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 while still able to fly effectively.
The artificial muscles have been optimised so that the robot can better isolate defects and overcome minor damage, such as tiny holes in its actuators.
A novel laser-repair method was also developed to help the robot recover from severe damage, such as a fire that scorches the device.
Using their techniques, a damaged robot was able to maintain flight-level performance after one of its artificial muscles was jabbed by 10 needles, while the actuator was able to operate even after a large hole was burnt into it. The repair methods enabled a robot to keep flying even after the researchers cut off 20 per cent of its wing tip.
This could make swarms of tiny robots better able to perform tasks in tough environments, such as conducting a search mission through a collapsing building or dense forest, the researchers said.
“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,” said Kevin Chen, senior author on the research.
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.
Microscopic imperfections can cause sparks that burn the elastomer and cause the device to fail. The researchers employed a technique known as “self-clearing” which applies high voltage to the DEA to disconnect a local electrode around a small defect, isolating that failure from the rest of the electrode.
For major defects, the team used a laser to carefully cut along the outer contours of the damaged area. They then used self-clearing to burn off the slightly damaged electrode, isolating the larger defect.
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 per cent of its performance.
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