Resilient bug-sized robots keep flying even after wing damage
New repair techniques enable microscale robots to recover flight
performance after suffering severe damage to the artificial muscles that power their wings.

Date:
March 15, 2023
Source:
Massachusetts Institute of Technology
Summary:
Researchers have developed resilient artificial muscles that can
enable insect-scale aerial robots to effectively recover flight
performance after suffering severe damage.


Facebook Twitter Pinterest LinkedIN Email
FULL STORY ========================================================================== Bumblebees are clumsy fliers. It is estimated that a foraging bee
bumps into a flower about once per second, which damages its wings
over time. Yet despite having many tiny rips or holes in their wings, bumblebees can still fly.


========================================================================== Aerial robots, on the other hand, are not so resilient. Poke holes in
the robot's wing motors or chop off part of its propellor, and odds are
pretty good it will be grounded.

Inspired by the hardiness of bumblebees, MIT researchers have developed
repair techniques that enable a bug-sized aerial robot to sustain severe
damage to the actuators, or artificial muscles, that power its wings --
but to still fly effectively.

They optimized these artificial muscles so the robot can better isolate
defects and overcome minor damage, like tiny holes in the actuator. In addition, they demonstrated a novel laser repair method that can help the
robot recover from severe damage, such as a fire that scorches the device.

Using their techniques, a damaged robot could maintain flight-level
performance after one of its artificial muscles was jabbed by 10 needles,
and the actuator was still able to operate after a large hole was burnt
into it. Their repair methods enabled a robot to keep flying even after
the researchers cut off 20 percent of its wing tip.

This could make swarms of tiny robots better able to perform tasks in
tough environments, like conducting a search mission through a collapsing building or dense forest.

"We spent a lot of time understanding the dynamics of soft,
artificial muscles and, through both a new fabrication method and a
new understanding, we can show a level of resilience to damage that is comparable to insects. We're very excited about this. But the insects
are still superior to us, in the sense that they can lose up to 40
percent of their wing and still fly. We still have some catch-up work
to do," says Kevin Chen, the D. Reid Weedon, Jr. Assistant Professor in
the Department of Electrical Engineering and Computer Science (EECS),
the head of the Soft and Micro Robotics Laboratory in the Research
Laboratory of Electronics (RLE), and the senior author of the paper on
these latest advances.

Chen wrote the paper with co-lead authors and EECS graduate students Suhan
Kim and Yi-Hsuan Hsiao; Younghoon Lee, a postdoc; Weikun "Spencer" Zhu,
a graduate student in the Department of Chemical Engineering; Zhijian
Ren, an EECS graduate student; and Farnaz Niroui, the EE Landsman
Career Development Assistant Professor of EECS at MIT and a member of
the RLE. The article will appear in Science Robotics.

Robot repair techniques The tiny, rectangular robots being developed in
Chen's lab are about the same size and shape as a microcassette tape,
though one robot weighs barely more than a paper clip. Wings on each
corner are powered by dielectric elastomer actuators (DEAs), which are
soft artificial muscles that use mechanical forces to rapidly flap the
wings. These artificial muscles are made from layers of elastomer that
are sandwiched between two razor-thin electrodes and then rolled into a
squishy tube. When voltage is applied to the DEA, the electrodes squeeze
the elastomer, which flaps the wing.

But microscopic imperfections can cause sparks that burn the elastomer and cause the device to fail. About 15 years ago, researchers found they could prevent DEA failures from one tiny defect using a physical phenomenon
known as self-clearing. In this process, applying high voltage to the
DEA disconnects the local electrode around a small defect, isolating
that failure from the rest of the electrode so the artificial muscle
still works.

Chen and his collaborators employed this self-clearing process in their
robot repair techniques.

First, they optimized the concentration of carbon nanotubes that comprise
the electrodes in the DEA. Carbon nanotubes are super-strong but extremely
tiny rolls of carbon. Having fewer carbon nanotubes in the electrode
improves self- clearing, since it reaches higher temperatures and burns
away more easily. But this also reduces the actuator's power density.

"At a certain point, you will not be able to get enough energy out of
the system, but we need a lot of energy and power to fly the robot. We
had to find the optimal point between these two constraints -- optimize
the self-clearing property under the constraint that we still want the
robot to fly," Chen says.

However, even an optimized DEA will fail if it suffers from severe damage,
like a large hole that lets too much air into the device.

Chen and his team used a laser to overcome major defects. They carefully
cut along the outer contours of a large defect with a laser, which causes
minor damage around the perimeter. Then, they can use self-clearing to
burn off the slightly damaged electrode, isolating the larger defect.

"In a way, we are trying to do surgery on muscles. But if we don't use
enough power, then we can't do enough damage to isolate the defect. On
the other hand, if we use too much power, the laser will cause severe
damage to the actuator that won't be clearable," Chen says.

The team soon realized that, when "operating" on such tiny devices, it is
very difficult to observe the electrode to see if they had successfully isolated a defect. Drawing on previous work, they incorporated electroluminescent particles into the actuator. Now, if they see light
shining, they know that part of the actuator is operational, but dark
patches mean they successfully isolated those areas.

Flight test success Once they had perfected their techniques, the
researchers conducted tests with damaged actuators -- some had been
jabbed by many needles while other had holes burned into them. They
measured how well the robot performed in flapping wing, take-off, and
hovering experiments.

Even with damaged DEAs, the repair techniques enabled the robot to
maintain its flight performance, with altitude, position, and attitude
errors that deviated only very slightly from those of an undamaged
robot. With laser surgery, a DEA that would have been broken beyond
repair was able to recover 87 percent of its performance.

"I have to hand it to my two students, who did a lot of hard work when
they were flying the robot. Flying the robot by itself is very hard,
not to mention now that we are intentionally damaging it," Chen says.

These repair techniques make the tiny robots much more robust, so Chen
and his team are now working on teaching them new functions, like landing
on flowers or flying in a swarm. They are also developing new control algorithms so the robots can fly better, teaching the robots to control
their yaw angle so they can keep a constant heading, and enabling the
robots to carry a tiny circuit, with the longer-term goal of carrying
its own power source.

This work is funded, in part, by the National Science Foundation (NSF)
and a MathWorks Fellowship.

* RELATED_TOPICS
o Matter_&_Energy
# Robotics_Research # Engineering #
Engineering_and_Construction # Vehicles
o Computers_&_Math
# Robotics # Artificial_Intelligence # Computer_Science
# Distributed_Computing
* RELATED_TERMS
o Nanorobotics o Robot o Humanoid_robot o Industrial_robot
o Aerial_photography o Robotic_surgery o Scale_model o
Absolute_zero

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Adam
Zewe. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Resilient_bug-sized_robot ========================================================================== Journal Reference:
1. Suhan Kim, Yi-Hsuan Hsiao, Younghoon Lee, Weikun Zhu, Zhijian
Ren, Farnaz
Niroui, Yufeng Chen. Laser-assisted failure recovery for dielectric
elastomer actuators in aerial robots. Science Robotics, 2023; 8
(76) DOI: 10.1126/scirobotics.adf4278 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230315143816.htm

--- up 1 year, 2 weeks, 2 days, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)