Unmanned aerial vehicles (UAVs), now also often referred to as drones, can either be controlled remotely or through prior programming, or they can fly autonomously. The market for UAVs has grown steadily in recent years, and as in many other areas, this trend is also accompanied by an increasing orientation towards models taken from nature.
In the current development, systems with dimensions in the lower decimeter range (Micro Aerial Vehicles, MAVs) dominate. Especially when it comes to the stability of these small systems in unfavorable wind conditions, but also when it comes to optimizing motion sequences, maneuverability, robustness, energy efficiency and noise reduction, an animal is often the inspiration for the development of the drones, then known as Biomimetic Micro Aerial Vehicles (BMAVs) .
The field of application of such bio-inspired UAVs is wide. Better, faster and more powerful drones are being developed not only for professional tasks such as delivering parcels, filming or monitoring difficult to access or dangerous areas, but also increasingly for private use. Birds, which are ideally prepared for the different conditions with specially adapted wing shapes, serve as models for such bio-inspired aircraft.
The developers are inspired by the shape of the wing, the flapping mechanism and the movement of the wing itself. In the case of drones, which are developed for use in agriculture, for example, in addition to their aerodynamic capabilities, the external appearance of the bird and the behavior of birds of prey are often simulated at the same time in order to keep predators such as seagulls, sparrows or other animals away from cultivation fields or fish farms, without having to use other processes that are harmful to the environment or animals. Toy drones are also becoming more and more similar to natural models. Bird- and dragonfly-like drones for private use, controlled by a smartphone, can fly quickly and with great agility, and from a distance it cannot be seen at first glance that it is not a real animal.
But the researchers don't just see birds as role models for missiles; insects, bats and “floating” fish such as rays also serve as inspiration in drone development. In addition to the flight of birds, the flight mechanisms of various insects, some of which have been very well researched, are now being implemented in a wide variety of models. Harvard University, for example, has developed a small missile and named it “RoboBee”. This tiny drone is only two centimeters tall and weighs just 100 milligrams. However, only the shape of the four wings is reminiscent of a bee. With these, the little robot can hit up to 170 times per second, which means that it is only slightly inferior to the natural model (200 times). Like real insects, the drone can stay in the air, dodge at lightning speed or perch on leaves. Work is now underway to ensure that RoboBee can move autonomously and without cables.
As a rule, such biomimetic missiles, like their natural counterparts, move at slow speeds. Problems with dealing with turbulence and gusts of wind occur more often, especially with small aircraft. Since small UAVs like to be used in cities or other areas with obstacles, this can lead to problems and damage. Another critical point with the small mini-drones is the operating time in which they can move in the air.
Usually the battery is empty after a relatively short time. Here, too, new bio-inspired solutions are constantly being developed, such as so-called separate flow blades, with which the mini-UAVs can fly more stable and longer than other devices of similar size and weight. The non-smooth shape of the front side of the wing, inspired by birds and insects, creates a detachment of the air flow, which would create efficiency problems in large aircraft, but in animals and also in mini-UAVs it provides more stability and higher efficiency. Other small adjustments to the wings can also have a great positive influence on the lift function after flight maneuvers.
Other special challenges of these unmanned aircraft are sufficient lift and propulsion, the control of autonomous flight ability and the management of complex flight maneuvers and gusts of wind. In nature you can find a mature interplay of aerodynamic shape, muscle activity and central neuronal control. In addition to the imitation of wings or individual special structures, the technical implementation has also been based on various control mechanisms from the (flying) animal kingdom for several years. Artificial neural networks or bio-inspired algorithms, for example, use the optomotor principle of insects for navigation models, enable autonomous landing of UAVs or, inspired by houseflies, improve the altitude control and evasive behavior of the drones. In addition to the installation of lightweight materials, material development also gives rise to other important impulses, for example artificial actuators made of ionic polymer-metal composite material, with which wing muscle-
can control similarly.
Despite all the advances, the specific performance data of the natural models are usually even better today than those of the corresponding technical implementations, but the current developments contribute to the fact that the market for biomimetic UAVs will continue to grow in the future.
Dr. Vanessa Hollmann