A new tiny, self-driving robot powered only by surrounding light or radio waves can run indefinitely on harvested power.

Small mobile robots carrying sensors could perform tasks like catching gas leaks or tracking warehouse inventory. But moving robots demands a lot of energy, and batteries, the typical power source, limit lifetime and raise environmental concerns.

Researchers have explored various alternatives: affixing sensors to insects, keeping charging mats nearby, or powering the robots with lasers. Each has drawbacks. Insects roam. Chargers limit range. Lasers can burn people’s eyes.

Researchers have now created MilliMobile, a self-driving robot that is about the size of a penny, weighs as much as a raisin, and can move about the length of a bus (30 feet, or 10 meters) in an hour even on a cloudy day.

The robot can drive on surfaces such as concrete or packed soil and carry nearly three times its own weight in equipment like a camera or sensors. It uses a light sensor to move automatically toward light sources.

“We took inspiration from ‘intermittent computing,’ which breaks complex programs into small steps, so a device with very limited power can work incrementally, as energy is available,” says co-lead author Kyle Johnson, a doctoral student in the Paul G. Allen School of Computer Science & Engineering at the University of Washington.

“With MilliMobile, we applied this concept to motion. We reduced the robot’s size and weight so it takes only a small amount of energy to move. And, similar to an animal taking steps, our robot moves in discrete increments, using small pulses of energy to turn its wheels.”

The team tested MilliMobile both indoors and outdoors, in environments such as parks, an indoor hydroponic farm, and an office. Even in very low light situations—for instance, powered only by the lights under a kitchen counter—the robots are still able to inch along, though much slower.

Running continuously, even at that pace, opens new abilities for a swarm of robots deployed in areas where other sensors have trouble generating nuanced data.

The robots are also able to steer themselves, navigating with onboard sensors and tiny computing chips. To demonstrate this, the team programmed the robots to use their onboard light sensors to move towards a light source.

“‘Internet of Things’ sensors are usually fixed in specific locations,” says co-lead author Zachary Englhardt, a doctoral student in the Allen School. “Our work crosses domains to create robotic sensors that can sample data at multiple points throughout a space to create a more detailed view of its environment, whether that’s a smart farm where the robots are tracking humidity and soil moisture, or a factory where they’re seeking out electromagnetic noise to find equipment malfunctions.”

Researchers have outfitted MilliMobile with light, temperature, and humidity sensors as well as with Bluetooth, letting it transmit data over 650 feet (200 meters). In the future, they plan to add other sensors and improve data-sharing among swarms of these robots.

The team will present its research October 2 at the ACM MobiCom 2023 conference in Madrid, Spain.

Vicente Arroyos, a doctoral student in the Allen School, is a co-lead author of the study. Dennis Yin, who completed this work as undergraduate in electrical and computer engineering, and Shwetak Patel, a professor in the Allen School and in electrical and computer engineering, are coauthors, and Vikram Iyer, assistant professor in the Allen School, is the study’s senior author.

The research received funding from an Amazon Research Award, a Google Research Scholar award, the National Science Foundation Graduate Research Fellowship Program, the National GEM Consortium, the Washington NASA Space Grant Consortium, the Pastry-Powered T(o)uring Machine Endowed Fellowship, and the SPEEA ACE fellowship program.

Source: University of Washington

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Get a bug’s eye view from a tiny ‘beetle backpack’ camera

A tiny, wireless, steerable camera that can also ride aboard an insect gives everyone a chance to see a bug’s view of the world.

The camera, which streams video to a smartphone at 1 to 5 frames per second, sits on a mechanical arm that can pivot 60 degrees. This allows a viewer to capture a high-resolution, panoramic shot or track a moving object while expending a minimal amount of energy.

“…prior to our work, wireless vision has not been possible for small robots or insects.”

To demonstrate the versatility of this system, which weighs about 250 milligrams—about one-tenth the weight of a playing card—the team mounted it on top of live beetles and insect-sized robots.

“We have created a low-power, low-weight, wireless camera system that can capture a first-person view of what’s happening from an actual live insect or create vision for small robots,” says senior author Shyam Gollakota, a associate professor in the Paul G. Allen School of Computer Science & Engineering at the University of Washington.

