Tiny, agile drones

Insects’ acrobatic and resilient flight traits help them navigate wind gusts, obstacles, and general uncertainty. Such traits are hard to build into flying robots, but Massachusetts Institute of Technology (MIT) Assistant Professor Kevin Yufeng Chen built a system that approaches insect agility.

Chen, a member of the Department of Electrical Engineering and Computer Science and the Research Laboratory of Electronics, developed insect-sized drones with dexterity and resilience.

Typically, large drones aren’t nimble enough to navigate confined spaces nor robust enough to withstand collisions. Tiny drones require a different construction from larger ones, since motors lose efficiency as they’re miniaturized. For insect-like robots, the principal alternative has been a small, rigid actuator built from piezoelectric ceramic materials. While piezoelectric ceramics allowed the first generation of tiny robots to take flight, they’re extremely fragile – a problem when building a robot to mimic a foraging bumblebee that endures a collision about once every second.

Chen designed a more resilient tiny drone using a new class of soft actuators instead of hard, enabling the aerial robots to withstand the physical struggles of real-world flight. The soft actuators are made of thin rubber cylinders coated in carbon nanotubes. When voltage is applied, the carbon nanotubes produce an electrostatic force that squeezes and elongates the rubber cylinder. Repeated elongation and contraction cause the drone’s wings to beat rapidly.

Chen’s actuators flap nearly 500x per second, giving the drone insect-like resilience. “You can hit it when it’s flying, and it can recover,” Chen says. “It can also perform somersaults in the air.”

The current prototype weighs 0.6g, approximately the mass of a large bumble bee. Chen is working on a new model shaped like a dragonfly. A key step will be untethering the drone from a wired power source, which is currently required by the actuators’ high operating voltage.

Chen says his mini-aerialists could navigate complex machinery to ensure safety and functionality.

“Think about the inspection of a turbine engine. You’d want a drone to move around [an enclosed space] with a small camera to check for cracks on the turbine plates.”

Other potential applications include artificial pollination of crops or completing search-and-rescue missions following a disaster. “All those things can be very challenging for existing large-scale robots.”

Massachusetts Institute of Technology (MIT)

Chen’s work, “Collision Resilient Insect-Scale Soft-Actuated Aerial Robots with High Agility,” appears in the journal IEEE Transactions on Robotics. Co-authors include MIT Ph.D. student Zhijian Ren, Harvard University Ph.D. student Siyi Xu, and City University of Hong Kong roboticist Pakpong Chirarattananon.