Switches medium quickly and can hitchhike: Scientists have developed a drone that can navigate both in water and in the air and is equipped with a sophisticated ‘thrusting device’. Tests show that its suction disc, inspired by the Remora fish, allows it to stably attach to surfaces in water and on land. For example, a drone can also save energy when traveling on ship hulls or whale bellies. According to the researchers, the concept is particularly suitable for the biological and ecological monitoring of marine ecosystems.
They fly through the air in increasingly sophisticated versions, and scientists have already developed many autonomous robotic systems for use in water. However, the goal of a team of scientists from China, UK and Switzerland is now to create powerful combinations of these concepts. As the ability to flexibly switch between media, air and water can open up some interesting application possibilities, especially in environmental exploration.
In addition to optimizing the drivetrain, an important aspect in the development of the current team model was the expansion of the range without relying on battery systems. Giving drones more freedom from base stations could increase their potential for research missions over large or remote areas. Scientists are now presenting a prototype of a hybrid drone that is suitable for both air and water operation and that can reduce its energy requirements thanks to ‘hitchhiking’.
Improved propellers and biomimetic grip
The basic concept is based on the design of conventional quadrocopter drones with four propulsion units. A special adjustment of the change between water and air is the clever design of the rotors: when driven in a liquid medium, the blades of these units take an angled position via a flexible joint to form a more propeller shape. However, as soon as they reach the surface, they stretch under the action of the increased speed and the associated centrifugal forces, thus creating a propeller shape. This passive transformational power propels the drone optimally in both media, and the change can happen surprisingly quickly: scientists report that a changing propeller crosses the air-water barrier in 0.35 seconds.
Scientists were inspired by nature when designing the adhesive component of a hybrid drone. They studied in detail the organ by which the fish remora (Echeneis naucrates) attaches to marine animals in order to be carried away by them. It is a disk consisting of various chambers. They form a set of suction cups that use negative pressure to provide adjustable traction. The compartments ensure that the connection can also be retained on surfaces with a complex structure. Remora fish even stick to the skin without any problems when dolphins and others jump out of the water.
Hitchhiking on the way
The new adhesive that scientists have developed is now based on the same basic concept as the fish model. The flexible polymeric material creates compartments that provide a negative pressure as soon as the element comes into contact with the surfaces due to shape changes generated by the hydraulic systems. This enables a strong adhesion, which can easily be released again by means of the device driver if necessary. The developers’ prototype has one such fastener on the top and one on the bottom of the CPU. Concept tests have confirmed that the self-adhesive disc can securely attach the robot not only to wet but also dry surfaces with different textures.
The practical potential of the concept was also confirmed in application related tests: scientists docked the hybrid drone on the hull of the watercraft so that it could be taken with them. This resulted in video recordings of the seabed, such as hermit crabs, scallops and seaweed. The hitchhiker himself used almost no energy. During testing, the team was also able to document that the robot can perform a variety of tasks in both fresh and salt water.
“We have successfully technically implemented a cavity adhesion mechanism and combined it with robotic systems to achieve novel mobility methods in robotics,” says co-author Mirko Kovac of the Swiss Federal Laboratories for Materials Science and Technology in Dübendorf, summarizing the result. from work. Collectively, the researchers write: ‘We believe that our results now pave the way for the development of autonomous robots with different functions in a variety of air and water environments.’
Source: Swiss Federal Laboratories for Materials Testing and Research, article: Science Robotics, doi: 10.1126 / scirobotics.abm6695
Video © Empa (source: Beihang University / Science Robotics)