Engineers at the Massachusetts Institute of Technology (MIT) and the Swiss Federal Institute of Technology Lausanne (EPFL) have developed a lightweight robotic vehicle capable of swimming underwater before transitioning directly into flight, drawing inspiration from diving birds such as puffins, gulls, loons, and petrels. The research, which has been peer reviewed, is scheduled for publication in the journal Science.
The flapping-wing aerial-aquatic vehicle (FAAV) weighs less than 300 grams and is designed to investigate how diving birds move efficiently through both air and water despite the two environments having substantially different physical properties. The robot consists of a central fuselage, two flexible flapping wings, and a motorized tail whose angle can be adjusted. Its wings and tail can also be exchanged for components of different sizes to evaluate flight performance under varying conditions.
The research team conducted experiments in a water tank and in Lake Geneva, testing combinations of wing size, flapping frequency, and tail angle to determine the conditions that allow the robot to swim underwater, break through the water’s surface, and continue flying. The experiments found that medium-sized wings provided the most reliable performance across swimming, takeoff, and flight. Wing flexibility also proved important, with the wings needing to reduce flapping amplitude in water while maintaining sufficient rigidity for flight.
According to the researchers, the robot was able to swim at speeds approaching one metre per second while flapping its wings at approximately five hertz and could fly at roughly six metres per second using a similar flapping frequency. These operating characteristics are comparable to those observed in several species of diving birds.
The team also found that the robot achieved successful water-to-air transitions when pitched at an angle of about 70 degrees, which prevented the wing tips from striking the water during takeoff. Unlike many diving birds, however, the robotic system did not require a paddling motion with feet to launch from the water’s surface.
Raphael Zufferey, assistant professor of mechanical engineering at MIT and lead author of the study, said the project aims to support future oceanographic research by providing a platform capable of repeatedly flying to remote locations, collecting measurements or samples underwater, and returning with the data. He added that the long-term objective is to enable more frequent and geographically distributed environmental observations than are practical with conventional research vessels.
The researchers plan to refine the vehicle by developing wings capable of rotational movement in addition to flapping and by evaluating the robot’s performance in more demanding conditions, including rough water and windy environments. They also intend to explore applications in ocean science that require repeated aerial and underwater data collection.
