Relationship between the shape of the elliptical knee joint and jumping height in a leg-type robot driven by pneumatic artificial muscle

The McKibben pneumatic actuator (MPA) is a soft actuator used for performing various practical functions in robots. Particularly, many dynamic robots have been realized using MPAs. However, there is a trade-off between torque generated by MPA and the range of motion of the joint. In this study, we focus on the jumping motion of a leg-type robot and use an elliptical pulley whose moment arm changes depending on the robot’s posture. To confirm the effectiveness of the elliptical pulley, the relationship between the knee joint pulley (patella) shape and jumping height was analyzed by simulation, and the shape of the patella maximizing jumping height was determined. It was shown that an elongated elliptical patella shape is more effective for the jumping motion than a circular one. Furthermore, the effectiveness of the analytically determined patella shape was confirmed by experiments using an actual robot.