Festo 's Bionic Learning Network has been exploring the fascination of flight for more than 15 years. In addition to the technical decoding of bird flight, the team has researched and technologically implemented numerous other flying objects and their natural principles. The BionicBee is now available. With a weight of around 34 g, a length of 220 mm and a wingspan of 240 mm, it is the Bionic Learning Network's smallest flying object to date.

For the first time, the developers used the method of generative design: after entering a few parameters, 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 essential for good maneuverability and flight duration.

The compact construction for the flapping wing mechanism, the communication technology and the control components for flapping and adapting the wing geometry are located in the bee's body. A brushless motor, three servomotors, the battery, the gearbox and various circuit boards are installed in a very small space. The intelligent interaction of motors and mechanics allows, for example, the frequency of the wing beat to be precisely adjusted for the various maneuvers.

Natural flight maneuvers with four degrees of freedom

The artificial bee flies with a flapping frequency of 15 to 20 hearts. The wings beat back and forth at a 180° angle. The brushless motor drives the flapping of the wings backlash-free via a precisely guided, ultra-light mechanical construction. The higher the speed, the higher the flapping frequency and the lift. The three servomotors at the wing root change the geometry of the wing in a targeted manner, thus increasing the effectiveness in certain wing positions and leading to a targeted variation of the lift generated.

If the bee is to fly forwards, the geometry is adjusted so that the lift is greater in the rear position of the wing than in the front position. This causes the body to tilt forward (pitch) and the bee to fly forwards. If the geometry is set so that the right wing generates more lift than the left wing, the bee rolls around the longitudinal axis to the left and flies off to the side. Another option is to adjust the geometry so that one wing generates more lift at the front and the second wing generates more lift at the rear. This causes the bee to turn (yaw) around its vertical axis.

Safe and collision-free flying

The autonomous behaviour of the swarm of bees is achieved 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 makes it possible to precisely measure the time of flight and the bees can localize themselves in the room. The UWB anchors send signals to the individual bees, which independently measure the distances to the respective transmitting elements and can calculate their own position in the room using the time stamps.

To fly in a swarm, the bees follow the paths specified by a central computer. A high degree of spatial and temporal accuracy is required for safe and collision-free flight in close formation. When planning the path, possible mutual interaction due to air turbulence ('down-wash') must also be taken into account.

As each bee is built by hand and even the smallest manufacturing differences can influence the flight behaviour, 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.