Safe landing thanks to snake legs

Spektrum der Wissenschaft

3.5.2025

Translation: machine translated

Tiny flying machines could one day pollinate flowers or search for missing persons. But until now, they have not been able to land safely. Researchers have now modelled them on the long legs of gnats.

It may be called RoboBee, or robot bee, but at first glance the mini drone has little to do with the black and yellow striped hymenoptera. The tiny, autonomously buzzing aircraft is more reminiscent of a snake. This is mainly due to the fact that the machine creature can already fly, dive and hover like a real insect - but it has so far struggled to land. The solution: long, articulated legs like those of snails or weavers, which make the transition from the air to the ground easier and allow it to touch down gently. This is now reported by a research team from the Harvard School of Engineering in the specialist journal «Science Robotics». Videos show that they have succeeded in having the artificial insect take off from a plant leaf and land there again.

In addition to the long legs, the robot has also been given an updated control system that helps it to slow down on approach. These improvements protect RoboBee's sensitive piezoelectric actuators, which can easily break during rough landings and collisions. «In the past, we had to switch it off just above the ground when landing, just drop it and pray that it would land upright and safely», says engineer and co-author Christian Chan in a press release. The landing was also problematic because the flying object is so small and light. It weighs just a tenth of a gram and has a wingspan of three centimetres. As it flaps its wings, the drone creates air vortices that rob it of its stability close to the ground.

To solve the problem, Christian Chan and his colleague Nakseung Hyun took inspiration from nature when redesigning the landing unit. They found suitable legs in the biological superfamily Tipuloidea. These include mosquitoes, wading midges and gnats. «The ratio of wingspan to body size of our RoboBee was already similar to that of the Tipuloidea», explains Chan. They found that the insects have long, articulated appendages, which probably give them the ability to cushion their landings. Using specimens from the Harvard Museum of Comparative Zoology database, the team created prototypes of different leg architectures and settled on a design that resembles the leg segmentation and joint arrangement of the Tipuloidea.

The diminutive size and insect-like flight capabilities of RoboBee, which has been in development since 2012 and is being continuously improved, offer fascinating possibilities for future applications, including environmental monitoring and disaster response. One of Chan's favourite applications, according to the press release, is artificial pollination. However, the idea that one day swarms of RoboBees will be buzzing around autonomously in gardens and over fields is perhaps something for science fiction films.

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