“Vision is so important for communication and for navigation, but it’s extremely challenging to do it at such a small scale. As a result, prior to our work, wireless vision has not been possible for small robots or insects.”

Typical small cameras, such as those used in smartphones, use a lot of power to capture wide-angle, high-resolution photos, and that doesn’t work at the insect scale. While the cameras themselves are lightweight, the batteries they need to support them make the overall system too big and heavy for insects—or insect-sized robots—to lug around. So the team took a lesson from biology.

“Similar to cameras, vision in animals requires a lot of power,” says coauthor Sawyer Fuller, an assistant professor of mechanical engineering.

“It’s less of a big deal in larger creatures like humans, but flies are using 10 to 20% of their resting energy just to power their brains, most of which is devoted to visual processing. To help cut the cost, some flies have a small, high-resolution region of their compound eyes. They turn their heads to steer where they want to see with extra clarity, such as for chasing prey or a mate. This saves power over having high resolution over their entire visual field.”

To mimic an animal’s vision, the researchers used a tiny, ultra-low-power black-and-white camera that can sweep across a field of view with the help of a mechanical arm. The arm moves when the team applies a high voltage, which makes the material bend and move the camera to the desired position.

Unless the team applies more power, the arm stays at that angle for about a minute before relaxing back to its original position. This is similar to how people can keep their head turned in one direction for only a short period of time before returning to a more neutral position.

“One advantage to being able to move the camera is that you can get a wide-angle view of what’s happening without consuming a huge amount of power,” says co-lead author Vikram Iyer, a doctoral student in electrical and computer engineering.

“We can track a moving object without having to spend the energy to move a whole robot. These images are also at a higher resolution than if we used a wide-angle lens, which would create an image with the same number of pixels divided up over a much larger area.”

“We made sure the beetles could still move properly when they were carrying our system.”

The camera and arm are controlled via Bluetooth from a smartphone from a distance up to 120 meters away, just a little longer than a football field.

The researchers attached their removable system to the backs of two different types of beetles—a death-feigning beetle and a Pinacate beetle. Similar beetles have been known to be able to carry loads heavier than half a gram, the researchers say.

“We made sure the beetles could still move properly when they were carrying our system,” says co-lead author Ali Najafi, a doctoral student in electrical and computer engineering. “They were able to navigate freely across gravel, up a slope, and even climb trees.”

The beetles also lived for at least a year after the experiment ended.

“We added a small accelerometer to our system to be able to detect when the beetle moves. Then it only captures images during that time,” Iyer says.

“If the camera is just continuously streaming without this accelerometer, we could record one to two hours before the battery died. With the accelerometer, we could record for six hours or more, depending on the beetle’s activity level.”

The researchers also used their camera system to design the world’s smallest terrestrial, power-autonomous robot with wireless vision. This insect-sized robot uses vibrations to move and consumes almost the same power as low-power Bluetooth radios need to operate.

The team found, however, that the vibrations shook the camera and produced distorted images. The researchers solved this issue by having the robot stop momentarily, take a picture and then resume its journey. With this strategy, the system was still able to move about 2 to 3 centimeters per second—faster than any other tiny robot that uses vibrations to move—and had a battery life of about 90 minutes.

“This is the first time that we’ve had a first-person view from the back of a beetle while it’s walking around.”

While the team is excited about the potential for lightweight and low-power mobile cameras, the researchers acknowledge that this technology comes with a new set of privacy risks.

“As researchers we strongly believe that it’s really important to put things in the public domain so people are aware of the risks and so people can start coming up with solutions to address them,” Gollakota says.

Applications could range from biology to exploring novel environments, the researchers say. The team hopes that future versions of the camera will require even less power and be battery free, potentially solar-powered.

“This is the first time that we’ve had a first-person view from the back of a beetle while it’s walking around. There are so many questions you could explore, such as how does the beetle respond to different stimuli that it sees in the environment?” Iyer says. “But also, insects can traverse rocky environments, which is really challenging for robots to do at this scale. So this system can also help us out by letting us see or collect samples from hard-to-navigate spaces.”

Johannes James, a UW mechanical engineering doctoral student, is also a coauthor of the paper. Funding came from a Microsoft fellowship and the National Science Foundation.

The results appear in Science Robotics.

