초소형 비행 로봇 ‘로보비 엑스-윙’ VIDEO: The RoboBee flies solo—Cutting the power cord for the first untethered flight
The RoboBee flies solo—Cutting the power cord for the first untethered flight
by Harvard John A. Paulson School of Engineering and Applied Sciences
The RoboBee X-wing has four wings driven by two piezoelectric actuators. The vehicle has a total wingspan of 3.4 cm, weighs 90 mg, and has a maximum lift of 370mg. Credit: Noah T. Jafferis and E. Farrell Helbling, Harvard Microrobotics Laboratory
The RoboBee X-WingIt was developed by a team from Harvard University in Boston. It has a wingspan of 3.5 centimetres and weighs only 259 milligrams, light enough to land on leaves. The solar-powered RoboBee X-WingIt and has four wings which flap at a rate of 170 times per second, instead of a propeller to take off./dailymail.uk.com
초소형 비행 로봇 ‘로보비 엑스-윙’ 태양전지, 4개의 날개로 장거리 비행 성공 15세기 레오나르도 다빈치는 동물이 사람에게 영감을 준다고 말했다. 실제로 많은 과학자들이 동물의 모습을 모방해 기계나 기구를 제작해왔다. 그리고 지금 꿀벌의 날개를 모방해 비행이 가능한 초소형 날개를 제작하는데 성공하고 있다. 26일 ‘하버드 공대(Harvard John A. Paulson School of Engineering and Applied Sciences)’ 연구팀은 종이 클립의 절반에 불과하면서 장기간 비행이 가능한 초소형 비행체를 완성했다는 내용의 논문을 ‘네이처’ 지에 발표했다. 스타워즈 ‘엑스-윙 스타파이터’ 참조 논문에 따르면 이 로봇은 2013년 하버드대 로버트 우드(Robert Wood) 교수팀이 개발한 무게 로봇을 업그레이드 한 것이다. 우드 교수팀이 선보인 파리 모습의 로봇은 무게 80mg으로 초당 120회의 날갯짓을 할 수 있었다. 그러나 이 로봇에 탑재할 초소형 배터리가 없어 몸체에 전선을 연결해 전기를 공급했다. 그 결과 비행 거리가 약 10cm에 불과했다. 그러나 이번에 선보인 로봇의 무게는 259mg, 각 날개의 길이는 3.5cm에 달한다. 이전보다 몸체가 커졌지만 태양전지를 부착하고 있으며, 2개의 기본 날개 외에 2개의 보조 날개가 달려 있어 기류 상의 방해가 없는 한 무한정 장거리 비행이 가능하다. 기능을 첨가하면서 명칭도 과거 ‘로보비(RoboBee)’에서 ‘로보비 엑스-윙(RoboBee X-Wing)’으로 개명했다. 연구를 이끈 노아 자페리스(Noah T. Jafferis) 박사는 “이전의 로보비의 단점을 보강하기 위해 장착한 초소형 태양전지의 무게는 10mg에 불과하며, 밝은 태양 아래서 120mw(milliwatt)의 전력 생산이 가능하다.”고 말했다. 연구팀은 현재 태양전지가 지속적으로 가동하기 위해 매우 밝은 할로겐 라이트로 태양빛을 대체하고 있는 중이다. 로보비를 선보인 우드 교수는 이번 연구 결과에 대해 “수십 년 동안의 노력으로 오랜 비행이 가능한 초소형 비행체를 완성할 수 있었다.”며, “향후 추가 연구를 통해 더 작으면서 더 강력하고 지속적인 비행 능력을 지닌 초소형 비행체를 개발해나가겠다.”고 말했다. 논문은 26일자 ‘네이처’ 지에 게재됐다. 논문 제목은 ‘Untethered flight of an insect-sized flapping-wing microscale aerial vehicle’이다. “초소형 비행체 개발 분기점 넘었다” 연구팀은 논문을 통해 공기보다 무거운 비행체는 많은 에너지를 공급해야 하기 때문에 제작이 어려운 데다 많은 비용이 들어간다고 말했다.
하버드 공대에서 개발한 ‘엑스-윙 스타파이터’. 259mg의 무게로 장거리 비행에 성공해 향후 초소형 로못비행체 개발의 초석을 놓은 것으로 평가받고 있다. ⓒseas.harvard.edu 더구나 5cm 이하 곤충 크기의 초소형 비행체인 경우 상업적으로 배터리 생산이 이루어지지 않는 데다 배터리를 제작하기 위해 정교한 기술이 요구돼 에너지 공급 문제를 해결하는 데 더 큰 곤란을 겪어왔다고 털어놓았다. 연구팀은 이 문제를 해결하기 위해 다양한 모델을 통해 실험을 진행해왔다고 밝혔다. 강화 알루미늄을 소재로 만든 압전기(alumina-reinforced piezoelectric actuators) 2대와 4개의 날개를 장착한 259mg의 비행체를 제작했다는 것. 이 로봇은 2개의 날개를 지닌 비행체와 비교해 30% 에너지를 절약할 수 있었다. 연구팀은 수차례의 실험을 통해 110~120mw의 전력으로 꿀벌 크기의 로봇이 비행할 수 있게 됐다고 말했다. 한편 초소형 로봇 개발은 1970년대 미국 정보기관에서 시작됐다. 당시에는 전쟁 포로 구출을 돕거나 전자 교란 업무를 맡기려고 했으나, 기술 부족으로 실제 제작할 수는 없었다. 이후 1980년대 후반 미세전자기계시스템(MEMS)을 이용해 마이크로 로봇을 만들 수 있게 되면서 관련 기술에 대한 관심이 다시 높아졌다. 1993년 엡손에서 만들어 판매한 초소형 자율 주행 로봇 ‘므슈’는 1㎤밖에 안 되는 몸에 98개의 부품을 담고 있었다. 비행 로봇 역시 꾸준하게 이루어졌다. 특히 미국, 중국 간의 개발 경쟁이 치열하게 전개돼왔는데 이번에 하버드대에서 장거리 실험에 성공하면서 개발 경쟁에 새 국면을 맞게 됐다. 이강봉 객원기자baacc409@naver.com sciencetimes |
edited by kcontents
The RoboBee—the insect-inspired microrobot developed by researchers at Harvard University—has become the lightest vehicle ever to achieve sustained flight without the assistance of a power cord. After decades of work, the researchers achieved untethered flight by making several important changes to the RoboBee, including the addition of a second pair of wings. That change, along with less visible changes to the actuators and transmission ratio, gave the RoboBee enough lift for the researchers to attach solar cells and an electronics panel.
