A caterpillar curls its head into its body at the sight of a predator. Researchers have been examining the diverse behaviours of caterpillars to find solutions for the new generation of search and rescue soft robots.
Credit: iStockPhoto
SYDNEY: Drawing inspiration from caterpillars that rapidly curl their bodies to roll away from predators, researchers have created a new soft-bodied robot that can travel faster than half-a-metre per second.
The 10-centimetre-long robot, called GoQBot, has a hammer-shaped head and a soft silicone body embedded with metal coils that contract like muscles when stimulated. This allows the flat crawler to reconfigure its body into a round 'Q' shape and quickly propel itself forward.
By simulating this novel escape behaviour known as ballistic rolling, the soft-bodied robot is faster and could be more usefully deployed in search and rescue-type operations on flat ground, said lead author Huai-Ti Lin, a biomechanical engineer from Tufts University near Boston.
"Most small robots have an operation range limit, so the rescuers must attempt to deploy the robot as close to the locations of interest as possible," Lin said. "Ballistic rolling capability offers the robots an extended range so they can be deployed more generally at a site... We believe that such mode of locomotion can greatly enhance the performances of soft robots."
Soft-bodied robots limited by speed
A major reason why soft-bodied robots are modelled after limbless organisms like snakes and worms is because they are well adapted to accessing hard-to-reach places by crawling, climbing and burrowing.
Despite these advantages, they have traditionally been limited by their slow speeds, a result of many coordinated joints. Conversely, robots that roll are often too bulky to gain access to narrow spaces.
Crawling robots like GoQBot that can morph their soft, flexible bodies into round wheels for faster locomotion offer a balanced solution. "The robot can wheel to a debris field and wiggle into the danger for us," said Lin.
Robots are also considered highly effective search and rescue tools because, unlike humans, they can withstand severe conditions such as high radiation levels and are ultimately disposable at the end of their lifespan.
Muscle coordination sparks roll
According to the paper published in Bioinspiration & Biomimetics this week, GoQBot was designed to help researchers learn more about the mechanics of ballistic rolling, which is one of the fastest wheeling behaviours in nature.
The laterally elongated head acts as an anchor from which the rest of the body generates thrust, curling its abdomen into the shape of a 'Q' when stimulated by an electric current and moving forward with angular momentum.
This curling reconfiguration takes place in roughly 200 milliseconds, and is enabled by mechanical coordination between the front and rear muscles of the robot, similar to the non-linear muscle coupling in caterpillars.
But researchers say caterpillars don't use the roll as a default mode of travel because it requires a lot of energy, often ends unpredictably, and only works on smooth surfaces.
Challenges facing bio-inspired robots
Jaime Valls Miro, a lecturer in mobile robotics at the University of Technology, Sydney, said the research demonstrates an interesting bio-inspired feature to speed up the motion of limbless crawling robots.
But being able to move serves a limited purpose for search and rescue, he said. "The goal is to go to places to do something, for example finding people, mapping new environments, sniffing for gases or touching materials. For that, specific sensorial payloads need to be part of the robot."
"This research, like many others looking at novel motion strategies, tends to limit their research at the locomotion aspects of the robot."
Researchers will now try to refine this crawler tuned cart wheeler. While it can peel out at high speeds, it can only reach a maximum distance of 25 cm. In addition, there is the problem of reverting back to the crawling position and reorienting itself after rolling.
