Abstract
A robot driven by McKibben pneumatic actuator (MPA) generates stable motions in spite of its simple control and simple actuator model. In this paper, we investigate a relation between the design of a robot driven by MPA and the joint stiffness, based on mechanical analysis and simulation. After deriving a singular point of the joint stiffness, we confirm that qualitative relation between input pressure and the joint stiffness is reversed where the hip position is higher than the singular point. Moreover, we analyze the influence of MPA properties and geometric parameters on the singular point. From the results, we confirm that the significant posture disappear by increasing the radius of the knee-pulley. Finally, we verify the validity of these analytical results via numerical simulations.
