Pneumatic bladder links with wide range of motion joints for articulated inflatable robots
Katsu Uchiyama, Ryuma Niiyama
TL;DR
This work tackles the limited joint motion of inflatable robots by introducing Hillberry rolling-contact joints and modular pneumatic bladder links, achieving a wide range of motion ($\pm 150^{\circ}$) and scalable link configurations. It provides a mathematical model of angle-dependent moment arms and forward kinematics to predict arm behavior, and demonstrates practical capabilities through 3-DoF arms: lifting up to $5$ kg with a 1-DoF configuration, $3.4$ kg with a 2-DoF configuration, 500 g end-effector manipulation, and single-leg locomotion on a dolly guided by a human operator. The results indicate a lightweight, inexpensive path to higher degrees of freedom in inflatable robots, with potential applications in space, disaster sites, and uneven terrain. The study also identifies sensing and state-estimation needs to enable autonomous control given the bladder’s compliant nature and the dynamic tendon-length changes during operation.
Abstract
Exploration of various applications is the frontier of research on inflatable robots. We proposed an articulated robots consisting of multiple pneumatic bladder links connected by rolling contact joints called Hillberry joints. The bladder link is made of a double-layered structure of tarpaulin sheet and polyurethane sheet, which is both airtight and flexible in shape. The integration of the Hilberry joint into an inflatable robot is also a new approach. The rolling contact joint allows wide range of motion of $\pm 150 ^{\circ}$, the largest among the conventional inflatable joints. Using the proposed mechanism for inflatable robots, we demonstrated moving a 500 g payload with a 3-DoF arm and lifting 3.4 kg and 5 kg payloads with 2-DoF and 1-DoF arms, respectively. We also experimented with a single 3-DoF inflatable leg attached to a dolly to show that the proposed structure worked for legged locomotion.