MECHANICAL ENGINEER
Balloon Animal Robots
About the Project
Balloon Animal Robots are a new class of reconfigurable soft robots inspired by balloon animals. The system uses a single inflated tube and a collection of small, identical node robots that can drive along the tube, cinch it to create joints, and pull themselves together using cable-driven actuation. These simple operations allow the robot to change both its geometry and topology, forming structures ranging from trusses to quadrupeds with the same hardware.The concept takes inspiration from balloon twisting by creating pinch points to define joints and folding the balloon into a new shape. This research was presented at IROS 2021 and explores both the mechanical design of the robot and a graph-theoretic algorithm to plan reconfigurable structures.
My Role
As the lead author on this project, I was responsible for the mechanical design, fabrication, and experimental validation of the system. I designed and built all of the hardware components for the node robots, including the drive system, cinch mechanism, and cable actuation. I also led the setup and execution of the force and torque characterization experiments that informed the design. To bring the concept to life, I built a working prototype capable of reconfiguring into multiple shapes using a small set of node robots and string connections. Beyond the technical work, I authored the paper and presented the research at IROS 2021, sharing the project with the international robotics community.
Design Overview
The system is built around two main components:
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Inflated Tube: A thin-walled, fabric-reinforced tube pressurized to 34.5 kPa that serves as the robot’s main structural backbone.
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Node Robots: Modular, identical units capable of:
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Driving along the tube using motorized rollers
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Cinching the tube to create low-stiffness joints
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Pulling themselves toward other nodes via motorized winches and cables
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Each node can move, create or remove joints, and actuate connections, which allows the structure to be reconfigured without disassembly or onboard pumps.
Mechanical Design Highlights
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Drive System
Uses six rollers in a triangular arrangement for high friction and stable motion. One motorized roller drives the robot along the tube. -
Cinch Mechanism
A motorized winch with a worm gear tightens a loop around the tube, reducing local bending stiffness and defining a joint location. The worm gear allows the cinch to hold its position without continuous power. Cinch diameter directly controls joint stiffness. -
Cable Actuation
Nodes are connected with cables that can be pulled via winches, bringing nodes together to fold the structure. Worm gear drives lock the shape without continuous power.
Reconfiguration Algorithm
A graph-based algorithm was developed to find the minimum number of nodes and string connections needed to realize multiple goal topologies from a single inflated tube. The algorithm uses Eulerian path analysis to ensure physically constructible layouts and minimizes mechanical complexity. This approach allows the same hardware to form several different structures.
Results
This work was published as a peer-reviewed conference paper and presented at the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2021. The prototype successfully demonstrated that a small set of simple node robots can reconfigure a single inflated tube into multiple distinct 2D topologies without disassembly. The system formed four different shapes to validate the underlying design and reconfiguration approach. This was a proof of concept that can be built on and improved in future research.
The link to the full paper can be found here:
