Pneumatic actuation-based bidirectional modules with variable stiffness and closed-loop position control

This paper extends our previous work on a pneumatic bending module and presents two more modules for rotational and translational motions. In these modules, antagonistic chambers enveloped by rigid shells are adopted to realize bidirectional actuation, and they are characterized by safe actuation, enhanced torque/force output, independent stiffness tuning, and real-time position control. Due to their mechanical modularity, they can be conveniently assembled into robotic systems with multiple degrees of freedom (DoFs) according to different requirements. A complete workflow is presented including the module design, fabrication, theoretical modelling, controller design, and experimental validation. A reconfigurable robotic arm with high dexterity is also assembled using these modules, demonstrating the effectiveness of the proposed modules to develop robotic systems for safe, forceful, and precise tasks.