Multi-Modal Pneumatic Actuator for Twisting, Extension, and Bending

Soft pneumatic actuators are commonly used in robotics for creating single-axis compression, extension, or bending motions. If these actuators are composed of compliant materials, they can also have low off-axis stiffnesses, making it difficult to restrict off-axis motions. In this work, we exploit the low off-axis stiffnesses of pneumatic actuators to design a modular actuator system that is capable of multi-modal extension, compression, two-axis bending, and twisting motions. By combining physical constraint mechanisms and motion planning, we demonstrate closed loop control with up to 24 mm of compression, 70 mm of extension, 115 degrees of bending, and 240 degrees of twisting. This actuator system is then used to illustrate several unique applications including twisting for unscrewing bottle caps and peristaltic crawling for locomotion.