For robots to be useful for real-world applications, they must be safe around humans, be adaptable to their environment, and operate in an untethered manner. Soft robots could potentially meet these requirements; however, existing soft robotic architectures are limited by their ability to scale to human sizes and operate at these scales without a tether to transmit power or pressurized air from an external source. Here, we report an untethered, inflated robotic truss, composed of thin-walled inflatable tubes, capable of shape change by continuously relocating its joints, while its total edge length remains constant. Specifically, a set of identical roller modules each pinch the tube to create an effective joint that separates two edges, and modules can be connected to form complex structures. Driving a roller module along a tube changes the overall shape, lengthening one edge and shortening another, while the total edge length and hence fluid volume remain constant. This isoperimetric behavior allows the robot to operate without compressing air or requiring a tether. Our concept brings together advantages from three distinct types of robots—soft, collective, and truss-based—while overcoming certain limitations of each. Our robots are robust and safe, like soft robots, but not limited by a tether; are modular, like collective robots, but not limited by complex subunits; and are shape-changing, like truss robots, but not limited by rigid linear actuators. We demonstrate two-dimensional (2D) robots capable of shape change and a human-scale 3D robot capable of punctuated rolling locomotion and manipulation, all constructed with the same modular rollers and operating without a tether.
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An untethered soft cellular robot with variable volume, friction, and unit-to-unit cohesion
A fundamental challenge in the field of modular and collective robots is balancing the trade-off between unit- level simplicity, which allows scalability, and unit-level function- ality, which allows meaningful behaviors of the collective. At the same time, a challenge in the field of soft robotics is creating untethered systems, especially at a large scale with many controlled degrees of freedom (DOF). As a contribution toward addressing these challenges, here we present an untethered, soft cellular robot unit. A single unit is simple and one DOF, yet can increase its volume by 8x and apply substantial forces to the environment, can modulate its surface friction, and can switch its unit-to-unit cohesion while agnostic to unit-to- unit orientation. As a soft robot, it is robust and can achieve untethered operation of its DOF. We present the design of the unit, a volumetric actuator with a perforated strain-limiting fabric skin embedded with magnets surrounding an elastomeric membrane, which in turn encompasses a low-cost micro-pump, battery, and control electronics. We model and test this unit and show simple demonstrations of three-unit configurations that lift, crawl, and perform plate manipulation. Our untethered, soft cellular robot unit lays the foundation for new robust soft robotic collectives that have the potential to apply human-scale forces to the world.
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- Award ID(s):
- 1925373
- NSF-PAR ID:
- 10186621
- Date Published:
- Journal Name:
- Proceedings of the IEEERSJ International Conference on Intelligent Robots and Systems
- ISSN:
- 2153-0858
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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