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Harvard Launches Robot Moth

A robotic tobacco hawkmoth joins Harvard's collection of artificial insects

2 min read
Harvard robot moth
Image: Harvard Microrobotics Laboratory

Harvard researchers have been working on their robot bee for a really, really long time (in robot years). It’s impressively small, being bee-sized, but it turns out that it’s so small that it’s not realistic to expect it to fly with onboard power and computing in the near future. Plus, the flight dynamics of tiny insects like bees is significantly different from larger insects like butterflies and moths, which exhibit combinations of flapping, gliding, and soaring flight. To explore this, Harvard researchers have developed FWMAV, a novel insect-scale flapping-wing micro-air vehicle that’s just small enough to be called “micro” and just big enough to operate completely untethered.

The video makes it look like FWMAV has some trouble staying aloft, but the researchers told us that it can keep a stable altitude by flapping between 70 percent and 80 percent of the time. The wings are delicate, though, and when this particular clip was filmed (after 30 or 40 flight tests), the robot was a little bit beat up and wasn’t at peak efficiency.

FWMAV has a wingspan of 16 centimeters, and weighs just over 3 grams (almost half of which is the motor). It’s fully untethered, with onboard power, communication, and control systems. In overall dimensions and performance, it’s analogous to the tobacco hawkmoth. Flapping at 25 Hz, it can average about 4 g of thrust, more than enough to keep it airborne. The flapping action itself is generated by a folded carbon fiber transmission that converts the rotary motion of the motor into up and down motion of the wings, which are designed to flex over a 90 degree range to vary their angle of attack and improve aerodynamics in the same way that real insect wings do.

harvard robot moth A 3D model of the robot used for simulation. Image: Harvard Microrobotics Laboratory

The most obvious departure from the bioinspired design is in the tail, which is far more airplane-like than moth-like and required to keep the robot stable in yaw and roll. Real moths can do this using independent control of each of their wings, but since FWMAV doesn’t have this capability (yet), the tail is necessary. It also can’t take off by itself, and needs to be launched by catapult.

Relative to RoboBee, which can take off and hover and steer (and was learning to swim), FWMAV might seem a little primitive, but this paper represents just the first hardware validation. Researchers are already planning aerodynamic improvements, tail actuation, and a redesign to allow independent control over each wing. They’re also looking forward to taking the robot outside of the motion capture area that it’s currently restricted to, with the goal of closed-loop flight in bigger, more open areas.

“Development of a 3.2g Untethered Flapping-Wing Platform for Flight Energetics and Control Experiments,” by Michelle H. Rosen, Geoffroy le Pivain, Ranjana Sahai, Noah T. Jafferis, and Robert J. Wood from the Harvard Microrobotics Laboratory, was presented this week at ICRA 2016 in Stockholm, Sweden.

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Robot with threads near a fallen branch

RoMan, the Army Research Laboratory's robotic manipulator, considers the best way to grasp and move a tree branch at the Adelphi Laboratory Center, in Maryland.

Evan Ackerman
LightGreen

This article is part of our special report on AI, “The Great AI Reckoning.

"I should probably not be standing this close," I think to myself, as the robot slowly approaches a large tree branch on the floor in front of me. It's not the size of the branch that makes me nervous—it's that the robot is operating autonomously, and that while I know what it's supposed to do, I'm not entirely sure what it will do. If everything works the way the roboticists at the U.S. Army Research Laboratory (ARL) in Adelphi, Md., expect, the robot will identify the branch, grasp it, and drag it out of the way. These folks know what they're doing, but I've spent enough time around robots that I take a small step backwards anyway.

The robot, named RoMan, for Robotic Manipulator, is about the size of a large lawn mower, with a tracked base that helps it handle most kinds of terrain. At the front, it has a squat torso equipped with cameras and depth sensors, as well as a pair of arms that were harvested from a prototype disaster-response robot originally developed at NASA's Jet Propulsion Laboratory for a DARPA robotics competition. RoMan's job today is roadway clearing, a multistep task that ARL wants the robot to complete as autonomously as possible. Instead of instructing the robot to grasp specific objects in specific ways and move them to specific places, the operators tell RoMan to "go clear a path." It's then up to the robot to make all the decisions necessary to achieve that objective.

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