This study developed a hybrid pneumatic joint by combining a soft pneumatic-driven origami chamber and a rigid frame with a fixed rotational axis. The hybrid joint appropriately limited the excessive compliance, which was a drawback of existing inflatable joints, and was able to maintain high torque and control accuracy over a wide range of motion. This was expanded into a meter-scale hybrid robot manipulator, which stably performed pick-and-place tasks of heavy objects such as fruit.

The objective of this study is the development of a hybrid joint with a hard/soft combined structure that compensates for the drawbacks of existing pneumatic-driven inflatable joints, such as excessive compliance and high control difficulty. This joint has the advantage that deformation is predictable due to the origami structure, it can operate under both positive and negative pressure without the chamber shape collapsing through the use of facet reinforcement, and excessive expansion of the chamber can be prevented through the use of internal constraint. Additionally, the origami chamber, when combined with a rigid frame, allows the use of general rotational angle measurement sensors such as rotary encoders or potentiometers. The origami chamber was made of tarpaulin, a type of functional fabric, and combined with a 3D-printed frame to form the hybrid joint.

Unlike existing pneumatic-based joints, the joint developed in this study has the advantage of being capable of bidirectional actuation by alternating positive/negative pressure in a single chamber, and bidirectional, antagonistic actuation can also be realized by placing two origami chambers facing each other. Furthermore, by applying opposing pressures to the antagonistic chambers, a type of cooperation between chambers that significantly enhances the joint’s torque is possible, which can generate twice the torque of the original at the same chamber pressure limit.

Finally, the developed hybrid joints were configured into a 3-degree-of-freedom hybrid manipulator. This robotic arm showed excellent range of motion even under applied payload and, based on compliance, operated normally even under external shocks, demonstrating a well-blended result of the advantages of soft robots and rigid-body-based robots. Furthermore, it repeatedly performed the task of receiving fruit over 1kg from a user and placing it into a fixed basket without issue, proving its applicability to everyday human tasks.

※ Paper Title: Hybrid Hard-Soft Robotic Joint and Robotic Arm Based on Pneumatic Origami Chambers

※ Journal: IEEE/ASME Transactions on Mechatronics

※ DOI: https://doi.org/10.1109/TMECH.2024.3411629

※ Research Portal(Pure): https://pure.skku.edu/en/persons/hugo-rodrigue