greater than that of traditional muscles at rest length if pressure response is considered, although this improvement decreases with contraction. If force is instead considered, the increase in bandwidth is even greater (up to 120% greater than that of a traditional PAM). The volume of both PAMs was determined using an experimental method, and a phenomenological model was fitted. When these models were used to simulate the performance of a PAM-actuated system, it was shown that both approximate the behavior of the measured system with good accuracy. Finally, a proposed implementation is given which illustrates how the benefits of the sleeved PAM actuator design could be realized in a practical robotics application.