Folded-Tube Soft Pneumatic Actuators for Bending.

Area of Science:

• Robotics
• Materials Science
• Mechanical Engineering

Background:

• Soft pneumatic actuators (SPAs) offer compliant and adaptable actuation.
• Existing SPA designs often face limitations in strain, force generation, and bending control.

Purpose of the Study:

• To introduce a new class of bending SPAs constructed from a single section of flexible tubing.
• To model and experimentally validate the performance of these novel SPAs.

Main Methods:

• Fabrication of SPAs by creasing thin-walled flexible tubing into folds and inserting them through slits in a high-strength fabric.
• Pressurization of the folded-tube actuators to induce inflation and bending.
• Experimental characterization of three SPAs with varying fold spacings to measure tension and bending moments.

Main Results:

• The novel SPAs bend in a constant-length arc due to fabric constraint.
• Membrane reinforcement in the tubing walls enables large motions with limited material strain.
• The strongest actuator generated >190 N tension and ~10 Nm bending moment at 60 kPa, maintaining ~5.7 Nm after 160° bending.
• A presented model accurately predicted actuator performance with <13% average absolute error.

Conclusions:

• The developed SPAs demonstrate efficient actuation with large bending angles and minimal strain.
• Fold spacing is a key parameter for tuning the bending moment of these actuators.
• The proposed model provides a reliable method for predicting the behavior of these novel bending SPAs.