Tubular Shaped (Continuum) Soft Robotic Arm with Variable Stiffness: Design, Fabrication, and Testing

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The Ohio State University

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Soft robots are designed to be highly flexible and adaptable to their surroundings. Often times conventional rigid robots are at a disadvantage due to lack of versatility in complex environments and safety concerns on human-robot interactions. Soft robots can be compliantly designed to overcome those limitations at the expense of lower precision and reduced load capacity. To improve the precision and weight carrying capability, this research built a compliant robotic arm of tunable stiffness by using layer jamming technique. Most of continuum and compliant robotic arm designs have a center backbone, which connects the subsections and provides the majority of the stiffness. However, the center backbone takes large internal space of the robotic arm which could be used for wiring and sensor/gadget placement. This research project provided a tubular shaped solution by redesigning the backbone and placing the compliant backbone at the perimeter of each tubular subsection, thus leaving large space available inside the robotic arm. With the novel body design and the incorporation of layer jamming, the arm is able to pass through complex environment to reach target locations with its compliant body, that contains 3 subsections with 90 degrees maximum bending angle on each. Stiffness can be tuned up to 87 times higher in high stiffness mode (12.5psi vacuum pressure) than its natural state (0psi). This robotic arm is able to eliminate or reduce impact injury in its low stiffness mode and perform accurately while carrying large load in its high stiffness mode. The features of this robotic arm give benefit in minimal invasive surgery and rescue robotics applications.