One of the main challenges in microrobotics is equipping the robots to autonomously maneuver and avoid obstructions. However, researchers from the Harvard Microrobotics Laboratory at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have instead taken the opposite direction by building robots that can withstand collisions without sustaining damage. The RoboBee is powered by soft actuators and is the first microrobot of its kind to achieve controlled flight.
Soft actuators can be assembled and replaced easily in small-scale robots, according to Yufeng Chen, a former graduate student and postdoctoral fellow at SEAS, as well as the first author of the paper.
“There has been a big push in the field of microrobotics to make mobile robots out of soft actuators because they are so resilient,” Chen said. “However, many people in the field have been skeptical that they could be used for flying robots because the power density of those actuators simply hasn’t been high enough and they are notoriously difficult to control. Our actuator has high enough power density and controllability to achieve hovering flight.”
To address the challenges in power density, the team improved the electrode conductivity on the soft actuators. This allowed them to operate the actuator at 500 Hz, which is alike to the rigid actuators used in similar robots.
Another challenge with soft actuators is their tendency to become unstable. To prevent this, the researchers built a lightweight airframe with a piece of vertical constraining thread to keep it from buckling.
Several models of the RoboBee were built to demonstrate its various flight capabilities. A two-wing model was able to takeoff from the ground but had limited to no additional control. On the other hand, a four-wing, two-actuator model was able to navigate a cluttered environment and overcome multiple collisions in a single flight. An eight-wing, four-actuator model was also able to exhibit controlled hovering flight, which was a first for a soft-powered flying microrobot.
The researchers expressed the advantages of their technology in real-life applications, particularly in search-and-rescue operations.
“One advantage of small-scale, low-mass robots is their resilience to external impacts,” said Elizabeth Farrell Helbling, a former graduate student at SEAS and coauthor on the paper. “The soft actuator provides an additional benefit because it can absorb impact better than traditional actuation strategies. This would come in handy in potential applications such as flying through rubble for search and rescue missions.”
The researchers are working on increasing the efficiency of their robots which, while offering a unique solution, still lag behind traditional flying robots.
“Soft actuators with muscle-like properties and electrical activation represent a grand challenge in robotics,” said Robert Wood, Charles River Professor of Engineering and Applied Sciences in SEAS, core faculty member of the Wyss Institute for Biologically Inspired Engineering and senior author of the paper. “If we could engineer high-performance artificial muscles, the sky is the limit for what robots we could build.”
The research is published in Nature.
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