Analysis of mode bifurcation between McKibben pneumatic actuators in the antagonist musculoskeletal model

Abstract

This study focused on the bifurcation of coordination relationships between McKibben pneumatic actuators (MPA). We aimed to arrive at the control theory of a robot with MPAs by analyzing this bifurcation phenomena. The control law using the MPA tension generates multiple motion modes, and the coordination relationships between MPAs bifurcate depending on parameters reported in a previous study. The bifurcation phenomenon between two of those coordination relationships was analyzed and it was found that despite a similar link movement, the phase oscillators exhibited different coupled modes. The important difference between two coupled modes was determined to be the relationship between the MPA pressure and length. Further, we verified that the angular velocity of the link was the parameter that generated this phenomenon by analyzing it in correspondence with the model of forced oscillation. In addition, we confirmed the bifurcation phenomenon employing a 1-DOF pendulum machine.