Source: University of Washington

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Bees wearing backpacks could replace some drones

Engineers have created a sensing system small enough to ride aboard a bumble bee. The system’s tiny rechargeable battery lasts for seven hours of flight and recharges while the bees are in their hive at night.

The system could one day replace drones to soar over huge farm fields and monitor temperature, humidity, or crop health. Drones need so much power to fly they can’t get very far without needing a charge.

“Drones can fly for maybe 10 or 20 minutes before they need to charge again, whereas our bees can collect data for hours,” says senior author Shyam Gollakota, an associate professor in the Paul G. Allen School of Computer Science & Engineering at the University of Washington.

“We showed for the first time that it’s possible to actually do all this computation and sensing using insects in lieu of drones.”

7 grains of rice

While using insects instead of drones solves the power problem, the technique has its own set of complications: First, insects can’t carry much weight. And second, GPS receivers, which work well for helping drones report their positions, consume too much power for this application. To develop a sensor package that could fit on an insect and sense its location, the team had to address both issues.

“We decided to use bumble bees because they’re large enough to carry a tiny battery that can power our system, and they return to a hive every night where we could wirelessly recharge the batteries,” says coauthor Vikram Iyer, a doctoral student in the electrical & computer engineering department. “For this research we followed the best methods for care and handling of these creatures.”

Previously other research groups have fitted bumble bees with simple “backpacks” by supergluing small trackers, like radio-frequency identification, or RFID, tags, to them to follow their movement. For these types of experiments, researchers put a bee in the freezer for a few minutes to slow it down before they glue on the backpack. When they’re finished with the experiment, the team removes the backpack through a similar process.

These prior studies, however, only involved backpacks that simply tracked bees’ locations over short distances—around 10 inches—and didn’t carry anything to survey the environment around them. For this study, researchers designed a sensor backpack that rides on the bees’ backs and weighs 102 milligrams—about the weight of seven grains of uncooked rice.

“The rechargeable battery powering the backpack weighs about 70 milligrams, so we had a little over 30 milligrams left for everything else, like the sensors and the localization system to track the insect’s position,” says coauthor Rajalakshmi Nandakumar, a doctoral student in the Allen School.

‘Hey bees…’

Because bees don’t advertise where they are flying and because GPS receivers are too power-hungry to ride on a tiny insect, the team came up with a method that uses no power to localize the bees. The researchers set up multiple antennas that broadcasted signals from a base station across a specific area. A receiver in a bee’s backpack uses the strength of the signal and the angle difference between the bee and the base station to triangulate the insect’s position.

“To test the localization system, we did an experiment on a soccer field,” says coauthor Anran Wang, a doctoral student in the Allen School. “We set up our base station with four antennas on one side of the field, and then we had a bee with a backpack flying around in a jar that we moved away from the antennas. We were able to detect the bee’s position as long as it was within 80 meters, about three-quarters the length of a football field, of the antennas.”

Next the team added a series of small sensors—monitoring temperature, humidity, and light intensity—to the backpack. That way, the bees could collect data and log that information along with their location, and eventually compile information about a whole farm.

“It would be interesting to see if the bees prefer one region of the farm and visit other areas less often,” says coauthor Sawyer Fuller, an assistant professor in the mechanical engineering department. “Alternatively, if you want to know what’s happening in a particular area, you could also program the backpack to say: ‘Hey bees, if you visit this location, take a temperature reading.'”

Back at the hive

After the bees have finished their day of foraging, they return to their hive where the backpack can upload any data it collected via a method called backscatter, through which a device can share information by reflecting radio waves transmitted from a nearby antenna.

Right now the backpacks can only store about 30 kilobytes of data, so they are limited to carrying sensors that create small amounts of data. Also, the backpacks can upload data only when the bees return to the hive. The team would eventually like to develop backpacks with cameras that can livestream information about plant health back to farmers.

“Having insects carry these sensor systems could be beneficial for farms because bees can sense things that electronic objects, like drones, cannot,” Gollakota says.

“With a drone, you’re just flying around randomly, while a bee is going to be drawn to specific things, like the plants it prefers to pollinate. And on top of learning about the environment, you can also learn a lot about how the bees behave.”

The research team will present its findings online and at the ACM MobiCom 2019 conference.

Source: University of Washington

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