Folding Under Pressure

When selecting a robot for a new use case, the first major choice will be between a soft or rigid body. Soft robots are extremely flexible, which allows them to fit into tight spaces and adapt to changing conditions. However, while they excel in flexibility, they are lacking in strength. Rigid robots, on the other hand, can be exceptionally strong, but they are unable to bend their form to meet the demands of changing environments.

Neither of these choices provides applications that require both flexibility and strength with a suitable option. In an effort to better accommodate these situations, a group of engineers at the Shenyang Institute of Automation has developed a new type of robot that combines both soft and rigid elements. This gives it the best of both worlds in many respects — it can be flexible when needed, but it is also capable of lifting heavy loads like a traditional rigid robot.

How it works

The team’s creation was inspired by origami, the ancient Japanese art of folding paper. Robots built using their technique consist of a joint module made from a deployable origami exoskeleton and three inflatable airbags. The exoskeleton provides structural reinforcement and torsional resistance, while the airbags act as soft actuators that drive motion. This pairing allows the robot to maintain flexibility without compromising strength.

The origami structure itself consists of an upper platform, a lower platform, and six parallel waterbomb origami folds. When pressurized, the airbags expand or contract, moving the exoskeleton and enabling the arm to extend, bend, or twist with a high degree of precision. By independently controlling the three airbags, the robot achieves multiple degrees of freedom, making it suitable for fairly complex manipulation tasks.

Performance and potential applications

In testing, the soft arm demonstrated a cargo-loading capacity well beyond what traditional soft robots can achieve. It successfully supported loads of at least 5 kilograms during bending, extension, and contraction, all while maintaining stability. The arm was also capable of bending more than 240 degrees and contracting to less than one-third of its length, with a contraction ratio surpassing 300%. It was also found that the system displayed bistable characteristics, meaning that it remains stable in both fully extended and fully contracted states without continuous energy input.

Potential applications for this hybrid design range widely. In aerospace, for example, it could be deployed for turbine maintenance, where delicate maneuvering and the ability to handle substantial tools or components are both required. Similar opportunities exist in manufacturing, inspection, and medical robotics.