In the Harvard Microrobotics Lab, on a late afternoon in August, decades of research culminated in a moment of stress as the tiny, groundbreaking Robobee made its first solo flight.
Graduate student Elizabeth Farrell Helbling, Ph.D. '19, and postdoctoral fellow Noah T. Jafferis from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Graduate School of Arts and Sciences and The Wyss Institute for Biologically Inspired Engineering caught the moment on camera.
Helbling, who has worked on the project for six years, counted down.
"Three, two, one, go."
The bright halogens switched on and the solar-powered Robobee launched into the air. For a terrifying second, the tiny robot, still without on-board steering and control, careened towards the lights.
Off camera, Helbling exclaimed and cut the power. The Robobee fell dead out of the air, caught by its Kevlar safety harness.
"That went really close to me," Helbling said, with a nervous laugh.
"It went up," Jafferis, who has also worked on the project for about six years, responded excitedly from the high-speed camera monitor where he was recording the test.
And with that, Harvard University's Robobee reached its latest major milestone—becoming the lightest vehicle ever to achieve sustained untethered flight.
Changes to the Robobee -- including an additional pair of wings and improvements to the actuators and transmission ratio -- made the vehicle more efficient and allowed the addition of solar cells and an electronics panel. This Robobee is the first to fly without a power cord and is the lightest, untethered vehicle to achieve sustained flight. Credit: Harvard Microrobotics Lab/Harvard SEAS
"This is a result several decades in the making," said Robert Wood, Charles River Professor of Engineering and Applied Sciences at SEAS, Core Faculty member of the Wyss Institute and principle investigator of the Robobee project. "Powering flight is something of a Catch-22 as the tradeoff between mass and power becomes extremely problematic at small scales where flight is inherently inefficient. It doesn't help that even the smallest commercially available batteries weigh much more than the robot. We have developed strategies to address this challenge by increasing vehicle efficiency, creating extremely lightweight power circuits, and integrating high efficiency solar cells."
The milestone is described in Nature.
To achieve untethered flight, this latest iteration of the Robobee underwent several important changes, including the addition of a second pair of wings.
"The change from two to four wings, along with less visible changes to the actuator and transmission ratio, made the vehicle more efficient, gave it more lift, and allowed us to put everything we need on-board without using more power," said Jafferis.
Changes to the Robobee -- including an additional pair of wings and improvements to the actuators and transmission ratio -- made the vehicle more efficient and allowed the addition of solar cells and an electronics panel. This Robobee is the first to fly without a power cord and is the lightest, untethered vehicle to achieve sustained flight. Credit: Harvard Microrobotics Lab/Harvard SEAS
That extra lift, with no additional power requirements, allowed the researchers to cut the power cord—which has kept the Robobee tethered for nearly a decade—and attach solar cells and an electronics panel to the vehicle.
The solar cells, the smallest commercially available, weigh 10 milligrams each and get 0.76 milliwatts per milligram of power when the sun is at full intensity. The Robobee X-Wing needs the power of about three Earth suns to fly, making outdoor flight out of reach for now. Instead, the researchers simulate that level of sunlight in the lab with halogen lights.
The solar cells are connected to an electronics panel under the bee, which converts the low voltage signals of the solar array into high voltage drive signals needed to control the actuators. The solar cells sit about three centimeters above the wings, to avoid interference.
via youtube
edited by kcontents
To achieve untethered flight, the latest iteration of the Robobee underwent several important changes, including the addition of a second pair of wings. Credit: Harvard SEAS
In all, the final vehicle, with the solar cells and electronics, weights 259 milligrams (about a quarter of a paper clip) and uses about 120 milliwatts of power, which is less power than it would take to light a single bulb on a string of LED Christmas lights.
"When you see engineering in movies, if something doesn't work, people hack at it once or twice and suddenly it works. Real science isn't like that," said Helbling. "We hacked at this problem in every which way to finally achieve what we did. In the end, it's pretty thrilling."
The researchers will continue to hack away, aiming to bring down the power and add on-board control to enable the Robobee to fly outside.
"Over the life of this project we have sequentially developed solutions to challenging problems, like how to build complex devices at millimeter scales, how to create high-performance millimeter-scale artificial muscles, bioinspired designs, and novel sensors, and flight control strategies," said Wood. "Now that power solutions are emerging, the next step is onboard control. Beyond these robots, we are excited that these underlying technologies are finding applications in other areas such as minimally-invasive surgical devices, wearable sensors, assistive robots, and haptic communication devices—to name just a few."
https://techxplore.com/news/2019-06-robobee-flies-solocutting-power-cord.html
