17-04-2025
RoboBee outfitted with reliable landing gear enables safe touchdowns for tiny robots
Nature has perfected the art of landing. From delicate flies to buzzing bees, insects navigate complex aerial maneuvers and touchdown with high precision.
But for human-made flying robots, especially those at the insect scale, landing safely has been a significant challenge.
Drawing inspiration from insects, researchers at Harvard University have engineered a landing gear and control strategy that allows miniature flying robots to achieve safe landings on different types of surfaces.
It was applied to Harvard's RoboBee – a tiny flapping-wing robot.
'RoboBee is an excellent platform to explore the interface of biology and robotics,' said Alyssa Hernandez, co-author.
'Seeking bioinspiration within the amazing diversity of insects offers us countless avenues to continue improving the robot. Reciprocally, we can use these robotic platforms as tools for biological research, producing studies that test biomechanical hypotheses,' Hernandez said.
The team studied the long, jointed legs of the crane fly, an insect known for its slow, deliberate movements. These legs appear perfectly designed to absorb impact and ensure a gentle touchdown.
Inspired by this natural design, the engineers outfitted the RoboBee with its own set of long, double-jointed legs. These new appendages are designed to cushion the impact as the robot transitions from air to ground, protecting its delicate components.
The Harvard team has continuously improved the RoboBee's insect-like flight. It can fly, dive, and hover.
But this robot is a bit delicate as it weighs only a tenth of a gram and has a wingspan of a mere three centimeters.
Due to its small size, the RoboBee is significantly affected by the "ground effect.' It is the turbulent air generated by its flapping wings near a surface, similar to a helicopter's downdraft.
Christian Chan, a graduate student and co-first author on the paper, spearheaded the mechanical redesign.
He explains that these legs are crucial for safeguarding the RoboBee's fragile piezoelectric actuators – the powerful "muscles" that enable flight but are easily damaged by rough landings.
'The successful landing of any flying vehicle relies on minimizing the velocity as it approaches the surface before impact and dissipating energy quickly after the impact,' said Nak-seung Patrick Hyun, the co-first author, now an assistant professor at Purdue University.
'Even with the tiny wing flaps of RoboBee, the ground effect is non-negligible when flying close to the surface, and things can get worse after the impact as it bounces and tumbles,' Hyun explained.
But the new legs are only half the story. The RoboBee has also received a software update – an improved controller, or "brain," that helps it adapt to the troublesome ground effect.
The updated controller enables the robot to slow down upon approach, resulting in a gentle landing instead of a hard crash.
The team successfully tested these controlled landings on both rigid surfaces and even delicate leaves.
While currently tethered for power and control, the team's long-term goal is full autonomy for the RoboBee.
The RoboBee's safe landing capability creates exciting prospects for future uses.
For instance, it could be used in monitoring the environment and surveying disaster zones. Moreover, Chan is particularly enthusiastic about the potential for artificial pollination, envisioning swarms of RoboBees assisting in vertical farms and future gardens.
The findings were published in the journal Science Robotics.
