Autonomous flying in a swarm

As part of our Bionic Learning Network, we have been dealing with the fascination of flying for over 15 years. Since then, we have researched and technologically implemented numerous, additional flying objects and their natural principles, learning from the biological models. A major challenge here was autonomous swarm behavior. With the BionicBee, for the first time our team has now developed a flying object that can fly in large numbers and completely autonomously in a swarm.

Ultralight flying objects with intricate design

At about 34 grams, a length of 22 centimeters and a wingspan of 24 centimeters, the BionicBee is the smallest flying object of the Bionic Learning Network to date. For the first time, the developers used the methodology of generative design: after a few parameters have been entered, the software finds the optimum structure based on defined design principles in order to use as little material as necessary with the most stable construction possible. This consistent lightweight construction is of elementary importance for good maneuverability and flight duration.

Function integration in a small installation space

The bee’s body forms the compact housing for the beating wing mechanism, the communication technology as well as the control components for the wing beats and adaptation of the wing geometry. A brushless motor, three servo motors, the battery, the gear unit and various circuit boards are installed in the smallest of spaces. The intelligent interaction between the motors and the mechanical system makes it possible to precisely adjust the frequency of the flapping of the wings for the various maneuvers, for example.

Natural flight maneuvers with four degrees of freedom

The artificial bee flies with a stroke frequency of 15 to 20 hertz. In the process, the wings beat back and forth at a 180-degree angle. The brushless motor drives the wingbeat backlash-free via a precisely guided, ultra-lightweight, mechanical design. The higher the speed, the greater the stroke frequency and lift. The three servo motors at the wing root selectively change the geometry of the wing, thus increasing its effectiveness in certain wing positions and leading to a targeted variation of the lift generated.

If the bee is to fly forward, the geometry is adjusted so that the lift in the rear position of the wing is greater than in the forward position. This causes the body to tilt forward (pitch) and the bee goes into forward flight. If the geometry is set so that the right wing generates more lift than the left wing, the bee rolls (banks) about its longitudinal axis to the left and flies sideways. Another possibility is to adjust it in such a way that one wing generates more lift at the front and the second wing generates more lift at the rear. This causes the bee to rotate (yaw) about its vertical axis.

Autonomous flying in a swarm

The autonomous behavior of the ten bees succeeds with the help of an indoor localization system with ultra-wideband technology (UWB). For this purpose, eight UWB anchors are installed on two levels in the room. This allows accurate run time measurement and enables the bees to locate themselves in the room. The UWB anchors send signals to the individual bees, which independently measure their distances from the respective transmitting elements, so they can calculate their own position in space based on the time stamps.

In order to fly in a swarm, the bees follow the paths specified by a central computer. High spatial and temporal accuracy is required for safe and collision-free flight in close formation. Possible mutual interaction due to air turbulence ("down-wash") must also be taken into account when planning the flight path.

As each bee is built by hand and even the smallest manufacturing differences can influence the flight characteristics, the bees also have an automatic calibration function: after a short test flight, each bee determines its individually optimized controller parameters. In this way, the intelligent algorithm can work out the hardware differences between the individual bees, allowing the entire swarm to be controlled from the outside as if all the bees were identical.

The BionicBee makes use of numerous insights gained by our developers in previous projects. It thus joins a series of bionic flying objects that have been created as part of our Bionic Learning Network. For over 15 years, we have been designing research test beds with basic technical principles derived from nature. You will get a small insight on the following pages.