Soft landing for RoboBee

The team led by Robert Wood at the John A. Paulson School of Engineering and Applied Sciences (SEAS), has equipped the RoboBee flying robot with long, articulated legs to help it transition from the air to the ground. The robot has also been given an improved control system that helps it to slow down on approach, resulting in a soft touchdown. The improvements protect the sensitive electronics, which can easily be damaged by external forces during rough landings and collisions.

Previously, landing was critical for RoboBee because the robot weighs only a tenth of a gram and has a wingspan of three centimeters. Previous versions suffered from instability due to the air turbulence caused by the flapping wings - similar to the gusts of wind generated by helicopter rotors hitting the ground with full force.

“In the past, when we wanted to land, we would shut down the vehicle just above the ground, simply drop it and pray that it would touch down safely,” explains Christian Chan, who led the mechanical redesign of the robot.

The successful landing of any flying object depends on minimizing its speed as it approaches the surface and rapidly dissipating its energy after touchdown. Image: Harvard Microrobotics Laboratory

“The successful landing of any flying object depends on minimizing its speed as it approaches the surface and rapidly dissipating its energy after touchdown,” says Nak-seung Patrick Hyun, assistant professor at Purdue University. “Even with RoboBee's tiny wings, the ground effect is not negligible when it flies close to the surface. After impact, it can get even worse if it bounces or tumbles.”

The engineers drew inspiration from nature to develop improvements for stable flight and a graceful landing on different surfaces. They focused on the crane fly, a slow-flying insect that is often mistaken for a giant mosquito. “The size and scaling of the wingspan and body size of our flying machine is similar to the crane fly,” says Chan.

The researchers discovered that the crane fly has long, articulated appendages that give the insects the ability to cushion their landing. Crane flies are also characterized by their short flights. They spend a large part of their short adult lives landing and taking off.

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 crane fly's leg segmentation and joint arrangement.

RoboBee's tiny size and insect-like flight capabilities offer intriguing possibilities for applications including environmental monitoring and disaster response. Photo: Eliza Grinnell / Harvard SEAS Communications

“RoboBee is an excellent development for exploring the interface between biology and robotics,” says Alyssa Hernandez, who studies insect locomotion at Harvard's Department of Organismic and Evolutionary Biology. “Drawing inspiration from the amazing diversity of insects provides us with countless opportunities to further improve the robot. Conversely, we can use these robotic platforms as tools for biological research and create studies that test biomechanical hypotheses,” she continues.

The goal is for RoboBee to be fully autonomous, RoboBee's tiny size and insect-like flight capabilities offer fascinating possibilities for applications including environmental monitoring and disaster prevention. One of Chan's favorite applications is artificial pollination - imagine swarms of RoboBees buzzing around vertical farms and gardens of the future.

Original publication:

Nak-seung P. Hyun, Christian M. Chan, Alyssa M. Hernandez and Robert J. Wood

Sticking the landing: Insect-inspired strategies for safely landing flapping-wing aerial microrobots

Science Robotics, 16 Apr 2025, Vol 10, Issue 101

DOI: 10.1126/scirobotics.adq30