Image: The Institute of Physics |
Despite their extreme flexibility and adaptability,
current soft-bodied robots are often limited by their slow speed, leading the
researchers to turn to terrestrial soft-bodied animals for inspiration.
Some caterpillars have the
extraordinary ability to rapidly curl themselves into a wheel and propel
themselves away from predators. This highly dynamic process, called ballistic
rolling, is one of the fastest wheeling behaviors in nature.
Researchers from Tufts
Univ., Massachusetts,
saw this as an opportunity to design a robot that mimics this behavior of
caterpillars and to develop a better understanding of the mechanics behind
ballistic rolling.
The study, published in Bioinspiration & Biomimetics, also includes a video of both the
caterpillar and robot in action.
To simulate the movement of a caterpillar, the
researchers designed a 10 cm long soft-bodied robot, called GoQBot, made out of
silicone rubber and actuated by embedded shape memory alloy coils. It was named
GoQBot as it forms a “Q” shape before rolling away at over half a meter per
second.
The GoQBot was designed to specifically replicate the
functional morphologies of a caterpillar, and was fitted with five infrared
emitters along it side to allow motion tracking using one of the latest high
speed 3D tracking systems. Simultaneously, a force plate measured the detailed
ground forces as the robot pushed off into a ballistic roll.
In order to change its body conformation so quickly,
in less than 100 ms, GoQBot benefits from a significant degree of mechanical
coordination in ballistic rolling. Researchers believe such coordination is
mediated by the nonlinear muscle coupling in the animals.
The researchers were also able to explain why
caterpillars don’t use the ballistic roll more often as a default mode of
transport; despite its impressive performance, ballistic rolling is only
effective on smooth surfaces, demands a large amount of power, and often ends
unpredictably.
Not only did the study provide an insight into the
fascinating escape system of a caterpillar, it also put forward a new locomotor
strategy which could be used in future robot development.
Many modern robots are modelled after snakes, worms,
and caterpillars for their talents in crawling and climbing into difficult
spaces. However, the limbless bodies severely reduce the speeds of the robots
in the opening. On the other hand, there are many robots that employ a rolling
motion in order to travel with speed and efficiency, but they struggle to gain
access to difficult spaces.
Lead author Huai-Ti Lin from the Department of
Biology, Tufts Univ., said: “GoQBot demonstrates a
solution by reconfiguring its body and could therefore enhance several robotic
applications such as urban rescue, building inspection, and environmental
monitoring.”
“Due to the increased speed and range, limbless
crawling robots with ballistic rolling capability could be deployed more
generally at a disaster site such as a tsunami aftermath. The robot can wheel
to a debris field and wiggle into the danger for us.”
