Sometimes bigger is not better. Researchers have developed tiny flying robots that are agile and resistant to collisions. Their insect-sized drones with soft, muscle-like actuators can expand the repertoire of flying robots, enabling them to operate in confined spaces and withstand collisions.
Insects can be remarkably acrobatic and resilient in flight. These properties help them to find their way around the air world with all its gusts of wind, obstacles and general uncertainties. Such properties are also difficult to build into flying robots, but MIT Assistant Professor Kevin Yufeng Chen has developed a system that approximates the mobility of insects.
Chen, a member of the Electrical and Computer Science Department and Electronics Research Laboratory, has developed insect-sized drones with unparalleled dexterity and resilience.
The flying robots are powered by a new class of soft actuators that enable them to withstand the physical difficulties of real flight. Chen hopes that one day the robots could help people by pollinating plants or performing machine inspections in confined spaces.
The study was published in the journal IEEE Transactions on Robotics.
Usually, drones require large open spaces, as they are neither nimble enough to navigate in tight spaces, nor robust enough to withstand collisions in a crowd. “If we look at most of the drones today, they’re usually pretty big,” says Chen. “Most of its uses include flying in the open air. The question is, can you create insect-scale robots that can move around in very complex, crowded spaces?”
According to Chen, “the challenge of building small flying robots is immense.” Pint-sized drones require a fundamentally different design than larger ones. Large drones are usually powered by motors, but motors lose efficiency as you downsize them. Chen says that for insect-like robots “one has to look for alternatives”.
So far, the main alternative has been to use a small, rigid actuator made from piezoelectric ceramic materials. While piezoelectric ceramics made it possible for the first generation of tiny robots to fly, they are quite fragile. And that’s a problem when you’re building a robot that mimics an insect – bumblebees looking for bumblebees get a collision about once every second.
Chen designed a more resilient tiny drone with soft actuators instead of hard, fragile ones. The soft actuators consist of thin rubber cylinders coated with carbon nanotubes. When voltage is applied to the carbon nanotubes, they generate an electrostatic force that compresses and elongates the blanket cylinder. Repeated stretching and contraction causes the drone’s wings to flap quickly.
Chen’s actuators can flutter nearly 500 times per second, giving the drone an insect-like resilience. “You can hit it when it flies and it can recover,” says Chen. “It can also perform aggressive maneuvers like somersaults in the air.” And it only weighs 0.6 grams, roughly the mass of a large bumblebee. The drone looks a bit like a tiny cassette with wings, although Chen is working on a new prototype that is shaped like a dragonfly.
The construction of insect-like robots offers an insight into the biology and physics of insect flight, a long-standing research path for researchers. Chen’s work addresses these issues through a kind of reverse engineering. “If you want to learn how insects fly, building a full-scale robot model is very educational,” he says. “You can perturb a few things and see how this affects the kinematics or how the fluid forces change. That helps you understand how these things fly.” However, Chen wants to add more than just entomology textbooks. Its drones can also be useful in industry and agriculture.
According to Chen, his mini aerialists could control complex machines to ensure safety and functionality. “Think about inspecting a turbine engine. You want a drone to move [an enclosed space] with a small camera to check the turbine plates for cracks. “Other possible uses are artificial pollination of plants or carrying out search and rescue missions after a disaster.