Taking inspiration from nature - particularly the agile and fast-moving insects - researchers found a way to make drones smaller and faster.
While the efficiency, movement patterns, and response time of natural beings have been notoriously difficult to emulate, Kevin Yufeng Chen, an assistant professor from the Massachusetts Institute of Technology (MIT) Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, has found a system that copies these abilities and applies them to robots.
The new aerial robots, roughly the size of small insects, now boasts unprecedented dexterity and resilience. These drones are fitted with a new class of soft actuators, allowing them to survive the physical challenges and obstacles in real-world flight. Chen hopes that the robots could be used for pollinating crops or conducting inspections in otherwise inaccessible locations.
Details of the new drone design are summarized in a report entitled "Collision Resilient Insect-Scale Soft-Actuated Aerial Robots With High Agility," published in the IEEE Transactions on Robotics. Chen's co-authors include PhD student Zhijian Ren also from MIT, PhD student Siyi Xu from Harvard University, and Pakpong Chirarattananon from the City University of Hong Kong.
Introducing a New Class of Drones
Conventional drones require wide and open spaces in order to operate properly, mainly because they are not robust enough to survive collisions or they're simply not nimble enough to evade and pass through narrow gaps - limiting their use to outdoor applications.
"If we look at most drones today, they're usually quite big," Chen says in a press release from MIT. "The question is: Can you create insect-scale robots that can move around in very complex, cluttered spaces?"
Chen acknowledges the challenge of building smaller drones, especially since the construction architecture involved in conventional drones no longer apply to their miniaturized versions. One example is motors that run drone propellers: motors lose efficiency as you scale them down, prompting Chen to find alternatives.
The leading alternative has been the use of small actuators based on piezoelectric ceramics. While it provided enough power for flight, these materials are limited by their fragility - posing a challenge for attempting to emulate insects. For example, bumblebees collecting food for the hive experience collisions almost every second.
Counterintuitive Solution
Instead of looking for hard and rigid materials, Chen turned to soft actuators made of thin rubber cylinders with a carbon nanotube finish. When voltage passes through the nanotubes, it creates an electrostatic force that squeezes the rubber cylinder, actuating it by elongation. The quick pulsing of electricity causes the cylinder to extend and retract, causing the drone wings to beat, and eventually take flight.
With this design, the new class of drones can flap about 500 times each second, which allows them to emulate the resilience of insects. He adds that you can hit the drones in flight and they still can recover, even capable of doing somersaults in mid-air. Furthermore, it only weighs about 0.6 grams, close to the mass of a large bumblebee. The new insect-inspired drone appears like "a tiny cassette tape with wings," and Chen has begun work on a dragonfly-looking drone.
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