In the very early hours of the morning, in a Harvard robotics laboratory, an insect called a RoboBee took flight achieving vertical take-off, hovering and steering.
Half the size of a paperclip, weighing less than a tenth of a gram, it leapt a few centimetres, hovered for a moment on fragile, flapping wings and then sped along a pre-set route through the air.
Like a proud parent watching a child take its first steps, graduate student Pakpong Chirarattananon immediately captured a video of the fledgling and emailed it to his adviser and colleagues at 3 am—subject line, ‘Flight of the RoboBee’.
“I was so excited, I couldn’t sleep,” recalls Chirarattananon, co-lead author of a paper published in Science.
The demonstration of the first controlled flight of an insect-sized robot is the culmination of more than a decade’s work, led by researchers at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard.
“This is what I have been trying to do for literally the last 12 years,” says Robert J Wood, Charles River Professor of Engineering and Applied Sciences at SEAS, Wyss Core Faculty Member and principal investigator of the National Science Foundation-supported RoboBee project.
“It’s really only because of this lab’s recent breakthroughs in manufacturing, materials and design that we have even been able to try this. And it just worked, spectacularly well.”
Inspired by the biology of a fly, with submillimetre-scale anatomy and two wafer-thin wings that flap almost invisibly, 120 times per second, the tiny device not only represents the absolute cutting edge of micromanufacturing and control systems, it is an aspiration that has impelled innovation in these fields by dozens of researchers across Harvard for years.
“We had to develop solutions from scratch, for everything,” explains Wood. “We would get one component working, but when we moved onto the next, five new problems would arise. It was a moving target.”
Flight muscles, for instance, don’t come prepackaged for robots the size of a fingertip.
“Large robots can run on electromagnetic motors, but at this small scale you have to come up with an alternative, and there wasn’t one,” says co-lead author Kevin Y Ma, a graduate student at SEAS.
The tiny robot flaps its wings with piezoelectric actuators—strips of ceramic that expand and contract when an electric field is applied.
Thin hinges of plastic embedded within the carbon fibre body frame serve as joints and a delicately balanced control system commands the rotational motions in the flapping-wing robot, with each wing controlled independently in real time.
At tiny scales, small changes in airflow can have an outsized effect on flight dynamics, and the control system has to react that much faster to remain stable.
The robotic insects also take advantage of an ingenious pop-up manufacturing technique that was developed by Wood’s team in 2011. Sheets of various laser-cut materials are layered and sandwiched together into a thin, flat plate that folds up like a child’s pop-up book into the complete electromechanical structure.
The quick, step-by-step process replaces what used to be a painstaking manual art and allows Wood’s team to use more robust materials in new combinations, while improving the overall precision of each device.
“We can now very rapidly build reliable prototypes, which allows us to be more aggressive in how we test them,” says Ma, adding that the team has gone through 20 prototypes in just the past six months.
Applications of the project
Applications of the RoboBee project could include distributed environmental monitoring, search-and-rescue operations, or assistance with crop pollination.
However, the materials, fabrication techniques and components that emerge along the way might prove to be even more significant.
(Continued next issue)
For more information, see Tree Fruit November 2013
