A new type of four-legged swarming robot can autonomously respond to distress signals from partners before joining together to help overcome environmental challenges.
The collective behaviour of animals such as ants, honeybees and birds inspired developer Yasemin Ozkan-Aydin, assistant professor of electrical engineering at the University of Notre Dame in Indiana.
“When ants collect or transport objects, if one comes upon an obstacle, the group works collectively to overcome that obstacle. If there’s a gap in the path, for example, they will form a bridge so the other ants can travel across — and that is the inspiration for this study,” she said. “Through robotics we’re able to gain a better understanding of the dynamics and collective behaviours of these biological systems and explore how we might be able to use this kind of technology in the future.”
Legged robots can navigate challenging environments such as rough terrain and tight spaces, she said, enabling rapid manoeuvrability and obstacle crossing. They can struggle in real outdoor environments, however.
For the study, Ozkan-Aydin hypothesised that a physical connection between individual robots could enhance overall mobility. Individual robots performed simple or small tasks such as moving over a smooth surface or carrying a light object, but if the task was beyond the capability of the single unit, the robots physically connected to each other to form a larger multi-legged system and collectively overcome issues.
Using a 3D printer, Ozkan-Aydin built four-legged robots measuring 15-20cm in length. Each was equipped with a lithium polymer battery, microcontroller and three sensors — a light sensor at the front, and two magnetic touch sensors at the front and back, allowing the robots to connect to one another. Four flexible legs reduced the need for additional sensors and parts, and gave the robots a level of mechanical intelligence, which helped when interacting with rough or uneven terrain.
“You don’t need additional sensors to detect obstacles because the flexibility in the legs helps the robot to move right past them,” said Ozkan-Aydin. “They can test for gaps in a path, building a bridge with their bodies; move objects individually; or connect to move objects collectively in different types of environments, not dissimilar to ants.”
Working during the Covid-19 pandemic, Ozkan-Aydin tested the robots over grass, mulch, insulation foam, shag carpet, wooden boards and other surfaces while working from home. When an individual unit became stuck, a signal was sent to the other robots, which linked together to provide support and successfully traverse obstacles.
The work could inform the design of low-cost adaptive swarms for cooperative tasks such as search-and-rescue, environmental monitoring and even space exploration, Ozkan-Aydin claimed.
Further research will focus on improving control, sensing and power capabilities, which are essential for real-world locomotion and problem-solving. Ozkan-Aydin also plans to use the system to explore the collective dynamics of insects such as ants and termites.
“For functional swarm systems, the battery technology needs to be improved,” she said. “We need small batteries that can provide more power, ideally lasting more than 10 hours. Otherwise, using this type of system in the real world isn’t sustainable.”
She added: “You need to think about how the robots would function in the real world, so you need to think about how much power is required, the size of the battery you use. Everything is limited, so you need to make decisions with every part of the machine.
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